Appendix O to Part 50 - Reference Method for the Determination of Coarse Particulate Matter as PM10-2.5 in the Atmosphere
40:2.0.1.1.1.0.1.20.16 : Appendix O
Appendix O to Part 50 - Reference Method for the Determination of
Coarse Particulate Matter as PM10-2.5 in the Atmosphere 1.0
Applicability and Definition
1.1 This method provides for the measurement of the mass
concentration of coarse particulate matter (PM10-2.5) in ambient
air over a 24-hour period. In conjunction with additional analysis,
this method may be used to develop speciated data.
1.2 For the purpose of this method, PM10-2.5 is defined as
particulate matter having an aerodynamic diameter in the nominal
range of 2.5 to 10 micrometers, inclusive.
1.3 For this reference method, PM10-2.5 concentrations shall be
measured as the arithmetic difference between separate but
concurrent, collocated measurements of PM10 and PM2.5, where the
PM10 measurements are obtained with a specially approved sampler,
identified as a “PM10c sampler,” that meets more demanding
performance requirements than conventional PM10 samplers described
in appendix J of this part. Measurements obtained with a PM10c
sampler are identified as “PM10c measurements” to distinguish them
from conventional PM10 measurements obtained with conventional PM10
samplers. Thus, PM10-2.5 = PM10c − PM2.5.
1.4 The PM10c and PM2.5 gravimetric measurement processes are
considered to be nondestructive, and the PM10c and PM2.5 samples
obtained in the PM10-2.5 measurement process can be subjected to
subsequent physical or chemical analyses.
1.5 Quality assessment procedures are provided in part 58,
appendix A of this chapter. The quality assurance procedures and
guidance provided in reference 1 in section 13 of this appendix,
although written specifically for PM2.5, are generally applicable
for PM10c, and, hence, PM10-2.5 measurements under this method, as
well.
1.6 A method based on specific model PM10c and PM2.5 samplers
will be considered a reference method for purposes of part 58 of
this chapter only if:
(a) The PM10c and PM2.5 samplers and the associated operational
procedures meet the requirements specified in this appendix and all
applicable requirements in part 53 of this chapter, and
(b) The method based on the specific samplers and associated
operational procedures have been designated as a reference method
in accordance with part 53 of this chapter.
1.7 PM10-2.5 methods based on samplers that meet nearly all
specifications set forth in this method but have one or more
significant but minor deviations or modifications from those
specifications may be designated as “Class I” equivalent methods
for PM10-2.5 in accordance with part 53 of this chapter.
1.8 PM2.5 measurements obtained incidental to the PM10-2.5
measurements by this method shall be considered to have been
obtained with a reference method for PM2.5 in accordance with
appendix L of this part.
1.9 PM10c measurements obtained incidental to the PM10-2.5
measurements by this method shall be considered to have been
obtained with a reference method for PM10 in accordance with
appendix J of this part, provided that:
(a) The PM10c measurements are adjusted to EPA reference
conditions (25 °C and 760 millimeters of mercury), and
(b) Such PM10c measurements are appropriately identified to
differentiate them from PM10 measurements obtained with other
(conventional) methods for PM10 designated in accordance with part
53 of this chapter as reference or equivalent methods for PM10.
2.0
Principle
2.1 Separate, collocated, electrically powered air samplers for
PM10c and PM2.5 concurrently draw ambient air at identical,
constant volumetric flow rates into specially shaped inlets and
through one or more inertial particle size separators where the
suspended particulate matter in the PM10 or PM2.5 size range, as
applicable, is separated for collection on a
polytetrafluoroethylene (PTFE) filter over the specified sampling
period. The air samplers and other aspects of this PM10-2.5
reference method are specified either explicitly in this appendix
or by reference to other applicable regulations or quality
assurance guidance.
2.2 Each PM10c and PM2.5 sample collection filter is weighed
(after moisture and temperature conditioning) before and after
sample collection to determine the net weight (mass) gain due to
collected PM10c or PM2.5. The total volume of air sampled by each
sampler is determined by the sampler from the measured flow rate at
local ambient temperature and pressure and the sampling time. The
mass concentrations of both PM10c and PM2.5 in the ambient air are
computed as the total mass of collected particles in the PM10 or
PM2.5 size range, as appropriate, divided by the total volume of
air sampled by the respective samplers, and expressed in micrograms
per cubic meter (µg/m 3)at local temperature and pressure
conditions. The mass concentration of PM10-2.5 is determined as the
PM10c concentration value less the corresponding, concurrently
measured PM2.5 concentration value.
2.3 Most requirements for PM10-2.5 reference methods are similar
or identical to the requirements for PM2.5 reference methods as set
forth in appendix L to this part. To insure uniformity, applicable
appendix L requirements are incorporated herein by reference in the
sections where indicated rather than repeated in this appendix.
3.0
PM10-2.5
Measurement Range
3.1 Lower concentration limit. The lower detection limit
of the mass concentration measurement range is estimated to be
approximately 3 µg/m 3, based on the observed precision of PM2.5
measurements in the national PM2.5 monitoring network, the probable
similar level of precision for the matched PM10c measurements, and
the additional variability arising from the differential nature of
the measurement process. This value is provided merely as a guide
to the significance of low PM10-2.5 concentration measurements.
3.2 Upper concentration limit. The upper limit of the
mass concentration range is determined principally by the PM10c
filter mass loading beyond which the sampler can no longer maintain
the operating flow rate within specified limits due to increased
pressure drop across the loaded filter. This upper limit cannot be
specified precisely because it is a complex function of the ambient
particle size distribution and type, humidity, the individual
filter used, the capacity of the sampler flow rate control system,
and perhaps other factors. All PM10c samplers are estimated to be
capable of measuring 24-hour mass concentrations of at least 200
µg/m 3 while maintaining the operating flow rate within the
specified limits. The upper limit for the PM10-2.5 measurement is
likely to be somewhat lower because the PM10-2.5 concentration
represents only a fraction of the PM10 concentration.
3.3 Sample period. The required sample period for
PM10-2.5 concentration measurements by this method shall be at
least 1,380 minutes but not more than 1,500 minutes (23 to 25
hours), and the start times of the PM2.5 and PM10c samples are
within 10 minutes and the stop times of the samples are also within
10 minutes (see section 10.4 of this appendix).
4.0
Accuracy (bias)
4.1 Because the size, density, and volatility of the particles
making up ambient particulate matter vary over wide ranges and the
mass concentration of particles varies with particle size, it is
difficult to define the accuracy of PM10-2.5 measurements in an
absolute sense. Furthermore, generation of credible PM10-2.5
concentration standards at field monitoring sites and presenting or
introducing such standards reliably to samplers or monitors to
assess accuracy is still generally impractical. The accuracy of
PM10-2.5 measurements is therefore defined in a relative sense as
bias, referenced to measurements provided by other reference method
samplers or based on flow rate verification audits or checks, or on
other performance evaluation procedures.
4.2 Measurement system bias for monitoring data is assessed
according to the procedures and schedule set forth in part 58,
appendix A of this chapter. The goal for the measurement
uncertainty (as bias) for monitoring data is defined in part 58,
appendix A of this chapter as an upper 95 percent confidence limit
for the absolute bias of 15 percent. Reference 1 in section 13 of
this appendix provides additional information and guidance on flow
rate accuracy audits and assessment of bias.
5.0
Precision
5.1 Tests to establish initial measurement precision for each
sampler of the reference method sampler pair are specified as a
part of the requirements for designation as a reference method
under part 53 of this chapter.
5.2 Measurement system precision is assessed according to the
procedures and schedule set forth in appendix A to part 58 of this
chapter. The goal for acceptable measurement uncertainty, as
precision, of monitoring data is defined in part 58, appendix A of
this chapter as an upper 95 percent confidence limit for the
coefficient of variation (CV) of 15 percent. Reference 1 in section
13 of this appendix provides additional information and guidance on
this requirement.
6.0 Filters for PM10c and PM2.5 Sample
Collection. Sample collection filters for both PM10c and PM2.5
measurements shall be identical and as specified in section 6 of
appendix L to this part.
7.0 Sampler. The PM10-2.5 sampler shall consist of a
PM10c sampler and a PM2.5 sampler, as follows:
7.1 The PM2.5 sampler shall be as specified in section 7 of
appendix L to this part.
7.2 The PM10c sampler shall be of like manufacturer, design,
configuration, and fabrication to that of the PM2.5 sampler and as
specified in section 7 of appendix L to this part, except as
follows:
7.2.1 The particle size separator specified in section 7.3.4 of
appendix L to this part shall be eliminated and replaced by a
downtube extension fabricated as specified in Figure O-1 of this
appendix.
7.2.2 The sampler shall be identified as a PM10c sampler on its
identification label required under § 53.9(d) of this chapter.
7.2.3 The average temperature and average barometric pressure
measured by the sampler during the sample period, as described in
Table L-1 of appendix L to this part, need not be reported to EPA's
AQS data base, as required by section 7.4.19 and Table L-1 of
appendix L to this part, provided such measurements for the sample
period determined by the associated PM2.5 sampler are reported as
required.
7.3 In addition to the operation/instruction manual required by
section 7.4.18 of appendix L to this part for each sampler,
supplemental operational instructions shall be provided for the
simultaneous operation of the samplers as a pair to collect
concurrent PM10c and PM2.5 samples. The supplemental instructions
shall cover any special procedures or guidance for installation and
setup of the samplers for PM10-2.5 measurements, such as
synchronization of the samplers' clocks or timers, proper
programming for collection of concurrent samples, and any other
pertinent issues related to the simultaneous, coordinated operation
of the two samplers.
7.4 Capability for electrical interconnection of the samplers to
simplify sample period programming and further ensure simultaneous
operation is encouraged but not required. Any such capability for
interconnection shall not supplant each sampler's capability to
operate independently, as required by section 7 of appendix L of
this part.
8.0
Filter Weighing
8.1 Conditioning and weighing for both PM10c and PM2.5 sample
filters shall be as specified in section 8 of appendix L to this
part. See reference 1 of section 13 of this appendix for
additional, more detailed guidance.
8.2 Handling, conditioning, and weighing for both PM10c and
PM2.5 sample filters shall be matched such that the corresponding
PM10c and PM2.5 filters of each filter pair receive uniform
treatment. The PM10c and PM2.5 sample filters should be weighed on
the same balance, preferably in the same weighing session and by
the same analyst.
8.3 Due care shall be exercised to accurately maintain the
paired relationship of each set of concurrently collected PM10c and
PM2.5 sample filters and their net weight gain data and to avoid
misidentification or reversal of the filter samples or weight data.
See Reference 1 of section 13 of this appendix for additional
guidance.
9.0 Calibration. Calibration of the flow rate,
temperature measurement, and pressure measurement systems for both
the PM10c and PM2.5 samplers shall be as specified in section 9 of
appendix L to this part.
10.0
PM10-2.5 Measurement Procedure
10.1 The PM10c and PM2.5 samplers shall be installed at the
monitoring site such that their ambient air inlets differ in
vertical height by not more than 0.2 meter, if possible, but in any
case not more than 1 meter, and the vertical axes of their inlets
are separated by at least 1 meter but not more than 4 meters,
horizontally.
10.2 The measurement procedure for PM10c shall be as specified
in section 10 of appendix L to this part, with “PM10c” substituted
for “PM2.5” wherever it occurs in that section.
10.3 The measurement procedure for PM2.5 shall be as specified
in section 10 of appendix L to this part.
10.4 For the PM10-2.5 measurement, the PM10c and PM2.5 samplers
shall be programmed to operate on the same schedule and such that
the sample period start times are within 5 minutes and the sample
duration times are within 5 minutes.
10.5 Retrieval, transport, and storage of each PM10c and PM2.5
sample pair following sample collection shall be matched to the
extent practical such that both samples experience uniform
conditions.
11.0 Sampler Maintenance. Both PM10c and PM2.5 samplers
shall be maintained as described in section 11 of appendix L to
this part.
12.0
Calculations
12.1 Both concurrent PM10c and PM2.5 measurements must be
available, valid, and meet the conditions of section 10.4 of this
appendix to determine the PM10-2.5 mass concentration.
12.2 The PM10c mass concentration is calculated using equation 1
of this section:
Where: PM10c = mass concentration of PM10c,
µg/m 3; Wf, Wi = final and initial masses (weights), respectively,
of the filter used to collect the PM10c particle sample, µg; Va =
total air volume sampled by the PM10c sampler in actual volume
units measured at local conditions of temperature and pressure, as
provided by the sampler, m 3. Note:
Total sample time must be between 1,380 and 1,500 minutes (23
and 25 hrs) for a fully valid PM10c sample; however, see also
section 3.3 of this appendix.
12.3 The PM2.5 mass concentration is calculated as specified in
section 12 of appendix L to this part.
12.4 The PM10−2.5 mass concentration, in µg/m 3, is calculated
using Equation 2 of this section:
13.0 Reference
1. Quality Assurance Guidance Document 2.12. Monitoring PM2.5 in
Ambient Air Using Designated Reference or Class I Equivalent
Methods. Draft, November 1998 (or later version or supplement, if
available). Available at:
www.epa.gov/ttn/amtic/pgqa.html.
14.0 Figures
Figure O-1 is included as part of this appendix O.
[71 FR 61230, Oct. 17, 2006]