## TSD-5

Baseline and Future PM 2.5 

## 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, 2007Introduction

Baseline PM 2.5 design values for a given area are based solely on measured Federal Reference Method (FRM) data, whereas air quality model-base d results utilizing emissions from a target future year are needed to project PM 2.5 design values to determine future attainment status of that area. The modeling guidance (USEPA, 2007a) states that the results from the regulatory app lications 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 se nse. For a single pollutant like ozone, the future design value at a given location is th e product of the current observed value and the ratio of the future-to-current model predic tions. The ratio of the future-to-current model prediction is also known as the rela tive response factor (RRF). Unlike ozone, PM 2.5 is comprised of a variety of ions, trace elements, and carbon species. To demonstrate future attainment of air quality standards for PM 2.5 , 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 PM 2.5 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 PM 2.5 design values acr oss the NYC NAA.

Baseline PM 2.5 design values

The first step in the modeled attainment test for the annual National Ambient Air Quality Standard (NAAQS) is to compute the ba seline 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 perf ormed utilizing data on a quarterly basis. In other words, for each quarter the baselin e concentration is the average of the concentrations from the corresponding quart ers of the three y ear periods of 2000-2002, 2001-2003, and 2002-2004. Table 1 lists the base line 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 th is 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 μ g m -3 during the third quarter of 2003. Examination of the data shows that for this quarter there were only five valid data poi nts 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 mi ssing, and this is reflected in Table 1. Attachment 1 provides a more detail ed 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 PM 2.5 species composition is highly complex, but if the goal of air quality management decisions is to reduce PM 2.5 , it is necessary to know the dominan t chemical species. Some of FRMmonitors in the NYC NAA are collocated with Speciation Tr ends Network (STN) monitors that collect majo r ions, including sulfate (SO 4 ), nitrate (NO 3 ), and ammonium (NH 4 ); carbon species, including elemental car bon (EC) and organic carbon (OC); and about 50 trace elements. At sites where bot h 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 th e NYC NAA there were only two sites in CT, three in NJ, and four in NY that had collocated STN a nd FRM monitors. At those FRM sites that do not have collocated STN monitor, we a ssumed that the speciation data from the nearest STN monitor is sufficient to characte rize the FRM site. Table 1 also lists the nearest STN site that is to be associat ed 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, part icularly 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. Accordi ng to the modeling guidance (USEPA, 2007a) the mass from the FRM monitor can be expressed as:

PM 2.5 = “retained nitrate mass” + “ammoniated su lfate mass” + “ammonium [Eq. 1] associated with sulfate and retained nitrat e” + “particle-bound water” + “other primary PM 2.5 ” + “blank mass” + “carbonaceous mass”

where PM 2.5 refers to the total mass measured at each FRM site; “retained nitrate mass” and “ammonium associated with sulfate and reta ined nitrate” refer onl y to the fractions of NO 3 and NH 4 , respectively, that are not volatilized ; “ammoniated sulfate mass” refers to the SO 4 that is measured by the STN; “particl e-bound water” refers to water that is associated with the hygroscopic ammonium sulf ate and nitrate, and can be estimated as a polynomial function of retained ammonium, su lfate, and nitrate; “other primary PM 2.5 ” refers to unspeciated, inert PM 2.5 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 μ g 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 speci es listed above.

To compute the current species concen trations at each FRM site in the NYC NAA, we used the EPA’s official databa se 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 NH 4 , the actual measured data were not used here, due to uncertainties in its measurement. The modeling guidance suggests that NH 4 can be estimated according to degree of neutralization (DON) of sulfate:NH 4 = DON×SO 4 + 0.29×NO 3 r [Eq. 2]

Where NO 3 r 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 NH 4 value to depend only on SO 4 and NO 3 , since reductions in emissi ons generally are targeting precursors of SO 4 and NO 3 . The formulas for particle-bound water (PBW) and other primary PM 2.5 (OPP) are listed in the modeling guidance (USEPA, 2007a).

Relative Response Factors

As stated in the Introducti on, the air quality modeling resu lts are to be used in a relative sense to compute future PM 2.5 design values. For each species i , the future concentration of each species (CF i ) is the product of the ba seline concentration (CB i ) and the corresponding RRF i :

CF i = CB i ×RRF i [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 averag e future-to-base year values. For this analysis, at each FRM site we considered th e average of the surrounding nine grid cells and not just the grid cell that corresponds to that FRM site.

The RRF values for SO 4 , NO 3 r, 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 estimat e the speciated RRF values. For NH 4 , we used the future values of SO 4 and NO 3 r to obtain the future year value, as per Equation 2. For PBW, we used the future year SO 4 , NO 3 r, and NH 4 values and the polynomial formulation listed in the modeling guid ance (USEPA, 2007a). Finally, the blank concentration of 0.5 μ g m -3 is assumed to remain constant in the future year.

Future PM 2.5 design values

Table 4 lists the baseline and future de sign values for the annual NAAQS at each FRM location in the NYC NAA. In 2009 a ll 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 μ g m -3 . The P.S. 59 site has a projected future concentration of 15.3 μ g m -3 , meaning that corroboratory analyses are needed for a weight of evidence (WOE) determ ination to demonstrate attainme nt at this monitor. It should be noted that on the average the desi gn values across the NYC NAA were reduced by about 1.6 μ g m -3 , ranging from 1.2-2.2 μ g 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 PM 2.5 NAAQS by 2009.References

United States Environmental Protection Ag ency (USEPA), 2007a. Guidance on the use of models and other analyses for demonstrating attainment of air quality goals for ozone, PM 2.5 , 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 demons trate attainment of the annual PM 2.5 NAAQS: Annualofficial-FRM-99-06-v1.zip (official quart erly average FRM mass) and STN-only-02-04- R2.zip (daily speciation data).

TSD-2c, 2007. PM 2.5 modeling using the SMOKE/CMAQ system over the Ozone Transport Region (OTR)Table 1. Base year PM 2.5 design values across the NYC NAA based on weighted averages over 2000-2004, and the nearest STN monitor to each FRM mo nitor. Base year design values listed in bold are above the annual NAAQS.

FRM site Base year Design Value, μ g 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 360050083Table 2. Current species composition in μ g m -3 across the NYC NAA, based on speciation data from the nearest STN monitor. “SO 4 ” is sulfate; “NO 3 r” is retained nitrate; “OM” is organic mass; “PBW” is particle-bound water; “NH 4 ” is ammonium associated with SO 4 and NO 3 r; and “OPP” is other primary PM 2.5 , assumed to equal the sum of major crustal oxides (Si, Ca, Fe, and Ti).

FRM site SO 4 NO 3 r OM EC PBW NH 4 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 0.57Table 3. Model variables from CMAQ used to compute speciated RRF values.

PM 2.5 species, μ g m -3 CMAQ variables, μ g m -3

SO 4 ASO4I + ASO4J NO 3 r ANO3I + ANO3J

OC AORGPAI + AORGPAJ + AORGAI + AORGAJ + AORGBI + AORGBJ EC AECI + AECJ OPP A25I + A25JTable 4. Base year and future (2009) PM 2.5 design values across the NYC NAA. Concentrations listed in bold are above the annual NAAQS.

FRM site Base Year Design Value

μ g m -3 Future PM 2.5 Design Value

μ g 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 10.9Attachment 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 PM 2.5 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) requ ires 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 PM 2.5 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 PM 2.5 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 PM 2.5 NAAQS. This is despite the fact that on average, PM 2.5 levels have been decreasing at this site by nearly ~0.4-0.5 μ g m -3

yr -1 since 1999. In the following we investig ate the cause for this dichotomy, and note that the measurements taken during the third qua rter of 2003 play an important role in the estimated PM 2.5 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 de scription of the monitoring site. The FRM sampler was collocated with a duplicate sampler, as part of the network design requirements. Both monitors we re shut down for most of the third quarter of 2003 due to roof repairs. Appendix B pr ovides the correspondence from New York City School Construction Au thority indicating the work ing 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 we re only the first five samples out of a possible 31 were available.

Duplicate Monitors and Analysis

Appendix C describes the analysis asso ciated with the primary and duplicate measurements, which shows that there is ve ry good agreement between the two monitors, except for one outlier, which is found to be not associated with the period in question – 3 rd quarter of 2003. The estimated correlation coefficient (r 2 =0.9867) and the almost zerointercept (0.0081) suggest either of the monitors could be used in the analysis. It should also be noted that from a monitoring perspe ctive 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 aver age based on these five data points is not necessarily representative of air quality over the entire quarter at this location in addressing model-based attainme nt. The reason for examining the data by quarter arises from the mode ling guidance (US EPA, 2007) that calls for a weighted fiveyear running quarterly average to co mpute baseline concentration levels.

In the following two sections we will pr esent a case that a more appropriate quarterly concentration value be used for this quarter at this site, ra ther than one based on only the five values, in estimating the DVc.

Observed PM 2.5 mass in New York County, 2003

Figure 1 displays the time series of PM 2.5 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 po ssible 121 days which were used to estimate the annual arithmetic average at each site: PS 59, 17.11 μ g m -3 ; Canal Street, 15.69 μ g m -3 JHS 45, 14.75 μ g m -3 and PS 19, 16.18 μ g m -3 . These averages, not to be confused with the regulatory definition, i ndicate that in 2003 the PS 59 monitor is on avergae about 1 to 2 μ g m -3 higher than the other sites.

Figures 2a-d display the qua rterly 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 μ g m -3 higher than the other three sites, whose third quarter averages based on 20 to 29 samples were in the 16-17 μ g m -3 range.

Current and baseline PM 2.5 levels at PS 59

To compute baseline PM 2.5 levels at this site, we starte d with the data file that was provided to the New York State DEC by Re gion 2 on August 17, 2007. The file labeled “Annual-official-FRM-99-06-v1.csv” lists the EPA’s official qua rterly averages at each FRM site across the country for the pe riod 1999-2006, as well as the corresponding attainment status and completion codes.

Base year PM 2.5 levels were computed three ways. The first method (method A) includes the FRM data from the anomalous th ird quarter of 2003. The other two methods involve data substitution; method B s ubstitutes the third quarter average (16.70 μ g 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 μ g m -3 ; 2000-2002 and 2004). The third quarter of 2003 at PS 19 and th e average of the third quarters from theother 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 μ g m -3 , while the methods B and C result in a DVc of 16.90 μ g m -3 and 16.89 μ g m -3 , respectively. Hence, if the ‘anomalous quarter’ from 2003 is used in this calculati on (method A), the base year DVc is about 0.5

μ g 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 μ g m -3 using method A, and about 15.3 μ g 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 PM 2.5 non-attainment status at the PS 59 monitor. A quarterly average that c overs only five days fo r 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 quart erly average be re-cal culated using either the substitution of a third quart er concentration from a near by 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, PM 2.5 , and regional haze. Office of Air Quality Planning and Standards, 253 pp., EPA-454/B-07-002.Figure 1. Time series of PM 2.5 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 12/27/2003PM2.5 mass

PS 59 Canal St JHS 45 PS 19Figure 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 2004PM2.5 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 2004PM2.5 mass

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

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

0 3 6 9 12 15 18 21 24 27

2000 2001 2002 2003 2004PM2.5 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 2004PM2.5 mass

PS 59 Canal St JHS 45 PS 19Appendix AAppendix BAppendix C

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

• Both sites started in July 1999; the prim ary monitor continues to operate but the duplicate monitor was shut down at the end of 2005

• Data were extracted fr om 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

R 2 = 0.9867

0 10 20 30 40 50 60 70 80

0 10 20 30 40 50 60 70 8 Primary FRMDuplicate FRM

0

The overall arithmetic average at the primary monitor is 17.07 μ g m -3 , while at the duplicate monitor it is 17.04 μ g m -3 . The average difference (“primary-duplicate”) is 0.03 μ g m -3 and the standard deviati on of the difference is 1.05 μ g m -3 . The central 95% of the differences between the tw o monitors ranges from -1.2 μ g m -3 to +1.5 μ g 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

μ g m -3 , and 30.8 μ g 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 fi ve samples were available). On July 7, 2002 – the only FRM sampling day during the wild fire period – the primary FRM recorded 79.0 μ g m -3 , while the duplicate FRM recorded 79.8 μ g m -3 . Hence, even on this very high loading day the monitors were within 0.8 μ g m -3 (1%) of each other.

As per the 3 rd quarter of 2003, the following plot disp lays the data for both monitors that were operational only for five sampling days. Recall that the monitors were shut downfor the rest of the quarter. On each of thes e days the two monitors agree to within 0.2 μ g

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

3rd Quarter, 2003 (July 2-14)

0 5 10 15 20 25 30 35 40

20030702 20030705 20030708 20030711 20030714PM2.5

Primary Duplicate

Attachment 2Weight of evidence (WOE) in support of modeled attainment of the PM 2.5 NAAQS in the New York City non-attainment area

The EPA modeling guidance (US EPA, 2007), in conjunction with ambient Federal Reference Method (FRM) PM 2.5 mass data from 2000- 2004 and baseline and future air quality modeling results, has been ap plied 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 th e 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 PM 2.5 NAAQS level of 15 μ g m -3 . The estimated future PM 2.5 design value at this monitor, base d on this procedure, is 15.3 μ g m -3 . This value falls within the uncertainty range of ±0.5 μ g m -3 of the annual PM 2.5 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 ther e 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 PM 2.5 species. Figure 1 displays th e 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 valu e for 2002, which is a weighted average of the measurements in the 2000 to 2004 period; an d 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 us e 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 Br onx 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 – Cana l Street and I.S.52 – have collocated STN monitors, while the species composition at the other FRM site s are only estimates based on the speciation data from a nearby monitor. Examination of th e speciation data at Ca nal Street and I.S.52 suggests that there may be fair ly substantial gradients in PM 2.5 species composition over the non-attainment area, on the or der of several tenths of a μ g 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 speci es composition at these monitors. This is certainly a limitation that needs to be taken in to consideration when projecting the future design values using the model results and the current speciation levels.

Although the air quality modeli ng results are to be used in a relative sense, it is instructive to examine the changes in PM 2.5 mass that the model predicts in an absolutesense to see the direct impacts of emi ssions reductions. We examined the CMAQpredicted average PM 2.5 mass over the nine-grid cells that surround each of these FRM monitors (see Table 3) in th e 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 PM 2.5 concentrations at each FRM location across the 22-county NYC NAA are predic ted by CMAQ to decrease by 12-18%.

Estimate of future design values

Table 4 lists the base year and projec ted future design values based on the EPA Guidance. The only monitor that is projected to be above 15 μ g m -3 in 2009 is P.S.59 (360610056). In fact, none of the other m onitors in the 22-county metropolitan nonattainment area is projected to exceed the lo wer end of the margin of safety range of 14.5 μ g m -3 . This suggests that on an overall ba sis the planned emissions reductions are projected to improve the PM 2.5 air quality over the NYC NAA.

Noting that there is only one othe r monitor (360610062) that is above 16 μ g m -3 besides 360610056, and that it is collocated with STN providing an estimated future design value of 14.4 μ g m -3 that is below the annual PM 2.5 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 14.9 μ g m -3 and thus below the annual PM 2.5 NAAQS. Also, the change estimated based on the gu idance between 2009 and 2002 at 360610062 is 1.9 μ g m -3 , whereas at 360610056 the decrease is only 1.6 μ g m -3

.

Other data analysis

A recent study by Qin et al. (2006) sugge st that sum of sulfate and nitrate comprise about 40% or more of the PM 2.5 mass in the NYC metropolitan area, and that 70% or more of the PM 2.5 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 larg est single source fact or affecting NYC is “secondary sulfate” a ssociated with SO 2 emissions from upwind regi ons. It is clear that emission reductions in upwind states will be needed to further reduce PM 2.5 in the NYC NAA.

In an earlier chapter (T SD-3a), we showed that PM 2.5 levels appear to be decreasing across the NYC NAA. Although the data records for PM 2.5 are somewhat short, we estimated that PM 2.5 mass is decreasing by about 0.1-0.5 μ g m -3 yr -1 . At the P.S.59 site PM 2.5 mass measurements ar e decreasing by about 0.3 μ g m -3 yr -1 during 1999-2006. In addition to PM 2.5 mass, several criteria polluta nts are also measured at the P.S.59 site. We examine the trends in SO 2 and NO 2 from 1993 to 2006 using the seasonal Kendall test, and found that ambient levels are de clining 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 PM 2.5 precursors.Summary

In summary, the above analysis shows that, based upon the EPA guidance only one monitor in the New York PM 2.5 nonattainment area falls sligh tly above the level of the annual NAAQS, but still within the framework of uncertainty. The analysis suggests that lack of collocated speciation monitors and us e of speciation informa tion from the nearest neighborhood monitor may have cont ributed to the estimate of PM 2.5 being above the level of NAAQS at the P.S.59 monitor. Examini ng the trends in precursors as well as measured PM 2.5 at P.S.59 suggests a downward pa th and that coupled with the observation that the contributi on 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 PM 2.5 concentrations is projecte d to be below the level of the annual NAAQS, suggests that P.S.59 (360610056) would also be simila rly be below the level of the annual NAAQS.

Reference

Qin, Y., Kim., E., Hopke, P. K., 2006. Th e concentrations and sources of PM 2.5 in metropolitan New York City. Atmospheric Environment 40, S312-S332.

TSD-3a (2007) Analysis of Ambient PM 2.5 Mass and Speciation for the New York metropolitan area through 2006. NYSDEC, Division of Air Resources, Albany, NY 12233.

United States Environmental Protection Agen cy (US EPA), 2007. Guidance on the use of models and other analyses for demonstrating attainment of air quality goals for ozone, PM 2.5 , and regional haze. Office of Air Qu ality 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 PM 2.5 design value, and the nearest STN monitor.

Site Name FRM site Operational periods during 2000-2004 Base year Design Value, μ g m -3 Nearest STN monitor P.S.59 360610056 1 st qtr 2000 – 4 th qtr 2004 16.9 360610062 Canal St 360610062 1 st qtr 2000 – 4 th qtr 2004 16.3 360610062 J.H.S.45 360610079 1 st qtr 2000 – 4 th qtr 2004 14.7 360050110 P.S.19 360610128 3 rd qtr 2001 – 4 th qtr 2004 15.9 360610062 I.S.52 360050110 1 st qtr 2000 – 4 th qtr 2004 14.7 360050110

Table 2. Current PM 2.5 species composition at each site: sulfate (SO 4 ), retained nitrate (NO 3 r), organic carbon (OC), elemental carbon (EC), particle-bound water (PBW), retained ammonium (NH 4 ), and other primary PM 2.5 (OPP).

FRM site SO 4 NO 3 r OC EC PBW NH 4 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 PM 2.5 mass over the nine grid cells surrounding each monitor from the base year (2002) and future y ear (2009) CMAQ simulations, as well as the absolute and percent reductions.

FRM site 2002 avg.,

μ g m -3 2009 avg.,

μ g m -3 Change ( μ g

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 -15.5Table 4. Base and future year PM 2.5 design values.

FRM site Base Year Design Value,

μ g m -3 Future PM 2.5 Design Value,

μ g 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.