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[Federal Register: July 18, 1997 (Rules and Regulations)]
[Page 38752-38760]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr18jy97-18]
[[pp. 38752-38760]] National Ambient Air Quality Standards for Particulate Matter
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[GRAPHIC] [TIFF OMITTED] TR18JY97.051
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7. Appendix M is added to read as follows:
Appendix M to Part 50--Reference Method for the Determination of
Particulate Matter as PM10 in the Atmosphere
1.0 Applicability.
1.1 This method provides for the measurement of the mass
concentration of particulate matter with an aerodynamic diameter
less than or equal to a nominal 10 micrometers (PM1O ) in
ambient air over a 24-hour period for purposes of determining
attainment and maintenance of the primary and secondary national
ambient air quality standards for particulate matter specified in
Sec. 50.6 of this chapter. The measurement process is
nondestructive, and the PM10 sample can be subjected to
subsequent physical or chemical analyses. Quality assurance
procedures and guidance are provided in part 58, Appendices A and B
of this chapter and in references 1 and 2 of section 12.0 of this
appendix.
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, measured
at the actual ambient temperature and pressure, 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 actual
cubic meter (g/m3).
2.3 A method based on this principle will be considered a
reference method only if the associated sampler meets the
requirements specified in this appendix and the requirements in part
53 of this chapter, and 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
g/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
g/m\3\ for PM10 concentrations below 80
g/m\3\ and 7 percent for PM10 concentrations
above 80 g/m\3\, as required by part 53 of this chapter,
which prescribes a test procedure that determines the variation in
the PM10 concentration measurements of identical samplers
under typical sampling conditions. Continual assessment of precision
via collocated samplers is required by part 58 of this chapter for
PM10 samplers used in certain monitoring networks.
5.0 Accuracy.
5.1 Because the size of the particles making up ambient
particulate matter varies over a wide range and the concentration of
particles varies with particle size, it is difficult to define the
absolute accuracy of PM10 samplers. Part 53 of this
chapter provides a specification for the sampling effectiveness of
PM10 samplers. This specification requires that the
expected mass concentration calculated for a candidate
PM10 sampler, when sampling a specified particle size
distribution, be within 10 percent of that calculated
for an ideal sampler whose sampling effectiveness is explicitly
specified. Also, the particle size for 50 percent sampling
effectiveness is required to be 100.5 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 of this
appendix, 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&127 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 of
this appendix 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 of this appendix.
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, under section 7.1.3 of this
appendix, 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, under section 7.1.5 of this appendix, 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.
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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 m particles at the
sampler's operating face velocity.
7.2.3 Integrity. 5 g/m\3\ (assuming
sampler's nominal 24-hour air sample volume). Integrity is measured
as the PM10 concentration equivalent corresponding to the
average difference between the initial and the final weights of a
random sample of test filters that are weighed and handled under
actual or simulated sampling conditions, but have no air sample
passed through them, i.e., filter blanks. As a minimum, the test
procedure must include initial equilibration and weighing,
installation on an inoperative sampler, removal from the sampler,
and final equilibration and weighing.
7.2.4 Alkalinity. <25 microequivalents/gram of filter, as measured by the procedure given in reference 13 of section 12.0 of this appendix 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 Institute of Standard and Technology (NIST). 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 ).
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 rate indicator employed.
Calibration is in terms of actual volumetric flow rates
(Qa ) to meet the requirements of section 8.1 of this
appendix. The general procedure given here serves to illustrate the
steps involved in the calibration. Consult the sampler
manufacturer's instruction manual and reference 2 of section 12.0 of
this appendix for specific guidance on calibration. Reference 14 of
section 12.0 of this appendix provides additional information on
various other 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 NIST. 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,
under section 7.1.2 of the appendix, 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 in section 12.0 of this appendix 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 in section 12.0 of this appendix. 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 (a) 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.
(b) 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
[[Page 38755]]
the sampler calibration, under section 8.2.4 of this appendix. 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 241 hours.
9.11 Determine and record the average flow rate (Qa )
in actual m\3\/min for the sampling period in accordance with the
instructions provided in the sampler manufacturer's instruction
manual. Record the elapsed time meter final reading and, if needed,
the average ambient temperature and barometric pressure for the
sampling period, in note following section 9.6 of this appendix.
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
section 9.3 of this appendix).
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 total volume of air sampled as:
V = Qa t
where:
V = total air sampled, at ambient temperature and
pressure,m3;
Qa = average sample flow rate at ambient temperature and
pressure, m3/min; and
t = sampling time, min.
11.2 (a) Calculate the PM10 concentration as:
PM10 = (Wf -Wi ) x 10\6\/V
where:
PM10 = mass concentration of PM10 , g/
m\3\;
Wf , Wi = final and initial weights of filter
collecting PM1O particles, g; and
10\6\ = conversion of g to g.
(b) 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
[(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.
8. Appendix N is added to read as follows:
Appendix N to Part 50--Interpretation of the National Ambient Air
Quality Standards for Particulate Matter
1.0 General.
(a) This appendix explains the data handling conventions and
computations necessary for determining when the annual and 24-hour
primary and secondary national ambient air quality standards for PM
specified in Sec. 50.7 of this chapter are met. Particulate matter
is measured in the ambient air as PM10 and
PM2.5 (particles with an aerodynamic diameter less than
or equal to a nominal 10 and 2.5 micrometers, respectively) by a
reference method based on Appendix M of this part for
PM10 and on Appendix L of this part for PM2.5 ,
as applicable, and designated in accordance with part 53 of this
chapter, or by an equivalent method designated in accordance with
part 53 of this chapter. Data handling and computation procedures to
be used in making comparisons between reported PM10 and
PM2.5 concentrations and the levels of the PM standards
are specified in the following sections.
(b) Data resulting from uncontrollable or natural events, for
example structural fires or high winds, may require special
consideration. In some cases, it may be appropriate to exclude these
data because they could result in inappropriate values to compare
with the levels of the PM standards. In other cases, it may be more
appropriate to retain the data for comparison with the level of the
PM standards and then allow the EPA to formulate the appropriate
regulatory response. Whether to exclude, retain, or make adjustments
to the data affected by uncontrollable or natural events is subject
to the approval of the appropriate Regional Administrator.
(c) The terms used in this appendix are defined as follows:
Average and mean refer to an arithmetic mean.
Daily value for PM refers to the 24-hour average concentration
of PM calculated or measured from midnight to midnight (local time)
for PM10 or PM2.5 .
Designated monitors are those monitoring sites designated in a
State PM Monitoring Network Description for spatial averaging in
areas opting for spatial averaging in accordance with part 58 of
this chapter.
98th percentile (used for PM2.5 ) means the
daily value out of a year of monitoring data below which 98 percent
of all values in the group fall.
[[Page 38756]]
99th percentile (used for PM10 ) means the
daily value out of a year of monitoring data below which 99 percent
of all values in the group fall.
Year refers to a calendar year.
(d) Sections 2.1 and 2.5 of this appendix contain data handling
instructions for the option of using a spatially averaged network of
monitors for the annual standard. If spatial averaging is not
considered for an area, then the spatial average is equivalent to
the annual average of a single site and is treated accordingly in
subsequent calculations. For example, paragraph (a)(3) of section
2.1 of this appendix could be eliminated since the spatial average
would be equivalent to the annual average.
2.0 Comparisons with the PM2.5 Standards.
2.1 Annual PM2.5 Standard.
(a) The annual PM2.5 standard is met when the 3-year
average of the spatially averaged annual means is less than or equal
to 15.0 g/m3. The 3-year average of the
spatially averaged annual means is determined by averaging quarterly
means at each monitor to obtain the annual mean PM2.5
concentrations at each monitor, then averaging across all designated
monitors, and finally averaging for 3 consecutive years. The steps
can be summarized as follows:
(1) Average 24-hour measurements to obtain quarterly means at
each monitor.
(2) Average quarterly means to obtain annual means at each
monitor.
(3) Average across designated monitoring sites to obtain an
annual spatial mean for an area (this can be one site in which case
the spatial mean is equal to the annual mean).
(4) Average 3 years of annual spatial means to obtain a 3-year
average of spatially averaged annual means.
(b) In the case of spatial averaging, 3 years of spatial
averages are required to demonstrate that the standard has been met.
Designated sites with less than 3 years of data shall be included in
spatial averages for those years that data completeness requirements
are met. For the annual PM2.5 standard, a year meets data
completeness requirements when at least 75 percent of the scheduled
sampling days for each quarter have valid data. However, years with
high concentrations and more than a minimal amount of data (at least
11 samples in each quarter) shall not be ignored just because they
are comprised of quarters with less than complete data. Thus, in
computing annual spatially averaged means, years containing quarters
with at least 11 samples but less than 75 percent data completeness
shall be included in the computation if the resulting spatially
averaged annual mean concentration (rounded according to the
conventions of section 2.3 of this appendix) is greater than the
level of the standard.
(c) Situations may arise in which there are compelling reasons
to retain years containing quarters which do not meet the data
completeness requirement of 75 percent or the minimum number of 11
samples. The use of less than complete data is subject to the
approval of the appropriate Regional Administrator.
(d) The equations for calculating the 3-year average annual mean
of the PM2.5 standard are given in section 2.5 of this
appendix.
2.2 24-Hour PM2.5 Standard.
(a) The 24-hour PM2.5 standard is met when the 3-year
average of the 98th percentile values at each monitoring
site is less than or equal to 65 g/m3. This
comparison shall be based on 3 consecutive, complete years of air
quality data. A year meets data completeness requirements when at
least 75 percent of the scheduled sampling days for each quarter
have valid data. However, years with high concentrations shall not
be ignored just because they are comprised of quarters with less
than complete data. Thus, in computing the 3-year average
98th percentile value, years containing quarters with
less than 75 percent data completeness shall be included in the
computation if the annual 98th percentile value (rounded
according to the conventions of section 2.3 of this appendix) is
greater than the level of the standard.
(b) Situations may arise in which there are compelling reasons
to retain years containing quarters which do not meet the data
completeness requirement. The use of less than complete data is
subject to the approval of the appropriate Regional Administrator.
(c) The equations for calculating the 3-year average of the
annual 98th percentile values is given in section 2.6 of
this appendix.
2.3 Rounding Conventions. For the purposes of comparing
calculated values to the applicable level of the standard, it is
necessary to round the final results of the calculations described
in sections 2.5 and 2.6 of this appendix. For the annual
PM2.5 standard, the 3-year average of the spatially
averaged annual means shall be rounded to the nearest 0.1
g/m3 (decimals 0.05 and greater are rounded up
to the next 0.1, and any decimal lower than 0.05 is rounded down to
the nearest 0.1). For the 24-hour PM2.5 standard, the 3-
year average of the annual 98th percentile values shall
be rounded to the nearest 1 g/m3 (decimals 0.5
and greater are rounded up to nearest whole number, and any decimal
lower than 0.5 is rounded down to the nearest whole number).
2.4 Monitoring Considerations.
(a) Section 58.13 of this chapter specifies the required minimum
frequency of sampling for PM2.5 . Exceptions to the
specified sampling frequencies, such as a reduced frequency during a
season of expected low concentrations, are subject to the approval
of the appropriate Regional Administrator. Section 58.14 of 40 CFR
part 58 and section 2.8 of Appendix D of 40 CFR part 58, specify
which monitors are eligible for making comparisons with the PM
standards. In determining a spatial mean using two or more
monitoring sites operating in a given year, the annual mean for an
individual site may be included in the spatial mean if and only if
the mean for that site meets the criterion specified in Sec. 2.8 of
Appendix D of 40 CFR part 58. In the event data from an otherwise
eligible site is excluded from being averaged with data from other
sites on the basis of this criterion, then the 3-year mean from that
site shall be compared directly to the annual standard.
(b) For the annual PM2.5 standard, when designated
monitors are located at the same site and are reporting
PM2.5 values for the same time periods, and when spatial
averaging has been chosen, their concentrations shall be averaged
before an area-wide spatial average is calculated. Such monitors
will then be considered as one monitor.
2.5 Equations for the Annual PM2.5 Standard.
(a) An annual mean value for PM2.5 is determined by
first averaging the daily values of a calendar quarter:
Equation 1
[GRAPHIC] [TIFF OMITTED] TR18JY97.000
where:
xq,y,s = the mean for quarter q of year y for site s;
nq = the number of monitored values in the quarter; and
xi,q,y,s = the ith value in quarter q for year
y for site s.
(b) The following equation is then to be used for calculation of
the annual mean:
Equation 2
[GRAPHIC] [TIFF OMITTED] TR18JY97.001
where:
xy,s = the annual mean concentration for year y (y = 1,
2, or 3) and for site s; and
xq,y,s = the mean for quarter q of year y for site s.
(c) (1) The spatially averaged annual mean for year y is
computed by first calculating the annual mean for each site
designated to be included in a spatial average, xy,s , and
then computing the average of these values across sites:
Equation 3
[GRAPHIC] [TIFF OMITTED] TR18JY97.002
where:
xy = the spatially averaged mean for year y;
xy,s = the annual mean for year y and site s; and
ns = the number of sites designated to be averaged.
(2) In the event that an area designated for spatial averaging
has two or more sites at the same location producing data for the
same time periods, the sites are averaged together before using
Equation 3 by:
Equation 4
[GRAPHIC] [TIFF OMITTED] TR18JY97.003
where:
xy,s* = the annual mean for year y for the sites at the
same location (which will now be considered one site);
[[Page 38757]]
nc = the number of sites at the same location designated
to be included in the spatial average; and
xy,s = the annual mean for year y and site s.
(d) The 3-year average of the spatially averaged annual means is
calculated by using the following equation:
Equation 5
[GRAPHIC] [TIFF OMITTED] TR18JY97.004
where:
x = the 3-year average of the spatially averaged annual means; and
xy = the spatially averaged annual mean for year y.
Example 1--Area Designated for Spatial Averaging That Meets the
Primary Annual PM2.5 Standard.
a. In an area designated for spatial averaging, four designated
monitors recorded data in at least 1 year of a particular 3-year
period. Using Equations 1 and 2, the annual means for
PM2.5 at each site are calculated for each year. The
following table can be created from the results. Data completeness
percentages for the quarter with the fewest number of samples are
also shown.
Table 1.--Results from Equations 1 and 2
--------------------------------------------------------------------------------------------------------------------------------------------------------
Site #1 Site #2 Site #3 Site #4 Spatial mean
--------------------------------------------------------------------------------------------------------------------------------------------------------
Year 1......................................... Annual mean (g/m\3\).... 12.7 ............ ............ ............ 12.7
% data completeness.............. 80 0 0 0 ............
Year 2......................................... Annual mean (g/m\3\).... 12.6 17.5 15.2 ............ 15.05
% data completeness.............. 90 63 38 0 ............
Year 3......................................... Annual mean (g/m\3\).... 12.5 18.5 14.1 16.9 15.50
% data completeness.............. 90 80 85 50 ............
3-year mean.................................... ................................. ............ ............ ............ ............ 14.42
--------------------------------------------------------------------------------------------------------------------------------------------------------
b. The data from these sites are averaged in the order described
in section 2.1 of this appendix. Note that the annual mean from site
#3 in year 2 and the annual mean from site #4 in year 3 do not meet
the 75 percent data completeness criteria. Assuming the 38 percent
data completeness represents a quarter with fewer than 11 samples,
site #3 in year 2 does not meet the minimum data completeness
requirement of 11 samples in each quarter. The site is therefore
excluded from the calculation of the spatial mean for year 2.
However, since the spatial mean for year 3 is above the level of the
standard and the minimum data requirement of 11 samples in each
quarter has been met, the annual mean from site #4 in year 3 is
included in the calculation of the spatial mean for year 3 and in
the calculation of the 3-year average. The 3-year average is rounded
to 14.4 g/m3, indicating that this area meets
the annual PM2.5 standard.
Example 2--Area With Two Monitors at the Same Location That Meets
the Primary Annual PM2.5 Standard.
a. In an area designated for spatial averaging, six designated
monitors, with two monitors at the same location (#5 and #6),
recorded data in a particular 3-year period. Using Equations 1 and
2, the annual means for PM2.5 are calculated for each
year. The following table can be created from the results.
Table 2.--Results From Equations 1 and 2
--------------------------------------------------------------------------------------------------------------------------------------------------------
Average of Spatial
Annual mean (g/m\3\) Site #1 Site #2 Site #3 Site #4 Site #5 Site #6 #5 and #6 mean
--------------------------------------------------------------------------------------------------------------------------------------------------------
Year 1............................................ 12.9 9.9 12.6 11.1 14.5 14.6 14.55 12.21
Year 2............................................ 14.5 13.3 12.2 10.9 16.1 16.0 16.05 13.39
Year 3............................................ 14.4 12.4 11.5 9.7 12.3 12.1 12.20 12.04
3-Year mean....................................... ........... ........... ........... ........... ........... ........... .......... 12.55
--------------------------------------------------------------------------------------------------------------------------------------------------------
b. The annual means for sites #5 and #6 are averaged together
using Equation 4 before the spatial average is calculated using
Equation 3 since they are in the same location. The 3-year mean is
rounded to 12.6 g/m3, indicating that this area
meets the annual PM2.5 standard.
Example 3--Area With a Single Monitor That Meets the Primary Annual
PM2.5 Standard.
a. Given data from a single monitor in an area, the calculations
are as follows. Using Equations 1 and 2, the annual means for
PM2.5 are calculated for each year. If the annual means
are 10.28, 17.38, and 12.25 g/m3, then the 3-
year mean is:
[GRAPHIC] [TIFF OMITTED] TR18JY97.005
b. This value is rounded to 13.3, indicating that this area
meets the annual PM2.5 standard.
2.6 Equations for the 24-Hour PM2.5 Standard.
(a) When the data for a particular site and year meet the data
completeness requirements in section 2.2 of this appendix,
calculation of the 98th percentile is accomplished by the
following steps. All the daily values from a particular site and
year comprise a series of values (x1 , x2 ,
x3 , ..., xn ), that can be sorted into a series
where each number is equal to or larger than the preceding number
(x[1] , x[2] , x[3] , ...,
x[n] ). In this case, x[1] is the smallest
number and x[n] is the largest value. The 98th
percentile is found from the sorted series of daily values which is
ordered from the lowest to the highest number. Compute (0.98) x
(n) as the number ``i.d'', where ``i'' is the integer part of the
result and ``d'' is the decimal part of the result. The
98th percentile value for year y, P0.98, y , is
given by Equation 6:
Equation 6
[GRAPHIC] [TIFF OMITTED] TR18JY97.006
where:
P0.98,y = 98th percentile for year y;
x[i+1] = the (i+1)th number in the ordered
series of numbers; and
i = the integer part of the product of 0.98 and n.
[[Page 38758]]
(b) The 3-year average 98th percentile is then
calculated by averaging the annual 98th percentiles:
Equation 7
[GRAPHIC] [TIFF OMITTED] TR18JY97.007
(c) The 3-year average 98th percentile is rounded
according to the conventions in section 2.3 of this appendix before
a comparison with the standard is made.
Example 4--Ambient Monitoring Site With Every-Day Sampling That
Meets the Primary 24-Hour PM2.5 Standard.
a. In each year of a particular 3 year period, varying numbers
of daily PM2.5 values (e.g., 281, 304, and 296) out of a
possible 365 values were recorded at a particular site with the
following ranked values (in g/m3):
Table 3.--Ordered Monitoring Data For 3 Years
----------------------------------------------------------------------------------------------------------------
Year 1 Year 2 Year 3
----------------------------------------------------------------------------------------------------------------
j rank Xj value j rank Xj value j rank Xj value
----------------------------------------------------------------------------------------------------------------
275.............. 57.9 296 54.3 290 66.0
276.............. 59.0 297 57.1 291 68.4
277.............. 62.2 298 63.0 292 69.8
----------------------------------------------------------------------------------------------------------------
b. Using Equation 6, the 98th percentile values for
each year are calculated as follows:
[GRAPHIC] [TIFF OMITTED] TR18JY97.008
[GRAPHIC] [TIFF OMITTED] TR18JY97.009
[GRAPHIC] [TIFF OMITTED] TR18JY97.010
c. 1. Using Equation 7, the 3-year average 98th
percentile is calculated as follows:
[GRAPHIC] [TIFF OMITTED] TR18JY97.011
2. Therefore, this site meets the 24-hour PM2.5
standard.
3.0 Comparisons with the PM10 Standards.
3.1 Annual PM10 Standard.
(a) The annual PM10 standard is met when the 3-year
average of the annual mean PM10 concentrations at each
monitoring site is less than or equal to 50 g/
m3. The 3-year average of the annual means is determined
by averaging quarterly means to obtain annual mean PM10
concentrations for 3 consecutive, complete years at each monitoring
site. The steps can be summarized as follows:
(1) Average 24-hour measurements to obtain a quarterly mean.
(2) Average quarterly means to obtain an annual mean.
(3) Average annual means to obtain a 3-year mean.
(b) For the annual PM10 standard, a year meets data
completeness requirements when at least 75 percent of the scheduled
sampling days for each quarter have valid data. However, years with
high concentrations and more than a minimal amount of data (at least
11 samples in each quarter) shall not be ignored just because they
are comprised of quarters with less than complete data. Thus, in
computing the 3-year average annual mean concentration, years
containing quarters with at least 11 samples but less than 75
percent data completeness shall be included in the computation if
the annual mean concentration (rounded according to the conventions
of section 2.3 of this appendix) is greater than the level of the
standard.
(c) Situations may arise in which there are compelling reasons
to retain years containing quarters which do not meet the data
completeness requirement of 75 percent or the minimum number of 11
samples. The use of less than complete data is subject to the
approval of the appropriate Regional Administrator.
(d) The equations for calculating the 3-year average annual mean
of the PM10 standard are given in section 3.5 of this
appendix.
3.2 24-Hour PM10 Standard.
(a) The 24-hour PM10 standard is met when the 3-year
average of the annual 99th percentile values at each
monitoring site is less than or equal to 150 g/
m3. This comparison shall be based on 3 consecutive,
complete years of air quality data. A year meets data completeness
requirements when at least 75 percent of the scheduled sampling days
for each quarter have valid data. However, years with high
concentrations shall not be ignored just because they are comprised
of quarters with less than complete data. Thus, in computing the 3-
year average of the annual 99th percentile values, years
containing quarters with less than 75 percent data completeness
shall be included in the computation if the annual 99th
percentile value (rounded according to the conventions of section
2.3 of this appendix) is greater than the level of the standard.
(b) Situations may arise in which there are compelling reasons
to retain years containing quarters which do not meet the data
completeness requirement. The use of less than complete data is
subject to the approval of the appropriate Regional Administrator.
(c) The equation for calculating the 3-year average of the
annual 99th percentile values is given in section 2.6 of
this appendix.
3.3 Rounding Conventions. For the annual PM10
standard, the 3-year average of the annual PM10 means
shall be rounded to the nearest 1 g/m3 (decimals
0.5 and greater are
[[Page 38759]]
rounded up to the next whole number, and any decimal less than 0.5
is rounded down to the nearest whole number). For the 24-hour
PM10 standard, the 3-year average of the annual
99th percentile values of PM10 shall be
rounded to the nearest 10 g/m3 (155 g/
m3 and greater would be rounded to 160 g/
m3 and 154 g/m3 and less would be
rounded to 150 g/m3).
3.4 Monitoring Considerations. Section 58.13 of this chapter
specifies the required minimum frequency of sampling for
PM10 . Exceptions to the specified sampling frequencies,
such as a reduced frequency during a season of expected low
concentrations, are subject to the approval of the appropriate
Regional Administrator. For making comparisons with the
PM10 NAAQS, all sites meeting applicable requirements in
part 58 of this chapter would be used.
3.5 Equations for the Annual PM10 Standard.
(a) An annual arithmetic mean value for PM10 is
determined by first averaging the 24-hour values of a calendar
quarter using the following equation:
Equation 8
[GRAPHIC] [TIFF OMITTED] TR18JY97.012
where:
xq,y = the mean for quarter q of year y;
nq = the number of monitored values in the quarter; and
xi,q,y = the ith value in quarter q for year
y.
(b) The following equation is then to be used for calculation of
the annual mean:
Equation 9
[GRAPHIC] [TIFF OMITTED] TR18JY97.013
where:
xy = the annual mean concentration for year y, (y=1, 2,
or 3); and
xq,y = the mean for a quarter q of year y.
(c) The 3-year average of the annual means is calculated by
using the following equation:
Equation 10
[GRAPHIC] [TIFF OMITTED] TR18JY97.014
where:
x = the 3-year average of the annual means; and
xy = the annual mean for calendar year y.
Example 5--Ambient Monitoring Site That Does Not Meet the Annual
PM10 Standard.
a. Given data from a PM10 monitor and using Equations
8 and 9, the annual means for PM10 are calculated for
each year. If the annual means are 52.42, 82.17, and 63.23
g/m3, then the 3-year average annual mean is:
[GRAPHIC] [TIFF OMITTED] TR18JY97.015
b. Therefore, this site does not meet the annual PM10
standard.
3.6 Equation for the 24-Hour PM10 Standard.
(a) When the data for a particular site and year meet the data
completeness requirements in section 3.2 of this appendix,
calculation of the 99th percentile is accomplished by the
following steps. All the daily values from a particular site and
year comprise a series of values (x1 , x2 ,
x3 , ..., xn ) that can be sorted into a series
where each number is equal to or larger than the preceding number
(x[1] , x[2] , x[3] , ...,
x[n] ). In this case, x[1] is the smallest
number and x[n] is the largest value. The 99th percentile
is found from the sorted series of daily values which is ordered
from the lowest to the highest number. Compute (0.99) x (n) as the
number ``i.d'', where ``i'' is the integer part of the result and
``d'' is the decimal part of the result. The 99th
percentile value for year y, P0.99,y , is given by
Equation 11:
Equation 11
[GRAPHIC] [TIFF OMITTED] TR18JY97.016
where:
P0.99,y = the 99th percentile for year y;
x[i+1] = the (i+1)th number in the ordered
series of numbers; and
i = the integer part of the product of 0.99 and n.
(b) The 3-year average 99th percentile value is then
calculated by averaging the annual 99th percentiles:
Equation 12
[GRAPHIC] [TIFF OMITTED] TR18JY97.017
(c) The 3-year average 99th percentile is rounded
according to the conventions in section 3.3 of this appendix before
a comparison with the standard is made.
Example 6--Ambient Monitoring Site With Sampling Every Sixth Day
That Meets the Primary 24-Hour PM10 Standard.
a. In each year of a particular 3 year period, varying numbers
of PM10 daily values (e.g., 110, 98, and 100) out of a
possible 121 daily values were recorded at a particular site with
the following ranked values (in g/m3):
Table 4.--Ordered Monitoring Data For 3 Years
----------------------------------------------------------------------------------------------------------------
Year 1 Year 2 Year 3
----------------------------------------------------------------------------------------------------------------
j rank Xj value j rank Xj value j rank Xj value
----------------------------------------------------------------------------------------------------------------
108.............. 120 96 143 98 140
109.............. 128 97 148 99 144
110.............. 130 98 150 100 147
----------------------------------------------------------------------------------------------------------------
b. Using Equation 11, the 99th percentile values for
each year are calculated as follows:
[GRAPHIC] [TIFF OMITTED] TR18JY97.018
[GRAPHIC] [TIFF OMITTED] TR18JY97.019
[[Page 38760]]
[GRAPHIC] [TIFF OMITTED] TR18JY97.020
c. 1. Using Equation 12, the 3-year average 99th
percentile is calculated as follows:
[GRAPHIC] [TIFF OMITTED] TR18JY97.021
2. Therefore, this site meets the 24-hour PM10
standard.
[FR Doc. 97-18577 Filed 7-17-97; 8:45 am]
BILLING CODE 6560-50-F
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