[Title 40 CFR ]
[Code of Federal Regulations (annual edition) - July 1, 2018 Edition]
[From the U.S. Government Publishing Office]
[[Page i]]
Title 40
Protection of Environment
________________________
Parts 50 to 51
Revised as of July 1, 2018
Containing a codification of documents of general
applicability and future effect
As of July 1, 2018
Published by the Office of the Federal Register
National Archives and Records Administration as a
Special Edition of the Federal Register
[[Page ii]]
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[[Page iii]]
Table of Contents
Page
Explanation................................................. v
Title 40:
Chapter I--Environmental Protection Agency
(Continued) 3
Finding Aids:
Table of CFR Titles and Chapters........................ 683
Alphabetical List of Agencies Appearing in the CFR...... 703
List of CFR Sections Affected........................... 713
[[Page iv]]
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Cite this Code: CFR
To cite the regulations in
this volume use title,
part and section number.
Thus, 40 CFR 50.1 refers
to title 40, part 50,
section 1.
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[[Page v]]
EXPLANATION
The Code of Federal Regulations is a codification of the general and
permanent rules published in the Federal Register by the Executive
departments and agencies of the Federal Government. The Code is divided
into 50 titles which represent broad areas subject to Federal
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name of the issuing agency. Each chapter is further subdivided into
parts covering specific regulatory areas.
Each volume of the Code is revised at least once each calendar year
and issued on a quarterly basis approximately as follows:
Title 1 through Title 16.................................as of January 1
Title 17 through Title 27..................................as of April 1
Title 28 through Title 41...................................as of July 1
Title 42 through Title 50................................as of October 1
The appropriate revision date is printed on the cover of each
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LEGAL STATUS
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HOW TO USE THE CODE OF FEDERAL REGULATIONS
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OMB CONTROL NUMBERS
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collection request.
[[Page vi]]
Many agencies have begun publishing numerous OMB control numbers as
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(b) The matter incorporated is in fact available to the extent
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(c) The incorporating document is drafted and submitted for
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this volume.
[[Page vii]]
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Oliver A. Potts,
Director,
Office of the Federal Register
July 1, 2018
[[Page ix]]
THIS TITLE
Title 40--Protection of Environment is composed of thirty-seven
volumes. The parts in these volumes are arranged in the following order:
Parts 1-49, parts 50-51, part 52 (52.01-52.1018), part 52 (52.1019-
52.2019), part 52 (52.2020-end of part 52), parts 53-59, part 60 (60.1-
60.499), part 60 (60.500-end of part 60, sections), part 60
(Appendices), parts 61-62, part 63 (63.1-63.599), part 63 (63.600-
63.1199), part 63 (63.1200-63.1439), part 63 (63.1440-63.6175), part 63
(63.6580-63.8830), part 63 (63.8980-end of part 63), parts 64-71, parts
72-79, part 80, part 81, parts 82-86, parts 87-95, parts 96-99, parts
100-135, parts 136-149, parts 150-189, parts 190-259, parts 260-265,
parts 266-299, parts 300-399, parts 400-424, parts 425-699, parts 700-
722, parts 723-789, parts 790-999, parts 1000-1059, and part 1060 to
end. The contents of these volumes represent all current regulations
codified under this title of the CFR as of July 1, 2018.
Chapter I--Environmental Protection Agency appears in all thirty-
seven volumes. Regulations issued by the Council on Environmental
Quality, including an Index to Parts 1500 through 1508, appear in the
volume containing parts 1060 to end. The OMB control numbers for title
40 appear in Sec. 9.1 of this chapter.
For this volume, Michele Bugenhagen was Chief Editor. The Code of
Federal Regulations publication program is under the direction of John
Hyrum Martinez, assisted by Stephen J. Frattini.
[[Page 1]]
TITLE 40--PROTECTION OF ENVIRONMENT
(This book contains parts 50 to 51)
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Part
chapter i--Environmental Protection Agency (Continued)...... 50
[[Page 3]]
CHAPTER I--ENVIRONMENTAL PROTECTION AGENCY (CONTINUED)
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SUBCHAPTER C--AIR PROGRAMS
Part Page
50 National primary and secondary ambient air
quality standards....................... 5
51 Requirements for preparation, adoption, and
submittal of implementation plans....... 169
[[Page 5]]
SUBCHAPTER C_AIR PROGRAMS
PART 50_NATIONAL PRIMARY AND SECONDARY AMBIENT AIR QUALITY STANDARDS
--Table of Contents
Sec.
50.1 Definitions.
50.2 Scope.
50.3 Reference conditions.
50.4 National primary ambient air quality standards for sulfur oxides
(sulfur dioxide).
50.5 National secondary ambient air quality standard for sulfur oxides
(sulfur dioxide).
50.6 National primary and secondary ambient air quality standards for
PM10.
50.7 National primary and secondary ambient air quality standards for
PM2.5.
50.8 National primary ambient air quality standards for carbon monoxide.
50.9 National 1-hour primary and secondary ambient air quality standards
for ozone.
50.10 National 8-hour primary and secondary ambient air quality
standards for ozone.
50.11 National primary and secondary ambient air quality standards for
oxides of nitrogen (with nitrogen dioxide as the indicator).
50.12 National primary and secondary ambient air quality standards for
lead.
50.13 National primary and secondary ambient air quality standards for
PM2.5.
50.14 Treatment of air quality monitoring data influenced by exceptional
events.
50.15 National primary and secondary ambient air quality standards for
ozone.
50.16 National primary and secondary ambient air quality standards for
lead.
50.17 National primary ambient air quality standards for sulfur oxides
(sulfur dioxide).
50.18 National primary ambient air quality standards for
PM2.5.
50.19 National primary and secondary ambient air quality standards for
ozone.
Appendix A-1 to Part 50--Reference Measurement Principle and Calibration
Procedure for the Measurement of Sulfur Dioxide in the
Atmosphere (Ultraviolet Fluorescence Method)
Appendix A-2 to Part 50--Reference Method for the Determination of
Sulfur Dioxide in the Atmosphere (Pararosaniline Method)
Appendix B to Part 50--Reference Method for the Determination of
Suspended Particulate Matter in the Atmosphere (High-Volume
Method)
Appendix C to Part 50--Measurement Principle and Calibration Procedure
for the Measurement of Carbon Monoxide in the Atmosphere (Non-
Dispersive Infrared Photometry)
Appendix D to Part 50--Reference Measurement Principle and Calibration
Procedure for the Measurement of Ozone in the Atmosphere
(Chemiluminescence Method)
Appendix E to Part 50 [Reserved]
Appendix F to Part 50--Measurement Principle and Calibration Procedure
for the Measurement of Nitrogen Dioxide in the Atmosphere (Gas
Phase Chemiluminescence)
Appendix G to Part 50--Reference Method for the Determination of Lead in
Total Suspended Particulate Matter
Appendix H to Part 50--Interpretation of the 1-Hour Primary and
Secondary National Ambient Air Quality Standards for Ozone
Appendix I to Part 50--Interpretation of the 8-Hour Primary and
Secondary National Ambient Air Quality Standards for Ozone
Appendix J to Part 50--Reference Method for the Determination of
Particulate Matter as PM10 in the Atmosphere
Appendix K to Part 50--Interpretation of the National Ambient Air
Quality Standards for Particulate Matter
Appendix L to Part 50--Reference Method for the Determination of Fine
Particulate Matter as PM2.5 in the Atmosphere
Appendix M to Part 50 [Reserved]
Appendix N to Part 50--Interpretation of the National Ambient Air
Quality Standards for PM2.5
Appendix O to Part 50--Reference Method for the Determination of Coarse
Particulate Matter as PM10-2.5 in the Atmosphere
Appendix P to Part 50--Interpretation of the Primary and Secondary
National Ambient Air Quality Standards for Ozone
Appendix Q to Part 50--Reference Method for the Determination of Lead in
Particulate Matter as PM10 Collected From Ambient
Air
Appendix R to Part 50--Interpretation of the National Ambient Air
Quality Standards for Lead
Appendix S to Part 50--Interpretation of the Primary National Ambient
Air Quality Standards for Oxides of Nitrogen (Nitrogen
Dioxide)
Appendix T to Part 50--Interpretation of the Primary National Ambient
Air Quality Standards for Oxides of Sulfur (Sulfur Dioxide)
Appendix U to Pt. 50--Interpretation of the Primary and Secondary
National
[[Page 6]]
Ambient Air Quality Standards for Ozone
Authority: 42 U.S.C. 7401, et seq.
Source: 36 FR 22384, Nov. 25, 1971, unless otherwise noted.
Sec. 50.1 Definitions.
(a) As used in this part, all terms not defined herein shall have
the meaning given them by the Act.
(b) Act means the Clean Air Act, as amended (42 U.S.C. 1857-18571,
as amended by Pub. L. 91-604).
(c) Agency means the Environmental Protection Agency.
(d) Administrator means the Administrator of the Environmental
Protection Agency.
(e) Ambient air means that portion of the atmosphere, external to
buildings, to which the general public has access.
(f) Reference method means a method of sampling and analyzing the
ambient air for an air pollutant that is specified as a reference method
in an appendix to this part, or a method that has been designated as a
reference method in accordance with part 53 of this chapter; it does not
include a method for which a reference method designation has been
cancelled in accordance with Sec. 53.11 or Sec. 53.16 of this chapter.
(g) Equivalent method means a method of sampling and analyzing the
ambient air for an air pollutant that has been designated as an
equivalent method in accordance with part 53 of this chapter; it does
not include a method for which an equivalent method designation has been
cancelled in accordance with Sec. 53.11 or Sec. 53.16 of this chapter.
(h) Traceable means that a local standard has been compared and
certified either directly or via not more than one intermediate
standard, to a primary standard such as a National Bureau of Standards
Standard Reference Material (NBS SRM), or a USEPA/NBS-approved Certified
Reference Material (CRM).
(i) Indian country is as defined in 18 U.S.C. 1151.
(j) Exceptional event means an event(s) and its resulting emissions
that affect air quality in such a way that there exists a clear causal
relationship between the specific event(s) and the monitored
exceedance(s) or violation(s), is not reasonably controllable or
preventable, is an event(s) caused by human activity that is unlikely to
recur at a particular location or a natural event(s), and is determined
by the Administrator in accordance with 40 CFR 50.14 to be an
exceptional event. It does not include air pollution relating to source
noncompliance. Stagnation of air masses and meteorological inversions do
not directly cause pollutant emissions and are not exceptional events.
Meteorological events involving high temperatures or lack of
precipitation (i.e., severe, extreme or exceptional drought) also do not
directly cause pollutant emissions and are not considered exceptional
events. However, conditions involving high temperatures or lack of
precipitation may promote occurrences of particular types of exceptional
events, such as wildfires or high wind events, which do directly cause
emissions.
(k) Natural event means an event and its resulting emissions, which
may recur at the same location, in which human activity plays little or
no direct causal role. For purposes of the definition of a natural
event, anthropogenic sources that are reasonably controlled shall be
considered to not play a direct role in causing emissions.
(l) Exceedance with respect to a national ambient air quality
standard means one occurrence of a measured or modeled concentration
that exceeds the specified concentration level of such standard for the
averaging period specified by the standard.
(m) Prescribed fire is any fire intentionally ignited by management
actions in accordance with applicable laws, policies, and regulations to
meet specific land or resource management objectives.
(n) Wildfire is any fire started by an unplanned ignition caused by
lightning; volcanoes; other acts of nature; unauthorized activity; or
accidental, human-caused actions, or a prescribed fire that has
developed into a wildfire. A wildfire that predominantly occurs on
wildland is a natural event.
(o) Wildland means an area in which human activity and development
are essentially non-existent, except for roads, railroads, power lines,
and similar transportation facilities. Structures, if any, are widely
scattered.
[[Page 7]]
(p) High wind dust event is an event that includes the high-speed
wind and the dust that the wind entrains and transports to a monitoring
site.
(q) High wind threshold is the minimum wind speed capable of causing
particulate matter emissions from natural undisturbed lands in the area
affected by a high wind dust event.
(r) Federal land manager means, consistent with the definition in 40
CFR 51.301, the Secretary of the department with authority over the
Federal Class I area (or the Secretary's designee) or, with respect to
Roosevelt-Campobello International Park, the Chairman of the Roosevelt-
Campobello International Park Commission.
[36 FR 22384, Nov. 25, 1971, as amended at 41 FR 11253, Mar. 17, 1976;
48 FR 2529, Jan. 20, 1983; 63 FR 7274, Feb. 12, 1998; 72 FR 13580, Mar.
22, 2007; 81 FR 68276, Oct. 3, 2016]
Sec. 50.2 Scope.
(a) National primary and secondary ambient air quality standards
under section 109 of the Act are set forth in this part.
(b) National primary ambient air quality standards define levels of
air quality which the Administrator judges are necessary, with an
adequate margin of safety, to protect the public health. National
secondary ambient air quality standards define levels of air quality
which the Administrator judges necessary to protect the public welfare
from any known or anticipated adverse effects of a pollutant. Such
standards are subject to revision, and additional primary and secondary
standards may be promulgated as the Administrator deems necessary to
protect the public health and welfare.
(c) The promulgation of national primary and secondary ambient air
quality standards shall not be considered in any manner to allow
significant deterioration of existing air quality in any portion of any
State or Indian country.
(d) The proposal, promulgation, or revision of national primary and
secondary ambient air quality standards shall not prohibit any State or
Indian country from establishing ambient air quality standards for that
State or area under a tribal CAA program or any portion thereof which
are more stringent than the national standards.
[36 FR 22384, Nov. 25, 1971, as amended at 63 FR 7274, Feb. 12, 1998]
Sec. 50.3 Reference conditions.
All measurements of air quality that are expressed as mass per unit
volume (e.g., micrograms per cubic meter) other than for particulate
matter (PM2.5) standards contained in Sec. Sec. 50.7, 50.13,
and 50.18, and lead standards contained in Sec. 50.16 shall be
corrected to a reference temperature of 25 (deg) C and a reference
pressure of 760 millimeters of mercury (1,013.2 millibars). Measurements
of PM2.5 for purposes of comparison to the standards
contained in Sec. Sec. 50.7, 50.13, and 50.18, and of lead for purposes
of comparison to the standards contained in Sec. 50.16 shall be
reported based on actual ambient air volume measured at the actual
ambient temperature and pressure at the monitoring site during the
measurement period.
[78 FR 3277, Jan. 15, 2013]
Sec. 50.4 National primary ambient air quality standards for sulfur
oxides (sulfur dioxide).
(a) The level of the annual standard is 0.030 parts per million
(ppm), not to be exceeded in a calendar year. The annual arithmetic mean
shall be rounded to three decimal places (fractional parts equal to or
greater than 0.0005 ppm shall be rounded up).
(b) The level of the 24-hour standard is 0.14 parts per million
(ppm), not to be exceeded more than once per calendar year. The 24-hour
averages shall be determined from successive nonoverlapping 24-hour
blocks starting at midnight each calendar day and shall be rounded to
two decimal places (fractional parts equal to or greater than 0.005 ppm
shall be rounded up).
(c) Sulfur oxides shall be measured in the ambient air as sulfur
dioxide by the reference method described in appendix A to this part or
by an equivalent method designated in accordance with part 53 of this
chapter.
(d) To demonstrate attainment, the annual arithmetic mean and the
second-highest 24-hour averages must be based upon hourly data that are
at
[[Page 8]]
least 75 percent complete in each calendar quarter. A 24-hour block
average shall be considered valid if at least 75 percent of the hourly
averages for the 24-hour period are available. In the event that only
18, 19, 20, 21, 22, or 23 hourly averages are available, the 24-hour
block average shall be computed as the sum of the available hourly
averages using 18, 19, etc. as the divisor. If fewer than 18 hourly
averages are available, but the 24-hour average would exceed the level
of the standard when zeros are substituted for the missing values,
subject to the rounding rule of paragraph (b) of this section, then this
shall be considered a valid 24-hour average. In this case, the 24-hour
block average shall be computed as the sum of the available hourly
averages divided by 24.
(e) The standards set forth in this section will remain applicable
to all areas notwithstanding the promulgation of SO2 national
ambient air quality standards (NAAQS) in Sec. 50.17. The SO2
NAAQS set forth in this section will no longer apply to an area one year
after the effective date of the designation of that area, pursuant to
section 107 of the Clean Air Act, for the SO2 NAAQS set forth
in Sec. 50.17; except that for areas designated nonattainment for the
SO2 NAAQS set forth in this section as of the effective date
of Sec. 50.17, and areas not meeting the requirements of a SIP call
with respect to requirements for the SO2 NAAQS set forth in
this section, the SO2 NAAQS set forth in this section will
apply until that area submits, pursuant to section 191 of the Clean Air
Act, and EPA approves, an implementation plan providing for attainment
of the SO2 NAAQS set forth in Sec. 50.17.
[61 FR 25579, May 22, 1996, as amended at 75 FR 35592, June 22, 2010]
Sec. 50.5 National secondary ambient air quality standard for sulfur
oxides (sulfur dioxide).
(a) The level of the 3-hour standard is 0.5 parts per million (ppm),
not to be exceeded more than once per calendar year. The 3-hour averages
shall be determined from successive nonoverlapping 3-hour blocks
starting at midnight each calendar day and shall be rounded to 1 decimal
place (fractional parts equal to or greater than 0.05 ppm shall be
rounded up).
(b) Sulfur oxides shall be measured in the ambient air as sulfur
dioxide by the reference method described in appendix A of this part or
by an equivalent method designated in accordance with part 53 of this
chapter.
(c) To demonstrate attainment, the second-highest 3-hour average
must be based upon hourly data that are at least 75 percent complete in
each calendar quarter. A 3-hour block average shall be considered valid
only if all three hourly averages for the 3-hour period are available.
If only one or two hourly averages are available, but the 3-hour average
would exceed the level of the standard when zeros are substituted for
the missing values, subject to the rounding rule of paragraph (a) of
this section, then this shall be considered a valid 3-hour average. In
all cases, the 3-hour block average shall be computed as the sum of the
hourly averages divided by 3.
[61 FR 25580, May 22, 1996]
Sec. 50.6 National primary and secondary ambient air quality standards
for PM [bdi1][bdi0].
(a) The level of the national primary and secondary 24-hour ambient
air quality standards for particulate matter is 150 micrograms per cubic
meter ([micro]g/m\3\), 24-hour average concentration. The standards are
attained when the expected number of days per calendar year with a 24-
hour average concentration above 150 [micro]g/m\3\, as determined in
accordance with appendix K to this part, is equal to or less than one.
(b) [Reserved]
(c) For the purpose of determining attainment of the primary and
secondary standards, particulate matter shall be measured in the ambient
air as PM10 (particles with an aerodynamic diameter less than
or equal to a nominal 10 micrometers) by:
(1) A reference method based on appendix J and designated in
accordance with part 53 of this chapter, or
(2) An equivalent method designated in accordance with part 53 of
this chapter.
[52 FR 24663, July 1, 1987, as amended at 62 FR 38711, July 18, 1997; 65
FR 80779, Dec. 22, 2000; 71 FR 61224, Oct. 17, 2006]
[[Page 9]]
Sec. 50.7 National primary and secondary ambient air quality standards
for PM2.5.
(a) The national primary and secondary ambient air quality standards
for particulate matter are 15.0 micrograms per cubic meter ([micro]g/
m\3\) annual arithmetic mean concentration, and 65 [micro]g/m\3\ 24-hour
average concentration measured in the ambient air as PM2.5
(particles with an aerodynamic diameter less than or equal to a nominal
2.5 micrometers) by either:
(1) A reference method based on appendix L of this part and
designated in accordance with part 53 of this chapter; or
(2) An equivalent method designated in accordance with part 53 of
this chapter.
(b) The annual primary and secondary PM2.5 standards are
met when the annual arithmetic mean concentration, as determined in
accordance with appendix N of this part, is less than or equal to 15.0
micrograms per cubic meter.
(c) The 24-hour primary and secondary PM2.5 standards are
met when the 98\th\ percentile 24-hour concentration, as determined in
accordance with appendix N of this part, is less than or equal to 65
micrograms per cubic meter.
[62 FR 38711, July 18, 1997, as amended at 69 FR 45595, July 30, 2004]
Sec. 50.8 National primary ambient air quality standards for carbon
monoxide.
(a) The national primary ambient air quality standards for carbon
monoxide are:
(1) 9 parts per million (10 milligrams per cubic meter) for an 8-
hour average concentration not to be exceeded more than once per year
and
(2) 35 parts per million (40 milligrams per cubic meter) for a 1-
hour average concentration not to be exceeded more than once per year.
(b) The levels of carbon monoxide in the ambient air shall be
measured by:
(1) A reference method based on appendix C and designated in
accordance with part 53 of this chapter, or
(2) An equivalent method designated in accordance with part 53 of
this chapter.
(c) An 8-hour average shall be considered valid if at least 75
percent of the hourly average for the 8-hour period are available. In
the event that only six (or seven) hourly averages are available, the 8-
hour average shall be computed on the basis of the hours available using
six (or seven) as the divisor.
(d) When summarizing data for comparision with the standards,
averages shall be stated to one decimal place. Comparison of the data
with the levels of the standards in parts per million shall be made in
terms of integers with fractional parts of 0.5 or greater rounding up.
[50 FR 37501, Sept. 13, 1985]
Sec. 50.9 National 1-hour primary and secondary ambient air quality
standards for ozone.
(a) The level of the national 1-hour primary and secondary ambient
air quality standards for ozone measured by a reference method based on
appendix D to this part and designated in accordance with part 53 of
this chapter, is 0.12 parts per million (235 [micro]g/m\3\). The
standard is attained when the expected number of days per calendar year
with maximum hourly average concentrations above 0.12 parts per million
(235 [micro]g/m\3\) is equal to or less than 1, as determined by
appendix H to this part.
(b) The 1-hour standards set forth in this section will remain
applicable to all areas notwithstanding the promulgation of 8-hour ozone
standards under Sec. 50.10. The 1-hour NAAQS set forth in paragraph (a)
of this section will no longer apply to an area one year after the
effective date of the designation of that area for the 8-hour ozone
NAAQS pursuant to section 107 of the Clean Air Act. Area designations
and classifications with respect to the 1-hour standards are codified in
40 CFR part 81.
[62 FR 38894, July 18, 1997, as amended at 65 FR 45200, July 20, 2000;
68 FR 38163, June 26, 2003, 69 FR 23996, Apr. 30, 2004; 77 FR 28441, May
14, 2012]
Sec. 50.10 National 8-hour primary and secondary ambient air quality
standards for ozone.
(a) The level of the national 8-hour primary and secondary ambient
air quality standards for ozone, measured
[[Page 10]]
by a reference method based on appendix D to this part and designated in
accordance with part 53 of this chapter, is 0.08 parts per million
(ppm), daily maximum 8-hour average.
(b) The 8-hour primary and secondary ozone ambient air quality
standards are met at an ambient air quality monitoring site when the
average of the annual fourth-highest daily maximum 8-hour average ozone
concentration is less than or equal to 0.08 ppm, as determined in
accordance with appendix I to this part.
(c) Until the effective date of the final Implementation of the 2008
National Ambient Air Quality Standards for Ozone: State Implementation
Plan Requirements Rule (final SIP Requirements Rule) to be codified at
40 CFR 51.1100 et seq., the 1997 ozone NAAQS set forth in this section
will continue in effect, notwithstanding the promulgation of the 2008
ozone NAAQS under Sec. 50.15. The 1997 ozone NAAQS set forth in this
section will no longer apply upon the effective date of the final SIP
Requirements Rule. For purposes of the anti-backsliding requirements of
Sec. 51.1105, Sec. 51.165 and Appendix S to part 51, the area
designations and classifications with respect to the revoked 1997 ozone
NAAQS are codified in 40 CFR part 81.
[62 FR 38894, July 18, 1997, as amended at 77 FR 30170, May 21, 2012; 80
FR 12312, Mar. 6, 2015]
Sec. 50.11 National primary and secondary ambient air quality standards
for oxides of nitrogen (with nitrogen dioxide as the indicator).
(a) The level of the national primary annual ambient air quality
standard for oxides of nitrogen is 53 parts per billion (ppb, which is 1
part in 1,000,000,000), annual average concentration, measured in the
ambient air as nitrogen dioxide.
(b) The level of the national primary 1-hour ambient air quality
standard for oxides of nitrogen is 100 ppb, 1-hour average
concentration, measured in the ambient air as nitrogen dioxide.
(c) The level of the national secondary ambient air quality standard
for nitrogen dioxide is 0.053 parts per million (100 micrograms per
cubic meter), annual arithmetic mean concentration.
(d) The levels of the standards shall be measured by:
(1) A reference method based on appendix F to this part; or
(2) By a Federal equivalent method (FEM) designated in accordance
with part 53 of this chapter.
(e) The annual primary standard is met when the annual average
concentration in a calendar year is less than or equal to 53 ppb, as
determined in accordance with appendix S of this part for the annual
standard.
(f) The 1-hour primary standard is met when the three-year average
of the annual 98th percentile of the daily maximum 1-hour average
concentration is less than or equal to 100 ppb, as determined in
accordance with appendix S of this part for the 1-hour standard.
(g) The secondary standard is attained when the annual arithmetic
mean concentration in a calendar year is less than or equal to 0.053
ppm, rounded to three decimal places (fractional parts equal to or
greater than 0.0005 ppm must be rounded up). To demonstrate attainment,
an annual mean must be based upon hourly data that are at least 75
percent complete or upon data derived from manual methods that are at
least 75 percent complete for the scheduled sampling days in each
calendar quarter.
[75 FR 6531, Feb. 9, 2010]
Sec. 50.12 National primary and secondary ambient air quality
standards for lead.
(a) National primary and secondary ambient air quality standards for
lead and its compounds, measured as elemental lead by a reference method
based on appendix G to this part, or by an equivalent method, are: 1.5
micrograms per cubic meter, maximum arithmetic mean averaged over a
calendar quarter.
(b) The standards set forth in this section will remain applicable
to all areas notwithstanding the promulgation of lead national ambient
air quality standards (NAAQS) in Sec. 50.16. The lead NAAQS set forth
in this section will no longer apply to an area one
[[Page 11]]
year after the effective date of the designation of that area, pursuant
to section 107 of the Clean Air Act, for the lead NAAQS set forth in
Sec. 50.16; except that for areas designated nonattainment for the lead
NAAQS set forth in this section as of the effective date of Sec. 50.16,
the lead NAAQS set forth in this section will apply until that area
submits, pursuant to section 191 of the Clean Air Act, and EPA approves,
an implementation plan providing for attainment and/or maintenance of
the lead NAAQS set forth in Sec. 50.16.
(Secs. 109, 301(a) Clean Air Act as amended (42 U.S.C. 7409, 7601(a)))
[43 FR 46258, Oct. 5, 1978, as amended at 73 FR 67051, Nov. 12, 2008]
Sec. 50.13 National primary and secondary ambient air quality
standards for PM2.5.
(a) The national primary and secondary ambient air quality standards
for particulate matter are 15.0 micrograms per cubic meter ([micro]g/
m\3\) annual arithmetic mean concentration, and 35 [micro]g/m\3\ 24-hour
average concentration measured in the ambient air as PM2.5
(particles with an aerodynamic diameter less than or equal to a nominal
2.5 micrometers) by either:
(1) A reference method based on appendix L of this part and
designated in accordance with part 53 of this chapter; or
(2) An equivalent method designated in accordance with part 53 of
this chapter.
(b) The annual primary and secondary PM2.5 standards are
met when the annual arithmetic mean concentration, as determined in
accordance with appendix N of this part, is less than or equal to 15.0
[micro]g/m\3\.
(c) The 24-hour primary and secondary PM2.5 standards are
met when the 98th percentile 24-hour concentration, as determined in
accordance with appendix N of this part, is less than or equal to 35
[micro]g/m\3\.
(d) Until the effective date of the final Fine Particulate Matter
National Ambient Air Quality Standards: State Implementation Plan
Requirements rule to be codified at 40 CFR 51.1000 through 51.1016, the
1997 annual PM2.5 NAAQS set forth in this section will
continue in effect, notwithstanding the promulgation of the 2012 primary
annual PM2.5 NAAQS under Sec. 50.18. The 1997 primary annual
PM2.5 NAAQS set forth in this section will no longer apply
upon the effective date of the final Fine Particulate Matter National
Ambient Air Quality Standards: State Implementation Plan Requirements
rule; except that for areas designated nonattainment for the 1997 annual
PM2.5 NAAQS set forth in this section as of the effective
date of the final Fine Particulate Matter National Ambient Air Quality
Standards: State Implementation Plan Requirements rule, the requirements
applicable to the 1997 primary annual PM2.5 NAAQS set forth
in this section will apply until the effective date of an area's
redesignation to attainment for the 1997 annual PM2.5 NAAQS
pursuant to the requirements of section 107 of the Clean Air Act. The
1997 secondary annual PM2.5 NAAQS and the 1997 24-hour
PM2.5 NAAQS shall remain in effect. The area designations and
classifications with respect to the 1997 annual and 24-hour
PM2.5 NAAQS remain codified in 40 CFR part 81 in order to
provide information on where the 1997 primary annual PM2.5
NAAQS has been revoked and to facilitate the implementation of the 1997
secondary annual PM2.5 NAAQS and the 1997 24-hour
PM2.5 NAAQS.
[71 FR 61224, Oct. 17, 2006, as amended at 81 FR 58149, Aug. 24, 2016]
Sec. 50.14 Treatment of air quality monitoring data influenced by
exceptional events.
(a) Requirements--(1) Scope. (i) This section applies to the
treatment of data showing exceedances or violations of any national
ambient air quality standard for purposes of the following types of
regulatory determinations by the Administrator:
(A) An action to designate an area, pursuant to Clean Air Act
section 107(d)(1), or redesignate an area, pursuant to Clean Air Act
section 107(d)(3), for a particular national ambient air quality
standard;
(B) The assignment or re-assignment of a classification category to
a nonattainment area where such classification is based on a comparison
of pollutant design values, calculated according
[[Page 12]]
to the specific data handling procedures in 40 CFR part 50 for each
national ambient air quality standard, to the level of the relevant
national ambient air quality standard;
(C) A determination regarding whether a nonattainment area has
attained the level of the appropriate national ambient air quality
standard by its specified deadline;
(D) A determination that an area has data for the specific NAAQS,
which qualify the area for an attainment date extension under the CAA
provisions for the applicable pollutant;
(E) A determination under Clean Air Act section 110(k)(5), if based
on an area violating a national ambient air quality standard, that the
state implementation plan is inadequate under the requirements of Clean
Air Act section 110; and
(F) Other actions on a case-by-case basis as determined by the
Administrator.
(ii) A State, federal land manager or other federal agency may
request the Administrator to exclude data showing exceedances or
violations of any national ambient air quality standard that are
directly due to an exceptional event from use in determinations
identified in paragraph (a)(1)(i) of this section by demonstrating to
the Administrator's satisfaction that such event caused a specific air
pollution concentration at a particular air quality monitoring location.
(A) For a federal land manager or other federal agency to be
eligible to initiate such a request for data exclusion, the federal land
manager or other federal agency must:
(1) Either operate a regulatory monitor that has been affected by an
exceptional event or manage land on which an exceptional event occurred
that influenced a monitored concentration at a regulatory monitor; and
(2) Initiate such a request only after the State in which the
affected monitor is located concurs with the federal land manager's or
other federal agency's submittal.
(B) With regard to such a request, all provisions in this section
that are expressed as requirements applying to a State shall, except as
noted, be requirements applying to the federal land manager or other
federal agency.
(C) Provided all provisions in this section are met, the
Administrator shall allow a State to submit demonstrations for any
regulatory monitor within its jurisdictional bounds, including those
operated by federal land managers, other federal agencies and delegated
local agencies.
(D) Where multiple agencies within a state submit demonstrations for
events that meet the requirements of the Exceptional Events Rule, a
State submittal shall have primacy for any regulatory monitor within its
jurisdictional bounds.
(2) A demonstration to justify data exclusion may include any
reliable and accurate data, but must specifically address the elements
in paragraphs (c)(3)(iv) and (v) of this section.
(b) Determinations by the Administrator--(1) Generally. The
Administrator shall exclude data from use in determinations of
exceedances and violations identified in paragraph (a)(1)(i) of this
section where a State demonstrates to the Administrator's satisfaction
that an exceptional event caused a specific air pollution concentration
at a particular air quality monitoring location and otherwise satisfies
the requirements of this section.
(2) Fireworks displays. The Administrator shall exclude data from
use in determinations of exceedances and violations where a State
demonstrates to the Administrator's satisfaction that emissions from
fireworks displays caused a specific air pollution concentration in
excess of one or more national ambient air quality standards at a
particular air quality monitoring location and otherwise satisfies the
requirements of this section. Such data will be treated in the same
manner as exceptional events under this rule, provided a State
demonstrates that such use of fireworks is significantly integral to
traditional national, ethnic, or other cultural events including, but
not limited to, July Fourth celebrations that satisfy the requirements
of this section.
(3) Prescribed fires. (i) The Administrator shall exclude data from
use in determinations of exceedances and violations, where a State
demonstrates to
[[Page 13]]
the Administrator's satisfaction that emissions from prescribed fires
caused a specific air pollution concentration in excess of one or more
national ambient air quality standards at a particular air quality
monitoring location and otherwise satisfies the requirements of this
section.
(ii) In addressing the requirements set forth in paragraph
(c)(3)(iv)(D) of this section regarding the not reasonably controllable
or preventable criterion:
(A) With respect to the requirement that a prescribed fire be not
reasonably controllable, the State must either certify to the
Administrator that it has adopted and is implementing a smoke management
program or the State must demonstrate that the burn manager employed
appropriate basic smoke management practices identified in Table 1 to
Sec. 50.14. Where a burn manager employs appropriate basic smoke
management practices, the State may rely on a statement or other
documentation provided by the burn manager that he or she employed those
practices. If an exceedance or violation of a NAAQS occurs when a
prescribed fire is employing an appropriate basic smoke management
practices approach, the State and the burn manager must undertake a
review of the subject fire, including a review of the basic smoke
management practices applied during the subject fire to ensure the
protection of air quality and public health and progress towards
restoring and/or maintaining a sustainable and resilient wildland
ecosystem. If the prescribed fire becomes the subject of an exceptional
events demonstration, documentation of the post-burn review must
accompany the demonstration.
(B) If the State anticipates satisfying the requirements of
paragraph (c)(3)(iv)(D) of this section by employing the appropriate
basic smoke management practices identified in Table 1 to Sec. 50.14,
then:
(1) The State, federal land managers, and other entities as
appropriate, must periodically collaborate with burn managers operating
within the jurisdiction of the State to discuss and document the process
by which air agencies and land managers will work together to protect
public health and manage air quality impacts during the conduct of
prescribed fires on wildland. Such discussions must include outreach and
education regarding general expectations for the selection and
application of appropriate basic smoke management practices and goals
for advancing strategies and increasing adoption and communication of
the benefits of appropriate basic smoke management practices;
(2) The State, federal land managers and burn managers shall have an
initial implementation period, defined as being 2 years from September
30, 2016, to implement the collaboration and outreach effort identified
in paragraph (b)(3)(ii)(B)(1) of this section; and
(3) Except as provided in paragraph (b)(3)(ii)(B)(2) of this
section, the Administrator shall not place a concurrence flag in the
appropriate field for the data record in the AQS database, as specified
in paragraph (c)(2)(ii) of this section, if the data are associated with
a prescribed fire on wildland unless the requirements of paragraph
(b)(3)(ii)(B)(1) of this section have been met and associated
documentation accompanies any applicable exceptional events
demonstration. The Administrator may nonconcur or defer action on such a
demonstration.
(C) With respect to the requirement that a prescribed fire be not
reasonably preventable, the State may rely upon and reference a multi-
year land or resource management plan for a wildland area with a stated
objective to establish, restore and/or maintain a sustainable and
resilient wildland ecosystem and/or to preserve endangered or threatened
species through a program of prescribed fire provided that the
Administrator determines that there is no compelling evidence to the
contrary in the record and the use of prescribed fire in the area has
not exceeded the frequency indicated in that plan.
(iii) Provided the Administrator determines that there is no
compelling evidence to the contrary in the record, in addressing the
requirements set forth in paragraph (c)(3)(iv)(E) of this section
regarding the human activity unlikely to recur at a particular location
criterion for demonstrations involving prescribed fires on wildland,
[[Page 14]]
the State must describe the actual frequency with which a burn was
conducted, but may rely upon and reference an assessment of the natural
fire return interval or the prescribed fire frequency needed to
establish, restore and/or maintain a sustainable and resilient wildland
ecosystem contained in a multi-year land or resource management plan
with a stated objective to establish, restore and/or maintain a
sustainable and resilient wildland ecosystem and/or to preserve
endangered or threatened species through a program of prescribed fire.
Table 1 to Sec. 50.14--Summary of Basic Smoke Management Practices,
Benefit Achieved With the BSMP, and When it is Applieda
------------------------------------------------------------------------
When the BSMP is
Basic Smoke Management Benefit achieved with applied--before/
Practice \b\ the BSMP during/after the
burn
------------------------------------------------------------------------
Evaluate Smoke Dispersion Minimize smoke Before, During,
Conditions. impacts. After.
Monitor Effects on Air Quality Be aware of where the Before, During,
smoke is going and After.
degree it impacts
air quality.
Record-Keeping/Maintain a Burn/ Retain information Before, During,
Smoke Journal. about the weather, After.
burn and smoke. If
air quality problems
occur, documentation
helps analyze and
address air
regulatory issues..
Communication--Public Notify neighbors and Before, During.
Notification. those potentially
impacted by smoke,
especially sensitive
receptors.
Consider Emission Reduction Reducing emissions Before, During,
Techniques. through mechanisms After.
such as reducing
fuel loading can
reduce downwind
impacts.
Share the Airshed-- Coordinate multiple Before, During,
Coordination of Area Burning. burns in the area to After.
manage exposure of
the public to smoke.
------------------------------------------------------------------------
\a\ The EPA believes that elements of these BSMP could also be practical
and beneficial to apply to wildfires for areas likely to experience
recurring wildfires.
\b\ The listing of BSMP in this table is not intended to be all-
inclusive. Not all BSMP are appropriate for all burns. Goals for
applicability should retain flexibility to allow for onsite variation
and site-specific conditions that can be variable on the day of the
burn. Burn managers can consider other appropriate BSMP as they become
available due to technological advancement or programmatic refinement.
(4) Wildfires. The Administrator shall exclude data from use in
determinations of exceedances and violations where a State demonstrates
to the Administrator's satisfaction that emissions from wildfires caused
a specific air pollution concentration in excess of one or more national
ambient air quality standard at a particular air quality monitoring
location and otherwise satisfies the requirements of this section.
Provided the Administrator determines that there is no compelling
evidence to the contrary in the record, the Administrator will determine
every wildfire occurring predominantly on wildland to have met the
requirements identified in paragraph (c)(3)(iv)(D) of this section
regarding the not reasonably controllable or preventable criterion.
(5) High wind dust events. (i) The Administrator shall exclude data
from use in determinations of exceedances and violations, where a State
demonstrates to the Administrator's satisfaction that emissions from a
high wind dust event caused a specific air pollution concentration in
excess of one or more national ambient air quality standards at a
particular air quality monitoring location and otherwise satisfies the
requirements of this section provided that such emissions are from high
wind dust events.
(ii) The Administrator will consider high wind dust events to be
natural events in cases where windblown dust is entirely from natural
undisturbed lands in the area or where all anthropogenic sources are
reasonably controlled as determined in accordance with paragraph (b)(8)
of this section.
(iii) The Administrator will accept a high wind threshold of a
sustained wind of 25 mph for areas in the States of Arizona, California,
Colorado, Kansas, Nebraska, Nevada, New Mexico, North Dakota, Oklahoma,
South Dakota, Texas, Utah, and Wyoming provided this value is not
contradicted by evidence in the record at the time the State submits a
demonstration. In lieu of this threshold, States can identify
[[Page 15]]
and use an Administrator-approved alternate area-specific high wind
threshold that is more representative of local or regional conditions,
if appropriate.
(iv) In addressing the requirements set forth in paragraph
(c)(3)(iv)(D) of this section regarding the not reasonably preventable
criterion, the State shall not be required to provide a case-specific
justification for a high wind dust event.
(v) With respect to the not reasonably controllable criterion of
paragraph (c)(3)(iv)(D) of this section, dust controls on an
anthropogenic source shall be considered reasonable in any case in which
the controls render the anthropogenic source as resistant to high winds
as natural undisturbed lands in the area affected by the high wind dust
event. The Administrator may determine lesser controls reasonable on a
case-by-case basis.
(vi) For large-scale and high-energy high wind dust events, the
Administrator will generally consider a demonstration documenting the
nature and extent of the event to be sufficient with respect to the not
reasonably controllable criterion of paragraph (c)(3)(iv)(D) of this
section provided the State provides evidence showing that the event
satisfies the following:
(A) The event is associated with a dust storm and is the focus of a
Dust Storm Warning.
(B) The event has sustained winds that are greater than or equal to
40 miles per hour.
(C) The event has reduced visibility equal to or less than 0.5
miles.
(6) Stratospheric Intrusions. Where a State demonstrates to the
Administrator's satisfaction that emissions from stratospheric
intrusions caused a specific air pollution concentration in excess of
one or more national ambient air quality standard at a particular air
quality monitoring location and otherwise satisfies the requirements of
this section, the Administrator will determine stratospheric intrusions
to have met the requirements identified in paragraph (c)(3)(iv)(D) of
this section regarding the not reasonably controllable or preventable
criterion and shall exclude data from use in determinations of
exceedances and violations.
(7) Determinations with respect to event aggregation, multiple
national ambient air quality standards for the same pollutant, and
exclusion of 24-hour values for particulate matter.
(i) Where a State demonstrates to the Administrator's satisfaction
that for national ambient air quality standards with averaging or
cumulative periods less than or equal to 24 hours the aggregate effect
of events occurring on the same day has caused an exceedance or
violation, the Administrator shall determine such collective data to
satisfy the requirements in paragraph (c)(3)(iv)(B) of this section
regarding the clear causal relationship criterion. Where a State
demonstrates to the Administrator's satisfaction that for national
ambient air quality standards with averaging or cumulative periods
longer than 24 hours the aggregate effect of events occurring on
different days has caused an exceedance or violation, the Administrator
shall determine such collective data to satisfy the requirements in
paragraph (c)(3)(iv)(B) of this section regarding the clear causal
relationship criterion.
(ii) The Administrator shall accept as part of a demonstration for
the clear causal relationship in paragraph (c)(3)(iv)(B) of this section
with respect to a 24-hour NAAQS, a State's comparison of a 24-hour
concentration of any national ambient air quality standard pollutant to
the level of a national ambient air quality standard for the same
pollutant with a longer averaging period. The Administrator shall also
accept as part of a demonstration for the clear causal relationship in
paragraph (c)(3)(iv)(B) of this section with respect to a NAAQS with a
longer averaging period, a State's comparison of a 24-hour concentration
of any national ambient air quality standard pollutant to the level of
the national ambient air quality standard for the same pollutant with a
longer averaging period, without the State having to demonstrate that
the event caused the annual average concentration of the pollutant to
exceed the level of the NAAQS with the longer averaging period.
(iii) Where a State operates a continuous analyzer that has been
designated
[[Page 16]]
as a Federal Equivalent Method monitor as defined in 40 CFR 50.1(g) that
complies with the monitoring requirements of 40 CFR part 58, Appendix C,
and the State believes that collected data have been influenced by an
event, in following the process outlined in paragraph (c)(2) of this
section, the State shall create an initial event description and flag
the associated event-influenced data that have been submitted to the AQS
database for the affected monitor. Where a State demonstrates to the
Administrator's satisfaction that such data satisfy the requirements in
paragraph (c)(3)(iv)(B) of this section regarding the clear causal
relationship criterion and otherwise satisfy the requirements of this
section, the Administrator shall agree to exclude all data within the
affected calendar day(s).
(8) Determinations with respect to the not reasonably controllable
or preventable criterion. (i) The not reasonably controllable or
preventable criterion has two prongs that the State must demonstrate:
prevention and control.
(ii) The Administrator shall determine that an event is not
reasonably preventable if the State shows that reasonable measures to
prevent the event were applied at the time of the event.
(iii) The Administrator shall determine that an event is not
reasonably controllable if the State shows that reasonable measures to
control the impact of the event on air quality were applied at the time
of the event.
(iv) The Administrator shall assess the reasonableness of available
controls for anthropogenic sources based on information available as of
the date of the event.
(v) Except where a State, tribal or federal air agency is obligated
to revise its state implementation plan, tribal implementation plan, or
federal implementation plan, the Administrator shall consider
enforceable control measures implemented in accordance with a state
implementation plan, tribal implementation plan, or federal
implementation plan, approved by the EPA within 5 years of the date of
the event, that address the event-related pollutant and all sources
necessary to fulfill the requirements of the Clean Air Act for the state
implementation plan, tribal implementation plan, or federal
implementation plan to be reasonable controls with respect to all
anthropogenic sources that have or may have contributed to the monitored
exceedance or violation.
(vi) Where a State, tribal or federal air agency is obligated to
revise its state implementation plan, tribal implementation plan, or
federal implementation plan, the deference to enforceable control
measures identified in paragraph (b)(8)(v) of this section shall remain
only until the due date of the required state implementation plan,
tribal implementation plan, or federal implementation plan revisions.
However, where an air agency is obligated to revise the enforceable
control measures identified in paragraph (b)(8)(v) of this section in
its implementation plan as a result of an action pursuant to Clean Air
Act section 110(k)(5), the deference, if any, to those enforceable
control measures shall be determined on a case-by-case basis.
(vii) The Administrator shall not require a State to provide case-
specific justification to support the not reasonably controllable or
preventable criterion for emissions-generating activity that occurs
outside of the State's jurisdictional boundaries within which the
concentration at issue was monitored. In the case of a tribe treated as
a state under 40 CFR 49.2 with respect to exceptional events
requirements, the tribe's jurisdictional boundaries for purposes of
requiring or directly implementing emission controls apply. In the case
of a federal land manager or other federal agency submitting a
demonstration under the requirements of this section, the jurisdictional
boundaries that apply are those of the State or the tribe depending on
which has jurisdiction over the area where the event has occurred.
(viii) In addition to the provisions that apply to specific event
types identified in paragraphs (b)(3)(ii) and (b)(5)(i) through (iii) of
this section in addressing the requirements set forth in paragraph
(c)(3)(iv)(D) of this section regarding the not reasonably controllable
or preventable criterion, the State must include the following
components:
[[Page 17]]
(A) Identification of the natural and anthropogenic sources of
emissions causing and contributing to the monitored exceedance or
violation, including the contribution from local sources.
(B) Identification of the relevant state implementation plan, tribal
implementation plan, or federal implementation plan or other enforceable
control measures in place for the sources identified in paragraph
(b)(8)(vii)(A) of this section and the implementation status of these
controls.
(C) Evidence of effective implementation and enforcement of the
measures identified in paragraph (b)(8)(vii)(B) of this section.
(D) The provisions in this paragraph shall not apply if the
provisions in paragraph (b)(4), (b)(5)(vi), or (b)(6) of this section
apply.
(9) Mitigation plans. (i) Except as provided for in paragraph
(b)(9)(ii) of this section, where a State is subject to the requirements
of 40 CFR 51.930(b), the Administrator shall not place a concurrence
flag in the appropriate field for the data record in the AQS database,
as specified in paragraph (c)(2)(ii) of this section, if the data are of
the type and pollutant that are the focus of the mitigation plan until
the State fulfills its obligations under the requirements of 40 CFR
51.930(b). The Administrator may nonconcur or defer action on such a
demonstration.
(ii) The prohibition on placing a concurrence flag in the
appropriate field for the data record in the AQS database by the
Administrator stated in paragraph (b)(9(i) of this section does not
apply to data that are included in an exceptional events demonstration
that is:
(A) submitted in accordance with paragraph (c)(3) of this section
that is also of the type and pollutant that is the focus of the
mitigation plan, and
(B) submitted within the 2-year period allowed for mitigation plan
development as specified in 40 CFR 51.930(b)(3).
(c) Schedules and procedures--(1) Public notification. (i) In
accordance with the mitigation requirement at 40 CFR 51.930(a)(1), all
States and, where applicable, their political subdivisions must notify
the public promptly whenever an event occurs or is reasonably
anticipated to occur which may result in the exceedance of an applicable
air quality standard.
(ii) [Reserved]
(2) Initial notification of potential exceptional event. (i) A State
shall notify the Administrator of its intent to request exclusion of one
or more measured exceedances of an applicable national ambient air
quality standard as being due to an exceptional event by creating an
initial event description and flagging the associated data that have
been submitted to the AQS database and by engaging in the Initial
Notification of Potential Exceptional Event process as follows:
(A) The State and the appropriate EPA Regional office shall engage
in regular communications to identify those data that have been
potentially influenced by an exceptional event, to determine whether the
identified data may affect a regulatory determination and to discuss
whether the State should develop and submit an exceptional events
demonstration according to the requirements in this section;
(B) For data that may affect an anticipated regulatory determination
or where circumstances otherwise compel the Administrator to prioritize
the resulting demonstration, the Administrator shall respond to a
State's Initial Notification of Potential Exceptional Event with a due
date for demonstration submittal that considers the nature of the event
and the anticipated timing of the associated regulatory decision;
(C) The Administrator may waive the Initial Notification of
Potential Exceptional Event process on a case-by-case basis.
(ii) The data shall not be excluded from determinations with respect
to exceedances or violations of the national ambient air quality
standards unless and until, following the State's submittal of its
demonstration pursuant to paragraph (c)(3) of this section and the
Administrator's review, the Administrator notifies the State of its
concurrence by placing a concurrence flag in the appropriate field for
the data record in the AQS database.
(iii) [Reserved]
(iv) [Reserved]
[[Page 18]]
(v) [Reserved]
(vi) Table 2 to Sec. 50.14 identifies the submission process for
data that will or may influence the initial designation of areas for any
new or revised national ambient air quality standard.
Table 2 to Sec. 50.14--Schedule for Initial Notification and
Demonstration Submission for Data Influenced by Exceptional Events for
Use in Initial Area Designations
------------------------------------------------------------------------
Exceptional events/Regulatory Exceptional events
action Condition deadline schedule \d\
------------------------------------------------------------------------
(A) Initial Notification If state and then the Initial
deadline for data years 1, 2 tribal initial Notification
and 3.\a\. designation deadline will be the
recommendations July 1 prior to the
for a new/ recommendation
revised national deadline.
ambient air
quality standard
are due August
through January,
(B) Initial Notification If state and then the Initial
deadline for data years 1, 2 tribal Notification
and 3.\a\. recommendations deadline will be the
for a new/ January 1 prior to
revised national the recommendation
ambient air deadline.
quality standard
are due February
through July,
(C) Exceptional events None............. no later than the
demonstration submittal later of November
deadline for data years 1, 2 29, 2016 or the date
and 3 \a\. that state and
tribal
recommendations are
due to the
Administrator.
(D) Initial Notification and None............. by the last day of
exceptional events the month that is 1
demonstration submittal year and 7 months
deadline for data year 4 \b\ after promulgation
and, where applicable, data of a new/revised
year 5.\c\. national ambient air
quality standard,
unless either
paragraph (E) or
paragraph (F)
applies.
(E) Initial Notification and If the the deadline is 2
exceptional events Administrator years and 7 months
demonstration submittal follows a 3-year after promulgation
deadline for data year 4 \b\ designation of a new/revised
and, where applicable, data schedule. national ambient air
year 5.\c\. quality standard.
(F) Initial Notification and If the the deadline is 5
exceptional events Administrator months prior to the
demonstration submittal notifies the date specified for
deadline for data year 4 \b\ state/tribe that final designations
and, where applicable, data it intends to decisions in such
year 5.\c\. complete the Administrator
initial area notification.
designations
process
according to a
schedule between
2 and 3 years,.
------------------------------------------------------------------------
\a\ Where data years 1, 2, and 3 are those years expected to be
considered in state and tribal recommendations.
\b\ Where data year 4 is the additional year of data that the
Administrator may consider when making final area designations for a
new/revised national ambient air quality standard under the standard
designations schedule.
\c\ Where data year 5 is the additional year of data that the
Administrator may consider when making final area designations for a
new/revised national ambient air quality standard under an extended
designations schedule.
\d\ The date by which air agencies must certify their ambient air
quality monitoring data in AQS is annually on May 1 of the year
following the year of data collection as specified in 40 CFR
58.15(a)(2). In some cases, however, air agencies may choose to
certify a prior year's data in advance of May 1 of the following year,
particularly if the Administrator has indicated intent to promulgate
final designations in the first 8 months of the calendar year.
Exceptional events demonstration deadlines for ``early certified''
data will follow the deadlines for ``year 4'' and ``year 5'' data.
(3) Submission of demonstrations. (i) Except as provided under
paragraph (c)(2)(vi) of this section, a State that has flagged data as
being due to an exceptional event and is requesting exclusion of the
affected measurement data shall, after notice and opportunity for public
comment, submit a demonstration to justify data exclusion to the
Administrator according to the schedule established under paragraph
(c)(2)(i)(B).
(ii) [Reserved]
(iii) [Reserved]
(iv) The demonstration to justify data exclusion must include:
(A) A narrative conceptual model that describes the event(s) causing
the exceedance or violation and a discussion of how emissions from the
event(s) led to the exceedance or violation at the affected monitor(s);
(B) A demonstration that the event affected air quality in such a
way that there exists a clear causal relationship between the specific
event and the monitored exceedance or violation;
(C) Analyses comparing the claimed event-influenced concentration(s)
to concentrations at the same monitoring site at other times to support
the requirement at paragraph (c)(3)(iv)(B) of this section. The
Administrator shall not require a State to prove a specific percentile
point in the distribution of data;
(D) A demonstration that the event was both not reasonably
controllable and not reasonably preventable; and
[[Page 19]]
(E) A demonstration that the event was a human activity that is
unlikely to recur at a particular location or was a natural event.
(v) With the submission of the demonstration containing the elements
in paragraph (c)(3)(iv) of this section, the State must:
(A) Document that the State followed the public comment process and
that the comment period was open for a minimum of 30 days, which could
be concurrent with the beginning of the Administrator's initial review
period of the associated demonstration provided the State can meet all
requirements in this paragraph;
(B) Submit the public comments it received along with its
demonstration to the Administrator; and
(C) Address in the submission to the Administrator those comments
disputing or contradicting factual evidence provided in the
demonstration.
(vi) Where the State has submitted a demonstration according to the
requirements of this section after September 30, 2016 and the
Administrator has reviewed such demonstration and requested additional
evidence to support one of the elements in paragraph (c)(3)(iv) of this
section, the State shall have 12 months from the date of the
Administrator's request to submit such evidence. At the conclusion of
this time, if the State has not submitted the requested additional
evidence, the Administrator will notify the State in writing that it
considers the demonstration to be inactive and will not pursue
additional review of the demonstration. After a 12-month period of
inactivity by the State, if a State desires to pursue the inactive
demonstration, it must reinitiate its request to exclude associated data
by following the process beginning with paragraph (c)(2)(i) of this
section.
[81 FR 68277, Oct. 3, 2016]
Sec. 50.15 National primary and secondary ambient air quality standards
for ozone.
(a) The level of the national 8-hour primary and secondary ambient
air quality standards for ozone (O3) is 0.075 parts per
million (ppm), daily maximum 8-hour average, measured by a reference
method based on appendix D to this part and designated in accordance
with part 53 of this chapter or an equivalent method designated in
accordance with part 53 of this chapter.
(b) The 8-hour primary and secondary O3 ambient air
quality standards are met at an ambient air quality monitoring site when
the 3-year average of the annual fourth-highest daily maximum 8-hour
average O3 concentration is less than or equal to 0.075 ppm,
as determined in accordance with appendix P to this part.
[73 FR 16511, Mar. 27, 2008]
Sec. 50.16 National primary and secondary ambient air quality standards
for lead.
(a) The national primary and secondary ambient air quality standards
for lead (Pb) and its compounds are 0.15 micrograms per cubic meter,
arithmetic mean concentration over a 3-month period, measured in the
ambient air as Pb either by:
(1) A reference method based on appendix G of this part and
designated in accordance with part 53 of this chapter or;
(2) An equivalent method designated in accordance with part 53 of
this chapter.
(b) The national primary and secondary ambient air quality standards
for Pb are met when the maximum arithmetic 3-month mean concentration
for a 3-year period, as determined in accordance with appendix R of this
part, is less than or equal to 0.15 micrograms per cubic meter.
[73 FR 67052, Nov. 12, 2008]
Sec. 50.17 National primary ambient air quality standards for sulfur
oxides (sulfur dioxide).
(a) The level of the national primary 1-hour annual ambient air
quality standard for oxides of sulfur is 75 parts per billion (ppb,
which is 1 part in 1,000,000,000), measured in the ambient air as sulfur
dioxide (SO2).
(b) The 1-hour primary standard is met at an ambient air quality
monitoring site when the three-year average of the annual (99th
percentile) of the daily maximum 1-hour average concentrations is less
than or equal to 75 ppb, as determined in accordance with appendix T of
this part.
[[Page 20]]
(c) The level of the standard shall be measured by a reference
method based on appendix A or A-1 of this part, or by a Federal
Equivalent Method (FEM) designated in accordance with part 53 of this
chapter.
[75 FR 35592, June 22, 2010]
Sec. 50.18 National primary ambient air quality standards for PM2.5.
(a) The national primary ambient air quality standards for
PM2.5 are 12.0 micrograms per cubic meter ([micro]g/m\3\)
annual arithmetic mean concentration and 35 [micro]g/m\3\ 24-hour
average concentration measured in the ambient air as PM2.5
(particles with an aerodynamic diameter less than or equal to a nominal
2.5 micrometers) by either:
(1) A reference method based on appendix L to this part and
designated in accordance with part 53 of this chapter; or
(2) An equivalent method designated in accordance with part 53 of
this chapter.
(b) The primary annual PM2.5 standard is met when the
annual arithmetic mean concentration, as determined in accordance with
appendix N of this part, is less than or equal to 12.0 [micro]g/m\3\.
(c) The primary 24-hour PM2.5 standard is met when the
98th percentile 24-hour concentration, as determined in accordance with
appendix N of this part, is less than or equal to 35 [micro]g/m\3\.
[78 FR 3277, Jan. 15, 2013]
Sec. 50.19 National primary and secondary ambient air quality
standards for ozone.
(a) The level of the national 8-hour primary ambient air quality
standard for ozone (O3) is 0.070 parts per million (ppm),
daily maximum 8-hour average, measured by a reference method based on
appendix D to this part and designated in accordance with part 53 of
this chapter or an equivalent method designated in accordance with part
53 of this chapter.
(b) The 8-hour primary O3 ambient air quality standard is
met at an ambient air quality monitoring site when the 3-year average of
the annual fourth-highest daily maximum 8-hour average O3
concentration is less than or equal to 0.070 ppm, as determined in
accordance with appendix U to this part.
(c) The level of the national secondary ambient air quality standard
for O3 is 0.070 ppm, daily maximum 8-hour average, measured
by a reference method based on appendix D to this part and designated in
accordance with part 53 of this chapter or an equivalent method
designated in accordance with part 53 of this chapter.
(d) The 8-hour secondary O3 ambient air quality standard
is met at an ambient air quality monitoring site when the 3-year average
of the annual fourth-highest daily maximum 8-hour average O3
concentration is less than or equal to 0.070 ppm, as determined in
accordance with appendix U to this part.
[80 FR 65452, Oct. 26, 2015]
Sec. Appendix A-1 to Part 50--Reference Measurement Principle and
Calibration Procedure for the Measurement of Sulfur Dioxide in the
Atmosphere (Ultraviolet Fluorescence Method)
1.0 Applicability
1.1 This ultraviolet fluorescence (UVF) method provides a
measurement of the concentration of sulfur dioxide (SO2) in
ambient air for determining compliance with the national primary and
secondary ambient air quality standards for sulfur oxides (sulfur
dioxide) as specified in Sec. 50.4, Sec. 50.5, and Sec. 50.17 of this
chapter. The method is applicable to the measurement of ambient
SO2 concentrations using continuous (real-time) sampling.
Additional quality assurance procedures and guidance are provided in
part 58, appendix A, of this chapter and in Reference 3.
2.0 Principle
2.1 This reference method is based on automated measurement of the
intensity of the characteristic fluorescence released by SO2
in an ambient air sample contained in a measurement cell of an analyzer
when the air sample is irradiated by ultraviolet (UV) light passed
through the cell. The fluorescent light released by the SO2
is also in the ultraviolet region, but at longer wavelengths than the
excitation light. Typically, optimum instrumental measurement of
SO2 concentrations is obtained with an excitation wavelength
in a band between approximately 190 to 230 nm, and measurement of the
SO2 fluorescence in a broad band around 320 nm, but these
wavelengths are not necessarily
[[Page 21]]
constraints of this reference method. Generally, the measurement system
(analyzer) also requires means to reduce the effects of aromatic
hydrocarbon species, and possibly other compounds, in the air sample to
control measurement interferences from these compounds, which may be
present in the ambient air. References 1 and 2 describe UVF method.
2.2 The measurement system is calibrated by referencing the
instrumental fluorescence measurements to SO2 standard
concentrations traceable to a National Institute of Standards and
Technology (NIST) primary standard for SO2 (see Calibration
Procedure below).
2.3 An analyzer implementing this measurement principle is shown
schematically in Figure 1. Designs should include a measurement cell, a
UV light source of appropriate wavelength, a UV detector system with
appropriate wave length sensitivity, a pump and flow control system for
sampling the ambient air and moving it into the measurement cell, sample
air conditioning components as necessary to minimize measurement
interferences, suitable control and measurement processing capability,
and other apparatus as may be necessary. The analyzer must be designed
to provide accurate, repeatable, and continuous measurements of
SO2 concentrations in ambient air, with measurement
performance as specified in Subpart B of Part 53 of this chapter.
2.4 Sampling considerations: The use of a particle filter on the
sample inlet line of a UVF SO2 analyzer is required to
prevent interference, malfunction, or damage due to particles in the
sampled air.
3.0 Interferences
3.1 The effects of the principal potential interferences may need to
be mitigated to meet the interference equivalent requirements of part 53
of this chapter. Aromatic hydrocarbons such as xylene and naphthalene
can fluoresce and act as strong positive interferences. These gases can
be removed by using a permeation type scrubber (hydrocarbon ``kicker'').
Nitrogen oxide (NO) in high concentrations can also fluoresce and cause
positive interference. Optical filtering can be employed to improve the
rejection of interference from high NO. Ozone can absorb UV light given
off by the SO2 molecule and cause a measurement offset. This
effect can be reduced by minimizing the measurement path length between
the area where SO2 fluorescence occurs and the
photomultiplier tube detector (e.g., <5 cm). A hydrocarbon scrubber,
optical filter and appropriate distancing of the measurement path length
may be required method components to reduce interference.
4.0 Calibration Procedure
Atmospheres containing accurately known concentrations of sulfur
dioxide are prepared using a compressed gas transfer standard diluted
with accurately metered clean air flow rates.
4.1 Apparatus: Figure 2 shows a typical generic system suitable for
diluting a SO2 gas cylinder concentration standard with clean
air through a mixing chamber to produce the desired calibration
concentration standards. A valve may be used to conveniently divert the
SO2 from the sampling manifold to provide clean zero air at
the output manifold for zero adjustment. The system may be made up using
common laboratory components, or it may be a commercially manufactured
system. In either case, the principle components are as follows:
4.1.1 SO2 standard gas flow control and measurement
devices (or a combined device) capable of regulating and maintaining the
standard gas flow rate constant to within 2
percent and measuring the gas flow rate accurate to within 2, properly calibrated to a NIST-traceable standard.
4.1.2 Dilution air flow control and measurement devices (or a
combined device) capable of regulating and maintaining the air flow rate
constant to within 2 percent and measuring the air
flow rate accurate to within 2, properly
calibrated to a NIST-traceable standard.
4.1.3 Mixing chamber, of an inert material such as glass and of
proper design to provide thorough mixing of pollutant gas and diluent
air streams.
4.1.4 Sampling manifold, constructed of glass,
polytetrafluoroethylene (PTFE Teflon \TM\), or other suitably inert
material and of sufficient diameter to insure a minimum pressure drop at
the analyzer connection, with a vent designed to insure a minimum over-
pressure (relative to ambient air pressure) at the analyzer connection
and to prevent ambient air from entering the manifold.
4.1.5 Standard gas pressure regulator, of clean stainless steel with
a stainless steel diaphragm, suitable for use with a high pressure
SO2 gas cylinder.
4.1.6 Reagents
4.1.6.1 SO2 gas concentration transfer standard having a
certified SO2 concentration of not less than 10 ppm, in
N2, traceable to a NIST Standard Reference Material (SRM).
4.1.6.2 Clean zero air, free of contaminants that could cause a
detectable response or a change in sensitivity of the analyzer. Since
ultraviolet fluorescence analyzers may be sensitive to aromatic
hydrocarbons and O2-to-N2 ratios, it is important
that the clean zero air contains less than 0.1 ppm aromatic hydrocarbons
and O2 and N2 percentages approximately the same
as in ambient air. A
[[Page 22]]
procedure for generating zero air is given in reference 1.
4.2 Procedure
4.2.1 Obtain a suitable calibration apparatus, such as the one shown
schematically in Figure 1, and verify that all materials in contact with
the pollutant are of glass, Teflon \TM\, or other suitably inert
material and completely clean.
4.2.2 Purge the SO2 standard gas lines and pressure
regulator to remove any residual air.
4.2.3 Ensure that there are no leaks in the system and that the flow
measuring devices are properly and accurately calibrated under the
conditions of use against a reliable volume or flow rate standard such
as a soap-bubble meter or a wet-test meter traceable to a NIST standard.
All volumetric flow rates should be corrected to the same reference
temperature and pressure by using the formula below:
[GRAPHIC] [TIFF OMITTED] TR22JN10.000
Where:
Fc = corrected flow rate (L/min at 25 [deg]C and 760 mm Hg),
Fm = measured flow rate, (at temperature, Tm and pressure,
Pm),
Pm = measured pressure in mm Hg, (absolute), and
Tm = measured temperature in degrees Celsius.
4.2.4 Allow the SO2 analyzer under calibration to sample
zero air until a stable response is obtained, then make the proper zero
adjustment.
4.2.5 Adjust the airflow to provide an SO2 concentration
of approximately 80 percent of the upper measurement range limit of the
SO2 instrument and verify that the total air flow of the
calibration system exceeds the demand of all analyzers sampling from the
output manifold (with the excess vented).
4.2.6 Calculate the actual SO2 calibration concentration
standard as:
[GRAPHIC] [TIFF OMITTED] TR22JN10.001
Where:
C = the concentration of the SO2 gas standard
Fp = the flow rate of SO2 gas standard
Ft = the total air flow rate of pollutant and diluent gases
4.2.7 When the analyzer response has stabilized, adjust the
SO2 span control to obtain the desired response equivalent to
the calculated standard concentration. If substantial adjustment of the
span control is needed, it may be necessary to re-check the zero and
span adjustments by repeating steps 4.2.4 through 4.2.7 until no further
adjustments are needed.
4.2.8 Adjust the flow rate(s) to provide several other
SO2 calibration concentrations over the analyzer's
measurement range. At least five different concentrations evenly spaced
throughout the analyzer's range are suggested.
4.2.9 Plot the analyzer response (vertical or Y-axis) versus
SO2 concentration (horizontal or X-axis). Compute the linear
regression slope and intercept and plot the regression line to verify
that no point deviates from this line by more than 2 percent of the
maximum concentration tested.
Note: Additional information on calibration and pollutant standards
is provided in Section 12 of Reference 3.
5.0 Frequency of Calibration
The frequency of calibration, as well as the number of points
necessary to establish the calibration curve and the frequency of other
performance checking will vary by analyzer; however, the minimum
frequency, acceptance criteria, and subsequent actions are specified in
Reference 3, Appendix D: Measurement Quality Objectives and Validation
Template for SO2 (page 9 of 30). The user's quality control
program should provide guidelines for initial establishment of these
variables and for subsequent alteration as
[[Page 23]]
operational experience is accumulated. Manufacturers of analyzers should
include in their instruction/operation manuals information and guidance
as to these variables and on other matters of operation, calibration,
routine maintenance, and quality control.
6.0 References for SO2 Method
1. H. Okabe, P. L. Splitstone, and J. J. Ball, ``Ambient and Source
SO2 Detector Based on a Fluorescence Method'',
Journal of the Air Control Pollution Association, vol. 23, p.
514-516 (1973).
2. F. P. Schwarz, H. Okabe, and J. K. Whittaker, ``Fluorescence
Detection of Sulfur Dioxide in Air at the Parts per Billion
Level,'' Analytical Chemistry, vol. 46, pp. 1024-1028 (1974).
3. QA Handbook for Air Pollution Measurement Systems--Volume II. Ambient
Air Quality Monitoring Programs. U.S.
[GRAPHIC] [TIFF OMITTED] TR22JN10.002
[[Page 24]]
[GRAPHIC] [TIFF OMITTED] TR22JN10.003
[75 FR 35593, June 22, 2010]
Sec. Appendix A-2 to Part 50--Reference Method for the Determination of
Sulfur Dioxide in the Atmosphere (Pararosaniline Method)
1.0 Applicability.
1.1 This method provides a measurement of the concentration of
sulfur dioxide (SO2) in ambient air for determining
compliance with the primary and secondary national ambient air quality
standards for sulfur oxides (sulfur dioxide) as specified in Sec. 50.4
and Sec. 50.5 of this chapter. The method is applicable to the
measurement of ambient SO2 concentrations using sampling
periods ranging from 30 minutes to 24 hours. Additional quality
assurance procedures and guidance are provided in part 58, appendixes A
and B, of this chapter and in references 1 and 2.
2.0 Principle.
2.1 A measured volume of air is bubbled through a solution of 0.04 M
potassium tetrachloromercurate (TCM). The SO2 present in the
air stream reacts with the TCM solution to form a stable
monochlorosulfonatomercurate(3) complex. Once formed, this complex
resists air oxidation(4, 5) and is stable in the presence of strong
oxidants such as ozone and oxides of nitrogen. During subsequent
analysis, the complex is reacted with acid-bleached pararosaniline dye
and formaldehyde to form an intensely colored pararosaniline methyl
sulfonic acid.
(6) The optical density of this species is determined
spectrophotometrically at 548 nm and is directly related to the amount
of SO2 collected. The total volume of air sampled, corrected
to EPA reference conditions (25 [deg]C, 760 mm Hg [101 kPa]), is
determined from the measured flow rate and the sampling time. The
concentration of SO2 in the ambient air is computed and
expressed in micrograms per standard cubic meter ([micro]g/std m\3\).
3.0 Range.
3.1 The lower limit of detection of SO2 in 10 mL of TCM
is 0.75 [micro]g (based on collaborative
[[Page 25]]
test results).(7) This represents a concentration of 25 [micro]g
SO2/m\3\ (0.01 ppm) in an air sample of 30 standard liters
(short-term sampling) and a concentration of 13 [micro]g SO2/
m\3\ (0.005 ppm) in an air sample of 288 standard liters (long-term
sampling). Concentrations less than 25 [micro]g SO2/m\3\ can
be measured by sampling larger volumes of ambient air; however, the
collection efficiency falls off rapidly at low concentrations.(8, 9)
Beer's law is adhered to up to 34 [micro]g of SO2 in 25 mL of
final solution. This upper limit of the analysis range represents a
concentration of 1,130 [micro]g SO2/m\3\ (0.43 ppm) in an air
sample of 30 standard liters and a concentration of 590 [micro]g
SO2/m\3\ (0.23 ppm) in an air sample of 288 standard liters.
Higher concentrations can be measured by collecting a smaller volume of
air, by increasing the volume of absorbing solution, or by diluting a
suitable portion of the collected sample with absorbing solution prior
to analysis.
4.0 Interferences.
4.1 The effects of the principal potential interferences have been
minimized or eliminated in the following manner: Nitrogen oxides by the
addition of sulfamic acid,(10, 11) heavy metals by the addition of
ethylenediamine tetracetic acid disodium salt (EDTA) and phosphoric
acid,(10, 12) and ozone by time delay.(10) Up to 60 [micro]g Fe (III),
22 [micro]g V (V), 10 [micro]g Cu (II), 10 [micro]g Mn (II), and 10
[micro]g Cr (III) in 10 mL absorbing reagent can be tolerated in the
procedure.(10) No significant interference has been encountered with 2.3
[micro]g NH3.(13)
5.0 Precision and Accuracy.
5.1 The precision of the analysis is 4.6 percent (at the 95 percent
confidence level) based on the analysis of standard sulfite samples.(10)
5.2 Collaborative test results (14) based on the analysis of
synthetic test atmospheres (SO2 in scrubbed air) using the
24-hour sampling procedure and the sulfite-TCM calibration procedure
show that:
The replication error varies linearly with
concentration from 2.5 [micro]g/m\3\ at
concentrations of 100 [micro]g/m\3\ to 7 [micro]g/
m\3\ at concentrations of 400 [micro]g/m\3\.
The day-to-day variability within an individual
laboratory (repeatability) varies linearly with concentration from
18.1 [micro]g/m\3\ at levels of 100 [micro]g/m\3\
to 50.9 [micro]g/m\3\ at levels of 400 [micro]g/
m\3\.
The day-to-day variability between two or more
laboratories (reproducibility) varies linearly with concentration from
36.9 [micro]g/m\3\ at levels of 100 [micro]g/m\3\
to 103.5 [micro] g/m\3\ at levels of 400 [micro]g/
m\3\.
The method has a concentration-dependent bias, which
becomes significant at the 95 percent confidence level at the high
concentration level. Observed values tend to be lower than the expected
SO2 concentration level.
6.0 Stability.
6.1 By sampling in a controlled temperature environment of 15[deg]
10 [deg]C, greater than 98.9 percent of the
SO2-TCM complex is retained at the completion of sampling.
(15) If kept at 5 [deg]C following the completion of sampling, the
collected sample has been found to be stable for up to 30 days. (10) The
presence of EDTA enhances the stability of SO2 in the TCM
solution and the rate of decay is independent of the concentration of
SO2. (16)
7.0 Apparatus.
7.1 Sampling.
7.1.1 Sample probe: A sample probe meeting the requirements of
section 7 of 40 CFR part 58, appendix E (Teflon [supreg] or glass with
residence time less than 20 sec.) is used to transport ambient air to
the sampling train location. The end of the probe should be designed or
oriented to preclude the sampling of precipitation, large particles,
etc. A suitable probe can be constructed from Teflon [supreg] tubing
connected to an inverted funnel.
7.1.2 Absorber--short-term sampling: An all glass midget impinger
having a solution capacity of 30 mL and a stem clearance of 4 1 mm from the bottom of the vessel is used for sampling
periods of 30 minutes and 1 hour (or any period considerably less than
24 hours). Such an impinger is shown in Figure 1. These impingers are
commercially available from distributors such as Ace Glass,
Incorporated.
7.1.3 Absorber--24-hour sampling: A polypropylene tube 32 mm in
diameter and 164 mm long (available from Bel Art Products, Pequammock,
NJ) is used as the absorber. The cap of the absorber must be a
polypropylene cap with two ports (rubber stoppers are unacceptable
because the absorbing reagent can react with the stopper to yield
erroneously high SO2 concentrations). A glass impinger stem,
6 mm in diameter and 158 mm long, is inserted into one port of the
absorber cap. The tip of the stem is tapered to a small diameter orifice
(0.4 0.1 mm) such that a No. 79 jeweler's drill
bit will pass through the opening but a No. 78 drill bit will not.
Clearance from the bottom of the absorber to the tip of the stem must be
6 2 mm. Glass stems can be fabricated by any
reputable glass blower or can be obtained from a scientific supply firm.
Upon receipt, the orifice test should be performed to verify the orifice
size. The 50 mL volume level should be permanently marked on the
absorber. The assembled absorber is shown in Figure 2.
7.1.4 Moisture trap: A moisture trap constructed of a glass trap as
shown in Figure 1 or a polypropylene tube as shown in Figure 2 is placed
between the absorber tube and flow control device to prevent entrained
liquid from reaching the flow control device. The tube is packed with
indicating silica gel as shown in Figure 2. Glass wool may be
substituted for silica gel when collecting short-term samples (1 hour or
less) as shown in
[[Page 26]]
Figure 1, or for long term (24 hour) samples if flow changes are not
routinely encountered.
7.1.5 Cap seals: The absorber and moisture trap caps must seal
securely to prevent leaks during use. Heat-shrink material as shown in
Figure 2 can be used to retain the cap seals if there is any chance of
the caps coming loose during sampling, shipment, or storage.
[[Page 27]]
[[Page 28]]
7.1.6 Flow control device: A calibrated rotameter and needle valve
combination capable of maintaining and measuring air flow to within
2 percent is suitable for short-term sampling but
may not be used for long-term sampling. A critical orifice can be used
for regulating flow rate for both long-term and short-term sampling. A
22-gauge hypodermic needle 25 mm long may be used as a critical orifice
to yield a flow rate of approximately 1 L/min for a 30-minute sampling
period. When sampling for 1 hour, a 23-gauge hypodermic needle 16 mm in
length will provide a flow rate of approximately 0.5 L/min. Flow control
for a 24-hour sample may be provided by a 27-gauge hypodermic needle
critical orifice that is 9.5 mm in length. The flow rate should be in
the range of 0.18 to 0.22 L/min.
7.1.7 Flow measurement device: Device calibrated as specified in
9.4.1 and used to measure sample flow rate at the monitoring site.
7.1.8 Membrane particle filter: A membrane filter of 0.8 to 2
[micro]m porosity is used to protect the flow controller from particles
during long-term sampling. This item is optional for short-term
sampling.
7.1.9 Vacuum pump: A vacuum pump equipped with a vacuum gauge and
capable of maintaining at least 70 kPa (0.7 atm) vacuum differential
across the flow control device at the specified flow rate is required
for sampling.
7.1.10 Temperature control device: The temperature of the absorbing
solution during sampling must be maintained at 15[deg] 10 [deg]C. As soon as possible following sampling and
until analysis, the temperature of the collected sample must be
maintained at 5[deg] 5 [deg]C. Where an extended
period of time may elapse before the collected sample can be moved to
the lower storage temperature, a collection temperature near the lower
limit of the 15 10 [deg]C range should be used to
minimize losses during this period. Thermoelectric coolers specifically
designed for this temperature control are available commercially and
normally operate in the range of 5[deg] to 15 [deg]C. Small
refrigerators can be modified to provide the required temperature
control; however, inlet lines must be insulated from the lower
temperatures to prevent condensation when sampling under humid
conditions. A small heating pad may be necessary when sampling at low
temperatures (<7 [deg]C) to prevent the absorbing solution from
freezing.(17)
7.1.11 Sampling train container: The absorbing solution must be
shielded from light during and after sampling. Most commercially
available sampler trains are enclosed in a light-proof box.
7.1.12 Timer: A timer is recommended to initiate and to stop
sampling for the 24-hour period. The timer is not a required piece of
equipment; however, without the timer a technician would be required to
start and stop the sampling manually. An elapsed time meter is also
recommended to determine the duration of the sampling period.
7.2 Shipping.
7.2.1 Shipping container: A shipping container that can maintain a
temperature of 5[deg] 5 [deg]C is used for
transporting the sample from the collection site to the analytical
laboratory. Ice coolers or refrigerated shipping containers have been
found to be satisfactory. The use of eutectic cold packs instead of ice
will give a more stable temperature control. Such equipment is available
from Cole-Parmer Company, 7425 North Oak Park Avenue, Chicago, IL 60648.
7.3 Analysis.
7.3.1 Spectrophotometer: A spectrophotometer suitable for
measurement of absorbances at 548 nm with an effective spectral
bandwidth of less than 15 nm is required for analysis. If the
spectrophotometer reads out in transmittance, convert to absorbance as
follows:
[GRAPHIC] [TIFF OMITTED] TC08NO91.000
where:
A = absorbance, and
T = transmittance (0<=T<1).
A standard wavelength filter traceable to the National Bureau of
Standards is used to verify the wavelength calibration according to the
procedure enclosed with the filter. The wavelength calibration must be
verified upon initial receipt of the instrument and after each 160 hours
of normal use or every 6 months, whichever occurs first.
7.3.2 Spectrophotometer cells: A set of 1-cm path length cells
suitable for use in the visible region is used during analysis. If the
cells are unmatched, a matching correction factor must be determined
according to Section 10.1.
7.3.3 Temperature control device: The color development step during
analysis must be conducted in an environment that is in the range of
20[deg] to 30 [deg]C and controlled to 1 [deg]C.
Both calibration and sample analysis must be performed under identical
conditions (within 1 [deg]C). Adequate temperature control may be
obtained by means of constant temperature baths, water baths with manual
temperature control, or temperature controlled rooms.
7.3.4 Glassware: Class A volumetric glassware of various capacities
is required for preparing and standardizing reagents and standards and
for dispensing solutions during analysis. These included pipets,
volumetric flasks, and burets.
7.3.5 TCM waste receptacle: A glass waste receptacle is required for
the storage of spent TCM solution. This vessel should be stoppered and
stored in a hood at all times.
8.0 Reagents.
8.1 Sampling.
[[Page 29]]
8.1.1 Distilled water: Purity of distilled water must be verified by
the following procedure:(18)
Place 0.20 mL of potassium permanganate solution
(0.316 g/L), 500 mL of distilled water, and 1mL of concentrated sulfuric
acid in a chemically resistant glass bottle, stopper the bottle, and
allow to stand.
If the permanganate color (pink) does not disappear
completely after a period of 1 hour at room temperature, the water is
suitable for use.
If the permanganate color does disappear, the water
can be purified by redistilling with one crystal each of barium
hydroxide and potassium permanganate in an all glass still.
8.1.2 Absorbing reagent (0.04 M potassium tetrachloromercurate
[TCM]): Dissolve 10.86 g mercuric chloride, 0.066 g EDTA, and 6.0 g
potassium chloride in distilled water and dilute to volume with
distilled water in a 1,000-mL volumetric flask. (Caution: Mercuric
chloride is highly poisonous. If spilled on skin, flush with water
immediately.) The pH of this reagent should be between 3.0 and 5.0 (10)
Check the pH of the absorbing solution by using pH indicating paper or a
pH meter. If the pH of the solution is not between 3.0 and 5.0, dispose
of the solution according to one of the disposal techniques described in
Section 13.0. The absorbing reagent is normally stable for 6 months. If
a precipitate forms, dispose of the reagent according to one of the
procedures described in Section 13.0.
8.2 Analysis.
8.2.1 Sulfamic acid (0.6%): Dissolve 0.6 g sulfamic acid in 100 mL
distilled water. Perpare fresh daily.
8.2.2 Formaldehyde (0.2%): Dilute 5 mL formaldehyde solution (36 to
38 percent) to 1,000 mL with distilled water. Prepare fresh daily.
8.2.3 Stock iodine solution (0.1 N): Place 12.7 g resublimed iodine
in a 250-mL beaker and add 40 g potassium iodide and 25 mL water. Stir
until dissolved, transfer to a 1,000 mL volumetric flask and dilute to
volume with distilled water.
8.2.4 Iodine solution (0.01 N): Prepare approximately 0.01 N iodine
solution by diluting 50 mL of stock iodine solution (Section 8.2.3) to
500 mL with distilled water.
8.2.5 Starch indicator solution: Triturate 0.4 g soluble starch and
0.002 g mercuric iodide (preservative) with enough distilled water to
form a paste. Add the paste slowly to 200 mL of boiling distilled water
and continue boiling until clear. Cool and transfer the solution to a
glass stopperd bottle.
8.2.6 1 N hydrochloric acid: Slowly and while stirring, add 86 mL of
concentrated hydrochloric acid to 500 mL of distilled water. Allow to
cool and dilute to 1,000 mL with distilled water.
8.2.7 Potassium iodate solution: Accurately weigh to the nearest 0.1
mg, 1.5 g (record weight) of primary standard grade potassium iodate
that has been previously dried at 180 [deg]C for at least 3 hours and
cooled in a dessicator. Dissolve, then dilute to volume in a 500-mL
volumetric flask with distilled water.
8.2.8 Stock sodium thiosulfate solution (0.1 N): Prepare a stock
solution by dissolving 25 g sodium thiosulfate (Na2
S2 O3 / 5H2 O) in 1,000 mL freshly
boiled, cooled, distilled water and adding 0.1 g sodium carbonate to the
solution. Allow the solution to stand at least 1 day before
standardizing. To standardize, accurately pipet 50 mL of potassium
iodate solution (Section 8.2.7) into a 500-mL iodine flask and add 2.0 g
of potassium iodide and 10 mL of 1 N HCl. Stopper the flask and allow to
stand for 5 minutes. Titrate the solution with stock sodium thiosulfate
solution (Section 8.2.8) to a pale yellow color. Add 5 mL of starch
solution (Section 8.2.5) and titrate until the blue color just
disappears. Calculate the normality (Ns) of the stock sodium
thiosulfate solution as follows:
[GRAPHIC] [TIFF OMITTED] TC08NO91.001
where:
M = volume of thiosulfate required in mL, and
W = weight of potassium iodate in g (recorded weight in Section 8.2.7).
[GRAPHIC] [TIFF OMITTED] TC08NO91.002
8.2.9 Working sodium thiosulfate titrant (0.01 N): Accurately pipet
100 mL of stock sodium thiosulfate solution (Section 8.2.8) into a
1,000-mL volumetric flask and dilute to volume with freshly boiled,
cooled, distilled water. Calculate the normality of the working sodium
thiosulfate titrant (NT) as follows:
[GRAPHIC] [TIFF OMITTED] TC08NO91.003
8.2.10 Standardized sulfite solution for the preparation of working
sulfite-TCM solution: Dissolve 0.30 g sodium metabisulfite
(Na2 S2 O5) or 0.40 g sodium sulfite
(Na2 SO3) in 500 mL of recently boiled, cooled,
distilled water. (Sulfite solution is unstable; it is therefore
important to use water of the highest purity to minimize this
instability.) This solution contains the equivalent of 320 to 400
[micro]g SO2/mL. The actual concentration of the solution is
determined by adding excess iodine and back-titrating with standard
sodium thiosulfate solution. To back-titrate, pipet 50 mL of the 0.01 N
iodine solution (Section 8.2.4) into each of two 500-mL iodine flasks (A
and B). To flask A (blank) add 25 mL distilled water, and to flask B
(sample)
[[Page 30]]
pipet 25 mL sulfite solution. Stopper the flasks and allow to stand for
5 minutes. Prepare the working sulfite-TCM solution (Section 8.2.11)
immediately prior to adding the iodine solution to the flasks. Using a
buret containing standardized 0.01 N thiosulfate titrant (Section
8.2.9), titrate the solution in each flask to a pale yellow color. Then
add 5 mL starch solution (Section 8.2.5) and continue the titration
until the blue color just disappears.
8.2.11 Working sulfite-TCM solution: Accurately pipet 5 mL of the
standard sulfite solution (Section 8.2.10) into a 250-mL volumetric
flask and dilute to volume with 0.04 M TCM. Calculate the concentration
of sulfur dioxide in the working solution as follows:
[GRAPHIC] [TIFF OMITTED] TC08NO91.004
where:
A = volume of thiosulfate titrant required for the blank, mL;
B = volume of thiosulfate titrant required for the sample, mL;
NT = normality of the thiosulfate titrant, from equation (3);
32,000 = milliequivalent weight of SO2, [micro]g;
25 = volume of standard sulfite solution, mL; and
0.02 = dilution factor.
This solution is stable for 30 days if kept at 5 [deg]C. (16) If not
kept at 5 [deg]C, prepare fresh daily.
8.2.12 Purified pararosaniline (PRA) stock solution (0.2% nominal):
8.2.12.1 Dye specifications--
The dye must have a maximum absorbance at a
wavelength of 540 nm when assayed in a buffered solution of 0.1 M sodium
acetate-acetic acid;
The absorbance of the reagent blank, which is
temperature sensitive (0.015 absorbance unit/ [deg]C), must not exceed
0.170 at 22 [deg]C with a 1-cm optical path length when the blank is
prepared according to the specified procedure;
The calibration curve (Section 10.0) must have a
slope equal to 0.030 0.002 absorbance unit/
[micro]g SO2 with a 1-cm optical path length when the dye is
pure and the sulfite solution is properly standardized.
8.2.12.2 Preparation of stock PRA solution--A specially purified (99
to 100 percent pure) solution of pararosaniline, which meets the above
specifications, is commercially available in the required 0.20 percent
concentration (Harleco Co.). Alternatively, the dye may be purified, a
stock solution prepared, and then assayed according to the procedure as
described below.(10)
8.2.12.3 Purification procedure for PRA--
1. Place 100 mL each of 1-butanol and 1 N HCl in a large separatory
funnel (250-mL) and allow to equilibrate. Note: Certain batches of 1-
butanol contain oxidants that create an SO2 demand. Before
using, check by placing 20 mL of 1-butanol and 5 mL of 20 percent
potassium iodide (KI) solution in a 50-mL separatory funnel and shake
thoroughly. If a yellow color appears in the alcohol phase, redistill
the 1-butanol from silver oxide and collect the middle fraction or
purchase a new supply of 1-butanol.
2. Weigh 100 mg of pararosaniline hydrochloride dye (PRA) in a small
beaker. Add 50 mL of the equilibrated acid (drain in acid from the
bottom of the separatory funnel in 1.) to the beaker and let stand for
several minutes. Discard the remaining acid phase in the separatory
funnel.
3. To a 125-mL separatory funnel, add 50 mL of the equilibrated 1-
butanol (draw the 1-butanol from the top of the separatory funnel in
1.). Transfer the acid solution (from 2.) containing the dye to the
funnel and shake carefully to extract. The violet impurity will transfer
to the organic phase.
4. Transfer the lower aqueous phase into another separatory funnel,
add 20 mL of equilibrated 1-butanol, and extract again.
5. Repeat the extraction procedure with three more 10-mL portions of
equilibrated 1-butanol.
6. After the final extraction, filter the acid phase through a
cotton plug into a 50-mL volumetric flask and bring to volume with 1 N
HCl. This stock reagent will be a yellowish red.
7. To check the purity of the PRA, perform the assay and adjustment
of concentration (Section 8.2.12.4) and prepare a reagent blank (Section
11.2); the absorbance of this reagent blank at 540 nm should be less
than 0.170 at 22 [deg]C. If the absorbance is greater than 0.170 under
these conditions, further extractions should be performed.
8.2.12.4 PRA assay procedure--The concentration of pararosaniline
hydrochloride (PRA) need be assayed only once after purification. It is
also recommended that commercial solutions of pararosaniline be assayed
when first purchased. The assay procedure is as follows:(10)
1. Prepare 1 M acetate-acetic acid buffer stock solution with a pH
of 4.79 by dissolving
[[Page 31]]
13.61 g of sodium acetate trihydrate in distilled water in a 100-mL
volumetric flask. Add 5.70 mL of glacial acetic acid and dilute to
volume with distilled water.
2. Pipet 1 mL of the stock PRA solution obtained from the
purification process or from a commercial source into a 100-mL
volumetric flask and dilute to volume with distilled water.
3. Transfer a 5-mL aliquot of the diluted PRA solution from 2. into
a 50-mL volumetric flask. Add 5mL of 1 M acetate-acetic acid buffer
solution from 1. and dilute the mixture to volume with distilled water.
Let the mixture stand for 1 hour.
4. Measure the absorbance of the above solution at 540 nm with a
spectrophotometer against a distilled water reference. Compute the
percentage of nominal concentration of PRA by
[GRAPHIC] [TIFF OMITTED] TC08NO91.005
where:
A = measured absorbance of the final mixture (absorbance units);
W = weight in grams of the PRA dye used in the assay to prepare 50 mL of
stock solution (for example, 0.100 g of dye was used to
prepare 50 mL of solution in the purification procedure; when
obtained from commercial sources, use the stated concentration
to compute W; for 98% PRA, W = .098 g.); and
K = 21.3 for spectrophotometers having a spectral bandwidth of less than
15 nm and a path length of 1 cm.
8.2.13 Pararosaniline reagent: To a 250-mL volumetric flask, add 20
mL of stock PRA solution. Add an additional 0.2 mL of stock solution for
each percentage that the stock assays below 100 percent. Then add 25 mL
of 3 M phosphoric acid and dilute to volume with distilled water. The
reagent is stable for at least 9 months. Store away from heat and light.
9.0 Sampling Procedure.
9.1 General Considerations. Procedures are described for short-term
sampling (30-minute and 1-hour) and for long-term sampling (24-hour).
Different combinations of absorbing reagent volume, sampling rate, and
sampling time can be selected to meet special needs. For combinations
other than those specifically described, the conditions must be adjusted
so that linearity is maintained between absorbance and concentration
over the dynamic range. Absorbing reagent volumes less than 10 mL are
not recommended. The collection efficiency is above 98 percent for the
conditions described; however, the efficiency may be substantially lower
when sampling concentrations below 25 [micro][gamma]SO2/
m\3\.(8,9)
9.2 30-Minute and 1-Hour Sampling. Place 10 mL of TCM absorbing
reagent in a midget impinger and seal the impinger with a thin film of
silicon stopcock grease (around the ground glass joint). Insert the
sealed impinger into the sampling train as shown in Figure 1, making
sure that all connections between the various components are leak tight.
Greaseless ball joint fittings, heat shrinkable Teflon [supreg] tubing,
or Teflon [supreg] tube fittings may be used to attain leakfree
conditions for portions of the sampling train that come into contact
with air containing SO2. Shield the absorbing reagent from
direct sunlight by covering the impinger with aluminum foil or by
enclosing the sampling train in a light-proof box. Determine the flow
rate according to Section 9.4.2. Collect the sample at 1 0.10 L/min for 30-minute sampling or 0.500 0.05 L/min for 1-hour sampling. Record the exact
sampling time in minutes, as the sample volume will later be determined
using the sampling flow rate and the sampling time. Record the
atmospheric pressure and temperature.
9.3 24-Hour Sampling. Place 50 mL of TCM absorbing solution in a
large absorber, close the cap, and, if needed, apply the heat shrink
material as shown in Figure 3. Verify that the reagent level is at the
50 mL mark on the absorber. Insert the sealed absorber into the sampling
train as shown in Figure 2. At this time verify that the absorber
temperature is controlled to 15 10 [deg]C. During
sampling, the absorber temperature must be controlled to prevent
decomposition of the collected complex. From the onset of sampling until
analysis, the absorbing solution must be protected from direct sunlight.
Determine the flow rate according to Section 9.4.2. Collect the sample
for 24 hours from midnight to midnight at a flow rate of 0.200 0.020 L/min. A start/stop timer is helpful for
initiating and stopping sampling and an elapsed time meter will be
useful for determining the sampling time.
[[Page 32]]
9.4 Flow Measurement.
9.4.1 Calibration: Flow measuring devices used for the on-site flow
measurements required in 9.4.2 must be calibrated against a reliable
flow or volume standard such as an NBS traceable bubble flowmeter or
calibrated wet test meter. Rotameters or critical orifices used in the
sampling train may be calibrated, if desired, as a quality control
check, but such calibration shall not replace the on-site flow
measurements required by 9.4.2. In-line rotameters, if they are to be
calibrated, should be calibrated in situ, with the appropriate volume of
solution in the absorber.
9.4.2 Determination of flow rate at sampling site: For short-term
samples, the standard flow rate is determined at the sampling site at
the initiation and completion of sample collection with a calibrated
flow measuring device connected to the inlet of the absorber. For 24-
hour samples, the standard flow rate is determined at the time the
absorber is placed in the sampling train and again when the absorber is
removed from the train for shipment to the analytical laboratory with a
calibrated flow measuring device connected to the inlet of the sampling
train. The flow rate determination must be made with all components of
the sampling system in operation (e.g., the absorber temperature
controller and any sample box heaters must also be operating). Equation
6 may be used to determine the standard flow rate when a calibrated
positive displacement meter is used as the flow measuring device. Other
types of calibrated flow measuring devices may also be used to determine
the flow rate at the sampling site provided that the user applies any
appropriate corrections to devices for which output is dependent on
temperature or pressure.
[[Page 33]]
[GRAPHIC] [TIFF OMITTED] TC08NO91.006
where:
Qstd = flow rate at standard conditions, std L/min (25 [deg]C
and 760 mm Hg);
Qact = flow rate at monitoring site conditions, L/min;
Pb = barometric pressure at monitoring site conditions, mm Hg
or kPa;
RH = fractional relative humidity of the air being measured;
PH2O = vapor pressure of water at the temperature
of the air in the flow or volume standard, in the same units
as Pb, (for wet volume standards only, i.e., bubble
flowmeter or wet test meter; for dry standards, i.e., dry test
meter, PH2O = 0);
Pstd = standard barometric pressure, in the same units as
Pb (760 mm Hg or 101 kPa); and
Tmeter = temperature of the air in the flow or volume
standard, [deg]C (e.g., bubble flowmeter).
If a barometer is not available, the following equation may be used
to determine the barometric pressure:
[GRAPHIC] [TIFF OMITTED] TC08NO91.007
where:
H = sampling site elevation above sea level in meters.
If the initial flow rate (Qi) differs from the flow rate
of the critical orifice or the flow rate indicated by the flowmeter in
the sampling train (Qc) by more than 5 percent as determined
by equation (8), check for leaks and redetermine Qi.
[GRAPHIC] [TIFF OMITTED] TC08NO91.008
Invalidate the sample if the difference between the initial
(Qi) and final (Qf) flow rates is more than 5
percent as determined by equation (9):
[GRAPHIC] [TIFF OMITTED] TC08NO91.009
9.5 Sample Storage and Shipment. Remove the impinger or absorber
from the sampling train and stopper immediately. Verify that the
temperature of the absorber is not above 25 [deg]C. Mark the level of
the solution with a temporary (e.g., grease pencil) mark. If the sample
will not be analyzed within 12 hours of sampling, it must be stored at
5[deg] 5 [deg]C until analysis. Analysis must
occur within 30 days. If the sample is transported or shipped for a
period exceeding 12 hours, it is recommended that thermal coolers using
eutectic ice packs, refrigerated shipping containers, etc., be used for
periods up to 48 hours. (17) Measure the temperature of the absorber
solution when the shipment is received. Invalidate the sample if the
temperature is above 10 [deg]C. Store the sample at 5[deg] 5 [deg]C until it is analyzed.
10.0 Analytical Calibration.
10.1 Spectrophotometer Cell Matching. If unmatched spectrophotometer
cells are used, an absorbance correction factor must be determined as
follows:
1. Fill all cells with distilled water and designate the one that
has the lowest absorbance at 548 nm as the reference. (This reference
cell should be marked as such and continually used for this purpose
throughout all future analyses.)
2. Zero the spectrophotometer with the reference cell.
3. Determine the absorbance of the remaining cells (Ac)
in relation to the reference cell and record these values for future
use. Mark all cells in a manner that adequately identifies the
correction.
The corrected absorbance during future analyses using each cell is
determining as follows:
[GRAPHIC] [TIFF OMITTED] TC08NO91.010
where:
A = corrected absorbance,
Aobs = uncorrected absorbance, and
Ac = cell correction.
10.2 Static Calibration Procedure (Option 1). Prepare a dilute
working sulfite-TCM solution by diluting 10 mL of the working sulfite-
TCM solution (Section 8.2.11) to 100 mL with TCM absorbing reagent.
Following the table below, accurately pipet the indicated volumes of the
sulfite-TCM solutions into a series of 25-mL volumetric flasks. Add TCM
absorbing reagent as indicated to bring the volume in each flask to 10
mL.
[[Page 34]]
------------------------------------------------------------------------
Volume of Total
sulfite- Volume of [micro]g
Sulfite-TCM solution TCM TCM, mL SO2
solution (approx.*
------------------------------------------------------------------------
Working................................ 4.0 6.0 28.8
Working................................ 3.0 7.0 21.6
Working................................ 2.0 8.0 14.4
Dilute working......................... 10.0 0.0 7.2
Dilute working......................... 5.0 5.0 3.6
0.0 10.0 0.0
------------------------------------------------------------------------
*Based on working sulfite-TCM solution concentration of 7.2 [micro]g SO2/
mL; the actual total [micro]g SO2 must be calculated using equation 11
below.
To each volumetric flask, add 1 mL 0.6% sulfamic acid (Section
8.2.1), accurately pipet 2 mL 0.2% formaldehyde solution (Section
8.2.2), then add 5 mL pararosaniline solution (Section 8.2.13). Start a
laboratory timer that has been set for 30 minutes. Bring all flasks to
volume with recently boiled and cooled distilled water and mix
thoroughly. The color must be developed (during the 30-minute period) in
a temperature environment in the range of 20[deg] to 30 [deg]C, which is
controlled to 1 [deg]C. For increased precision, a
constant temperature bath is recommended during the color development
step. After 30 minutes, determine the corrected absorbance of each
standard at 548 nm against a distilled water reference (Section 10.1).
Denote this absorbance as (A). Distilled water is used in the reference
cell rather than the reagant blank because of the temperature
sensitivity of the reagent blank. Calculate the total micrograms
SO2 in each solution:
[GRAPHIC] [TIFF OMITTED] TC08NO91.011
where:
VTCM/SO2 = volume of sulfite-TCM solution used, mL;
CTCM/SO2 = concentration of sulfur dioxide in the working
sulfite-TCM, [micro]g SO2/mL (from equation 4); and
D = dilution factor (D = 1 for the working sulfite-TCM solution; D = 0.1
for the diluted working sulfite-TCM solution).
A calibration equation is determined using the method of linear
least squares (Section 12.1). The total micrograms SO2
contained in each solution is the x variable, and the corrected
absorbance (eq. 10) associated with each solution is the y variable. For
the calibration to be valid, the slope must be in the range of 0.030
0.002 absorbance unit/[micro]g SO2, the
intercept as determined by the least squares method must be equal to or
less than 0.170 absorbance unit when the color is developed at 22 [deg]C
(add 0.015 to this 0.170 specification for each [deg]C above 22 [deg]C)
and the correlation coefficient must be greater than 0.998. If these
criteria are not met, it may be the result of an impure dye and/or an
improperly standardized sulfite-TCM solution. A calibration factor
(Bs) is determined by calculating the reciprocal of the slope
and is subsequently used for calculating the sample concentration
(Section 12.3).
10.3 Dynamic Calibration Procedures (Option 2). Atmospheres
containing accurately known concentrations of sulfur dioxide are
prepared using permeation devices. In the systems for generating these
atmospheres, the permeation device emits gaseous SO2 at a
known, low, constant rate, provided the temperature of the device is
held constant (0.1 [deg]C) and the device has been
accurately calibrated at the temperature of use. The SO2
permeating from the device is carried by a low flow of dry carrier gas
to a mixing chamber where it is diluted with SO2-free air to
the desired concentration and supplied to a vented manifold. A typical
system is shown schematically in Figure 4 and this system and other
similar systems have been described in detail by O'Keeffe and Ortman;
(19) Scaringelli, Frey, and Saltzman, (20) and Scaringelli, O'Keeffe,
Rosenberg, and Bell. (21) Permeation devices may be prepared or
purchased and in both cases must be traceable either to a National
Bureau of Standards (NBS) Standard Reference Material (SRM 1625, SRM
1626, SRM 1627) or to an NBS/EPA-approved commercially available
Certified Reference Material (CRM). CRM's are described in Reference 22,
and a list of CRM sources is available from the address shown for
Reference 22. A recommended protocol for certifying a permeation device
to an NBS SRM or CRM is given in Section 2.0.7 of Reference 2. Device
permeation rates of 0.2 to 0.4 [micro]g/min, inert gas flows of about 50
mL/min, and dilution air flow rates from 1.1 to 15 L/min conveniently
yield standard atmospheres in the range of 25 to 600 [micro]g
SO2/m\3\ (0.010 to 0.230 ppm).
10.3.1 Calibration Option 2A (30-minute and 1-hour samples):
Generate a series of six standard atmospheres of SO2 (e.g.,
0, 50, 100, 200, 350, 500, 750 [micro]g/m\3\) by adjusting the dilution
flow rates appropriately. The concentration of SO2 in each
atmosphere is calculated as follows:
[GRAPHIC] [TIFF OMITTED] TR31AU93.014
where:
[[Page 35]]
Ca = concentration of SO2 at standard conditions,
[micro]g/m\3\;
Pr = permeation rate, [micro]g/min;
Qd = flow rate of dilution air, std L/min; and
Qp = flow rate of carrier gas across permeation device, std
L/min.
[[Page 36]]
Be sure that the total flow rate of the standard exceeds the flow
demand of the sample train, with the excess flow vented at atmospheric
pressure. Sample each atmosphere using similar apparatus as shown in
Figure 1 and under the same conditions as field sampling (i.e., use same
absorbing reagent volume and sample same volume of air at an equivalent
flow rate). Due to the length of the sampling periods required, this
method is not recommended for 24-hour sampling. At the completion of
sampling, quantitatively transfer the contents of each impinger to one
of a series of 25-mL volumetric flasks (if 10 mL of absorbing solution
was used) using small amounts of distilled water for rinse (<5mL). If
10 mL of absorbing solution was used, bring the absorber
solution in each impinger to orginal volume with distilled H2
O and pipet 10-mL portions from each impinger into a series of 25-mL
volumetric flasks. If the color development steps are not to be started
within 12 hours of sampling, store the solutions at 5[deg] 5 [deg]C. Calculate the total micrograms SO2
in each solution as follows:
[GRAPHIC] [TIFF OMITTED] TR31AU93.015
where:
Ca = concentration of SO2 in the standard
atmosphere, [micro]g/m\3\;
Os = sampling flow rate, std L/min;
t = sampling time, min;
Va = volume of absorbing solution used for color development
(10 mL); and
Vb = volume of absorbing solution used for sampling, mL.
Add the remaining reagents for color development in the same manner
as in Section 10.2 for static solutions. Calculate a calibration
equation and a calibration factor (Bg) according to Section
10.2, adhering to all the specified criteria.
10.3.2 Calibration Option 2B (24-hour samples): Generate a standard
atmosphere containing approximately 1,050 [micro]g SO2/m\3\
and calculate the exact concentration according to equation 12. Set up a
series of six absorbers according to Figure 2 and connect to a common
manifold for sampling the standard atmosphere. Be sure that the total
flow rate of the standard exceeds the flow demand at the sample
manifold, with the excess flow vented at atmospheric pressure. The
absorbers are then allowed to sample the atmosphere for varying time
periods to yield solutions containing 0, 0.2, 0.6, 1.0, 1.4, 1.8, and
2.2 [micro]g SO2/mL solution. The sampling times required to
attain these solution concentrations are calculated as follows:
[GRAPHIC] [TIFF OMITTED] TR31AU93.016
where:
t = sampling time, min;
Vb = volume of absorbing solution used for sampling (50 mL);
Cs = desired concentration of SO2 in the absorbing
solution, [micro]g/mL;
Ca = concentration of the standard atmosphere calculated
according to equation 12, [micro]g/m\3\; and
Qs = sampling flow rate, std L/min.
At the completion of sampling, bring the absorber solutions to
original volume with distilled water. Pipet a 10-mL portion from each
absorber into one of a series of 25-mL volumetric flasks. If the color
development steps are not to be started within 12 hours of sampling,
store the solutions at 5[deg] 5 [deg]C. Add the
remaining reagents for color development in the same manner as in
Section 10.2 for static solutions. Calculate the total [micro]g
SO2 in each standard as follows:
[GRAPHIC] [TIFF OMITTED] TR31AU93.017
where:
Va = volume of absorbing solution used for color development
(10 mL).
All other parameters are defined in equation 14.
Calculate a calibration equation and a calibration factor
(Bt) according to Section 10.2 adhering to all the specified
criteria.
11.0 Sample Preparation and Analysis.
11.1 Sample Preparation. Remove the samples from the shipping
container. If the shipment period exceeded 12 hours from the completion
of sampling, verify that the temperature is below 10 [deg]C. Also,
compare the solution level to the temporary level mark on the absorber.
If either the temperature is above 10 [deg]C or there was significant
loss (more than 10 mL) of the sample during shipping, make an
appropriate notation in the record and invalidate the sample. Prepare
the samples for analysis as follows:
1. For 30-minute or 1-hour samples: Quantitatively transfer the
entire 10 mL amount of absorbing solution to a 25-mL volumetric flask
and rinse with a small amount (<5 mL) of distilled water.
2. For 24-hour samples: If the volume of the sample is less than the
original 50-mL volume (permanent mark on the absorber), adjust the
volume back to the original volume with distilled water to compensate
for water lost to evaporation during sampling. If the final volume is
greater than the original volume, the volume must be measured using a
graduated cylinder. To analyze, pipet 10 mL
[[Page 37]]
of the solution into a 25-mL volumetric flask.
11.2 Sample Analysis. For each set of determinations, prepare a
reagent blank by adding 10 mL TCM absorbing solution to a 25-mL
volumetric flask, and two control standards containing approximately 5
and 15 [micro]g SO2, respectively. The control standards are
prepared according to Section 10.2 or 10.3. The analysis is carried out
as follows:
1. Allow the sample to stand 20 minutes after the completion of
sampling to allow any ozone to decompose (if applicable).
2. To each 25-mL volumetric flask containing reagent blank, sample,
or control standard, add 1 mL of 0.6% sulfamic acid (Section 8.2.1) and
allow to react for 10 min.
3. Accurately pipet 2 mL of 0.2% formaldehyde solution (Section
8.2.2) and then 5 mL of pararosaniline solution (Section 8.2.13) into
each flask. Start a laboratory timer set at 30 minutes.
4. Bring each flask to volume with recently boiled and cooled
distilled water and mix thoroughly.
5. During the 30 minutes, the solutions must be in a temperature
controlled environment in the range of 20[deg] to 30 [deg]C maintained
to 1 [deg]C. This temperature must also be within
1 [deg]C of that used during calibration.
6. After 30 minutes and before 60 minutes, determine the corrected
absorbances (equation 10) of each solution at 548 nm using 1-cm optical
path length cells against a distilled water reference (Section 10.1).
(Distilled water is used as a reference instead of the reagent blank
because of the sensitivity of the reagent blank to temperature.)
7. Do not allow the colored solution to stand in the cells because a
film may be deposited. Clean the cells with isopropyl alcohol after use.
8. The reagent blank must be within 0.03 absorbance units of the
intercept of the calibration equation determined in Section 10.
11.3 Absorbance range. If the absorbance of the sample solution
ranges between 1.0 and 2.0, the sample can be diluted 1:1 with a portion
of the reagent blank and the absorbance redetermined within 5 minutes.
Solutions with higher absorbances can be diluted up to sixfold with the
reagent blank in order to obtain scale readings of less than 1.0
absorbance unit. However, it is recommended that a smaller portion (<10
mL) of the original sample be reanalyzed (if possible) if the sample
requires a dilution greater than 1:1.
11.4 Reagent disposal. All reagents containing mercury compounds
must be stored and disposed of using one of the procedures contained in
Section 13. Until disposal, the discarded solutions can be stored in
closed glass containers and should be left in a fume hood.
12.0 Calculations.
12.1 Calibration Slope, Intercept, and Correlation Coefficient. The
method of least squares is used to calculate a calibration equation in
the form of:
[GRAPHIC] [TIFF OMITTED] TC08NO91.012
where:
y = corrected absorbance,
m = slope, absorbance unit/[micro]g SO2,
x = micrograms of SO2,
b = y intercept (absorbance units).
The slope (m), intercept (b), and correlation coefficient (r) are
calculated as follows:
[GRAPHIC] [TIFF OMITTED] TR31AU93.018
[GRAPHIC] [TIFF OMITTED] TR31AU93.019
[GRAPHIC] [TIFF OMITTED] TR31AU93.020
where n is the number of calibration points.
A data form (Figure 5) is supplied for easily organizing calibration
data when the slope, intercept, and correlation coefficient are
calculated by hand.
12.2 Total Sample Volume. Determine the sampling volume at standard
conditions as follows:
[GRAPHIC] [TIFF OMITTED] TR31AU93.021
where:
Vstd = sampling volume in std L,
Qi = standard flow rate determined at the initiation of
sampling in std L/min,
Qf = standard flow rate determined at the completion of
sampling is std L/min, and
t = total sampling time, min.
12.3 Sulfur Dioxide Concentration. Calculate and report the
concentration of each sample as follows:
[GRAPHIC] [TIFF OMITTED] TR31AU93.022
where:
A = corrected absorbance of the sample solution, from equation (10);
Ao = corrected absorbance of the reagent blank, using
equation (10);
BX = calibration factor equal to Bs,
Bg, or Bt depending on the calibration
procedure used, the reciprocal of the slope of the calibration
equation;
Va = volume of absorber solution analyzed, mL;
Vb = total volume of solution in absorber (see 11.1-2), mL;
and
Vstd = standard air volume sampled, std L (from Section
12.2).
[[Page 38]]
Data Form
[For hand calculations]
----------------------------------------------------------------------------------------------------------------
Absor- bance
Calibration point no. Micro- grams So2 units
----------------------------------------------------------------------------------------------------------------
(x) (y) x\2\ xy y\2\
1............................. ................. ................. ................. ................ .....
2............................. ................. ................. ................. ................ .....
3............................. ................. ................. ................. ................ .....
4............................. ................. ................. ................. ................ .....
5............................. ................. ................. ................. ................ .....
6............................. ................. ................. ................. ................ .....
----------------------------------------------------------------------------------------------------------------
[Sigma] x=___ [Sigma] y=___ [Sigma] x\2\=___ [Sigma]xy___ [Sigma]y\2\___
n=___ (number of pairs of coordinates.)
________________________________________________________________________
Figure 5. Data form for hand calculations.
12.4 Control Standards. Calculate the analyzed micrograms of
SO2 in each control standard as follows:
[GRAPHIC] [TIFF OMITTED] TC08NO91.070
where:
Cq = analyzed [micro]g SO2 in each control
standard,
A = corrected absorbance of the control standard, and
Ao = corrected absorbance of the reagent blank.
The difference between the true and analyzed values of the control
standards must not be greater than 1 [micro]g. If the difference is
greater than 1 [micro]g, the source of the discrepancy must be
identified and corrected.
12.5 Conversion of [micro]g/m\3\ to ppm (v/v). If desired, the
concentration of sulfur dioxide at reference conditions can be converted
to ppm SO2 (v/v) as follows:
[GRAPHIC] [TIFF OMITTED] TR31AU93.023
13.0 The TCM absorbing solution and any reagents containing mercury
compounds must be treated and disposed of by one of the methods
discussed below. Both methods remove greater than 99.99 percent of the
mercury.
13.1 Disposal of Mercury-Containing Solutions.
13.2 Method for Forming an Amalgam.
1. Place the waste solution in an uncapped vessel in a hood.
2. For each liter of waste solution, add approximately 10 g of
sodium carbonate until neutralization has occurred (NaOH may have to be
used).
3. Following neutralization, add 10 g of granular zinc or magnesium.
4. Stir the solution in a hood for 24 hours. Caution must be
exercised as hydrogen gas is evolved by this treatment process.
5. After 24 hours, allow the solution to stand without stirring to
allow the mercury amalgam (solid black material) to settle to the bottom
of the waste receptacle.
6. Upon settling, decant and discard the supernatant liquid.
7. Quantitatively transfer the solid material to a container and
allow to dry.
8. The solid material can be sent to a mercury reclaiming plant. It
must not be discarded.
13.3 Method Using Aluminum Foil Strips.
1. Place the waste solution in an uncapped vessel in a hood.
2. For each liter of waste solution, add approximately 10 g of
aluminum foil strips. If all the aluminum is consumed and no gas is
evolved, add an additional 10 g of foil. Repeat until the foil is no
longer consumed and allow the gas to evolve for 24 hours.
3. Decant the supernatant liquid and discard.
4. Transfer the elemental mercury that has settled to the bottom of
the vessel to a storage container.
5. The mercury can be sent to a mercury reclaiming plant. It must
not be discarded.
14.0 References for SO2 Method.
1. Quality Assurance Handbook for Air Pollution Measurement Systems,
Volume I, Principles. EPA-600/9-76-005, U.S. Environmental Protection
Agency, Research Triangle Park, NC 27711, 1976.
2. Quality Assurance Handbook for Air Pollution Measurement Systems,
Volume II, Ambient Air Specific Methods. EPA-600/4-77-027a, U.S.
Environmental Protection Agency, Research Triangle Park, NC 27711, 1977.
3. Dasqupta, P. K., and K. B. DeCesare. Stability of Sulfur Dioxide
in Formaldehyde and Its Anomalous Behavior in Tetrachloromercurate (II).
Submitted for publication in Atmospheric Environment, 1982.
4. West, P. W., and G. C. Gaeke. Fixation of Sulfur Dioxide as
Disulfitomercurate (II) and Subsequent Colorimetric Estimation. Anal.
Chem., 28:1816, 1956.
5. Ephraim, F. Inorganic Chemistry. P. C. L. Thorne and E. R.
Roberts, Eds., 5th Edition, Interscience, 1948, p. 562.
6. Lyles, G. R., F. B. Dowling, and V. J. Blanchard. Quantitative
Determination of Formaldehyde in the Parts Per Hundred Million
Concentration Level. J. Air. Poll. Cont. Assoc., Vol. 15(106), 1965.
7. McKee, H. C., R. E. Childers, and O. Saenz, Jr. Collaborative
Study of Reference Method for Determination of Sulfur Dioxide in the
Atmosphere (Pararosaniline Method). EPA-APTD-0903, U.S. Environmental
Protection Agency, Research Triangle Park, NC 27711, September 1971.
8. Urone, P., J. B. Evans, and C. M. Noyes. Tracer Techniques in
Sulfur--Air Pollution Studies Apparatus and Studies of Sulfur Dioxide
Colorimetric and Conductometric Methods. Anal. Chem., 37: 1104, 1965.
[[Page 39]]
9. Bostrom, C. E. The Absorption of Sulfur Dioxide at Low
Concentrations (pphm) Studied by an Isotopic Tracer Method. Intern. J.
Air Water Poll., 9:333, 1965.
10. Scaringelli, F. P., B. E. Saltzman, and S. A. Frey.
Spectrophotometric Determination of Atmospheric Sulfur Dioxide. Anal.
Chem., 39: 1709, 1967.
11. Pate, J. B., B. E. Ammons, G. A. Swanson, and J. P. Lodge, Jr.
Nitrite Interference in Spectrophotometric Determination of Atmospheric
Sulfur Dioxide. Anal. Chem., 37:942, 1965.
12. Zurlo, N., and A. M. Griffini. Measurement of the Sulfur Dioxide
Content of the Air in the Presence of Oxides of Nitrogen and Heavy
Metals. Medicina Lavoro, 53:330, 1962.
13. Rehme, K. A., and F. P. Scaringelli. Effect of Ammonia on the
Spectrophotometric Determination of Atmospheric Concentrations of Sulfur
Dioxide. Anal. Chem., 47:2474, 1975.
14. McCoy, R. A., D. E. Camann, and H. C. McKee. Collaborative Study
of Reference Method for Determination of Sulfur Dioxide in the
Atmosphere (Pararosaniline Method) (24-Hour Sampling). EPA-650/4-74-027,
U.S. Environmental Protection Agency, Research Triangle Park, NC 27711,
December 1973.
15. Fuerst, R. G. Improved Temperature Stability of Sulfur Dioxide
Samples Collected by the Federal Reference Method. EPA-600/4-78-018,
U.S. Environmental Protection Agency, Research Triangle Park, NC 27711,
April 1978.
16. Scaringelli, F. P., L. Elfers, D. Norris, and S. Hochheiser.
Enhanced Stability of Sulfur Dioxide in Solution. Anal. Chem., 42:1818,
1970.
17. Martin, B. E. Sulfur Dioxide Bubbler Temperature Study. EPA-600/
4-77-040, U.S. Environmental Protection Agency, Research Triangle Park,
NC 27711, August 1977.
18. American Society for Testing and Materials. ASTM Standards,
Water; Atmospheric Analysis. Part 23. Philadelphia, PA, October 1968, p.
226.
19. O'Keeffe, A. E., and G. C. Ortman. Primary Standards for Trace
Gas Analysis. Anal. Chem., 38:760, 1966.
20. Scaringelli, F. P., S. A. Frey, and B. E. Saltzman. Evaluation
of Teflon Permeation Tubes for Use with Sulfur Dioxide. Amer. Ind.
Hygiene Assoc. J., 28:260, 1967.
21. Scaringelli, F. P., A. E. O'Keeffe, E. Rosenberg, and J. P.
Bell, Preparation of Known Concentrations of Gases and Vapors With
Permeation Devices Calibrated Gravimetrically. Anal. Chem., 42:871,
1970.
22. A Procedure for Establishing Traceability of Gas Mixtures to
Certain National Bureau of Standards Standard Reference Materials. EPA-
600/7-81-010, U.S. Environmental Protection Agency, Environmental
Monitoring Systems Laboratory (MD-77), Research Triangle Park, NC 27711,
January 1981.
[47 FR 54899, Dec. 6, 1982; 48 FR 17355, Apr. 22, 1983. Redesignated at
75 FR 35595, June 22, 2010]
Sec. Appendix B to Part 50--Reference Method for the Determination of
Suspended Particulate Matter in the Atmosphere (High-Volume Method)
1.0 Applicability.
1.1 This method provides a measurement of the mass concentration of
total suspended particulate matter (TSP) in ambient air for determining
compliance with the primary and secondary national ambient air quality
standards for particulate matter as specified in Sec. 50.6 and Sec.
50.7 of this chapter. The measurement process is nondestructive, and the
size of the sample collected is usually adequate for subsequent chemical
analysis. Quality assurance procedures and guidance are provided in part
58, appendixes A and B, of this chapter and in References 1 and 2.
2.0 Principle.
2.1 An air sampler, properly located at the measurement site, draws
a measured quantity of ambient air into a covered housing and through a
filter during a 24-hr (nominal) sampling period. The sampler flow rate
and the geometry of the shelter favor the collection of particles up to
25-50 [micro]m (aerodynamic diameter), depending on wind speed and
direction.(3) The filters used are specified to have a minimum
collection efficiency of 99 percent for 0.3 [micro]m (DOP) particles
(see Section 7.1.4).
2.2 The filter is weighed (after moisture equilibration) before and
after use to determine the net weight (mass) gain. The total volume of
air sampled, corrected to EPA standard conditions (25 [deg]C, 760 mm Hg
[101 kPa]), is determined from the measured flow rate and the sampling
time. The concentration of total suspended particulate matter in the
ambient air is computed as the mass of collected particles divided by
the volume of air sampled, corrected to standard conditions, and is
expressed in micrograms per standard cubic meter ([micro]g/std m\3\).
For samples collected at temperatures and pressures significantly
different than standard conditions, these corrected concentrations may
differ substantially from actual concentrations (micrograms per actual
cubic meter), particularly at high elevations. The actual particulate
matter concentration can be calculated from the corrected concentration
using the actual temperature and pressure during the sampling period.
3.0 Range.
3.1 The approximate concentration range of the method is 2 to 750
[micro]g/std m\3\. The upper limit is determined by the point at which
the
[[Page 40]]
sampler can no longer maintain the specified flow rate due to the
increased pressure drop of the loaded filter. This point is affected by
particle size distribution, moisture content of the collected particles,
and variability from filter to filter, among other things. The lower
limit is determined by the sensitivity of the balance (see Section 7.10)
and by inherent sources of error (see Section 6).
3.2 At wind speeds between 1.3 and 4.5 m/sec (3 and 10 mph), the
high-volume air sampler has been found to collect particles up to 25 to
50 [micro]m, depending on wind speed and direction.(3) For the filter
specified in Section 7.1, there is effectively no lower limit on the
particle size collected.
4.0 Precision.
4.1 Based upon collaborative testing, the relative standard
deviation (coefficient of variation) for single analyst precision
(repeatability) of the method is 3.0 percent. The corresponding value
for interlaboratory precision (reproducibility) is 3.7 percent.(4)
5.0 Accuracy.
5.1 The absolute accuracy of the method is undefined because of the
complex nature of atmospheric particulate matter and the difficulty in
determining the ``true'' particulate matter concentration. This method
provides a measure of particulate matter concentration suitable for the
purpose specified under Section 1.0, Applicability.
6.0 Inherent Sources of Error.
6.1 Airflow variation. The weight of material collected on the
filter represents the (integrated) sum of the product of the
instantaneous flow rate times the instantaneous particle concentration.
Therefore, dividing this weight by the average flow rate over the
sampling period yields the true particulate matter concentration only
when the flow rate is constant over the period. The error resulting from
a nonconstant flow rate depends on the magnitude of the instantaneous
changes in the flow rate and in the particulate matter concentration.
Normally, such errors are not large, but they can be greatly reduced by
equipping the sampler with an automatic flow controlling mechanism that
maintains constant flow during the sampling period. Use of a contant
flow controller is recommended.*
---------------------------------------------------------------------------
*At elevated altitudes, the effectiveness of automatic flow
controllers may be reduced because of a reduction in the maximum sampler
flow.
---------------------------------------------------------------------------
6.2 Air volume measurement. If the flow rate changes substantially
or nonuniformly during the sampling period, appreciable error in the
estimated air volume may result from using the average of the
presampling and postsampling flow rates. Greater air volume measurement
accuracy may be achieved by (1) equipping the sampler with a flow
controlling mechanism that maintains constant air flow during the
sampling period,* (2) using a calibrated, continuous flow rate recording
device to record the actual flow rate during the samping period and
integrating the flow rate over the period, or (3) any other means that
will accurately measure the total air volume sampled during the sampling
period. Use of a continuous flow recorder is recommended, particularly
if the sampler is not equipped with a constant flow controller.
6.3 Loss of volatiles. Volatile particles collected on the filter
may be lost during subsequent sampling or during shipment and/or storage
of the filter prior to the postsampling weighing.(5) Although such
losses are largely unavoidable, the filter should be reweighed as soon
after sampling as practical.
6.4 Artifact particulate matter. Artifact particulate matter can be
formed on the surface of alkaline glass fiber filters by oxidation of
acid gases in the sample air, resulting in a higher than true TSP
determination.(6 7) This effect usually occurs early in the sample
period and is a function of the filter pH and the presence of acid
gases. It is generally believed to account for only a small percentage
of the filter weight gain, but the effect may become more significant
where relatively small particulate weights are collected.
6.5 Humidity. Glass fiber filters are comparatively insensitive to
changes in relative humidity, but collected particulate matter can be
hygroscopic.(8) The moisture conditioning procedure minimizes but may
not completely eliminate error due to moisture.
6.6 Filter handling. Careful handling of the filter between the
presampling and postsampling weighings is necessary to avoid errors due
to loss of fibers or particles from the filter. A filter paper cartridge
or cassette used to protect the filter can minimize handling errors.
(See Reference 2, Section 2).
6.7 Nonsampled particulate matter. Particulate matter may be
deposited on the filter by wind during periods when the sampler is
inoperative. (9) It is recommended that errors from this source be
minimized by an automatic mechanical device that keeps the filter
covered during nonsampling periods, or by timely installation and
retrieval of filters to minimize the nonsampling periods prior to and
following operation.
6.8 Timing errors. Samplers are normally controlled by clock timers
set to start and stop the sampler at midnight. Errors in the nominal
1,440-min sampling period may result from a power interruption during
the sampling period or from a discrepancy between the start or stop time
recorded on the filter information record and the actual start or stop
time of the sampler. Such discrepancies may be caused by (1) poor
resolution of the timer set-points, (2) timer error due to power
interruption, (3) missetting of
[[Page 41]]
the timer, or (4) timer malfunction. In general, digital electronic
timers have much better set-point resolution than mechanical timers, but
require a battery backup system to maintain continuity of operation
after a power interruption. A continuous flow recorder or elapsed time
meter provides an indication of the sampler run-time, as well as
indication of any power interruption during the sampling period and is
therefore recommended.
6.9 Recirculation of sampler exhaust. Under stagnant wind
conditions, sampler exhaust air can be resampled. This effect does not
appear to affect the TSP measurement substantially, but may result in
increased carbon and copper in the collected sample. (10) This problem
can be reduced by ducting the exhaust air well away, preferably
downwind, from the sampler.
7.0 Apparatus.
(See References 1 and 2 for quality assurance information.)
Note: Samplers purchased prior to the effective date of this
amendment are not subject to specifications preceded by ([dagger]).
7.1 Filter. (Filters supplied by the Environmental Protection Agency
can be assumed to meet the following criteria. Additional specifications
are required if the sample is to be analyzed chemically.)
7.1.1 Size: 20.3 0.2 x 25.4 0.2 cm (nominal 8 x 10 in).
7.1.2 Nominal exposed area: 406.5 cm\2\ (63 in\2\).
7.1.3. Material: Glass fiber or other relatively inert,
nonhygroscopic material. (8)
7.1.4 Collection efficiency: 99 percent minimum as measured by the
DOP test (ASTM-2986) for particles of 0.3 [micro]m diameter.
7.1.5 Recommended pressure drop range: 42-54 mm Hg (5.6-7.2 kPa) at
a flow rate of 1.5 std m\3\/min through the nominal exposed area.
7.1.6 pH: 6 to 10. (11)
7.1.7 Integrity: 2.4 mg maximum weight loss. (11)
7.1.8 Pinholes: None.
7.1.9 Tear strength: 500 g minimum for 20 mm wide strip cut from
filter in weakest dimension. (See ASTM Test D828-60).
7.1.10 Brittleness: No cracks or material separations after single
lengthwise crease.
7.2 Sampler. The air sampler shall provide means for drawing the air
sample, via reduced pressure, through the filter at a uniform face
velocity.
7.2.1 The sampler shall have suitable means to:
a. Hold and seal the filter to the sampler housing.
b. Allow the filter to be changed conveniently.
c. Preclude leaks that would cause error in the measurement of the
air volume passing through the filter.
d. ([dagger]) Manually adjust the flow rate to accommodate
variations in filter pressure drop and site line voltage and altitude.
The adjustment may be accomplished by an automatic flow controller or by
a manual flow adjustment device. Any manual adjustment device must be
designed with positive detents or other means to avoid unintentional
changes in the setting.
---------------------------------------------------------------------------
([dagger]) See note at beginning of Section 7 of this appendix.
---------------------------------------------------------------------------
7.2.2 Minimum sample flow rate, heavily loaded filter: 1.1 m\3\/min
(39 ft\3\/min).[Dagger]
---------------------------------------------------------------------------
[Dagger] These specifications are in actual air volume units; to
convert to EPA standard air volume units, multiply the specifications by
(Pb/Pstd)(298/T) where Pb and T are the
barometric pressure in mm Hg (or kPa) and the temperature in K at the
sampler, and Pstd is 760 mm Hg (or 101 kPa).
---------------------------------------------------------------------------
7.2.3 Maximum sample flow rate, clean filter: 1.7 m\3\/min (60
ft\3\/min).[Dagger]
7.2.4 Blower Motor: The motor must be capable of continuous
operation for 24-hr periods.
7.3 Sampler shelter.
7.3.1 The sampler shelter shall:
a. Maintain the filter in a horizontal position at least 1 m above
the sampler supporting surface so that sample air is drawn downward
through the filter.
b. Be rectangular in shape with a gabled roof, similar to the design
shown in Figure 1.
c. Cover and protect the filter and sampler from precipitation and
other weather.
d. Discharge exhaust air at least 40 cm from the sample air inlet.
e. Be designed to minimize the collection of dust from the
supporting surface by incorporating a baffle between the exhaust outlet
and the supporting surface.
7.3.2 The sampler cover or roof shall overhang the sampler housing
somewhat, as shown in Figure 1, and shall be mounted so as to form an
air inlet gap between the cover and the sampler housing walls.
[dagger] This sample air inlet should be approximately
uniform on all sides of the sampler. [dagger] The area of the
sample air inlet must be sized to provide an effective particle capture
air velocity of between 20 and 35 cm/sec at the recommended operational
flow rate. The capture velocity is the sample air flow rate divided by
the inlet area measured in a horizontal plane at the lower edge of the
cover. [dagger] Ideally, the inlet area and operational flow
rate should be selected to obtain a capture air velocity of 25 2 cm/sec.
7.4 Flow rate measurement devices.
7.4.1 The sampler shall incorporate a flow rate measurement device
capable of indicating the total sampler flow rate. Two common types of
flow indicators covered in the calibration procedure are (1) an
electronic mass flowmeter and (2) an orifice or orifices
[[Page 42]]
located in the sample air stream together with a suitable pressure
indicator such as a manometer, or aneroid pressure gauge. A pressure
recorder may be used with an orifice to provide a continuous record of
the flow. Other types of flow indicators (including rotameters) having
comparable precision and accuracy are also acceptable.
7.4.2 [dagger] The flow rate measurement device must be capable of
being calibrated and read in units corresponding to a flow rate which is
readable to the nearest 0.02 std m\3\/min over the range 1.0 to 1.8 std
m\3\/min.
7.5 Thermometer, to indicate the approximate air temperature at the
flow rate measurement orifice, when temperature corrections are used.
7.5.1 Range: -40[deg] to + 50 [deg]C (223-323 K).
7.5.2 Resolution: 2 [deg]C (2 K).
7.6 Barometer, to indicate barometric pressure at the flow rate
measurement orifice, when pressure corrections are used.
7.6.1 Range: 500 to 800 mm Hg (66-106 kPa).
7.6.2 Resolution: 5 mm Hg (0.67 kPa).
7.7 Timing/control device.
7.7.1 The timing device must be capable of starting and stopping the
sampler to obtain an elapsed run-time of 24 hr 1
hr (1,440 60 min).
7.7.2 Accuracy of time setting: 30 min, or
better. (See Section 6.8).
7.8 Flow rate transfer standard, traceable to a primary standard.
(See Section 9.2.)
7.8.1 Approximate range: 1.0 to 1.8 m\3\/min.
7.8.2 Resolution: 0.02 m\3\/min.
7.8.3 Reproducibility: 2 percent (2 times
coefficient of variation) over normal ranges of ambient temperature and
pressure for the stated flow rate range. (See Reference 2, Section 2.)
7.8.4 Maximum pressure drop at 1.7 std m\3\/min; 50 cm H2
O (5 kPa).
7.8.5 The flow rate transfer standard must connect without leaks to
the inlet of the sampler and measure the flow rate of the total air
sample.
7.8.6 The flow rate transfer standard must include a means to vary
the sampler flow rate over the range of 1.0 to 1.8 m\3\/min (35-64
ft\3\/min) by introducing various levels of flow resistance between the
sampler and the transfer standard inlet.
7.8.7 The conventional type of flow transfer standard consists of:
An orifice unit with adapter that connects to the inlet of the sampler,
a manometer or other device to measure orifice pressure drop, a means to
vary the flow through the sampler unit, a thermometer to measure the
ambient temperature, and a barometer to measure ambient pressure. Two
such devices are shown in Figures 2a and 2b. Figure 2a shows multiple
fixed resistance plates, which necessitate disassembly of the unit each
time the flow resistance is changed. A preferable design, illustrated in
Figure 2b, has a variable flow restriction that can be adjusted
externally without disassembly of the unit. Use of a conventional,
orifice-type transfer standard is assumed in the calibration procedure
(Section 9). However, the use of other types of transfer standards
meeting the above specifications, such as the one shown in Figure 2c,
may be approved; see the note following Section 9.1.
7.9 Filter conditioning environment
7.9.1 Controlled temperature: between 15[deg] and 30 [deg]C with
less than 3 [deg]C variation during equilibration
period.
7.9.2 Controlled humidity: Less than 50 percent relative humidity,
constant within 5 percent.
7.10 Analytical balance.
7.10.1 Sensitivity: 0.1 mg.
7.10.2 Weighing chamber designed to accept an unfolded 20.3 x 25.4
cm (8 x 10 in) filter.
7.11 Area light source, similar to X-ray film viewer, to backlight
filters for visual inspection.
7.12 Numbering device, capable of printing identification numbers on
the filters before they are placed in the filter conditioning
environment, if not numbered by the supplier.
8.0 Procedure.
(See References 1 and 2 for quality assurance information.)
8.1 Number each filter, if not already numbered, near its edge with
a unique identification number.
8.2 Backlight each filter and inspect for pinholes, particles, and
other imperfections; filters with visible imperfections must not be
used.
8.3 Equilibrate each filter in the conditioning environment for at
least 24-hr.
8.4 Following equilibration, weigh each filter to the nearest
milligram and record this tare weight (Wi) with the filter
identification number.
8.5 Do not bend or fold the filter before collection of the sample.
8.6 Open the shelter and install a numbered, preweighed filter in
the sampler, following the sampler manufacturer's instructions. During
inclement weather, precautions must be taken while changing filters to
prevent damage to the clean filter and loss of sample from or damage to
the exposed filter. Filter cassettes that can be loaded and unloaded in
the laboratory may be used to minimize this problem (See Section 6.6).
8.7 Close the shelter and run the sampler for at least 5 min to
establish run-temperature conditions.
8.8 Record the flow indicator reading and, if needed, the barometric
pressure (P\3\3) and the ambient temperature
(T\3\3) see NOTE following step 8.12). Stop the sampler.
Determine the sampler flow rate (see Section 10.1); if it is outside the
acceptable range (1.1 to 1.7 m\3\/min [39-60 ft\3\/min]), use a
different filter, or adjust the sampler flow rate. Warning: Substantial
flow adjustments may affect the
[[Page 43]]
calibration of the orifice-type flow indicators and may necessitate
recalibration.
8.9 Record the sampler identification information (filter number,
site location or identification number, sample date, and starting time).
8.10 Set the timer to start and stop the sampler such that the
sampler runs 24-hrs, from midnight to midnight (local time).
8.11 As soon as practical following the sampling period, run the
sampler for at least 5 min to again establish run-temperature
conditions.
8.12 Record the flow indicator reading and, if needed, the
barometric pressure (P\3\3) and the ambient temperature
(T\3\3).
Note: No onsite pressure or temperature measurements are necessary
if the sampler flow indicator does not require pressure or temperature
corrections (e.g., a mass flowmeter) or if average barometric pressure
and seasonal average temperature for the site are incorporated into the
sampler calibration (see step 9.3.9). For individual pressure and
temperature corrections, the ambient pressure and temperature can be
obtained by onsite measurements or from a nearby weather station.
Barometric pressure readings obtained from airports must be station
pressure, not corrected to sea level, and may need to be corrected for
differences in elevation between the sampler site and the airport. For
samplers having flow recorders but not constant flow controllers, the
average temperature and pressure at the site during the sampling period
should be estimated from weather bureau or other available data.
8.13 Stop the sampler and carefully remove the filter, following the
sampler manufacturer's instructions. Touch only the outer edges of the
filter. See the precautions in step 8.6.
8.14 Fold the filter in half lengthwise so that only surfaces with
collected particulate matter are in contact and place it in the filter
holder (glassine envelope or manila folder).
8.15 Record the ending time or elapsed time on the filter
information record, either from the stop set-point time, from an elapsed
time indicator, or from a continuous flow record. The sample period must
be 1,440 60 min. for a valid sample.
8.16 Record on the filter information record any other factors, such
as meteorological conditions, construction activity, fires or dust
storms, etc., that might be pertinent to the measurement. If the sample
is known to be defective, void it at this time.
8.17 Equilibrate the exposed filter in the conditioning environment
for at least 24-hrs.
8.18 Immediately after equilibration, reweigh the filter to the
nearest milligram and record the gross weight with the filter
identification number. See Section 10 for TSP concentration
calculations.
9.0 Calibration.
9.1 Calibration of the high volume sampler's flow indicating or
control device is necessary to establish traceability of the field
measurement to a primary standard via a flow rate transfer standard.
Figure 3a illustrates the certification of the flow rate transfer
standard and Figure 3b illustrates its use in calibrating a sampler flow
indicator. Determination of the corrected flow rate from the sampler
flow indicator, illustrated in Figure 3c, is addressed in Section 10.1
Note: The following calibration procedure applies to a conventional
orifice-type flow transfer standard and an orifice-type flow indicator
in the sampler (the most common types). For samplers using a pressure
recorder having a square-root scale, 3 other acceptable calibration
procedures are provided in Reference 12. Other types of transfer
standards may be used if the manufacturer or user provides an
appropriately modified calibration procedure that has been approved by
EPA under Section 2.8 of appendix C to part 58 of this chapter.
9.2 Certification of the flow rate transfer standard.
9.2.1 Equipment required: Positive displacement standard volume
meter traceable to the National Bureau of Standards (such as a Roots
meter or equivalent), stop-watch, manometer, thermometer, and barometer.
9.2.2 Connect the flow rate transfer standard to the inlet of the
standard volume meter. Connect the manometer to measure the pressure at
the inlet of the standard volume meter. Connect the orifice manometer to
the pressure tap on the transfer standard. Connect a high-volume air
pump (such as a high-volume sampler blower) to the outlet side of the
standard volume meter. See Figure 3a.
9.2.3 Check for leaks by temporarily clamping both manometer lines
(to avoid fluid loss) and blocking the orifice with a large-diameter
rubber stopper, wide cellophane tape, or other suitable means. Start the
high-volume air pump and note any change in the standard volume meter
reading. The reading should remain constant. If the reading changes,
locate any leaks by listening for a whistling sound and/or retightening
all connections, making sure that all gaskets are properly installed.
9.2.4 After satisfactorily completing the leak check as described
above, unclamp both manometer lines and zero both manometers.
9.2.5 Achieve the appropriate flow rate through the system, either
by means of the variable flow resistance in the transfer standard or by
varying the voltage to the air pump. (Use of resistance plates as shown
in Figure 1a is discouraged because the above leak check must be
repeated each time a new resistance plate is installed.) At least five
[[Page 44]]
different but constant flow rates, evenly distributed, with at least
three in the specified flow rate interval (1.1 to 1.7 m\3\/min [39-60
ft\3\/min]), are required.
9.2.6 Measure and record the certification data on a form similar to
the one illustrated in Figure 4 according to the following steps.
9.2.7 Observe the barometric pressure and record as P1
(item 8 in Figure 4).
9.2.8 Read the ambient temperature in the vicinity of the standard
volume meter and record it as T1 (item 9 in Figure 4).
9.2.9 Start the blower motor, adjust the flow, and allow the system
to run for at least 1 min for a constant motor speed to be attained.
9.2.10 Observe the standard volume meter reading and simultaneously
start a stopwatch. Record the initial meter reading (Vi) in
column 1 of Figure 4.
9.2.11 Maintain this constant flow rate until at least 3 m\3\ of air
have passed through the standard volume meter. Record the standard
volume meter inlet pressure manometer reading as [Delta]P (column 5 in
Figure 4), and the orifice manometer reading as [Delta]H (column 7 in
Figure 4). Be sure to indicate the correct units of measurement.
9.2.12 After at least 3 m\3\ of air have passed through the system,
observe the standard volume meter reading while simultaneously stopping
the stopwatch. Record the final meter reading (Vf) in column
2 and the elapsed time (t) in column 3 of Figure 4.
9.2.13 Calculate the volume measured by the standard volume meter at
meter conditions of temperature and pressures as Vm =
Vf-Vi. Record in column 4 of Figure 4.
9.2.14 Correct this volume to standard volume (std m\3\) as follows:
[GRAPHIC] [TIFF OMITTED] TR31AU93.024
where:
Vstd = standard volume, std m\3\;
Vm = actual volume measured by the standard volume meter;
P1 = barometric pressure during calibration, mm Hg or kPa;
[Delta]P = differential pressure at inlet to volume meter, mm Hg or kPa;
Pstd = 760 mm Hg or 101 kPa;
Tstd = 298 K;
T1 = ambient temperature during calibration, K.
Calculate the standard flow rate (std m\3\/min) as follows:
[GRAPHIC] [TIFF OMITTED] TC08NO91.013
where:
Qstd = standard volumetric flow rate, std m\3\/min
t = elapsed time, minutes.
Record Qstd to the nearest 0.01 std m\3\/min in column 6
of Figure 4.
9.2.15 Repeat steps 9.2.9 through 9.2.14 for at least four
additional constant flow rates, evenly spaced over the approximate range
of 1.0 to 1.8 std m\3\/min (35-64 ft\3\/min).
9.2.16 For each flow, compute
[radic][Delta][Delta]H (P1/Pstd)(298/
T1)
(column 7a of Figure 4) and plot these value against Qstd as
shown in Figure 3a. Be sure to use consistent units (mm Hg or kPa) for
barometric pressure. Draw the orifice transfer standard certification
curve or calculate the linear least squares slope (m) and intercept (b)
of the certification curve:
[radic][Delta][Delta]H (P1/Pstd)(298/
T1)
= mQstd + b. See Figures 3 and 4. A certification graph
should be readable to 0.02 std m\3\/min.
9.2.17 Recalibrate the transfer standard annually or as required by
applicable quality control procedures. (See Reference 2.)
9.3 Calibration of sampler flow indicator.
Note: For samplers equipped with a flow controlling device, the flow
controller must be disabled to allow flow changes during calibration of
the sampler's flow indicator, or the alternate calibration of the flow
controller given in 9.4 may be used. For samplers using an orifice-type
flow indicator downstream of the motor, do not vary the flow rate by
adjusting the voltage or power supplied to the sampler.
9.3.1 A form similar to the one illustrated in Figure 5 should be
used to record the calibration data.
9.3.2 Connect the transfer standard to the inlet of the sampler.
Connect the orifice manometer to the orifice pressure tap, as
illustrated in Figure 3b. Make sure there are no leaks between the
orifice unit and the sampler.
9.3.3 Operate the sampler for at least 5 minutes to establish
thermal equilibrium prior to the calibration.
9.3.4 Measure and record the ambient temperature, T2, and
the barometric pressure, P2, during calibration.
9.3.5 Adjust the variable resistance or, if applicable, insert the
appropriate resistance plate (or no plate) to achieve the desired flow
rate.
9.3.6 Let the sampler run for at least 2 min to re-establish the
run-temperature conditions. Read and record the pressure drop across the
orifice ([Delta]H) and the sampler flow rate indication (I) in the
appropriate columns of Figure 5.
9.3.7 Calculate [radic][Delta][Delta]H(P2/
Pstd)(298/T2) and determine the flow rate at
standard conditions (Qstd) either graphically from the
certification curve or by calculating Qstd from the least
square slope and intercept of the transfer standard's transposed
certification curve:
[[Page 45]]
Qstd = 1/m [radic][Delta]H(P2/
Pstd)(298/T2)-b. Record the value of
Qstd on Figure 5.
9.3.8 Repeat steps 9.3.5, 9.3.6, and 9.3.7 for several additional
flow rates distributed over a range that includes 1.1 to 1.7 std m\3\/
min.
9.3.9 Determine the calibration curve by plotting values of the
appropriate expression involving I, selected from table 1, against
Qstd. The choice of expression from table 1 depends on the
flow rate measurement device used (see Section 7.4.1) and also on
whether the calibration curve is to incorporate geographic average
barometric pressure (Pa) and seasonal average temperature
(Ta) for the site to approximate actual pressure and
temperature. Where Pa and Ta can be determined for
a site for a seasonal period such that the actual barometric pressure
and temperature at the site do not vary by more than 60 mm Hg (8 kPa) from Pa or 15 [deg]C from Ta, respectively, then using
Pa and Ta avoids the need for subsequent pressure
and temperature calculation when the sampler is used. The geographic
average barometric pressure (Pa) may be estimated from an
altitude-pressure table or by making an (approximate) elevation
correction of -26 mm Hg (-3.46 kPa) for each 305 m (1,000 ft) above sea
level (760 mm Hg or 101 kPa). The seasonal average temperature
(Ta) may be estimated from weather station or other records.
Be sure to use consistent units (mm Hg or kPa) for barometric pressure.
9.3.10 Draw the sampler calibration curve or calculate the linear
least squares slope (m), intercept (b), and correlation coefficient of
the calibration curve: [Expression from table 1]= mQstd + b.
See Figures 3 and 5. Calibration curves should be readable to 0.02 std
m\3\/min.
9.3.11 For a sampler equipped with a flow controller, the flow
controlling mechanism should be re-enabled and set to a flow near the
lower flow limit to allow maximum control range. The sample flow rate
should be verified at this time with a clean filter installed. Then add
two or more filters to the sampler to see if the flow controller
maintains a constant flow; this is particularly important at high
altitudes where the range of the flow controller may be reduced.
9.4 Alternate calibration of flow-controlled samplers. A flow-
controlled sampler may be calibrated solely at its controlled flow rate,
provided that previous operating history of the sampler demonstrates
that the flow rate is stable and reliable. In this case, the flow
indicator may remain uncalibrated but should be used to indicate any
relative change between initial and final flows, and the sampler should
be recalibrated more often to minimize potential loss of samples because
of controller malfunction.
9.4.1 Set the flow controller for a flow near the lower limit of the
flow range to allow maximum control range.
9.4.2 Install a clean filter in the sampler and carry out steps
9.3.2, 9.3.3, 9.3.4, 9.3.6, and 9.3.7.
9.4.3 Following calibration, add one or two additional clean filters
to the sampler, reconnect the transfer standard, and operate the sampler
to verify that the controller maintains the same calibrated flow rate;
this is particularly important at high altitudes where the flow control
range may be reduced.
[[Page 46]]
10.0 Calculations of TSP Concentration.
10.1 Determine the average sampler flow rate during the sampling
period according to either 10.1.1 or 10.1.2 below.
10.1.1 For a sampler without a continuous flow recorder, determine
the appropriate expression to be used from table 2 corresponding to the
one from table 1 used in step 9.3.9. Using this appropriate expression,
determine Qstd for the initial flow rate from the sampler
calibration curve, either graphically or from the transposed regression
equation:
Qstd =
1/m ([Appropriate expression from table 2]-b)
Similarly, determine Qstd from the final flow reading, and
calculate the average flow Qstd as one-half the sum of the
initial and final flow rates.
[[Page 47]]
10.1.2 For a sampler with a continuous flow recorder, determine the
average flow rate device reading, I, for the period. Determine the
appropriate expression from table 2 corresponding to the one from table
1 used in step 9.3.9. Then using this expression and the average flow
rate reading, determine Qstd from the sampler calibration
curve, either graphically or from the transposed regression equation:
Qstd =
1/m ([Appropriate expression from table 2]-b)
If the trace shows substantial flow change during the sampling
period, greater accuracy may be achieved by dividing the sampling period
into intervals and calculating an average reading before determining
Qstd.
10.2 Calculate the total air volume sampled as:
V - Qstd x t
where:
V = total air volume sampled, in standard volume units, std m\3\/;
Qstd = average standard flow rate, std m\3\/min;
t = sampling time, min.
10.3 Calculate and report the particulate matter concentration as:
[GRAPHIC] [TIFF OMITTED] TR31AU93.025
where:
TSP = mass concentration of total suspended particulate matter,
[micro]g/std m\3\;
Wi = initial weight of clean filter, g;
Wf = final weight of exposed filter, g;
V = air volume sampled, converted to standard conditions, std m\3\,
10\6\ = conversion of g to [micro]g.
10.4 If desired, the actual particulate matter concentration (see
Section 2.2) can be calculated as follows:
(TSP)a = TSP (P3/Pstd)(298/
T3)
where:
(TSP)a = actual concentration at field conditions, [micro]g/
m\3\;
TSP = concentration at standard conditions, [micro]g/std m\3\;
P3 = average barometric pressure during sampling period, mm
Hg;
Pstd = 760 mn Hg (or 101 kPa);
T3 = average ambient temperature during sampling period, K.
11.0 References.
1. Quality Assurance Handbook for Air Pollution Measurement Systems,
Volume I, Principles. EPA-600/9-76-005, U.S. Environmental Protection
Agency, Research Triangle Park, NC 27711, 1976.
2. Quality Assurance Handbook for Air Pollution Measurement Systems,
Volume II, Ambient Air Specific Methods. EPA-600/4-77-027a, U.S.
Environmental Protection Agency, Research Triangle Park, NC 27711, 1977.
3. Wedding, J. B., A. R. McFarland, and J. E. Cernak. Large Particle
Collection Characteristics of Ambient Aerosol Samplers. Environ. Sci.
Technol. 11:387-390, 1977.
4. McKee, H. C., et al. Collaborative Testing of Methods to Measure
Air Pollutants, I. The High-Volume Method for Suspended Particulate
Matter. J. Air Poll. Cont. Assoc., 22 (342), 1972.
5. Clement, R. E., and F. W. Karasek. Sample Composition Changes in
Sampling and Analysis of Organic Compounds in Aerosols. The Intern. J.
Environ. Anal. Chem., 7:109, 1979.
6. Lee, R. E., Jr., and J. Wagman. A Sampling Anomaly in the
Determination of Atmospheric Sulfuric Concentration. Am. Ind. Hygiene
Assoc. J., 27:266, 1966.
7. Appel, B. R., et al. Interference Effects in Sampling Particulate
Nitrate in Ambient Air. Atmospheric Environment, 13:319, 1979.
8. Tierney, G. P., and W. D. Conner. Hygroscopic Effects on Weight
Determinations of Particulates Collected on Glass-Fiber Filters. Am.
Ind. Hygiene Assoc. J., 28:363, 1967.
9. Chahal, H. S., and D. J. Romano. High-Volume Sampling Effect of
Windborne Particulate Matter Deposited During Idle Periods. J. Air Poll.
Cont. Assoc., Vol. 26 (885), 1976.
10. Patterson, R. K. Aerosol Contamination from High-Volume Sampler
Exhaust. J. Air Poll. Cont. Assoc., Vol. 30 (169), 1980.
11. EPA Test Procedures for Determining pH and Integrity of High-
Volume Air Filters. QAD/M-80.01. Available from the Methods
Standardization Branch, Quality Assurance Division, Environmental
Monitoring Systems Laboratory (MD-77), U.S. Environmental Protection
Agency, Research Triangle Park, NC 27711, 1980.
12. Smith, F., P. S. Wohlschlegel, R. S. C. Rogers, and D. J.
Mulligan. Investigation of Flow Rate Calibration Procedures Associated
with the High-Volume Method for Determination of Suspended Particulates.
EPA-600/4-78-047, U.S. Environmental Protection Agency, Research
Triangle Park, NC, June 1978.
[[Page 48]]
[[Page 49]]
[[Page 50]]
[[Page 51]]
[[Page 52]]
[47 FR 54912, Dec. 6, 1982; 48 FR 17355, Apr. 22, 1983]
Sec. Appendix C to Part 50--Measurement Principle and Calibration
Procedure for the Measurement of Carbon Monoxide in the Atmosphere (Non-
Dispersive Infrared Photometry)
1.0 Applicability
1.1 This non-dispersive infrared photometry (NDIR) Federal Reference
Method (FRM) provides measurements of the concentration of carbon
monoxide (CO) in ambient air for determining compliance with the primary
and secondary National Ambient Air Quality Standards (NAAQS) for CO as
specified in Sec. 50.8 of this chapter. The method is applicable to
continuous sampling and measurement of ambient CO concentrations
suitable for determining 1-hour or longer average measurements. The
method may also provide measurements of shorter averaging times, subject
to specific analyzer performance limitations. Additional CO monitoring
quality assurance procedures and guidance
[[Page 53]]
are provided in part 58, appendix A, of this chapter and in reference 1
of this appendix C.
2.0 Measurement Principle
2.1 Measurements of CO in ambient air are based on automated
measurement of the absorption of infrared radiation by CO in an ambient
air sample drawn into an analyzer employing non-wavelength-dispersive,
infrared photometry (NDIR method). Infrared energy from a source in the
photometer is passed through a cell containing the air sample to be
analyzed, and the quantitative absorption of energy by CO in the sample
cell is measured by a suitable detector. The photometer is sensitized
specifically to CO by employing CO gas in a filter cell in the optical
path, which, when compared to a differential optical path without a CO
filter cell, limits the measured absorption to one or more of the
characteristic wavelengths at which CO strongly absorbs. However, to
meet measurement performance requirements, various optical filters,
reference cells, rotating gas filter cells, dual-beam configurations,
moisture traps, or other means may also be used to further enhance
sensitivity and stability of the photometer and to minimize potential
measurement interference from water vapor, carbon dioxide
(CO2), or other species. Also, various schemes may be used to
provide a suitable zero reference for the photometer, and optional
automatic compensation may be provided for the actual pressure and
temperature of the air sample in the measurement cell. The measured
infrared absorption, converted to a digital reading or an electrical
output signal, indicates the measured CO concentration.
2.2 The measurement system is calibrated by referencing the
analyzer's CO measurements to CO concentration standards traceable to a
National Institute of Standards and Technology (NIST) primary standard
for CO, as described in the associated calibration procedure specified
in section 4 of this reference method.
2.3 An analyzer implementing this measurement principle will be
considered a reference method only if it has been designated as a
reference method in accordance with part 53 of this chapter.
2.4 Sampling considerations. The use of a particle filter in the
sample inlet line of a CO FRM analyzer is optional and left to the
discretion of the user unless such a filter is specified or recommended
by the analyzer manufacturer in the analyzer's associated operation or
instruction manual.
3.0 Interferences
3.1 The NDIR measurement principle is potentially susceptible to
interference from water vapor and CO2, which have some
infrared absorption at wavelengths in common with CO and normally exist
in the atmosphere. Various instrumental techniques can be used to
effectively minimize these interferences.
4.0 Calibration Procedures
4.1 Principle. Either of two methods may be selected for dynamic
multipoint calibration of FRM CO analyzers, using test gases of
accurately known CO concentrations obtained from one or more compressed
gas cylinders certified as CO transfer standards:
4.1.1 Dilution method: A single certified standard cylinder of CO is
quantitatively diluted as necessary with zero air to obtain the various
calibration concentration standards needed.
4.1.2 Multiple-cylinder method: Multiple, individually certified
standard cylinders of CO are used for each of the various calibration
concentration standards needed.
4.1.3 Additional information on calibration may be found in Section
12 of reference 1.
4.2 Apparatus. The major components and typical configurations of
the calibration systems for the two calibration methods are shown in
Figures 1 and 2. Either system may be made up using common laboratory
components, or it may be a commercially manufactured system. In either
case, the principal components are as follows:
4.2.1 CO standard gas flow control and measurement devices (or a
combined device) capable of regulating and maintaining the standard gas
flow rate constant to within 2 percent and
measuring the gas flow rate accurate to within 2
percent, properly calibrated to a NIST-traceable standard.
4.2.2 For the dilution method (Figure 1), dilution air flow control
and measurement devices (or a combined device) capable of regulating and
maintaining the air flow rate constant to within 2
percent and measuring the air flow rate accurate to within 2 percent, properly calibrated to a NIST-traceable
standard.
4.2.3 Standard gas pressure regulator(s) for the standard CO
cylinder(s), suitable for use with a high-pressure CO gas cylinder and
having a non-reactive diaphragm and internal parts and a suitable
delivery pressure.
4.2.4 Mixing chamber for the dilution method of an inert material
and of proper design to provide thorough mixing of CO standard gas and
diluent air streams.
4.2.5 Output sampling manifold, constructed of an inert material and
of sufficient diameter to ensure an insignificant pressure drop at the
analyzer connection. The system must have a vent designed to ensure
nearly atmospheric pressure at the analyzer connection port and to
prevent ambient air from entering the manifold.
4.3 Reagents
4.3.1 CO gas concentration transfer standard(s) of CO in air,
containing an appropriate
[[Page 54]]
concentration of CO suitable for the selected operating range of the
analyzer under calibration and traceable to a NIST standard reference
material (SRM). If the CO analyzer has significant sensitivity to
CO2, the CO standard(s) should also contain 350 to 400 ppm
CO2 to replicate the typical CO2 concentration in
ambient air. However, if the zero air dilution ratio used for the
dilution method is not less than 100:1 and the zero air contains ambient
levels of CO2, then the CO standard may be contained in
nitrogen and need not contain CO2.
4.3.2 For the dilution method, clean zero air, free of contaminants
that could cause a detectable response on or a change in sensitivity of
the CO analyzer. The zero air should contain <0.1 ppm CO.
4.4 Procedure Using the Dilution Method
4.4.1 Assemble or obtain a suitable dynamic dilution calibration
system such as the one shown schematically in Figure 1. Generally, all
calibration gases including zero air must be introduced into the sample
inlet of the analyzer. However, if the analyzer has special, approved
zero and span inlets and automatic valves to specifically allow
introduction of calibration standards at near atmospheric pressure, such
inlets may be used for calibration in lieu of the sample inlet. For
specific operating instructions, refer to the manufacturer's manual.
4.4.2 Ensure that there are no leaks in the calibration system and
that all flowmeters are properly and accurately calibrated, under the
conditions of use, if appropriate, against a reliable volume or flow
rate standard such as a soap-bubble meter or wet-test meter traceable to
a NIST standard. All volumetric flow rates should be corrected to the
same temperature and pressure such as 298.15 K (25 [deg]C) and 760 mm Hg
(101 kPa), using a correction formula such as the following:
[GRAPHIC] [TIFF OMITTED] TR31AU11.001
Where:
Fc = corrected flow rate (L/min at 25 [deg]C and 760 mm Hg),
Fm = measured flow rate (at temperature Tm and pressure Pm),
Pm = measured pressure in mm Hg (absolute), and
Tm = measured temperature in degrees Celsius.
4.4.3 Select the operating range of the CO analyzer to be
calibrated. Connect the measurement signal output of the analyzer to an
appropriate readout instrument to allow the analyzer's measurement
output to be continuously monitored during the calibration. Where
possible, this readout instrument should be the same one used to record
routine monitoring data, or, at least, an instrument that is as closely
representative of that system as feasible.
4.4.4 Connect the inlet of the CO analyzer to the output-sampling
manifold of the calibration system.
4.4.5 Adjust the calibration system to deliver zero air to the
output manifold. The total air flow must exceed the total demand of the
analyzer(s) connected to the output manifold to ensure that no ambient
air is pulled into the manifold vent. Allow the analyzer to sample zero
air until a stable response is obtained. After the response has
stabilized, adjust the analyzer zero reading.
4.4.6 Adjust the zero air flow rate and the CO gas flow rate from
the standard CO cylinder to provide a diluted CO concentration of
approximately 80 percent of the measurement upper range limit (URL) of
the operating range of the analyzer. The total air flow rate must exceed
the total demand of the analyzer(s) connected to the output manifold to
ensure that no ambient air is pulled into the manifold vent. The exact
CO concentration is calculated from:
[GRAPHIC] [TIFF OMITTED] TR31AU11.002
Where:
[CO]OUT = diluted CO concentration at the output manifold (ppm),
[CO]STD = concentration of the undiluted CO standard (ppm),
[[Page 55]]
FCO = flow rate of the CO standard (L/min), and
FD = flow rate of the dilution air (L/min).
Sample this CO concentration until a stable response is obtained. Adjust
the analyzer span control to obtain the desired analyzer response
reading equivalent to the calculated standard concentration. If
substantial adjustment of the analyzer span control is required, it may
be necessary to recheck the zero and span adjustments by repeating steps
4.4.5 and 4.4.6. Record the CO concentration and the analyzer's final
response.
4.4.7 Generate several additional concentrations (at least three
evenly spaced points across the remaining scale are suggested to verify
linearity) by decreasing FCO or increasing FD. Be sure the total flow
exceeds the analyzer's total flow demand. For each concentration
generated, calculate the exact CO concentration using equation (2).
Record the concentration and the analyzer's stable response for each
concentration. Plot the analyzer responses (vertical or y-axis) versus
the corresponding CO concentrations (horizontal or x-axis). Calculate
the linear regression slope and intercept of the calibration curve and
verify that no point deviates from this line by more than 2 percent of
the highest concentration tested.
4.5 Procedure Using the Multiple-Cylinder Method. Use the procedure
for the dilution method with the following changes:
4.5.1 Use a multi-cylinder, dynamic calibration system such as the
typical one shown in Figure 2.
4.5.2 The flowmeter need not be accurately calibrated, provided the
flow in the output manifold can be verified to exceed the analyzer's
flow demand.
4.5.3 The various CO calibration concentrations required in Steps
4.4.5, 4.4.6, and 4.4.7 are obtained without dilution by selecting zero
air or the appropriate certified standard cylinder.
4.6 Frequency of Calibration. The frequency of calibration, as well
as the number of points necessary to establish the calibration curve and
the frequency of other performance checking, will vary by analyzer.
However, the minimum frequency, acceptance criteria, and subsequent
actions are specified in reference 1, appendix D, ``Measurement Quality
Objectives and Validation Template for CO'' (page 5 of 30). The user's
quality control program should provide guidelines for initial
establishment of these variables and for subsequent alteration as
operational experience is accumulated. Manufacturers of CO analyzers
should include in their instruction/operation manuals information and
guidance as to these variables and on other matters of operation,
calibration, routine maintenance, and quality control.
5.0 Reference
1. QA Handbook for Air Pollution Measurement Systems--Volume II.
Ambient Air Quality Monitoring Program. U.S. EPA. EPA-454/B-08-003
(2008).
[GRAPHIC] [TIFF OMITTED] TR31AU11.003
[[Page 56]]
[GRAPHIC] [TIFF OMITTED] TR31AU11.004
[76 FR 54323, Aug. 31, 2011]
Sec. Appendix D to Part 50--Reference Measurement Principle and
Calibration Procedure for the Measurement of Ozone in the Atmosphere
(Chemiluminescence Method)
1.0 Applicability.
1.1 This chemiluminescence method provides reference measurements of
the concentration of ozone (O3) in ambient air for
determining compliance with the national primary and secondary ambient
air quality standards for O3 as specified in 40 CFR part 50.
This automated method is applicable to the measurement of ambient
O3 concentrations using continuous (real-time) sampling and
analysis. Additional quality assurance procedures and guidance are
provided in 40 CFR part 58, appendix A, and in Reference 14.
2.0 Measurement Principle.
2.1 This reference method is based on continuous automated
measurement of the intensity of the characteristic chemiluminescence
released by the gas phase reaction of O3 in sampled air with
either ethylene (C2H4) or nitric oxide (NO) gas.
An ambient air sample stream and a specific flowing concentration of
either C2H4 (ET-CL method) or NO (NO-CL method)
are mixed in a measurement cell, where the resulting chemiluminescence
is quantitatively measured by a sensitive photo-detector. References 8-
11 describe the chemiluminescence measurement principle.
2.2 The measurement system is calibrated by referencing the
instrumental chemiluminescence measurements to certified O3
standard concentrations generated in a dynamic flow system and assayed
by photometry to be traceable to a National Institute of Standards and
Technology (NIST) standard reference photometer for O3 (see
Section 4, Calibration Procedure, below).
2.3 An analyzer implementing this measurement principle is shown
schematically in Figure 1. Designs implementing this measurement
principle must include: an appropriately designed mixing and measurement
cell; a suitable quantitative photometric measurement system with
adequate sensitivity and wavelength specificity for O3; a
pump, flow control, and sample conditioning system for sampling the
ambient air and moving it into and through the measurement cell; a
sample air dryer as necessary to meet the water vapor interference limit
requirement specified in subpart B of part 53 of this chapter; a means
to supply, meter, and mix a constant, flowing stream of either
C2H4 or NO gas of fixed concentration with the
sample air flow in the measurement cell; suitable electronic control and
measurement processing capability; and other associated apparatus as may
be necessary. The analyzer must be designed and constructed to provide
accurate, repeatable, and continuous measurements of O3
concentrations in ambient air, with measurement performance that meets
the requirements specified in subpart B of part 53 of this chapter.
[[Page 57]]
2.4 An analyzer implementing this measurement principle and
calibration procedure will be considered a federal reference method
(FRM) only if it has been designated as a reference method in accordance
with part 53 of this chapter.
2.5 Sampling considerations. The use of a particle filter on the
sample inlet line of a chemiluminescence O3 FRM analyzer is
required to prevent buildup of particulate matter in the measurement
cell and inlet components. This filter must be changed weekly (or at
least often as specified in the manufacturer's operation/instruction
manual), and the sample inlet system used with the analyzer must be kept
clean, to avoid loss of O3 in the O3 sample air
prior to the concentration measurement.
3.0 Interferences.
3.1 Except as described in 3.2 below, the chemiluminescence
measurement system is inherently free of significant interferences from
other pollutant substances that may be present in ambient air.
3.2 A small sensitivity to variations in the humidity of the sample
air is minimized by a sample air dryer. Potential loss of O3
in the inlet air filter and in the air sample handling components of the
analyzer and associated exterior air sampling components due to buildup
of airborne particulate matter is minimized by filter replacement and
cleaning of the other inlet components.
4.0 Calibration Procedure.
4.1 Principle. The calibration procedure is based on the photometric
assay of O3 concentrations in a dynamic flow system. The
concentration of O3 in an absorption cell is determined from
a measurement of the amount of 254 nm light absorbed by the sample. This
determination requires knowledge of (1) the absorption coefficient
([alpha]) of O3 at 254 nm, (2) the optical path length (l)
through the sample, (3) the transmittance of the sample at a nominal
wavelength of 254 nm, and (4) the temperature (T) and pressure (P) of
the sample. The transmittance is defined as the ratio I/I0,
where I is the intensity of light which passes through the cell and is
sensed by the detector when the cell contains an O3 sample,
and I0 is the intensity of light which passes through the
cell and is sensed by the detector when the cell contains zero air. It
is assumed that all conditions of the system, except for the contents of
the absorption cell, are identical during measurement of I and
I0. The quantities defined above are related by the Beer-
Lambert absorption law,
[GRAPHIC] [TIFF OMITTED] TR26OC15.002
Where:
[alpha] = absorption coefficient of O3 at 254 nm = 308 4 atm-1 cm-1 at 0 [deg]C and 760 torr,\1, 2,
3, 4, 5, 6, 7\
c = O3 concentration in atmospheres, and
l = optical path length in cm.
A stable O3 generator is used to produce O3
concentrations over the required calibration concentration range. Each
O3 concentration is determined from the measurement of the
transmittance (I/I0) of the sample at 254 nm with a
photometer of path length l and calculated from the equation,
[GRAPHIC] [TIFF OMITTED] TR26OC15.003
The calculated O3 concentrations must be corrected for
O3 losses, which may occur in the photometer, and for the
temperature and pressure of the sample.
4.2 Applicability. This procedure is applicable to the calibration
of ambient air O3 analyzers, either directly or by means of a
transfer standard certified by this procedure. Transfer standards must
meet the requirements and specifications set forth in Reference 12.
[[Page 58]]
4.3 Apparatus. A complete UV calibration system consists of an
O3 generator, an output port or manifold, a photometer, an
appropriate source of zero air, and other components as necessary. The
configuration must provide a stable O3 concentration at the
system output and allow the photometer to accurately assay the output
concentration to the precision specified for the photometer (4.3.1).
Figure 2 shows a commonly used configuration and serves to illustrate
the calibration procedure, which follows. Other configurations may
require appropriate variations in the procedural steps. All connections
between components in the calibration system downstream of the
O3 generator must be of glass, Teflon, or other relatively
inert materials. Additional information regarding the assembly of a UV
photometric calibration apparatus is given in Reference 13. For
certification of transfer standards which provide their own source of
O3, the transfer standard may replace the O3
generator and possibly other components shown in Figure 2; see Reference
12 for guidance.
4.3.1 UV photometer. The photometer consists of a low-pressure
mercury discharge lamp, (optional) collimation optics, an absorption
cell, a detector, and signal-processing electronics, as illustrated in
Figure 2. It must be capable of measuring the transmittance, I/
I0, at a wavelength of 254 nm with sufficient precision such
that the standard deviation of the concentration measurements does not
exceed the greater of 0.005 ppm or 3% of the concentration. Because the
low-pressure mercury lamp radiates at several wavelengths, the
photometer must incorporate suitable means to assure that no
O3 is generated in the cell by the lamp, and that at least
99.5% of the radiation sensed by the detector is 254 nm radiation. (This
can be readily achieved by prudent selection of optical filter and
detector response characteristics.) The length of the light path through
the absorption cell must be known with an accuracy of at least 99.5%. In
addition, the cell and associated plumbing must be designed to minimize
loss of O3 from contact with cell walls and gas handling
components. See Reference 13 for additional information.
4.3.2 Air flow controllers. Air flow controllers are devices capable
of regulating air flows as necessary to meet the output stability and
photometer precision requirements.
4.3.3 Ozone generator. The ozone generator used must be capable of
generating stable levels of O3 over the required
concentration range.
4.3.4 Output manifold. The output manifold must be constructed of
glass, Teflon, or other relatively inert material, and should be of
sufficient diameter to insure a negligible pressure drop at the
photometer connection and other output ports. The system must have a
vent designed to insure atmospheric pressure in the manifold and to
prevent ambient air from entering the manifold.
4.3.5 Two-way valve. A manual or automatic two-way valve, or other
means is used to switch the photometer flow between zero air and the
O3 concentration.
4.3.6 Temperature indicator. A device to indicate temperature must
be used that is accurate to 1 [deg]C.
4.3.7 Barometer or pressure indicator. A device to indicate
barometric pressure must be used that is accurate to 2 torr.
4.4 Reagents.
4.4.1 Zero air. The zero air must be free of contaminants which
would cause a detectable response from the O3 analyzer, and
it must be free of NO, C2H4, and other species
which react with O3. A procedure for generating suitable zero
air is given in Reference 13. As shown in Figure 2, the zero air
supplied to the photometer cell for the I0 reference
measurement must be derived from the same source as the zero air used
for generation of the O3 concentration to be assayed (I
measurement). When using the photometer to certify a transfer standard
having its own source of O3, see Reference 12 for guidance on
meeting this requirement.
4.5 Procedure.
4.5.1 General operation. The calibration photometer must be
dedicated exclusively to use as a calibration standard. It must always
be used with clean, filtered calibration gases, and never used for
ambient air sampling. A number of advantages are realized by locating
the calibration photometer in a clean laboratory where it can be
stationary, protected from the physical shock of transportation,
operated by a responsible analyst, and used as a common standard for all
field calibrations via transfer standards.
4.5.2 Preparation. Proper operation of the photometer is of critical
importance to the accuracy of this procedure. Upon initial operation of
the photometer, the following steps must be carried out with all
quantitative results or indications recorded in a chronological record,
either in tabular form or plotted on a graphical chart. As the
performance and stability record of the photometer is established, the
frequency of these steps may be reduced to be consistent with the
documented stability of the photometer and the guidance provided in
Reference 12.
4.5.2.1 Instruction manual. Carry out all set up and adjustment
procedures or checks as described in the operation or instruction manual
associated with the photometer.
4.5.2.2 System check. Check the photometer system for integrity,
leaks, cleanliness, proper flow rates, etc. Service or replace filters
and zero air scrubbers or other consumable materials, as necessary.
[[Page 59]]
4.5.2.3 Linearity. Verify that the photometer manufacturer has
adequately established that the linearity error of the photometer is
less than 3%, or test the linearity by dilution as follows: Generate and
assay an O3 concentration near the upper range limit of the
system or appropriate calibration scale for the instrument, then
accurately dilute that concentration with zero air and re-assay it.
Repeat at several different dilution ratios. Compare the assay of the
original concentration with the assay of the diluted concentration
divided by the dilution ratio, as follows
[GRAPHIC] [TIFF OMITTED] TR26OC15.004
Where:
E = linearity error, percent
A1 = assay of the original concentration
A2 = assay of the diluted concentration
R = dilution ratio = flow of original concentration divided by the total
flow
The linearity error must be less than 5%. Since the accuracy of the
measured flow-rates will affect the linearity error as measured this
way, the test is not necessarily conclusive. Additional information on
verifying linearity is contained in Reference 13.
4.5.2.4 Inter-comparison. The photometer must be inter-compared
annually, either directly or via transfer standards, with a NIST
standard reference photometer (SRP) or calibration photometers used by
other agencies or laboratories.
4.5.2.5 Ozone losses. Some portion of the O3 may be lost
upon contact with the photometer cell walls and gas handling components.
The magnitude of this loss must be determined and used to correct the
calculated O3 concentration. This loss must not exceed 5%.
Some guidelines for quantitatively determining this loss are discussed
in Reference 13.
4.5.3 Assay of O3 concentrations. The operator must carry
out the following steps to properly assay O3 concentrations.
4.5.3.1 Allow the photometer system to warm up and stabilize.
4.5.3.2 Verify that the flow rate through the photometer absorption
cell, F, allows the cell to be flushed in a reasonably short period of
time (2 liter/min is a typical flow). The precision of the measurements
is inversely related to the time required for flushing, since the
photometer drift error increases with time.
4.5.3.3 Ensure that the flow rate into the output manifold is at
least 1 liter/min greater than the total flow rate required by the
photometer and any other flow demand connected to the manifold.
4.5.3.4 Ensure that the flow rate of zero air, Fz, is at least 1
liter/min greater than the flow rate required by the photometer.
4.5.3.5 With zero air flowing in the output manifold, actuate the
two-way valve to allow the photometer to sample first the manifold zero
air, then Fz. The two photometer readings must be equal (I =
I0).
Note: In some commercially available photometers, the operation of
the two-way valve and various other operations in section 4.5.3 may be
carried out automatically by the photometer.
4.5.3.6 Adjust the O3 generator to produce an
O3 concentration as needed.
4.5.3.7 Actuate the two-way valve to allow the photometer to sample
zero air until the absorption cell is thoroughly flushed and record the
stable measured value of Io.
4.5.3.8 Actuate the two-way valve to allow the photometer to sample
the O3 concentration until the absorption cell is thoroughly
flushed and record the stable measured value of I.
4.5.3.9 Record the temperature and pressure of the sample in the
photometer absorption cell. (See Reference 13 for guidance.)
4.5.3.10 Calculate the O3 concentration from equation 4.
An average of several determinations will provide better precision.
[GRAPHIC] [TIFF OMITTED] TR26OC15.005
Where:
[O3]OUT = O3 concentration, ppm
[alpha] = absorption coefficient of O3 at 254 nm = 308 atm-1
cm-1 at 0 [deg]C and 760 torr
l = optical path length, cm
T = sample temperature, K
P = sample pressure, torr
L = correction factor for O3 losses from 4.5.2.5 = (1-
fraction of O3 lost).
[[Page 60]]
Note: Some commercial photometers may automatically evaluate all or
part of equation 4. It is the operator's responsibility to verify that
all of the information required for equation 4 is obtained, either
automatically by the photometer or manually. For ``automatic''
photometers which evaluate the first term of equation 4 based on a
linear approximation, a manual correction may be required, particularly
at higher O3 levels. See the photometer instruction manual
and Reference 13 for guidance.
4.5.3.11 Obtain additional O3 concentration standards as
necessary by repeating steps 4.5.3.6 to 4.5.3.10 or by Option 1.
4.5.4 Certification of transfer standards. A transfer standard is
certified by relating the output of the transfer standard to one or more
O3 calibration standards as determined according to section
4.5.3. The exact procedure varies depending on the nature and design of
the transfer standard. Consult Reference 12 for guidance.
4.5.5 Calibration of ozone analyzers. Ozone analyzers must be
calibrated as follows, using O3 standards obtained directly
according to section 4.5.3 or by means of a certified transfer standard.
4.5.5.1 Allow sufficient time for the O3 analyzer and the
photometer or transfer standard to warm-up and stabilize.
4.5.5.2 Allow the O3 analyzer to sample zero air until a
stable response is obtained and then adjust the O3 analyzer's
zero control. Offsetting the analyzer's zero adjustment to +5% of scale
is recommended to facilitate observing negative zero drift (if any).
Record the stable zero air response as ``Z''.
4.5.5.3 Generate an O3 concentration standard of
approximately 80% of the desired upper range limit (URL) of the
O3 analyzer. Allow the O3 analyzer to sample this
O3 concentration standard until a stable response is
obtained.
4.5.5.4 Adjust the O3 analyzer's span control to obtain
the desired response equivalent to the calculated standard
concentration. Record the O3 concentration and the
corresponding analyzer response. If substantial adjustment of the span
control is necessary, recheck the zero and span adjustments by repeating
steps 4.5.5.2 to 4.5.5.4.
4.5.5.5 Generate additional O3 concentration standards (a
minimum of 5 are recommended) over the calibration scale of the
O3 analyzer by adjusting the O3 source or by
Option 1. For each O3 concentration standard, record the
O3 concentration and the corresponding analyzer response.
4.5.5.6 Plot the O3 analyzer responses (vertical or Y-
axis) versus the corresponding O3 standard concentrations
(horizontal or X-axis). Compute the linear regression slope and
intercept and plot the regression line to verify that no point deviates
from this line by more than 2 percent of the maximum concentration
tested.
4.5.5.7 Option 1: The various O3 concentrations required
in steps 4.5.3.11 and 4.5.5.5 may be obtained by dilution of the
O3 concentration generated in steps 4.5.3.6 and 4.5.5.3. With
this option, accurate flow measurements are required. The dynamic
calibration system may be modified as shown in Figure 3 to allow for
dilution air to be metered in downstream of the O3 generator.
A mixing chamber between the O3 generator and the output
manifold is also required. The flow rate through the O3
generator (Fo) and the dilution air flow rate (FD) are measured with a
flow or volume standard that is traceable to a NIST flow or volume
calibration standard. Each O3 concentration generated by
dilution is calculated from:
[GRAPHIC] [TIFF OMITTED] TR26OC15.006
Where:
[O3][min]OUT = diluted O3
concentration, ppm
FO = flow rate through the O3 generator, liter/min
FD = diluent air flow rate, liter/min
Note: Additional information on calibration and pollutant standards
is provided in Section 12 of Reference 14.
5.0 Frequency of Calibration.
5.1 The frequency of calibration, as well as the number of points
necessary to establish the calibration curve, and the frequency of other
performance checking will vary by analyzer; however, the minimum
frequency, acceptance criteria, and subsequent actions are specified in
Appendix D of Reference 14: Measurement Quality Objectives and
Validation Templates. The user's quality control program shall provide
guidelines for initial establishment of these variables and for
subsequent alteration as operational experience is accumulated.
Manufacturers of analyzers should include in their instruction/operation
manuals information and guidance as to these variables and on other
matters of operation, calibration, routine maintenance, and quality
control.
6.0 References.
1. E.C.Y. Inn and Y. Tanaka, ``Absorption coefficient of Ozone in the
Ultraviolet and Visible Regions'', J. Opt. Soc. Am., 43, 870
(1953).
[[Page 61]]
2. A. G. Hearn, ``Absorption of Ozone in the Ultraviolet and Visible
Regions of the Spectrum'', Proc. Phys. Soc. (London), 78, 932
(1961).
3. W. B. DeMore and O. Raper, ``Hartley Band Extinction Coefficients of
Ozone in the Gas Phase and in Liquid Nitrogen, Carbon
Monoxide, and Argon'', J. Phys. Chem., 68, 412 (1964).
4. M. Griggs, ``Absorption Coefficients of Ozone in the Ultraviolet and
Visible Regions'', J. Chem. Phys., 49, 857 (1968).
5. K. H. Becker, U. Schurath, and H. Seitz, ``Ozone Olefin Reactions in
the Gas Phase. 1. Rate Constants and Activation Energies'',
Int'l Jour. of Chem. Kinetics, VI, 725 (1974).
6. M. A. A. Clyne and J. A. Coxom, ``Kinetic Studies of Oxy-halogen
Radical Systems'', Proc. Roy. Soc., A303, 207 (1968).
7. J. W. Simons, R. J. Paur, H. A. Webster, and E. J. Bair, ``Ozone
Ultraviolet Photolysis. VI. The Ultraviolet Spectrum'', J.
Chem. Phys., 59, 1203 (1973).
8. Ollison, W.M.; Crow, W.; Spicer, C.W. ``Field testing of new-
technology ambient air ozone monitors.'' J. Air Waste Manage.
Assoc., 63 (7), 855-863 (2013).
9. Parrish, D.D.; Fehsenfeld, F.C. ``Methods for gas-phase measurements
of ozone, ozone precursors and aerosol precursors.'' Atmos.
Environ., 34 (12-14), 1921-1957(2000).
10. Ridley, B.A.; Grahek, F.E.; Walega, J.G. ``A small, high-
sensitivity, medium-response ozone detector suitable for
measurements from light aircraft.'' J. Atmos. Oceanic
Technol., 9 (2), 142-148(1992).
11. Boylan, P., Helmig, D., and Park, J.H. ``Characterization and
mitigation of water vapor effects in the measurement of ozone
by chemiluminescence with nitric oxide.'' Atmos. Meas. Tech.
7, 1231-1244 (2014).
12. Transfer Standards for Calibration of Ambient Air Monitoring
Analyzers for Ozone, EPA publication number EPA-454/B-13-004,
October 2013. EPA, Office of Air Quality Planning and
Standards, Research Triangle Park, NC 27711. [Available at
www.epa.gov/ttnamti1/files/ambient/qaqc/
OzoneTransferStandardGuidance.pdf.]
13. Technical Assistance Document for the Calibration of Ambient Ozone
Monitors, EPA publication number EPA-600/4-79-057, September,
1979. [Available at www.epa.gov/ttnamti1/files/ambient/
criteria/4-79-057.pdf.]
14. QA Handbook for Air Pollution Measurement Systems--Volume II.
Ambient Air Quality Monitoring Program. EPA-454/B-13-003, May
2013. [Available at http://www.epa.gov/ttnamti1/files/ambient/
pm25/qa/QA-Handbook-Vol-II.pdf.]
[[Page 62]]
[GRAPHIC] [TIFF OMITTED] TR26OC15.007
[[Page 63]]
[GRAPHIC] [TIFF OMITTED] TR26OC15.008
[[Page 64]]
[GRAPHIC] [TIFF OMITTED] TR26OC15.009
[80 FR 65453, Oct. 26, 2015]
Sec. Appendix E to Part 50 [Reserved]
Sec. Appendix F to Part 50--Measurement Principle and Calibration
Procedure for the Measurement of Nitrogen Dioxide in the Atmosphere (Gas
Phase Chemiluminescence)
Principle and Applicability
1. Atmospheric concentrations of nitrogen dioxide (NO2)
are measured indirectly by photometrically measuring the light
intensity, at wavelengths greater than 600 nanometers, resulting from
the chemiluminescent reaction of nitric oxide (NO) with ozone
(O3). (1,2,3) NO2 is first quantitatively reduced
to NO(4,5,6) by means of a converter. NO, which commonly exists in
ambient air together with NO2, passes through the converter
unchanged causing a resultant total NOX concentration equal
to NO + NO2. A sample of the input air is also measured
without having passed through the converted. This latter NO measurement
is subtracted from the former measurement (NO + NO2) to yield
the final NO2 measurement. The NO and NO + NO2
measurements may be made concurrently with dual systems, or cyclically
with the same system provided the cycle time does not exceed 1 minute.
2. Sampling considerations.
2.1 Chemiluminescence NO/NOX/NO2 analyzers
will respond to other nitrogen containing compounds, such as
peroxyacetyl nitrate (PAN), which might be reduced to NO in the thermal
converter. (7) Atmospheric concentrations of these potential
interferences are generally low relative to NO2 and valid
NO2 measurements may be obtained. In certain geographical
areas, where the concentration of these potential interferences is known
or suspected to be high relative to NO2, the use of an
equivalent method for the measurement of NO2 is recommended.
2.2 The use of integrating flasks on the sample inlet line of
chemiluminescence NO/
[[Page 65]]
NOX/NO2 analyzers is optional and left to
couraged. The sample residence time between the sampling point and the
analyzer should be kept to a minimum to avoid erroneous NO2
measurements resulting from the reaction of ambient levels of NO and
O3 in the sampling system.
2.3 The use of particulate filters on the sample inlet line of
chemiluminescence NO/NOX/NO2 analyzers is optional
and left to the discretion of the user or the manufacturer.
Use of the filter should depend on the analyzer's susceptibility to
interference, malfunction, or damage due to particulates. Users are
cautioned that particulate matter concentrated on a filter may cause
erroneous NO2 measurements and therefore filters should be
changed frequently.
3. An analyzer based on this principle will be considered a
reference method only if it has been designated as a reference method in
accordance with part 53 of this chapter.
Calibration
1. Alternative A--Gas phase titration (GPT) of an NO standard with
O3.
Major equipment required: Stable O3 generator.
Chemiluminescence NO/NOX/NO2 analyzer with strip
chart recorder(s). NO concentration standard.
1.1 Principle. This calibration technique is based upon the rapid
gas phase reaction between NO and O3 to produce
stoichiometric quantities of NO2 in accordance with the
following equation: (8)
[GRAPHIC] [TIFF OMITTED] TC08NO91.075
The quantitative nature of this reaction is such that when the NO
concentration is known, the concentration of NO2 can be
determined. Ozone is added to excess NO in a dynamic calibration system,
and the NO channel of the chemiluminescence NO/NOX/
NO2 analyzer is used as an indicator of changes in NO
concentration. Upon the addition of O3, the decrease in NO
concentration observed on the calibrated NO channel is equivalent to the
concentration of NO2 produced. The amount of NO2
generated may be varied by adding variable amounts of O3 from
a stable uncalibrated O3 generator. (9)
1.2 Apparatus. Figure 1, a schematic of a typical GPT apparatus,
shows the suggested configuration of the components listed below. All
connections between components in the calibration system downstream from
the O3 generator should be of glass, Teflon [supreg], or
other non-reactive material.
1.2.1 Air flow controllers. Devices capable of maintaining constant
air flows within 2% of the required flowrate.
1.2.2 NO flow controller. A device capable of maintaining constant
NO flows within 2% of the required flowrate.
Component parts in contact with the NO should be of a non-reactive
material.
1.2.3 Air flowmeters. Calibrated flowmeters capable of measuring and
monitoring air flowrates with an accuracy of 2% of
the measured flowrate.
1.2.4 NO flowmeter. A calibrated flowmeter capable of measuring and
monitoring NO flowrates with an accuracy of 2% of
the measured flowrate. (Rotameters have been reported to operate
unreliably when measuring low NO flows and are not recommended.)
1.2.5 Pressure regulator for standard NO cylinder. This regulator
must have a nonreactive diaphragm and internal parts and a suitable
delivery pressure.
1.2.6 Ozone generator. The generator must be capable of generating
sufficient and stable levels of O3 for reaction with NO to
generate NO2 concentrations in the range required. Ozone
generators of the electric discharge type may produce NO and
NO2 and are not recommended.
1.2.7 Valve. A valve may be used as shown in Figure 1 to divert the
NO flow when zero air is required at the manifold. The valve should be
constructed of glass, Teflon [supreg], or other nonreactive material.
1.2.8 Reaction chamber. A chamber, constructed of glass, Teflon
[supreg], or other nonreactive material, for the quantitative reaction
of O3 with excess NO. The chamber should be of sufficient
volume (VRC) such that the residence time (tR) meets the
requirements specified in 1.4. For practical reasons, tR should be less
than 2 minutes.
1.2.9 Mixing chamber. A chamber constructed of glass, Teflon
[supreg], or other nonreactive material and designed to provide thorough
mixing of reaction products and diluent air. The residence time is not
critical when the dynamic parameter specification given in 1.4 is met.
1.2.10 Output manifold. The output manifold should be constructed of
glass, Teflon [supreg], or other non-reactive material and should be of
sufficient diameter to insure an insignificant pressure drop at the
analyzer connection. The system must have a vent designed to insure
atmospheric pressure at the manifold and to prevent ambient air from
entering the manifold.
1.3 Reagents.
1.3.1 NO concentration standard. Gas cylinder standard containing 50
to 100 ppm NO in N2 with less than 1 ppm NO2. This
standard must be traceable to a National Bureau of Standards (NBS) NO in
N2 Standard Reference Material (SRM 1683 or SRM 1684), an NBS
NO2 Standard Reference Material (SRM 1629), or an NBS/EPA-
approved commercially available Certified Reference Material (CRM).
CRM's are described in Reference 14, and a list of CRM sources is
available from the address shown for Reference 14. A recommended
protocol for certifying NO gas cylinders against either an NO SRM or CRM
[[Page 66]]
is given in section 2.0.7 of Reference 15. Reference 13 gives procedures
for certifying an NO gas cylinder against an NBS NO2 SRM and
for determining the amount of NO2 impurity in an NO cylinder.
1.3.2 Zero air. Air, free of contaminants which will cause a
detectable response on the NO/NOX/NO2 analyzer or
which might react with either NO, O3, or NO2 in
the gas phase titration. A procedure for generating zero air is given in
reference 13.
1.4 Dynamic parameter specification.
1.4.1 The O3 generator air flowrate (F0) and
NO flowrate (FNO) (see Figure 1) must be adjusted such that
the following relationship holds:
[GRAPHIC] [TIFF OMITTED] TC08NO91.076
[GRAPHIC] [TIFF OMITTED] TC08NO91.077
[GRAPHIC] [TIFF OMITTED] TC08NO91.078
where:
PR = dynamic parameter specification, determined empirically, to insure
complete reaction of the available O3, ppm-minute
[NO]RC = NO concentration in the reaction chamber, ppm
R = residence time of the reactant gases in the reaction chamber, minute
[NO]STD = concentration of the undiluted NO standard, ppm
FNO = NO flowrate, scm\3\/min
FO = O3 generator air flowrate, scm\3\/min
VRC = volume of the reaction chamber, scm\3\
1.4.2 The flow conditions to be used in the GPT system are
determined by the following procedure:
(a) Determine FT, the total flow required at the output manifold (FT
= analyzer demand plus 10 to 50% excess).
(b) Establish [NO]OUT as the highest NO concentration
(ppm) which will be required at the output manifold. [NO]OUT
should be approximately equivalent to 90% of the upper range limit (URL)
of the NO2 concentration range to be covered.
(c) Determine FNO as
[GRAPHIC] [TIFF OMITTED] TC08NO91.079
(d) Select a convenient or available reaction chamber volume.
Initially, a trial VRC may be selected to be in the range of
approximately 200 to 500 scm\3\.
(e) Compute FO as
(f) Compute tR as
[GRAPHIC] [TIFF OMITTED] TC08NO91.080
Verify that tR <2 minutes. If not, select a reaction chamber with a
smaller VRC.
(g) Compute the diluent air flowrate as
[GRAPHIC] [TIFF OMITTED] TC08NO91.081
where:
FD = diluent air flowrate, scm\3\/min
(h) If FO turns out to be impractical for the desired system, select
a reaction chamber having a different VRC and recompute FO and FD.
Note: A dynamic parameter lower than 2.75 ppm-minutes may be used if
it can be determined empirically that quantitative reaction of
O3 with NO occurs. A procedure for making this determination
as well as a more detailed discussion of the above requirements and
other related considerations is given in reference 13.
1.5 Procedure.
1.5.1 Assemble a dynamic calibration system such as the one shown in
Figure 1.
1.5.2 Insure that all flowmeters are calibrated under the conditions
of use against a reliable standard such as a soap-bubble meter or wet-
test meter. All volumetric flowrates should be corrected to 25 [deg]C
and 760 mm Hg. A discussion on the calibration of flowmeters is given in
reference 13.
1.5.3 Precautions must be taken to remove O2 and other
contaminants from the NO pressure regulator and delivery system prior to
the start of calibration to avoid any conversion of the standard NO to
NO2. Failure to do so can cause significant errors in
calibration. This problem may be minimized by (1) carefully evacuating
the regulator, when possible, after the regulator has been connected to
the cylinder and before opening the cylinder valve; (2) thoroughly
flushing the regulator and delivery system with NO after opening the
cylinder valve; (3) not removing the regulator from the cylinder between
calibrations unless absolutely necessary. Further discussion of these
procedures is given in reference 13.
1.5.4 Select the operating range of the NO/NOX/
NO2 analyzer to be calibrated. In order to obtain maximum
precision and accuracy for NO2 calibration, all three
channels of the analyzer should be set to the same range. If operation
of the NO and NOX channels on
[[Page 67]]
higher ranges is desired, subsequent recalibration of the NO and
NOX channels on the higher ranges is recommended.
Note: Some analyzer designs may require identical ranges for NO,
NOX, and NO2 during operation of the analyzer.
1.5.5 Connect the recorder output cable(s) of the NO/NOX/
NO2 analyzer to the input terminals of the strip chart
recorder(s). All adjustments to the analyzer should be performed based
on the appropriate strip chart readings. References to analyzer
responses in the procedures given below refer to recorder responses.
1.5.6 Determine the GPT flow conditions required to meet the dynamic
parameter specification as indicated in 1.4.
1.5.7 Adjust the diluent air and O3 generator air flows
to obtain the flows determined in section 1.4.2. The total air flow must
exceed the total demand of the analyzer(s) connected to the output
manifold to insure that no ambient air is pulled into the manifold vent.
Allow the analyzer to sample zero air until stable NO, NOX,
and NO2 responses are obtained. After the responses have
stabilized, adjust the analyzer zero control(s).
Note: Some analyzers may have separate zero controls for NO,
NOX, and NO2. Other analyzers may have separate
zero controls only for NO and NOX, while still others may
have only one zero control common to all three channels.
Offsetting the analyzer zero adjustments to + 5 percent of scale is
recommended to facilitate observing negative zero drift. Record the
stable zero air responses as ZNO, Znox, and Zno2.
1.5.8 Preparation of NO and NOX calibration curves.
1.5.8.1 Adjustment of NO span control. Adjust the NO flow from the
standard NO cylinder to generate an NO concentration of approximately 80
percent of the upper range limit (URL) of the NO range. This exact NO
concentration is calculated from:
[GRAPHIC] [TIFF OMITTED] TR31AU93.044
where:
[NO]OUT = diluted NO concentration at the output manifold, ppm
Sample this NO concentration until the NO and NOX responses
have stabilized. Adjust the NO span control to obtain a recorder
response as indicated below:
recorder response (percent scale) =
[GRAPHIC] [TIFF OMITTED] TR31AU93.045
where:
URL = nominal upper range limit of the NO channel, ppm
Note: Some analyzers may have separate span controls for NO,
NOX, and NO2. Other analyzers may have separate
span controls only for NO and NOX, while still others may
have only one span control common to all three channels. When only one
span control is available, the span adjustment is made on the NO channel
of the analyzer.
If substantial adjustment of the NO span control is necessary, it may be
necessary to recheck the zero and span adjustments by repeating steps
1.5.7 and 1.5.8.1. Record the NO concentration and the analyzer's NO
response.
1.5.8.2 Adjustment of NOX span control. When adjusting
the analyzer's NOX span control, the presence of any
NO2 impurity in the standard NO cylinder must be taken into
account. Procedures for determining the amount of NO2
impurity in the standard NO cylinder are given in reference 13. The
exact NOX concentration is calculated from:
[GRAPHIC] [TIFF OMITTED] TR31AU93.046
where:
[NOX]OUT = diluted NOX concentration at
the output manifold, ppm
[NO2]IMP = concentration of NO2
impurity in the standard NO cylinder, ppm
Adjust the NOX span control to obtain a recorder response as
indicated below:
recorder response (% scale) =
[GRAPHIC] [TIFF OMITTED] TR31AU93.047
Note: If the analyzer has only one span control, the span adjustment
is made on the NO channel and no further adjustment is made here for
NOX.
If substantial adjustment of the NOX span control is
necessary, it may be necessary to recheck the zero and span adjustments
by repeating steps 1.5.7 and 1.5.8.2. Record the NOX
concentration and the analyzer's NOX response.
1.5.8.3 Generate several additional concentrations (at least five
evenly spaced points across the remaining scale are suggested to verify
linearity) by decreasing FNO or increasing FD. For
each concentration generated, calculate the exact NO and NOX
concentrations using equations (9) and (11) respectively. Record the
analyzer's NO and NOX responses for each concentration. Plot
the analyzer responses versus the respective calculated NO and
NOX concentrations and draw or calculate the NO and
NOX calibration curves. For subsequent calibrations
[[Page 68]]
where linearity can be assumed, these curves may be checked with a two-
point calibration consisting of a zero air point and NO and
NOX concentrations of approximately 80% of the URL.
1.5.9 Preparation of NO2 calibration curve.
1.5.9.1 Assuming the NO2 zero has been properly adjusted
while sampling zero air in step 1.5.7, adjust FO and
FD as determined in section 1.4.2. Adjust FNO to
generate an NO concentration near 90% of the URL of the NO range. Sample
this NO concentration until the NO and NOX responses have
stabilized. Using the NO calibration curve obtained in section 1.5.8,
measure and record the NO concentration as [NO]orig. Using
the NOX calibration curve obtained in section 1.5.8, measure
and record the NOX concentration as
[NOX]orig.
1.5.9.2 Adjust the O3 generator to generate sufficient
O3 to produce a decrease in the NO concentration equivalent
to approximately 80% of the URL of the NO2 range. The
decrease must not exceed 90% of the NO concentration determined in step
1.5.9.1. After the analyzer responses have stabilized, record the
resultant NO and NOX concentrations as [NO]rem and
[NOX]rem.
1.5.9.3 Calculate the resulting NO2 concentration from:
[GRAPHIC] [TIFF OMITTED] TC08NO91.082
where:
[NO2]OUT = diluted NO2 concentration at
the output manifold, ppm
[NO]orig = original NO concentration, prior to addition of
O3, ppm
[NO]rem = NO concentration remaining after addition of
O3, ppm
Adjust the NO2 span control to obtain a recorder response as
indicated below:
recorder response (% scale) =
[GRAPHIC] [TIFF OMITTED] TR31AU93.048
Note: If the analyzer has only one or two span controls, the span
adjustments are made on the NO channel or NO and NOX channels
and no further adjustment is made here for NO2.
If substantial adjustment of the NO2 span control is
necessary, it may be necessary to recheck the zero and span adjustments
by repeating steps 1.5.7 and 1.5.9.3. Record the NO2
concentration and the corresponding analyzer NO2 and
NOX responses.
1.5.9.4 Maintaining the same FNO, FO, and
FD as in section 1.5.9.1, adjust the ozone generator to
obtain several other concentrations of NO2 over the
NO2 range (at least five evenly spaced points across the
remaining scale are suggested). Calculate each NO2
concentration using equation (13) and record the corresponding analyzer
NO2 and NOX responses. Plot the analyzer's
NO2 responses versus the corresponding calculated
NO2 concentrations and draw or calculate the NO2
calibration curve.
1.5.10 Determination of converter efficiency.
1.5.10.1 For each NO2 concentration generated during the
preparation of the NO2 calibration curve (see section 1.5.9)
calculate the concentration of NO2 converted from:
[GRAPHIC] [TIFF OMITTED] TC08NO91.083
where:
[NO2]CONV = concentration of NO2
converted, ppm
[NOX]orig = original NOX concentration
prior to addition of O3, ppm
[NOX]rem = NOX concentration remaining
after addition of O3, ppm
Note: Supplemental information on calibration and other procedures
in this method are given in reference 13.
Plot [NO2]CONV (y-axis) versus
[NO2]OUT (x-axis) and draw or calculate the
converter efficiency curve. The slope of the curve times 100 is the
average converter efficiency, EC The average converter
efficiency must be greater than 96%; if it is less than 96%, replace or
service the converter.
2. Alternative B--NO2 permeation device.
Major equipment required:
Stable O3 generator.
Chemiluminescence NO/NOX/NO2 analyzer with strip chart
recorder(s).
NO concentration standard.
NO2 concentration standard.
[[Page 69]]
2.1 Principle. Atmospheres containing accurately known
concentrations of nitrogen dioxide are generated by means of a
permeation device. (10) The permeation device emits NO2 at a
known constant rate provided the temperature of the device is held
constant (0.1 [deg]C) and the device has been
accurately calibrated at the temperature of use. The NO2
emitted from the device is diluted with zero air to produce
NO2 concentrations suitable for calibration of the
NO2 channel of the NO/NOX/NO2 analyzer. An NO
concentration standard is used for calibration of the NO and NOX
channels of the analyzer.
2.2 Apparatus. A typical system suitable for generating the required
NO and NO2 concentrations is shown in Figure 2. All
connections between components downstream from the permeation device
should be of glass, Teflon [supreg], or other non-reactive material.
2.2.1 Air flow controllers. Devices capable of maintaining constant
air flows within 2% of the required flowrate.
2.2.2 NO flow controller. A device capable of maintaining constant
NO flows within 2% of the required flowrate.
Component parts in contact with the NO must be of a non-reactive
material.
2.2.3 Air flowmeters. Calibrated flowmeters capable of measuring and
monitoring air flowrates with an accuracy of 2% of
the measured flowrate.
2.2.4 NO flowmeter. A calibrated flowmeter capable of measuring and
monitoring NO flowrates with an accuracy of 2% of
the measured flowrate. (Rotameters have been reported to operate
unreliably when measuring low NO flows and are not recommended.)
2.2.5 Pressure regulator for standard NO cylinder. This regulator
must have a non-reactive diaphragm and internal parts and a suitable
delivery pressure.
2.2.6 Drier. Scrubber to remove moisture from the permeation device
air system. The use of the drier is optional with NO2
permeation devices not sensitive to moisture. (Refer to the supplier's
instructions for use of the permeation device.)
2.2.7 Constant temperature chamber. Chamber capable of housing the
NO2 permeation device and maintaining its temperature to
within 0.1 [deg]C.
2.2.8 Temperature measuring device. Device capable of measuring and
monitoring the temperature of the NO2 permeation device with
an accuracy of 0.05 [deg]C.
2.2.9 Valves. A valve may be used as shown in Figure 2 to divert the
NO2 from the permeation device when zero air or NO is
required at the manifold. A second valve may be used to divert the NO
flow when zero air or NO2 is required at the manifold.
The valves should be constructed of glass, Teflon [supreg], or other
nonreactive material.
2.2.10 Mixing chamber. A chamber constructed of glass, Teflon
[supreg], or other nonreactive material and designed to provide thorough
mixing of pollutant gas streams and diluent air.
2.2.11 Output manifold. The output manifold should be constructed of
glass, Teflon [supreg], or other non-reactive material and should be of
sufficient diameter to insure an insignificant pressure drop at the
analyzer connection. The system must have a vent designed to insure
atmospheric pressure at the manifold and to prevent ambient air from
entering the manifold.
2.3 Reagents.
2.3.1 Calibration standards. Calibration standards are required for
both NO and NO2. The reference standard for the calibration
may be either an NO or NO2 standard, and must be traceable to
a National Bureau of Standards (NBS) NO in N2 Standard
Reference Material (SRM 1683 or SRM 1684), and NBS NO2
Standard Reference Material (SRM 1629), or an NBS/EPA-approved
commercially available Certified Reference Material (CRM). CRM's are
described in Reference 14, and a list of CRM sources is available from
the address shown for Reference 14. Reference 15 gives recommended
procedures for certifying an NO gas cylinder against an NO SRM or CRM
and for certifying an NO2 permeation device against an
NO2 SRM. Reference 13 contains procedures for certifying an
NO gas cylinder against an NO2 SRM and for certifying an
NO2 permeation device against an NO SRM or CRM. A procedure
for determining the amount of NO2 impurity in an NO cylinder
is also contained in Reference 13. The NO or NO2 standard
selected as the reference standard must be used to certify the other
standard to ensure consistency between the two standards.
2.3.1.1 NO2 Concentration standard. A permeation device
suitable for generating NO2 concentrations at the required
flow-rates over the required concentration range. If the permeation
device is used as the reference standard, it must be traceable to an SRM
or CRM as specified in 2.3.1. If an NO cylinder is used as the reference
standard, the NO2 permeation device must be certified against
the NO standard according to the procedure given in Reference 13. The
use of the permeation device should be in strict accordance with the
instructions supplied with the device. Additional information regarding
the use of permeation devices is given by Scaringelli et al. (11) and
Rook et al. (12).
2.3.1.2 NO Concentration standard. Gas cylinder containing 50 to 100
ppm NO in N2 with less than 1 ppm NO2. If this
cylinder is used as the reference standard, the cylinder must be
traceable to an SRM or CRM as specified in 2.3.1. If an NO2
permeation device is used as the reference standard, the NO cylinder
must be certified against the NO2 standard according to the
procedure given in Reference 13. The cylinder should be recertified
[[Page 70]]
on a regular basis as determined by the local quality control program.
2.3.3 Zero air. Air, free of contaminants which might react with NO
or NO2 or cause a detectable response on the NO/NOX/
NO2 analyzer. When using permeation devices that are
sensitive to moisture, the zero air passing across the permeation device
must be dry to avoid surface reactions on the device. (Refer to the
supplier's instructions for use of the permeation device.) A procedure
for generating zero air is given in reference 13.
2.4 Procedure.
2.4.1 Assemble the calibration apparatus such as the typical one
shown in Figure 2.
2.4.2 Insure that all flowmeters are calibrated under the conditions
of use against a reliable standard such as a soap bubble meter or wet-
test meter. All volumetric flowrates should be corrected to 25 [deg]C
and 760 mm Hg. A discussion on the calibration of flowmeters is given in
reference 13.
2.4.3 Install the permeation device in the constant temperature
chamber. Provide a small fixed air flow (200-400 scm\3\/min) across the
device. The permeation device should always have a continuous air flow
across it to prevent large buildup of NO2 in the system and a
consequent restabilization period. Record the flowrate as FP. Allow the
device to stabilize at the calibration temperature for at least 24
hours. The temperature must be adjusted and controlled to within 0.1 [deg]C or less of the calibration temperature as
monitored with the temperature measuring device.
2.4.4 Precautions must be taken to remove O2 and other
contaminants from the NO pressure regulator and delivery system prior to
the start of calibration to avoid any conversion of the standard NO to
NO2. Failure to do so can cause significant errors in
calibration. This problem may be minimized by
(1) Carefully evacuating the regulator, when possible, after the
regulator has been connected to the cylinder and before opening the
cylinder valve;
(2) Thoroughly flushing the regulator and delivery system with NO
after opening the cylinder valve;
(3) Not removing the regulator from the cylinder between
calibrations unless absolutely necessary. Further discussion of these
procedures is given in reference 13.
2.4.5 Select the operating range of the NO/NOX NO2
analyzer to be calibrated. In order to obtain maximum precision and
accuracy for NO2 calibration, all three channels of the
analyzer should be set to the same range. If operation of the NO and NOX
channels on higher ranges is desired, subsequent recalibration of the NO
and NOX channels on the higher ranges is recommended.
Note: Some analyzer designs may require identical ranges for NO,
NOX, and NO2 during operation of the analyzer.
2.4.6 Connect the recorder output cable(s) of the NO/NOX/
NO2 analyzer to the input terminals of the strip chart
recorder(s). All adjustments to the analyzer should be performed based
on the appropriate strip chart readings. References to analyzer
responses in the procedures given below refer to recorder responses.
2.4.7 Switch the valve to vent the flow from the permeation device
and adjust the diluent air flowrate, FD, to provide zero air at the
output manifold. The total air flow must exceed the total demand of the
analyzer(s) connected to the output manifold to insure that no ambient
air is pulled into the manifold vent. Allow the analyzer to sample zero
air until stable NO, NOX, and NO2 responses are obtained.
After the responses have stabilized, adjust the analyzer zero
control(s).
Note: Some analyzers may have separate zero controls for NO, NOX,
and NO2. Other analyzers may have separate zero controls only
for NO and NOX, while still others may have only one zero common control
to all three channels.
Offsetting the analyzer zero adjustments to + 5% of scale is recommended
to facilitate observing negative zero drift. Record the stable zero air
responses as ZNO, ZNOX, and
ZNO2.
2.4.8 Preparation of NO and NOX calibration curves.
2.4.8.1 Adjustment of NO span control. Adjust the NO flow from the
standard NO cylinder to generate an NO concentration of approximately
80% of the upper range limit (URL) of the NO range. The exact NO
concentration is calculated from:
[GRAPHIC] [TIFF OMITTED] TR31AU93.049
where:
[NO]OUT = diluted NO concentration at the output manifold,
ppm
FNO = NO flowrate, scm\3\/min
[NO]STD = concentration of the undiluted NO standard, ppm
FD = diluent air flowrate, scm\3\/min
Sample this NO concentration until the NO and NOX responses have
stabilized. Adjust the NO span control to obtain a recorder response as
indicated below:
recorder response (% scale) =
[GRAPHIC] [TIFF OMITTED] TR31AU93.050
[GRAPHIC] [TIFF OMITTED] TR31AU93.051
where:
[[Page 71]]
URL = nominal upper range limit of the NO channel, ppm
Note: Some analyzers may have separate span controls for NO, NOX,
and NO2. Other analyzers may have separate span controls only
for NO and NOX, while still others may have only one span control common
to all three channels. When only one span control is available, the span
adjustment is made on the NO channel of the analyzer.
If substantial adjustment of the NO span control is necessary, it may be
necessary to recheck the zero and span adjustments by repeating steps
2.4.7 and 2.4.8.1. Record the NO concentration and the analyzer's NO
response.
2.4.8.2 Adjustment of NOX span control. When adjusting the
analyzer's NOX span control, the presence of any NO2 impurity
in the standard NO cylinder must be taken into account. Procedures for
determining the amount of NO2 impurity in the standard NO
cylinder are given in reference 13. The exact NOX concentration is
calculated from:
[GRAPHIC] [TIFF OMITTED] TR31AU93.052
where:
[NOX]OUT = diluted NOX cencentration at
the output manifold, ppm
[NO2]IMP = concentration of NO2
impurity in the standard NO cylinder, ppm
Adjust the NOX span control to obtain a convenient recorder response as
indicated below:
recorder response (% scale)
[GRAPHIC] [TIFF OMITTED] TR31AU93.053
Note: If the analyzer has only one span control, the span adjustment
is made on the NO channel and no further adjustment is made here for
NOX.
If substantial adjustment of the NOX span control is
necessary, it may be necessary to recheck the zero and span adjustments
by repeating steps 2.4.7 and 2.4.8.2. Record the NOX
concentration and the analyzer's NOX response.
2.4.8.3 Generate several additional concentrations (at least five
evenly spaced points across the remaining scale are suggested to verify
linearity) by decreasing FNO or increasing FD. For each
concentration generated, calculate the exact NO and NOX
concentrations using equations (16) and (18) respectively. Record the
analyzer's NO and NOX responses for each concentration. Plot
the analyzer responses versus the respective calculated NO and
NOX concentrations and draw or calculate the NO and
NOX calibration curves. For subsequent calibrations where
linearity can be assumed, these curves may be checked with a two-point
calibration consisting of a zero point and NO and NOX
concentrations of approximately 80 percent of the URL.
2.4.9 Preparation of NO2 calibration curve.
2.4.9.1 Remove the NO flow. Assuming the NO2 zero has
been properly adjusted while sampling zero air in step 2.4.7, switch the
valve to provide NO2 at the output manifold.
2.4.9.2 Adjust FD to generate an NO2 concentration of
approximately 80 percent of the URL of the NO2 range. The
total air flow must exceed the demand of the analyzer(s) under
calibration. The actual concentration of NO2 is calculated
from:
[GRAPHIC] [TIFF OMITTED] TR31AU93.054
where:
[NO2]OUT = diluted NO2 concentration at
the output manifold, ppm
R = permeation rate, [micro]g/min
K = 0.532 [micro]l NO2/[micro]g NO2 (at 25 [deg]C
and 760 mm Hg)
Fp = air flowrate across permeation device, scm\3\/min
FD = diluent air flowrate, scm\3\/min
Sample this NO2 concentration until the NOX and
NO2 responses have stabilized. Adjust the NO2 span
control to obtain a recorder response as indicated below:
recorder response (% scale)
[GRAPHIC] [TIFF OMITTED] TR31AU93.055
Note: If the analyzer has only one or two span controls, the span
adjustments are made on the NO channel or NO and NOX channels
and no further adjustment is made here for NO2.
If substantial adjustment of the NO2 span control is
necessary it may be necessary to recheck the zero and span adjustments
by repeating steps 2.4.7 and 2.4.9.2. Record the NO2
concentration and the analyzer's NO2 response. Using the
NOX calibration curve obtained in step 2.4.8, measure and
record the NOX concentration as [NOX]M.
2.4.9.3 Adjust FD to obtain several other concentrations of
NO2 over the NO2 range (at least five evenly
spaced points across the remaining scale are suggested). Calculate each
NO2 concentration using equation (20) and record the
corresponding analyzer NO2 and NOX responses. Plot
the analyzer's NO2 responses versus the corresponding
calculated NO2 concentrations and draw or calculate the
NO2 calibration curve.
2.4.10 Determination of converter efficiency.
2.4.10.1 Plot [NOX]M (y-axis) versus
[NO2]OUT (x-axis) and draw or calculate the
converter efficiency curve. The slope of the curve times 100 is the
average converter efficiency,
[[Page 72]]
EC. The average converter efficiency must be greater than 96 percent; if
it is less than 96 percent, replace or service the converter.
Note: Supplemental information on calibration and other procedures
in this method are given in reference 13.
3. Frequency of calibration. The frequency of calibration, as well
as the number of points necessary to establish the calibration curve and
the frequency of other performance checks, will vary from one analyzer
to another. The user's quality control program should provide guidelines
for initial establishment of these variables and for subsequent
alteration as operational experience is accumulated. Manufacturers of
analyzers should include in their instruction/operation manuals
information and guidance as to these variables and on other matters of
operation, calibration, and quality control.
References
1. A. Fontijn, A. J. Sabadell, and R. J. Ronco, ``Homogeneous
Chemiluminescent Measurement of Nitric Oxide with Ozone,'' Anal. Chem.,
42, 575 (1970).
2. D. H. Stedman, E. E. Daby, F. Stuhl, and H. Niki, ``Analysis of
Ozone and Nitric Oxide by a Chemiluminiscent Method in Laboratory and
Atmospheric Studies of Photochemical Smog,'' J. Air Poll. Control
Assoc., 22, 260 (1972).
3. B. E. Martin, J. A. Hodgeson, and R. K. Stevens, ``Detection of
Nitric Oxide Chemiluminescence at Atmospheric Pressure,'' Presented at
164th National ACS Meeting, New York City, August 1972.
4. J. A. Hodgeson, K. A. Rehme, B. E. Martin, and R. K. Stevens,
``Measurements for Atmospheric Oxides of Nitrogen and Ammonia by
Chemiluminescence,'' Presented at 1972 APCA Meeting, Miami, FL, June
1972.
5. R. K. Stevens and J. A. Hodgeson, ``Applications of
Chemiluminescence Reactions to the Measurement of Air Pollutants,''
Anal. Chem., 45, 443A (1973).
6. L. P. Breitenbach and M. Shelef, ``Development of a Method for
the Analysis of NO2 and NH3 by NO-Measuring
Instruments,'' J. Air Poll. Control Assoc., 23, 128 (1973).
7. A. M. Winer, J. W. Peters, J. P. Smith, and J. N. Pitts, Jr.,
``Response of Commercial Chemiluminescent NO-NO2 Analyzers to
Other Nitrogen-Containing Compounds,'' Environ. Sci. Technol., 8, 1118
(1974).
8. K. A. Rehme, B. E. Martin, and J. A. Hodgeson, Tentative Method
for the Calibration of Nitric Oxide, Nitrogen Dioxide, and Ozone
Analyzers by Gas Phase Titration,'' EPA-R2-73-246, March 1974.
9. J. A. Hodgeson, R. K. Stevens, and B. E. Martin, ``A Stable Ozone
Source Applicable as a Secondary Standard for Calibration of Atmospheric
Monitors,'' ISA Transactions, 11, 161 (1972).
10. A. E. O'Keeffe and G. C. Ortman, ``Primary Standards for Trace
Gas Analysis,'' Anal. Chem., 38, 760 (1966).
11. F. P. Scaringelli, A. E. O'Keeffe, E. Rosenberg, and J. P. Bell,
``Preparation of Known Concentrations of Gases and Vapors with
Permeation Devices Calibrated Gravimetrically,'' Anal. Chem., 42, 871
(1970).
12. H. L. Rook, E. E. Hughes, R. S. Fuerst, and J. H. Margeson,
``Operation Characteristics of NO2 Permeation Devices,''
Presented at 167th National ACS Meeting, Los Angeles, CA, April 1974.
13. E. C. Ellis, ``Technical Assistance Document for the
Chemiluminescence Measurement of Nitrogen Dioxide,'' EPA-E600/4-75-003
(Available in draft form from the United States Environmental Protection
Agency, Department E (MD-76), Environmental Monitoring and Support
Laboratory, Research Triangle Park, NC 27711).
14. A Procedure for Establishing Traceability of Gas Mixtures to
Certain National Bureau of Standards Standard Reference Materials. EPA-
600/7-81-010, Joint publication by NBS and EPA. Available from the U.S.
Environmental Protection Agency, Environmental Monitoring Systems
Laboratory (MD-77), Research Triangle Park, NC 27711, May 1981.
15. Quality Assurance Handbook for Air Pollution Measurement
Systems, Volume II, Ambient Air Specific Methods. The U.S. Environmental
Protection Agency, Environmental Monitoring Systems Laboratory, Research
Triangle Park, NC 27711. Publication No. EAP-600/4-77-027a.
[[Page 73]]
[41 FR 52688, Dec. 1, 1976, as amended at 48 FR 2529, Jan. 20, 1983]
[[Page 74]]
Sec. Appendix G to Part 50--Reference Method for the Determination of
Lead in Total Suspended Particulate Matter
1.0 Scope and Applicability
Based on review of the air quality criteria and national ambient air
quality standard (NAAQS) for lead (Pb) completed in 2008, the EPA made
revisions to the primary and secondary NAAQS for Pb to protect public
health and welfare. The EPA revised the level from 1.5 [micro]g/m\3\ to
0.15 [micro]g/m\3\ while retaining the current indicator of Pb in total
suspended particulate matter (Pb-TSP).
Pb-TSP is collected for 24 hours on a TSP filter as described in
Appendix B of part 50, the Reference Method for the Determination of
Suspended Particulate Matter in the Atmosphere (High-Volume Method).
This method is for the analysis of Pb from TSP filters by Inductively
Coupled Plasma Mass Spectrometry (ICP-MS) using a heated ultrasonic bath
with nitric acid (HNO3) and hydrochloric acid (HCl) or a
heated block (hot block) digester with HNO3 for filter
extraction.
This method is based on the EPA's Office of Solid Waste (SW-846)
Method 6020A--Inductively Coupled Plasma Mass Spectrometry (U.S. EPA,
2007). Wording in certain sections of this method is paraphrased or
taken directly from Method 6020A.
1.1 ICP-MS is applicable for the sub-[micro]g/mL (ppb) determination
of Pb in a wide variety of matrices. Results reported for monitoring or
compliance purposes are calculated in [micro]g/m\3\ at local conditions
(LC). This procedure describes a method for the acid extraction of Pb in
particulate matter collected on glass fiber, quartz, or PTFE filters and
measurement of the extracted Pb using ICP-MS.
1.2 Due to variations in the isotopic abundance of Pb, the value for
total Pb must be based on the sum of the signal intensities for isotopic
masses, 206, 207, and 208. Most instrument software packages are able to
sum the primary isotope signal intensities automatically.
1.3 ICP-MS requires the use of an internal standard. \115\In
(Indium), \165\Ho (Holmium), and \209\Bi (Bismuth) are recommended
internal standards for the determination of Pb.
1.4 Use of this method is restricted to use by, or under supervision
of, properly trained and experienced laboratory personnel. Requirements
include training and experience in inorganic sample preparation,
including acid extraction, and also knowledge in the recognition and in
the correction of spectral, chemical and physical interference in ICP-
MS.
2.0 Summary of Method
2.1 This method describes the acid extraction of Pb in particulate
matter collected on glass fiber, quartz, or PTFE ambient air filters
with subsequent measurement of Pb by ICP-MS. Estimates of the Method
Detection Limit (MDL) or sensitivity of the method are provided in
Tables 1, 3 and 5 and determined using Pb-spiked filters or filter
strips analyzed in accordance with the guidance provided in 40 CFR 136,
Appendix B--Determination and procedures for the Determination of the
Method Detection Limit--Revision 1.1. The analytical range of the method
is 0.00024 [micro]g/m\3\ to 0.60 [micro]g/m\3\, and based on the low and
high calibration curve standards and a nominal filter sample volume of
2000 m\3\.
2.2 This method includes two extraction methods. In the first
method, a solution of HNO3 and HCl is added to the filters or
filter strips in plastic digestion tubes and the tubes are placed in a
heated ultrasonic bath for one hour to facilitate the extraction of Pb.
Following ultrasonication, the samples are brought to a final volume of
40 mL (50 mL for PTFE filters), vortex mixed or shaken vigorously, and
centrifuged prior to aliquots being taken for ICP-MS analysis. In the
second method, a solution of dilute HNO3 is added to the
filter strips in plastic digestion tubes and the tubes placed into the
hot block digester. The filter strip is completely covered by the
solution. The tubes are covered with polypropylene watch glasses and
refluxed. After reflux, the samples are diluted to a final volume of 50
mL with reagent water and mixed before analysis.
2.3 Calibration standards and check standards are prepared to matrix
match the acid composition of the samples. ICP-MS analysis is then
performed. With this method, the samples are first aspirated and the
aerosol thus created is transported by a flow of argon gas into the
plasma torch. The ions produced (e.g., Pb\ + 1\) in the plasma are
extracted via a differentially-pumped vacuum interface and are separated
on the basis of their mass-to-charge ratio. The ions are quantified by a
channel electron multiplier or a Faraday detector and the signal
collected is processed by the instrument's software. Interferences must
be assessed and corrected for, if present.
3.0 Definitions
Pb--Elemental or ionic lead
HNO3--Nitric acid
HCl--Hydrochloric acid
ICP-MS--Inductively Coupled Plasma Mass Spectrometer
MDL--Method detection limit
RSD--Relative standard deviation
RPD--Relative percent difference
CB--Calibration Blank
CAL--Calibration Standard
ICB--Initial calibration blank
CCB--Continuing calibration blank
ICV--Initial calibration verification
CCV--Continuing calibration verification
[[Page 75]]
LLCV--Lower Level Calibration Verification, serves as the lower level
ICV and lower level CCV
RB--Reagent blank
RBS--Reagent blank spike
MSDS--Material Safety Data Sheet
NIST--National Institute of Standards and Technology
D.I. water--Deionized water
SRM--NIST Standard Reference Material
CRM--Certified Reference Material
EPA--Environmental Protection Agency
v/v--Volume to volume ratio
4.0 Interferences
4.1 Reagents, glassware, plasticware, and other sample processing
hardware may yield artifacts and/or interferences to sample analysis. If
reagent blanks, filter blanks, or quality control blanks yield results
above the detection limit, the source of contamination must be
identified. All containers and reagents used in the processing of the
samples must be checked for contamination prior to sample extraction and
analysis. Reagents shall be diluted to match the final concentration of
the extracts and analyzed for Pb. Labware shall be rinsed with dilute
acid solution and the solution analyzed. Once a reagent or labware
article (such as extraction tubes) from a manufacturer has been
successfully screened, additional screening is not required unless
contamination is suspected.
4.2 Isobaric elemental interferences in ICP-MS are caused by
isotopes of different elements forming atomic ions with the same nominal
mass-to-charge ratio (m/z) as the species of interest. There are no
species found in ambient air that will result in isobaric interference
with the three Pb isotopes (206, 207, and 208) being measured.
Polyatomic interferences occur when two or more elements combine to form
an ion with the same mass-to-charge ratio as the isotope being measured.
Pb is not subject to interference from common polyatomic ions and no
correction is required.
4.3 The distribution of Pb isotopes is not constant. The analysis of
total Pb should be based on the summation of signal intensities for the
isotopic masses 206, 207, and 208. In most cases, the instrument
software can perform the summation automatically.
4.4 Physical interferences are associated with the sample
nebulization and transport processes as well as with ion-transmission
efficiencies. Dissolved solids can deposit on the nebulizer tip of a
pneumatic nebulizer and on the interface skimmers of the ICP-MS.
Nebulization and transport processes can be affected if a matrix
component causes a change in surface tension or viscosity. Changes in
matrix composition can cause significant signal suppression or
enhancement. These interferences are compensated for by use of internal
standards. Sample dilution will reduce the effects of high levels of
dissolved salts, but calibration standards must be prepared in the
extraction medium and diluted accordingly.
4.5 Memory interferences are related to sample transport and result
when there is carryover from one sample to the next. Sample carryover
can result from sample deposition on the sample and skimmer cones and
from incomplete rinsing of the sample solution from the plasma torch and
the spray chamber between samples. These memory effects are dependent
upon both the analyte being measured and sample matrix and can be
minimized through the use of suitable rinse times.
5.0 Health and Safety Cautions
5.1 The toxicity or carcinogenicity of reagents used in this method
has not been fully established. Each chemical should be regarded as a
potential health hazard and exposure to these compounds should be as low
as reasonably achievable. Each laboratory is responsible for maintaining
a current file of OSHA regulations regarding the safe handling of the
chemicals specified in this method. A reference file of material safety
data sheets (MSDSs) should be available to all personnel involved in the
chemical analysis. Specifically, concentrated HNO3 presents
various hazards and is moderately toxic and extremely irritating to skin
and mucus membranes. Use this reagent in a fume hood whenever possible
and if eye or skin contact occurs, flush with large volumes of water.
Always wear safety glasses or a shield for eye protection, protective
clothing, and observe proper mixing when working with these reagents.
5.2 Concentrated HNO3 and HCl are moderately toxic and
extremely irritating to the skin. Use these reagents in a fume hood, and
if eye and skin contact occurs, flush with large volumes of water.
Always wear safety glasses or a shield for eye protection when working
with these reagents. The component of this procedure requiring the
greatest care is HNO3. HNO3 is a strong,
corrosive, oxidizing agent that requires protection of the eyes, skin,
and clothing. Items to be worn during use of this reagent include:
1. Safety goggles (or safety glasses with side shields),
2. Acid resistant rubber gloves, and
3. A protective garment such as a laboratory apron. HNO3
spilled on clothing will destroy the fabric; contact with the skin
underneath will result in a burn.
It is also essential that an eye wash fountain or eye wash bottle be
available during performance of this method. An eye wash bottle has a
spout that covers the eye. If acid or any other corrosive gets into the
eye, the water in this bottle is squirted onto the eye to wash out the
harmful material. Eye washing should be performed with large amounts
[[Page 76]]
of water immediately after exposure. Medical help should be sought
immediately after washing. If either acid, but especially
HNO3, is spilled onto the skin, wash immediately with large
amounts of water. Medical attention is not required unless the burn
appears to be significant. Even after washing and drying,
HNO3 may leave the skin slightly brown in color; this will
heal and fade with time.
5.3 Pb salts and Pb solutions are toxic. Great care must be taken to
ensure that samples and standards are handled properly; wash hands
thoroughly after handling.
5.4 Care must be taken when using the ultrasonic bath and hot block
digester as they are capable of causing mild burns. Users should refer
to the safety guidance provided by the manufacturer of their specific
equipment.
5.5 Analytical plasma sources emit radio frequency radiation in
addition to intense ultra violet (UV) radiation. Suitable precautions
should be taken to protect personnel from such hazards. The inductively
coupled plasma should only be viewed with proper eye protection from UV
emissions.
6.0 Equipment
6.1 Thermo Scientific X-Series ICP-MS or equivalent. The system must
be capable of providing resolution better or equal to 1.0 atomic mass
unit (amu) at 10 percent peak height. The system must have a mass range
from at least 7 to 240 amu that allows for the application of the
internal standard technique. For the measurement of Pb, an instrument
with a collision or reaction cell is not required.
6.2 Ultrasonic Extraction Equipment
6.2.1 Heated ultrasonic bath capable of maintaining a temperature of
80 [deg]C; VWR Model 750HT, 240W, or equivalent. Ultrasonic bath must
meet the following performance criteria:
1. Cut a strip of aluminum foil almost the width of the tank and
double the depth.
2. Turn the ultrasonic bath on and lower the foil into the bath
vertically until almost touching the bottom of the tank and hold for 10
seconds.
3. Remove the foil from the tank and observe the distribution of
perforations and small pin prick holes. The indentations should be fine
and evenly distributed. The even distribution of indentations indicates
the ultrasonic bath is acceptable for use.
6.2.2 Laboratory centrifuge, Beckman GS-6, or equivalent.
6.2.3 Vortex mixer, VWR Signature Digital Vortex Mixer, VWR Catalog
No. 14005-824, or equivalent.
6.3 Hot block extraction equipment
6.3.1 Hot block digester, SCP Science DigiPrep Model MS, No. 010-
500-205 block digester capable of maintaining a temperature of 95
[deg]C, or equivalent.
6.4 Materials and Supplies
Argon gas supply, 99.99 percent purity or better.
National Welders Microbulk, or equivalent.
Plastic digestion tubes with threaded caps for
extraction and storage, SCP Science DigiTUBE[supreg] Item No. 010-500-
063, or equivalent.
Disposable polypropylene ribbed watch glasses
(for heated block extraction), SCP Science Item No. 010-500-081, or
equivalent.
Pipette, Rainin EDP2, 100 [micro]L, 1 percent accuracy, <=1 percent RSD (precision), with
disposable tips, or equivalent.
Pipette, Rainin EDP2, 1000 [micro]L, 1 percent accuracy, <=1 percent RSD (precision), with
disposable tips, or equivalent.
Pipette, Rainin EDP2, 1-10 mL, 1 percent accuracy, <=1 percent RSD (precision), with
disposable tips, or equivalent.
Pipette, Thermo Lab Systems, 5 mL, 1 percent accuracy, <=1 percent RSD (precision), with
disposable tips, or equivalent.
Plastic tweezer, VWR Catalog No. 89026-420, or
equivalent.
Laboratory marker.
Ceramic knife, Kyocera LK-25, and non-metal ruler
or other suitable cutting tools for making straight cuts for accurately
measured strips.
Blank labels or labeling tape, VWR Catalog No.
36425-045, or equivalent.
Graduated cylinder, 1 L, VWR 89000-260, or
equivalent.
Volumetric flask, Class A, 1 L, VWR Catalog No.
89025-778, or equivalent.
Millipore Element deionized water system, or
equivalent, capable of generating water with a resistivity of
=17.9 M[Omega]-cm).
Disposable syringes, 10-mL, with 0.45 micron
filters (must be Pb-free).
Plastic or PTFE wash bottles.
Glassware, Class A--volumetric flasks, pipettes,
and graduated cylinders.
Glass fiber, quartz, or PTFE filters from the
same filter manufacturer and lot used for sample collection for use in
the determination of the MDL and for laboratory blanks.
7.0 Reagents and Standards
7.1 Reagent--or trace metals-grade chemicals must be used in all
tests. Unless otherwise indicated, it is intended that all reagents
conform to the specifications of the Committee on Analytical Reagents of
the American Chemical Society, where such specifications are available.
7.2 Concentrated nitric acid, 67-70 percent, SCP Science Catalog No.
250-037-177, or equivalent.
7.3 Concentrated hydrochloric acid (for the ultrasonic extraction
method), 33-36 percent, SCP Science Catalog No. 250-037-175, or
equivalent.
[[Page 77]]
7.4 Deionized water--All references to deionized water in the method
refer to deionized water with a resistivity =17.9 M[Omega]-
cm.
7.5 Standard stock solutions may be commercially purchased for each
element or as a multi-element mix. Internal standards may be purchased
as a mixed multi-element solution. The manufacturer's expiration date
and storage conditions must be adhered to.
7.5.1 Lead standard, 1000 [micro]g/mL, NIST traceable, commercially
available with certificate of analysis. High Purity Standards Catalog
No. 100028-1, or equivalent.
7.5.2 Indium (In) standard, 1000 [micro]g/mL, NIST traceable,
commercially available with certificate of analysis. High Purity
Standards Catalog No. 100024-1, or equivalent.
7.5.3 Bismuth (Bi) standard, 1000 [micro]g/mL, NIST traceable,
commercially available with certificate of analysis. High Purity
Standards Catalog No. 100006-1, or equivalent.
7.5.4 Holmium (Ho) standard, 1000 [micro]g/mL, NIST traceable,
commercially available with certificate of analysis. High Purity
Standards Catalog No. 100023-1, or equivalent.
7.5.5 Second source lead standard, 1000 [micro]g/mL, NIST traceable,
commercially available with certificate of analysis. Must be from a
different vendor or lot than the standard described in 7.5.1. Inorganic
Ventures Catalog No. CGPB-1, or equivalent.
7.5.6 Standard Reference Materials, NIST SRM 2583, 2586, 2587 or
1648, or equivalent.\5\
---------------------------------------------------------------------------
\5\ Certificates of Analysis for these SRMs can be found at: http://
www.nist.gov/srm/index.cfm.
---------------------------------------------------------------------------
Note: The In, Bi, and Ho internal standards may also be purchased as
10 [micro]g/mL standards. Calibration standards are prepared by diluting
stock standards to the appropriate levels in the same acid
concentrations as in the final sample volume. The typical range for
calibration standards is 0.001 to 2.00 [micro]g/mL. At a minimum, the
curve must contain a blank and five Pb containing calibration standards.
The calibration standards are stored at ambient laboratory temperature.
Calibration standards must be prepared weekly and verified against a
freshly prepared ICV using a NIST-traceable source different from the
calibration standards.
7.6 Internal standards may be added to the test solution or by on-
line addition. The nominal concentration for an internal standard is
0.010 [micro]g/mL (10 ppb). Bismuth (Bi) or holmium (Ho) are the
preferred internal standards for Pb, but indium (In) may be used in the
event the sample contains Bi and high recoveries are observed.
7.7 Three laboratory blank solutions are required for analysis: (1)
The calibration blank is used in the construction of the calibration
curve and as a periodic check of system cleanliness (ICB and CCB); (2)
the reagent blank (RB) is carried through the extraction process to
assess possible contamination; and (3) the rinse blank is run between
samples to clean the sample introduction system. If RBs or laboratory
blanks yield results above the detection limit, the source of
contamination must be identified. Screening of labware and reagents is
addressed in Section 4.1.
7.7.1 The calibration blank is prepared in the same acid matrix as
the calibration standards and samples and contains all internal
standards used in the analysis.
7.7.2 The RB contains all reagents used in the extraction and is
carried through the extraction procedure at the same time as the
samples.
7.7.3 The rinse blank is a solution of 1 to 2 percent
HNO3 (v/v) in reagent grade water. A sufficient volume should
be prepared to flush the system between all standards and samples
analyzed.
7.7.4 The EPA currently provides glass fiber, quartz, and PTFE
filters to air monitoring agencies as requested annually. As part of the
procurement process, these filters are tested for acceptance by the EPA.
The current acceptance criteria for glass fiber and quartz filters is 15
[micro]g per filter or 0.0075 [micro]g/m\3\ using a nominal sample
volume of 2000 m\3\ and 4.8 ng/cm\2\ or 0.0024 [micro]g/m\3\ for PTFE
filters using a nominal sample volume of 24 m\3\. Acceptance test
results for filters obtained by the EPA are typically well below the
criterion specified and also below the recently revised Pb method
performance detection limit of 0.0075 [micro]g/m\3\; therefore, blank
subtraction should not be performed.
7.7.5 If filters are not provided by the EPA for sample collection
and analysis, filter lot blanks should be analyzed for Pb content. For
large filter lots (500 filters), randomly select 20 to 30
filters from the lot and analyze the filter or filter strips for Pb. For
smaller filter lots, a lesser number of filters can be analyzed. Glass,
quartz and PTFE filters must not have levels of Pb above the criteria
specified in section 7.7.4 and, therefore, blank correction should not
be performed. If acceptance testing shows levels of Pb above the
criteria in Section 7.7.4, corrective action must be taken to reduce the
levels before proceeding.
7.8 The Initial Calibration Verification (ICV), Lower Level
Calibration Verification (LLCV), and Continuing Calibration Verification
(CCV) solutions are prepared from a different Pb source than the
calibration curve standards and at a concentration that is either at or
below the midpoint on the calibration curve, but within the calibration
range. Both are prepared in the same acid matrix as the calibration
standards. Note that the same solution may be used for both the ICV and
CCV. The ICV/CCV and LLCV solutions must be prepared fresh daily.
[[Page 78]]
7.9 Tuning Solution. Prepare a tuning solution according to the
instrument manufacturer's recommendations. This solution will be used to
verify the mass calibration and resolution of the instrument.
8.0 Quality Control (QC)
8.1 Standard QC practices shall be employed to assess the validity
of the data generated, including: MDL, RB, duplicate samples, spiked
samples, serial dilutions, ICV, CCV, LLCV, ICB, CCB, and SRMs/CRMs.
8.2 MDLs must be calculated in accordance with 40 CFR part 136,
Appendix B. RBs with low-level standard spikes are used to estimate the
MDL. The low-level standard spike is added to at least 7 individual
filter strips and then carried through the entire extraction procedure.
This will result in at least 7 individual samples to be used for the
MDL. The recommended range for spiking the strips is 1 to 5 times the
estimated MDL.
8.3 For each batch of samples, one RB and one reagent blank spike
(RBS) that is spiked at the same level as the sample spike (see Section
8.6) must be prepared and carried throughout the entire process. The
results of the RB must be below 0.001 [micro]g/mL. The recovery for the
RBS must be within 20 percent of the expected
value. If the RB yields a result above 0.001 [micro]g/mL, the source of
contamination must be identified and the extraction and analysis
repeated. Reagents and labware must be suspected as sources of
contamination. Screening of reagents and labware is addressed in Section
4.1.
8.4 Any samples that exceed the highest calibration standard must be
diluted and rerun so that the concentration falls within the curve. The
minimum dilution will be 1 to 5 with matrix matched acid solution.
8.5 The internal standard response must be monitored during the
analysis. If the internal standard response falls below 70 percent or
rises above 120 percent of expected due to possible matrix effects, the
sample must be diluted and reanalyzed. The minimum dilution will be 1 to
5 with matrix matched acid solution. If the first dilution does not
correct the problem, additional dilutions must be run until the internal
standard falls within the specified range.
8.6 For every batch of samples prepared, there must be one duplicate
and one spike sample prepared. The spike added is to be at a level that
falls within the calibration curve, normally the midpoint of the curve.
The initial plus duplicate sample must yield a relative percent
difference <=20 percent. The spike must be within 20 percent of the expected value.
8.7 For each batch of samples, one extract must be diluted five-fold
and analyzed. The corrected dilution result must be within 10 percent of the undiluted result. The sample chosen
for the serial dilution shall have a concentration at or above 10X the
lowest standard in the curve to ensure the diluted value falls within
the curve. If the serial dilution fails, chemical or physical
interference should be suspected.
8.8 ICB, ICV, LLCV, CCB and CCV samples are to be run as shown in
the following table.
------------------------------------------------------------------------
Performance
Sample Frequency specification
------------------------------------------------------------------------
ICB....................... Prior to first sample Less than 0.001
[micro]g/mL.
ICV....................... Prior to first sample Within 90 to 110
percent of the
expected value.
LLCV...................... Daily, before first 10 percent of the
last sample. expected value.
CCB....................... After every 10 Less than 0.001
extracted samples. [micro]g/mL.
CCV....................... After every 10 Within 90-110 percent
extracted samples. of the expected
value.
------------------------------------------------------------------------
If any of these QC samples fails to meet specifications, the source
of the unacceptable performance must be determined, the problem
corrected, and any samples not bracketed by passing QC samples must be
reanalyzed.
8.9 For each batch of samples, one certified reference material
(CRM) must be combined with a blank filter strip and carried through the
entire extraction procedure. The result must be within 10 percent of the expected value.
8.10 For each run, a LLCV must be analyzed. The LLCV must be
prepared at a concentration not more than three times the lowest
calibration standard and at a concentration not used in the calibration
curve. The LLCV is used to assess performance at the low end of the
curve. If the LLCV fails (10 percent of the
expected value) the run must be terminated, the problem corrected, the
instrument recalibrated, and the analysis repeated.
8.11 Pipettes used for volumetric transfer must have the calibration
checked at least once every 6 months and pass 1
percent accuracy and <=1 percent RSD (precision) based on five replicate
readings. The pipettes must be checked weekly for accuracy with a single
replicate. Any pipette that does not meet 1
percent accuracy on the weekly check must be removed from service,
repaired, and pass a full calibration check before use.
8.12 Samples with physical deformities are not quantitatively
analyzable. The analyst should visually check filters prior to
proceeding with preparation for holes, tears, or non-uniform deposit
which would prevent
[[Page 79]]
representative sampling. Document any deformities and qualify the data
with flags appropriately. Care must be taken to protect filters from
contamination. Filters must be kept covered prior to sample preparation.
9.0 ICP MS Calibration
Follow the instrument manufacturer's instructions for the routine
maintenance, cleaning, and ignition procedures for the specific ICP-MS
instrument being used.
9.1 Ignite the plasma and wait for at least one half hour for the
instrument to warm up before beginning any pre-analysis steps.
9.2 For the Thermo X-Series with Xt cones, aspirate a 10 ng/mL
tuning solution containing In, Bi, and Ce (Cerium). Monitor the
intensities of In, Bi, Ce, and CeO (Cerium oxide) and adjust the
instrument settings to achieve the highest In and Bi counts while
minimizing the CeO/Ce oxide ratio. For other instruments, follow the
manufacturer's recommended practice. Tune to meet the instrument
manufacturer's specifications. After tuning, place the sample aspiration
probe into a 2 percent HNO3 rinse solution for at least 5
minutes to flush the system.
9.3 Aspirate a 5 ng/mL solution containing Co, In, and Bi to perform
a daily instrument stability check. Run 10 replicates of the solution.
The percent RSD for the replicates must be less than 3 percent at all
masses. If the percent RSD is greater than 3 percent, the sample
introduction system, pump tubing, and tune should be examined, and the
analysis repeated. Place the sample aspiration probe into a 2 percent
HNO3 rinse solution for at least 5 minutes to flush the
system.
9.4 Load the calibration standards in the autosampler and analyze
using the same method parameters that will be used to analyze samples.
The curve must include one blank and at least 5 Pb-containing
calibration standards. The correlation coefficient must be at least
0.998 for the curve to be accepted. The lowest standard must recover
15 percent of the expected value and the remaining
standards must recover 10 percent of the expected
value to be accepted.
9.5 Immediately after the calibration curve is completed, analyze an
ICV and an ICB. The ICV must be prepared from a different source of Pb
than the calibration standards. The ICV must recover 90-110 percent of
the expected value for the run to continue. The ICB must be less than
0.001 [micro]g/mL. If either the ICV or the ICB fails, the run must be
terminated, the problem identified and corrected, and the analysis re-
started.
9.6 A LLCV, CCV and a CCB must be run after the ICV and ICB. A CCV
and CCB must be run at a frequency of not less than every 10 extracted
samples. A typical analytical run sequence would be: Calibration blank,
Calibration standards, ICV, ICB, LLCV, CCV, CCB, Extracts 1-10, CCV,
CCB, Extracts 11-20, CCV, CCB, Extracts 21-30, CCV, CCB, LLCV, CCV, CCB.
Extracts are any field sample or QC samples that have been carried
through the extraction process. The CCV solution is prepared from a
different source than the calibration standards and may be the same as
the ICV solution. The LLCV must be within 10
percent of expected value. The CCV value must be within 10 percent of expected for the run to continue. The CCB
must be less than 0.001 [micro]g/mL. If either the CCV, LLCV, or CCB
fails, the run must be terminated, the problem identified and corrected,
and the analysis re-started from the last passing CCV/LLCV/CCB set.
9.7 A LLCV, CCV, and CCB set must be run at the end of the analysis.
The LLCV must be within 30 percent of expected
value. If either the CCV, LLCV, or CCB fails, the run must be
terminated, the problem identified and corrected, and the analysis re-
started from the last passing CCV/LLCV/CCB set.
10.0 Heated Ultrasonic Filter Strip Extraction
All plasticware (e.g., Nalgene) and glassware used in the extraction
procedures is soaked in 1 percent HNO3 (v/v) for at least 24
hours and rinsed with reagent water prior to use. All mechanical
pipettes used must be calibrated to 1 percent
accuracy and <=1 percent RSD at a minimum of once every 6 months.
10.1 Sample Preparation--Heated Ultrasonic Bath
10.1.1 Extraction solution (1.03M HNO3 + 2.23M HCl).
Prepare by adding 500 mL of deionized water to a 1000 mL flask, adding
64.4 mL of concentrated HNO3 and 182 mL of concentrated HCl,
shaking to mix, allowing solution to cool, diluting to volume with
reagent water, and inverting several times to mix. Extraction solution
must be prepared at least weekly.
10.1.2 Use a ceramic knife and non-metal ruler, or other cutting
device that will not contaminate the filter with Pb. Cut a \3/4\ inch x
8 inch strip from the glass fiber or quartz filter by cutting a strip
from the edge of the filter where it has been folded along the 10 inch
side at least 1 inch from the right or left side to avoid the un-sampled
area covered by the filter holder. The filters must be carefully handled
to avoid dislodging deposits.
10.1.3 Using plastic tweezers, roll the filter strip up in a coil
and place the rolled strip in the bottom of a labeled 50 mL extraction
tube. In a fume hood, add 15.00 0.15 mL of the
extraction solution (see Section 10.1.1) using a calibrated mechanical
pipette. Ensure that the extraction solution completely covers the
filter strip.
10.1.4 Loosely cap the 50 mL extraction tube and place it upright in
a plastic rack. When all samples have been prepared, place the racks in
an uncovered heated ultrasonic water bath that has been preheated to 80
5
[[Page 80]]
[deg]C and ensure that the water level in the ultrasonic is above the
level of the extraction solution in the tubes but well below the level
of the extraction tube caps to avoid contamination. Start the ultrasonic
bath and allow the unit to run for 1 hour 5
minutes at 80 5 [deg]C.
10.1.5 Remove the rack(s) from the ultrasonic bath and allow the
racks to cool.
10.1.6 Add 25.00 0.25 mL of D.I. water with a
calibrated mechanical pipette to bring the sample to a final volume of
40.0 0.4 mL. Tightly cap the tubes, and vortex mix
or shake vigorously. Place the extraction tubes in an appropriate holder
and centrifuge for 20 minutes at 2500 revolutions per minute (RPM).
CAUTION--Make sure that the centrifuge holder has a flat bottom to
support the flat bottomed extraction tubes.
10.1.7 Pour an aliquot of the solution into an autosampler vial for
ICP-MS analysis to avoid the potential for contamination. Do not pipette
an aliquot of solution into the autosampler vial.
10.1.8 Decant the extract to a clean tube, cap tightly, and store
the sample extract at ambient laboratory temperature. Extracts may be
stored for up to 6 months from the date of extraction.
10.2 47 mm PTFE Filter Extraction--Heated Ultrasonic Bath
10.2.1 Extraction solution (1.03M HNO3 + 2.23M HCl).
Prepare by adding 500 mL of D.I. water to a 1000mL flask, adding 64.4 mL
of concentrated HNO3 and 182 mL of concentrated HCl, shaking
to mix, allowing solution to cool, diluting to volume with reagent
water, and inverting several times to mix. Extraction solution must be
prepared at least weekly.
10.2.2 Using plastic tweezers, bend the PTFE filter into a U-shape
and insert the filter into a labeled 50 mL extraction tube with the
particle loaded side facing the center of the tube. Gently push the
filter to the bottom of the extraction tube. In a fume hood, add 25.00
0.15 mL of the extraction solution (see Section
10.2.1) using a calibrated mechanical pipette. Ensure that the
extraction solution completely covers the filter.
10.2.3 Loosely cap the 50 mL extraction tube and place it upright in
a plastic rack. When all samples have been prepared, place the racks in
an uncovered heated ultrasonic water bath that has been preheated to 80
5 [deg]C and ensure that the water level in the
ultrasonic is above the level of the extraction solution in the tubes,
but well below the level of the extraction tube caps to avoid
contamination. Start the ultrasonic bath and allow the unit to run for 1
hour 5 minutes at 80 5
[deg]C.
10.2.4 Remove the rack(s) from the ultrasonic bath and allow the
racks to cool.
10.2.5 Add 25.00 0.25 mL of D.I. water with a
calibrated mechanical pipette to bring the sample to a final volume of
50.0 0.4 mL. Tightly cap the tubes, and vortex mix
or shake vigorously. Allow samples to stand for one hour to allow
complete diffusion of the extracted Pb. The sample is now ready for
analysis.
Note: Although PTFE filters have only been extracted using the
ultrasonic extraction procedure in the development of this FRM, PTFE
filters are inert and have very low Pb content. No issues are expected
with the extraction of PTFE filters using the heated block digestion
method. However, prior to using PTFE filters in the heated block
extraction method, extraction method performance test using CRMs must be
done to confirm performance (see Section 8.9).
11.0 Hot Block Filter Strip Extraction
All plasticware (e.g., Nalgene) and glassware used in the extraction
procedures is soaked in 1 percent HNO3 for at least 24 hours
and rinsed with reagent water prior to use. All mechanical pipettes used
must be calibrated to 1 percent accuracy and <=1
percent RSD at a minimum of once every 6 months.
11.1 Sample Preparation--Hot Block Digestion
11.1.1 Extraction solution (1:19, v/v HNO3). Prepare by
adding 500 mL of D.I. water to a 1000 mL flask, adding 50 mL of
concentrated HNO3, shaking to mix, allowing solution to cool,
diluting to volume with reagent water, and inverting several times to
mix. The extraction solution must be prepared at least weekly.
11.1.2 Use a ceramic knife and non-metal ruler, or other cutting
device that will not contaminate the filter with Pb. Cut a 1-inch x 8-
inch strip from the glass fiber or quartz filter. Cut a strip from the
edge of the filter where it has been folded along the 10-inch side at
least 1 inch from the right or left side to avoid the un-sampled area
covered by the filter holder. The filters must be carefully handled to
avoid dislodging particle deposits.
11.1.3 Using plastic tweezers, roll the filter strip up in a coil
and place the rolled strip in the bottom of a labeled 50 mL extraction
tube. In a fume hood, add 20.0 0.15 mL of the
extraction solution (see Section 11.1.1) using a calibrated mechanical
pipette. Ensure that the extraction solution completely covers the
filter strip.
11.1.4 Place the extraction tube in the heated block digester and
cover with a disposable polyethylene ribbed watch glass. Heat at 95
5 [deg]C for 1 hour and ensure that the sample
does not evaporate to dryness. For proper heating, adjust the
temperature control of the hot block such that an uncovered vessel
containing 50 mL of water placed in the center of the hot block can be
maintained at a temperature approximately, but
[[Page 81]]
no higher than 85C. Once the vessel is covered with a ribbed watch
glass, the temperature of the water will increase to approximately 95
[deg]C.
11.1.5 Remove the rack(s) from the heated block digester and allow
the samples to cool.
11.1.6 Bring the samples to a final volume of 50 mL with D.I. water.
Tightly cap the tubes, and vortex mix or shake vigorously for at least 5
seconds. Set aside (with the filter strip in the tube) for at least 30
minutes to allow the HNO3 trapped in the filter to diffuse
into the extraction solution.
11.1.7 Shake thoroughly (with the filter strip in the digestion
tube) and let settle for at least one hour. The sample is now ready for
analysis.
12.0 Measurement Procedure
12.1 Follow the instrument manufacturer's startup procedures for the
ICP-MS.
12.2 Set instrument parameters to the appropriate operating
conditions as presented in the instrument manufacturer's operating
manual and allow the instrument to warm up for at least 30 minutes.
12.3 Calibrate the instrument per Section 9.0 of this method.
12.4 Verify the instrument is suitable for analysis as defined in
Sections 9.2 and 9.3.
12.5 As directed in Section 8.0 of this method, analyze an ICV and
ICB immediately after the calibration curve followed by a LLCV, then CCV
and CCB. The acceptance requirements for these parameters are presented
in Section 8.8.
12.6 Analyze a CCV and a CCB after every 10 extracted samples.
12.7 Analyze a LLCV, CCV and CCB at the end of the analysis.
12.8 A typical sample run will include field samples, field sample
duplicates, spiked field sample extracts, serially diluted samples, the
set of QC samples listed in Section 8.8 above, and one or more CRMs or
SRMs.
12.9 Any samples that exceed the highest standard in the calibration
curve must be diluted and reanalyzed so that the diluted concentration
falls within the calibration curve.
13.0 Results
13.1 The filter results must be initially reported in [micro]g/mL as
analyzed. Any additional dilutions must be accounted for. The internal
standard recoveries must be included in the result calculation; this is
done by the ICP-MS software for most commercially-available instruments.
Final results should be reported in [micro]g Pb/m\3\ to three
significant figures as follows:
C = (([micro]g Pb/mL * Vf * A)* D))/Vs
Where:
C = Concentration, [micro]g Pb/m\3\
[micro]g Pb/mL = Lead concentration in solution
Vf = Total extraction solution volume
A = Area correction; \3/4\ x 8 strip = 5.25 in\2\
analyzed, A = 12.0 or 1 x 8 strip = 7
in\2\ analyzed, A = 9.0
D = dilution factor (if required)
Vs = Actual volume of air sampled
The calculation assumes the use of a standard 8-inch x 10-inch TSP
filter which has a sampled area of 9-inch x 7-inch (63.0 in\2\) due to
the \1/2\-inch filter holder border around the outer edge. The \3/4\-
inch x 8-inch strip has a sampled area of \3/4\-inch x 7-inch (5.25
in\2\). The 1-inch x 8-inch strip has a sampled area of 1-inch x 7-inch
(7.0 in\2\). If filter lot blanks are provided for analysis, refer to
Section 7.7.5 of this method for guidance on testing.
14.0 Method Performance
Information in this section is an example of typical performance
results achieved by this method. Actual performance must be demonstrated
by each individual laboratory and instrument.
14.1 Performance data have been collected to estimate MDLs for this
method. MDLs were determined in accordance with 40 CFR 136, Appendix B.
MDLs were estimated for glass fiber, quartz, and PTFE filters using
seven reagent/filter blank solutions spiked with low level Pb at three
times the estimated MDL of 0.001 [micro]g/mL. Tables 1, 3, and 5 shows
the MDLs estimated using both the ultrasonic and hot block extraction
methods for glass fiber and quartz filters and the ultrasonic method for
PTFE filters. The MDLs are well below the EPA requirement of five
percent of the current Pb NAAQS or 0.0075 [micro]g/m\3\. These MDLs are
provided to demonstrate the adequacy of the method's performance for Pb
in TSP. Each laboratory using this method should determine MDLs in their
laboratory and verify them annually. It is recommended that laboratories
also perform the optional iterative procedure in 40 CFR 136, Appendix B
to verify the reasonableness of the estimated MDL and subsequent MDL
determinations.
14.2 Extraction method recovery tests with glass fiber and quartz
filter strips, and PTFE filters spiked with NIST SRMs were performed
using the ultrasonic/HNO3 and HCl filter extraction methods
and measurement of the dissolved Pb with ICP-MS. Tables 2, 4, and 6 show
recoveries obtained with these SRM. The recoveries for all SRMs were
=90 percent at the 95 percent confidence level.
[[Page 82]]
Table 1--Method Detection Limits Determined by Analysis of Reagent/Glass
Fiber Filter Blanks Spiked With Low-level Pb Solution
------------------------------------------------------------------------
Ultrasonic Hotblock
extraction extraction
method method
-------------------------
[micro]g/ [micro]g/
m\3\* m\3\*
------------------------------------------------------------------------
n = 1......................................... 0.0000702 0.000533
n = 2......................................... 0.0000715 0.000482
n = 3......................................... 0.0000611 0.000509
n = 4......................................... 0.0000587 0.000427
n = 5......................................... 0.0000608 0.000449
n = 6......................................... 0.0000607 0.000539
n = 7......................................... 0.0000616 0.000481
Average....................................... 0.0000635 0.000489
Standard Deviation............................ 0.0000051 0.000042
MDL**......................................... 0.0000161 0.000131
------------------------------------------------------------------------
* Assumes 2000 m\3\ of air sampled.
** MDL is 3.143 times the standard deviation of the results for seven
sample replicates analyzed.
Table 2--Recoveries of Lead From NIST SRMs Spiked Onto Glass Fiber Filters
----------------------------------------------------------------------------------------------------------------
Recovery, ICP-MS, (percent)
---------------------------------------------------------------
Extraction method NIST 1547 NIST 2582
plant NIST 2709 soil NIST 2583 dust paint
----------------------------------------------------------------------------------------------------------------
Ultrasonic Bath................................. 100 3, HCl, and solutions containing these
reagents and/or Pb must be placed in labeled bottles and delivered to a
commercial firm that specializes in removal of hazardous waste.
17.0 References
FACDQ (2007). Report of the Federal Advisory Committee on Detection and
Quantitation Approaches and Uses in Clean Water Act Programs,
submitted to the U.S. EPA December 2007. Available: http://
water.epa.gov/scitech/methods/cwa/det/upload/final-report-
200712.pdf.
Rice J (2013). Results from the Development of a New Federal Reference
Method (FRM) for Lead in Total Suspended Particulate (TSP)
Matter. Docket EPA-HQ-OAR-2012-0210.
U.S. EPA (2007). Method 6020A--Inductively Coupled Plasma Mass
Spectrometry. U.S. Environmental Protection Agency. Revision
1, February 2007. Available: http://www.epa.gov/osw/hazard/
testmethods/sw846/pdfs/6020a.pdf.
U.S. EPA (2011). A Laboratory Study of Procedures Evaluated by the
Federal Advisory Committee on Detection and Quantitation
Approaches and Uses in Clean Water Act Programs. December
2011. Available: http://water.epa.gov/scitech/methods/cwa/det/
upload/fac_report_2009.pdf.
[78 FR 40004, July 3, 2013]
[[Page 84]]
Sec. Appendix H to Part 50--Interpretation of the 1-Hour Primary and
Secondary National Ambient Air Quality Standards for Ozone
1. General
This appendix explains how to determine when the expected number of
days per calendar year with maximum hourly average concentrations above
0.12 ppm (235 [micro]g/m\3\) is equal to or less than 1. An expanded
discussion of these procedures and associated examples are contained in
the ``Guideline for Interpretation of Ozone Air Quality Standards.'' For
purposes of clarity in the following discussion, it is convenient to use
the term ``exceedance'' to describe a daily maximum hourly average ozone
measurement that is greater than the level of the standard. Therefore,
the phrase ``expected number of days with maximum hourly average ozone
concentrations above the level of the standard'' may be simply stated as
the ``expected number of exceedances.''
The basic principle in making this determination is relatively
straightforward. Most of the complications that arise in determining the
expected number of annual exceedances relate to accounting for
incomplete sampling. In general, the average number of exceedances per
calendar year must be less than or equal to 1. In its simplest form, the
number of exceedances at a monitoring site would be recorded for each
calendar year and then averaged over the past 3 calendar years to
determine if this average is less than or equal to 1.
2. Interpretation of Expected Exceedances
The ozone standard states that the expected number of exceedances
per year must be less than or equal to 1. The statistical term
``expected number'' is basically an arithmetic average. The following
example explains what it would mean for an area to be in compliance with
this type of standard. Suppose a monitoring station records a valid
daily maximum hourly average ozone value for every day of the year
during the past 3 years. At the end of each year, the number of days
with maximum hourly concentrations above 0.12 ppm is determined and this
number is averaged with the results of previous years. As long as this
average remains ``less than or equal to 1,'' the area is in compliance.
3. Estimating the Number of Exceedances for a Year
In general, a valid daily maximum hourly average value may not be
available for each day of the year, and it will be necessary to account
for these missing values when estimating the number of exceedances for a
particular calendar year. The purpose of these computations is to
determine if the expected number of exceedances per year is less than or
equal to 1. Thus, if a site has two or more observed exceedances each
year, the standard is not met and it is not necessary to use the
procedures of this section to account for incomplete sampling.
The term ``missing value'' is used here in the general sense to
describe all days that do not have an associated ozone measurement. In
some cases, a measurement might actually have been missed but in other
cases no measurement may have been scheduled for that day. A daily
maximum ozone value is defined to be the highest hourly ozone value
recorded for the day. This daily maximum value is considered to be valid
if 75 percent of the hours from 9:01 a.m. to 9:00 p.m. (LST) were
measured or if the highest hour is greater than the level of the
standard.
In some areas, the seasonal pattern of ozone is so pronounced that
entire months need not be sampled because it is extremely unlikely that
the standard would be exceeded. Any such waiver of the ozone monitoring
requirement would be handled under provisions of 40 CFR, part 58. Some
allowance should also be made for days for which valid daily maximum
hourly values were not obtained but which would quite likely have been
below the standard. Such an allowance introduces a complication in that
it becomes necessary to define under what conditions a missing value may
be assumed to have been less than the level of the standard. The
following criterion may be used for ozone:
A missing daily maximum ozone value may be assumed to be less than
the level of the standard if the valid daily maxima on both the
preceding day and the following day do not exceed 75 percent of the
level of the standard.
Let z denote the number of missing daily maximum values that may be
assumed to be less than the standard. Then the following formula shall
be used to estimate the expected number of exceedances for the year:
[GRAPHIC] [TIFF OMITTED] TC08NO91.086
(*Indicates multiplication.)
where:
e = the estimated number of exceedances for the year,
N = the number of required monitoring days in the year,
n = the number of valid daily maxima,
v = the number of daily values above the level of the standard, and
z = the number of days assumed to be less than the standard level.
This estimated number of exceedances shall be rounded to one decimal
place (fractional parts equal to 0.05 round up).
[[Page 85]]
It should be noted that N will be the total number of days in the
year unless the appropriate Regional Administrator has granted a waiver
under the provisions of 40 CFR part 58.
The above equation may be interpreted intuitively in the following
manner. The estimated number of exceedances is equal to the observed
number of exceedances (v) plus an increment that accounts for incomplete
sampling. There were (N-n) missing values for the year but a certain
number of these, namely z, were assumed to be less than the standard.
Therefore, (N-n-z) missing values are considered to include possible
exceedances. The fraction of measured values that are above the level of
the standard is v/n. It is assumed that this same fraction applies to
the (N-n-z) missing values and that (v/n)*(N-n-z) of these values would
also have exceeded the level of the standard.
[44 FR 8220, Feb. 8, 1979, as amended at 62 FR 38895, July 18, 1997]
Sec. Appendix I to Part 50--Interpretation of the 8-Hour Primary and
Secondary National Ambient Air Quality Standards for Ozone
1. General.
This appendix explains the data handling conventions and
computations necessary for determining whether the national 8-hour
primary and secondary ambient air quality standards for ozone specified
in Sec. 50.10 are met at an ambient ozone air quality monitoring site.
Ozone is measured in the ambient air by a reference method based on
appendix D of this part. Data reporting, data handling, and computation
procedures to be used in making comparisons between reported ozone
concentrations and the level of the ozone standard are specified in the
following sections. Whether to exclude, retain, or make adjustments to
the data affected by stratospheric ozone intrusion or other natural
events is subject to the approval of the appropriate Regional
Administrator.
2. Primary and Secondary Ambient Air Quality Standards for Ozone.
2.1 Data Reporting and Handling Conventions.
2.1.1 Computing 8-hour averages. Hourly average concentrations shall
be reported in parts per million (ppm) to the third decimal place, with
additional digits to the right being truncated. Running 8-hour averages
shall be computed from the hourly ozone concentration data for each hour
of the year and the result shall be stored in the first, or start, hour
of the 8-hour period. An 8-hour average shall be considered valid if at
least 75% of the hourly averages for the 8-hour period are available. In
the event that only 6 (or 7) hourly averages are available, the 8-hour
average shall be computed on the basis of the hours available using 6
(or 7) as the divisor. (8-hour periods with three or more missing hours
shall not be ignored if, after substituting one-half the minimum
detectable limit for the missing hourly concentrations, the 8-hour
average concentration is greater than the level of the standard.) The
computed 8-hour average ozone concentrations shall be reported to three
decimal places (the insignificant digits to the right of the third
decimal place are truncated, consistent with the data handling
procedures for the reported data.)
2.1.2 Daily maximum 8-hour average concentrations. (a) There are 24
possible running 8-hour average ozone concentrations for each calendar
day during the ozone monitoring season. (Ozone monitoring seasons vary
by geographic location as designated in part 58, appendix D to this
chapter.) The daily maximum 8-hour concentration for a given calendar
day is the highest of the 24 possible 8-hour average concentrations
computed for that day. This process is repeated, yielding a daily
maximum 8-hour average ozone concentration for each calendar day with
ambient ozone monitoring data. Because the 8-hour averages are recorded
in the start hour, the daily maximum 8-hour concentrations from two
consecutive days may have some hourly concentrations in common.
Generally, overlapping daily maximum 8-hour averages are not likely,
except in those non-urban monitoring locations with less pronounced
diurnal variation in hourly concentrations.
(b) An ozone monitoring day shall be counted as a valid day if valid
8-hour averages are available for at least 75% of possible hours in the
day (i.e., at least 18 of the 24 averages). In the event that less than
75% of the 8-hour averages are available, a day shall also be counted as
a valid day if the daily maximum 8-hour average concentration for that
day is greater than the level of the ambient standard.
2.2 Primary and Secondary Standard-related Summary Statistic. The
standard-related summary statistic is the annual fourth-highest daily
maximum 8-hour ozone concentration, expressed in parts per million,
averaged over three years. The 3-year average shall be computed using
the three most recent, consecutive calendar years of monitoring data
meeting the data completeness requirements described in this appendix.
The computed 3-year average of the annual fourth-highest daily maximum
8-hour average ozone concentrations shall be expressed to three decimal
places (the remaining digits to the right are truncated.)
2.3 Comparisons with the Primary and Secondary Ozone Standards. (a)
The primary and secondary ozone ambient air quality standards are met at
an ambient air quality monitoring site when the 3-year average of the
annual fourth-highest daily maximum 8-hour
[[Page 86]]
average ozone concentration is less than or equal to 0.08 ppm. The
number of significant figures in the level of the standard dictates the
rounding convention for comparing the computed 3-year average annual
fourth-highest daily maximum 8-hour average ozone concentration with the
level of the standard. The third decimal place of the computed value is
rounded, with values equal to or greater than 5 rounding up. Thus, a
computed 3-year average ozone concentration of 0.085 ppm is the smallest
value that is greater than 0.08 ppm.
(b) This comparison shall be based on three consecutive, complete
calendar years of air quality monitoring data. This requirement is met
for the three year period at a monitoring site if daily maximum 8-hour
average concentrations are available for at least 90%, on average, of
the days during the designated ozone monitoring season, with a minimum
data completeness in any one year of at least 75% of the designated
sampling days. When computing whether the minimum data completeness
requirements have been met, meteorological or ambient data may be
sufficient to demonstrate that meteorological conditions on missing days
were not conducive to concentrations above the level of the standard.
Missing days assumed less than the level of the standard are counted for
the purpose of meeting the data completeness requirement, subject to the
approval of the appropriate Regional Administrator.
(c) Years with concentrations greater than the level of the standard
shall not be ignored on the ground that they have less than complete
data. Thus, in computing the 3-year average fourth maximum
concentration, calendar years with less than 75% data completeness shall
be included in the computation if the average annual fourth maximum 8-
hour concentration is greater than the level of the standard.
(d) Comparisons with the primary and secondary ozone standards are
demonstrated by examples 1 and 2 in paragraphs (d)(1) and (d) (2)
respectively as follows:
(1) As shown in example 1, the primary and secondary standards are
met at this monitoring site because the 3-year average of the annual
fourth-highest daily maximum 8-hour average ozone concentrations (i.e.,
0.084 ppm) is less than or equal to 0.08 ppm. The data completeness
requirement is also met because the average percent of days with valid
ambient monitoring data is greater than 90%, and no single year has less
than 75% data completeness.
Example 1. Ambient monitoring site attaining the primary and secondary ozone standards
----------------------------------------------------------------------------------------------------------------
1st Highest 2nd Highest 3rd Highest 4th Highest 5th Highest
Percent Daily Max 8- Daily Max 8- Daily Max 8- Daily Max 8- Daily Max 8-
Year Valid Days hour Conc. hour Conc. hour Conc. hour Conc. hour Conc.
(ppm) (ppm) (ppm) (ppm) (ppm)
----------------------------------------------------------------------------------------------------------------
1993.............................. 100% 0.092 0.091 0.090 0.088 0.085
----------------------------------------------------------------------------------------------------------------
1994.............................. 96% 0.090 0.089 0.086 0.084 0.080
----------------------------------------------------------------------------------------------------------------
1995.............................. 98% 0.087 0.085 0.083 0.080 0.075
================================================================================================================
Average....................... 98%
----------------------------------------------------------------------------------------------------------------
(2) As shown in example 2, the primary and secondary standards are
not met at this monitoring site because the 3-year average of the
fourth-highest daily maximum 8-hour average ozone concentrations (i.e.,
0.093 ppm) is greater than 0.08 ppm. Note that the ozone concentration
data for 1994 is used in these computations, even though the data
capture is less than 75%, because the average fourth-highest daily
maximum 8-hour average concentration is greater than 0.08 ppm.
Example 2. Ambient Monitoring Site Failing to Meet the Primary and Secondary Ozone Standards
----------------------------------------------------------------------------------------------------------------
1st Highest 2nd Highest 3rd Highest 4th Highest 5th Highest
Percent Daily Max 8- Daily Max 8- Daily Max 8- Daily Max 8- Daily Max 8-
Year Valid Days hour Conc. hour Conc. hour Conc. hour Conc. hour Conc.
(ppm) (ppm) (ppm) (ppm) (ppm)
----------------------------------------------------------------------------------------------------------------
1993.............................. 96% 0.105 0.103 0.103 0.102 0.102
----------------------------------------------------------------------------------------------------------------
1994.............................. 74% 0.090 0.085 0.082 0.080 0.078
----------------------------------------------------------------------------------------------------------------
1995.............................. 98% 0.103 0.101 0.101 0.097 0.095
================================================================================================================
Average....................... 89%
----------------------------------------------------------------------------------------------------------------
[[Page 87]]
3. Design Values for Primary and Secondary Ambient Air Quality
Standards for Ozone. The air quality design value at a monitoring site
is defined as that concentration that when reduced to the level of the
standard ensures that the site meets the standard. For a concentration-
based standard, the air quality design value is simply the standard-
related test statistic. Thus, for the primary and secondary ozone
standards, the 3-year average annual fourth-highest daily maximum 8-hour
average ozone concentration is also the air quality design value for the
site.
[62 FR 38895, July 18, 1997]
Sec. Appendix J to Part 50--Reference Method for the Determination of
Particulate Matter as PM10 in the Atmosphere
1.0 Applicability.
1.1 This method provides for the measurement of the mass
concentration of particulate matter with an aerodynamic diameter less
than or equal to a nominal 10 micrometers (PM1O) in ambient
air over a 24-hour period for purposes of determining attainment and
maintenance of the primary and secondary national ambient air quality
standards for particulate matter specified in Sec. 50.6 of this
chapter. The measurement process is nondestructive, and the
PM10 sample can be subjected to subsequent physical or
chemical analyses. Quality assurance procedures and guidance are
provided in part 58, appendices A and B, of this chapter and in
References 1 and 2.
2.0 Principle.
2.1 An air sampler draws ambient air at a constant flow rate into a
specially shaped inlet where the suspended particulate matter is
inertially separated into one or more size fractions within the
PM10 size range. Each size fraction in the PM1O
size range is then collected on a separate filter over the specified
sampling period. The particle size discrimination characteristics
(sampling effectiveness and 50 percent cutpoint) of the sampler inlet
are prescribed as performance specifications in part 53 of this chapter.
2.2 Each filter is weighed (after moisture equilibration) before and
after use to determine the net weight (mass) gain due to collected
PM10. The total volume of air sampled, corrected to EPA
reference conditions (25 C, 101.3 kPa), is determined from the measured
flow rate and the sampling time. The mass concentration of
PM10 in the ambient air is computed as the total mass of
collected particles in the PM10 size range divided by the
volume of air sampled, and is expressed in micrograms per standard cubic
meter ([micro]g/std m\3\). For PM10 samples collected at
temperatures and pressures significantly different from EPA reference
conditions, these corrected concentrations sometimes differ
substantially from actual concentrations (in micrograms per actual cubic
meter), particularly at high elevations. Although not required, the
actual PM10 concentration can be calculated from the
corrected concentration, using the average ambient temperature and
barometric pressure during the sampling period.
2.3 A method based on this principle will be considered a reference
method only if (a) the associated sampler meets the requirements
specified in this appendix and the requirements in part 53 of this
chapter, and (b) the method has been designated as a reference method in
accordance with part 53 of this chapter.
3.0 Range.
3.1 The lower limit of the mass concentration range is determined by
the repeatability of filter tare weights, assuming the nominal air
sample volume for the sampler. For samplers having an automatic filter-
changing mechanism, there may be no upper limit. For samplers that do
not have an automatic filter-changing mechanism, the upper limit is
determined by the filter mass loading beyond which the sampler no longer
maintains the operating flow rate within specified limits due to
increased pressure drop across the loaded filter. This upper limit
cannot be specified precisely because it is a complex function of the
ambient particle size distribution and type, humidity, filter type, and
perhaps other factors. Nevertheless, all samplers should be capable of
measuring 24-hour PM10 mass concentrations of at least 300
[micro]g/std m\3\ while maintaining the operating flow rate within the
specified limits.
4.0 Precision.
4.1 The precision of PM10 samplers must be 5 [micro]g/
m\3\ for PM10 concentrations below 80 [micro]g/m\3\ and 7
percent for PM10 concentrations above 80 [micro]g/m\3\, as
required by part 53 of this chapter, which prescribes a test procedure
that determines the variation in the PM10 concentration
measurements of identical samplers under typical sampling conditions.
Continual assessment of precision via collocated samplers is required by
part 58 of this chapter for PM10 samplers used in certain
monitoring networks.
5.0 Accuracy.
5.1 Because the size of the particles making up ambient particulate
matter varies over a wide range and the concentration of particles
varies with particle size, it is difficult to define the absolute
accuracy of PM10 samplers. Part 53 of this chapter provides a
specification for the sampling effectiveness of PM10
samplers. This specification requires that the expected mass
concentration calculated for a candidate PM10 sampler, when
sampling a specified particle size distribution, be within 10 percent of that calculated
[[Page 88]]
for an ideal sampler whose sampling effectiveness is explicitly
specified. Also, the particle size for 50 percent sampling effectiveness
is required to be 10 0.5 micrometers. Other
specifications related to accuracy apply to flow measurement and
calibration, filter media, analytical (weighing) procedures, and
artifact. The flow rate accuracy of PM10 samplers used in
certain monitoring networks is required by part 58 of this chapter to be
assessed periodically via flow rate audits.
6.0 Potential Sources of Error.
6.1 Volatile Particles. Volatile particles collected on filters are
often lost during shipment and/or storage of the filters prior to the
post-sampling weighing \3\. Although shipment or storage of loaded
filters is sometimes unavoidable, filters should be reweighed as soon as
practical to minimize these losses.
6.2 Artifacts. Positive errors in PM10 concentration
measurements may result from retention of gaseous species on filters. \4
5\ Such errors include the retention of sulfur dioxide and nitric acid.
Retention of sulfur dioxide on filters, followed by oxidation to
sulfate, is referred to as artifact sulfate formation, a phenomenon
which increases with increasing filter alkalinity. \6\ Little or no
artifact sulfate formation should occur using filters that meet the
alkalinity specification in section 7.2.4. Artifact nitrate formation,
resulting primarily from retention of nitric acid, occurs to varying
degrees on many filter types, including glass fiber, cellulose ester,
and many quartz fiber filters. \5 7 8 9 10\ Loss of true atmospheric
particulate nitrate during or following sampling may also occur due to
dissociation or chemical reaction. This phenomenon has been observed on
Teflon [supreg] filters \8\ and inferred for quartz fiber filters. \11
12\ The magnitude of nitrate artifact errors in PM10 mass
concentration measurements will vary with location and ambient
temperature; however, for most sampling locations, these errors are
expected to be small.
6.3 Humidity. The effects of ambient humidity on the sample are
unavoidable. The filter equilibration procedure in section 9.0 is
designed to minimize the effects of moisture on the filter medium.
6.4 Filter Handling. Careful handling of filters between presampling
and postsampling weighings is necessary to avoid errors due to damaged
filters or loss of collected particles from the filters. Use of a filter
cartridge or cassette may reduce the magnitude of these errors. Filters
must also meet the integrity specification in section 7.2.3.
6.5 Flow Rate Variation. Variations in the sampler's operating flow
rate may alter the particle size discrimination characteristics of the
sampler inlet. The magnitude of this error will depend on the
sensitivity of the inlet to variations in flow rate and on the particle
distribution in the atmosphere during the sampling period. The use of a
flow control device (section 7.1.3) is required to minimize this error.
6.6 Air Volume Determination. Errors in the air volume determination
may result from errors in the flow rate and/or sampling time
measurements. The flow control device serves to minimize errors in the
flow rate determination, and an elapsed time meter (section 7.1.5) is
required to minimize the error in the sampling time measurement.
7.0 Apparatus.
7.1 PM10 Sampler.
7.1.1 The sampler shall be designed to:
a. Draw the air sample into the sampler inlet and through the
particle collection filter at a uniform face velocity.
b. Hold and seal the filter in a horizontal position so that sample
air is drawn downward through the filter.
c. Allow the filter to be installed and removed conveniently.
d. Protect the filter and sampler from precipitation and prevent
insects and other debris from being sampled.
e. Minimize air leaks that would cause error in the measurement of
the air volume passing through the filter.
f. Discharge exhaust air at a sufficient distance from the sampler
inlet to minimize the sampling of exhaust air.
g. Minimize the collection of dust from the supporting surface.
7.1.2 The sampler shall have a sample air inlet system that, when
operated within a specified flow rate range, provides particle size
discrimination characteristics meeting all of the applicable performance
specifications prescribed in part 53 of this chapter. The sampler inlet
shall show no significant wind direction dependence. The latter
requirement can generally be satisfied by an inlet shape that is
circularly symmetrical about a vertical axis.
7.1.3 The sampler shall have a flow control device capable of
maintaining the sampler's operating flow rate within the flow rate
limits specified for the sampler inlet over normal variations in line
voltage and filter pressure drop.
7.1.4 The sampler shall provide a means to measure the total flow
rate during the sampling period. A continuous flow recorder is
recommended but not required. The flow measurement device shall be
accurate to 2 percent.
7.1.5 A timing/control device capable of starting and stopping the
sampler shall be used to obtain a sample collection period of 24 1 hr (1,440 60 min). An elapsed
time meter, accurate to within 15 minutes, shall
be used to measure sampling time. This meter is optional for samplers
with continuous flow recorders if the sampling time
[[Page 89]]
measurement obtained by means of the recorder meets the 15 minute accuracy specification.
7.1.6 The sampler shall have an associated operation or instruction
manual as required by part 53 of this chapter which includes detailed
instructions on the calibration, operation, and maintenance of the
sampler.
7.2 Filters.
7.2.1 Filter Medium. No commercially available filter medium is
ideal in all respects for all samplers. The user's goals in sampling
determine the relative importance of various filter characteristics
(e.g., cost, ease of handling, physical and chemical characteristics,
etc.) and, consequently, determine the choice among acceptable filters.
Furthermore, certain types of filters may not be suitable for use with
some samplers, particularly under heavy loading conditions (high mass
concentrations), because of high or rapid increase in the filter flow
resistance that would exceed the capability of the sampler's flow
control device. However, samplers equipped with automatic filter-
changing mechanisms may allow use of these types of filters. The
specifications given below are minimum requirements to ensure
acceptability of the filter medium for measurement of PM10
mass concentrations. Other filter evaluation criteria should be
considered to meet individual sampling and analysis objectives.
7.2.2 Collection Efficiency. =99 percent, as measured by
the DOP test (ASTM-2986) with 0.3 [micro]m particles at the sampler's
operating face velocity.
7.2.3 Integrity. 5 [micro]g/m\3\ (assuming
sampler's nominal 24-hour air sample volume). Integrity is measured as
the PM10 concentration equivalent corresponding to the
average difference between the initial and the final weights of a random
sample of test filters that are weighed and handled under actual or
simulated sampling conditions, but have no air sample passed through
them (i.e., filter blanks). As a minimum, the test procedure must
include initial equilibration and weighing, installation on an
inoperative sampler, removal from the sampler, and final equilibration
and weighing.
7.2.4 Alkalinity. <25 microequivalents/gram of filter, as measured
by the procedure given in Reference 13 following at least two months
storage in a clean environment (free from contamination by acidic gases)
at room temperature and humidity.
7.3 Flow Rate Transfer Standard. The flow rate transfer standard
must be suitable for the sampler's operating flow rate and must be
calibrated against a primary flow or volume standard that is traceable
to the National Bureau of Standards (NBS). The flow rate transfer
standard must be capable of measuring the sampler's operating flow rate
with an accuracy of 2 percent.
7.4 Filter Conditioning Environment.
7.4.1 Temperature range: 15 to 30 C.
7.4.2 Temperature control: 3 C.
7.4.3 Humidity range: 20% to 45% RH.
7.4.4 Humidity control: 5% RH.
7.5 Analytical Balance. The analytical balance must be suitable for
weighing the type and size of filters required by the sampler. The range
and sensitivity required will depend on the filter tare weights and mass
loadings. Typically, an analytical balance with a sensitivity of 0.1 mg
is required for high volume samplers (flow rates 0.5 m\3\/
min). Lower volume samplers (flow rates <0.5 m\3\/min) will require a
more sensitive balance.
8.0 Calibration.
8.1 General Requirements.
8.1.1 Calibration of the sampler's flow measurement device is
required to establish traceability of subsequent flow measurements to a
primary standard. A flow rate transfer standard calibrated against a
primary flow or volume standard shall be used to calibrate or verify the
accuracy of the sampler's flow measurement device.
8.1.2 Particle size discrimination by inertial separation requires
that specific air velocities be maintained in the sampler's air inlet
system. Therefore, the flow rate through the sampler's inlet must be
maintained throughout the sampling period within the design flow rate
range specified by the manufacturer. Design flow rates are specified as
actual volumetric flow rates, measured at existing conditions of
temperature and pressure (Qa). In contrast, mass
concentrations of PM10 are computed using flow rates
corrected to EPA reference conditions of temperature and pressure
(Qstd).
8.2 Flow Rate Calibration Procedure.
8.2.1 PM10 samplers employ various types of flow control
and flow measurement devices. The specific procedure used for flow rate
calibration or verification will vary depending on the type of flow
controller and flow indicator employed. Calibration in terms of actual
volumetric flow rates (Qa) is generally recommended, but
other measures of flow rate (e.g., Qstd) may be used provided
the requirements of section 8.1 are met. The general procedure given
here is based on actual volumetric flow units (Qa) and serves
to illustrate the steps involved in the calibration of a PM10
sampler. Consult the sampler manufacturer's instruction manual and
Reference 2 for specific guidance on calibration. Reference 14 provides
additional information on the use of the commonly used measures of flow
rate and their interrelationships.
8.2.2 Calibrate the flow rate transfer standard against a primary
flow or volume standard traceable to NBS. Establish a calibration
relationship (e.g., an equation or family of curves) such that
traceability to the primary standard is accurate to within 2 percent
over the expected range of ambient conditions (i.e., temperatures and
pressures) under
[[Page 90]]
which the transfer standard will be used. Recalibrate the transfer
standard periodically.
8.2.3 Following the sampler manufacturer's instruction manual,
remove the sampler inlet and connect the flow rate transfer standard to
the sampler such that the transfer standard accurately measures the
sampler's flow rate. Make sure there are no leaks between the transfer
standard and the sampler.
8.2.4 Choose a minimum of three flow rates (actual m\3\/min), spaced
over the acceptable flow rate range specified for the inlet (see 7.1.2)
that can be obtained by suitable adjustment of the sampler flow rate. In
accordance with the sampler manufacturer's instruction manual, obtain or
verify the calibration relationship between the flow rate (actual m\3\/
min) as indicated by the transfer standard and the sampler's flow
indicator response. Record the ambient temperature and barometric
pressure. Temperature and pressure corrections to subsequent flow
indicator readings may be required for certain types of flow measurement
devices. When such corrections are necessary, correction on an
individual or daily basis is preferable. However, seasonal average
temperature and average barometric pressure for the sampling site may be
incorporated into the sampler calibration to avoid daily corrections.
Consult the sampler manufacturer's instruction manual and Reference 2
for additional guidance.
8.2.5 Following calibration, verify that the sampler is operating at
its design flow rate (actual m\3\/min) with a clean filter in place.
8.2.6 Replace the sampler inlet.
9.0 Procedure.
9.1 The sampler shall be operated in accordance with the specific
guidance provided in the sampler manufacturer's instruction manual and
in Reference 2. The general procedure given here assumes that the
sampler's flow rate calibration is based on flow rates at ambient
conditions (Qa) and serves to illustrate the steps involved
in the operation of a PM10 sampler.
9.2 Inspect each filter for pinholes, particles, and other
imperfections. Establish a filter information record and assign an
identification number to each filter.
9.3 Equilibrate each filter in the conditioning environment (see
7.4) for at least 24 hours.
9.4 Following equilibration, weigh each filter and record the
presampling weight with the filter identification number.
9.5 Install a preweighed filter in the sampler following the
instructions provided in the sampler manufacturer's instruction manual.
9.6 Turn on the sampler and allow it to establish run-temperature
conditions. Record the flow indicator reading and, if needed, the
ambient temperature and barometric pressure. Determine the sampler flow
rate (actual m\3\/min) in accordance with the instructions provided in
the sampler manufacturer's instruction manual. NOTE.--No onsite
temperature or pressure measurements are necessary if the sampler's flow
indicator does not require temperature or pressure corrections or if
seasonal average temperature and average barometric pressure for the
sampling site are incorporated into the sampler calibration (see step
8.2.4). If individual or daily temperature and pressure corrections are
required, ambient temperature and barometric pressure can be obtained by
on-site measurements or from a nearby weather station. Barometric
pressure readings obtained from airports must be station pressure, not
corrected to sea level, and may need to be corrected for differences in
elevation between the sampling site and the airport.
9.7 If the flow rate is outside the acceptable range specified by
the manufacturer, check for leaks, and if necessary, adjust the flow
rate to the specified setpoint. Stop the sampler.
9.8 Set the timer to start and stop the sampler at appropriate
times. Set the elapsed time meter to zero or record the initial meter
reading.
9.9 Record the sample information (site location or identification
number, sample date, filter identification number, and sampler model and
serial number).
9.10 Sample for 24 1 hours.
9.11 Determine and record the average flow rate (Qa) in
actual m\3\/min for the sampling period in accordance with the
instructions provided in the sampler manufacturer's instruction manual.
Record the elapsed time meter final reading and, if needed, the average
ambient temperature and barometric pressure for the sampling period (see
note following step 9.6).
9.12 Carefully remove the filter from the sampler, following the
sampler manufacturer's instruction manual. Touch only the outer edges of
the filter.
9.13 Place the filter in a protective holder or container (e.g.,
petri dish, glassine envelope, or manila folder).
9.14 Record any factors such as meteorological conditions,
construction activity, fires or dust storms, etc., that might be
pertinent to the measurement on the filter information record.
9.15 Transport the exposed sample filter to the filter conditioning
environment as soon as possible for equilibration and subsequent
weighing.
9.16 Equilibrate the exposed filter in the conditioning environment
for at least 24 hours under the same temperature and humidity conditions
used for presampling filter equilibration (see 9.3).
9.17 Immediately after equilibration, reweigh the filter and record
the postsampling weight with the filter identification number.
10.0 Sampler Maintenance.
[[Page 91]]
10.1 The PM10 sampler shall be maintained in strict
accordance with the maintenance procedures specified in the sampler
manufacturer's instruction manual.
11.0 Calculations.
11.1 Calculate the average flow rate over the sampling period
corrected to EPA reference conditions as Qstd. When the
sampler's flow indicator is calibrated in actual volumetric units
(Qa), Qstd is calculated as:
Qstd = Qa x (Pav/
Tav)(Tstd/Pstd)
where
Qstd = average flow rate at EPA reference conditions, std
m\3\/min;
Qa = average flow rate at ambient conditions, m\3\/min;
Pav = average barometric pressure during the sampling period
or average barometric pressure for the sampling site, kPa (or
mm Hg);
Tav = average ambient temperature during the sampling period
or seasonal average ambient temperature for the sampling site,
K;
Tstd = standard temperature, defined as 298 K;
Pstd = standard pressure, defined as 101.3 kPa (or 760 mm
Hg).
11.2 Calculate the total volume of air sampled as:
Vstd = Qstd x t
where
Vstd = total air sampled in standard volume units, std m\3\;
t = sampling time, min.
11.3 Calculate the PM10 concentration as:
PM10 = (Wf-Wi) x 10\6\/Vstd
where
PM10 = mass concentration of PM10, [micro]g/std
m\3\;
Wf, Wi = final and initial weights of filter
collecting PM1O particles, g;
10\6\ = conversion of g to [micro]g.
Note: If more than one size fraction in the PM10 size
range is collected by the sampler, the sum of the net weight gain by
each collection filter [[Sigma](Wf-Wi)] is used to
calculate the PM10 mass concentration.
12.0 References.
1. Quality Assurance Handbook for Air Pollution Measurement Systems,
Volume I, Principles. EPA-600/9-76-005, March 1976. Available from CERI,
ORD Publications, U.S. Environmental Protection Agency, 26 West St.
Clair Street, Cincinnati, OH 45268.
2. Quality Assurance Handbook for Air Pollution Measurement Systems,
Volume II, Ambient Air Specific Methods. EPA-600/4-77-027a, May 1977.
Available from CERI, ORD Publications, U.S. Environmental Protection
Agency, 26 West St. Clair Street, Cincinnati, OH 45268.
3. Clement, R.E., and F.W. Karasek. Sample Composition Changes in
Sampling and Analysis of Organic Compounds in Aerosols. Int. J. Environ.
Analyt. Chem., 7:109, 1979.
4. Lee, R.E., Jr., and J. Wagman. A Sampling Anomaly in the
Determination of Atmospheric Sulfate Concentration. Amer. Ind. Hyg.
Assoc. J., 27:266, 1966.
5. Appel, B.R., S.M. Wall, Y. Tokiwa, and M. Haik. Interference
Effects in Sampling Particulate Nitrate in Ambient Air. Atmos. Environ.,
13:319, 1979.
6. Coutant, R.W. Effect of Environmental Variables on Collection of
Atmospheric Sulfate. Environ. Sci. Technol., 11:873, 1977.
7. Spicer, C.W., and P. Schumacher. Interference in Sampling
Atmospheric Particulate Nitrate. Atmos. Environ., 11:873, 1977.
8. Appel, B.R., Y. Tokiwa, and M. Haik. Sampling of Nitrates in
Ambient Air. Atmos. Environ., 15:283, 1981.
9. Spicer, C.W., and P.M. Schumacher. Particulate Nitrate:
Laboratory and Field Studies of Major Sampling Interferences. Atmos.
Environ., 13:543, 1979.
10. Appel, B.R. Letter to Larry Purdue, U.S. EPA, Environmental
Monitoring and Support Laboratory. March 18, 1982, Docket No. A-82-37,
II-I-1.
11. Pierson, W.R., W.W. Brachaczek, T.J. Korniski, T.J. Truex, and
J.W. Butler. Artifact Formation of Sulfate, Nitrate, and Hydrogen Ion on
Backup Filters: Allegheny Mountain Experiment. J. Air Pollut. Control
Assoc., 30:30, 1980.
12. Dunwoody, C.L. Rapid Nitrate Loss From PM10 Filters.
J. Air Pollut. Control Assoc., 36:817, 1986.
13. Harrell, R.M. Measuring the Alkalinity of Hi-Vol Air Filters.
EMSL/RTP-SOP-QAD-534, October 1985. Available from the U.S.
Environmental Protection Agency, EMSL/QAD, Research Triangle Park, NC
27711.
14. Smith, F., P.S. Wohlschlegel, R.S.C. Rogers, and D.J. Mulligan.
Investigation of Flow Rate Calibration Procedures Associated With the
High Volume Method for Determination of Suspended Particulates. EPA-600/
4-78-047, U.S. Environmental Protection Agency, Research Triangle Park,
NC 27711, 1978.
[52 FR 24664, July 1, 1987; 52 FR 29467, Aug. 7, 1987]
Sec. Appendix K to Part 50--Interpretation of the National Ambient Air
Quality Standards for Particulate Matter
1.0 General
(a) This appendix explains the computations necessary for analyzing
particulate matter data to determine attainment of the 24-hour standards
specified in 40 CFR 50.6. For the primary and secondary standards,
particulate matter is measured in the ambient air as PM10
(particles with an aerodynamic diameter less than or equal to a
[[Page 92]]
nominal 10 micrometers) by a reference method based on appendix J of
this part and designated in accordance with part 53 of this chapter, or
by an equivalent method designated in accordance with part 53 of this
chapter. The required frequency of measurements is specified in part 58
of this chapter.
(b) The terms used in this appendix are defined as follows:
Average refers to the arithmetic mean of the estimated number of
exceedances per year, as per Section 3.1.
Daily value for PM10 refers to the 24-hour average
concentration of PM10 calculated or measured from midnight to
midnight (local time).
Exceedance means a daily value that is above the level of the 24-
hour standard after rounding to the nearest 10 [micro]g/m\3\ (i.e.,
values ending in 5 or greater are to be rounded up).
Expected annual value is the number approached when the annual
values from an increasing number of years are averaged, in the absence
of long-term trends in emissions or meteorological conditions.
Year refers to a calendar year.
(c) Although the discussion in this appendix focuses on monitored
data, the same principles apply to modeling data, subject to EPA
modeling guidelines.
2.0 Attainment Determinations
2.1 24-Hour Primary and Secondary Standards
(a) Under 40 CFR 50.6(a) the 24-hour primary and secondary standards
are attained when the expected number of exceedances per year at each
monitoring site is less than or equal to one. In the simplest case, the
number of expected exceedances at a site is determined by recording the
number of exceedances in each calendar year and then averaging them over
the past 3 calendar years. Situations in which 3 years of data are not
available and possible adjustments for unusual events or trends are
discussed in sections 2.3 and 2.4 of this appendix. Further, when data
for a year are incomplete, it is necessary to compute an estimated
number of exceedances for that year by adjusting the observed number of
exceedances. This procedure, performed by calendar quarter, is described
in section 3.0 of this appendix. The expected number of exceedances is
then estimated by averaging the individual annual estimates for the past
3 years.
(b) The comparison with the allowable expected exceedance rate of
one per year is made in terms of a number rounded to the nearest tenth
(fractional values equal to or greater than 0.05 are to be rounded up;
e.g., an exceedance rate of 1.05 would be rounded to 1.1, which is the
lowest rate for nonattainment).
2.2 Reserved
2.3 Data Requirements
(a) 40 CFR 58.12 specifies the required minimum frequency of
sampling for PM10. For the purposes of making comparisons
with the particulate matter standards, all data produced by State and
Local Air Monitoring Stations (SLAMS) and other sites submitted to EPA
in accordance with the part 58 requirements must be used, and a minimum
of 75 percent of the scheduled PM10 samples per quarter are
required.
(b) To demonstrate attainment of the 24-hour standards at a
monitoring site, the monitor must provide sufficient data to perform the
required calculations of sections 3.0 and 4.0 of this appendix. The
amount of data required varies with the sampling frequency, data capture
rate and the number of years of record. In all cases, 3 years of
representative monitoring data that meet the 75 percent criterion of the
previous paragraph should be utilized, if available, and would suffice.
More than 3 years may be considered, if all additional representative
years of data meeting the 75 percent criterion are utilized. Data not
meeting these criteria may also suffice to show attainment; however,
such exceptions will have to be approved by the appropriate Regional
Administrator in accordance with EPA guidance.
(c) There are less stringent data requirements for showing that a
monitor has failed an attainment test and thus has recorded a violation
of the particulate matter standards. Although it is generally necessary
to meet the minimum 75 percent data capture requirement per quarter to
use the computational equations described in section 3.0 of this
appendix, this criterion does not apply when less data is sufficient to
unambiguously establish nonattainment. The following examples illustrate
how nonattainment can be demonstrated when a site fails to meet the
completeness criteria. Nonattainment of the 24-hour primary standards
can be established by the observed annual number of exceedances (e.g.,
four observed exceedances in a single year), or by the estimated number
of exceedances derived from the observed number of exceedances and the
required number of scheduled samples (e.g., two observed exceedances
with every other day sampling). In both cases, expected annual values
must exceed the levels allowed by the standards.
2.4 Adjustment for Exceptional Events and Trends
(a) An exceptional event is an uncontrollable event caused by
natural sources of particulate matter or an event that is not expected
to recur at a given location. Inclusion of such a value in the
computation of
[[Page 93]]
exceedances or averages could result in inappropriate estimates of their
respective expected annual values. To reduce the effect of unusual
events, more than 3 years of representative data may be used.
Alternatively, other techniques, such as the use of statistical models
or the use of historical data could be considered so that the event may
be discounted or weighted according to the likelihood that it will
recur. The use of such techniques is subject to the approval of the
appropriate Regional Administrator in accordance with EPA guidance.
(b) In cases where long-term trends in emissions and air quality are
evident, mathematical techniques should be applied to account for the
trends to ensure that the expected annual values are not inappropriately
biased by unrepresentative data. In the simplest case, if 3 years of
data are available under stable emission conditions, this data should be
used. In the event of a trend or shift in emission patterns, either the
most recent representative year(s) could be used or statistical
techniques or models could be used in conjunction with previous years of
data to adjust for trends. The use of less than 3 years of data, and any
adjustments are subject to the approval of the appropriate Regional
Administrator in accordance with EPA guidance.
3.0 Computational Equations for the 24-Hour Standards
3.1 Estimating Exceedances for a Year
(a) If PM10 sampling is scheduled less frequently than
every day, or if some scheduled samples are missed, a PM10
value will not be available for each day of the year. To account for the
possible effect of incomplete data, an adjustment must be made to the
data collected at each monitoring location to estimate the number of
exceedances in a calendar year. In this adjustment, the assumption is
made that the fraction of missing values that would have exceeded the
standard level is identical to the fraction of measured values above
this level. This computation is to be made for all sites that are
scheduled to monitor throughout the entire year and meet the minimum
data requirements of section 2.3 of this appendix. Because of possible
seasonal imbalance, this adjustment shall be applied on a quarterly
basis. The estimate of the expected number of exceedances for the
quarter is equal to the observed number of exceedances plus an increment
associated with the missing data. The following equation must be used
for these computations:
[GRAPHIC] [TIFF OMITTED] TR17OC06.000
Where:
eq = the estimated number of exceedances for calendar quarter
q;
vq = the observed number of exceedances for calendar quarter
q;
Nq = the number of days in calendar quarter q;
nq = the number of days in calendar quarter q with
PM10 data; and
q = the index for calendar quarter, q = 1, 2, 3 or 4.
(b) The estimated number of exceedances for a calendar quarter must
be rounded to the nearest hundredth (fractional values equal to or
greater than 0.005 must be rounded up).
(c) The estimated number of exceedances for the year, e, is the sum
of the estimates for each calendar quarter.
[GRAPHIC] [TIFF OMITTED] TR17OC06.001
(d) The estimated number of exceedances for a single year must be
rounded to one decimal place (fractional values equal to or greater than
0.05 are to be rounded up). The expected number of exceedances is then
estimated by averaging the individual annual estimates for the most
recent 3 or more representative years of data. The expected number of
exceedances must be rounded to one decimal place (fractional values
equal to or greater than 0.05 are to be rounded up).
(e) The adjustment for incomplete data will not be necessary for
monitoring or modeling data which constitutes a complete record, i.e.,
365 days per year.
(f) To reduce the potential for overestimating the number of
expected exceedances, the correction for missing data will not be
required for a calendar quarter in which the first observed exceedance
has occurred if:
(1) There was only one exceedance in the calendar quarter;
(2) Everyday sampling is subsequently initiated and maintained for 4
calendar quarters in accordance with 40 CFR 58.12; and
(3) Data capture of 75 percent is achieved during the required
period of everyday sampling. In addition, if the first exceedance is
observed in a calendar quarter in which the monitor is already sampling
every day, no adjustment for missing data will be made to the first
exceedance if a 75 percent data capture rate was achieved in the quarter
in which it was observed.
[[Page 94]]
Example 1
a. During a particular calendar quarter, 39 out of a possible 92
samples were recorded, with one observed exceedance of the 24-hour
standard. Using Equation 1, the estimated number of exceedances for the
quarter is:
eq = 1 x 92/39 = 2.359 or 2.36.
b. If the estimated exceedances for the other 3 calendar quarters in
the year were 2.30, 0.0 and 0.0, then, using Equation 2, the estimated
number of exceedances for the year is 2.36 + 2.30 + 0.0 + 0.0 which
equals 4.66 or 4.7. If no exceedances were observed for the 2 previous
years, then the expected number of exceedances is estimated by: (\1/3\)
x (4.7 + 0 + 0) = 1.57 or 1.6. Since 1.6 exceeds the allowable number of
expected exceedances, this monitoring site would fail the attainment
test.
Example 2
In this example, everyday sampling was initiated following the first
observed exceedance as required by 40 CFR 58.12. Accordingly, the first
observed exceedance would not be adjusted for incomplete sampling.
During the next three quarters, 1.2 exceedances were estimated. In this
case, the estimated exceedances for the year would be 1.0 + 1.2 + 0.0 +
0.0 which equals 2.2. If, as before, no exceedances were observed for
the two previous years, then the estimated exceedances for the 3-year
period would then be (\1/3\) x (2.2 + 0.0 + 0.0) = 0.7, and the
monitoring site would not fail the attainment test.
3.2 Adjustments for Non-Scheduled Sampling Days
(a) If a systematic sampling schedule is used and sampling is
performed on days in addition to the days specified by the systematic
sampling schedule, e.g., during episodes of high pollution, then an
adjustment must be made in the equation for the estimation of
exceedances. Such an adjustment is needed to eliminate the bias in the
estimate of the quarterly and annual number of exceedances that would
occur if the chance of an exceedance is different for scheduled than for
non-scheduled days, as would be the case with episode sampling.
(b) The required adjustment treats the systematic sampling schedule
as a stratified sampling plan. If the period from one scheduled sample
until the day preceding the next scheduled sample is defined as a
sampling stratum, then there is one stratum for each scheduled sampling
day. An average number of observed exceedances is computed for each of
these sampling strata. With nonscheduled sampling days, the estimated
number of exceedances is defined as:
[GRAPHIC] [TIFF OMITTED] TR17OC06.002
Where:
eq = the estimated number of exceedances for the quarter;
Nq = the number of days in the quarter;
mq = the number of strata with samples during the quarter;
vj = the number of observed exceedances in stratum j; and
kj = the number of actual samples in stratum j.
(c) Note that if only one sample value is recorded in each stratum,
then Equation 3 reduces to Equation 1.
Example 3
A monitoring site samples according to a systematic sampling
schedule of one sample every 6 days, for a total of 15 scheduled samples
in a quarter out of a total of 92 possible samples. During one 6-day
period, potential episode levels of PM10 were suspected, so 5
additional samples were taken. One of the regular scheduled samples was
missed, so a total of 19 samples in 14 sampling strata were measured.
The one 6-day sampling stratum with 6 samples recorded 2 exceedances.
The remainder of the quarter with one sample per stratum recorded zero
exceedances. Using Equation 3, the estimated number of exceedances for
the quarter is:
Eq = (92/14) x (2/6 + 0 + . . . + 0) = 2.19.
[71 FR 61224, Oct. 17, 2006]
Sec. Appendix L to Part 50--Reference Method for the Determination of
Fine Particulate Matter as PM2.5 in the Atmosphere
1.0 Applicability.
1.1 This method provides for the measurement of the mass
concentration of fine particulate matter having an aerodynamic diameter
less than or equal to a nominal 2.5 micrometers (PM2.5) in
ambient air over a 24-hour period for purposes of determining whether
the primary and secondary national ambient air quality standards for
fine particulate matter specified in Sec. 50.7 and Sec. 50.13 of this
part are met. The measurement process is considered to be
nondestructive, and the PM2.5 sample obtained can be
subjected to subsequent physical or chemical analyses. Quality
assessment procedures are provided in part 58, appendix A of this
chapter, and quality assurance guidance are provided in references 1, 2,
and 3 in section 13.0 of this appendix.
[[Page 95]]
1.2 This method will be considered a reference method for purposes
of part 58 of this chapter only if:
(a) The associated sampler meets the requirements specified in this
appendix and the applicable requirements in part 53 of this chapter, and
(b) The method and associated sampler have been designated as a
reference method in accordance with part 53 of this chapter.
1.3 PM2.5 samplers that meet nearly all specifications
set forth in this method but have minor deviations and/or modifications
of the reference method sampler will be designated as ``Class I''
equivalent methods for PM2.5 in accordance with part 53 of
this chapter.
2.0 Principle.
2.1 An electrically powered air sampler draws ambient air at a
constant volumetric flow rate into a specially shaped inlet and through
an inertial particle size separator (impactor) where the suspended
particulate matter in the PM2.5 size range is separated for
collection on a polytetrafluoroethylene (PTFE) filter over the specified
sampling period. The air sampler and other aspects of this reference
method are specified either explicitly in this appendix or generally
with reference to other applicable regulations or quality assurance
guidance.
2.2 Each filter is weighed (after moisture and temperature
conditioning) before and after sample collection to determine the net
gain due to collected PM2.5. The total volume of air sampled
is determined by the sampler from the measured flow rate at actual
ambient temperature and pressure and the sampling time. The mass
concentration of PM2.5 in the ambient air is computed as the
total mass of collected particles in the PM2.5 size range
divided by the actual volume of air sampled, and is expressed in
micrograms per cubic meter of air ([micro]g/m\3\).
3.0 PM2.5 Measurement Range.
3.1 Lower concentration limit. The lower detection limit of the mass
concentration measurement range is estimated to be approximately 2
[micro]g/m\3\, based on noted mass changes in field blanks in
conjunction with the 24 m\3\ nominal total air sample volume specified
for the 24-hour sample.
3.2 Upper concentration limit. The upper limit of the mass
concentration range is determined by the filter mass loading beyond
which the sampler can no longer maintain the operating flow rate within
specified limits due to increased pressure drop across the loaded
filter. This upper limit cannot be specified precisely because it is a
complex function of the ambient particle size distribution and type,
humidity, the individual filter used, the capacity of the sampler flow
rate control system, and perhaps other factors. Nevertheless, all
samplers are estimated to be capable of measuring 24-hour
PM2.5 mass concentrations of at least 200 [micro]g/m\3\ while
maintaining the operating flow rate within the specified limits.
3.3 Sample period. The required sample period for PM2.5
concentration measurements by this method shall be 1,380 to 1500 minutes
(23 to 25 hours). However, when a sample period is less than 1,380
minutes, the measured concentration (as determined by the collected
PM2.5 mass divided by the actual sampled air volume),
multiplied by the actual number of minutes in the sample period and
divided by 1,440, may be used as if it were a valid concentration
measurement for the specific purpose of determining a violation of the
NAAQS. This value assumes that the PM2.5 concentration is
zero for the remaining portion of the sample period and therefore
represents the minimum concentration that could have been measured for
the full 24-hour sample period. Accordingly, if the value thus
calculated is high enough to be an exceedance, such an exceedance would
be a valid exceedance for the sample period. When reported to AIRS, this
data value should receive a special code to identify it as not to be
commingled with normal concentration measurements or used for other
purposes.
4.0 Accuracy.
4.1 Because the size and volatility of the particles making up
ambient particulate matter vary over a wide range and the mass
concentration of particles varies with particle size, it is difficult to
define the accuracy of PM2.5 measurements in an absolute
sense. The accuracy of PM2.5 measurements is therefore
defined in a relative sense, referenced to measurements provided by this
reference method. Accordingly, accuracy shall be defined as the degree
of agreement between a subject field PM2.5 sampler and a
collocated PM2.5 reference method audit sampler operating
simultaneously at the monitoring site location of the subject sampler
and includes both random (precision) and systematic (bias) errors. The
requirements for this field sampler audit procedure are set forth in
part 58, appendix A of this chapter.
4.2 Measurement system bias. Results of collocated measurements
where the duplicate sampler is a reference method sampler are used to
assess a portion of the measurement system bias according to the
schedule and procedure specified in part 58, appendix A of this chapter.
4.3 Audits with reference method samplers to determine system
accuracy and bias. According to the schedule and procedure specified in
part 58, appendix A of this chapter, a reference method sampler is
required to be located at each of selected PM2.5 SLAMS sites
as a duplicate sampler. The results from the primary sampler and the
duplicate reference method sampler are used to calculate accuracy of the
primary sampler on a quarterly
[[Page 96]]
basis, bias of the primary sampler on an annual basis, and bias of a
single reporting organization on an annual basis. Reference 2 in section
13.0 of this appendix provides additional information and guidance on
these reference method audits.
4.4 Flow rate accuracy and bias. Part 58, appendix A of this chapter
requires that the flow rate accuracy and bias of individual
PM2.5 samplers used in SLAMS monitoring networks be assessed
periodically via audits of each sampler's operational flow rate. In
addition, part 58, appendix A of this chapter requires that flow rate
bias for each reference and equivalent method operated by each reporting
organization be assessed quarterly and annually. Reference 2 in section
13.0 of this appendix provides additional information and guidance on
flow rate accuracy audits and calculations for accuracy and bias.
5.0 Precision. A data quality objective of 10 percent coefficient of
variation or better has been established for the operational precision
of PM2.5 monitoring data.
5.1 Tests to establish initial operational precision for each
reference method sampler are specified as a part of the requirements for
designation as a reference method under Sec. 53.58 of this chapter.
5.2 Measurement System Precision. Collocated sampler results, where
the duplicate sampler is not a reference method sampler but is a sampler
of the same designated method as the primary sampler, are used to assess
measurement system precision according to the schedule and procedure
specified in part 58, appendix A of this chapter. Part 58, appendix A of
this chapter requires that these collocated sampler measurements be used
to calculate quarterly and annual precision estimates for each primary
sampler and for each designated method employed by each reporting
organization. Reference 2 in section 13.0 of this appendix provides
additional information and guidance on this requirement.
6.0 Filter for PM2.5 Sample Collection. Any filter
manufacturer or vendor who sells or offers to sell filters specifically
identified for use with this PM2.5 reference method shall
certify that the required number of filters from each lot of filters
offered for sale as such have been tested as specified in this section
6.0 and meet all of the following design and performance specifications.
6.1 Size. Circular, 46.2 mm diameter 0.25 mm.
6.2 Medium. Polytetrafluoroethylene (PTFE Teflon), with integral
support ring.
6.3 Support ring. Polymethylpentene (PMP) or equivalent inert
material, 0.38 0.04 mm thick, outer diameter 46.2
mm 0.25 mm, and width of 3.68 mm (0.00, -0.51 mm).
6.4 Pore size. 2 [micro]m as measured by ASTM F 316-94.
6.5 Filter thickness. 30 to 50 [micro]m.
6.6 Maximum pressure drop (clean filter). 30 cm H2O
column @ 16.67 L/min clean air flow.
6.7 Maximum moisture pickup. Not more than 10 [micro]g weight
increase after 24-hour exposure to air of 40 percent relative humidity,
relative to weight after 24-hour exposure to air of 35 percent relative
humidity.
6.8 Collection efficiency. Greater than 99.7 percent, as measured by
the DOP test (ASTM D 2986-91) with 0.3 [micro]m particles at the
sampler's operating face velocity.
6.9 Filter weight stability. Filter weight loss shall be less than
20 [micro]g, as measured in each of the following two tests specified in
sections 6.9.1 and 6.9.2 of this appendix. The following conditions
apply to both of these tests: Filter weight loss shall be the average
difference between the initial and the final filter weights of a random
sample of test filters selected from each lot prior to sale. The number
of filters tested shall be not less than 0.1 percent of the filters of
each manufacturing lot, or 10 filters, whichever is greater. The filters
shall be weighed under laboratory conditions and shall have had no air
sample passed through them, i.e., filter blanks. Each test procedure
must include initial conditioning and weighing, the test, and final
conditioning and weighing. Conditioning and weighing shall be in
accordance with sections 8.0 through 8.2 of this appendix and general
guidance provided in reference 2 of section 13.0 of this appendix.
6.9.1 Test for loose, surface particle contamination. After the
initial weighing, install each test filter, in turn, in a filter
cassette (Figures L-27, L-28, and L-29 of this appendix) and drop the
cassette from a height of 25 cm to a flat hard surface, such as a
particle-free wood bench. Repeat two times, for a total of three drop
tests for each test filter. Remove the test filter from the cassette and
weigh the filter. The average change in weight must be less than 20
[micro]g.
6.9.2 Test for temperature stability. After weighing each filter,
place the test filters in a drying oven set at 40 [deg]C 2 [deg]C for not less than 48 hours. Remove, condition,
and reweigh each test filter. The average change in weight must be less
than 20 [micro]g.
6.10 Alkalinity. Less than 25 microequivalents/gram of filter, as
measured by the guidance given in reference 2 in section 13.0 of this
appendix.
6.11 Supplemental requirements. Although not required for
determination of PM2.5 mass concentration under this
reference method, additional specifications for the filter must be
developed by users who intend to subject PM2.5 filter samples
to subsequent chemical analysis. These supplemental specifications
include background chemical contamination of the filter and any other
filter parameters that may be required by the method of chemical
analysis. All such supplemental filter specifications must be compatible
with and
[[Page 97]]
secondary to the primary filter specifications given in this section 6.0
of this appendix.
7.0 PM2.5 Sampler.
7.1 Configuration. The sampler shall consist of a sample air inlet,
downtube, particle size separator (impactor), filter holder assembly,
air pump and flow rate control system, flow rate measurement device,
ambient and filter temperature monitoring system, barometric pressure
measurement system, timer, outdoor environmental enclosure, and suitable
mechanical, electrical, or electronic control capability to meet or
exceed the design and functional performance as specified in this
section 7.0 of this appendix. The performance specifications require
that the sampler:
(a) Provide automatic control of sample volumetric flow rate and
other operational parameters.
(b) Monitor these operational parameters as well as ambient
temperature and pressure.
(c) Provide this information to the sampler operator at the end of
each sample period in digital form, as specified in table L-1 of section
7.4.19 of this appendix.
7.2 Nature of specifications. The PM2.5 sampler is
specified by a combination of design and performance requirements. The
sample inlet, downtube, particle size discriminator, filter cassette,
and the internal configuration of the filter holder assembly are
specified explicitly by design figures and associated mechanical
dimensions, tolerances, materials, surface finishes, assembly
instructions, and other necessary specifications. All other aspects of
the sampler are specified by required operational function and
performance, and the design of these other aspects (including the design
of the lower portion of the filter holder assembly) is optional, subject
to acceptable operational performance. Test procedures to demonstrate
compliance with both the design and performance requirements are set
forth in subpart E of part 53 of this chapter.
7.3 Design specifications. Except as indicated in this section 7.3
of this appendix, these components must be manufactured or reproduced
exactly as specified, in an ISO 9001-registered facility, with
registration initially approved and subsequently maintained during the
period of manufacture. See Sec. 53.1(t) of this chapter for the
definition of an ISO-registered facility. Minor modifications or
variances to one or more components that clearly would not affect the
aerodynamic performance of the inlet, downtube, impactor, or filter
cassette will be considered for specific approval. Any such proposed
modifications shall be described and submitted to the EPA for specific
individual acceptability either as part of a reference or equivalent
method application under part 53 of this chapter or in writing in
advance of such an intended application under part 53 of this chapter.
7.3.1 Sample inlet assembly. The sample inlet assembly, consisting
of the inlet, downtube, and impactor shall be configured and assembled
as indicated in Figure L-1 of this appendix and shall meet all
associated requirements. A portion of this assembly shall also be
subject to the maximum overall sampler leak rate specification under
section 7.4.6 of this appendix.
7.3.2 Inlet. The sample inlet shall be fabricated as indicated in
Figures L-2 through L-18 of this appendix and shall meet all associated
requirements.
7.3.3 Downtube. The downtube shall be fabricated as indicated in
Figure L-19 of this appendix and shall meet all associated requirements.
7.3.4 Particle size separator. The sampler shall be configured with
either one of the two alternative particle size separators described in
this section 7.3.4. One separator is an impactor-type separator (WINS
impactor) described in sections 7.3.4.1, 7.3.4.2, and 7.3.4.3 of this
appendix. The alternative separator is a cyclone-type separator (VSCC
\TM\) described in section 7.3.4.4 of this appendix.
7.3.4.1 The impactor (particle size separator) shall be fabricated
as indicated in Figures L-20 through L-24 of this appendix and shall
meet all associated requirements. Following the manufacture and
finishing of each upper impactor housing (Figure L-21 of this appendix),
the dimension of the impaction jet must be verified by the manufacturer
using Class ZZ go/no-go plug gauges that are traceable to NIST.
7.3.4.2 Impactor filter specifications:
(a) Size. Circular, 35 to 37 mm diameter.
(b) Medium. Borosilicate glass fiber, without binder.
(c) Pore size. 1 to 1.5 micrometer, as measured by ASTM F 316-80.
(d) Thickness. 300 to 500 micrometers.
7.3.4.3 Impactor oil specifications:
(a) Composition. Dioctyl sebacate (DOS), single-compound diffusion
oil.
(b) Vapor pressure. Maximum 2 x 10-8 mm Hg at 25 [deg]C.
(c) Viscosity. 36 to 40 centistokes at 25 [deg]C.
(d) Density. 1.06 to 1.07 g/cm\3\ at 25 [deg]C.
(e) Quantity. 1 mL 0.1 mL.
7.3.4.4 The cyclone-type separator is identified as a BGI VSCC \TM\
Very Sharp Cut Cyclone particle size separator specified as part of EPA-
designated equivalent method EQPM-0202-142 (67 FR 15567, April 2, 2002)
and as manufactured by BGI Incorporated, 58 Guinan Street, Waltham,
Massachusetts 20451.
7.3.5 Filter holder assembly. The sampler shall have a sample filter
holder assembly to adapt and seal to the down tube and to hold and seal
the specified filter, under section 6.0 of this appendix, in the sample
air stream in a horizontal position below the downtube such that the
sample air passes downward through the filter at a uniform face
velocity.
[[Page 98]]
The upper portion of this assembly shall be fabricated as indicated in
Figures L-25 and L-26 of this appendix and shall accept and seal with
the filter cassette, which shall be fabricated as indicated in Figures
L-27 through L-29 of this appendix.
(a) The lower portion of the filter holder assembly shall be of a
design and construction that:
(1) Mates with the upper portion of the assembly to complete the
filter holder assembly,
(2) Completes both the external air seal and the internal filter
cassette seal such that all seals are reliable over repeated filter
changings, and
(3) Facilitates repeated changing of the filter cassette by the
sampler operator.
(b) Leak-test performance requirements for the filter holder
assembly are included in section 7.4.6 of this appendix.
(c) If additional or multiple filters are stored in the sampler as
part of an automatic sequential sample capability, all such filters,
unless they are currently and directly installed in a sampling channel
or sampling configuration (either active or inactive), shall be covered
or (preferably) sealed in such a way as to:
(1) Preclude significant exposure of the filter to possible
contamination or accumulation of dust, insects, or other material that
may be present in the ambient air, sampler, or sampler ventilation air
during storage periods either before or after sampling; and
(2) To minimize loss of volatile or semi-volatile PM sample
components during storage of the filter following the sample period.
7.3.6 Flow rate measurement adapter. A flow rate measurement adapter
as specified in Figure L-30 of this appendix shall be furnished with
each sampler.
7.3.7 Surface finish. All internal surfaces exposed to sample air
prior to the filter shall be treated electrolytically in a sulfuric acid
bath to produce a clear, uniform anodized surface finish of not less
than 1000 mg/ft\2\ (1.08 mg/cm\2\) in accordance with military standard
specification (mil. spec.) 8625F, Type II, Class 1 in reference 4 of
section 13.0 of this appendix. This anodic surface coating shall not be
dyed or pigmented. Following anodization, the surfaces shall be sealed
by immersion in boiling deionized water for not less than 15 minutes.
Section 53.51(d)(2) of this chapter should also be consulted.
7.3.8 Sampling height. The sampler shall be equipped with legs, a
stand, or other means to maintain the sampler in a stable, upright
position and such that the center of the sample air entrance to the
inlet, during sample collection, is maintained in a horizontal plane and
is 2.0 0.2 meters above the floor or other
horizontal supporting surface. Suitable bolt holes, brackets, tie-downs,
or other means should be provided to facilitate mechanically securing
the sample to the supporting surface to prevent toppling of the sampler
due to wind.
7.4 Performance specifications.
7.4.1 Sample flow rate. Proper operation of the impactor requires
that specific air velocities be maintained through the device.
Therefore, the design sample air flow rate through the inlet shall be
16.67 L/min (1.000 m\3\/hour) measured as actual volumetric flow rate at
the temperature and pressure of the sample air entering the inlet.
7.4.2 Sample air flow rate control system. The sampler shall have a
sample air flow rate control system which shall be capable of providing
a sample air volumetric flow rate within the specified range, under
section 7.4.1 of this appendix, for the specified filter, under section
6.0 of this appendix, at any atmospheric conditions specified, under
section 7.4.7 of this appendix, at a filter pressure drop equal to that
of a clean filter plus up to 75 cm water column (55 mm Hg), and over the
specified range of supply line voltage, under section 7.4.15.1 of this
appendix. This flow control system shall allow for operator adjustment
of the operational flow rate of the sampler over a range of at least
15 percent of the flow rate specified in section
7.4.1 of this appendix.
7.4.3 Sample flow rate regulation. The sample flow rate shall be
regulated such that for the specified filter, under section 6.0 of this
appendix, at any atmospheric conditions specified, under section 7.4.7
of this appendix, at a filter pressure drop equal to that of a clean
filter plus up to 75 cm water column (55 mm Hg), and over the specified
range of supply line voltage, under section 7.4.15.1 of this appendix,
the flow rate is regulated as follows:
7.4.3.1 The volumetric flow rate, measured or averaged over
intervals of not more than 5 minutes over a 24-hour period, shall not
vary more than 5 percent from the specified 16.67
L/min flow rate over the entire sample period.
7.4.3.2 The coefficient of variation (sample standard deviation
divided by the mean) of the flow rate, measured over a 24-hour period,
shall not be greater than 2 percent.
7.4.3.3 The amplitude of short-term flow rate pulsations, such as
may originate from some types of vacuum pumps, shall be attenuated such
that they do not cause significant flow measurement error or affect the
collection of particles on the particle collection filter.
7.4.4 Flow rate cut off. The sampler's sample air flow rate control
system shall terminate sample collection and stop all sample flow for
the remainder of the sample period in the event that the sample flow
rate deviates by more than 10 percent from the sampler design flow rate
specified in section 7.4.1 of this appendix for more than 60 seconds.
However, this sampler cut-off provision shall not apply during periods
when the sampler is inoperative due to a temporary power interruption,
[[Page 99]]
and the elapsed time of the inoperative period shall not be included in
the total sample time measured and reported by the sampler, under
section 7.4.13 of this appendix.
7.4.5 Flow rate measurement.
7.4.5.1 The sampler shall provide a means to measure and indicate
the instantaneous sample air flow rate, which shall be measured as
volumetric flow rate at the temperature and pressure of the sample air
entering the inlet, with an accuracy of 2 percent.
The measured flow rate shall be available for display to the sampler
operator at any time in either sampling or standby modes, and the
measurement shall be updated at least every 30 seconds. The sampler
shall also provide a simple means by which the sampler operator can
manually start the sample flow temporarily during non-sampling modes of
operation, for the purpose of checking the sample flow rate or the flow
rate measurement system.
7.4.5.2 During each sample period, the sampler's flow rate
measurement system shall automatically monitor the sample volumetric
flow rate, obtaining flow rate measurements at intervals of not greater
than 30 seconds.
(a) Using these interval flow rate measurements, the sampler shall
determine or calculate the following flow-related parameters, scaled in
the specified engineering units:
(1) The instantaneous or interval-average flow rate, in L/min.
(2) The value of the average sample flow rate for the sample period,
in L/min.
(3) The value of the coefficient of variation (sample standard
deviation divided by the average) of the sample flow rate for the sample
period, in percent.
(4) The occurrence of any time interval during the sample period in
which the measured sample flow rate exceeds a range of 5 percent of the average flow rate for the sample period
for more than 5 minutes, in which case a warning flag indicator shall be
set.
(5) The value of the integrated total sample volume for the sample
period, in m\3\.
(b) Determination or calculation of these values shall properly
exclude periods when the sampler is inoperative due to temporary
interruption of electrical power, under section 7.4.13 of this appendix,
or flow rate cut off, under section 7.4.4 of this appendix.
(c) These parameters shall be accessible to the sampler operator as
specified in table L-1 of section 7.4.19 of this appendix. In addition,
it is strongly encouraged that the flow rate for each 5-minute interval
during the sample period be available to the operator following the end
of the sample period.
7.4.6 Leak test capability.
7.4.6.1 External leakage. The sampler shall include an external air
leak-test capability consisting of components, accessory hardware,
operator interface controls, a written procedure in the associated
Operation/Instruction Manual, under section 7.4.18 of this appendix, and
all other necessary functional capability to permit and facilitate the
sampler operator to conveniently carry out a leak test of the sampler at
a field monitoring site without additional equipment. The sampler
components to be subjected to this leak test include all components and
their interconnections in which external air leakage would or could
cause an error in the sampler's measurement of the total volume of
sample air that passes through the sample filter.
(a) The suggested technique for the operator to use for this leak
test is as follows:
(1) Remove the sampler inlet and installs the flow rate measurement
adapter supplied with the sampler, under section 7.3.6 of this appendix.
(2) Close the valve on the flow rate measurement adapter and use the
sampler air pump to draw a partial vacuum in the sampler, including (at
least) the impactor, filter holder assembly (filter in place), flow
measurement device, and interconnections between these devices, of at
least 55 mm Hg (75 cm water column), measured at a location downstream
of the filter holder assembly.
(3) Plug the flow system downstream of these components to isolate
the components under vacuum from the pump, such as with a built-in
valve.
(4) Stop the pump.
(5) Measure the trapped vacuum in the sampler with a built-in
pressure measuring device.
(6) (i) Measure the vacuum in the sampler with the built-in pressure
measuring device again at a later time at least 10 minutes after the
first pressure measurement.
(ii) Caution: Following completion of the test, the adaptor valve
should be opened slowly to limit the flow rate of air into the sampler.
Excessive air flow rate may blow oil out of the impactor.
(7) Upon completion of the test, open the adaptor valve, remove the
adaptor and plugs, and restore the sampler to the normal operating
configuration.
(b) The associated leak test procedure shall require that for
successful passage of this test, the difference between the two pressure
measurements shall not be greater than the number of mm of Hg specified
for the sampler by the manufacturer, based on the actual internal volume
of the sampler, that indicates a leak of less than 80 mL/min.
(c) Variations of the suggested technique or an alternative external
leak test technique may be required for samplers whose design or
configuration would make the suggested technique impossible or
impractical. The specific proposed external leak test procedure, or
particularly an alternative leak
[[Page 100]]
test technique, proposed for a particular candidate sampler may be
described and submitted to the EPA for specific individual acceptability
either as part of a reference or equivalent method application under
part 53 of this chapter or in writing in advance of such an intended
application under part 53 of this chapter.
7.4.6.2 Internal, filter bypass leakage. The sampler shall include
an internal, filter bypass leak-check capability consisting of
components, accessory hardware, operator interface controls, a written
procedure in the Operation/Instruction Manual, and all other necessary
functional capability to permit and facilitate the sampler operator to
conveniently carry out a test for internal filter bypass leakage in the
sampler at a field monitoring site without additional equipment. The
purpose of the test is to determine that any portion of the sample flow
rate that leaks past the sample filter without passing through the
filter is insignificant relative to the design flow rate for the
sampler.
(a) The suggested technique for the operator to use for this leak
test is as follows:
(1) Carry out an external leak test as provided under section
7.4.6.1 of this appendix which indicates successful passage of the
prescribed external leak test.
(2) Install a flow-impervious membrane material in the filter
cassette, either with or without a filter, as appropriate, which
effectively prevents air flow through the filter.
(3) Use the sampler air pump to draw a partial vacuum in the
sampler, downstream of the filter holder assembly, of at least 55 mm Hg
(75 cm water column).
(4) Plug the flow system downstream of the filter holder to isolate
the components under vacuum from the pump, such as with a built-in
valve.
(5) Stop the pump.
(6) Measure the trapped vacuum in the sampler with a built-in
pressure measuring device.
(7) Measure the vacuum in the sampler with the built-in pressure
measuring device again at a later time at least 10 minutes after the
first pressure measurement.
(8) Remove the flow plug and membrane and restore the sampler to the
normal operating configuration.
(b) The associated leak test procedure shall require that for
successful passage of this test, the difference between the two pressure
measurements shall not be greater than the number of mm of Hg specified
for the sampler by the manufacturer, based on the actual internal volume
of the portion of the sampler under vacuum, that indicates a leak of
less than 80 mL/min.
(c) Variations of the suggested technique or an alternative
internal, filter bypass leak test technique may be required for samplers
whose design or configuration would make the suggested technique
impossible or impractical. The specific proposed internal leak test
procedure, or particularly an alternative internal leak test technique
proposed for a particular candidate sampler may be described and
submitted to the EPA for specific individual acceptability either as
part of a reference or equivalent method application under part 53 of
this chapter or in writing in advance of such intended application under
part 53 of this chapter.
7.4.7 Range of operational conditions. The sampler is required to
operate properly and meet all requirements specified in this appendix
over the following operational ranges.
7.4.7.1 Ambient temperature. -30 to = 45 [deg]C (Note: Although for
practical reasons, the temperature range over which samplers are
required to be tested under part 53 of this chapter is -20 to = 40
[deg]C, the sampler shall be designed to operate properly over this
wider temperature range.).
7.4.7.2 Ambient relative humidity. 0 to 100 percent.
7.4.7.3 Barometric pressure range. 600 to 800 mm Hg.
7.4.8 Ambient temperature sensor. The sampler shall have capability
to measure the temperature of the ambient air surrounding the sampler
over the range of -30 to = 45 [deg]C, with a resolution of 0.1 [deg]C
and accuracy of 2.0 [deg]C, referenced as
described in reference 3 in section 13.0 of this appendix, with and
without maximum solar insolation.
7.4.8.1 The ambient temperature sensor shall be mounted external to
the sampler enclosure and shall have a passive, naturally ventilated sun
shield. The sensor shall be located such that the entire sun shield is
at least 5 cm above the horizontal plane of the sampler case or
enclosure (disregarding the inlet and downtube) and external to the
vertical plane of the nearest side or protuberance of the sampler case
or enclosure. The maximum temperature measurement error of the ambient
temperature measurement system shall be less than 1.6 [deg]C at 1 m/s
wind speed and 1000 W/m2 solar radiation intensity.
7.4.8.2 The ambient temperature sensor shall be of such a design and
mounted in such a way as to facilitate its convenient dismounting and
immersion in a liquid for calibration and comparison to the filter
temperature sensor, under section 7.4.11 of this appendix.
7.4.8.3 This ambient temperature measurement shall be updated at
least every 30 seconds during both sampling and standby (non-sampling)
modes of operation. A visual indication of the current (most recent)
value of the ambient temperature measurement, updated at least every 30
seconds, shall be available to the sampler operator during both sampling
and standby (non-sampling) modes of operation, as specified in table L-1
of section 7.4.19 of this appendix.
[[Page 101]]
7.4.8.4 This ambient temperature measurement shall be used for the
purpose of monitoring filter temperature deviation from ambient
temperature, as required by section 7.4.11 of this appendix, and may be
used for purposes of effecting filter temperature control, under section
7.4.10 of this appendix, or computation of volumetric flow rate, under
sections 7.4.1 to 7.4.5 of this appendix, if appropriate.
7.4.8.5 Following the end of each sample period, the sampler shall
report the maximum, minimum, and average temperature for the sample
period, as specified in table L-1 of section 7.4.19 of this appendix.
7.4.9 Ambient barometric sensor. The sampler shall have capability
to measure the barometric pressure of the air surrounding the sampler
over a range of 600 to 800 mm Hg referenced as described in reference 3
in section 13.0 of this appendix; also see part 53, subpart E of this
chapter. This barometric pressure measurement shall have a resolution of
5 mm Hg and an accuracy of 10 mm Hg and shall be
updated at least every 30 seconds. A visual indication of the value of
the current (most recent) barometric pressure measurement, updated at
least every 30 seconds, shall be available to the sampler operator
during both sampling and standby (non-sampling) modes of operation, as
specified in table L-1 of section 7.4.19 of this appendix. This
barometric pressure measurement may be used for purposes of computation
of volumetric flow rate, under sections 7.4.1 to 7.4.5 of this appendix,
if appropriate. Following the end of a sample period, the sampler shall
report the maximum, minimum, and mean barometric pressures for the
sample period, as specified in table L-1 of section 7.4.19 of this
appendix.
7.4.10 Filter temperature control (sampling and post-sampling). The
sampler shall provide a means to limit the temperature rise of the
sample filter (all sample filters for sequential samplers), from
insolation and other sources, to no more 5 [deg]C above the temperature
of the ambient air surrounding the sampler, during both sampling and
post-sampling periods of operation. The post-sampling period is the non-
sampling period between the end of the active sampling period and the
time of retrieval of the sample filter by the sampler operator.
7.4.11 Filter temperature sensor(s).
7.4.11.1 The sampler shall have the capability to monitor the
temperature of the sample filter (all sample filters for sequential
samplers) over the range of -30 to = 45 [deg]C during both sampling and
non-sampling periods. While the exact location of this temperature
sensor is not explicitly specified, the filter temperature measurement
system must demonstrate agreement, within 1 [deg]C, with a test
temperature sensor located within 1 cm of the center of the filter
downstream of the filter during both sampling and non-sampling modes, as
specified in the filter temperature measurement test described in part
53, subpart E of this chapter. This filter temperature measurement shall
have a resolution of 0.1 [deg]C and accuracy of 1.0 [deg]C, referenced as described in reference 3 in
section 13.0 of this appendix. This temperature sensor shall be of such
a design and mounted in such a way as to facilitate its reasonably
convenient dismounting and immersion in a liquid for calibration and
comparison to the ambient temperature sensor under section 7.4.8 of this
appendix.
7.4.11.2 The filter temperature measurement shall be updated at
least every 30 seconds during both sampling and standby (non-sampling)
modes of operation. A visual indication of the current (most recent)
value of the filter temperature measurement, updated at least every 30
seconds, shall be available to the sampler operator during both sampling
and standby (non-sampling) modes of operation, as specified in table L-1
of section 7.4.19 of this appendix.
7.4.11.3 For sequential samplers, the temperature of each filter
shall be measured individually unless it can be shown, as specified in
the filter temperature measurement test described in Sec. 53.57 of this
chapter, that the temperature of each filter can be represented by fewer
temperature sensors.
7.4.11.4 The sampler shall also provide a warning flag indicator
following any occurrence in which the filter temperature (any filter
temperature for sequential samplers) exceeds the ambient temperature by
more than 5 [deg]C for more than 30 consecutive minutes during either
the sampling or post-sampling periods of operation, as specified in
table L-1 of section 7.4.19 of this appendix, under section 10.12 of
this appendix, regarding sample validity when a warning flag occurs. It
is further recommended (not required) that the sampler be capable of
recording the maximum differential between the measured filter
temperature and the ambient temperature and its time and date of
occurrence during both sampling and post-sampling (non-sampling) modes
of operation and providing for those data to be accessible to the
sampler operator following the end of the sample period, as suggested in
table L-1 of section 7.4.19 of this appendix.
7.4.12 Clock/timer system.
(a) The sampler shall have a programmable real-time clock timing/
control system that:
(1) Is capable of maintaining local time and date, including year,
month, day-of-month, hour, minute, and second to an accuracy of 1.0 minute per month.
(2) Provides a visual indication of the current system time,
including year, month, day-of-month, hour, and minute, updated at least
each minute, for operator verification.
(3) Provides appropriate operator controls for setting the correct
local time and date.
[[Page 102]]
(4) Is capable of starting the sample collection period and sample
air flow at a specific, operator-settable time and date, and stopping
the sample air flow and terminating the sampler collection period 24
hours (1440 minutes) later, or at a specific, operator-settable time and
date.
(b) These start and stop times shall be readily settable by the
sampler operator to within 1.0 minute. The system
shall provide a visual indication of the current start and stop time
settings, readable to 1.0 minute, for verification
by the operator, and the start and stop times shall also be available
via the data output port, as specified in table L-1 of section 7.4.19 of
this appendix. Upon execution of a programmed sample period start, the
sampler shall automatically reset all sample period information and
warning flag indications pertaining to a previous sample period. Refer
also to section 7.4.15.4 of this appendix regarding retention of current
date and time and programmed start and stop times during a temporary
electrical power interruption.
7.4.13 Sample time determination. The sampler shall be capable of
determining the elapsed sample collection time for each PM2.5
sample, accurate to within 1.0 minute, measured as
the time between the start of the sampling period, under section 7.4.12
of this appendix and the termination of the sample period, under section
7.4.12 of this appendix or section 7.4.4 of this appendix. This elapsed
sample time shall not include periods when the sampler is inoperative
due to a temporary interruption of electrical power, under section
7.4.15.4 of this appendix. In the event that the elapsed sample time
determined for the sample period is not within the range specified for
the required sample period in section 3.3 of this appendix, the sampler
shall set a warning flag indicator. The date and time of the start of
the sample period, the value of the elapsed sample time for the sample
period, and the flag indicator status shall be available to the sampler
operator following the end of the sample period, as specified in table
L-1 of section 7.4.19 of this appendix.
7.4.14 Outdoor environmental enclosure. The sampler shall have an
outdoor enclosure (or enclosures) suitable to protect the filter and
other non-weatherproof components of the sampler from precipitation,
wind, dust, extremes of temperature and humidity; to help maintain
temperature control of the filter (or filters, for sequential samplers);
and to provide reasonable security for sampler components and settings.
7.4.15 Electrical power supply.
7.4.15.1 The sampler shall be operable and function as specified
herein when operated on an electrical power supply voltage of 105 to 125
volts AC (RMS) at a frequency of 59 to 61 Hz. Optional operation as
specified at additional power supply voltages and/or frequencies shall
not be precluded by this requirement.
7.4.15.2 The design and construction of the sampler shall comply
with all applicable National Electrical Code and Underwriters
Laboratories electrical safety requirements.
7.4.15.3 The design of all electrical and electronic controls shall
be such as to provide reasonable resistance to interference or
malfunction from ordinary or typical levels of stray electromagnetic
fields (EMF) as may be found at various monitoring sites and from
typical levels of electrical transients or electronic noise as may often
or occasionally be present on various electrical power lines.
7.4.15.4 In the event of temporary loss of electrical supply power
to the sampler, the sampler shall not be required to sample or provide
other specified functions during such loss of power, except that the
internal clock/timer system shall maintain its local time and date
setting within 1 minute per week, and the sampler
shall retain all other time and programmable settings and all data
required to be available to the sampler operator following each sample
period for at least 7 days without electrical supply power. When
electrical power is absent at the operator-set time for starting a
sample period or is interrupted during a sample period, the sampler
shall automatically start or resume sampling when electrical power is
restored, if such restoration of power occurs before the operator-set
stop time for the sample period.
7.4.15.5 The sampler shall have the capability to record and retain
a record of the year, month, day-of-month, hour, and minute of the start
of each power interruption of more than 1 minute duration, up to 10 such
power interruptions per sample period. (More than 10 such power
interruptions shall invalidate the sample, except where an exceedance is
measured, under section 3.3 of this appendix.) The sampler shall provide
for these power interruption data to be available to the sampler
operator following the end of the sample period, as specified in table
L-1 of section 7.4.19 of this appendix.
7.4.16 Control devices and operator interface. The sampler shall
have mechanical, electrical, or electronic controls, control devices,
electrical or electronic circuits as necessary to provide the timing,
flow rate measurement and control, temperature control, data storage and
computation, operator interface, and other functions specified.
Operator-accessible controls, data displays, and interface devices shall
be designed to be simple, straightforward, reliable, and easy to learn,
read, and operate under field conditions. The sampler shall have
provision for operator input and storage of up to 64 characters of
numeric (or alphanumeric) data for purposes of site, sampler, and sample
identification. This information shall be available to the sampler
operator for verification and
[[Page 103]]
change and for output via the data output port along with other data
following the end of a sample period, as specified in table L-1 of
section 7.4.19 of this appendix. All data required to be available to
the operator following a sample collection period or obtained during
standby mode in a post-sampling period shall be retained by the sampler
until reset, either manually by the operator or automatically by the
sampler upon initiation of a new sample collection period.
7.4.17 Data output port requirement. The sampler shall have a
standard RS-232C data output connection through which digital data may
be exported to an external data storage or transmission device. All
information which is required to be available at the end of each sample
period shall be accessible through this data output connection. The
information that shall be accessible though this output port is
summarized in table L-1 of section 7.4.19 of this appendix. Since no
specific format for the output data is provided, the sampler
manufacturer or vendor shall make available to sampler purchasers
appropriate computer software capable of receiving exported sampler data
and correctly translating the data into a standard spreadsheet format
and optionally any other formats as may be useful to sampler users. This
requirement shall not preclude the sampler from offering other types of
output connections in addition to the required RS-232C port.
7.4.18 Operation/instruction manual. The sampler shall include an
associated comprehensive operation or instruction manual, as required by
part 53 of this chapter, which includes detailed operating instructions
on the setup, operation, calibration, and maintenance of the sampler.
This manual shall provide complete and detailed descriptions of the
operational and calibration procedures prescribed for field use of the
sampler and all instruments utilized as part of this reference method.
The manual shall include adequate warning of potential safety hazards
that may result from normal use or malfunction of the method and a
description of necessary safety precautions. The manual shall also
include a clear description of all procedures pertaining to
installation, operation, periodic and corrective maintenance, and
troubleshooting, and shall include parts identification diagrams.
7.4.19 Data reporting requirements. The various information that the
sampler is required to provide and how it is to be provided is
summarized in the following table L-1.
Table L-1 to Appendix L of Part 50--Summary of Information To Be Provided by the Sampler
--------------------------------------------------------------------------------------------------------------------------------------------------------
Availability Format
Appendix L section -------------------------------------------------------------------------------------------------
Information to be provided reference End of Visual Data output
Anytime \1\ period \2\ display \3\ \4\ Digital reading \5\ Units
--------------------------------------------------------------------------------------------------------------------------------------------------------
Flow rate, 30-second maximum 7.4.5.1............ [check] ............ [check] * XX.X............... L/min
interval.
Flow rate, average for the sample 7.4.5.2............ * [check] * [check] XX.X............... L/min
period.
Flow rate, CV, for sample period. 7.4.5.2............ * [check] * [check] XX.X............... %
Flow rate, 5-min. average out of 7.4.5.2............ [check] [check] [check] [check][squf On/Off
spec. (FLAG \6\). ]
Sample volume, total............. 7.4.5.2............ * [check] [check] [check] XX.X............... m\3\
Temperature, ambient, 30-second 7.4.8.............. [check] ............ [check] ............ XX.X............... [deg]C
interval.
Temperature, ambient, min., max., 7.4.8.............. * [check] [check] [check][squf XX.X............... [deg]C
average for the sample period. ]
Baro. pressure, ambient, 30- 7.4.9.............. [check] ............ [check] ............ XXX................ mm Hg
second interval.
Baro. pressure, ambient, min., 7.4.9.............. * [check] [check] [check][squf XXX................ mm Hg
max., average for the sample ]
period.
Filter temperature, 30-second 7.4.11............. [check] ............ [check] ............ XX.X............... [deg]C
interval.
[[Page 104]]
Filter temp. differential, 30- 7.4.11............. * [check] [check] [check][squf On/Off
second interval, out of spec. ]
(FLAG \6\).
Filter temp., maximum 7.4.11............. * * * * X.X, YY/MM/DD HH.mm [deg]C, Yr/Mon/Day
differential from ambient, date, Hrs. min
time of occurrence.
Date and Time.................... 7.4.12............. [check] ............ [check] ............ YY/MM/DD HH.mm..... Yr/Mon/Day Hrs. min
Sample start and stop time 7.4.12............. [check] [check] [check] [check] YY/MM/DD HH.mm..... Yr/Mon/Day Hrs. min
settings.
Sample period start time......... 7.4.12............. ............ [check] [check] [check] YY/MM/DD HH.mm..... Yr/Mon/Day Hrs. min
Elapsed sample time.............. 7.4.13............. * [check] [check] [check] HH.mm.............. Hrs. min
Elapsed sample time, out of spec. 7.4.13............. ............ [check] [check] [check][squf On/Off
(FLAG \6\). ]
Power interruptions <=1 min., 7.4.15.5........... * [check] * [check] 1HH.mm, 2HH.mm, Hrs. min
start time of first 10. etc..
User-entered information, such as 7.4.16............. [check] [check] [check] [check][squf As entered ........
sampler and site identification. ]
--------------------------------------------------------------------------------------------------------------------------------------------------------
[check] Provision of this information is required.
* Provision of this information is optional. If information related to the entire sample period is optionally provided prior to the end of the sample
period, the value provided should be the value calculated for the portion of the sampler period completed up to the time the information is provided.
[squf] Indicates that this information is also required to be provided to the Air Quality System (AQS) data bank; see Sec. 58.16 of this chapter. For
ambient temperature and barometric pressure, only the average for the sample period must be reported.
1. Information is required to be available to the operator at any time the sampler is operating, whether sampling or not.
2. Information relates to the entire sampler period and must be provided following the end of the sample period until reset manually by the operator or
automatically by the sampler upon the start of a new sample period.
3. Information shall be available to the operator visually.
4. Information is to be available as digital data at the sampler's data output port specified in section 7.4.16 of this appendix following the end of
the sample period until reset manually by the operator or automatically by the sampler upon the start of a new sample period.
5. Digital readings, both visual and data output, shall have not less than the number of significant digits and resolution specified.
6. Flag warnings may be displayed to the operator by a single flag indicator or each flag may be displayed individually. Only a set (on) flag warning
must be indicated; an off (unset) flag may be indicated by the absence of a flag warning. Sampler users should refer to section 10.12 of this appendix
regarding the validity of samples for which the sampler provided an associated flag warning.
8.0 Filter Weighing. See reference 2 in section 13.0 of this
appendix, for additional, more detailed guidance.
8.1 Analytical balance. The analytical balance used to weigh filters
must be suitable for weighing the type and size of filters specified,
under section 6.0 of this appendix, and have a readability of 1 [micro]g. The balance shall be calibrated as specified
by the manufacturer at installation and recalibrated immediately prior
to each weighing session. See reference 2 in section 13.0 of this
appendix for additional guidance.
8.2 Filter conditioning. All sample filters used shall be
conditioned immediately before both the pre- and post-sampling weighings
as specified below. See reference 2 in section 13.0 of this appendix for
additional guidance.
8.2.1 Mean temperature. 20 - 23 [deg]C.
8.2.2 Temperature control. 2 [deg]C over 24
hours.
8.2.3 Mean humidity. Generally, 30-40 percent relative humidity;
however, where it can be shown that the mean ambient relative humidity
during sampling is less than 30 percent, conditioning is permissible at
a mean
[[Page 105]]
relative humidity within 5 relative humidity
percent of the mean ambient relative humidity during sampling, but not
less than 20 percent.
8.2.4 Humidity control. 5 relative humidity
percent over 24 hours.
8.2.5 Conditioning time. Not less than 24 hours.
8.3 Weighing procedure.
8.3.1 New filters should be placed in the conditioning environment
immediately upon arrival and stored there until the pre-sampling
weighing. See reference 2 in section 13.0 of this appendix for
additional guidance.
8.3.2 The analytical balance shall be located in the same controlled
environment in which the filters are conditioned. The filters shall be
weighed immediately following the conditioning period without
intermediate or transient exposure to other conditions or environments.
8.3.3 Filters must be conditioned at the same conditions (humidity
within 5 relative humidity percent) before both
the pre- and post-sampling weighings.
8.3.4 Both the pre- and post-sampling weighings should be carried
out on the same analytical balance, using an effective technique to
neutralize static charges on the filter, under reference 2 in section
13.0 of this appendix. If possible, both weighings should be carried out
by the same analyst.
8.3.5 The pre-sampling (tare) weighing shall be within 30 days of
the sampling period.
8.3.6 The post-sampling conditioning and weighing shall be completed
within 240 hours (10 days) after the end of the sample period, unless
the filter sample is maintained at temperatures below the average
ambient temperature during sampling (or 4 [deg]C or below for average
sampling temperatures less than 4 [deg]C) during the time between
retrieval from the sampler and the start of the conditioning, in which
case the period shall not exceed 30 days. Reference 2 in section 13.0 of
this appendix has additional guidance on transport of cooled filters.
8.3.7 Filter blanks.
8.3.7.1 New field blank filters shall be weighed along with the pre-
sampling (tare) weighing of each lot of PM2.5 filters. These
blank filters shall be transported to the sampling site, installed in
the sampler, retrieved from the sampler without sampling, and reweighed
as a quality control check.
8.3.7.2 New laboratory blank filters shall be weighed along with the
pre-sampling (tare) weighing of each set of PM2.5 filters.
These laboratory blank filters should remain in the laboratory in
protective containers during the field sampling and should be reweighed
as a quality control check.
8.3.8 Additional guidance for proper filter weighing and related
quality assurance activities is provided in reference 2 in section 13.0
of this appendix.
9.0 Calibration. Reference 2 in section 13.0 of this appendix
contains additional guidance.
9.1 General requirements.
9.1.1 Multipoint calibration and single-point verification of the
sampler's flow rate measurement device must be performed periodically to
establish and maintain traceability of subsequent flow measurements to a
flow rate standard.
9.1.2 An authoritative flow rate standard shall be used for
calibrating or verifying the sampler's flow rate measurement device with
an accuracy of 2 percent. The flow rate standard
shall be a separate, stand-alone device designed to connect to the flow
rate measurement adapter, Figure L-30 of this appendix. This flow rate
standard must have its own certification and be traceable to a National
Institute of Standards and Technology (NIST) primary standard for volume
or flow rate. If adjustments to the sampler's flow rate measurement
system calibration are to be made in conjunction with an audit of the
sampler's flow measurement system, such adjustments shall be made
following the audit. Reference 2 in section 13.0 of this appendix
contains additional guidance.
9.1.3 The sampler's flow rate measurement device shall be re-
calibrated after electromechanical maintenance or transport of the
sampler.
9.2 Flow rate calibration/verification procedure.
9.2.1 PM2.5 samplers may employ various types of flow
control and flow measurement devices. The specific procedure used for
calibration or verification of the flow rate measurement device will
vary depending on the type of flow rate controller and flow rate
measurement employed. Calibration shall be in terms of actual ambient
volumetric flow rates (Q\a\), measured at the sampler's inlet downtube.
The generic procedure given here serves to illustrate the general steps
involved in the calibration of a PM2.5 sampler. The sampler
operation/instruction manual required under section 7.4.18 of this
appendix and the Quality Assurance Handbook in reference 2 in section
13.0 of this appendix provide more specific and detailed guidance for
calibration.
9.2.2 The flow rate standard used for flow rate calibration shall
have its own certification and be traceable to a NIST primary standard
for volume or flow rate. A calibration relationship for the flow rate
standard, e.g., an equation, curve, or family of curves relating actual
flow rate (Qa) to the flow rate indicator reading, shall be
established that is accurate to within 2 percent over the expected range
of ambient temperatures and pressures at which the flow rate standard
may be used. The flow rate standard must be re-calibrated or re-verified
at least annually.
9.2.3 The sampler flow rate measurement device shall be calibrated
or verified by removing the sampler inlet and connecting the
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flow rate standard to the sampler's downtube in accordance with the
operation/instruction manual, such that the flow rate standard
accurately measures the sampler's flow rate. The sampler operator shall
first carry out a sampler leak check and confirm that the sampler passes
the leak test and then verify that no leaks exist between the flow rate
standard and the sampler.
9.2.4 The calibration relationship between the flow rate (in actual
L/min) indicated by the flow rate standard and by the sampler's flow
rate measurement device shall be established or verified in accordance
with the sampler operation/instruction manual. Temperature and pressure
corrections to the flow rate indicated by the flow rate standard may be
required for certain types of flow rate standards. Calibration of the
sampler's flow rate measurement device shall consist of at least three
separate flow rate measurements (multipoint calibration) evenly spaced
within the range of -10 percent to = 10 percent of the sampler's
operational flow rate, section 7.4.1 of this appendix. Verification of
the sampler's flow rate shall consist of one flow rate measurement at
the sampler's operational flow rate. The sampler operation/instruction
manual and reference 2 in section 13.0 of this appendix provide
additional guidance.
9.2.5 If during a flow rate verification the reading of the
sampler's flow rate indicator or measurement device differs by 4 percent or more from the flow rate measured by the
flow rate standard, a new multipoint calibration shall be performed and
the flow rate verification must then be repeated.
9.2.6 Following the calibration or verification, the flow rate
standard shall be removed from the sampler and the sampler inlet shall
be reinstalled. Then the sampler's normal operating flow rate (in L/min)
shall be determined with a clean filter in place. If the flow rate
indicated by the sampler differs by 2 percent or
more from the required sampler flow rate, the sampler flow rate must be
adjusted to the required flow rate, under section 7.4.1 of this
appendix.
9.3 Periodic calibration or verification of the calibration of the
sampler's ambient temperature, filter temperature, and barometric
pressure measurement systems is also required. Reference 3 of section
13.0 of this appendix contains additional guidance.
10.0 PM2.5 Measurement Procedure. The detailed procedure
for obtaining valid PM2.5 measurements with each specific
sampler designated as part of a reference method for PM2.5
under part 53 of this chapter shall be provided in the sampler-specific
operation or instruction manual required by section 7.4.18 of this
appendix. Supplemental guidance is provided in section 2.12 of the
Quality Assurance Handbook listed in reference 2 in section 13.0 of this
appendix. The generic procedure given here serves to illustrate the
general steps involved in the PM2.5 sample collection and
measurement, using a PM2.5 reference method sampler.
10.1 The sampler shall be set up, calibrated, and operated in
accordance with the specific, detailed guidance provided in the specific
sampler's operation or instruction manual and in accordance with a
specific quality assurance program developed and established by the
user, based on applicable supplementary guidance provided in reference 2
in section 13.0 of this appendix.
10.2 Each new sample filter shall be inspected for correct type and
size and for pinholes, particles, and other imperfections. Unacceptable
filters should be discarded. A unique identification number shall be
assigned to each filter, and an information record shall be established
for each filter. If the filter identification number is not or cannot be
marked directly on the filter, alternative means, such as a number-
identified storage container, must be established to maintain positive
filter identification.
10.3 Each filter shall be conditioned in the conditioning
environment in accordance with the requirements specified in section 8.2
of this appendix.
10.4 Following conditioning, each filter shall be weighed in
accordance with the requirements specified in section 8.0 of this
appendix and the presampling weight recorded with the filter
identification number.
10.5 A numbered and preweighed filter shall be installed in the
sampler following the instructions provided in the sampler operation or
instruction manual.
10.6 The sampler shall be checked and prepared for sample collection
in accordance with instructions provided in the sampler operation or
instruction manual and with the specific quality assurance program
established for the sampler by the user.
10.7 The sampler's timer shall be set to start the sample collection
at the beginning of the desired sample period and stop the sample
collection 24 hours later.
10.8 Information related to the sample collection (site location or
identification number, sample date, filter identification number, and
sampler model and serial number) shall be recorded and, if appropriate,
entered into the sampler.
10.9 The sampler shall be allowed to collect the PM2.5
sample during the set 24-hour time period.
10.10 Within 177 hours (7 days, 9 hours) of the end of the sample
collection period, the filter, while still contained in the filter
cassette, shall be carefully removed from the sampler, following the
procedure provided in the sampler operation or instruction manual and
the quality assurance program, and placed in a protective container. The
protective container shall contain no loose material that could be
transferred to the filter. The protective container shall hold the
filter
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cassette securely such that the cover shall not come in contact with the
filter's surfaces. Reference 2 in section 13.0 of this appendix contains
additional information.
10.11 The total sample volume in actual m\3\ for the sampling period
and the elapsed sample time shall be obtained from the sampler and
recorded in accordance with the instructions provided in the sampler
operation or instruction manual. All sampler warning flag indications
and other information required by the local quality assurance program
shall also be recorded.
10.12 All factors related to the validity or representativeness of
the sample, such as sampler tampering or malfunctions, unusual
meteorological conditions, construction activity, fires or dust storms,
etc. shall be recorded as required by the local quality assurance
program. The occurrence of a flag warning during a sample period shall
not necessarily indicate an invalid sample but rather shall indicate the
need for specific review of the QC data by a quality assurance officer
to determine sample validity.
10.13 After retrieval from the sampler, the exposed filter
containing the PM2.5 sample should be transported to the
filter conditioning environment as soon as possible, ideally to arrive
at the conditioning environment within 24 hours for conditioning and
subsequent weighing. During the period between filter retrieval from the
sampler and the start of the conditioning, the filter shall be
maintained as cool as practical and continuously protected from exposure
to temperatures over 25 [deg]C to protect the integrity of the sample
and minimize loss of volatile components during transport and storage.
See section 8.3.6 of this appendix regarding time limits for completing
the post-sampling weighing. See reference 2 in section 13.0 of this
appendix for additional guidance on transporting filter samplers to the
conditioning and weighing laboratory.
10.14. The exposed filter containing the PM2.5 sample
shall be re-conditioned in the conditioning environment in accordance
with the requirements specified in section 8.2 of this appendix.
10.15. The filter shall be reweighed immediately after conditioning
in accordance with the requirements specified in section 8.0 of this
appendix, and the postsampling weight shall be recorded with the filter
identification number.
10.16 The PM2.5 concentration shall be calculated as
specified in section 12.0 of this appendix.
11.0 Sampler Maintenance. The sampler shall be maintained as
described by the sampler's manufacturer in the sampler-specific
operation or instruction manual required under section 7.4.18 of this
appendix and in accordance with the specific quality assurance program
developed and established by the user based on applicable supplementary
guidance provided in reference 2 in section 13.0 of this appendix.
12.0 Calculations
12.1 (a) The PM2.5 concentration is calculated as:
PM2.5 = (Wf - Wi)/Va
where:
PM2.5 = mass concentration of PM2.5, [micro]g/
m\3\;
Wf, Wi = final and initial weights, respectively,
of the filter used to collect the PM2.5 particle
sample, [micro]g;
Va = total air volume sampled in actual volume units, as
provided by the sampler, m\3\.
Note: Total sample time must be between 1,380 and 1,500 minutes (23
and 25 hrs) for a fully valid PM2.5 sample; however, see also
section 3.3 of this appendix.
13.0 References.
1. Quality Assurance Handbook for Air Pollution Measurement Systems,
Volume I, Principles. EPA/600/R-94/038a, April 1994. Available from
CERI, ORD Publications, U.S. Environmental Protection Agency, 26 West
Martin Luther King Drive, Cincinnati, Ohio 45268.
2. Quality Assurance Guidance Document 2.12. Monitoring
PM2.5 in Ambient Air Using Designated Reference or Class I
Equivalent Methods. U.S. EPA, National Exposure Research Laboratory.
Research Triangle Park, NC, November 1988 or later edition. Currently
available at: http://www.epa.gov/ttn/amtic/pmqainf.html.
3. Quality Assurance Handbook for Air Pollution Measurement Systems,
Volume IV: Meteorological Measurements, (Revised Edition) EPA/600/R-94/
038d, March, 1995. Available from CERI, ORD Publications, U.S.
Environmental Protection Agency, 26 West Martin Luther King Drive,
Cincinnati, Ohio 45268.
4. Military standard specification (mil. spec.) 8625F, Type II,
Class 1 as listed in Department of Defense Index of Specifications and
Standards (DODISS), available from DODSSP-Customer Service,
Standardization Documents Order Desk, 700 Robbins Avenue, Building 4D,
Philadelphia, PA 1911-5094.
14.0 Figures L-1 through L-30 to Appendix L.
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[62 FR 38714, July 18, 1997, as amended at 64 FR 19719, Apr. 22, 1999;
71 FR 61226, Oct. 17, 2006]
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Sec. Appendix M to Part 50 [Reserved]
Sec. Appendix N to Part 50--Interpretation of the National Ambient Air
Quality Standards for PM2.5
1.0 General
(a) This appendix explains the data handling conventions and
computations necessary for determining when the national ambient air
quality standards (NAAQS) for PM2.5 are met, specifically the
primary and secondary annual and 24-hour PM2.5 NAAQS
specified in Sec. 50.7, 50.13, and 50.18. PM2.5 is defined,
in general terms, as particles with an aerodynamic diameter less than or
equal to a nominal 2.5 micrometers. PM2.5 mass concentrations
are measured in the ambient air by a Federal Reference Method (FRM)
based on appendix L of this part, as applicable, and designated in
accordance with part 53 of this chapter; or by a Federal Equivalent
Method (FEM) designated in accordance with part 53 of this chapter; or
by an Approved Regional Method (ARM) designated in accordance with part
58 of this chapter. Only those FRM, FEM, and ARM measurements that are
derived in accordance with part 58 of this chapter (i.e., that are
deemed ``suitable'') shall be used in comparisons with the
PM2.5 NAAQS. The data handling and computation procedures to
be used to construct annual and 24-hour NAAQS metrics from reported
PM2.5 mass concentrations, and the associated instructions
for comparing these calculated metrics to the levels of the
PM2.5 NAAQS, are specified in sections 2.0, 3.0, and 4.0 of
this appendix.
(b) Decisions to exclude, retain, or make adjustments to the data
affected by exceptional events, including natural events, are made
according to the requirements and process deadlines specified in
Sec. Sec. 50.1, 50.14 and 51.930 of this chapter.
(c) The terms used in this appendix are defined as follows:
Annual mean refers to a weighted arithmetic mean, based on quarterly
means, as defined in section 4.4 of this appendix.
The Air Quality System (AQS) is EPA's official repository of ambient
air data.
Collocated monitors refers to two or more air measurement
instruments for the same parameter (e.g., PM2.5 mass)
operated at the same site location, and whose placement is consistent
with Sec. 53.1 of this chapter. For purposes of considering a combined
site record in this appendix, when two or more monitors are operated at
the same site, one monitor is designated as the ``primary'' monitor with
any additional monitors designated as ``collocated.'' It is implicit in
these appendix procedures that the primary monitor and collocated
monitor(s) are all deemed suitable for the applicable NAAQS comparison;
however, it is not a requirement that the primary and monitors utilize
the same specific sampling and analysis method.
Combined site data record is the data set used for performing
calculations in appendix N. It represents data for the primary monitors
augmented with data from collocated monitors according to the procedure
specified in section 3.0(d) of this appendix.
Creditable samples are daily values in the combined site record that
are given credit for data completeness. The number of creditable samples
(cn) for a given year also governs which value in the sorted series of
daily values represents the 98th percentile for that year. Creditable
samples include daily values collected on scheduled sampling days and
valid make-up samples taken for missed or invalidated samples on
scheduled sampling days.
Daily values refer to the 24-hour average concentrations of
PM2.5 mass measured (or averaged from hourly measurements in
AQS) from midnight to midnight (local standard time) from suitable
monitors.
Data substitution tests are diagnostic evaluations performed on an
annual PM2.5 NAAQS design value (DV) or a 24-hour
PM2.5 NAAQS DV to determine if those metrics, which are
judged to be based on incomplete data in accordance with 4.1(b) or
4.2(b) of this appendix shall nevertheless be deemed valid for NAAQS
comparisons, or alternatively, shall still be considered incomplete and
not valid for NAAQS comparisons. There are two data substitution tests,
the ``minimum quarterly value'' test and the ``maximum quarterly value''
test. Design values (DVs) are the 3-year average NAAQS metrics that are
compared to the NAAQS levels to determine when a monitoring site meets
or does not meet the NAAQS, calculated as shown in section 4. There are
two separate DVs specified in this appendix:
(1) The 3-year average of PM2.5 annual mean mass
concentrations for each eligible monitoring site is referred to as the
``annual PM2.5 NAAQS DV''.
(2) The 3-year average of annual 98th percentile 24-hour average
PM2.5 mass concentration values recorded at each eligible
monitoring site is referred to as the ``24-hour (or daily) PM2.5 NAAQS
DV''.
Eligible sites are monitoring stations that meet the criteria
specified in Sec. 58.11 and Sec. 58.30 of this chapter, and thus are
approved for comparison to the annual PM2.5 NAAQS. For the
24-hour PM2.5 NAAQS, all site locations that meet the
criteria specified in Sec. 58.11 are approved (i.e., eligible) for
NAAQS comparisons.
Extra samples are non-creditable samples. They are daily values that
do not occur on scheduled sampling days and that cannot be used as make-
up samples for missed or invalidated scheduled samples. Extra samples
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are used in mean calculations and are included in the series of all
daily values subject to selection as a 98th percentile value, but are
not used to determine which value in the sorted list represents the 98th
percentile.
Make-up samples are samples collected to take the place of missed or
invalidated required scheduled samples. Make-up samples can be made by
either the primary or the collocated monitor. Make-up samples are either
taken before the next required sampling day or exactly one week after
the missed (or voided) sampling day.
The maximum quarterly value data substitution test substitutes
actual ``high'' reported daily PM2.5 values from the same
site (specifically, the highest reported non-excluded quarterly value(s)
(year non-specific) contained in the combined site record for the
evaluated 3-year period) for missing daily values.
The minimum quarterly value data substitution test substitutes
actual ``low'' reported daily PM2.5 values from the same site
(specifically, the lowest reported quarterly value(s) (year non-
specific) contained in the combined site record for the evaluated 3-year
period) for missing daily values.
98th percentile is the smallest daily value out of a year of
PM2.5 mass monitoring data below which no more than 98
percent of all daily values fall using the ranking and selection method
specified in section 4.5(a) of this appendix.
Primary monitors are suitable monitors designated by a state or
local agency in their annual network plan (and in AQS) as the default
data source for creating a combined site record for purposes of NAAQS
comparisons. If there is only one suitable monitor at a particular site
location, then it is presumed to be a primary monitor.
Quarter refers to a calendar quarter (e.g., January through March).
Quarterly data capture rate is the percentage of scheduled samples
in a calendar quarter that have corresponding valid reported sample
values. Quarterly data capture rates are specifically calculated as the
number of creditable samples for the quarter divided by the number of
scheduled samples for the quarter, the result then multiplied by 100 and
rounded to the nearest integer.
Scheduled PM2.5 samples refers to those reported daily values which
are consistent with the required sampling frequency (per Sec. 58.12 of
this chapter) for the primary monitor, or those that meet the special
exception noted in section 3.0(e) of this appendix.
Seasonal sampling is the practice of collecting data at a reduced
frequency during a season of expected low concentrations.
Suitable monitors are instruments that use sampling and analysis
methods approved for NAAQS comparisons. For the annual and 24-hour
PM2.5 NAAQS, suitable monitors include all FRMs, and all
FEMs/ARMs except those specific continuous FEMs/ARMs disqualified by a
particular monitoring agency network in accordance with Sec.
58.10(b)(13) and approved by the EPA Regional Administrator per Sec.
58.11(e) of this chapter.
Test design values (TDV) are numerical values that used in the data
substitution tests described in sections 4.1(c)(i), 4.1(c)(ii) and
4.2(c)(i) of this appendix to determine if the PM2.5 NAAQS DV
with incomplete data are judged to be valid for NAAQS comparisons. There
are two TDVs: TDVmin to determine if the NAAQS is not met and
is used in the ``minimum quarterly value'' data substitution test and
TDVmax to determine if the NAAQS is met and is used in the
``maximum quarterly value'' data substitution test. These TDV's are
derived by substituting historically low or historically high daily
concentration values for missing data in an incomplete year(s).
Year refers to a calendar year.
2.0 Monitoring Considerations
(a) Section 58.30 of this chapter provides special considerations
for data comparisons to the annual PM2.5 NAAQS.
(b) Monitors meeting the network technical requirements detailed in
Sec. 58.11 of this chapter are suitable for comparison with the NAAQS
for PM2.5.
(c) Section 58.12 of this chapter specifies the required minimum
frequency of sampling for PM2.5. Exceptions to the specified
sampling frequencies, such as seasonal sampling, are subject to the
approval of the EPA Regional Administrator and must be documented in the
state or local agency Annual Monitoring Network Plan as required in
Sec. 58.10 of this chapter and also in AQS.
3.0 Requirements for Data Use and Data Reporting for Comparisons With
the NAAQS for PM2.5
(a) Except as otherwise provided in this appendix, all valid FRM/
FEM/ARM PM2.5 mass concentration data produced by suitable
monitors that are required to be submitted to AQS, or otherwise
available to EPA, meeting the requirements of part 58 of this chapter
including appendices A, C, and E shall be used in the DV calculations.
Generally, EPA will only use such data if they have been certified by
the reporting organization (as prescribed by Sec. 58.15 of this
chapter); however, data not certified by the reporting organization can
nevertheless be used, if the deadline for certification has passed and
EPA judges the data to be complete and accurate.
(b) PM2.5 mass concentration data (typically collected
hourly for continuous instruments and daily for filter-based
instruments) shall be reported to AQS in micrograms per cubic meter
([micro]g/m\3\) to at least one decimal place. If concentrations are
reported to one
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decimal place, additional digits to the right of the tenths decimal
place shall be truncated. If concentrations are reported to AQS with
more than one decimal place, AQS will truncate the value to one decimal
place for NAAQS usage (i.e., for implementing the procedures in this
appendix). In situations where suitable PM2.5 data are
available to EPA but not reported to AQS, the same truncation protocol
shall be applied to that data. In situations where PM2.5 mass
data are submitted to AQS, or are otherwise available, with less
precision than specified above, these data shall nevertheless still be
deemed appropriate for NAAQS usage.
(c) Twenty-four-hour average concentrations will be computed in AQS
from submitted hourly PM2.5 concentration data for each
corresponding day of the year and the result will be stored in the
first, or start, hour (i.e., midnight, hour `0') of the 24-hour period.
A 24-hour average concentration shall be considered valid if at least 75
percent of the hourly averages (i.e., 18 hourly values) for the 24-hour
period are available. In the event that less than all 24 hourly average
concentrations are available (i.e., less than 24, but at least 18), the
24-hour average concentration shall be computed on the basis of the
hours available using the number of available hours within the 24-hour
period as the divisor (e.g., 19, if 19 hourly values are available).
Twenty-four-hour periods with seven or more missing hours shall also be
considered valid if, after substituting zero for all missing hourly
concentrations, the resulting 24-hour average daily value is greater
than the level of the 24-hour PM2.5 NAAQS (i.e., greater than
or equal to 35.5 [micro]g/m\3\). Twenty-four hour average
PM2.5 mass concentrations that are averaged in AQS from
hourly values will be truncated to one decimal place, consistent with
the data handling procedure for the reported hourly (and also 24-hour
filter-based) data.
(d) All calculations shown in this appendix shall be implemented on
a site-level basis. Site level concentration data shall be processed as
follows:
(1) The default dataset for PM2.5 mass concentrations for
a site shall consist of the measured concentrations recorded from the
designated primary monitor(s). All daily values produced by the primary
monitor are considered part of the site record; this includes all
creditable samples and all extra samples.
(2) Data for the primary monitors shall be augmented as much as
possible with data from collocated monitors. If a valid daily value is
not produced by the primary monitor for a particular day (scheduled or
otherwise), but a value is available from a collocated monitor, then
that collocated value shall be considered part of the combined site data
record. If more than one collocated daily value is available, the
average of those valid collocated values shall be used as the daily
value. The data record resulting from this procedure is referred to as
the ``combined site data record.''
(e) All daily values in a combined site data record are used in the
calculations specified in this appendix; however, not all daily values
are given credit towards data completeness requirements. Only creditable
samples are given credit for data completeness. Creditable samples
include daily values in the combined site record that are collected on
scheduled sampling days and valid make-up samples taken for missed or
invalidated samples on scheduled sampling days. Days are considered
scheduled according to the required sampling frequency of the designated
primary monitor with one exception. The exception is, if a collocated
continuous FEM/ARM monitor has a more intensive sampling frequency than
the primary FRM monitor, then samples contributed to the combined site
record from that continuous FEM/ARM monitor are always considered
scheduled and, hence, also creditable. Daily values in the combined site
data record that are reported for nonscheduled days, but that are not
valid make-up samples are referred to as extra samples.
4.0 Comparisons With the Annual and 24-Hour PM2.5 NAAQS
4.1 Annual PM2.5 NAAQS
(a) The primary annual PM2.5 NAAQS is met when the annual
PM2.5 NAAQS DV is less than or equal to 12.0 [micro]g/m\3\ at
each eligible monitoring site. The secondary annual PM2.5
NAAQS is met when the annual PM2.5 NAAQS DV is less than or
equal to 15.0 [micro]g/m\3\ at each eligible monitoring site.
(b) Three years of valid annual means are required to produce a
valid annual PM2.5 NAAQS DV. A year meets data completeness
requirements when quarterly data capture rates for all four quarters are
at least 75 percent. However, years with at least 11 creditable samples
in each quarter shall also be considered valid if the resulting annual
mean or resulting annual PM2.5 NAAQS DV (rounded according to
the conventions of section 4.3 of this appendix) is greater than the
level of the applicable primary or secondary annual PM2.5
NAAQS. Furthermore, where the explicit 75 percent data capture and/or 11
sample minimum requirements are not met, the 3-year annual
PM2.5 NAAQS DV shall still be considered valid if it passes
at least one of the two data substitution tests stipulated below.
(c) In the case of one, two, or three years that do not meet the
completeness requirements of section 4.1(b) of this appendix and thus
would normally not be useable for the calculation of a valid annual
PM2.5 NAAQS DV, the annual PM2.5 NAAQS DV shall
nevertheless be considered valid if one of the test
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conditions specified in sections 4.1(c)(i) and 4.1(c)(ii) of this
appendix is met.
(i) An annual PM2.5 NAAQS DV that is above the level of
the NAAQS can be validated if it passes the minimum quarterly value data
substitution test. This type of data substitution is permitted only if
there are at least 30 days across the three quarters of the three years
under consideration (e.g., collectively, quarter 1 of year 1, quarter 1
of year 2 and quarter 1 of year 3) from which to select the quarter-
specific low value. Data substitution will be performed in all quarter
periods that have less than 11 creditable samples.
Procedure: Identify for each deficient quarter (i.e., those with
less than 11 creditable samples) the lowest reported daily value for
that quarter, looking across those three months of all three years under
consideration. If after substituting the lowest reported daily value for
a quarter for (11- cn) daily values in the matching deficient quarter(s)
(i.e., to bring the creditable number for those quarters up to 11), the
procedure yields a recalculated annual PM2.5 NAAQS test DV
(TDVmin) that is greater than the level of the standard, then
the annual PM2.5 NAAQS DV is deemed to have passed the
diagnostic test and is valid, and the annual PM2.5 NAAQS is
deemed to have been violated in that 3-year period.
(ii) An annual PM2.5 NAAQS DV that is equal to or below
the level of the NAAQS can be validated if it passes the maximum
quarterly value data substitution test. This type of data substitution
is permitted only if there is at least 50 percent data capture in each
quarter that is deficient of 75 percent data capture in each of the
three years under consideration. Data substitution will be performed in
all quarter periods that have less than 75 percent data capture but at
least 50 percent data capture. If any quarter has less than 50 percent
data capture then this substitution test cannot be used.
Procedure: Identify for each deficient quarter (i.e., those with
less than 75 percent but at least 50 percent data capture) the highest
reported daily value for that quarter, excluding state-flagged data
affected by exceptional events which have been approved for exclusion by
the Administrator, looking across those three quarters of all three
years under consideration. If after substituting the highest reported
daily PM2.5 value for a quarter for all missing daily data in
the matching deficient quarter(s) (i.e., to make those quarters 100
percent complete), the procedure yields a recalculated annual
PM2.5 NAAQS test DV (TDVmax) that is less than or
equal to the level of the standard, then the annual PM2.5
NAAQS DV is deemed to have passed the diagnostic test and is valid, and
the annual PM2.5 NAAQS is deemed to have been met in that 3-
year period.
(d) An annual PM2.5 NAAQS DV based on data that do not
meet the completeness criteria stated in 4(b) and also do not satisfy
the test conditions specified in section 4(c), may also be considered
valid with the approval of, or at the initiative of, the EPA
Administrator, who may consider factors such as monitoring site
closures/moves, monitoring diligence, the consistency and levels of the
daily values that are available, and nearby concentrations in
determining whether to use such data.
(e) The equations for calculating the annual PM2.5 NAAQS
DVs are given in section 4.4 of this appendix.
4.2 Twenty-four-hour PM2.5 NAAQS
(a) The primary and secondary 24-hour PM2.5 NAAQS are met
when the 24-hour PM2.5 NAAQS DV at each eligible monitoring
site is less than or equal to 35 [micro]g/m\3\.
(b) Three years of valid annual PM2.5 98th percentile
mass concentrations are required to produce a valid 24-hour
PM2.5 NAAQS DV. A year meets data completeness requirements
when quarterly data capture rates for all four quarters are at least 75
percent. However, years shall be considered valid, notwithstanding
quarters with less than complete data (even quarters with less than 11
creditable samples, but at least one creditable sample must be present
for the year), if the resulting annual 98th percentile value or
resulting 24-hour NAAQS DV (rounded according to the conventions of
section 4.3 of this appendix) is greater than the level of the standard.
Furthermore, where the explicit 75 percent quarterly data capture
requirement is not met, the 24-hour PM2.5 NAAQS DV shall
still be considered valid if it passes the maximum quarterly value data
substitution test.
(c) In the case of one, two, or three years that do not meet the
completeness requirements of section 4.2(b) of this appendix and thus
would normally not be useable for the calculation of a valid 24-hour
PM2.5 NAAQS DV, the 24-hour PM2.5 NAAQS DV shall
nevertheless be considered valid if the test conditions specified in
section 4.2(c)(i) of this appendix are met.
(i) A PM2.5 24-hour mass NAAQS DV that is equal to or
below the level of the NAAQS can be validated if it passes the maximum
quarterly value data substitution test. This type of data substitution
is permitted only if there is at least 50 percent data capture in each
quarter that is deficient of 75 percent data capture in each of the
three years under consideration. Data substitution will be performed in
all quarters that have less than 75 percent data capture but at least 50
percent data capture. If any quarter has less than 50 percent data
capture then this substitution test cannot be used.
Procedure: Identify for each deficient quarter (i.e., those with
less than 75 percent but
[[Page 142]]
at least 50 percent data capture) the highest reported daily
PM2.5 value for that quarter, excluding state-flagged data
affected by exceptional events which have been approved for exclusion by
the Regional Administrator, looking across those three quarters of all
three years under consideration. If, after substituting the highest
reported daily maximum PM2.5 value for a quarter for all
missing daily data in the matching deficient quarter(s) (i.e., to make
those quarters 100 percent complete), the procedure yields a
recalculated 3-year 24-hour NAAQS test DV (TDVmax) less than
or equal to the level of the standard, then the 24-hour PM2.5
NAAQS DV is deemed to have passed the diagnostic test and is valid, and
the 24-hour PM2.5 NAAQS is deemed to have been met in that 3-
year period.
(d) A 24-hour PM2.5 NAAQS DV based on data that do not
meet the completeness criteria stated in section 4(b) of this appendix
and also do not satisfy the test conditions specified in section 4(c) of
this appendix, may also be considered valid with the approval of, or at
the initiative of, the EPA Administrator, who may consider factors such
as monitoring site closures/moves, monitoring diligence, the consistency
and levels of the daily values that are available, and nearby
concentrations in determining whether to use such data.
(e) The procedures and equations for calculating the 24-hour
PM2.5 NAAQS DVs are given in section 4.5 of this appendix.
4.3 Rounding Conventions. For the purposes of comparing calculated
PM2.5 NAAQS DVs to the applicable level of the standard, it
is necessary to round the final results of the calculations described in
sections 4.4 and 4.5 of this appendix. Results for all intermediate
calculations shall not be rounded.
(a) Annual PM2.5 NAAQS DVs shall be rounded to the
nearest tenth of a [micro]g/m\3\ (decimals x.x5 and greater are rounded
up to the next tenth, and any decimal lower than x.x5 is rounded down to
the nearest tenth).
(b) Twenty-four-hour PM2.5 NAAQS DVs shall be rounded to
the nearest 1 [micro]g/m\3\ (decimals 0.5 and greater are rounded up to
the nearest whole number, and any decimal lower than 0.5 is rounded down
to the nearest whole number).
4.4 Equations for the Annual PM2.5 NAAQS.
(a) An annual mean value for PM2.5 is determined by first
averaging the daily values of a calendar quarter using equation 1 of
this appendix:
[GRAPHIC] [TIFF OMITTED] TR15JA13.005
Where:
Xq,y = the mean for quarter q of the year y;
nq = the number of daily values in the quarter; and
xi q,y = the ith value in quarter q for year y.
(b) Equation 2 of this appendix is then used to calculate the site
annual mean:
[GRAPHIC] [TIFF OMITTED] TR20MR17.000
Where:
Xy = the annual mean concentration for year y (y = 1, 2, or 3);
nQ,y = the number of quarters Q in year y with at least one daily value;
and
Xq,y = the mean for quarter q of year y (result of equation 1).
[[Page 143]]
(c) The annual PM2.5 NAAQS DV is calculated using
equation 3 of this appendix:
[GRAPHIC] [TIFF OMITTED] TR15JA13.007
Where:
X = the annual PM2.5 NAAQS DV; and
Xy = the annual mean for year y (result of equation 2)
(d) The annual PM2.5 NAAQS DV is rounded according to the
conventions in section 4.3 of this appendix before comparisons with the
levels of the primary and secondary annual PM2.5 NAAQS are
made.
4.5 Procedures and Equations for the 24-Hour PM2.5 NAAQS
(a) When the data for a particular site and year meet the data
completeness requirements in section 4.2 of this appendix, calculation
of the 98th percentile is accomplished by the steps provided in this
subsection. Table 1 of this appendix shall be used to identify annual
98th percentile values.
Identification of annual 98th percentile values using the Table 1
procedure will be based on the creditable number of samples (as
described below), rather than on the actual number of samples. Credit
will not be granted for extra (non-creditable) samples. Extra samples,
however, are candidates for selection as the annual 98th percentile.
[The creditable number of samples will determine how deep to go into the
data distribution, but all samples (creditable and extra) will be
considered when making the percentile assignment.] The annual creditable
number of samples is the sum of the four quarterly creditable number of
samples.
Procedure: Sort all the daily values from a particular site and year
by descending value. (For example: (x[1], x[2], x[3], * * *, x[n]). In
this case, x[1] is the largest number and x[n] is the smallest value.)
The 98th percentile value is determined from this sorted series of daily
values which is ordered from the highest to the lowest number. Using the
left column of Table 1, determine the appropriate range for the annual
creditable number of samples for year y (cny) (e.g., for 120
creditable samples per year, the appropriate range would be 101 to 150).
The corresponding ``n'' value in the right column identifies the rank of
the annual 98th percentile value in the descending sorted list of site
specific daily values for year y (e.g., for the range of 101 to 150, n
would be 3). Thus, P0.98, y = the nth largest
value (e.g., for the range of 101 to 150, the 98th percentile value
would be the third highest value in the sorted series of daily values.
Table 1
------------------------------------------------------------------------
The 98th percentile for year
y (P0.98,y), is the nth
Annual number of creditable samples for maximum 24-hour average
year y (cny) value for the year where n
is the listed number
------------------------------------------------------------------------
1 to 50................................... 1
51 to 100................................. 2
101 to 150................................ 3
151 to 200................................ 4
201 to 250................................ 5
251 to 300................................ 6
301 to 350................................ 7
351 to 366................................ 8
------------------------------------------------------------------------
(b) The 24-hour PM2.5 NAAQS DV is then calculated by
averaging the annual 98th percentiles using equation 4 of this appendix:
P0.98,y
[GRAPHIC] [TIFF OMITTED] TR15JA13.008
[[Page 144]]
Where:
P0.98 = the 24-hour PM2.5 NAAQS DV; and
P0.98, y = the annual 98th percentile for year y
(c) The 24-hour PM2.5 NAAQS DV is rounded according to
the conventions in section 4.3 of this appendix before a comparison with
the level of the primary and secondary 24-hour NAAQS are made.
[78 FR 3277, Jan. 15, 2013, as amended at 82 FR 14327, Mar. 20, 2017]
Sec. Appendix O to Part 50--Reference Method for the Determination of
Coarse Particulate Matter as PM10-2.5 in the Atmosphere
1.0 Applicability and Definition
1.1 This method provides for the measurement of the mass
concentration of coarse particulate matter (PM10-2.5) in
ambient air over a 24-hour period. In conjunction with additional
analysis, this method may be used to develop speciated data.
1.2 For the purpose of this method, PM10-2.5 is defined
as particulate matter having an aerodynamic diameter in the nominal
range of 2.5 to 10 micrometers, inclusive.
1.3 For this reference method, PM10-2.5 concentrations
shall be measured as the arithmetic difference between separate but
concurrent, collocated measurements of PM10 and
PM2.5, where the PM10 measurements are obtained
with a specially approved sampler, identified as a ``PM10c
sampler,'' that meets more demanding performance requirements than
conventional PM10 samplers described in appendix J of this
part. Measurements obtained with a PM10c sampler are
identified as ``PM10c measurements'' to distinguish them from
conventional PM10 measurements obtained with conventional
PM10 samplers. Thus, PM10-2.5 = PM10c -
PM2.5.
1.4 The PM10c and PM2.5 gravimetric
measurement processes are considered to be nondestructive, and the
PM10c and PM2.5 samples obtained in the
PM10-2.5 measurement process can be subjected to subsequent
physical or chemical analyses.
1.5 Quality assessment procedures are provided in part 58, appendix
A of this chapter. The quality assurance procedures and guidance
provided in reference 1 in section 13 of this appendix, although written
specifically for PM2.5, are generally applicable for
PM10c, and, hence, PM10-2.5 measurements under
this method, as well.
1.6 A method based on specific model PM10c and
PM2.5 samplers will be considered a reference method for
purposes of part 58 of this chapter only if:
(a) The PM10c and PM2.5 samplers and the
associated operational procedures meet the requirements specified in
this appendix and all applicable requirements in part 53 of this
chapter, and
(b) The method based on the specific samplers and associated
operational procedures have been designated as a reference method in
accordance with part 53 of this chapter.
1.7 PM10-2.5 methods based on samplers that meet nearly
all specifications set forth in this method but have one or more
significant but minor deviations or modifications from those
specifications may be designated as ``Class I'' equivalent methods for
PM10-2.5 in accordance with part 53 of this chapter.
1.8 PM2.5 measurements obtained incidental to the
PM10-2.5 measurements by this method shall be considered to
have been obtained with a reference method for PM2.5 in
accordance with appendix L of this part.
1.9 PM10c measurements obtained incidental to the
PM10-2.5 measurements by this method shall be considered to
have been obtained with a reference method for PM10 in
accordance with appendix J of this part, provided that:
(a) The PM10c measurements are adjusted to EPA reference
conditions (25 [deg]C and 760 millimeters of mercury), and
(b) Such PM10c measurements are appropriately identified
to differentiate them from PM10 measurements obtained with
other (conventional) methods for PM10 designated in
accordance with part 53 of this chapter as reference or equivalent
methods for PM10.
2.0 Principle
2.1 Separate, collocated, electrically powered air samplers for
PM10c and PM2.5 concurrently draw ambient air at
identical, constant volumetric flow rates into specially shaped inlets
and through one or more inertial particle size separators where the
suspended particulate matter in the PM10 or PM2.5
size range, as applicable, is separated for collection on a
polytetrafluoroethylene (PTFE) filter over the specified sampling
period. The air samplers and other aspects of this PM10-2.5
reference method are specified either explicitly in this appendix or by
reference to other applicable regulations or quality assurance guidance.
2.2 Each PM10c and PM2.5 sample collection
filter is weighed (after moisture and temperature conditioning) before
and after sample collection to determine the net weight (mass) gain due
to collected PM10c or PM2.5. The total volume of
air sampled by each sampler is determined by the sampler from the
measured flow rate at local ambient temperature and pressure and the
sampling time. The mass concentrations of both PM10c and
PM2.5 in the ambient air are computed as the total mass of
collected particles in the PM10 or PM2.5 size
range, as appropriate, divided by the total volume of air sampled by the
respective samplers, and expressed in micrograms per cubic meter
([micro]g/
[[Page 145]]
m\3\)at local temperature and pressure conditions. The mass
concentration of PM10-2.5 is determined as the
PM10c concentration value less the corresponding,
concurrently measured PM2.5 concentration value.
2.3 Most requirements for PM10-2.5 reference methods are
similar or identical to the requirements for PM2.5 reference
methods as set forth in appendix L to this part. To insure uniformity,
applicable appendix L requirements are incorporated herein by reference
in the sections where indicated rather than repeated in this appendix.
3.0 PM10 2.5 Measurement Range
3.1 Lower concentration limit. The lower detection limit of the mass
concentration measurement range is estimated to be approximately 3
[micro]g/m\3\, based on the observed precision of PM2.5
measurements in the national PM2.5 monitoring network, the
probable similar level of precision for the matched PM10c
measurements, and the additional variability arising from the
differential nature of the measurement process. This value is provided
merely as a guide to the significance of low PM10-2.5
concentration measurements.
3.2 Upper concentration limit. The upper limit of the mass
concentration range is determined principally by the PM10c
filter mass loading beyond which the sampler can no longer maintain the
operating flow rate within specified limits due to increased pressure
drop across the loaded filter. This upper limit cannot be specified
precisely because it is a complex function of the ambient particle size
distribution and type, humidity, the individual filter used, the
capacity of the sampler flow rate control system, and perhaps other
factors. All PM10c samplers are estimated to be capable of
measuring 24-hour mass concentrations of at least 200 [micro]g/m\3\
while maintaining the operating flow rate within the specified limits.
The upper limit for the PM10-2.5 measurement is likely to be
somewhat lower because the PM10-2.5 concentration represents
only a fraction of the PM10 concentration.
3.3 Sample period. The required sample period for
PM10-2.5 concentration measurements by this method shall be
at least 1,380 minutes but not more than 1,500 minutes (23 to 25 hours),
and the start times of the PM2.5 and PM10c samples
are within 10 minutes and the stop times of the samples are also within
10 minutes (see section 10.4 of this appendix).
4.0 Accuracy (bias)
4.1 Because the size, density, and volatility of the particles
making up ambient particulate matter vary over wide ranges and the mass
concentration of particles varies with particle size, it is difficult to
define the accuracy of PM10-2.5 measurements in an absolute
sense. Furthermore, generation of credible PM10-2.5
concentration standards at field monitoring sites and presenting or
introducing such standards reliably to samplers or monitors to assess
accuracy is still generally impractical. The accuracy of
PM10-2.5 measurements is therefore defined in a relative
sense as bias, referenced to measurements provided by other reference
method samplers or based on flow rate verification audits or checks, or
on other performance evaluation procedures.
4.2 Measurement system bias for monitoring data is assessed
according to the procedures and schedule set forth in part 58, appendix
A of this chapter. The goal for the measurement uncertainty (as bias)
for monitoring data is defined in part 58, appendix A of this chapter as
an upper 95 percent confidence limit for the absolute bias of 15
percent. Reference 1 in section 13 of this appendix provides additional
information and guidance on flow rate accuracy audits and assessment of
bias.
5.0 Precision
5.1 Tests to establish initial measurement precision for each
sampler of the reference method sampler pair are specified as a part of
the requirements for designation as a reference method under part 53 of
this chapter.
5.2 Measurement system precision is assessed according to the
procedures and schedule set forth in appendix A to part 58 of this
chapter. The goal for acceptable measurement uncertainty, as precision,
of monitoring data is defined in part 58, appendix A of this chapter as
an upper 95 percent confidence limit for the coefficient of variation
(CV) of 15 percent. Reference 1 in section 13 of this appendix provides
additional information and guidance on this requirement.
6.0 Filters for PM10c and PM2.5 Sample
Collection. Sample collection filters for both PM10c and
PM2.5 measurements shall be identical and as specified in
section 6 of appendix L to this part.
7.0 Sampler. The PM10-2.5 sampler shall consist of a
PM10c sampler and a PM2.5 sampler, as follows:
7.1 The PM2.5 sampler shall be as specified in section 7
of appendix L to this part.
7.2 The PM10c sampler shall be of like manufacturer,
design, configuration, and fabrication to that of the PM2.5
sampler and as specified in section 7 of appendix L to this part, except
as follows:
7.2.1 The particle size separator specified in section 7.3.4 of
appendix L to this part shall be eliminated and replaced by a downtube
extension fabricated as specified in Figure O-1 of this appendix.
7.2.2 The sampler shall be identified as a PM10c sampler
on its identification label required under Sec. 53.9(d) of this
chapter.
7.2.3 The average temperature and average barometric pressure
measured by the
[[Page 146]]
sampler during the sample period, as described in Table L-1 of appendix
L to this part, need not be reported to EPA's AQS data base, as required
by section 7.4.19 and Table L-1 of appendix L to this part, provided
such measurements for the sample period determined by the associated
PM2.5 sampler are reported as required.
7.3 In addition to the operation/instruction manual required by
section 7.4.18 of appendix L to this part for each sampler, supplemental
operational instructions shall be provided for the simultaneous
operation of the samplers as a pair to collect concurrent
PM10c and PM2.5 samples. The supplemental
instructions shall cover any special procedures or guidance for
installation and setup of the samplers for PM10-2.5
measurements, such as synchronization of the samplers' clocks or timers,
proper programming for collection of concurrent samples, and any other
pertinent issues related to the simultaneous, coordinated operation of
the two samplers.
7.4 Capability for electrical interconnection of the samplers to
simplify sample period programming and further ensure simultaneous
operation is encouraged but not required. Any such capability for
interconnection shall not supplant each sampler's capability to operate
independently, as required by section 7 of appendix L of this part.
8.0 Filter Weighing
8.1 Conditioning and weighing for both PM10c and
PM2.5 sample filters shall be as specified in section 8 of
appendix L to this part. See reference 1 of section 13 of this appendix
for additional, more detailed guidance.
8.2 Handling, conditioning, and weighing for both PM10c
and PM2.5 sample filters shall be matched such that the
corresponding PM10c and PM2.5 filters of each
filter pair receive uniform treatment. The PM10c and
PM2.5 sample filters should be weighed on the same balance,
preferably in the same weighing session and by the same analyst.
8.3 Due care shall be exercised to accurately maintain the paired
relationship of each set of concurrently collected PM10c and
PM2.5 sample filters and their net weight gain data and to
avoid misidentification or reversal of the filter samples or weight
data. See Reference 1 of section 13 of this appendix for additional
guidance.
9.0 Calibration. Calibration of the flow rate, temperature
measurement, and pressure measurement systems for both the
PM10c and PM2.5 samplers shall be as specified in
section 9 of appendix L to this part.
10.0 PM10 2.5 Measurement Procedure
10.1 The PM10c and PM2.5 samplers shall be
installed at the monitoring site such that their ambient air inlets
differ in vertical height by not more than 0.2 meter, if possible, but
in any case not more than 1 meter, and the vertical axes of their inlets
are separated by at least 1 meter but not more than 4 meters,
horizontally.
10.2 The measurement procedure for PM10c shall be as
specified in section 10 of appendix L to this part, with
``PM10c'' substituted for ``PM2.5'' wherever it
occurs in that section.
10.3 The measurement procedure for PM2.5 shall be as
specified in section 10 of appendix L to this part.
10.4 For the PM10-2.5 measurement, the PM10c
and PM2.5 samplers shall be programmed to operate on the same
schedule and such that the sample period start times are within 5
minutes and the sample duration times are within 5 minutes.
10.5 Retrieval, transport, and storage of each PM10c and
PM2.5 sample pair following sample collection shall be
matched to the extent practical such that both samples experience
uniform conditions.
11.0 Sampler Maintenance. Both PM10c and PM2.5
samplers shall be maintained as described in section 11 of appendix L to
this part.
12.0 Calculations
12.1 Both concurrent PM10c and PM2.5
measurements must be available, valid, and meet the conditions of
section 10.4 of this appendix to determine the PM10-2.5 mass
concentration.
12.2 The PM10c mass concentration is calculated using
equation 1 of this section:
[GRAPHIC] [TIFF OMITTED] TR17OC06.012
Where:
PM10c = mass concentration of PM10c, [micro]g/
m\3\;
Wf, Wi = final and initial masses (weights),
respectively, of the filter used to collect the
PM10c particle sample, [micro]g;
Va = total air volume sampled by the PM10c sampler
in actual volume units measured at local conditions of
temperature and pressure, as provided by the sampler, m\3\.
Note: Total sample time must be between 1,380 and 1,500 minutes (23
and 25 hrs) for a fully valid PM10c sample; however, see also
section 3.3 of this appendix.
12.3 The PM2.5 mass concentration is calculated as
specified in section 12 of appendix L to this part.
12.4 The PM10-2.5 mass concentration, in [micro]g/m\3\,
is calculated using Equation 2 of this section:
[[Page 147]]
[GRAPHIC] [TIFF OMITTED] TR17OC06.013
13.0 Reference
1. Quality Assurance Guidance Document 2.12. Monitoring
PM2.5 in Ambient Air Using Designated Reference or Class I
Equivalent Methods. Draft, November 1998 (or later version or
supplement, if available). Available at: www.epa.gov/ttn/amtic/
pgqa.html.
14.0 Figures
Figure O-1 is included as part of this appendix O.
[[Page 148]]
[GRAPHIC] [TIFF OMITTED] TR17OC06.014
[[Page 149]]
[71 FR 61230, Oct. 17, 2006]
Sec. Appendix P to Part 50--Interpretation of the Primary and Secondary
National Ambient Air Quality Standards for Ozone
1. General
(a) This appendix explains the data handling conventions and
computations necessary for determining whether the national 8-hour
primary and secondary ambient air quality standards for ozone
(O3) specified in Sec. 50.15 are met at an ambient
O3 air quality monitoring site. Ozone is measured in the
ambient air by a reference method based on appendix D of this part, as
applicable, and designated in accordance with part 53 of this chapter,
or by an equivalent method designated in accordance with part 53 of this
chapter. Data reporting, data handling, and computation procedures to be
used in making comparisons between reported O3 concentrations
and the levels of the O3 standards are specified in the
following sections. Whether to exclude, retain, or make adjustments to
the data affected by exceptional events, including stratospheric
O3 intrusion and other natural events, is determined by the
requirements under Sec. Sec. 50.1, 50.14 and 51.930.
(b) The terms used in this appendix are defined as follows:
8-hour average is the rolling average of eight hourly O3
concentrations as explained in section 2 of this appendix.
Annual fourth-highest daily maximum refers to the fourth highest
value measured at a monitoring site during a particular year.
Daily maximum 8-hour average concentration refers to the maximum
calculated 8-hour average for a particular day as explained in section 2
of this appendix.
Design values are the metrics (i.e., statistics) that are compared
to the NAAQS levels to determine compliance, calculated as shown in
section 3 of this appendix.
O3 monitoring season refers to the span of time within a
calendar year when individual States are required to measure ambient
O3 concentrations as listed in part 58 appendix D to this
chapter.
Year refers to calendar year.
2. Primary and Secondary Ambient Air Quality Standards for Ozone
2.1 Data Reporting and Handling Conventions
Computing 8-hour averages. Hourly average concentrations shall be
reported in parts per million (ppm) to the third decimal place, with
additional digits to the right of the third decimal place truncated.
Running 8-hour averages shall be computed from the hourly O3
concentration data for each hour of the year and shall be stored in the
first, or start, hour of the 8-hour period. An 8-hour average shall be
considered valid if at least 75% of the hourly averages for the 8-hour
period are available. In the event that only 6 or 7 hourly averages are
available, the 8-hour average shall be computed on the basis of the
hours available using 6 or 7 as the divisor. 8-hour periods with three
or more missing hours shall be considered valid also, if, after
substituting one-half the minimum detectable limit for the missing
hourly concentrations, the 8-hour average concentration is greater than
the level of the standard. The computed 8-hour average O3
concentrations shall be reported to three decimal places (the digits to
the right of the third decimal place are truncated, consistent with the
data handling procedures for the reported data).
Daily maximum 8-hour average concentrations. (a) There are 24
possible running 8-hour average O3 concentrations for each
calendar day during the O3 monitoring season. The daily
maximum 8-hour concentration for a given calendar day is the highest of
the 24 possible 8-hour average concentrations computed for that day.
This process is repeated, yielding a daily maximum 8-hour average
O3 concentration for each calendar day with ambient
O3 monitoring data. Because the 8-hour averages are recorded
in the start hour, the daily maximum 8-hour concentrations from two
consecutive days may have some hourly concentrations in common.
Generally, overlapping daily maximum 8-hour averages are not likely,
except in those non-urban monitoring locations with less pronounced
diurnal variation in hourly concentrations.
(b) An O3 monitoring day shall be counted as a valid day
if valid 8-hour averages are available for at least 75% of possible
hours in the day (i.e., at least 18 of the 24 averages). In the event
that less than 75% of the 8-hour averages are available, a day shall
also be counted as a valid day if the daily maximum 8-hour average
concentration for that day is greater than the level of the standard.
2.2 Primary and Secondary Standard-related Summary Statistic
The standard-related summary statistic is the annual fourth-highest
daily maximum 8-hour O3 concentration, expressed in parts per
million, averaged over three years. The 3-year average shall be computed
using the three most recent, consecutive calendar years of monitoring
data meeting the data completeness requirements described in this
appendix. The computed 3-year average of the annual fourth-highest daily
maximum 8-hour average O3 concentrations shall be reported to
three decimal places (the digits to the right of the third decimal place
are truncated, consistent with the data handling procedures for the
reported data).
[[Page 150]]
2.3 Comparisons with the Primary and Secondary Ozone Standards
(a) The primary and secondary O3 ambient air quality
standards are met at an ambient air quality monitoring site when the 3-
year average of the annual fourth-highest daily maximum 8-hour average
O3 concentration is less than or equal to 0.075 ppm.
(b) This comparison shall be based on three consecutive, complete
calendar years of air quality monitoring data. This requirement is met
for the 3-year period at a monitoring site if daily maximum 8-hour
average concentrations are available for at least 90% of the days within
the O3 monitoring season, on average, for the 3-year period,
with a minimum data completeness requirement in any one year of at least
75% of the days within the O3 monitoring season. When
computing whether the minimum data completeness requirements have been
met, meteorological or ambient data may be sufficient to demonstrate
that meteorological conditions on missing days were not conducive to
concentrations above the level of the standard. Missing days assumed
less then the level of the standard are counted for the purpose of
meeting the data completeness requirement, subject to the approval of
the appropriate Regional Administrator.
(c) Years with concentrations greater than the level of the standard
shall be included even if they have less than complete data. Thus, in
computing the 3-year average fourth maximum concentration, calendar
years with less than 75% data completeness shall be included in the
computation if the 3-year average fourth-highest 8-hour concentration is
greater than the level of the standard.
(d) Comparisons with the primary and secondary O3
standards are demonstrated by examples 1 and 2 in paragraphs (d)(1) and
(d)(2) respectively as follows:
Example 1--Ambient Monitoring Site Attaining the Primary and Secondary O3 Standards
--------------------------------------------------------------------------------------------------------------------------------------------------------
Percent valid
days (within 1st Highest 2nd Highest 3rd Highest 4th Highest 5th Highest
Year the required daily max 8- daily max 8- daily max 8- daily max 8- daily max 8-
monitoring hour Conc. hour Conc. hour Conc. hour Conc. hour Conc.
season) (ppm) (ppm) (ppm) (ppm) (ppm)
--------------------------------------------------------------------------------------------------------------------------------------------------------
2004.................................................... 100 0.092 0.090 0.085 0.079 0.078
2005.................................................... 96 0.084 0.083 0.075 0.072 0.070
2006.................................................... 98 0.080 0.079 0.077 0.076 0.060
-----------------------------------------------------------------------------------------------
Average............................................. 98 .............. .............. .............. 0.075 ..............
--------------------------------------------------------------------------------------------------------------------------------------------------------
(1) As shown in Example 1, this monitoring site meets the primary
and secondary O3 standards because the 3-year average of the
annual fourth-highest daily maximum 8-hour average O3
concentrations (i.e., 0.075666 * * * ppm, truncated to 0.075 ppm) is
less than or equal to 0.075 ppm. The data completeness requirement is
also met because the average percent of days within the required
monitoring season with valid ambient monitoring data is greater than
90%, and no single year has less than 75% data completeness. In Example
1, the individual 8-hour averages used to determine the annual fourth
maximum have also been truncated to the third decimal place.
Example 2--Ambient Monitoring Site Failing to Meet the Primary and Secondary O3 Standards
--------------------------------------------------------------------------------------------------------------------------------------------------------
Percent valid
days (within 1st Highest 2nd Highest 3rd Highest 4th Highest 5th Highest
Year the required daily max 8- daily max 8- daily max 8- daily max 8- daily max 8-
monitoring hour Conc. hour Conc. hour Conc. hour Conc. hour Conc.
season) (ppm) (ppm) (ppm) (ppm) (ppm)
--------------------------------------------------------------------------------------------------------------------------------------------------------
2004.................................................... 96 0.105 0.103 0.103 0.103 0.102
2005.................................................... 74 0.104 0.103 0.092 0.091 0.088
2006.................................................... 98 0.103 0.101 0.101 0.095 0.094
-----------------------------------------------------------------------------------------------
Average............................................. 89 .............. .............. .............. 0.096 ..............
--------------------------------------------------------------------------------------------------------------------------------------------------------
As shown in Example 2, the primary and secondary O3
standards are not met for this monitoring site because the 3-year
average of the fourth-highest daily maximum 8-hour average O3
concentrations (i.e., 0.096333 * * * ppm, truncated to 0.096 ppm) is
greater than 0.075 ppm, even though the data capture is less than 75%
and the average data capture for the 3 years is less than 90% within the
required monitoring season. In Example 2, the individual 8-hour averages
used to determine
[[Page 151]]
the annual fourth maximum have also been truncated to the third decimal
place.
3. Design Values for Primary and Secondary Ambient Air Quality Standards
for Ozone
The air quality design value at a monitoring site is defined as that
concentration that when reduced to the level of the standard ensures
that the site meets the standard. For a concentration-based standard,
the air quality design value is simply the standard-related test
statistic. Thus, for the primary and secondary standards, the 3-year
average annual fourth-highest daily maximum 8-hour average O3
concentration is also the air quality design value for the site.
[73 FR 16511, Mar. 27, 2008]
Sec. Appendix Q to Part 50--Reference Method for the Determination of
Lead in Particulate Matter as PM10 Collected From Ambient Air
This Federal Reference Method (FRM) draws heavily from the specific
analytical protocols used by the U.S. EPA.
1. Applicability and Principle
1.1 This method provides for the measurement of the lead (Pb)
concentration in particulate matter that is 10 micrometers or less
(PM10) in ambient air. PM10 is collected on an
acceptable (see section 6.1.2) 46.2 mm diameter polytetrafluoroethylene
(PTFE) filter for 24 hours using active sampling at local conditions
with a low-volume air sampler. The low-volume sampler has an average
flow rate of 16.7 liters per minute (Lpm) and total sampled volume of 24
cubic meters (m\3\) of air. The analysis of Pb in PM10 is
performed on each individual 24-hour sample. Gravimetric mass analysis
of PM10c filters is not required for Pb analysis. For the
purpose of this method, PM10 is defined as particulate matter
having an aerodynamic diameter in the nominal range of 10 micrometers
(10 [micro]m) or less.
1.2 For this reference method, PM10 shall be collected
with the PM10c federal reference method (FRM) sampler as
described in appendix O to Part 50 using the same sample period,
measurement procedures, and requirements specified in appendix L of Part
50. The PM10c sampler is also being used for measurement of
PM10-2.5 mass by difference and as such, the PM10c
sampler must also meet all of the performance requirements specified for
PM2.5 in appendix L. The concentration of Pb in the
atmosphere is determined in the total volume of air sampled and
expressed in micrograms per cubic meter ([micro]g/m\3\) at local
temperature and pressure conditions.
1.3 The FRM will serve as the basis for approving Federal Equivalent
Methods (FEMs) as specified in 40 CFR Part 53 (Reference and Equivalent
Methods). This FRM specifically applies to the analysis of Pb in
PM10 filters collected with the PM10c sampler. If
these filters are analyzed for elements other than Pb, then refer to the
guidance provided in the EPA Inorganic Compendium Method IO-3.3
(Reference 1 of section 8) for multi-element analysis.
1.4 The PM10c air sampler draws ambient air at a constant
volumetric flow rate into a specially shaped inlet and through an
inertial particle size separator, where the suspended particulate matter
in the PM10 size range is separated for collection on a PTFE
filter over the specified sampling period. The Pb content of the
PM10 sample is analyzed by energy-dispersive X-ray
fluorescence spectrometry (EDXRF). Energy-dispersive X-ray fluorescence
spectrometry provides a means for identification of an element by
measurement of its characteristic X-ray emission energy. The method
allows for quantification of the element by measuring the intensity of
X-rays emitted at the characteristic photon energy and then relating
this intensity to the elemental concentration. The number or intensity
of X-rays produced at a given energy provides a measure of the amount of
the element present by comparisons with calibration standards. The X-
rays are detected and the spectral signals are acquired and processed
with a personal computer. EDXRF is commonly used as a non-destructive
method for quantifying trace elements in PM. A detailed explanation of
quantitative X-ray spectrometry is described in references 2, 3 and 4.
1.5 Quality assurance (QA) procedures for the collection of
monitoring data are contained in Part 58, appendix A.
2. PM10Pb Measurement Range and Detection Limit. The values given
below in section 2.1 and 2.2 are typical of the method capabilities.
Absolute values will vary for individual situations depending on the
instrument, detector age, and operating conditions used. Data are
typically reported in ng/m\3\ for ambient air samples; however, for this
reference method, data will be reported in [micro]g/m\3\ at local
temperature and pressure conditions.
2.1 EDXRF Pb Measurement Range. The typical ambient air measurement
range is 0.001 to 30 [micro]g Pb/m\3\, assuming an upper range
calibration standard of about 60 [micro]g Pb per square centimeter
(cm\2\), a filter deposit area of 11.86 cm\2\, and an air volume of 24
m\3\. The top range of the EDXRF instrument is much greater than what is
stated here. The top measurement range of quantification is defined by
the level of the high concentration calibration standard used and can be
increased to expand the measurement range as needed.
2.2 Detection Limit (DL). A typical estimate of the one-sigma
detection limit (DL) is about 2 ng Pb/cm\2\ or 0.001 [micro]g Pb/m\3\,
assuming a filter size of 46.2 mm (filter deposit
[[Page 152]]
area of 11.86 cm\2\) and a sample air volume of 24 m\3\. The DL is an
estimate of the lowest amount of Pb that can be reliably distinguished
from a blank filter. The one-sigma detection limit for Pb is calculated
as the average overall uncertainty or propagated error for Pb,
determined from measurements on a series of blank filters from the
filter lot(s) in use. Detection limits must be determined for each
filter lot in use. If a new filter lot is used, then a new DL must be
determined. The sources of random error which are considered are
calibration uncertainty; system stability; peak and background counting
statistics; uncertainty in attenuation corrections; and uncertainty in
peak overlap corrections, but the dominating source by far is peak and
background counting statistics. At a minimum, laboratories are to
determine annual estimates of the DL using the guidance provided in
Reference 5.
3. Factors Affecting Bias and Precision of Lead Determination by
EDXRF
3.1 Filter Deposit. X-ray spectra are subject to distortion if
unusually heavy deposits are analyzed. This is the result of internal
absorption of both primary and secondary X-rays within the sample;
however, this is not an issue for Pb due to the energetic X-rays used to
fluoresce Pb and the energetic characteristic X-rays emitted by Pb. The
optimum mass filter loading for multi-elemental EDXRF analyis is about
100 [micro]g/cm\2\ or 1.2 mg/filter for a 46.2-mm filter. Too little
deposit material can also be problematic due to low counting statistics
and signal noise. The particle mass deposit should minimally be 15
[micro]g/cm\2\. The maximum PM10 filter loading or upper
concentration limit of mass expected to be collected by the
PM10c sampler is 200 [micro]g/m\3\ (Appendix O to Part 50,
Section 3.2). This equates to a mass loading of about 400 [micro]g/cm\2\
and is the maximum expected loading for PM10c filters. This
maximum loading is acceptable for the analysis of Pb and other high-Z
elements with very energetic characteristic X-rays. A properly collected
sample will have a uniform deposit over the entire collection area.
Samples with physical deformities (including a visually non-uniform
deposit area) should not be quantitatively analyzed. Tests on the
uniformity of particle deposition on PM10C filters showed
that the non-uniformity of the filter deposit represents a small
fraction of the overall uncertainty in ambient Pb concentration
measurement. The analysis beam of the XRF analyzer does not cover the
entire filter collection area. The minimum allowable beam size is 10 mm.
3.2 Spectral Interferences and Spectral Overlap. Spectral
interference occurs when the entirety of the analyte spectral lines of
two species are nearly 100% overlapped. The presence of arsenic (As) is
a problematic interference for EDXRF systems which use the Pb L[alpha]
line exclusively to quantify the Pb concentration. This is because the
Pb L[alpha] line and the As K[alpha] lines severely overlap. The use of
multiple Pb lines, including the L[beta] and/or the L[gamma] lines for
quantification must be used to reduce the uncertainty in the Pb
determination in the presence of As. There can be instances when lines
partially overlap the Pb spectral lines, but with the energy resolution
of most detectors these overlaps are typically de-convoluted using
standard spectral de-convolution software provided by the instrument
vendor. An EDXRF protocol for Pb must define which Pb lines are used for
quantification and where spectral overlaps occur. A de-convolution
protocol must be used to separate all the lines which overlap with Pb.
3.3 Particle Size Effects and Attenuation Correction Factors. X-ray
attenuation is dependent on the X-ray energy, mass sample loading,
composition, and particle size. In some cases, the excitation and
fluorescent X-rays are attenuated as they pass through the sample. In
order to relate the measured intensity of the X-rays to the thin-film
calibration standards used, the magnitude of any attenuation present
must be corrected for. See references 6, 7, and 8 for more discussion on
this issue. Essentially no attenuation corrections are necessary for Pb
in PM10: Both the incoming excitation X-rays used for
analyzing lead and the fluoresced Pb X-rays are sufficiently energetic
that for particles in this size range and for normal filter loadings,
the Pb X-ray yield is not significantly impacted by attenuation.
4. Precision
4.1 Measurement system precision is assessed according to the
procedures set forth in appendix A to part 58. Measurement method
precision is assessed from collocated sampling and analysis. The goal
for acceptable measurement uncertainty, as precision, is defined as an
upper 90 percent confidence limit for the coefficient of variation (CV)
of 20 percent.
5. Bias
5.1 Measurement system bias for monitoring data is assessed
according to the procedures set forth in appendix A of part 58. The bias
is assessed through an audit using spiked filters. The goal for
measurement bias is defined as an upper 95 percent confidence limit for
the absolute bias of 15 percent.
6. Measurement of PTFE Filters by EDXRF
6.1 Sampling
6.1.1 Low-Volume PM10cSampler. The low-volume PM10c
sampler shall be used for PM10 sample collection and operated
in accordance with the performance specifications described in part 50,
appendix L.
6.1.2 PTFE Filters and Filter Acceptance Testing. The PTFE filters
used for PM10c sample collection shall meet the
specifications provided in part 50, appendix L. The following
requirements are similar to those
[[Page 153]]
currently specified for the acceptance of PM2.5 filters that
are tested for trace elements by EDXRF. For large filter lots (greater
than 500 filters) randomly select 20 filters from a given lot. For small
lots (less than 500 filters) a lesser number of filters may be taken.
Analyze each blank filter separately and calculate the average lead
concentration in ng/cm\2\. Ninety percent, or 18 of the 20 filters, must
have an average lead concentration that is less than 4.8 ng Pb/cm\2\.
6.1.2.1 Filter Blanks. Field blank filters shall be collected along
with routine samples. Field blank filters will be collected that are
transported to the sampling site and placed in the sampler for the
duration of sampling without sampling. Laboratory blank filters from
each filter lot used shall be analyzed with each batch of routine sample
filters analyzed. Laboratory blank filters are used in background
subtraction as discussed below in Section 6.2.4.
6.2 Analysis. The four main categories of random and systematic
error encountered in X-ray fluorescence analysis include errors from
sample collection, the X-ray source, the counting process, and inter-
element effects. These errors are addressed through the calibration
process and mathematical corrections in the instrument software.
Spectral processing methods are well established and most commercial
analyzers have software that can implement the most common approaches
(references 9-11) to background subtraction, peak overlap correction,
counting and deadtime corrections.
6.2.1 EDXRF Analysis Instrument. An energy-dispersive XRF system is
used. Energy-dispersive XRF systems are available from a number of
commercial vendors. Examples include Thermo (www.thermo.com), Spectro
(http://www.spectro.com), Xenemetrix (http://www.xenemetrix.com) and
PANalytical (http://www.panalytical.com). \1\ The analysis is performed
at room temperature in either vacuum or in a helium atmosphere. The
specific details of the corrections and calibration algorithms are
typically included in commercial analytical instrument software routines
for automated spectral acquisition and processing and vary by
manufacturer. It is important for the analyst to understand the
correction procedures and algorithms of the particular system used, to
ensure that the necessary corrections are applied.
---------------------------------------------------------------------------
\1\ These are examples of available systems and is not an all
inclusive list. The mention of commercial products does not imply
endorsement by the U.S. Environmental Protection Agency.
---------------------------------------------------------------------------
6.2.2 Thin film standards. Thin film standards are used for
calibration because they most closely resemble the layer of particles on
a filter. Thin films standards are typically deposited on Nuclepore
substrates. The preparation of thin film standards is discussed in
reference 8, and 10. The NIST SRM 2783 (Air Particulate on Filter Media)
is currently available on polycarbonate filters and contains a certified
concentration for Pb. Thin film standards at 15 and 50 [micro]g/cm\2\
are commercially available from MicroMatter Inc. (Arlington, WA).
6.2.3 Filter Preparation. Filters used for sample collection are
46.2-mm PTFE filters with a pore size of 2 microns and filter deposit
area 11.86 cm\2\. Cold storage is not a requirement for filters analyzed
for Pb; however, if filters scheduled for XRF analysis were stored cold,
they must be allowed to reach room temperature prior to analysis. All
filter samples received for analysis are checked for any holes, tears,
or a non-uniform deposit which would prevent quantitative analysis.
Samples with physical deformities are not quantitatively analyzable. The
filters are carefully removed with tweezers from the Petri dish and
securely placed into the instrument-specific sampler holder for
analysis. Care must be taken to protect filters from contamination prior
to analysis. Filters must be kept covered when not being analyzed. No
other preparation of filter samples is required.
6.2.4 Calibration. In general, calibration determines each element's
sensitivity, i.e., its response in x-ray counts/sec to each [micro]g/
cm\2\ of a standard and an interference coefficient for each element
that causes interference with another one (See section 3.2 above). The
sensitivity can be determined by a linear plot of count rate versus
concentration ([micro]g/cm\2\) in which the slope is the instrument's
sensitivity for that element. A more precise way, which requires fewer
standards, is to fit sensitivity versus atomic number. Calibration is a
complex task in the operation of an XRF system. Two major functions
accomplished by calibration are the production of reference spectra
which are used for fitting and the determination of the elemental
sensitivities. Included in the reference spectra (referred to as
``shapes'') are background-subtracted peak shapes of the elements to be
analyzed (as well as interfering elements) and spectral backgrounds.
Pure element thin film standards are used for the element peak shapes
and clean filter blanks from the same lot as routine filter samples are
used for the background. The analysis of Pb in PM filter deposits is
based on the assumption that the thickness of the deposit is small with
respect to the characteristic Pb X-ray transmission thickness.
Therefore, the concentration of Pb in a sample is determined by first
calibrating the spectrometer with thin film standards to determine the
sensitivity factor for Pb and then analyzing the unknown samples under
identical excitation conditions as used to determine the calibration.
Calibration shall be
[[Page 154]]
performed annually or when significant repairs or changes occur (e.g., a
change in fluorescers, X-ray tubes, or detector). Calibration
establishes the elemental sensitivity factors and the magnitude of
interference or overlap coefficients. See reference 7 for more detailed
discussion of calibration and analysis of shapes standards for
background correction, coarse particle absorption corrections, and
spectral overlap.
6.2.4.1 Spectral Peak Fitting. The EPA uses a library of pure
element peak shapes (shape standards) to extract the elemental
background-free peak areas from an unknown spectrum. It is also possible
to fit spectra using peak stripping or analytically defined functions
such as modified Gaussian functions. The EPA shape standards are
generated from pure, mono-elemental thin film standards. The shape
standards are acquired for sufficiently long times to provide a large
number of counts in the peaks of interest. It is not necessary for the
concentration of the standard to be known. A slight contaminant in the
region of interest in a shape standard can have a significant and
serious effect on the ability of the least squares fitting algorithm to
fit the shapes to the unknown spectrum. It is these elemental peak
shapes that are fitted to the peaks in an unknown sample during spectral
processing by the analyzer. In addition to this library of elemental
shapes there is also a background shape spectrum for the filter type
used as discussed below in section 6.2.4.2 of this section.
6.2.4.2 Background Measurement and Correction. A background spectrum
generated by the filter itself must be subtracted from the X-ray
spectrum prior to extracting peak areas. Background spectra must be
obtained for each filter lot used for sample collection. The background
shape standards which are used for background fitting are created at the
time of calibration. If a new lot of filters is used, new background
spectra must be obtained. A minimum of 20 clean blank filters from each
filter lot are kept in a sealed container and are used exclusively for
background measurement and correction. The spectra acquired on
individual blank filters are added together to produce a single spectrum
for each of the secondary targets or fluorescers used in the analysis of
lead. Individual blank filter spectra which show atypical contamination
are excluded from the summed spectra. The summed spectra are fitted to
the appropriate background during spectral processing. Background
correction is automatically included during spectral processing of each
sample.
7. Calculation.
7.1 PM10 Pb concentrations. The PM10 Pb concentration in
the atmosphere ([micro]g/m\3\) is calculated using the following
equation:
[GRAPHIC] [TIFF OMITTED] TR12NO08.000
Where,
MPb is the mass per unit volume for lead in [micro]g/m\3\;
CPb is the mass per unit area for lead in [micro]g/cm\2\ as measured by
XRF;
A is the filter deposit area in cm\2\;
VLC is the total volume of air sampled by the PM10c sampler
in actual volume units measured at local conditions of
temperature and pressure, as provided by the sampler in m\3\.
7.2 PM10 Pb Uncertainty Calculations.
The principal contributors to total uncertainty of XRF values
include: field sampling; filter deposit area; XRF calibration;
attenuation or loss of the x-ray signals due to the other components of
the particulate sample; and determination of the Pb X-ray emission peak
area by curve fitting. See reference 12 for a detailed discussion of how
uncertainties are similarly calculated for the PM2.5 Chemical
Speciation program.
The model for calculating total uncertainty is:
[delta]tot = ([delta]f2 + [delta]a2 + [delta]c2 + [delta]v2) 1/2
Where,
[delta]f = fitting uncertainty (XRF-specific, from 2 to 100 +
%)
[delta]a = attenuation uncertainty (XRF-specific,
insignificant for Pb)
[delta]c = calibration uncertainty (combined lab uncertainty,
assumed as 5%)
[delta]v = volume/deposition size uncertainty (combined field
uncertainty, assumed as 5%)
8. References
1. Inorganic Compendium Method IO-3.3; Determination of Metals in
Ambient Particulate Matter Using X-Ray Fluorescence (XRF) Spectroscopy;
U.S. Environmental Protection Agency, Cincinnati, OH 45268. EPA/625/R-
96/010a. June 1999.
2. Jenkins, R., Gould, R.W., and Gedcke, D. Quantitative X-ray
Spectrometry: Second Edition. Marcel Dekker, Inc., New York, NY. 1995.
3. Jenkins, R. X-Ray Fluorescence Spectrometry: Second Edition in
Chemical Analysis, a Series of Monographs on Analytical Chemistry and
Its Applications, Volume 152. Editor J.D.Winefordner; John Wiley & Sons,
Inc., New York, NY. 1999.
4. Dzubay, T.G. X-ray Fluorescence Analysis of Environmental
Samples, Ann Arbor Science Publishers Inc., 1977.
5. Code of Federal Regulations (CFR) 40, Part 136, Appendix B;
Definition and Procedure for the Determination of the Method Detection
Limit--Revision 1.1.
6. Drane, E.A, Rickel, D.G., and Courtney, W.J., ``Computer Code for
Analysis X-Ray
[[Page 155]]
Fluorescence Spectra of Airborne Particulate Matter,'' in Advances in X-
Ray Analysis, J.R. Rhodes, Ed., Plenum Publishing Corporation, New York,
NY, p. 23 (1980).
7. Analysis of Energy-Dispersive X-ray Spectra of Ambient Aerosols
with Shapes Optimization, Guidance Document; TR-WDE-06-02; prepared
under contract EP-D-05-065 for the U.S. Environmental Protection Agency,
National Exposure Research Laboratory. March 2006.
8. Billiet, J., Dams, R., and Hoste, J. (1980) Multielement Thin
Film Standards for XRF Analysis, X-Ray Spectrometry, 9(4): 206-211.
9. Bonner, N.A.; Bazan, F.; and Camp, D.C. (1973). Elemental
analysis of air filter samples using x-ray fluorescence. Report No.
UCRL-51388. Prepared for U.S. Atomic Energy Commission, by Univ. of
Calif., Lawrence Livermore Laboratory, Livermore, CA.
10. Dzubay, T.G.; Lamothe, P.J.; and Yoshuda, H. (1977). Polymer
films as calibration standards for X-ray fluorescence analysis. Adv. X-
Ray Anal., 20:411.
11. Giauque, R.D.; Garrett, R.B.; and Goda, L.Y. (1977). Calibration
of energy-dispersive X-ray spectrometers for analysis of thin
environmental samples. In X-Ray Fluorescence Analysis of Environmental
Samples, T.G. Dzubay, Ed., Ann Arbor Science Publishers, Ann Arbor, MI,
pp. 153-181.
12. Harmonization of Interlaboratory X-ray Fluorescence Measurement
Uncertainties, Detailed Discussion Paper; August 4, 2006; prepared for
the Office of Air Quality Planning and Standards under EPA contract 68-
D-03-038. http://www.epa.gov/ttn/amtic/files/ambient/pm25/spec/
xrfdet.pdf.
[73 FR 67052, Nov. 12, 2008]
Sec. Appendix R to Part 50--Interpretation of the National Ambient Air
Quality Standards for Lead
1. General.
(a) This appendix explains the data handling conventions and
computations necessary for determining when the primary and secondary
national ambient air quality standards (NAAQS) for lead (Pb) specified
in Sec. 50.16 are met. The NAAQS indicator for Pb is defined as: lead
and its compounds, measured as elemental lead in total suspended
particulate (Pb-TSP), sampled and analyzed by a Federal reference method
(FRM) based on appendix G to this part or by a Federal equivalent method
(FEM) designated in accordance with part 53 of this chapter. Although
Pb-TSP is the lead NAAQS indicator, surrogate Pb-TSP concentrations
shall also be used for NAAQS comparisons; specifically, valid surrogate
Pb-TSP data are concentration data for lead and its compounds, measured
as elemental lead, in particles with an aerodynamic size of 10 microns
or less (Pb-PM10), sampled and analyzed by an FRM based on
appendix Q to this part or by an FEM designated in accordance with part
53 of this chapter. Surrogate Pb-TSP data (i.e., Pb-PM10
data), however, can only be used to show that the Pb NAAQS were violated
(i.e., not met); they can not be used to demonstrate that the Pb NAAQS
were met. Pb-PM10 data used as surrogate Pb-TSP data shall be
processed at face value; that is, without any transformation or scaling.
Data handling and computation procedures to be used in making
comparisons between reported and/or surrogate Pb-TSP concentrations and
the level of the Pb NAAQS are specified in the following sections.
(b) Whether to exclude, retain, or make adjustments to the data
affected by exceptional events, including natural events, is determined
by the requirements and process deadlines specified in Sec. Sec. 50.1,
50.14, and 51.930 of this chapter.
(c) The terms used in this appendix are defined as follows:
Annual monitoring network plan refers to the plan required by
section 58.10 of this chapter.
Creditable samples are samples that are given credit for data
completeness. They include valid samples collected on required sampling
days and valid ``make-up'' samples taken for missed or invalidated
samples on required sampling days.
Daily values for Pb refer to the 24-hour mean concentrations of Pb
(Pb-TSP or Pb-PM10), measured from midnight to midnight
(local standard time), that are used in NAAQS computations.
Design value is the site-level metric (i.e., statistic) that is
compared to the NAAQS level to determine compliance; the design value
for the Pb NAAQS is selected according to the procedures in this
appendix from among the valid three-month Pb-TSP and surrogate Pb-TSP
(Pb-PM10) arithmetic mean concentration for the 38-month
period consisting of the most recent 3-year calendar period plus two
previous months (i.e., 36 3-month periods) using the last month of each
3-month period as the period of report.
Extra samples are non-creditable samples. They are daily values that
do not occur on scheduled sampling days and that can not be used as
``make-up samples'' for missed or invalidated scheduled samples. Extra
samples are used in mean calculations. For purposes of determining
whether a sample must be treated as a make-up sample or an extra sample,
Pb-TSP and Pb-PM10 data collected before January 1, 2009 will
be treated with an assumed scheduled sampling frequency of every sixth
day.
Make-up samples are samples taken to replace missed or invalidated
required scheduled samples. Make-ups can be made by either the primary
or collocated (same size fraction) instruments; to be considered a
[[Page 156]]
valid make-up, the sampling must be conducted with equipment and
procedures that meet the requirements for scheduled sampling. Make-up
samples are either taken before the next required sampling day or
exactly one week after the missed (or voided) sampling day. Make-up
samples can not span years; that is, if a scheduled sample for December
is missed (or voided), it can not be made up in January. Make-up
samples, however, may span months, for example a missed sample on
January 31 may be made up on February 1, 2, 3, 4, 5, or 7 (with an
assumed sampling frequency of every sixth day). Section 3(e) explains
how such month-spanning make-up samples are to be treated for purposes
of data completeness and mean calculations. Only two make-up samples are
permitted each calendar month; these are counted according to the month
in which the miss and not the makeup occurred. For purposes of
determining whether a sample must be treated as a make-up sample or an
extra sample, Pb-TSP and Pb-PM10 data collected before
January 1, 2009 will be treated with an assumed scheduled sampling
frequency of every sixth day.
Monthly mean refers to an arithmetic mean, calculated as specified
in section 6(a) of this appendix. Monthly means are computed at each
monitoring site separately for Pb-TSP and Pb-PM10 (i.e., by
site-parameter-year-month).
Parameter refers either to Pb-TSP or to Pb-PM10.
Pollutant Occurrence Code (POC) refers to a numerical code (1, 2, 3,
etc.) used to distinguish the data from two or more monitors for the
same parameter at a single monitoring site.
Scheduled sampling day means a day on which sampling is scheduled
based on the required sampling frequency for the monitoring site, as
provided in section 58.12 of this chapter.
Three-month means are arithmetic averages of three consecutive
monthly means. Three-month means are computed on a rolling, overlapping
basis. Each distinct monthly mean will be included in three different 3-
month means; for example, in a given year, a November mean would be
included in: (1) The September-October-November 3-month mean, (2) the
October-November-December 3-month mean, and (3) the November-December-
January(of the following year) 3-month mean. Three-month means are
computed separately for each parameter per section 6(a) (and are
referred to as 3-month parameter means) and are validated according to
the criteria specified in section 4(c). The parameter-specific 3-month
means are then prioritized according to section 2(a) to determine a
single 3-month site mean.
Year refers to a calendar year.
2. Use of Pb-PM10 Data as Surrogate Pb-TSP Data.
(a) As stipulated in section 2.10 of Appendix C to 40 CFR part 58,
at some mandatory Pb monitoring locations, monitoring agencies are
required to sample for Pb as Pb-TSP, and at other mandatory Pb
monitoring sites, monitoring agencies are permitted to monitor for Pb-
PM10 in lieu of Pb-TSP. In either situation, valid collocated
Pb data for the other parameter may be produced. Additionally, there may
be non-required monitoring locations that also produce valid Pb-TSP and/
or valid Pb-PM10 data. Pb-TSP data and Pb-PM10
data are always processed separately when computing monthly and 3-month
parameter means; monthly and 3-month parameter means are validated
according to the criteria stated in section 4 of this appendix. Three-
month ``site'' means, which are the final valid 3-month mean from which
a design value is identified, are determined from the one or two
available valid 3-month parameter means according to the following
prioritization which applies to all Pb monitoring locations.
(i) Whenever a valid 3-month Pb-PM10 mean shows a
violation and either is greater than a corresponding (collocated) 3-
month Pb-TSP mean or there is no corresponding valid 3-month Pb-TSP mean
present, then that 3-month Pb-PM10 mean will be the site-
level mean for that (site's) 3-month period.
(ii) Otherwise (i.e., there is no valid violating 3-month Pb-
PM10 that exceeds a corresponding 3-month Pb-TSP mean),
(A) If a valid 3-month Pb-TSP mean exists, then it will be the site-
level mean for that (site's) 3-month period, or
(B) If a valid 3-month Pb-TSP mean does not exist, then there is no
valid 3-month site mean for that period (even if a valid non-violating
3-month Pb-PM10 mean exists).
(b) As noted in section 1(a) of this appendix, FRM/FEM Pb-
PM10 data will be processed at face value (i.e., at reported
concentrations) without adjustment when computing means and making NAAQS
comparisons.
3. Requirements for Data Used for Comparisons With the Pb NAAQS and
Data Reporting Considerations.
(a) All valid FRM/FEM Pb-TSP data and all valid FRM/FEM Pb-
PM10 data submitted to EPA's Air Quality System (AQS), or
otherwise available to EPA, meeting the requirements of part 58 of this
chapter including appendices A, C, and E shall be used in design value
calculations. Pb-TSP and Pb-PM10 data representing sample
collection periods prior to January 1, 2009 (i.e., ``pre-rule'' data)
will also be considered valid for NAAQS comparisons and related
attainment/nonattainment determinations if the sampling and analysis
methods that were utilized to collect that data were consistent with
previous or newly designated FRMs or FEMs and with either the provisions
of part 58 of this chapter including appendices A, C,
[[Page 157]]
and E that were in effect at the time of original sampling or that are
in effect at the time of the attainment/nonattainment determination, and
if such data are submitted to AQS prior to September 1, 2009.
(b) Pb-TSP and Pb-PM10 measurement data are reported to
AQS in units of micrograms per cubic meter ([micro]g/m\3\) at local
conditions (local temperature and pressure, LC) to three decimal places;
any additional digits to the right of the third decimal place are
truncated. Pre-rule Pb-TSP and Pb-PM10 concentration data
that were reported in standard conditions (standard temperature and
standard pressure, STP) will not require a conversion to local
conditions but rather, after truncating to three decimal places and
processing as stated in this appendix, shall be compared ``as is'' to
the NAAQS (i.e., the LC to STP conversion factor will be assumed to be
one). However, if the monitoring agency has retroactively resubmitted
Pb-TSP or Pb-PM10 pre-rule data converted from STP to LC
based on suitable meteorological data, only the LC data will be used.
(c) At each monitoring location (site), Pb-TSP and Pb-
PM10 data are to be processed separately when selecting daily
data by day (as specified in section 3(d) of this appendix), when
aggregating daily data by month (per section 6(a)), and when forming 3-
month means (per section 6(b)). However, when deriving (i.e.,
identifying) the design value for the 38-month period, 3-month means for
the two data types may be considered together; see sections 2(a) and
4(e) of this appendix for details.
(d) Daily values for sites will be selected for a site on a size cut
(Pb-TSP or Pb-PM10, i.e., ``parameter'') basis; Pb-TSP
concentrations and Pb-PM10 concentrations shall not be
commingled in these determinations. Site level, parameter-specific daily
values will be selected as follows:
(i) The starting dataset for a site-parameter shall consist of the
measured daily concentrations recorded from the designated primary FRM/
FEM monitor for that parameter. The primary monitor for each parameter
shall be designated in the appropriate state or local agency annual
Monitoring Network Plan. If no primary monitor is designated, the
Administrator will select which monitor to treat as primary. All daily
values produced by the primary sampler are considered part of the site-
parameter data record (i.e., that site-parameter's set of daily values);
this includes all creditable samples and all extra samples. For pre-rule
Pb-TSP and Pb-PM10 data, valid data records present in AQS
for the monitor with the lowest occurring Pollutant Occurrence Code
(POC), as selected on a site-parameter-daily basis, will constitute the
site-parameter data record. Where pre-rule Pb-TSP data (or subsequent
non-required Pb-TSP or Pb-PM10 data) are reported in
``composite'' form (i.e., multiple filters for a month of sampling that
are analyzed together), the composite concentration will be used as the
site-parameter monthly mean concentration if there are no valid daily
Pb-TSP data reported for that month with a lower POC.
(ii) Data for the primary monitor for each parameter shall be
augmented as much as possible with data from collocated (same parameter)
FRM/FEM monitors. If a valid 24-hour measurement is not produced from
the primary monitor for a particular day (scheduled or otherwise), but a
valid sample is generated by a collocated (same parameter) FRM/FEM
instrument, then that collocated value shall be considered part of the
site-parameter data record (i.e., that site-parameter's monthly set of
daily values). If more than one valid collocated FRM/FEM value is
available, the mean of those valid collocated values shall be used as
the daily value. Note that this step will not be necessary for pre-rule
data given the daily identification presumption for the primary monitor.
(e) All daily values in the composite site-parameter record are used
in monthly mean calculations. However, not all daily values are given
credit towards data completeness requirements. Only ``creditable''
samples are given credit for data completeness. Creditable samples
include valid samples on scheduled sampling days and valid make-up
samples. All other types of daily values are referred to as ``extra''
samples. Make-up samples taken in the (first week of the) month after
the one in which the miss/void occurred will be credited for data
capture in the month of the miss/void but will be included in the month
actually taken when computing monthly means. For example, if a make-up
sample was taken in February to replace a missed sample scheduled for
January, the make-up concentration would be included in the February
monthly mean but the sample credited in the January data capture rate.
4. Comparisons With the Pb NAAQS.
(a) The Pb NAAQS is met at a monitoring site when the identified
design value is valid and less than or equal to 0.15 micrograms per
cubic meter ([micro]g/m\3\). A Pb design value that meets the NAAQS
(i.e., 0.15 [micro]g/m\3\ or less), is considered valid if it
encompasses 36 consecutive valid 3-month site means (specifically for a
3-year calendar period and the two previous months). For sites that
begin monitoring Pb after this rule is effective but before January 15,
2010 (or January 15, 2011), a 2010-2012 (or 2011-2013) Pb design value
that meets the NAAQS will be considered valid if it encompasses at least
34 consecutive valid 3-month means (specifically encompassing only the
3-year calendar period). See 4(c) of this appendix for the description
of a valid 3-month mean and section 6(d) for the definition of the
design value.
[[Page 158]]
(b) The Pb NAAQS is violated at a monitoring site when the
identified design value is valid and is greater than 0.15 [micro]g/m\3\,
no matter whether determined from Pb-TSP or Pb-PM10 data. A
Pb design value greater than 0.15 [micro]g/m\3\ is valid no matter how
many valid 3-month means in the 3-year period it encompasses; that is, a
violating design value is valid even if it (i.e., the highest 3-month
mean) is the only valid 3-month mean in the 3-year timeframe. Further, a
site does not have to monitor for three full calendar years in order to
have a valid violating design value; a site could monitor just three
months and still produce a valid (violating) design value.
(c)(i) A 3-month parameter mean is considered valid (i.e., meets
data completeness requirements) if the average of the data capture rate
of the three constituent monthly means (i.e., the 3-month data capture
rate) is greater than or equal to 75 percent. Monthly data capture rates
(expressed as a percentage) are specifically calculated as the number of
creditable samples for the month (including any make-up samples taken
the subsequent month for missed samples in the month in question, and
excluding any make-up samples taken in the month in question for missed
samples in the previous month) divided by the number of scheduled
samples for the month, the result then multiplied by 100 but not
rounded. The 3-month data capture rate is the sum of the three
corresponding unrounded monthly data capture rates divided by three and
the result rounded to the nearest integer (zero decimal places). As
noted in section 3(c), Pb-TSP and Pb-PM10 daily values are
processed separately when calculating monthly means and data capture
rates; a Pb-TSP value cannot be used as a make-up for a missing Pb-
PM10 value or vice versa. For purposes of assessing data
capture, Pb-TSP and Pb-PM10 data collected before January 1,
2009 will be treated with an assumed scheduled sampling frequency of
every sixth day.
(ii) A 3-month parameter mean that does not have at least 75 percent
data capture and thus is not considered valid under 4(c)(i) shall be
considered valid (and complete) if it passes either of the two following
``data substitution'' tests, one such test for validating an above
NAAQS-level (i.e., violating) 3-month Pb-TSP or Pb-PM10 mean
(using actual ``low'' reported values from the same site at about the
same time of the year (i.e., in the same month) looking across three or
four years), and the second test for validating a below-NAAQS level 3-
month Pb-TSP mean (using actual ``high'' values reported for the same
site at about the same time of the year (i.e., in the same month)
looking across three or four years). Note that both tests are merely
diagnostic in nature intending to confirm that there is a very high
likelihood if not certainty that the original mean (the one with less
than 75% data capture) reflects the true over/under NAAQS-level status
for that 3-month period; the result of one of these data substitution
tests (i.e., a ``test mean'', as defined in section 4(c)(ii)(A) or
4(c)(ii)(B)) is not considered the actual 3-month parameter mean and
shall not be used in the determination of design values. For both types
of data substitution, substitution is permitted only if there are
available data points from which to identify the high or low 3-year
month-specific values, specifically if there are at least 10 data points
total from at least two of the three (or four for November and December)
possible year-months. Data substitution may only use data of the same
parameter type.
(A) The ``above NAAQS level'' test is as follows: Data substitution
will be done in each month of the 3-month period that has less than 75
percent data capture; monthly capture rates are temporarily rounded to
integers (zero decimals) for this evaluation. If by substituting the
lowest reported daily value for that month (year non-specific; e.g., for
January) over the 38-month design value period in question for missing
scheduled data in the deficient months (substituting only enough to meet
the 75 percent data capture minimum), the computation yields a
recalculated test 3-month parameter mean concentration above the level
of the standard, then the 3-month period is deemed to have passed the
diagnostic test and the level of the standard is deemed to have been
exceeded in that 3-month period. As noted in section 4(c)(ii), in such a
case, the 3-month parameter mean of the data actually reported, not the
recalculated (``test'') result including the low values, shall be used
to determine the design value.
(B) The ``below NAAQS level'' test is as follows: Data substitution
will be performed for each month of the 3-month period that has less
than 75 percent but at least 50 percent data capture; if any month has
less than 50% data capture then the 3-month mean can not utilize this
substitution test. Also, incomplete 3-month Pb-PM10 means can
not utilize this test. A 3-month Pb-TSP mean with less than 75% data
capture shall still be considered valid (and complete) if, by
substituting the highest reported daily value, month-specific, over the
3-year design value period in question, for all missing scheduled data
in the deficient months (i.e., bringing the data capture rate up to
100%), the computation yields a recalculated 3-month parameter mean
concentration equal or less than the level of the standard (0.15
[micro]g/m\3\), then the 3-month mean is deemed to have passed the
diagnostic test and the level of the standard is deemed not to have been
exceeded in that 3-month period (for that parameter). As noted in
section 4(c)(ii), in such a case, the 3-month parameter mean of the data
actually reported, not the recalculated (``test'') result
[[Page 159]]
including the high values, shall be used to determine the design value.
(d) Months that do not meet the completeness criteria stated in
4(c)(i) or 4(c)(ii), and design values that do not meet the completeness
criteria stated in 4(a) or 4(b), may also be considered valid (and
complete) with the approval of, or at the initiative of, the
Administrator, who may consider factors such as monitoring site
closures/moves, monitoring diligence, the consistency and levels of the
valid concentration measurements that are available, and nearby
concentrations in determining whether to use such data.
(e) The site-level design value for a 38-month period (three
calendar years plus two previous months) is identified from the
available (between one and 36) valid 3-month site means. In a situation
where there are valid 3-month means for both parameters (Pb-TSP and Pb-
PM10), the mean originating from the reported Pb-TSP data
will be the one deemed the site-level monthly mean and used in design
value identifications unless the Pb-PM10 mean shows a
violation of the NAAQS and exceeds the Pb-TSP mean; see section 2(a) for
details. A monitoring site will have only one site-level 3-month mean
per 3-month period; however, the set of site-level 3-month means
considered for design value identification (i.e., one to 36 site-level
3-month means) can be a combination of Pb-TSP and Pb-PM10
data.
(f) The procedures for calculating monthly means and 3-month means,
and identifying Pb design values are given in section 6 of this
appendix.
5. Rounding Conventions.
(a) Monthly means and monthly data capture rates are not rounded.
(b) Three-month means shall be rounded to the nearest hundredth
[micro]g/m\3\ (0.xx). Decimals 0.xx5 and greater are rounded up, and any
decimal lower than 0.xx5 is rounded down. E.g., a 3-month mean of
0.104925 rounds to 0.10 and a 3-month mean of .10500 rounds to 0.11.
Three-month data capture rates, expressed as a percent, are round to
zero decimal places.
(c) Because a Pb design value is simply a (highest) 3-month mean and
because the NAAQS level is stated to two decimal places, no additional
rounding beyond what is specified for 3-month means is required before a
design value is compared to the NAAQS.
6. Procedures and Equations for the Pb NAAQS.
(a)(i) A monthly mean value for Pb-TSP (or Pb-PM10) is
determined by averaging the daily values of a calendar month using
equation 1 of this appendix, unless the Administrator chooses to
exercise his discretion to use the alternate approach described in
6(a)(ii).
[GRAPHIC] [TIFF OMITTED] TR12NO08.001
Where:
Xm,y,s = the mean for month m of the year y for sites; and
nm = the number of daily values in the month (creditable plus extra
samples); and
Xi,m,y,s = the i\th\ value in month m for year y for site s.
(a)(ii) The Administrator may at his discretion use the following
alternate approach to calculating the monthly mean concentration if the
number of extra sampling days during a month is greater than the number
of successfully completed scheduled and make-up sample days in that
month. In exercising his discretion, the Administrator will consider
whether the approach specified in 6(a)(i) might in the Administrator's
judgment result in an unrepresentative value for the monthly mean
concentration. This provision is to protect the integrity of the monthly
and 3-month mean concentration values in situations in which, by
intention or otherwise, extra sampling days are concentrated in a period
during which ambient concentrations are particularly high or low. The
alternate approach is to average all extra and make-up samples (in the
given month) taken after each scheduled sampling day (``Day X'') and
before the next scheduled sampling day (e.g., ``Day X + 6'', in the case
of one-in-six sampling) with the sample taken on Day X (assuming valid
data was obtained on the scheduled sampling day), and then averaging
these averages to calculate the monthly mean. This approach has the
effect of giving approximately equal weight to periods during a month
that have equal number of days, regardless of how many samples were
actually obtained during the periods, thus mitigating the potential for
the monthly mean to be distorted. The first day of scheduled sampling
typically will not fall on the first day of the calendar month, and
there may be make-up and/or extra samples (in that same calendar month)
preceding the first scheduled day of the month. These samples will not
be shifted into the previous month's mean concentration, but rather will
stay associated with their actual calendar month as follows. Any extra
and make-up samples taken in a month before the first scheduled sampling
day of the month will be associated with and averaged with the last
scheduled sampling day of that same month.
(b) Three-month parameter means are determined by averaging three
consecutive monthly means of the same parameter using Equation 2 of this
appendix.
[[Page 160]]
[GRAPHIC] [TIFF OMITTED] TR12NO08.002
Where:
Xm1, m2, m3; s = the 3-month parameter mean for months m1, m2, and m3
for site s; and
nm = the number of monthly means available to be averaged (typically 3,
sometimes 1 or 2 if one or two months have no valid daily
values); and
Xm, y: z, s = The mean for month m of the year y (or z) for site s.
(c) Three-month site means are determined from available 3-month
parameter means according to the hierarchy established in 2(a) of this
appendix.
(d) The site-level Pb design value is the highest valid 3-month
site-level mean over the most recent 38-month period (i.e., the most
recent 3-year calendar period plus two previous months). Section 4(a) of
this appendix explains when the identified design value is itself
considered valid for purposes of determining that the NAAQS is met or
violated at a site.
[73 FR 67054, Nov. 12, 2008]
Sec. Appendix S to Part 50--Interpretation of the Primary National
Ambient Air Quality Standards for Oxides of Nitrogen (Nitrogen Dioxide)
1. General
(a) This appendix explains the data handling conventions and
computations necessary for determining when the primary national ambient
air quality standards for oxides of nitrogen as measured by nitrogen
dioxide (``NO2 NAAQS'') specified in 50.11 are met. Nitrogen
dioxide (NO2) is measured in the ambient air by a Federal
reference method (FRM) based on appendix F to this part or by a Federal
equivalent method (FEM) designated in accordance with part 53 of this
chapter. Data handling and computation procedures to be used in making
comparisons between reported NO2 concentrations and the
levels of the NO2 NAAQS are specified in the following
sections.
(b) Whether to exclude, retain, or make adjustments to the data
affected by exceptional events, including natural events, is determined
by the requirements and process deadlines specified in 50.1, 50.14 and
51.930 of this chapter.
(c) The terms used in this appendix are defined as follows:
Annual mean refers to the annual average of all of the 1-hour
concentration values as defined in section 5.1 of this appendix.
Daily maximum 1-hour values for NO2 refers to the maximum
1-hour NO2 concentration values measured from midnight to
midnight (local standard time) that are used in NAAQS computations.
Design values are the metrics (i.e., statistics) that are compared
to the NAAQS levels to determine compliance, calculated as specified in
section 5 of this appendix. The design values for the primary NAAQS are:
(1) The annual mean value for a monitoring site for one year
(referred to as the ``annual primary standard design value'').
(2) The 3-year average of annual 98th percentile daily maximum 1-
hour values for a monitoring site (referred to as the ``1-hour primary
standard design value'').
98th percentile daily maximum 1-hour value is the value below which
nominally 98 percent of all daily maximum 1-hour concentration values
fall, using the ranking and selection method specified in section 5.2 of
this appendix.
Quarter refers to a calendar quarter.
Year refers to a calendar year.
2. Requirements for Data Used for Comparisons With the NO2
NAAQS and Data Reporting Considerations
(a) All valid FRM/FEM NO2 hourly data required to be
submitted to EPA's Air Quality System (AQS), or otherwise available to
EPA, meeting the requirements of part 58 of this chapter including
appendices A, C, and E shall be used in design value calculations.
Multi-hour average concentration values collected by wet chemistry
methods shall not be used.
(b) When two or more NO2 monitors are operated at a site,
the State may in advance designate one of them as the primary monitor.
If the State has not made this designation, the Administrator will make
the designation, either in advance or retrospectively. Design values
will be developed using only the data from the primary monitor, if this
results in a valid design value. If data from the primary monitor do not
allow the development of a valid design value, data solely from the
other monitor(s) will be used in turn to develop a valid design value,
if this results in a valid design value. If there are three or more
monitors, the order for such comparison of the other monitors will be
determined by the Administrator. The Administrator may combine data from
different monitors in different years for the purpose of developing a
valid 1-hour primary standard design value, if a valid design value
cannot be developed solely with the data from a single monitor. However,
data from two or more monitors in the same year at the same site will
not be combined in an attempt to meet data completeness requirements,
except if one monitor has physically replaced another instrument
permanently, in
[[Page 161]]
which case the two instruments will be considered to be the same
monitor, or if the State has switched the designation of the primary
monitor from one instrument to another during the year.
(c) Hourly NO2 measurement data shall be reported to AQS
in units of parts per billion (ppb), to at most one place after the
decimal, with additional digits to the right being truncated with no
further rounding.
3. Comparisons With the NO2 NAAQS
3.1 The Annual Primary NO2 NAAQS
(a) The annual primary NO2 NAAQS is met at a site when
the valid annual primary standard design value is less than or equal to
53 parts per billion (ppb).
(b) An annual primary standard design value is valid when at least
75 percent of the hours in the year are reported.
(c) An annual primary standard design value based on data that do
not meet the completeness criteria stated in section 3.1(b) may also be
considered valid with the approval of, or at the initiative of, the
Administrator, who may consider factors such as monitoring site
closures/moves, monitoring diligence, the consistency and levels of the
valid concentration measurements that are available, and nearby
concentrations in determining whether to use such data.
(d) The procedures for calculating the annual primary standard
design values are given in section 5.1 of this appendix.
3.2 The 1-hour Primary NO2 NAAQS
(a) The 1-hour primary NO2 NAAQS is met at a site when
the valid 1-hour primary standard design value is less than or equal to
100 parts per billion (ppb).
(b) An NO2 1-hour primary standard design value is valid
if it encompasses three consecutive calendar years of complete data. A
year meets data completeness requirements when all 4 quarters are
complete. A quarter is complete when at least 75 percent of the sampling
days for each quarter have complete data. A sampling day has complete
data if 75 percent of the hourly concentration values, including State-
flagged data affected by exceptional events which have been approved for
exclusion by the Administrator, are reported.
(c) In the case of one, two, or three years that do not meet the
completeness requirements of section 3.2(b) of this appendix and thus
would normally not be useable for the calculation of a valid 3-year 1-
hour primary standard design value, the 3-year 1-hour primary standard
design value shall nevertheless be considered valid if one of the
following conditions is true.
(i) At least 75 percent of the days in each quarter of each of three
consecutive years have at least one reported hourly value, and the
design value calculated according to the procedures specified in section
5.2 is above the level of the primary 1-hour standard.
(ii)(A) A 1-hour primary standard design value that is below the
level of the NAAQS can be validated if the substitution test in section
3.2(c)(ii)(B) results in a ``test design value'' that is below the level
of the NAAQS. The test substitutes actual ``high'' reported daily
maximum 1-hour values from the same site at about the same time of the
year (specifically, in the same calendar quarter) for unknown values
that were not successfully measured. Note that the test is merely
diagnostic in nature, intended to confirm that there is a very high
likelihood that the original design value (the one with less than 75
percent data capture of hours by day and of days by quarter) reflects
the true under-NAAQS-level status for that 3-year period; the result of
this data substitution test (the ``test design value'', as defined in
section 3.2(c)(ii)(B)) is not considered the actual design value. For
this test, substitution is permitted only if there are at least 200 days
across the three matching quarters of the three years under
consideration (which is about 75 percent of all possible daily values in
those three quarters) for which 75 percent of the hours in the day,
including State-flagged data affected by exceptional events which have
been approved for exclusion by the Administrator, have reported
concentrations. However, maximum 1-hour values from days with less than
75 percent of the hours reported shall also be considered in identifying
the high value to be used for substitution.
(B) The substitution test is as follows: Data substitution will be
performed in all quarter periods that have less than 75 percent data
capture but at least 50 percent data capture, including State-flagged
data affected by exceptional events which have been approved for
exclusion by the Administrator; if any quarter has less than 50 percent
data capture then this substitution test cannot be used. Identify for
each quarter (e.g., January-March) the highest reported daily maximum 1-
hour value for that quarter, excluding State-flagged data affected by
exceptional events which have been approved for exclusion by the
Administrator, looking across those three months of all three years
under consideration. All daily maximum 1-hour values from all days in
the quarter period shall be considered when identifying this highest
value, including days with less than 75 percent data capture. If after
substituting the highest non-excluded reported daily maximum 1-hour
value for a quarter for as much of the missing daily data in the
matching deficient quarter(s) as is needed to make them 100 percent
complete, the procedure in section 5.2 yields a recalculated 3-year 1-
hour standard ``test design value'' below the level of the standard,
then the 1-hour primary standard design value is deemed to have
[[Page 162]]
passed the diagnostic test and is valid, and the level of the standard
is deemed to have been met in that 3-year period. As noted in section
3.2(c)(i), in such a case, the 3-year design value based on the data
actually reported, not the ``test design value'', shall be used as the
valid design value.
(iii)(A) A 1-hour primary standard design value that is above the
level of the NAAQS can be validated if the substitution test in section
3.2(c)(iii)(B) results in a ``test design value'' that is above the
level of the NAAQS. The test substitutes actual ``low'' reported daily
maximum 1-hour values from the same site at about the same time of the
year (specifically, in the same three months of the calendar) for
unknown values that were not successfully measured. Note that the test
is merely diagnostic in nature, intended to confirm that there is a very
high likelihood that the original design value (the one with less than
75 percent data capture of hours by day and of days by quarter) reflects
the true above-NAAQS-level status for that 3-year period; the result of
this data substitution test (the ``test design value'', as defined in
section 3.2(c)(iii)(B)) is not considered the actual design value. For
this test, substitution is permitted only if there are a minimum number
of available daily data points from which to identify the low quarter-
specific daily maximum 1-hour values, specifically if there are at least
200 days across the three matching quarters of the three years under
consideration (which is about 75 percent of all possible daily values in
those three quarters) for which 75 percent of the hours in the day have
reported concentrations. Only days with at least 75 percent of the hours
reported shall be considered in identifying the low value to be used for
substitution.
(B) The substitution test is as follows: Data substitution will be
performed in all quarter periods that have less than 75 percent data
capture. Identify for each quarter (e.g., January-March) the lowest
reported daily maximum 1-hour value for that quarter, looking across
those three months of all three years under consideration. All daily
maximum 1-hour values from all days with at least 75 percent capture in
the quarter period shall be considered when identifying this lowest
value. If after substituting the lowest reported daily maximum 1-hour
value for a quarter for as much of the missing daily data in the
matching deficient quarter(s) as is needed to make them 75 percent
complete, the procedure in section 5.2 yields a recalculated 3-year 1-
hour standard ``test design value'' above the level of the standard,
then the 1-hour primary standard design value is deemed to have passed
the diagnostic test and is valid, and the level of the standard is
deemed to have been exceeded in that 3-year period. As noted in section
3.2(c)(i), in such a case, the 3-year design value based on the data
actually reported, not the ``test design value'', shall be used as the
valid design value.
(d) A 1-hour primary standard design value based on data that do not
meet the completeness criteria stated in 3.2(b) and also do not satisfy
section 3.2(c), may also be considered valid with the approval of, or at
the initiative of, the Administrator, who may consider factors such as
monitoring site closures/moves, monitoring diligence, the consistency
and levels of the valid concentration measurements that are available,
and nearby concentrations in determining whether to use such data.
(e) The procedures for calculating the 1-hour primary standard
design values are given in section 5.2 of this appendix.
4. Rounding Conventions
4.1 Rounding Conventions for the Annual Primary NO2 NAAQS
(a) Hourly NO2 measurement data shall be reported to AQS
in units of parts per billion (ppb), to at most one place after the
decimal, with additional digits to the right being truncated with no
further rounding.
(b) The annual primary standard design value is calculated pursuant
to section 5.1 and then rounded to the nearest whole number or 1 ppb
(decimals 0.5 and greater are rounded up to the nearest whole number,
and any decimal lower than 0.5 is rounded down to the nearest whole
number).
4.2 Rounding Conventions for the 1-hour Primary NO2 NAAQS
(a) Hourly NO2 measurement data shall be reported to AQS
in units of parts per billion (ppb), to at most one place after the
decimal, with additional digits to the right being truncated with no
further rounding.
(b) Daily maximum 1-hour values are not rounded.
(c) The 1-hour primary standard design value is calculated pursuant
to section 5.2 and then rounded to the nearest whole number or 1 ppb
(decimals 0.5 and greater are rounded up to the nearest whole number,
and any decimal lower than 0.5 is rounded down to the nearest whole
number).
5. Calculation Procedures for the Primary NO2 NAAQS
5.1 Procedures for the Annual Primary NO2 NAAQS
(a) When the data for a site and year meet the data completeness
requirements in section 3.1(b) of this appendix, or if the Administrator
exercises the discretionary authority in section 3.1(c), the annual mean
is simply the arithmetic average of all of the reported 1-hour values.
(b) The annual primary standard design value for a site is the valid
annual mean
[[Page 163]]
rounded according to the conventions in section 4.1.
5.2 Calculation Procedures for the 1-hour Primary NO2 NAAQS
(a) Procedure for identifying annual 98th percentile values. When
the data for a particular site and year meet the data completeness
requirements in section 3.2(b), or if one of the conditions of section
3.2(c) is met, or if the Administrator exercises the discretionary
authority in section 3.2(d), identification of annual 98th percentile
value is accomplished as follows.
(i) The annual 98th percentile value for a year is the higher of the
two values resulting from the following two procedures.
(1) Procedure 1.
(A) For the year, determine the number of days with at least 75
percent of the hourly values reported including State-flagged data
affected by exceptional events which have been approved for exclusion by
the Administrator.
(B) For the year, from only the days with at least 75 percent of the
hourly values reported, select from each day the maximum hourly value
excluding State-flagged data affected by exceptional events which have
been approved for exclusion by the Administrator.
(C) Sort all these daily maximum hourly values from a particular
site and year by descending value. (For example: (x[1], x[2], x[3], * *
*, x[n]). In this case, x[1] is the largest number and x[n] is the
smallest value.) The 98th percentile is determined from this sorted
series of daily values which is ordered from the highest to the lowest
number. Using the left column of Table 1, determine the appropriate
range (i.e., row) for the annual number of days with valid data for year
y (cny) as determined from step (A). The corresponding ``n''
value in the right column identifies the rank of the annual 98th
percentile value in the descending sorted list of daily site values for
year y. Thus, P0.98, y = the nth largest value.
(2) Procedure 2.
(A) For the year, determine the number of days with at least one
hourly value reported including State-flagged data affected by
exceptional events which have been approved for exclusion by the
Administrator.
(B) For the year, from all the days with at least one hourly value
reported, select from each day the maximum hourly value excluding State-
flagged data affected by exceptional events which have been approved for
exclusion by the Administrator.
(C) Sort all these daily maximum values from a particular site and
year by descending value. (For example: (x[1], x[2], x[3], * * *, x[n]).
In this case, x[1] is the largest number and x[n] is the smallest
value.) The 98th percentile is determined from this sorted series of
daily values which is ordered from the highest to the lowest number.
Using the left column of Table 1, determine the appropriate range (i.e.,
row) for the annual number of days with valid data for year y
(cny) as determined from step (A). The corresponding ``n''
value in the right column identifies the rank of the annual 98th
percentile value in the descending sorted list of daily site values for
year y. Thus, P0.98, y = the nth largest value.
(b) The 1-hour primary standard design value for a site is mean of
the three annual 98th percentile values, rounded according to the
conventions in section 4.
Table 1
------------------------------------------------------------------------
P0.98, y is the
nth maximum value
Annual number of days with valid data for year ``y'' of the year, where
(cny) n is the listed
number
------------------------------------------------------------------------
1-50................................................ 1
51-100.............................................. 2
101-150............................................. 3
151-200............................................. 4
201-250............................................. 5
251-300............................................. 6
301-350............................................. 7
351-366............................................. 8
------------------------------------------------------------------------
[75 FR 6532, Feb. 9, 2010]
Sec. Appendix T to Part 50--Interpretation of the Primary National
Ambient Air Quality Standards for Oxides of Sulfur (Sulfur Dioxide)
1. General
(a) This appendix explains the data handling conventions and
computations necessary for determining when the primary national ambient
air quality standards for Oxides of Sulfur as measured by Sulfur Dioxide
(``SO2 NAAQS'') specified in Sec. 50.17 are met at an
ambient air quality monitoring site. Sulfur Dioxide (SO2) is
measured in the ambient air by a Federal reference method (FRM) based on
appendix A or A-1 to this part or by a Federal equivalent method (FEM)
designated in accordance with part 53 of this chapter. Data handling and
computation procedures to be used in making comparisons between reported
SO2 concentrations and the levels of the SO2 NAAQS
are specified in the following sections.
(b) Decisions to exclude, retain, or make adjustments to the data
affected by exceptional events, including natural events, are made
according to the requirements and process deadlines specified in
Sec. Sec. 50.1, 50.14 and 51.930 of this chapter.
(c) The terms used in this appendix are defined as follows:
Daily maximum 1-hour values for SO2 refers to the maximum
1-hour SO2 concentration
[[Page 164]]
values measured from midnight to midnight (local standard time) that are
used in NAAQS computations.
Design values are the metrics (i.e., statistics) that are compared
to the NAAQS levels to determine compliance, calculated as specified in
section 5 of this appendix. The design value for the primary 1-hour
NAAQS is the 3-year average of annual 99th percentile daily maximum 1-
hour values for a monitoring site (referred to as the ``1-hour primary
standard design value'').
99th percentile daily maximum 1-hour value is the value below which
nominally 99 percent of all daily maximum 1-hour concentration values
fall, using the ranking and selection method specified in section 5 of
this appendix.
Pollutant Occurrence Code (POC) refers to a numerical code (1, 2, 3,
etc.) used to distinguish the data from two or more monitors for the
same parameter at a single monitoring site.
Quarter refers to a calendar quarter.
Year refers to a calendar year.
2. Requirements for Data Used for Comparisons With the SO2
NAAQS and Data Reporting Considerations
(a) All valid FRM/FEM SO2 hourly data required to be
submitted to EPA's Air Quality System (AQS), or otherwise available to
EPA, meeting the requirements of part 58 of this chapter including
appendices A, C, and E shall be used in design value calculations.
Multi-hour average concentration values collected by wet chemistry
methods shall not be used.
(b) Data from two or more monitors from the same year at the same
site reported to EPA under distinct Pollutant Occurrence Codes shall not
be combined in an attempt to meet data completeness requirements. The
Administrator will combine annual 99th percentile daily maximum
concentration values from different monitors in different years,
selected as described here, for the purpose of developing a valid 1-hour
primary standard design value. If more than one of the monitors meets
the completeness requirement for all four quarters of a year, the steps
specified in section 5(a) of this appendix shall be applied to the data
from the monitor with the highest average of the four quarterly
completeness values to derive a valid annual 99th percentile daily
maximum concentration. If no monitor is complete for all four quarters
in a year, the steps specified in section 3(c) and 5(a) of this appendix
shall be applied to the data from the monitor with the highest average
of the four quarterly completeness values in an attempt to derive a
valid annual 99th percentile daily maximum concentration. This paragraph
does not prohibit a monitoring agency from making a local designation of
one physical monitor as the primary monitor for a Pollutant Occurrence
Code and substituting the 1-hour data from a second physical monitor
whenever a valid concentration value is not obtained from the primary
monitor; if a monitoring agency substitutes data in this manner, each
substituted value must be accompanied by an AQS qualifier code
indicating that substitution with a value from a second physical monitor
has taken place.
(c) Hourly SO2 measurement data shall be reported to AQS
in units of parts per billion (ppb), to at most one place after the
decimal, with additional digits to the right being truncated with no
further rounding.
3. Comparisons With the 1-Hour Primary SO2 NAAQS
(a) The 1-hour primary SO2 NAAQS is met at an ambient air
quality monitoring site when the valid 1-hour primary standard design
value is less than or equal to 75 parts per billion (ppb).
(b) An SO2 1-hour primary standard design value is valid
if it encompasses three consecutive calendar years of complete data. A
year meets data completeness requirements when all 4 quarters are
complete. A quarter is complete when at least 75 percent of the sampling
days for each quarter have complete data. A sampling day has complete
data if 75 percent of the hourly concentration values, including State-
flagged data affected by exceptional events which have been approved for
exclusion by the Administrator, are reported.
(c) In the case of one, two, or three years that do not meet the
completeness requirements of section 3(b) of this appendix and thus
would normally not be useable for the calculation of a valid 3-year 1-
hour primary standard design value, the 3-year 1-hour primary standard
design value shall nevertheless be considered valid if one of the
following conditions is true.
(i) At least 75 percent of the days in each quarter of each of three
consecutive years have at least one reported hourly value, and the
design value calculated according to the procedures specified in section
5 is above the level of the primary 1-hour standard.
(ii)(A) A 1-hour primary standard design value that is equal to or
below the level of the NAAQS can be validated if the substitution test
in section 3(c)(ii)(B) results in a ``test design value'' that is below
the level of the NAAQS. The test substitutes actual ``high'' reported
daily maximum 1-hour values from the same site at about the same time of
the year (specifically, in the same calendar quarter) for unknown values
that were not successfully measured. Note that the test is merely
diagnostic in nature, intended to confirm that there is a very high
likelihood that the original design value (the one with less than 75
percent data capture of hours by day and of days by quarter) reflects
the true under-NAAQS-level status for that
[[Page 165]]
3-year period; the result of this data substitution test (the ``test
design value'', as defined in section 3(c)(ii)(B)) is not considered the
actual design value. For this test, substitution is permitted only if
there are at least 200 days across the three matching quarters of the
three years under consideration (which is about 75 percent of all
possible daily values in those three quarters) for which 75 percent of
the hours in the day, including State-flagged data affected by
exceptional events which have been approved for exclusion by the
Administrator, have reported concentrations. However, maximum 1-hour
values from days with less than 75 percent of the hours reported shall
also be considered in identifying the high value to be used for
substitution.
(B) The substitution test is as follows: Data substitution will be
performed in all quarter periods that have less than 75 percent data
capture but at least 50 percent data capture, including State-flagged
data affected by exceptional events which have been approved for
exclusion by the Administrator; if any quarter has less than 50 percent
data capture then this substitution test cannot be used. Identify for
each quarter (e.g., January-March) the highest reported daily maximum 1-
hour value for that quarter, excluding State-flagged data affected by
exceptional events which have been approved for exclusion by the
Administrator, looking across those three months of all three years
under consideration. All daily maximum 1-hour values from all days in
the quarter period shall be considered when identifying this highest
value, including days with less than 75 percent data capture. If after
substituting the highest reported daily maximum 1-hour value for a
quarter for as much of the missing daily data in the matching deficient
quarter(s) as is needed to make them 100 percent complete, the procedure
in section 5 yields a recalculated 3-year 1-hour standard ``test design
value'' less than or equal to the level of the standard, then the 1-hour
primary standard design value is deemed to have passed the diagnostic
test and is valid, and the level of the standard is deemed to have been
met in that 3-year period. As noted in section 3(c)(i), in such a case,
the 3-year design value based on the data actually reported, not the
``test design value'', shall be used as the valid design value.
(iii)(A) A 1-hour primary standard design value that is above the
level of the NAAQS can be validated if the substitution test in section
3(c)(iii)(B) results in a ``test design value'' that is above the level
of the NAAQS. The test substitutes actual ``low'' reported daily maximum
1-hour values from the same site at about the same time of the year
(specifically, in the same three months of the calendar) for unknown
hourly values that were not successfully measured. Note that the test is
merely diagnostic in nature, intended to confirm that there is a very
high likelihood that the original design value (the one with less than
75 percent data capture of hours by day and of days by quarter) reflects
the true above-NAAQS-level status for that 3-year period; the result of
this data substitution test (the ``test design value'', as defined in
section 3(c)(iii)(B)) is not considered the actual design value. For
this test, substitution is permitted only if there are a minimum number
of available daily data points from which to identify the low quarter-
specific daily maximum 1-hour values, specifically if there are at least
200 days across the three matching quarters of the three years under
consideration (which is about 75 percent of all possible daily values in
those three quarters) for which 75 percent of the hours in the day have
reported concentrations. Only days with at least 75 percent of the hours
reported shall be considered in identifying the low value to be used for
substitution.
(B) The substitution test is as follows: Data substitution will be
performed in all quarter periods that have less than 75 percent data
capture. Identify for each quarter (e.g., January-March) the lowest
reported daily maximum 1-hour value for that quarter, looking across
those three months of all three years under consideration. All daily
maximum 1-hour values from all days with at least 75 percent capture in
the quarter period shall be considered when identifying this lowest
value. If after substituting the lowest reported daily maximum 1-hour
value for a quarter for as much of the missing daily data in the
matching deficient quarter(s) as is needed to make them 75 percent
complete, the procedure in section 5 yields a recalculated 3-year 1-hour
standard ``test design value'' above the level of the standard, then the
1-hour primary standard design value is deemed to have passed the
diagnostic test and is valid, and the level of the standard is deemed to
have been exceeded in that 3-year period. As noted in section 3(c)(i),
in such a case, the 3-year design value based on the data actually
reported, not the ``test design value'', shall be used as the valid
design value.
(d) A 1-hour primary standard design value based on data that do not
meet the completeness criteria stated in 3(b) and also do not satisfy
section 3(c), may also be considered valid with the approval of, or at
the initiative of, the Administrator, who may consider factors such as
monitoring site closures/moves, monitoring diligence, the consistency
and levels of the valid concentration measurements that are available,
and nearby concentrations in determining whether to use such data.
(e) The procedures for calculating the 1-hour primary standard
design values are given in section 5 of this appendix.
[[Page 166]]
4. Rounding Conventions for the 1-Hour Primary SO2 NAAQS
(a) Hourly SO2 measurement data shall be reported to AQS
in units of parts per billion (ppb), to at most one place after the
decimal, with additional digits to the right being truncated with no
further rounding.
(b) Daily maximum 1-hour values and therefore the annual 99th
percentile of those daily values are not rounded.
(c) The 1-hour primary standard design value is calculated pursuant
to section 5 and then rounded to the nearest whole number or 1 ppb
(decimals 0.5 and greater are rounded up to the nearest whole number,
and any decimal lower than 0.5 is rounded down to the nearest whole
number).
5. Calculation Procedures for the 1-Hour Primary SO2 NAAQS
(a) Procedure for identifying annual 99th percentile values. When
the data for a particular ambient air quality monitoring site and year
meet the data completeness requirements in section 3(b), or if one of
the conditions of section 3(c) is met, or if the Administrator exercises
the discretionary authority in section 3(d), identification of annual
99th percentile value is accomplished as follows.
(i) The annual 99th percentile value for a year is the higher of the
two values resulting from the following two procedures.
(1) Procedure 1. For the year, determine the number of days with at
least 75 percent of the hourly values reported.
(A) For the year, determine the number of days with at least 75
percent of the hourly values reported including State-flagged data
affected by exceptional events which have been approved for exclusion by
the Administrator.
(B) For the year, from only the days with at least 75 percent of the
hourly values reported, select from each day the maximum hourly value
excluding State-flagged data affected by exceptional events which have
been approved for exclusion by the Administrator.
(C) Sort all these daily maximum hourly values from a particular
site and year by descending value. (For example: (x[1], x[2], x[3], * *
*, x[n]). In this case, x[1] is the largest number and x[n] is the
smallest value.) The 99th percentile is determined from this sorted
series of daily values which is ordered from the highest to the lowest
number. Using the left column of Table 1, determine the appropriate
range (i.e., row) for the annual number of days with valid data for year
y (cny). The corresponding ``n'' value in the right column
identifies the rank of the annual 99th percentile value in the
descending sorted list of daily site values for year y. Thus,
P0.99, y = the nth largest value.
(2) Procedure 2. For the year, determine the number of days with at
least one hourly value reported.
(A) For the year, determine the number of days with at least one
hourly value reported including State-flagged data affected by
exceptional events which have been approved for exclusion by the
Administrator.
(B) For the year, from all the days with at least one hourly value
reported, select from each day the maximum hourly value excluding State-
flagged data affected by exceptional events which have been approved for
exclusion by the Administrator.
(C) Sort all these daily maximum values from a particular site and
year by descending value. (For example: (x[1], x[2], x[3], * * *, x[n]).
In this case, x[1] is the largest number and x[n] is the smallest
value.) The 99th percentile is determined from this sorted series of
daily values which is ordered from the highest to the lowest number.
Using the left column of Table 1, determine the appropriate range (i.e.,
row) for the annual number of days with valid data for year y
(cny). The corresponding ``n'' value in the right column
identifies the rank of the annual 99th percentile value in the
descending sorted list of daily site values for year y. Thus,
P0.99,y = the nth largest value.
(b) The 1-hour primary standard design value for an ambient air
quality monitoring site is mean of the three annual 99th percentile
values, rounded according to the conventions in section 4.
Table 1
------------------------------------------------------------------------
P0.99,y is the nth
Annual number of days with valid data for year maximum value of the
``y'' (cny) year, where n is the
listed number
------------------------------------------------------------------------
1-100............................................. 1
101-200........................................... 2
201-300........................................... 3
301-366........................................... 4
------------------------------------------------------------------------
[75 FR 35595, June 23, 2010]
Sec. Appendix U to Part 50--Interpretation of the Primary and Secondary
National Ambient Air Quality Standards for Ozone
1. General
(a) This appendix explains the data handling conventions and
computations necessary for determining whether the primary and secondary
national ambient air quality standards (NAAQS) for ozone (O3)
specified in Sec. 50.19 are met at an ambient O3 air quality
monitoring site. Data reporting, data handling, and computation
procedures to be used in making comparisons between reported
O3 concentrations and the levels of the O3 NAAQS
are specified in the following sections.
(b) Whether to exclude or retain the data affected by exceptional
events is determined
[[Page 167]]
by the requirements under Sec. Sec. 50.1, 50.14 and 51.930.
(c) The terms used in this appendix are defined as follows:
8-hour average refers to the moving average of eight consecutive
hourly O3 concentrations measured at a site, as explained in
section 3 of this appendix.
Annual fourth-highest daily maximum refers to the fourth highest
value measured at a site during a year.
Collocated monitors refers to the instance of two or more
O3 monitors operating at the same physical location.
Daily maximum 8-hour average O3 concentration refers to the maximum
calculated 8-hour average value measured at a site on a particular day,
as explained in section 3 of this appendix.
Design value refers to the metric (i.e., statistic) that is used to
compare ambient O3 concentration data measured at a site to
the NAAQS in order to determine compliance, as explained in section 4 of
this appendix.
Minimum data completeness requirements refer to the amount of data
that a site is required to collect in order to make a valid
determination that the site is meeting the NAAQS.
Monitor refers to a physical instrument used to measure ambient
O3 concentrations.
O3 monitoring season refers to the span of time within a
year when individual states are required to measure ambient
O3 concentrations, as listed in Appendix D to part 58 of this
chapter.
Site refers to an ambient O3 air quality monitoring site.
Site data record refers to the set of hourly O3
concentration data collected at a site for use in comparisons with the
NAAQS.
Year refers to calendar year.
2. Selection of Data for use in Comparisons With the Primary and
Secondary Ozone NAAQS
(a) All valid hourly O3 concentration data collected
using a federal reference method specified in Appendix D to this part,
or an equivalent method designated in accordance with part 53 of this
chapter, meeting all applicable requirements in part 58 of this chapter,
and submitted to EPA's Air Quality System (AQS) database or otherwise
available to EPA, shall be used in design value calculations.
(b) All design value calculations shall be implemented on a site-
level basis. If data are reported to EPA from collocated monitors, those
data shall be combined into a single site data record as follows:
(i) The monitoring agency shall designate one monitor as the primary
monitor for the site.
(ii) Hourly O3 concentration data from a secondary
monitor shall be substituted into the site data record whenever a valid
hourly O3 concentration is not obtained from the primary
monitor. In the event that hourly O3 concentration data are
available for more than one secondary monitor, the hourly concentration
values from the secondary monitors shall be averaged and substituted
into the site data record.
(c) In certain circumstances, including but not limited to site
closures or relocations, data from two nearby sites may be combined into
a single site data record for the purpose of calculating a valid design
value. The appropriate Regional Administrator may approve such
combinations after taking into consideration factors such as distance
between sites, spatial and temporal patterns in air quality, local
emissions and meteorology, jurisdictional boundaries, and terrain
features.
3. Data Reporting and Data Handling Conventions
(a) Hourly average O3 concentrations shall be reported in
parts per million (ppm) to the third decimal place, with additional
digits to the right of the third decimal place truncated. Each hour
shall be identified using local standard time (LST).
(b) Moving 8-hour averages shall be computed from the hourly
O3 concentration data for each hour of the year and shall be
stored in the first, or start, hour of the 8-hour period. An 8-hour
average shall be considered valid if at least 6 of the hourly
concentrations for the 8-hour period are available. In the event that
only 6 or 7 hourly concentrations are available, the 8-hour average
shall be computed on the basis of the hours available, using 6 or 7,
respectively, as the divisor. In addition, in the event that 5 or fewer
hourly concentrations are available, the 8-hour average shall be
considered valid if, after substituting zero for the missing hourly
concentrations, the resulting 8-hour average is greater than the level
of the NAAQS, or equivalently, if the sum of the available hourly
concentrations is greater than 0.567 ppm. The 8-hour averages shall be
reported to three decimal places, with additional digits to the right of
the third decimal place truncated. Hourly O3 concentrations
that have been approved under Sec. 50.14 as having been affected by
exceptional events shall be counted as missing or unavailable in the
calculation of 8-hour averages.
(c) The daily maximum 8-hour average O3 concentration for
a given day is the highest of the 17 consecutive 8-hour averages
beginning with the 8-hour period from 7:00 a.m. to 3:00 p.m. and ending
with the 8-hour period from 11:00 p.m. to 7:00 a.m. the following day
(i.e., the 8-hour averages for 7:00 a.m. to 11:00 p.m.). Daily maximum
8-hour average O3 concentrations shall be determined for each
day with ambient O3 monitoring data, including days outside
the O3 monitoring season if those data are available.
[[Page 168]]
(d) A daily maximum 8-hour average O3 concentration shall
be considered valid if valid 8-hour averages are available for at least
13 of the 17 consecutive 8-hour periods starting from 7:00 a.m. to 11:00
p.m. In addition, in the event that fewer than 13 valid 8-hour averages
are available, a daily maximum 8-hour average O3
concentration shall also be considered valid if it is greater than the
level of the NAAQS. Hourly O3 concentrations that have been
approved under Sec. 50.14 as having been affected by exceptional events
shall be included when determining whether these criteria have been met.
(e) The primary and secondary O3 design value statistic
is the annual fourth-highest daily maximum 8-hour O3
concentration, averaged over three years, expressed in ppm. The fourth-
highest daily maximum 8-hour O3 concentration for each year
shall be determined based only on days meeting the validity criteria in
3(d). The 3-year average shall be computed using the three most recent,
consecutive years of ambient O3 monitoring data. Design
values shall be reported in ppm to three decimal places, with additional
digits to the right of the third decimal place truncated.
4. Comparisons With the Primary and Secondary Ozone NAAQS
(a) The primary and secondary national ambient air quality standards
for O3 are met at an ambient air quality monitoring site when
the 3-year average of the annual fourth-highest daily maximum 8-hour
average O3 concentration (i.e., the design value) is less
than or equal to 0.070 ppm.
(b) A design value greater than the level of the NAAQS is always
considered to be valid. A design value less than or equal to the level
of the NAAQS must meet minimum data completeness requirements in order
to be considered valid. These requirements are met for a 3-year period
at a site if valid daily maximum 8-hour average O3
concentrations are available for at least 90% of the days within the
O3 monitoring season, on average, for the 3-year period, with
a minimum of at least 75% of the days within the O3
monitoring season in any one year.
(c) When computing whether the minimum data completeness
requirements have been met, meteorological or ambient data may be
sufficient to demonstrate that meteorological conditions on missing days
were not conducive to concentrations above the level of the NAAQS.
Missing days assumed less than the level of the NAAQS are counted for
the purpose of meeting the minimum data completeness requirements,
subject to the approval of the appropriate Regional Administrator.
(d) Comparisons with the primary and secondary O3 NAAQS
are demonstrated by examples 1 and 2 as follows:
Example 1--Site Meeting the Primary and Secondary O3 NAAQS
--------------------------------------------------------------------------------------------------------------------------------------------------------
Percent valid
days within O3 1st highest 2nd highest 3rd highest 4th highest 5th highest
Year monitoring daily max 8- daily max 8- daily max 8- daily max 8- daily max 8-
season (Data hour O3 (ppm) hour O3 (ppm) hour O3 (ppm) hour O3 (ppm) hour O3 (ppm)
completeness)
--------------------------------------------------------------------------------------------------------------------------------------------------------
2014.................................................... 100 0.082 0.080 0.075 0.069 0.068
2015.................................................... 96 0.074 0.073 0.065 0.062 0.060
2016.................................................... 98 0.070 0.069 0.067 0.066 0.060
Average................................................. 98 .............. .............. .............. 0.065
--------------------------------------------------------------------------------------------------------------------------------------------------------
As shown in Example 1, this site meets the primary and secondary
O3 NAAQS because the 3-year average of the annual fourth-
highest daily maximum 8-hour average O3 concentrations (i.e.,
0.065666 ppm, truncated to 0.065 ppm) is less than or equal to 0.070
ppm. The minimum data completeness requirements are also met (i.e.,
design value is considered valid) because the average percent of days
within the O3 monitoring season with valid ambient monitoring
data is greater than 90%, and no single year has less than 75% data
completeness.
Example 2--Site Failing to Meet the Primary and Secondary O3 O3 NAAQS
--------------------------------------------------------------------------------------------------------------------------------------------------------
Percent valid
days within O3 1st highest 2nd highest 3rd highest 4th highest 5th highest
Year monitoring daily max 8- daily max 8- daily max 8- daily max 8- daily max 8-
season (Data hour O3 (ppm) hour O3 (ppm) hour O3 (ppm) hour O3 (ppm) hour O3 (ppm)
completeness)
--------------------------------------------------------------------------------------------------------------------------------------------------------
2014.................................................... 96 0.085 0.080 0.079 0.074 0.072
2015.................................................... 74 0.084 0.083 0.072 0.071 0.068
2016.................................................... 98 0.083 0.081 0.081 0.075 0.074
Average................................................. 89 .............. .............. .............. 0.073
--------------------------------------------------------------------------------------------------------------------------------------------------------
[[Page 169]]
As shown in Example 2, this site fails to meet the primary and
secondary O3 NAAQS because the 3-year average of the annual
fourth-highest daily maximum 8-hour average O3 concentrations
(i.e., 0.073333 ppm, truncated to 0.073 ppm) is greater than 0.070 ppm,
even though the annual data completeness is less than 75% in one year
and the 3-year average data completeness is less than 90% (i.e., design
value would not otherwise be considered valid).
[80 FR 65458, Oct. 26, 2015]
PART 51_REQUIREMENTS FOR PREPARATION, ADOPTION, AND SUBMITTAL OF
IMPLEMENTATION PLANS--Table of Contents
Subpart A_Air Emissions Reporting Requirements
General Information For Inventory Preparers
Sec.
51.1 Who is responsible for actions described in this subpart?
51.5 What tools are available to help prepare and report emissions data?
51.10 [Reserved]
Specific Reporting Requirements
51.15 What data does my state need to report to EPA?
51.20 What are the emission thresholds that separate point and nonpoint
sources?
51.25 What geographic area must my state's inventory cover?
51.30 When does my state report which emissions data to EPA?
51.35 How can my state equalize the emission inventory effort from year
to year?
51.40 In what form and format should my state report the data to EPA?
51.45 Where should my state report the data?
51.50 What definitions apply to this subpart?
Appendix A to Subpart A of Part 51--Tables
Appendix B to Subpart A of Part 51 [Reserved]
Subparts B-E [Reserved]
Subpart F_Procedural Requirements
51.100 Definitions.
51.101 Stipulations.
51.102 Public hearings.
51.103 Submission of plans, preliminary review of plans.
51.104 Revisions.
51.105 Approval of plans.
Subpart G_Control Strategy
51.110 Attainment and maintenance of national standards.
51.111 Description of control measures.
51.112 Demonstration of adequacy.
51.113 [Reserved]
51.114 Emissions data and projections.
51.115 Air quality data and projections.
51.116 Data availability.
51.117 Additional provisions for lead.
51.118 Stack height provisions.
51.119 Intermittent control systems.
51.120 Requirements for State Implementation Plan revisions relating to
new motor vehicles.
51.121 Findings and requirements for submission of State implementation
plan revisions relating to emissions of oxides of nitrogen.
51.122 Emissions reporting requirements for SIP revisions relating to
budgets for NOX emissions.
51.123 Findings and requirements for submission of State implementation
plan revisions relating to emissions of oxides of nitrogen
pursuant to the Clean Air Interstate Rule.
51.124 Findings and requirements for submission of State implementation
plan revisions relating to emissions of sulfur dioxide
pursuant to the Clean Air Interstate Rule.
51.125 [Reserved]
51.126 Determination of widespread use of ORVR and waiver of CAA section
182(b)(3) Stage II gasoline vapor recovery requirements.
Subpart H_Prevention of Air Pollution Emergency Episodes
51.150 Classification of regions for episode plans.
51.151 Significant harm levels.
51.152 Contingency plans.
51.153 Reevaluation of episode plans.
Subpart I_Review of New Sources and Modifications
51.160 Legally enforceable procedures.
51.161 Public availability of information.
51.162 Identification of responsible agency.
51.163 Administrative procedures.
51.164 Stack height procedures.
51.165 Permit requirements.
51.166 Prevention of significant deterioration of air quality.
Subpart J_Ambient Air Quality Surveillance
51.190 Ambient air quality monitoring requirements.
[[Page 170]]
Subpart K_Source Surveillance
51.210 General.
51.211 Emission reports and recordkeeping.
51.212 Testing, inspection, enforcement, and complaints.
51.213 Transportation control measures.
51.214 Continuous emission monitoring.
Subpart L_Legal Authority
51.230 Requirements for all plans.
51.231 Identification of legal authority.
51.232 Assignment of legal authority to local agencies.
Subpart M_Intergovernmental Consultation
Agency Designation
51.240 General plan requirements.
51.241 Nonattainment areas for carbon monoxide and ozone.
51.242 [Reserved]
Subpart N_Compliance Schedules
51.260 Legally enforceable compliance schedules.
51.261 Final compliance schedules.
51.262 Extension beyond one year.
Subpart O_Miscellaneous Plan Content Requirements
51.280 Resources.
51.281 Copies of rules and regulations.
51.285 Public notification.
51.286 Electronic reporting.
Subpart P_Protection of Visibility
51.300 Purpose and applicability.
51.301 Definitions.
51.302 Reasonably attributable visibility impairment.
51.303 Exemptions from control.
51.304 Identification of integral vistas.
51.305 Monitoring for reasonably attributable visibility impairment.
51.306 [Reserved]
51.307 New source review.
51.308 Regional haze program requirements.
51.309 Requirements related to the Grand Canyon Visibility Transport
Commission.
Subpart Q_Reports
Air Quality Data Reporting
51.320 Annual air quality data report.
Source Emissions and State Action Reporting
51.321 Annual source emissions and State action report.
51.322 Sources subject to emissions reporting.
51.323 Reportable emissions data and information.
51.324 Progress in plan enforcement.
51.326 Reportable revisions.
51.327 Enforcement orders and other State actions.
51.328 [Reserved]
Subpart R_Extensions
51.341 Request for 18-month extension.
Subpart S_Inspection/Maintenance Program Requirements
51.350 Applicability.
51.351 Enhanced I/M performance standard.
51.352 Basic I/M performance standard.
51.353 Network type and program evaluation.
51.354 Adequate tools and resources.
51.355 Test frequency and convenience.
51.356 Vehicle coverage.
51.357 Test procedures and standards.
51.358 Test equipment.
51.359 Quality control.
51.360 Waivers and compliance via diagnostic inspection.
51.361 Motorist compliance enforcement.
51.362 Motorist compliance enforcement program oversight.
51.363 Quality assurance.
51.364 Enforcement against contractors, stations and inspectors.
51.365 Data collection.
51.366 Data analysis and reporting.
51.367 Inspector training and licensing or certification.
51.368 Public information and consumer protection.
51.369 Improving repair effectiveness.
51.370 Compliance with recall notices.
51.371 On-road testing.
51.372 State Implementation Plan submissions.
51.373 Implementation deadlines.
Appendix A to Subpart S of Part 51--Calibrations, Adjustments and
Quality Control
Appendix B to Subpart S of Part 51--Test Procedures
Appendix C to Subpart S of Part 51--Steady-State Short Test Standards
Appendix D to Subpart S of Part 51--Steady-State Short Test Equipment
Appendix E to Subpart S of Part 51--Transient Test Driving Cycle
Subpart T_Conformity to State or Federal Implementation Plans of
Transportation Plans, Programs, and Projects Developed, Funded or
Approved Under Title 23 U.S.C. or the Federal Transit Laws
51.390 Implementation plan revision.
[[Page 171]]
Subpart U_Economic Incentive Programs
51.490 Applicability.
51.491 Definitions.
51.492 State program election and submittal.
51.493 State program requirements.
51.494 Use of program revenues.
Subpart W_Determining Conformity of General Federal Actions to State or
Federal Implementation Plans
51.850 [Reserved]
51.851 State implementation plan (SIP) or Tribal implementation plan
(TIP) revision.
51.852-51.860 [Reserved]
Subpart X_Provisions for Implementation of 8-hour Ozone National Ambient
Air Quality Standard
51.900 Definitions.
51.901 Applicability of part 51.
51.902 Which classification and nonattainment area planning provisions
of the CAA shall apply to areas designated nonattainment for
the 1997 8-hour NAAQS?
51.903 How do the classification and attainment date provisions in
section 181 of subpart 2 of the CAA apply to areas subject to
Sec. 51.902(a)?
51.904 How do the classification and attainment date provisions in
section 172(a) of subpart 1 of the CAA apply to areas subject
to Sec. 51.902(b)?
51.905 How do areas transition from the 1-hour NAAQS to the 1997 8-hour
NAAQS and what are the anti-backsliding provisions?
51.906 Redesignation to nonattainment following initial designations for
the 8-hour NAAQS.
51.907 For an area that fails to attain the 8-hour NAAQS by its
attainment date, how does EPA interpret sections
172(a)(2)(C)(ii) and 181(a)(5)(B) of the CAA?
51.908 What modeling and attainment demonstration requirements apply for
purposes of the 8-hour ozone NAAQS?
51.909 [Reserved]
51.910 What requirements for reasonable further progress (RFP) under
sections 172(c)(2) and 182 apply for areas designated
nonattainment for the 8-hour ozone NAAQS?
51.911 [Reserved]
51.912 What requirements apply for reasonably available control
technology (RACT) and reasonably available control measures
(RACM) under the 8-hour NAAQS?
51.913 How do the section 182(f) NOX exemption provisions
apply for the 8-hour NAAQS?
51.914 What new source review requirements apply for 8-hour ozone
nonattainment areas?
51.915 What emissions inventory requirements apply under the 8-hour
NAAQS?
51.916 What are the requirements for an Ozone Transport Region under the
8-hour NAAQS?
51.917 What is the effective date of designation for the Las Vegas, NV,
8-hour ozone nonattainment area?
51.918 Can any SIP planning requirements be suspended in 8-hour ozone
nonattainment areas that have air quality data that meets the
NAAQS?
51.919 Applicability.
Subpart Y_Mitigation Requirements
51.930 Mitigation of Exceptional Events.
Subpart Z_Provisions for Implementation of PM2.5 National
Ambient Air Quality Standards
51.1000 Definitions.
51.1001 Applicability of part 51.
51.1002 Classifications and reclassifications.
51.1003 Attainment plan due dates and submission requirements.
51.1004 Attainment dates.
51.1005 Attainment date extensions.
51.1006 Optional PM2.5 precursor demonstrations.
51.1007 [Reserved]
51.1008 Emissions inventory requirements.
51.1009 Moderate area attainment plan control strategy requirements.
51.1010 Serious area attainment plan control strategy requirements.
51.1011 Attainment demonstration and modeling requirements.
51.1012 Reasonable further progress (RFP) requirements.
51.1013 Quantitative milestone requirements.
51.1014 Contingency measures requirements.
51.1015 Clean data requirements.
51.1016 Continued applicability of the FIP and SIP requirements
pertaining to interstate transport under CAA section
110(a)(2)(D)(i) and (ii) after revocation of the 1997 primary
annual PM2.5 NAAQS.
Subpart AA_Provisions for Implementation of the 2008 Ozone National
Ambient Air Quality Standards
51.1100 Definitions.
51.1101 Applicability of part 51.
51.1102 Classification and nonattainment area planning provisions.
51.1103 Application of classification and attainment date provisions in
CAA section 181 to areas subject to Sec. 51.1102.
51.1104 [Reserved]
[[Page 172]]
51.1105 Transition from the 1997 ozone NAAQS to the 2008 ozone NAAQS and
anti-backsliding.
51.1106 Redesignation to nonattainment following initial designations.
51.1107 Determining eligibility for 1-year attainment date extensions
for the 2008 ozone NAAQS under CAA section 181(a)(5).
51.1108 Modeling and attainment demonstration requirements.
51.1109 [Reserved].
51.1110 Requirements for reasonable further progress (RFP).
51.1111 [Reserved].
51.1112 Requirements for reasonably available control technology (RACT)
and reasonably available control measures (RACM).
51.1113 Section 182(f) NOX exemption provisions.
51.1114 New source review requirements.
51.1115 Emissions inventory requirements.
51.1116 Requirements for an Ozone Transport Region.
51.1117 Fee programs for Severe and Extreme nonattainment areas that
fail to attain.
51.1118 Suspension of SIP planning requirements in nonattainment areas
that have air quality data that meet an ozone NAAQS.
51.1119 Applicability.
Subpart BB_Data Requirements for Characterizing Air Quality for the
Primary SO2 NAAQS
51.1200 Definitions.
51.1201 Purpose.
51.1202 Applicability.
51.1203 Air agency requirements.
51.1204 Enforceable emission limits providing for attainment.
51.1205 Ongoing data requirements.
Subpart CC_Provisions for Implementation of the 2015 Ozone National
Ambient Air Quality Standards
51.1300 Definitions.
51.1301 Applicability of this part.
51.1302 Classification and nonattainment area planning provisions.
51.1303 Application of classification and attainment date provisions in
CAA section 181 to areas subject to Sec. 51.1302.
Appendixes A-K to Part 51 [Reserved]
Appendix L to Part 51--Example Regulations for Prevention of Air
Pollution Emergency Episodes
Appendix M to Part 51--Recommended Test Methods for State Implementation
Plans
Appendixes N-O to Part 51 [Reserved]
Appendix P to Part 51--Minimum Emission Monitoring Requirements
Appendixes Q-R to Part 51 [Reserved]
Appendix S to Part 51--Emission Offset Interpretative Ruling
Appendixes T-U to Part 51 [Reserved]
Appendix V to Part 51--Criteria for Determining the Completeness of Plan
Submissions
Appendix W to Part 51--Guideline on Air Quality Models
Appendix X to Part 51--Examples of Economic Incentive Programs
Appendix Y to Part 51--Guidelines for BART Determinations Under the
Regional Haze Rule
Authority: 23 U.S.C. 101; 42 U.S.C. 7401-7671q.
Source: 36 FR 22398, Nov. 25, 1971, unless otherwise noted.
Subpart A_Air Emissions Reporting Requirements
Source: 73 FR 76552, Dec. 17, 2008, unless otherwise noted.
General Information for Inventory Preparers
Sec. 51.1 Who is responsible for actions described in this subpart?
States must inventory emission sources located on nontribal lands
and report this information to EPA.
Sec. 51.5 What tools are available to help prepare and report
emissions data?
(a) We urge your state to use estimation procedures described in
documents from the Emission Inventory Improvement Program (EIIP),
available at the following Internet address: http://www.epa.gov/ttn/
chief/eiip. These procedures are standardized and ranked according to
relative uncertainty for each emission estimating technique. Using this
guidance will enable others to use your state's data and evaluate its
quality and consistency with other data.
(b) Where current EIIP guidance materials have been supplanted by
state-of-the-art emission estimation approaches or are not applicable to
sources or source categories, states are urged to use applicable, state-
of-the-art techniques for estimating emissions.
[[Page 173]]
Sec. 51.10 [Reserved]
Specific Reporting Requirements
Sec. 51.15 What data does my state need to report to EPA?
(a) Pollutants. Report actual emissions of the following (see Sec.
51.50 for precise definitions as required):
(1) Required pollutants for triennial reports of annual (12-month)
emissions for all sources and every-year reports of annual emissions
from Type A sources:
(i) Sulfur dioxide (SO2).
(ii) Volatile organic compounds (VOC).
(iii) Nitrogen oxides (NOX).
(iv) Carbon monoxide (CO).
(v) Lead and lead compounds.
(vi) Primary PM2.5. As applicable, also report filterable
and condensable components.
(vii) Primary PM10. As applicable, also report filterable
and condensable components.
(viii) Ammonia (NH3).
(2) A state may, at its option, choose to report NOX and
VOC summer day emissions (or any other emissions) as required under the
Ozone Implementation Rule or report CO winter work weekday emissions for
CO nonattainment areas or CO attainment areas with maintenance plans to
the Emission Inventory System (EIS) using the data elements described in
this subpart.
(3) A state may, at its option, choose to report ozone season day
emissions of NOX as required under the NOX SIP
Call and summer day emissions of NOX that may be required
under the NOX SIP Call for controlled sources to the EIS
using the data elements described in this subpart.
(4) A state may, at its option, include estimates of emissions for
additional pollutants (such as hazardous air pollutants) in its emission
inventory reports.
(b) Sources. Emissions should be reported from the following sources
in all parts of the state, excluding sources located on tribal lands:
(1) Point.
(2) Nonpoint. States may choose to meet the requirements for some of
their nonpoint sources by accepting the EPA's estimates for the sources
for which the EPA makes calculations. In such instances, states are
encouraged to review and update the activity values or other
calculational inputs used by the EPA for these sources.
(3) Onroad and Nonroad mobile. (i) Emissions for onroad and nonroad
mobile sources must be reported as inputs to the latest EPA-developed
mobile emissions models, such as the Motor Vehicle Emissions Simulator
(MOVES) for onroad sources or the NMIM for nonroad sources. States using
these models may report, at their discretion, emissions values computed
from these models in addition to the model inputs.
(ii) In lieu of submitting model inputs for onroad and nonroad
mobile sources, California must submit emissions values.
(iii) In lieu of submitting any data, states may accept existing EPA
emission estimates.
(4) Emissions for wild and prescribed fires are not required to be
reported by states. If states wish to optionally report these sources,
they must be reported to the events data category. The events data
category is a day-specific accounting of these large-scale but usually
short duration emissions. Submissions must include both daily emissions
estimates as well as daily acres burned values. In lieu of submitting
this information, states may accept the EPA estimates or they may submit
inputs (e.g., acres burned, fuel loads) for us to use in the EPA's
estimation approach.
(c) Supporting information. You must report the data elements in
Tables 2a and 2b in Appendix A of this subpart. We may ask you for other
data on a voluntary basis to meet special purposes.
(d) Confidential data. We do not consider the data in Tables 2a and
2b in Appendix A of this subpart confidential, but some states limit
release of these types of data. Any data that you submit to EPA under
this subpart will be considered in the public domain and cannot be
treated as confidential. If Federal and state requirements are
inconsistent, consult your EPA Regional Office for a final
reconciliation.
[73 FR 76552, Dec. 17, 2008, as amended at 80 FR 8795, Feb. 19, 2015]
[[Page 174]]
Sec. 51.20 What are the emission thresholds that separate point
and nonpoint sources?
(a) All anthropogenic stationary sources must be included in your
inventory as either point or nonpoint sources.
(b) Sources that meet the definition of point source in this subpart
must be reported as point sources. All pollutants specified in Sec.
51.15(a) must be reported for point sources, not just the pollutant(s)
that qualify the source as a point source.
(c) If your state has lower emission reporting thresholds for point
sources than paragraph (b) of this section, then you may use these in
reporting your emissions to EPA.
(d) All stationary source emissions that are not reported as point
sources must be reported as nonpoint sources. Episodic wind-generated
particulate matter (PM) emissions from sources that are not major
sources may be excluded, for example dust lifted by high winds from
natural or tilled soil. Emissions of nonpoint sources should be
aggregated to the resolution required by the EIS as described in the
current National Emission Inventory (NEI) inventory year plan posted at
http://www.epa.gov/ttn/chief/eiinformation.html. In most cases, this is
county level and must be separated and identified by source
classification code (SCC). Nonpoint source categories or emission events
reasonably estimated by the state to represent a de minimis percentage
of total county and state emissions of a given pollutant may be omitted.
(1) The reporting of wild and prescribed fires is encouraged but not
required and should be done via only the ``Events'' data category.
(2) Agricultural fires (also referred to as crop residue burning)
must be reported to the nonpoint data category.
[73 FR 76552, Dec. 17, 2008, as amended at 80 FR 8795, Feb. 19, 2015]