[Title 40 CFR ]
[Code of Federal Regulations (annual edition) - July 1, 1998 Edition]
[From the U.S. Government Printing Office]
[[Page i]]
40
Protection of Environment
PARTS 50 TO 51
Revised as of July 1, 1998
CONTAINING
A CODIFICATION OF DOCUMENTS
OF GENERAL APPLICABILITY
AND FUTURE EFFECT
AS OF JULY 1, 1998
With Ancillaries
Published by
the Office of the Federal Register
National Archives and Records
Administration
as a Special Edition of
the Federal Register
[[Page ii]]
U.S. GOVERNMENT PRINTING OFFICE
WASHINGTON : 1998
For sale by U.S. Government Printing Office
Superintendent of Documents, Mail Stop: SSOP, Washington, DC 20402-9328
[[Page iii]]
Table of Contents
Page
Explanation................................................. v
Title 40:
Chapter I--Environmental Protection Agency................ 3
Finding Aids:
Material Approved for Incorporation by Reference.......... 459
Table of CFR Titles and Chapters.......................... 461
Alphabetical List of Agencies Appearing in the CFR........ 479
Table of OMB Control Numbers.............................. 489
List of CFR Sections Affected............................. 509
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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
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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
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[[Page vi]]
Many agencies have begun publishing numerous OMB control numbers as
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What is a proper incorporation by reference? The Director of the
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(a) The incorporation will substantially reduce the volume of
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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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Properly approved incorporations by reference in this volume are
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What if the material incorporated by reference cannot be found? If
you have any problem locating or obtaining a copy of material listed in
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The Federal Register Index is issued monthly in cumulative form.
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the daily Federal Register.
[[Page vii]]
A List of CFR Sections Affected (LSA) is published monthly, keyed to
the revision dates of the 50 CFR titles.
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Raymond A. Mosley,
Director,
Office of the Federal Register.
July 1, 1998.
[[Page ix]]
THIS TITLE
Title 40--Protection of Environment is composed of twenty-three
volumes. The parts in these volumes are arranged in the following order:
parts 1-49, parts 50-51, parts 52.01-52.1018, part 52.1019-end, parts
53-59, part 60, parts 61-62, part 63, parts 64-71, parts 72-80, parts
81-85, part 86, parts 87-135, 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 700-789, and part 790 to end. The contents of these
volumes represent all current regulations codified under this title of
the CFR as of July 1, 1998.
Chapter I--Environmental Protection Agency appears in all twenty-two
volumes. A Pesticide Tolerance Commodity/Chemical Index appears in parts
150-189. A Toxic Substances Chemical--CAS Number Index appears in parts
700-789 and part 790 to end. Redesignation Tables appear in the volumes
containing parts 50-51, parts 150-189, and parts 700-789. Regulations
issued by the Council on Environmental Quality appear in the volume
containing part 790 to end.
The OMB control numbers for title 40 appear in Sec. 9.1 of this
chapter. For the convenience of the user, Sec. 9.1 appears in the
Finding Aids section of the volumes containing part 50 to the end.
For this volume, Kenneth R. Payne was Chief Editor. The Code of
Federal Regulations publication program is under the direction of
Frances D. McDonald, assisted by Alomha S. Morris.
[[Page x]]
[[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
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CHAPTER I--ENVIRONMENTAL PROTECTION AGENCY
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Editorial Note: Subchapter C--Air Programs is continued in volumes 40
CFR parts 50-51, part 52.01-52.1018, part 52.1019-End, parts 53-59, part
60, parts 61-62, part 63, parts 64-71, parts 72-80, parts 81-85, part
86, and parts 87-135.
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....... 130
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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
particulate matter.
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
nitrogen dioxide.
50.12 National primary and secondary ambient air quality standards for
lead.
Appendix A 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--Measurement Principle and Calibration Procedure
for the Measurement of Ozone in the Atmosphere
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
Suspended Particulate Matter Collected From Ambient Air
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--Reference Method for the Determination of
Particulate Matter as PM10 in the Atmosphere
Appendix N to Part 50--Interpretation of the National Ambient Air
Quality Standards for Particulate Matter
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
[[Page 6]]
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.
[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]
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 the particulate
matter (PM10 and PM2.5) standards contained in
Sec. 50.7 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 PM10 and PM2.5 for purposes of
comparison to the standards contained in Sec. 50.7 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.
[62 FR 38711, July 18, 1997]
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 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
[[Page 7]]
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.
[61 FR 25579, May 22, 1996]
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 PM10.
(a) The level of the national primary and secondary 24-hour ambient
air quality standards for particulate matter is 150 micrograms per cubic
meter (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 g/m\3\, as determined
in accordance with appendix K to this part, is equal to or less than
one.
(b) The level of the national primary and secondary annual standards
for particulate matter is 50 micrograms per cubic meter (g/
m\3\), annual arithmetic mean. The standards are attained when the
expected annual arithmetic mean concentration, as determined in
accordance with appendix K to this part, is less than or equal to 50
g/m\3\.
(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.
(d) The PM10 standards set forth in this section will no
longer apply to an area not attaining these standards as of September
16, 1997, once EPA takes final action to promulgate a rule pursuant to
section 172(e) of the Clean Air Act, as amended (42 U.S.C. 7472(e))
applicable to the area. The PM10 standards set forth in this
section will no longer apply to an area attaining these standards as of
September 16, 1997, once EPA approves a State Implementation Plan (SIP)
applicable to the area containing all PM10 control measures
adopted and implemented by the State prior to September 16, 1997, and a
section 110 SIP implementing the PM standards published on July 18,
1997.
[[Page 8]]
SIP approvals are codified in 40 CFR part 52.
[52 FR 24663, July 1, 1987, as amended at 62 FR 38711, July 18, 1997]
Sec. 50.7 National primary and secondary ambient air quality standards for particulate matter.
(a) The national primary and secondary ambient air quality standards
for particulate matter are:
(1) 15.0 micrograms per cubic meter (g/m3)
annual arithmetic mean concentration, and 65 g/m3
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:
(i) A reference method based on appendix L of this part and
designated in accordance with part 53 of this chapter; or
(ii) An equivalent method designated in accordance with part 53 of
this chapter.
(2) 50 micrograms per cubic meter (g/m3) annual
arithmetic mean concentration, and 150 g/m3 24-hour
average concentration measured in the ambient air as PM10
(particles with an aerodynamic diameter less than or equal to a nominal
10 micrometers) by either:
(i) A reference method based on appendix M of this part and
designated in accordance with part 53 of this chapter; or
(ii) 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 98th 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.
(d) The annual primary and secondary PM10 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 50
micrograms per cubic meter.
(e) The 24-hour primary and secondary PM10 standards are
met when the 99th percentile 24-hour concentration, as
determined in accordance with appendix N of this part, is less than or
equal to 150 micrograms per cubic meter.
[62 FR 38711, July 18, 1997]
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
[[Page 9]]
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
g/m3). 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 g/
m3) 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 no longer
apply to an area once EPA determines that the area has air quality
meeting the 1-hour standard. Area designations are codified in 40 CFR
part 81.
[62 FR 38894, July 18, 1997]
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 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.
[62 FR 38894, July 18, 1997]
Sec. 50.11 National primary and secondary ambient air quality standards for nitrogen dioxide.
(a) The level of the national primary ambient air quality standard
for nitrogen dioxide is 0.053 parts per million (100 micrograms per
cubic meter), annual arithmetic mean concentration.
(b) The level of national secondary ambient air quality standard for
nitrogen dioxide is 0.053 parts per million (100 micrograms per cubic
meter), annual arithmetic mean concentration.
(c) The levels of the standards shall be measured by:
(1) A reference method based on appendix F and designated in
accordance with part 53 of this chapter, or
(2) An equivalent method designated in accordance with part 53 of
this chapter.
(d) The standards are 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.
[50 FR 25544, June 19, 1985]
Sec. 50.12 National primary and secondary ambient air quality standards for lead.
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.
(Secs. 109, 301(a) Clean Air Act as amended (42 U.S.C. 7409, 7601(a)))
[43 FR 46258, Oct. 5, 1978]
Appendix A 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 monochloro-
sulfonatomercurate(3) complex. Once formed, this complex resists air
oxidation(4,
[[Page 10]]
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 (g/std m3).
3.0 Range.
3.1 The lower limit of detection of SO2 in 10 mL of TCM
is 0.75 g (based on collaborative test results).(7) This
represents a concentration of 25 g SO2/m3
(0.01 ppm) in an air sample of 30 standard liters (short-term sampling)
and a concentration of 13 g SO2/m3 (0.005
ppm) in an air sample of 288 standard liters (long-term sampling).
Concentrations less than 25 g SO2/m3 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 g of SO2 in 25 mL
of final solution. This upper limit of the analysis range represents a
concentration of 1,130 g SO2/m3 (0.43
ppm) in an air sample of 30 standard liters and a concentration of 590
g SO2/m3 (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 g Fe (III),
22 g V (V), 10 g Cu (II), 10 g Mn (II), and
10 g Cr (III) in 10 mL absorbing reagent can be tolerated in
the procedure.(10) No significant interference has been encountered with
2.3 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 g/m\3\ at concentrations of 100 g/m\3\
to 7 g/m\3\ at concentrations of 400 g/
m\3\.
The day-to-day variability within an individual laboratory
(repeatability) varies linearly with concentration from 18.1
g/m\3\ at levels of 100 g/m\3\ to 50.9
g/m\3\ at levels of 400 g/m\3\.
The day-to-day variability between two or more laboratories
(reproducibility) varies linearly with concentration from
36.9 g/m\3\ at levels of 100 g/m\3\ to
103.5 g/m\3\ at levels of 400 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 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 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
41 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
(0.40.1 mm) such that a No. 79 jeweler's drill bit will pass
through the opening but a No. 78 drill bit
[[Page 11]]
will not. Clearance from the bottom of the absorber to the tip of the
stem must be 62 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 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 12]]
[[Page 13]]
[[Page 14]]
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
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 15]]
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 O35H2 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 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 16]]
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, 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
0.0300.002 absorbance unit/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 17]]
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 25SO2/
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
tubing, or Teflon 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 10.10
L/min for 30-minute sampling or 0.5000.05 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 1510 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 0.2000.020 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 18]]
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 19]]
[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 20]]
------------------------------------------------------------------------
Volume of Total
sulfite- Volume of 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 g
SO2/mL; the actual total 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 plus-minus1 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, 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
plus-minus0.002 absorbance unit/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 (plus-minus0.1 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 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 g
SO2/m3 (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 g/m3) 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 21]]
Ca = concentration of SO2 at standard conditions,
g/m3;
Pr = permeation rate, 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 22]]
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, 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 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 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, g/mL;
Ca = concentration of the standard atmosphere calculated
according to equation 12, 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 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 23]]
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 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 plus-minus 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 Reaqent 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/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 24]]
Data Form
[For hand calculations]
----------------------------------------------------------------------------------------------------------------
Absor- bance
Calibration point no. Micro- grams So2 units
----------------------------------------------------------------------------------------------------------------
(x) (y) x2 xy y2
1............................. ................. ................. ................. ................ .....
2............................. ................. ................. ................. ................ .....
3............................. ................. ................. ................. ................ .....
4............................. ................. ................. ................. ................ .....
5............................. ................. ................. ................. ................ .....
6............................. ................. ................. ................. ................ .....
----------------------------------------------------------------------------------------------------------------
x=______ y=______ x\2\=______
xy______ 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 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 g. If the difference is
greater than 1 g, the source of the discrepancy must be
identified and corrected.
12.5 Conversion of g/m3 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 25]]
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]
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 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 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 (g/std
m3). 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
g/std m3. The upper limit is determined by the point
at which the sampler can no longer maintain the specified
[[Page 26]]
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 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 27]]
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
().
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 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.
()
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.
---------------------------------------------------------------------------
()
See note at beginning of Section 7 of this appendix.
---------------------------------------------------------------------------
7.2.2 Minimum sample flow rate, heavily loaded filter: 1.1
m3/min (39 ft3/
min).
---------------------------------------------------------------------------
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 m3/min
(60 ft3/
min).
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 located in the
sample air stream together with
[[Page 28]]
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
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 m3/min over the range 1.0 to 1.8 std
m3/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 m3/min.
7.8.2 Resolution: 0.02 m3/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 m3/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 m3/min
(35-64 ft3/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 plus-minus3 deg.C variation during equilibration
period.
7.9.2 Controlled humidity: Less than 50 percent relative humidity,
constant within plus-minus5 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) and the ambient temperature (T 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 m3/min [39-60 ft3/min]), use a different
filter, or adjust the sampler flow rate. Warning: Substantial flow
adjustments may affect the
[[Page 29]]
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) and the ambient temperature (T
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
different but constant flow rates, evenly distributed, with at least
three in the specified
[[Page 30]]
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
m3 of air have passed through the standard volume meter.
Record the standard volume meter inlet pressure manometer reading as
P (column 5 in Figure 4), and the orifice manometer reading as
H (column 7 in Figure 4). Be sure to indicate the correct units
of measurement.
9.2.12 After at least 3 m3 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 m3) as
follows:
[GRAPHIC] [TIFF OMITTED] TR31AU93.024
where:
Vstd = standard volume, std m3;
Vm = actual volume measured by the standard volume meter;
P1 = barometric pressure during calibration, mm Hg or kPa;
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 m3/min) as follows:
[GRAPHIC] [TIFF OMITTED] TC08NO91.013
where:
Qstd = standard volumetric flow rate, std m3/min
t = elapsed time, minutes.
Record Qstd to the nearest 0.01 std m3/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 m3/min (35-64 ft\3\/min).
9.2.16 For each flow, compute
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:
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 (H) and the sampler flow rate indication (I) in the
appropriate columns of Figure 5.
9.3.7 Calculate 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: Qstd=1/m
H(P2/Pstd)(298/T2)-b.
Record the value of Qstd on Figure 5.
[[Page 31]]
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
m3/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
m3/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 32]]
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.
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,
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 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,
g/m\3\;
[[Page 33]]
TSP = concentration at standard conditions, 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 34]]