TSD-5 

Baseline and Future PM2.5 Design Values in the New York City 

Metropolitan Non-Attainment Area 

Bureau of Air Quality Analysis and Research 

Division of Air Resources 

New York State Department of Environmental Conservation 

Albany, NY 12233 

December 14, 2007 
Introduction 

Baseline PM2.5 design values for a given area are based solely on measured 

Federal Reference Method (FRM) data, whereas air quality model-based results utilizing 

emissions from a target future year are needed to project PM2.5 design values to 

determine future attainment status of that area. The modeling guidance (USEPA, 2007a) 

states that the results from the regulatory applications of air quality models are not to be 

used in an absolute sense; rather, they are to be used to estimate the effects of changes in 

emissions on pollutant levels in a relative sense. For a single pollutant like ozone, the 

future design value at a given location is the product of the current observed value and 

the ratio of the future-to-current model predictions. The ratio of the future-to-current 

model prediction is also known as the relative response factor (RRF). Unlike ozone, 

PM2.5 is comprised of a variety of ions, trace elements, and carbon species. To 

demonstrate future attainment of air quality standards for PM2.5, one needs to project how 

each of the major species changes between the baseline and future model yeasr; that is, it 

is necessary to estimate speciated RRF values. In this report we present an overview of 

the calculation of the baseline PM2.5 design values and speciated RRFs for monitors in 

the 22-county New York City non-attainment area (NYC NAA), which when combined 

yield future year PM2.5 design values across the NYC NAA. 

Baseline PM2.5 design values

The first step in the modeled attainment test for the annual National Ambient Air 

Quality Standard (NAAQS) is to compute the baseline design values at each FRM site in 

the NYC NAA. The baseline design value is based on a five-year weighted average of 

observations from 2000-2004 to straddle the baseline emissions/modeling year of 2002 

(EPA, 2007a). This calculation is to be performed utilizing data on a quarterly basis. In 

other words, for each quarter the baseline concentration is the average of the 

concentrations from the corresponding quarters of the three year periods of 2000-2002, 

2001-2003, and 2002-2004. Table 1 lists the baseline design values, based on the EPA’s 

official quarterly averages (EPA, 2007b), at each FRM site across the NYC NAA having 

at least two years of sampling data during this five-year period. We note that one monitor 

– P.S. 59 (360610056) in New York County – had recorded one anomalously high 

average concentration of 25.2 μg m-3 during the third quarter of 2003. Examination of the 

data shows that for this quarter there were only five valid data points at the beginning of 

the quarter, and the monitor was subsequently shut down because of construction activity 

at the site. Because this short time period is not representative of air quality over the 

entire quarter, in this analysis this quarter was treated as missing, and this is reflected in 

Table 1. Attachment 1 provides a more detailed analysis of this particular issue. 

Current species concentrations

The next step in the modeled attainment test is to determine the current species 

composition at each FRM monitor, based on measured species data. The PM2.5 species 

composition is highly complex, but if the goal of air quality management decisions is to 

reduce PM2.5, it is necessary to know the dominant chemical species. Some of FRM 
monitors in the NYC NAA are collocated with Speciation Trends Network (STN) 

monitors that collect major ions, including sulfate (SO4), nitrate (NO3), and ammonium 

(NH4); carbon species, including elemental carbon (EC) and organic carbon (OC); and 

about 50 trace elements. At sites where both STN and FRM data are available, it is 

possible to relate the total FRM mass with the mass of individual species; however, 

during the 2000-2004 period, in the NYC NAA there were only two sites in CT, three in 

NJ, and four in NY that had collocated STN and FRM monitors. At those FRM sites that 

do not have collocated STN monitor, we assumed that the speciation data from the 

nearest STN monitor is sufficient to characterize the FRM site. Table 1 also lists the 

nearest STN site that is to be associated with the FTM site in the NYC NAA for 

computing the current species concentrations. 

It is known that FRM monitor filters do not retain semi-volatile species such as 

ammonium nitrate and some organics with high efficiency, particularly during the 

warmer months. Hence, one cannot simply add up the major species from the STN 

monitor and expect to relate this identically to the total mass from the FRM monitor. It is 

necessary to adjust some of the STN data to estimate the species composition of mass 

measured by the FRM monitor. According to the modeling guidance (USEPA, 2007a) 

the mass from the FRM monitor can be expressed as: 

PM2.5 = “retained nitrate mass” + “ammoniated sulfate mass” + “ammonium [Eq. 1] 

 associated with sulfate and retained nitrate” + “particle-bound water” 

 + “other primary PM2.5” + “blank mass” + “carbonaceous mass” 

where PM2.5 refers to the total mass measured at each FRM site; “retained nitrate mass” 

and “ammonium associated with sulfate and retained nitrate” refer only to the fractions of 

NO3 and NH4, respectively, that are not volatilized; “ammoniated sulfate mass” refers to 

the SO4 that is measured by the STN; “particle-bound water” refers to water that is 

associated with the hygroscopic ammonium sulfate and nitrate, and can be estimated as a 

polynomial function of retained ammonium, sulfate, and nitrate; “other primary PM2.5” 

refers to unspeciated, inert PM2.5 such as soil/crustal elements (here assumed to be the 

sum of major crustal oxides – Si, Ca, Fe, and Ti); “blank mass” refers to passively 

collected contamination, assumed to be 0.5 μg m-3; and “carbonaceous mass” refers to 

EC and an estimate of retained OC. Because of uncertainties in the measured OC, the 

modeling guidance suggests that organic mass be computed as the difference between the 

measured FRM mass and the sum of the other species listed above. 

 

 To compute the current species concentrations at each FRM site in the NYC 

NAA, we used the EPA’s official database of STN data (EPA, 2007b) covering the 

period 2002-2004. This database also includes the adjusted speciation data needed to 

compute the various retained species. For each quarter, the average species composition 

was computed; this was a simple arithmetic average, not a weighted average like the 

FRM mass. Table 2 lists the current species composition, as defined in Equation 1 above. 

Note that in the case of retained NH4, the actual measured data were not used here, due to 

uncertainties in its measurement. The modeling guidance suggests that NH4 can be 

estimated according to degree of neutralization (DON) of sulfate: 
NH4 = DON×SO4 + 0.29×NO3r [Eq. 2] 

Where NO3r refers to retained nitrate. As will be shown in a later section, using the DON 

– which also is included in the official EPA database – will allow the future NH4 value to 

depend only on SO4 and NO3, since reductions in emissions generally are targeting 

precursors of SO4 and NO3. The formulas for particle-bound water (PBW) and other 

primary PM2.5 (OPP) are listed in the modeling guidance (USEPA, 2007a). 

Relative Response Factors

 As stated in the Introduction, the air quality modeling results are to be used in a 

relative sense to compute future PM2.5 design values. For each species i, the future 

concentration of each species (CFi) is the product of the baseline concentration (CBi) and 

the corresponding RRFi: 

CFi = CBi×RRFi [Eq. 3] 

 As with the measured data to obtain current FRM mass and species composition, 

the model results are used on a quarterly basis. For each quarter and species, we 

computed the quarterly average concentration for the base and future year simulations. 

The RRF is the ratio of the quarterly average future-to-base year values. For this 

analysis, at each FRM site we considered the average of the surrounding nine grid cells 

and not just the grid cell that corresponds to that FRM site. 

 The RRF values for SO4, NO3r, OC, EC, and OPP were based on application of 

CMAQ model (TSD-2c, 2007) for 2002 and 2009. Table 3 lists the appropriate CMAQ 

variables that were used to estimate the speciated RRF values. For NH4, we used the 

future values of SO4 and NO3r to obtain the future year value, as per Equation 2. For 

PBW, we used the future year SO4, NO3r, and NH4 values and the polynomial 

formulation listed in the modeling guidance (USEPA, 2007a). Finally, the blank 

concentration of 0.5 μg m-3 is assumed to remain constant in the future year. 

Future PM2.5 design values

 Table 4 lists the baseline and future design values for the annual NAAQS at each 

FRM location in the NYC NAA. In 2009 all sites except for one – P.S. 59 (360610056) 

in New York County, NY – are projected to be in attainment of the NAAQS, since the 

future design values are below 14.5 μg m-3. The P.S. 59 site has a projected future 

concentration of 15.3 μg m-3, meaning that corroboratory analyses are needed for a 

weight of evidence (WOE) determination to demonstrate attainment at this monitor. It 

should be noted that on the average the design values across the NYC NAA were reduced 

by about 1.6 μg m-3, ranging from 1.2-2.2 μg m-3, in 2009 compared to baseline design 

values. Attachment 2 details the WOE analyses that support the assertion that the entire 

NYC NAA is projected to be in attainment of the PM2.5 NAAQS by 2009. 

 
References

United States Environmental Protection Agency (USEPA), 2007a. Guidance on the use 

of models and other analyses for demonstrating attainment of air quality goals for ozone, 

PM2.5, and regional haze. EPA-454/B-07-002, Research Triangle Park, NC. 

United States Environmental Protection Agency (USEPA), 2007b. Electronic mail 

correspondence from Kenneth Fradkin, EPA Region 2, on 17 August, 2007 contains two 

data files used here to demonstrate attainment of the annual PM2.5 NAAQS: Annualofficial-FRM-99-06-v1.zip (official quarterly average FRM mass) and STN-only-02-04-

R2.zip (daily speciation data). 

TSD-2c, 2007. PM2.5 modeling using the SMOKE/CMAQ system over the Ozone 

Transport Region (OTR) 
Table 1. Base year PM2.5 design values across the NYC NAA based on weighted 

averages over 2000-2004, and the nearest STN monitor to each FRM monitor. Base year 

design values listed in bold are above the annual NAAQS. 

FRM site Base year Design Value, μg m-3 Nearest STN monitor 

090010010 13.1 090019003 

090010113 12.6 090019003 

090011123 12.8 090019003 

090012124 12.9 090019003 

090013005 12.9 090019003 

090019003 11.8 090019003 

090091123 13.7 090091123 

090092123 13.1 090091123 

090099005 11.6 090091123 

340030003 13.7 360050110 

340171003 14.9 360610062 

340172002 16.0 360610062 

340210008 13.9 340230006 

340218001 11.9 340230006 

340230006 12.5 340230006 

340270004 12.4 340273001 

340273001 11.1 340273001 

340310005 13.2 360050083 

340390004 15.7 340390004 

340390006 13.5 340390004 

340392003 13.1 340390004 

360050080 15.8 360050110 

360050083 13.8 360050083 

360050110 14.7 360050110 

360470052 15.1 360610062 

360470076 14.2 360610062 

360470122 14.8 360610062 

360590008 12.2 360810124 

360610056 16.9 360610062 

360610062 16.3 360610062 

360610079 14.7 360050110 

360610128 15.9 360610062 

360710002 11.5 090019003 

360810124 13.3 360810124 

360850055 14.0 340390004 

360850067 12.1 340390004 

361030001 12.1 360810124 

361191002 12.3 360050083 
Table 2. Current species composition in μg m-3 across the NYC NAA, based on 

speciation data from the nearest STN monitor. “SO4” is sulfate; “NO3r” is retained 

nitrate; “OM” is organic mass; “PBW” is particle-bound water; “NH4” is ammonium 

associated with SO4 and NO3r; and “OPP” is other primary PM2.5, assumed to equal the 

sum of major crustal oxides (Si, Ca, Fe, and Ti). 

FRM site SO4 NO3r OM EC PBW NH4 OPP 

090010010 3.98 0.61 4.09 0.86 1.18 1.34 0.56 

090010113 3.81 0.61 3.93 0.83 1.14 1.29 0.53 

090011123 3.85 0.60 3.97 0.84 1.15 1.30 0.54 

090012124 3.90 0.59 4.02 0.85 1.16 1.31 0.55 

090013005 3.89 0.61 4.00 0.85 1.16 1.31 0.55 

090019003 3.56 0.52 3.73 0.76 1.06 1.18 0.50 

090091123 4.26 0.69 3.67 1.00 1.46 1.63 0.51 

090092123 4.05 0.68 3.52 0.96 1.38 1.55 0.49 

090099005 3.62 0.57 3.06 0.84 1.24 1.38 0.43 

340030003 4.10 0.95 3.32 1.04 1.37 1.70 0.66 

340171003 4.40 1.28 3.38 1.33 1.46 1.92 0.68 

340172002 4.71 1.41 3.59 1.43 1.56 2.07 0.73 

340210008 4.68 0.85 3.32 0.75 1.52 1.77 0.52 

340218001 4.01 0.68 2.86 0.63 1.30 1.50 0.44 

340230006 4.19 0.73 2.98 0.66 1.36 1.57 0.46 

340270004 4.52 0.62 2.91 0.45 1.44 1.59 0.36 

340273001 4.04 0.53 2.61 0.39 1.29 1.41 0.32 

340310005 3.80 0.82 3.49 1.26 1.26 1.50 0.61 

340390004 4.40 1.02 4.03 1.74 1.47 1.83 0.67 

340390006 3.76 0.91 3.46 1.50 1.25 1.58 0.57 

340392003 3.67 0.84 3.38 1.46 1.22 1.52 0.56 

360050080 4.73 1.17 3.84 1.23 1.57 1.99 0.77 

360050083 3.95 0.92 3.61 1.34 1.31 1.57 0.64 

360050110 4.39 1.08 3.56 1.14 1.46 1.84 0.71 

360470052 4.45 1.28 3.42 1.34 1.47 1.94 0.68 

360470076 4.20 1.22 3.20 1.26 1.39 1.83 0.64 

360470122 4.36 1.26 3.32 1.31 1.44 1.90 0.67 

360590008 3.85 0.82 2.97 0.69 1.29 1.55 0.55 

360610056 4.98 1.50 3.81 1.51 1.65 2.19 0.77 

360610062 4.81 1.40 3.66 1.45 1.59 2.10 0.74 

360610079 4.41 1.05 3.58 1.13 1.47 1.84 0.71 

360610128 4.68 1.39 3.59 1.42 1.55 2.05 0.72 

360710002 3.46 0.49 3.65 0.74 1.03 1.14 0.49 

360810124 4.22 0.92 3.24 0.75 1.41 1.70 0.60 

360850055 3.93 0.87 3.62 1.56 1.31 1.63 0.60 

360850067 3.39 0.75 3.10 1.34 1.13 1.40 0.51 

361030001 3.82 0.81 2.95 0.68 1.28 1.53 0.55 

361191002 3.52 0.78 3.23 1.18 1.17 1.39 0.57 
Table 3. Model variables from CMAQ used to compute speciated RRF values. 

PM2.5 species, μg m-3 CMAQ variables, μg m-3

SO4 ASO4I + ASO4J 

NO3r ANO3I + ANO3J 

OC 

AORGPAI + AORGPAJ 

+ AORGAI + AORGAJ 

+ AORGBI + AORGBJ 

EC AECI + AECJ 

OPP A25I + A25J 
Table 4. Base year and future (2009) PM2.5 design values across the NYC NAA. 

Concentrations listed in bold are above the annual NAAQS. 

FRM site Base Year Design Value 

μg m-3

Future PM2.5 Design Value 

μg m-3

090010010 13.1 11.5 

090010113 12.6 11.2 

090011123 12.8 11.2 

090012124 12.9 11.4 

090013005 12.9 11.3 

090019003 11.8 10.4 

090091123 13.7 11.7 

090092123 13.1 11.2 

090099005 11.6 9.9 

340030003 13.7 12.1 

340171003 14.9 13.3 

340172002 16.0 14.3 

340210008 13.9 11.8 

340218001 11.9 10.1 

340230006 12.5 10.4 

340270004 12.4 10.4 

340273001 11.1 9.3 

340310005 13.2 11.4 

340390004 15.7 13.5 

340390006 13.5 11.8 

340392003 13.1 11.4 

360050080 15.8 14.2 

360050083 13.8 12.4 

360050110 14.7 13.3 

360470052 15.1 13.6 

360470076 14.2 12.8 

360470122 14.8 13.3 

360590008 12.2 11.0 

360610056 16.9 15.3 

360610062 16.3 14.4 

360610079 14.7 13.3 

360610128 15.9 14.3 

360710002 11.5 10.3 

360810124 13.3 12.1 

360850055 14.0 12.3 

360850067 12.1 10.6 

361030001 12.1 10.7 

361191002 12.3 10.9 
 Attachment 1 

 

Analysis of the FRM data at PS 59 in New York (Manhattan) County, NY 

New York State DEC 

Division of Air Resources 

Background 

The New York State DEC analyzed the measurements of PM2.5 mass data across 

the New York City metropolitan non-attainment area for use in estimating the future 

design values, which are based on air quality modeling of the 2002 base and 2009 future 

years. The EPA Guidance (US EPA, 2007) requires the use of the measured data from 

the five-year period around the base year (2000-2004) to estimate the current design 

value (DVc). Although the Modeled Attainment Test Software (MATS) has not yet been 

released, the New York State DEC has been able to compute preliminary baseline and 

future PM2.5 levels, based on discussions with EPA/OAQPS. These preliminary 

calculations suggest that, except for one monitor – PS 59 [AQS ID 36-061-0056] in New 

York (Manhattan) County, NY – the region will be at or below the annual PM2.5

NAAQS. If the official FRM data received from OAQPS are used ‘as-is,’ PS 59 will be 

slightly above the prescribed level of the annual PM2.5 NAAQS. This is despite the fact 

that on average, PM2.5 levels have been decreasing at this site by nearly ~0.4-0.5 μg m-3

yr

-1 since 1999. In the following we investigate the cause for this dichotomy, and note 

that the measurements taken during the third quarter of 2003 play an important role in the 

estimated PM2.5 DVc and the potential future status of nonattainment at this location. 

PS 59 monitoring location 

The FRM unit is located on the roof of PS 59 in New York County and has been 

operational since 1999. Appendix A provides the location and description of the 

monitoring site. The FRM sampler was collocated with a duplicate sampler, as part of the 

network design requirements. Both monitors were shut down for most of the third quarter 

of 2003 due to roof repairs. Appendix B provides the correspondence from New York 

City School Construction Authority indicating the working hours of construction 

activities at the location with the requirement that the roof-main work to be completed by 

August 25, 2003. Ambient monitoring was resumed at this site in October 2003. So for 

the third quarter in 2003 there were only the first five samples out of a possible 31 were 

available. 

Duplicate Monitors and Analysis 

Appendix C describes the analysis associated with the primary and duplicate 

measurements, which shows that there is very good agreement between the two monitors, 

except for one outlier, which is found to be not associated with the period in question – 

3rd quarter of 2003. The estimated correlation coefficient (r2

=0.9867) and the almost zero 
intercept (0.0081) suggest either of the monitors could be used in the analysis. It should 

also be noted that from a monitoring perspective the site meets the criteria for data 

completeness in 2003 based on the remainder of the measurements. Yet, examination of 

the data on a quarterly average basis indicates that an average based on these five data 

points is not necessarily representative of air quality over the entire quarter at this 

location in addressing model-based attainment. The reason for examining the data by 

quarter arises from the modeling guidance (US EPA, 2007) that calls for a weighted fiveyear running quarterly average to compute baseline concentration levels. 

 In the following two sections we will present a case that a more appropriate 

quarterly concentration value be used for this quarter at this site, rather than one based on 

only the five values, in estimating the DVc. 

 

Observed PM2.5 mass in New York County, 2003 

Figure 1 displays the time series of PM2.5 mass at the four New York County 

FRM monitors in 2003 – PS 59 (360610056), Canal Street (360610062), JHS 45 

(360610079), and PS 19 (360610128). Each site tends to track the others rather well over 

the entire year. Considering only those days for which valid measurements are available 

for all four sites, there were a total of 64 days out of a possible 121 days which were used 

to estimate the annual arithmetic average at each site: PS 59, 17.11 μg m-3; Canal Street, 

15.69 μg m-3 JHS 45, 14.75 μg m-3 and PS 19, 16.18 μg m-3. These averages, not to be 

confused with the regulatory definition, indicate that in 2003 the PS 59 monitor is on 

avergae about 1 to 2 μg m-3 higher than the other sites. 

Figures 2a-d display the quarterly average concentrations covering the five year 

span of 2000 to 2004 for these four monitors. With the exception of the third quarter of 

2003 (Figure 2c) the quarterly average concentrations are quite comparable at these four 

monitors. As evident from Figure 2c however, the estimated quarterly average for PS 59 

is more than 8 μg m-3 higher than the other three sites, whose third quarter averages based 

on 20 to 29 samples were in the 16-17 μg m-3 range. 

Current and baseline PM2.5 levels at PS 59 

To compute baseline PM2.5 levels at this site, we started with the data file that was 

provided to the New York State DEC by Region 2 on August 17, 2007. The file labeled 

“Annual-official-FRM-99-06-v1.csv” lists the EPA’s official quarterly averages at each 

FRM site across the country for the period 1999-2006, as well as the corresponding 

attainment status and completion codes. 

 

Base year PM2.5 levels were computed three ways. The first method (method A) 

includes the FRM data from the anomalous third quarter of 2003. The other two methods 

involve data substitution; method B substitutes the third quarter average (16.70 μg m-3) 

from a nearby site (PS 19, ~3.5 km south of PS 59), while method C substitutes the 

average of the third quarter values from the other years (16.51 μg m-3; 2000-2002 and 

2004). The third quarter of 2003 at PS 19 and the average of the third quarters from the 
other years at PS 59 are considered complete for attainment/non-attainment purposes and 

are more likely to reflect the average air quality at or near this site. 

If method A is used the base DVc is 17.37 μg m-3, while the methods B and C 

result in a DVc of 16.90 μg m-3 and 16.89 μg m-3, respectively. Hence, if the ‘anomalous 

quarter’ from 2003 is used in this calculation (method A), the base year DVc is about 0.5 

μg m-3 higher than the other methods that used substitution. Preliminary calculations of 

the future 2009 design value are estimated to be about 15.7 μg m-3 using method A, and 

about 15.3 μg m-3 based on either method B or C.

Summary 

The above analysis has demonstrated that the use of quarterly average based on 

the measured data ‘as-is’ has significant consequences for PM2.5 non-attainment status at 

the PS 59 monitor. A quarterly average that covers only five days for the third quarter of 

2003 is not consistent with the measurements available at other monitor locations in New 

York County. It is recommended that this quarterly average be re-calculated using either 

the substitution of a third quarter concentration from a nearby monitor such as PS 19, or 

the substitution of the composite average of the third quarters from the other years at that 

monitor. 

Reference

US EPA, 2007. Guidance on the use of models and other analyses for demonstrating 

attainment of air quality goals for ozone, PM2.5, and regional haze. Office of Air Quality 

Planning and Standards, 253 pp., EPA-454/B-07-002. 
Figure 1. Time series of PM2.5 mass at the four FRM sites in New York County in 2003. 

Figure 1. New York County, NY - Entire year, 2003

0

10

20

30

40

50

60

1/1/2003 2/10/2003 3/22/2003 5/1/2003 6/10/2003 7/20/2003 8/29/2003 10/8/2003 11/17/2003 12/27/2003

PM2.5 mass

PS 59 Canal St JHS 45 PS 19
Figure 2. Comparison of quarterly averages at the four FRM monitors in New York 

County, 2000-2004. (a) Quarter #1, (b) Quarter #2, (c) Quarter #3, and (d) Quarter #4. 

Figure 2a. Qtr #1 averages, 2000-2004

0

3

6

9

12

15

18

21

24

27

2000 2001 2002 2003 2004

PM2.5 mass

PS 59 Canal St JHS 45 PS 19

Figure 2b. Qtr #2 averages, 2000-2004

0

3

6

9

12

15

18

21

24

27

2000 2001 2002 2003 2004

PM2.5 mass

PS 59 Canal St JHS 45 PS 19
Figure 2 (continued). 

Figure 2c. Qtr #3 averages, 2000-2004

0

3

6

9

12

15

18

21

24

27

2000 2001 2002 2003 2004

PM2.5 mass

PS 59 Canal St JHS 45 PS 19

Figure 2d. Qtr #4 averages, 2000-2004

0

3

6

9

12

15

18

21

24

27

2000 2001 2002 2003 2004

PM2.5 mass

PS 59 Canal St JHS 45 PS 19
Appendix A 

 

 Appendix B 


Appendix C 

Comparison of data from the primary and duplicate FRM monitors at PS 59 

• Both sites started in July 1999; the primary monitor continues to operate but the 

duplicate monitor was shut down at the end of 2005 

• Data were extracted from AQS on December 3, 2007 

• There are 644 days during this 6.5 year period with both sets of data available 

PS 59, 7/1999 - 12/2005

y = 0.9987x - 0.0081

R2

 = 0.9867

0

10

20

30

40

50

60

70

80

0 10 20 30 40 50 60 70 8

Primary FRM

Duplicate FRM

0

The overall arithmetic average at the primary monitor is 17.07 μg m-3, while at the 

duplicate monitor it is 17.04 μg m-3. The average difference (“primary-duplicate”) is 

0.03 μg m-3 and the standard deviation of the difference is 1.05 μg m-3. The central 95% 

of the differences between the two monitors ranges from -1.2 μg m-3 to +1.5 μg m-3. Of 

the 644 days, there appears to be only one day for which the two monitors differed 

substantially - January 31, 2001 with the primary and duplicate monitors reporting 14.1 

μg m-3, and 30.8 μg m-3, respectively. 

Two time periods of interest are considered to highlight the comparability between the 

two monitors -- July 6-9, 2002 period (very high values due to the Canadian wildfires), 

and the third quarter of 2003 (only the first five samples were available). On July 7, 2002 

– the only FRM sampling day during the wildfire period – the primary FRM recorded 

79.0 μg m-3, while the duplicate FRM recorded 79.8 μg m-3. Hence, even on this very 

high loading day the monitors were within 0.8 μg m-3 (1%) of each other. 

As per the 3rd quarter of 2003, the following plot displays the data for both monitors that 

were operational only for five sampling days. Recall that the monitors were shut down 
for the rest of the quarter. On each of these days the two monitors agree to within 0.2 μg 

m-3. The averages over these five days were 25.22 μg m-3 (primary) and 25.16 μg m-3

(duplicate). 

3rd Quarter, 2003 (July 2-14)

0

5

10

15

20

25

30

35

40

20030702 20030705 20030708 20030711 20030714

PM2.5

Primary Duplicate

 Attachment 2 
Weight of evidence (WOE) in support of modeled attainment of the PM2.5 NAAQS 

in the New York City non-attainment area 

 The EPA modeling guidance (US EPA, 2007), in conjunction with ambient 

Federal Reference Method (FRM) PM2.5 mass data from 2000-2004 and baseline and 

future air quality modeling results, has been applied to determine the attainment status of 

the New York City non-attainment area (NYC NAA) with respect to the annual National 

Ambient Air Quality Standard (NAAQS). The application of the EPA guidance for 

estimating the future design values based on the use of relative response factor (RRF) has 

resulted in one monitor – P.S. 59 (360610056), located in New York County, NY – to 

exceed the annual PM2.5 NAAQS level of 15 μg m-3. The estimated future PM2.5 design 

value at this monitor, based on this procedure, is 15.3μg m-3. This value falls within the 

uncertainty range of ±0.5 μg m-3 of the annual PM2.5 NAAQS, and supplemental analyses 

are needed for this monitor be considered to be in attainment. In the following sections 

we provide information to suggest that there is high degree of potential that estimated 

future design value will be below the annual NAAQS. 

Monitoring network in New York County and surroundings

 For most of the 2000-2004 period New York County, NY had 4 FRM monitors, 

but only one Speciation Trends Network (STN) monitor collocated with the FRM at the 

Canal Street site (360610062) to provide information on composition of the baseline 

PM2.5 species. Figure 1 displays the location of the four monitors as well as monitors in 

the surrounding counties. Table 1 lists the dates of operation of the FRM monitors in 

New York County; the base year design value for 2002, which is a weighted average of 

the measurements in the 2000 to 2004 period; and the nearest STN monitor. It should be 

noted that not all monitors in New York County were assigned the same STN monitor, 

because the approach selected was to use the nearest neighborhood monitor to link the 

FRM and STN. In the case of the J.H.S.45 (36061007) FRM monitor in New York 

County, the nearest STN monitor is the Bronx County I.S.52 site (360050110), and this 

site is also included in Table 1. 

 The current speciation levels estimated at these monitors are listed in Table 2. 

Only two of these sites – Canal Street and I.S.52 – have collocated STN monitors, while 

the species composition at the other FRM sites are only estimates based on the speciation 

data from a nearby monitor. Examination of the speciation data at Canal Street and I.S.52 

suggests that there may be fairly substantial gradients in PM2.5 species composition over 

the non-attainment area, on the order of several tenths of a μg m-3. Thus the estimates 

listed for the other monitors should only be considered approximate, and in some cases 

may not necessarily be representative of species composition at these monitors. This is 

certainly a limitation that needs to be taken into consideration when projecting the future 

design values using the model results and the current speciation levels. 

 

 Although the air quality modeling results are to be used in a relative sense, it is 

instructive to examine the changes in PM2.5 mass that the model predicts in an absolute 
sense to see the direct impacts of emissions reductions. We examined the CMAQpredicted average PM2.5 mass over the nine-grid cells that surround each of these FRM 

monitors (see Table 3) in the base (2002) and future (2009) years. Note that CMAQ 

predicts a consistent reduction of about 16% over each FRM monitor in New York 

County. Although not shown here, future PM2.5 concentrations at each FRM location 

across the 22-county NYC NAA are predicted by CMAQ to decrease by 12-18%. 

Estimate of future design values

 Table 4 lists the base year and projected future design values based on the EPA 

Guidance. The only monitor that is projected to be above 15μg m-3 in 2009 is P.S.59 

(360610056). In fact, none of the other monitors in the 22-county metropolitan nonattainment area is projected to exceed the lower end of the margin of safety range of 

14.5μg m-3. This suggests that on an overall basis the planned emissions reductions are 

projected to improve the PM2.5 air quality over the NYC NAA. 

 Noting that there is only one other monitor (360610062) that is above 16μg m-3

besides 360610056, and that it is collocated with STN providing an estimated future 

design value of 14.4μg m-3 that is below the annual PM2.5 NAAQS. If a simple linear 

extrapolation is used to compare these two monitors, then the projected future design 

value for P.S.59 would be 14.9μg m-3 and thus below the annual PM2.5 NAAQS. Also, 

the change estimated based on the guidance between 2009 and 2002 at 360610062 is 

1.9μg m-3, whereas at 360610056 the decrease is only 1.6μg m-3. 

 

Other data analysis

 A recent study by Qin et al. (2006) suggest that sum of sulfate and nitrate 

comprise about 40% or more of the PM2.5 mass in the NYC metropolitan area, and that 

70% or more of the PM2.5 measured in NYC results from transport into the region. Based 

on results from source apportionment modeling using Positive Matrix Factorization 

(PMF), the authors determined that the largest single source factor affecting NYC is 

“secondary sulfate” associated with SO2 emissions from upwind regions. It is clear that 

emission reductions in upwind states will be needed to further reduce PM2.5 in the NYC 

NAA. 

 In an earlier chapter (TSD-3a), we showed that PM2.5 levels appear to be 

decreasing across the NYC NAA. Although the data records for PM2.5 are somewhat 

short, we estimated that PM2.5 mass is decreasing by about 0.1-0.5μg m-3 yr

-1. At the 

P.S.59 site PM2.5 mass measurements are decreasing by about 0.3μg m-3 yr

-1 during 

1999-2006. In addition to PM2.5 mass, several criteria pollutants are also measured at the 

P.S.59 site. We examine the trends in SO2 and NO2 from 1993 to 2006 using the 

seasonal Kendall test, and found that ambient levels are declining at rates of 3.4% yr-1

and 1.7% yr-1, respectively. This again points to the potential that this area would be 

meeting the annual NAAQS, given that there are various measures under consideration 

that are aimed at decreasing the emissions of PM2.5 precursors. 
Summary

In summary, the above analysis shows that, based upon the EPA guidance only one 

monitor in the New York PM2.5 nonattainment area falls slightly above the level of the 

annual NAAQS, but still within the framework of uncertainty. The analysis suggests that 

lack of collocated speciation monitors and use of speciation information from the nearest 

neighborhood monitor may have contributed to the estimate of PM2.5 being above the 

level of NAAQS at the P.S.59 monitor. Examining the trends in precursors as well as 

measured PM2.5 at P.S.59 suggests a downward path and that coupled with the 

observation that the contribution to the secondary species is from upwind regions rather 

than local, favors strongly that this monitor will also be in attainment similar to the rest of 

them in the region. Analysis based on the only other monitor (360610062) with similar 

PM2.5 concentrations is projected to be below the level of the annual NAAQS, suggests 

that P.S.59 (360610056) would also be similarly be below the level of the annual 

NAAQS. 

 

Reference

Qin, Y., Kim., E., Hopke, P. K., 2006. The concentrations and sources of PM2.5 in 

metropolitan New York City. Atmospheric Environment 40, S312-S332. 

TSD-3a (2007) Analysis of Ambient PM2.5 Mass and Speciation for the New York 

metropolitan area through 2006. NYSDEC, Division of Air Resources, Albany, NY 

12233. 

United States Environmental Protection Agency (US EPA), 2007. Guidance on the use of 

models and other analyses for demonstrating attainment of air quality goals for ozone, 

PM2.5, and regional haze. Office of Air Quality Planning and Standards, 253 pp., EPA454/B-07-002. 
Table 1. Information for the five FRM monitors considered in this analysis: site name 

and ID, dates of operation during 2000-2004, base year PM2.5 design value, and the 

nearest STN monitor. 

Site 

Name 

FRM site Operational periods 

during 2000-2004 

Base year Design 

Value, μg m-3

Nearest STN 

monitor 

P.S.59 360610056 1st qtr 2000 – 4th qtr 2004 16.9 360610062 

Canal St 360610062 1st qtr 2000 – 4th qtr 2004 16.3 360610062 

J.H.S.45 360610079 1st qtr 2000 – 4th qtr 2004 14.7 360050110 

P.S.19 360610128 3rd qtr 2001 – 4th qtr 2004 15.9 360610062 

I.S.52 360050110 1st qtr 2000 – 4th qtr 2004 14.7 360050110 

Table 2. Current PM2.5 species composition at each site: sulfate (SO4), retained nitrate 

(NO3r), organic carbon (OC), elemental carbon (EC), particle-bound water (PBW), 

retained ammonium (NH4), and other primary PM2.5 (OPP). 

FRM site SO4 NO3r OC EC PBW NH4 OPP 

360610056 4.98 1.50 3.81 1.51 1.65 2.19 0.77 

360610062* 4.81 1.40 3.66 1.45 1.59 2.10 0.74 

360610079 4.41 1.05 3.58 1.13 1.47 1.84 0.71 

360610128 4.68 1.39 3.59 1.42 1.55 2.05 0.72 

360050110* 4.39 1.08 3.56 1.14 1.46 1.84 0.71 

* FRM Monitor with collocated STN 

Table 3. Annual average PM2.5 mass over the nine grid cells surrounding each monitor 

from the base year (2002) and future year (2009) CMAQ simulations, as well as the 

absolute and percent reductions. 

FRM site 2002 avg., 

μg m-3

2009 avg., 

μg m-3

Change (μg 

m-3) 

Change 

(%) 

360610056 24.28 20.51 -3.77 -15.5 

360610062 23.70 19.80 -3.90 -16.5 

360610079 24.28 20.51 -3.77 -15.5 

360610128 23.66 20.01 -3.65 -15.4 

360050110 24.28 20.51 -3.77 -15.5 
Table 4. Base and future year PM2.5 design values. 

FRM site Base Year Design Value, 

μg m-3

Future PM2.5 Design Value, 

μg m-3

360610056 16.9 15.3 

360610062 16.3 14.4 

360610079 14.7 13.3 

360610128 15.9 14.3 

360050110 14.7 13.3 

Figure 1.