Appendix J to Part 50 - Reference Method for the Determination of Particulate Matter as PM10 in the Atmosphere
40:2.0.1.1.1.0.1.20.11 : Appendix J
Appendix J to Part 50 - Reference Method for the Determination of
Particulate Matter as PM10 in the Atmosphere
1.0 Applicability.
1.1 This method provides for the measurement of the mass
concentration of particulate matter with an aerodynamic diameter
less than or equal to a nominal 10 micrometers (PM1O) in ambient
air over a 24-hour period for purposes of determining attainment
and maintenance of the primary and secondary national ambient air
quality standards for particulate matter specified in § 50.6 of
this chapter. The measurement process is nondestructive, and the
PM10 sample can be subjected to subsequent physical or chemical
analyses. Quality assurance procedures and guidance are provided in
part 58, appendices A and B, of this chapter and in References 1
and 2.
2.0 Principle.
2.1 An air sampler draws ambient air at a constant flow rate
into a specially shaped inlet where the suspended particulate
matter is inertially separated into one or more size fractions
within the PM10 size range. Each size fraction in the PM1O size
range is then collected on a separate filter over the specified
sampling period. The particle size discrimination characteristics
(sampling effectiveness and 50 percent cutpoint) of the sampler
inlet are prescribed as performance specifications in part 53 of
this chapter.
2.2 Each filter is weighed (after moisture equilibration) before
and after use to determine the net weight (mass) gain due to
collected PM10. The total volume of air sampled, corrected to EPA
reference conditions (25 C, 101.3 kPa), is determined from the
measured flow rate and the sampling time. The mass concentration of
PM10 in the ambient air is computed as the total mass of collected
particles in the PM10 size range divided by the volume of air
sampled, and is expressed in micrograms per standard cubic meter
(µg/std m 3). For PM10 samples collected at temperatures and
pressures significantly different from EPA reference conditions,
these corrected concentrations sometimes differ substantially from
actual concentrations (in micrograms per actual cubic meter),
particularly at high elevations. Although not required, the actual
PM10 concentration can be calculated from the corrected
concentration, using the average ambient temperature and barometric
pressure during the sampling period.
2.3 A method based on this principle will be considered a
reference method only if (a) the associated sampler meets the
requirements specified in this appendix and the requirements in
part 53 of this chapter, and (b) the method has been designated as
a reference method in accordance with part 53 of this chapter.
3.0 Range.
3.1 The lower limit of the mass concentration range is
determined by the repeatability of filter tare weights, assuming
the nominal air sample volume for the sampler. For samplers having
an automatic filter-changing mechanism, there may be no upper
limit. For samplers that do not have an automatic filter-changing
mechanism, the upper limit is determined by the filter mass loading
beyond which the sampler no longer maintains the operating flow
rate within specified limits due to increased pressure drop across
the loaded filter. This upper limit cannot be specified precisely
because it is a complex function of the ambient particle size
distribution and type, humidity, filter type, and perhaps other
factors. Nevertheless, all samplers should be capable of measuring
24-hour PM10 mass concentrations of at least 300 µg/std m 3 while
maintaining the operating flow rate within the specified
limits.
4.0 Precision.
4.1 The precision of PM10 samplers must be 5 µg/m 3 for PM10
concentrations below 80 µg/m 3 and 7 percent for PM10
concentrations above 80 µg/m 3, as required by part 53 of this
chapter, which prescribes a test procedure that determines the
variation in the PM10 concentration measurements of identical
samplers under typical sampling conditions. Continual assessment of
precision via collocated samplers is required by part 58 of this
chapter for PM10 samplers used in certain monitoring networks.
5.0 Accuracy.
5.1 Because the size of the particles making up ambient
particulate matter varies over a wide range and the concentration
of particles varies with particle size, it is difficult to define
the absolute accuracy of PM10 samplers. Part 53 of this chapter
provides a specification for the sampling effectiveness of PM10
samplers. This specification requires that the expected mass
concentration calculated for a candidate PM10 sampler, when
sampling a specified particle size distribution, be within ±10
percent of that calculated for an ideal sampler whose sampling
effectiveness is explicitly specified. Also, the particle size for
50 percent sampling effectiveness is required to be 10 ±0.5
micrometers. Other specifications related to accuracy apply to flow
measurement and calibration, filter media, analytical (weighing)
procedures, and artifact. The flow rate accuracy of PM10 samplers
used in certain monitoring networks is required by part 58 of this
chapter to be assessed periodically via flow rate audits.
6.0 Potential Sources of Error.
6.1 Volatile Particles. Volatile particles collected on
filters are often lost during shipment and/or storage of the
filters prior to the post-sampling weighing 3. Although shipment or
storage of loaded filters is sometimes unavoidable, filters should
be reweighed as soon as practical to minimize these losses.
6.2 Artifacts. Positive errors in PM10 concentration
measurements may result from retention of gaseous species on
filters. 4 5 Such errors include the retention of sulfur dioxide
and nitric acid. Retention of sulfur dioxide on filters, followed
by oxidation to sulfate, is referred to as artifact sulfate
formation, a phenomenon which increases with increasing filter
alkalinity. 6 Little or no artifact sulfate formation should occur
using filters that meet the alkalinity specification in section
7.2.4. Artifact nitrate formation, resulting primarily from
retention of nitric acid, occurs to varying degrees on many filter
types, including glass fiber, cellulose ester, and many quartz
fiber filters. 5 7 8 9 10 Loss of true atmospheric particulate
nitrate during or following sampling may also occur due to
dissociation or chemical reaction. This phenomenon has been
observed on Teflon ® filters 8 and inferred for quartz fiber
filters. 11 12 The magnitude of nitrate artifact errors in PM10
mass concentration measurements will vary with location and ambient
temperature; however, for most sampling locations, these errors are
expected to be small.
6.3 Humidity. The effects of ambient humidity on the
sample are unavoidable. The filter equilibration procedure in
section 9.0 is designed to minimize the effects of moisture on the
filter medium.
6.4 Filter Handling. Careful handling of filters between
presampling and postsampling weighings is necessary to avoid errors
due to damaged filters or loss of collected particles from the
filters. Use of a filter cartridge or cassette may reduce the
magnitude of these errors. Filters must also meet the integrity
specification in section 7.2.3.
6.5 Flow Rate Variation. Variations in the sampler's
operating flow rate may alter the particle size discrimination
characteristics of the sampler inlet. The magnitude of this error
will depend on the sensitivity of the inlet to variations in flow
rate and on the particle distribution in the atmosphere during the
sampling period. The use of a flow control device (section 7.1.3)
is required to minimize this error.
6.6 Air Volume Determination. Errors in the air volume
determination may result from errors in the flow rate and/or
sampling time measurements. The flow control device serves to
minimize errors in the flow rate determination, and an elapsed time
meter (section 7.1.5) is required to minimize the error in the
sampling time measurement.
7.0 Apparatus.
7.1 PM10 Sampler.
7.1.1 The sampler shall be designed to:
a. Draw the air sample into the sampler inlet and through the
particle collection filter at a uniform face velocity.
b. Hold and seal the filter in a horizontal position so that
sample air is drawn downward through the filter.
c. Allow the filter to be installed and removed
conveniently.
d. Protect the filter and sampler from precipitation and prevent
insects and other debris from being sampled.
e. Minimize air leaks that would cause error in the measurement
of the air volume passing through the filter.
f. Discharge exhaust air at a sufficient distance from the
sampler inlet to minimize the sampling of exhaust air.
g. Minimize the collection of dust from the supporting
surface.
7.1.2 The sampler shall have a sample air inlet system that,
when operated within a specified flow rate range, provides particle
size discrimination characteristics meeting all of the applicable
performance specifications prescribed in part 53 of this chapter.
The sampler inlet shall show no significant wind direction
dependence. The latter requirement can generally be satisfied by an
inlet shape that is circularly symmetrical about a vertical
axis.
7.1.3 The sampler shall have a flow control device capable of
maintaining the sampler's operating flow rate within the flow rate
limits specified for the sampler inlet over normal variations in
line voltage and filter pressure drop.
7.1.4 The sampler shall provide a means to measure the total
flow rate during the sampling period. A continuous flow recorder is
recommended but not required. The flow measurement device shall be
accurate to ±2 percent.
7.1.5 A timing/control device capable of starting and stopping
the sampler shall be used to obtain a sample collection period of
24 ±1 hr (1,440 ±60 min). An elapsed time meter, accurate to within
±15 minutes, shall be used to measure sampling time. This meter is
optional for samplers with continuous flow recorders if the
sampling time measurement obtained by means of the recorder meets
the ±15 minute accuracy specification.
7.1.6 The sampler shall have an associated operation or
instruction manual as required by part 53 of this chapter which
includes detailed instructions on the calibration, operation, and
maintenance of the sampler.
7.2 Filters.
7.2.1 Filter Medium. No commercially available filter
medium is ideal in all respects for all samplers. The user's goals
in sampling determine the relative importance of various filter
characteristics (e.g., cost, ease of handling, physical and
chemical characteristics, etc.) and, consequently, determine the
choice among acceptable filters. Furthermore, certain types of
filters may not be suitable for use with some samplers,
particularly under heavy loading conditions (high mass
concentrations), because of high or rapid increase in the filter
flow resistance that would exceed the capability of the sampler's
flow control device. However, samplers equipped with automatic
filter-changing mechanisms may allow use of these types of filters.
The specifications given below are minimum requirements to ensure
acceptability of the filter medium for measurement of PM10 mass
concentrations. Other filter evaluation criteria should be
considered to meet individual sampling and analysis objectives.
7.2.2 Collection Efficiency. ≥99 percent, as measured by
the DOP test (ASTM-2986) with 0.3 µm particles at the sampler's
operating face velocity.
7.2.3 Integrity. ±5 µg/m 3 (assuming sampler's nominal
24-hour air sample volume). Integrity is measured as the PM10
concentration equivalent corresponding to the average difference
between the initial and the final weights of a random sample of
test filters that are weighed and handled under actual or simulated
sampling conditions, but have no air sample passed through them
(i.e., filter blanks). As a minimum, the test procedure must
include initial equilibration and weighing, installation on an
inoperative sampler, removal from the sampler, and final
equilibration and weighing.
7.2.4 Alkalinity. <25 microequivalents/gram of filter,
as measured by the procedure given in Reference 13 following at
least two months storage in a clean environment (free from
contamination by acidic gases) at room temperature and
humidity.
7.3 Flow Rate Transfer Standard. The flow rate transfer
standard must be suitable for the sampler's operating flow rate and
must be calibrated against a primary flow or volume standard that
is traceable to the National Bureau of Standards (NBS). The flow
rate transfer standard must be capable of measuring the sampler's
operating flow rate with an accuracy of ±2 percent.
7.4 Filter Conditioning Environment.
7.4.1 Temperature range: 15 to 30 C.
7.4.2 Temperature control: ±3 C.
7.4.3 Humidity range: 20% to 45% RH.
7.4.4 Humidity control: ±5% RH.
7.5 Analytical Balance. The analytical balance must be
suitable for weighing the type and size of filters required by the
sampler. The range and sensitivity required will depend on the
filter tare weights and mass loadings. Typically, an analytical
balance with a sensitivity of 0.1 mg is required for high volume
samplers (flow rates >0.5 m 3/min). Lower volume samplers (flow
rates <0.5 m 3/min) will require a more sensitive balance.
8.0 Calibration.
8.1 General Requirements.
8.1.1 Calibration of the sampler's flow measurement device is
required to establish traceability of subsequent flow measurements
to a primary standard. A flow rate transfer standard calibrated
against a primary flow or volume standard shall be used to
calibrate or verify the accuracy of the sampler's flow measurement
device.
8.1.2 Particle size discrimination by inertial separation
requires that specific air velocities be maintained in the
sampler's air inlet system. Therefore, the flow rate through the
sampler's inlet must be maintained throughout the sampling period
within the design flow rate range specified by the manufacturer.
Design flow rates are specified as actual volumetric flow rates,
measured at existing conditions of temperature and pressure (Qa).
In contrast, mass concentrations of PM10 are computed using flow
rates corrected to EPA reference conditions of temperature and
pressure (Qstd).
8.2 Flow Rate Calibration Procedure.
8.2.1 PM10 samplers employ various types of flow control and
flow measurement devices. The specific procedure used for flow rate
calibration or verification will vary depending on the type of flow
controller and flow indicator employed. Calibration in terms of
actual volumetric flow rates (Qa) is generally recommended, but
other measures of flow rate (e.g., Qstd) may be used provided the
requirements of section 8.1 are met. The general procedure given
here is based on actual volumetric flow units (Qa) and serves to
illustrate the steps involved in the calibration of a PM10 sampler.
Consult the sampler manufacturer's instruction manual and Reference
2 for specific guidance on calibration. Reference 14 provides
additional information on the use of the commonly used measures of
flow rate and their interrelationships.
8.2.2 Calibrate the flow rate transfer standard against a
primary flow or volume standard traceable to NBS. Establish a
calibration relationship (e.g., an equation or family of curves)
such that traceability to the primary standard is accurate to
within 2 percent over the expected range of ambient conditions
(i.e., temperatures and pressures) under which the transfer
standard will be used. Recalibrate the transfer standard
periodically.
8.2.3 Following the sampler manufacturer's instruction manual,
remove the sampler inlet and connect the flow rate transfer
standard to the sampler such that the transfer standard accurately
measures the sampler's flow rate. Make sure there are no leaks
between the transfer standard and the sampler.
8.2.4 Choose a minimum of three flow rates (actual m 3/min),
spaced over the acceptable flow rate range specified for the inlet
(see 7.1.2) that can be obtained by suitable adjustment of the
sampler flow rate. In accordance with the sampler manufacturer's
instruction manual, obtain or verify the calibration relationship
between the flow rate (actual m 3/min) as indicated by the transfer
standard and the sampler's flow indicator response. Record the
ambient temperature and barometric pressure. Temperature and
pressure corrections to subsequent flow indicator readings may be
required for certain types of flow measurement devices. When such
corrections are necessary, correction on an individual or daily
basis is preferable. However, seasonal average temperature and
average barometric pressure for the sampling site may be
incorporated into the sampler calibration to avoid daily
corrections. Consult the sampler manufacturer's instruction manual
and Reference 2 for additional guidance.
8.2.5 Following calibration, verify that the sampler is
operating at its design flow rate (actual m 3/min) with a clean
filter in place.
8.2.6 Replace the sampler inlet.
9.0 Procedure.
9.1 The sampler shall be operated in accordance with the
specific guidance provided in the sampler manufacturer's
instruction manual and in Reference 2. The general procedure given
here assumes that the sampler's flow rate calibration is based on
flow rates at ambient conditions (Qa) and serves to illustrate the
steps involved in the operation of a PM10 sampler.
9.2 Inspect each filter for pinholes, particles, and other
imperfections. Establish a filter information record and assign an
identification number to each filter.
9.3 Equilibrate each filter in the conditioning environment (see
7.4) for at least 24 hours.
9.4 Following equilibration, weigh each filter and record the
presampling weight with the filter identification number.
9.5 Install a preweighed filter in the sampler following the
instructions provided in the sampler manufacturer's instruction
manual.
9.6 Turn on the sampler and allow it to establish
run-temperature conditions. Record the flow indicator reading and,
if needed, the ambient temperature and barometric pressure.
Determine the sampler flow rate (actual m 3/min) in accordance with
the instructions provided in the sampler manufacturer's instruction
manual. NOTE. - No onsite temperature or pressure measurements are
necessary if the sampler's flow indicator does not require
temperature or pressure corrections or if seasonal average
temperature and average barometric pressure for the sampling site
are incorporated into the sampler calibration (see step 8.2.4). If
individual or daily temperature and pressure corrections are
required, ambient temperature and barometric pressure can be
obtained by on-site measurements or from a nearby weather station.
Barometric pressure readings obtained from airports must be station
pressure, not corrected to sea level, and may need to be corrected
for differences in elevation between the sampling site and the
airport.
9.7 If the flow rate is outside the acceptable range specified
by the manufacturer, check for leaks, and if necessary, adjust the
flow rate to the specified setpoint. Stop the sampler.
9.8 Set the timer to start and stop the sampler at appropriate
times. Set the elapsed time meter to zero or record the initial
meter reading.
9.9 Record the sample information (site location or
identification number, sample date, filter identification number,
and sampler model and serial number).
9.10 Sample for 24 ±1 hours.
9.11 Determine and record the average flow rate (Q a) in actual
m 3/min for the sampling period in accordance with the instructions
provided in the sampler manufacturer's instruction manual. Record
the elapsed time meter final reading and, if needed, the average
ambient temperature and barometric pressure for the sampling period
(see note following step 9.6).
9.12 Carefully remove the filter from the sampler, following the
sampler manufacturer's instruction manual. Touch only the outer
edges of the filter.
9.13 Place the filter in a protective holder or container (e.g.,
petri dish, glassine envelope, or manila folder).
9.14 Record any factors such as meteorological conditions,
construction activity, fires or dust storms, etc., that might be
pertinent to the measurement on the filter information record.
9.15 Transport the exposed sample filter to the filter
conditioning environment as soon as possible for equilibration and
subsequent weighing.
9.16 Equilibrate the exposed filter in the conditioning
environment for at least 24 hours under the same temperature and
humidity conditions used for presampling filter equilibration (see
9.3).
9.17 Immediately after equilibration, reweigh the filter and
record the postsampling weight with the filter identification
number.
10.0 Sampler Maintenance.
10.1 The PM10 sampler shall be maintained in strict accordance
with the maintenance procedures specified in the sampler
manufacturer's instruction manual.
11.0 Calculations.
11.1 Calculate the average flow rate over the sampling period
corrected to EPA reference conditions as Q std. When the sampler's
flow indicator is calibrated in actual volumetric units (Qa), Q std
is calculated as:
Q std = Q a × (Pav/Tav)(Tstd/Pstd) where Q std = average flow rate
at EPA reference conditions, std m 3/min; Q a = average flow rate
at ambient conditions, m 3/min; Pav = average barometric pressure
during the sampling period or average barometric pressure for the
sampling site, kPa (or mm Hg); Tav = average ambient temperature
during the sampling period or seasonal average ambient temperature
for the sampling site, K; Tstd = standard temperature, defined as
298 K; Pstd = standard pressure, defined as 101.3 kPa (or 760 mm
Hg).
11.2 Calculate the total volume of air sampled as:
Vstd = Q std × t where Vstd = total air sampled in standard volume
units, std m 3; t = sampling time, min.
11.3 Calculate the PM10 concentration as:
PM10 = (Wf−Wi) × 10 6/Vstd where PM10 = mass concentration of PM10,
µg/std m 3; Wf, Wi = final and initial weights of filter collecting
PM1O particles, g; 10 6 = conversion of g to µg. Note:
If more than one size fraction in the PM10 size range is
collected by the sampler, the sum of the net weight gain by each
collection filter [Σ(Wf−Wi)] is used to calculate the PM10 mass
concentration.
12.0 References.
1. Quality Assurance Handbook for Air Pollution Measurement
Systems, Volume I, Principles. EPA-600/9-76-005, March 1976.
Available from CERI, ORD Publications, U.S. Environmental
Protection Agency, 26 West St. Clair Street, Cincinnati, OH
45268.
2. Quality Assurance Handbook for Air Pollution Measurement
Systems, Volume II, Ambient Air Specific Methods.
EPA-600/4-77-027a, May 1977. Available from CERI, ORD Publications,
U.S. Environmental Protection Agency, 26 West St. Clair Street,
Cincinnati, OH 45268.
3. Clement, R.E., and F.W. Karasek. Sample Composition Changes
in Sampling and Analysis of Organic Compounds in Aerosols. Int. J.
Environ. Analyt. Chem., 7:109, 1979.
4. Lee, R.E., Jr., and J. Wagman. A Sampling Anomaly in the
Determination of Atmospheric Sulfate Concentration. Amer. Ind. Hyg.
Assoc. J., 27:266, 1966.
5. Appel, B.R., S.M. Wall, Y. Tokiwa, and M. Haik. Interference
Effects in Sampling Particulate Nitrate in Ambient Air. Atmos.
Environ., 13:319, 1979.
6. Coutant, R.W. Effect of Environmental Variables on Collection
of Atmospheric Sulfate. Environ. Sci. Technol., 11:873, 1977.
7. Spicer, C.W., and P. Schumacher. Interference in Sampling
Atmospheric Particulate Nitrate. Atmos. Environ., 11:873, 1977.
8. Appel, B.R., Y. Tokiwa, and M. Haik. Sampling of Nitrates in
Ambient Air. Atmos. Environ., 15:283, 1981.
9. Spicer, C.W., and P.M. Schumacher. Particulate Nitrate:
Laboratory and Field Studies of Major Sampling Interferences.
Atmos. Environ., 13:543, 1979.
10. Appel, B.R. Letter to Larry Purdue, U.S. EPA, Environmental
Monitoring and Support Laboratory. March 18, 1982, Docket No.
A-82-37, II-I-1.
11. Pierson, W.R., W.W. Brachaczek, T.J. Korniski, T.J. Truex,
and J.W. Butler. Artifact Formation of Sulfate, Nitrate, and
Hydrogen Ion on Backup Filters: Allegheny Mountain Experiment. J.
Air Pollut. Control Assoc., 30:30, 1980.
12. Dunwoody, C.L. Rapid Nitrate Loss From PM10 Filters. J. Air
Pollut. Control Assoc., 36:817, 1986.
13. Harrell, R.M. Measuring the Alkalinity of Hi-Vol Air
Filters. EMSL/RTP-SOP-QAD-534, October 1985. Available from the
U.S. Environmental Protection Agency, EMSL/QAD, Research Triangle
Park, NC 27711.
14. Smith, F., P.S. Wohlschlegel, R.S.C. Rogers, and D.J.
Mulligan. Investigation of Flow Rate Calibration Procedures
Associated With the High Volume Method for Determination of
Suspended Particulates. EPA-600/4-78-047, U.S. Environmental
Protection Agency, Research Triangle Park, NC 27711, 1978.
[52 FR 24664, July 1, 1987; 52 FR 29467, Aug. 7, 1987]