B-1 APPENDIX B

WEIGHT OF EVIDENCEB-2 

### SAN JOAQUIN VALLEY PM2.5 SUPPLEMENTAL ANALYSIS

1. INTRODUCTION

The State Implementation Plan or SIP serv es as a demonstration of attainment for the national ambient air quality standar ds (NAAQS or federal standards). The attainment demonstration comprises analyses used to determine the set of control measures needed to meet the N AAQS by the attainment year. These analyses typically include air quality m odeling, which generally guides the selection of the most effective pollut ants to control and the magnitude of needed emissions reductions. The Weight of Ev idence (WOE) analysis provides a set of complementary analyses that supplement the SIP-required modeling. These analyses can include consideration of measured air quality, emissions, and meteorological data, evaluat ion of other air quality in dicators, and additional air quality modeling.

A WOE approach looks at t he entirety of the informa tion at hand to provide a more informed basis for the attainment strategy. Because all methods have inherent strengths and weaknesses, examin ing an air quality problem in a variety of ways offsets the limitati ons and uncertainty that ar e inherent in air quality modeling. This approach also provi des a better understanding of the overall problem and the level and mix of emi ssions controls needed for attainment.

The United States Environmental Prot ection Agency (U.S. EPA) recognizes the importance of a comprehensive assessm ent of air quality data and modeling and encourages this type of broad assessment for all attainment demonstrations. In their modeling guidance, they further not e that the results of supplementary analyses may be used in a WOE determination to show that attainment is likely despite modeled results which may be inco nclusive (U.S. EPA 2007). Under the U.S. EPA guidance, future year modeled annual average design values that fall between 14.5 and 15.5 ug/m 3 should be accompanied by a WOE demonstration to determine whether attainment will occu r. This range in modeled design values reflects the uncertainty in predicting absolute PM2.5 concentrations that is inherent in air quality m odeling, and therefore rec ognizes that an improved assessment of attainment can be deriv ed from examining a broader set of analyses.

U.S. EPA recommends that three basic types of analyses be included to supplement the primary modeling analysis in the WOE approach:

1) analyses of trends in ambient air quality and emissions, 2) observational models and diagnostic analyses, and 3) additional modeling.

Each analysis is weighted based on its ability to quantitatively assess the ability of the proposed control measures to yi eld attainment. The scope of the WOEB-3 analysis is different for each nonattainment area. The level of detail appropriate for each area depends upon the complexity of the air quality problem, how far into the future the attainment deadlin e is, and the amount of data and modeling available. For example, less analysis is needed for an area t hat is projecting attainment near-term and by a wide marg in, and for which recent air quality trends have demonstrated significant progre ss, than for areas with more severe air quality challenges. The following sect ions present the WOE assessment for PM2.5 in the San Joaquin Valley Air Basi n for each of the ar eas outlined in the U.S. EPA guidance.

2. ASSESSMENT OF RECENT AIR QUALITY AND EMISSION TRENDS

a. Current Air Quality

According to U.S. EPA’s guidance, even though air quality models are regarded as the most appropriate tool to assess im pacts in emission changes, it is also possible to extrapolate futu re trends in PM2.5 based on measured historical trends of air quality and emissions. Strength of the ev idence produced by emissions and air quality trends is increas ed if an extensive monitoring network exists and if there is good correlati on between past emission reductions and current trends.

Along with the South Coast, the San Joaquin Valley Air Basin has one of the most severe PM2.5 problems in the nation and represents a considerable challenge in attaining the federal PM2. 5 standards. These standards consist of both a 24-hour standard of 65 ug/m 3 , and an annual average standard of 15 ug/m 3 . While the majority of monitors with complete data in the San Joaquin Valley still exceed the annual PM2.5 st andard, PM2.5 air quality has shown considerable improvement since 1999 when monitoring data for assessing compliance with the federal PM2.5 standard began. When the San Joaquin Valley was first designated nonattainment for the federal PM2.5 standards, the basin exceeded both the annual and the 24- hour PM2.5 standards. However, based on 2004-2006 data, the San Joaquin Va lley meets the federal 24-hour PM2.5 standard of 65 ug/m 3 throughout the basin. Thus attaining the annual standard is the primary challenge in this State Implementation Plan.

The San Joaquin Valley Air Basin is a lo wland area bordered by mountains to the east, west, and south. The mountains act as air flow barriers, with the resulting stagnant conditions favoring the accumulati on of emissions and pollutants. To the north, the Valley bor ders the Sacramento Valley and Delta lowland, which allows for some level of pollutant disper sion. As a result, PM2.5 concentrations are higher in the southern and central por tions of the Valley, where geography, emissions, and climate pose significant challenges to air quality progress. Chapter 3 and Appendix E of the Distric t Plan provide detailed information on the conceptual model of PM2.5 fo rmation in the Valley.B-4 Currently, eleven sites routinel y monitor PM2.5 in the Air Basin. Table 1 provides the 2006 annual standard design values an d the annual average values for 2004, 2005, and 2006 for each monitoring site with co mplete data. The design value is a statistic that is used to describe the air quality status of a given area relative to the level of the federal standard. The annual design values represent the average of the mean annual PM2.5 concent rations measured during the three year period. Table 2 provides t he 24-hour standard design value for each monitoring site with complete data and the yearly 98 th percentile value of the 24-hour concentrations measured in 2004, 2005, and 2006. The 24-hour design value represents the average of the yearly 98 th percentile of the 24-hour concentrations measured during the three year period. Attainment is reached when the design value is at or below the corresponding federal standard.

As shown in Table 1, current 2006 annual average design values (reflecting the 2004 through 2006 period) range from 12.9 ug/m 3 to 18.9 ug/m 3 . The San Joaquin Valley monitoring sites wit h the highest PM2.5 annual design values are located in the southern and centra l portions of the basin, including Bakersfield and Visalia. Monitors locat ed in the northern portion of the Valley, including Stockton, Modesto, and Merced have lower annual PM2.5 design values and attain the annual PM2.5 standard. As shown in bold in the table, the high site for the region is the Bakers field–Planz monitor with a PM2.5 design value of 18.9 ug/m 3

.

Table 1. PM2.5 Annual Average Values

Annual Average (ug/m 3 ) Monitor 2004 2005 2006 2006 3-year Annual Average

Design Value (ug/m 3 )
Clovis-N Villa Avenue 15.8 16.0 16.8 16.2 Bakersfield-410 E Planz Road 17.4 19.9 19.3 18.9 Bakersfield-5558 California Avenue 19.0 17.9 18.7 18.5

Bakersfield-Golden State Highway 18.1 18.9 18.6 18.5

Corcoran-Patterson Avenue 17.3 17.6 16.7 17.2
Fresno-1st Street 16.4 16.9 16.8 16.7 Fresno-Hamilton and Winery 17.0 16.9 17.6 17.2
Merced-2334 M Street 15.3 14.1 14.8 14.7
Modesto-14th Street 13.6 13.9 14.8 14.1
Stockton-Hazelton Street 13.2 12.5 13.1 12.9
Visalia-N Church Street 17.0 18.8 18.8 18.2B-5 Table 2. PM2.5 98th Percentile 24-hour Values

Annual 98 th Percentile (ug/m 3 ) Monitor 2004 2005 2006 2006 3-year Average of

98 th Percentile Design Value (ug/m 3 ) Clovis-N Villa Avenue 42.4 77.0 51.3 57 Bakersfield-410 E Planz Road 78.6 66.4 50.6 65* Bakersfield-5558 California Avenue 59.3 63.6 60.5 62

Bakersfield-Golden State Highway 53.8 74.9 64.4 64

Corcoran-Patterson Avenue 49.4 74.5 50.1 58
Fresno-1st Street 52.0 71.0 51.0 58 Fresno-Hamilton and Winery 49.4 71.2 55.0 59
Merced-2334 M Street 43.0 48.3 43.8 45
Modesto-14th Street 45.0 55.0 52.0 51
Stockton-Hazelton Street 36.0 44.0 42.0 41
Visalia-N Church Street 54.0 65.0 50.0 56

*The 24-hour standard is exceeded when the design value is over 65 ug/m 3

As previously mentioned, all monitors in the San Joaquin Valley currently attain the federal 24-hour PM2.5 st andard. As shown on Tabl e 2, 2006 24-hour PM2.5 design values (reflecting the 2004 th rough 2006 period) range from 41 ug/m 3 to 65 ug/m 3 . Monitoring sites with the highes t 24-hour PM2.5 design values are located in the southern portion of the Va lley, around Bakersfield. As shown in bold on the table, the high site for the r egion is Bakersfield-Planz with a 24-hour PM2.5 design value of 65 ug/m 3

.

b. Recent PM2.5 Mass Trends

Trends observed in the San Joaquin Valley show that considerable progress has occurred in the San Joaquin Valley over the last five years due to the ongoing emissions control program. As shown in Figure 1, 24-hour design values have decreased approximately 40 percent and, as discussed above, based on the 2004 through 2006 data, attain the federal standard at all sites in the Basin.B-6 Figure 1: Comparison of 2006 to 2001 PM2.5 24-hour Design Values

PM2.5 24-hour Design Value

0 20 40 60 80 100 120

Modesto-14th Street Fresno-1st Street Visalia BakersfieldGoldenConcentrations (ug/m3)

2001
2006

All San Joaquin Valley monitors with co mplete data also show a significant decrease in annual average design values (Figure 2). In 2001, all monitoring sites in the Basin had annual des ign values greater than 16 ug/m 3 , with the Visalia site at approximately one and a half times the level of the standard. By 2006, design values decreased throughout t he basin, and only those sites in the southern and central portions of the Valley are st ill greater than 16 ug/m 3

. Bakersfield–Planz is the current high site , with a design value which is 26 percent above the standard. The great est rate of progress has occurred in the northern and central basin. From 2001 through 2006, the Modesto site design value dropped 28 percent, from 19.7 ug/m 3 to 14.1 ug/m 3 , while the Visalia site design value dropped 26 percent from 24.7 ug/m 3 to 18.2 ug/m 3 . As a result, all monitoring sites in the northern portion of the Valley now attain the annual PM2.5 standard of 15 ug/m 3 . In contrast, the Bakersfield-Golden site dropped 22 percent from 23.6 ug/m 3 to 18.5 ug/m 3 and the Bakersfield-California site dropped 21 percent from 23.3 ug/m 3 to 18.5 ug/m 3 . This trend is further illustrated in Figure 3 whic h depicts maps of the s patial variations in annual average concentrations in 2001 as compared to 2006.B-7 Trends in 24-hour and annual average desig n values were further evaluated using the nonparametric statistical analysis test, known as the Theil test, that U. S. EPA uses in national air quality trend analysis 1 . This method tests for whether upward or downward trends are real (significant) or a chance product of year-to-year variation (not significant). Theil test results indicate the 2001 to 2006 downward trends in 24-hour and three-year annual average PM2.5 concentrations are statistically significant.

Figure 2: Trends in Annual Average PM2.5 Design Values

1 U.S. EPA , National Air Quality and Emissions Trends Report, Publication No. EPA 454/R-03-005, Office of Air Quality and Standa rds, Air Quality Stra tegies and Standards Division, Research Triangle Park, North Carolina. 2003. http://www.epa.gov/air/airtrends/aqtrnd03/ 

### Three Year Annual Average PM2.5 Design Values

0 5 10 15 20 25 30

2001 2002 2003 2004 2005 2006 YearConcentrations (ug/m3) Bakersfield-410 E Planz

Bakersfield-5558 California

Bakersfield-Golden

Modesto-14th Street

Stockton-Hazelton

Visalia-N Church

Fresno-1st StreetB-8 Figure 3: 2001 and 2006 Annual Average Values

The progress observed in both the annual and the 24-hour PM2.5 standards reflects the linkage between the two standards. The annual average is comprised of individual 24-hour samples which vary throughout the year. In the San Joaquin Valley, PM2.5 concentra tions exhibit a pronounced seasonal variation, with significantly higher mont hly average concentrations during the late fall and winter (November through January) . PM2.5 concentrations from April through September are generally below 15 ug/m 3 . Therefore 24-hour PM2.5 concentrations during the fall and winte r seasons strongly drive the annual average concentrations. During the la te fall and winter, stagnant air, cool temperatures, and high humidity can lead to a build-up of PM2.5 over a period of several days to weeks.

Analyses of the changes in the distri bution of the 24-hour concentrations between 2001-2003 and 2004- 2006 indicate that the decrease in both 24-hour and annual average concentrations is the re sult of the downward shift in the distribution of daily PM2.5 concentrations during the fall/winter period. This can be seen in the decrease in the monthl y average concentrations during the fall/winter months between 2001 and 2006 at Bakersfield-California and Fresno (Figures 4 and 5). PM2.5 (ug/m3) San Joaquin Valley Air Basin National PM2.5 Annual Average (2001)

Stockton

Modesto

Merced

Clovis Fresno-1st

Fresno-Hamilton Visalia

Corcoran

Bakersfield-Golden Bakersfield-California

Bakersfield-PlanzB-9 Figure 4: Changes in Seasonal Patte rn at the Bakersfield-California Monitoring Site

Figure 5: Changes in Seasonal Patte rn at the Fresno Monitoring SiteB-10 A comparison of the changes in t he frequency distribution of 24-hour concentrations over the last few year s provides another means of understanding progress. Data collected from 24-hour samples dur ing 1999-2001 at the Bakersfield site indicate that 6 percent of the samples had c oncentrations greater than 65 ug/m 3 (Figure 6). In comparison, du ring the 2004-2006 period, the number of samples with PM2.5 c oncentrations greater than 65 ug/m 3 fell to 1 percent. During both periods, 45 perc ent of the samples had concentrations above the level of the annua l PM2.5 standard of 15 ug/m 3

.

At the Fresno site data collected duri ng the 1999–2001 period indicate that approximately 8 percent of the samples had conc entrations greater than 65 ug/m 3 (Figure 7), while during the 2004- 2006 period, only 1 percent of the samples had concentrati ons greater than 65 ug/m 3 . In addition, during 1999-2001, 46 percent of the samples had co ncentrations above the level of the annual PM2.5 standard of 15 ug/m 3 , while during the 2004-2006 period, the number of samples with conc entrations greater than 15 ug/m 3 fell to 34 percent. This analysis, together with the analysi s of monthly average PM2.5 trends, further illustrate that progress to date in the annual average is primarily linked to reductions in peak concentrations from October through March.

Figure 6: PM2.5 Concentr ations at Bakersfield-Cal ifornia 1999-2001 versus 2004-2006B-11 Figure 7: PM2.5 Concentrations at Fresno 1999-2001 versus 2004-2006

c. Historical PM2.5 Mass Trends

The PM2.5 Federal Reference Method (FRM) network that is used for comparison to the federal standard wa s deployed in 1998 and 1999. However, PM2.5 data have been routi nely collected in the San Joaquin Valley Air Basin since the late 1980s using dichotomous samplers that were operated for research purposes. The PM2.5 dichotom ous data correlate very well with the FRM data (r=0.98), but are biased lower than the FRM by 12 percent, therefore an absolute comparison to the FRM can not be made. However, the relative changes in the dichotomous data do provide a longer-term context for assessing progress. Figure 8 depicts PM 2.5 concentrations at four sites. At all of these sites, the 3-year average concentrati ons decreased until 1998, then increased until 2000. At two of the three highest site s, Bakersfield and Visalia, the 3-year average concentrations decreased about 40 percent from 1990 to 1998 (the Bakersfield site trend has a gap from 1994 to 1996). PM2.5 concentrations at Bakersfield then increased 19 percent from 1998 to 2000. The dichotomous data record at the third high site, Fresno, started in 1992. From 1992 to 1998, PM2.5 concentrations decreased 21 percent, followed by a 12 percent increase from 1998 to 2000. PM2.5 concentrations at the low site, Stockton, decreased 40 percent from 1991 to 1998, followed by a 20 percent increase from 1998 to 2000. The period between 1999 and 2001 incl uded a number of adverse winter episodes which likely lead to higher annual averages during this period. However, overall concentrations declined 20 to 30 percent over the period fromB-12 1990 through 2001. Looking at dichot omous data and FRM data together therefore illustrates an overall lo ng-term improvement in PM2.5.

Figure 8: Trends in Three-Year Aver age PM2.5 Concentrations Measured with Dichotomous Samplers



### PM2.5 Dichot Three-Year Average Trend

0 5 10 15 20 25 30 35199019911992199319941995199619971998199920002001Concentrations (ug/m3)

Bakersfield*

Fresno-1st Street

Stockton

Visalia

d. Chemical Composition and Emissions Trends

Current Chemical Composition

Particulate matter (PM) consists of m any different chemical components. Investigating these different components and how they vary by site and season provides us with a better understanding of their complexity and responses to the emission control program. This mix of chemical components consists of both directly emitted PM such as geological material and elemental carbon (soot), known as primary PM, as well as PM formed in the atmosphere from the reactions of precursor gases, known as secondary PM. These precursor pollutants include nitrogen oxides (NOx), sulfur oxides (SOx), reactive organic gases (ROG), and ammonia. NOx, SO x, and ammonia combine to form secondary ammonium nitrate and sulfat e. ROG can form secondary organic carbon, as well as participate in the pr oduction of secondary ammonium nitrate.

In the San Joaquin Valley, chemical com ponents are routinely measured at four sites, Bakersfield, Fresno, Visalia, and Modesto. These sites represent urban areas in different portions in the air basin . The chemical composition of PM2.5, seasonal variability, and trends in thes e components at two of these sites,B-13 Fresno and Bakersfield are discussed below to provide further insight into the linkage between observed progress and ongoing emission reductions. The annual average PM2.5 chemical compos ition for Bakersfield and Fresno is shown in Figure 9. Ammonium ni trate and organic carbon are the major constituents at both sites. However, at Bakersfield, ammonium nitrate constitutes a higher percentage (39 per cent) of PM2.5 than organic carbon (35 percent), while the reverse (37 per cent ammonium nitr ate and 41 percent organic carbon) occurs in Fresno. Ammonium nitrate is formed in the atmosphere from chemical reactions of NOx emitted from motor vehicles and stationary combustion sources. Stagnant, cold, and damp conditions in the winter promote the formation and accumulati on of ammonium nitrate. Burning activities, such as residential wood co mbustion, cooking, and direct tailpipe emissions from mobile sources are major sources of organic carbon. Ammonium sulfate is also formed in the atmosphere from chemical reactions of SOx emitted from combustion sources. Ammonium sulfate constitutes about one tenth of ambient PM2.5 at both sites. Elemental car bon resulting from mobile and stationary combustion sources, and geolog ical material from roads and other dust producing activities also contribute to PM2.5 at both sites, but to a lesser extent.

Figure 9: 2004-2006 Average Chemi cal Composition of PM2.5 at Bakersfield and Fresno

Figures 10 and 11 illustrate the seasonal va riability in chemical components that make up PM2.5 for the Bakersfield and Fresno sites averaged over 2004 through 2006. As discussed previously, PM2.5 c oncentrations are highest during the fall and winter. These higher concentrations are driven by increases in ammonium 2004-2006 Average Composition Bakersfield

AmmNitrate 39%

AmmSulfate
13% OC
35% Geological
6% EC
5% Elements 2% 2004-2006 Average Composition Fresno

AmmNitrate 37%

AmmSulfate
11% OC
41% Geological
4% EC
5% Elements 2%B-14 nitrate and carbon. At the Bakersfield site (Figure 10), ammonium nitrate is highest during the fall and winter mont hs (November through January) and lowest from April through September. Ammonium nitrate concentrations at Fresno follow the same trend. Cold and humid conditions during the fall and winter favor the formation of ammonium ni trate in the atmosphere from chemical reactions of nitrogen oxides emitted fr om mobile and stationary combustion sources. At the Fresno site (Figure 11), organic carbon has a similar trend as that of ammonium nitrate. At the Bakersfield site, or ganic carbon is also highest during the fall and winter mont hs, but at this site organi c carbon levels start high in January, decrease until April and then incr ease almost linearly until reaching a maximum in December. Increased activi ty in residential wood combustion during the fall/winter period is one cause of higher organic carbon concentrations. At both locations, elemental carbon component remains fairly constant throughout the year, while the ammonium sulfate co mponent is more prevalent from May through September, and the geological co mponents from April through October.

Figure 10: Seasonal Variation in PM2.5 Chemical Components at BakersfieldB-15 Figure 11: Seasonal Variation in PM 2.5 Chemical Components at Fresno

Chemical Composition and Precursors Trends

As discussed previously, monitoring sites in the San Joaquin Valley have shown PM2.5 concentrations decreasing from 2001 to 2006. Trends in individual chemical components and precursor conc entrations, as well as emissions inventory trends were evaluated to understand the main chemical components responsible for this progress and to eval uate the response to our ongoing control program. Figures 12 and 13 il lustrate recent trends in PM2.5 concentrations and its individual chemical components at Fr esno and Bakersfield. Improvements in PM2.5 in the San Joaquin Valley can be mostly attributed to reductions in carbonaceous aerosols and ammonium ni trate. In Fresno, carbonaceous aerosols have dropped 37 percent, and am monium nitrate concentrations have dropped 24 percent. The overall impr ovement in PM2.5 mass observed in Fresno is therefore due in most part to reductions in carbonaceous aerosols (63 percent), with a smaller portion of the remaining PM2.5 improvement due to reductions in ammonium nitrate (24 perc ent). In Bakersfield, carbonaceous aerosols have dropped by 16 percent and ammonium nitrate concentrations dropped by 23 percent since 2002. Therefor e 41 percent of the overall reduction in PM2.5 mass is due to reductions in carbonaceous aerosols, while 59 percent is due to reductions in ammonium ni trate. Understandi ng the role of carbonaceous compounds in PM2.5 pollu tion, the San Joaquin Valley Air Pollution Control District made the Valley’ s Residential Wood Combustion Rule more stringent in 2003, which may have c ontributed to the observed decrease in carbonaceous aerosols.B-16 Figure 12: Trends in PM2.5 Mass and Chemical Components at Fresno

* The three-year design value is not considered valid.

Figure 13: Trends in PM2.5 M ass and Chemical Components at Bakersfield-California

Concentrations in ambient NO x, a precursor to nitric acid and ammonium nitrate decreased steadily from 2001 through 2006. Figures 3 -14 and 3 -15 illustrate theB-17 short-term trends in the Basin aver age NOx compared to ammonium nitrate concentrations in Fresno and Bakersfield. Ambient NOx concentrations in the Valley have shown a modest decrease of 15 percent. Ammonium nitrate concentrations were highest in 2002 at bot h sites, with a small decrease between 2001 and 2006 at Fresno of 7 percent.

While the short-term trends for ammoni um nitrate have been modest, longer-term records show concomitant decreases between ambient NOx and ammonium nitrate as well as between ambient SO 2 and ammonium sulf ate. Figure 16 shows trends in the basin three-year average ambient NOx concentrations and the corresponding ambient nitrate m easurements from the PM10 network extending back to the late 1980s. The h ills and valleys in the ammonium nitrate concentrations reflect the effects of the varying meteorology on ammonium nitrate formation. Since 1987, ambient NOx has decreased 50 percent while ammonium nitrate decreased by 35 percen t. Figure 17 shows the trends from 1987 to 1996 in the basin three-year average ambient SO2 concentrations and ammonium sulfate measurements from t he PM10 network. During this period SO2 decreased by 42 percent with a conc urrent decrease in PM10 sulfate of 39 percent.

Figure 14: PM2.5 Amm onium Nitrate Compared to NOx – FresnoB-18 Figure 15: PM2.5 Ammoni um Nitrate Compared to NOx - Bakersfield

Figure 16: Long-Term Trends in Three- Year Average Concentrations of PM10 Nitrate and NOx in San Joaquin Valley

Three-year Average Concentrations
of PM10 Nitrate and NO x in San Joaquin Valley

0 1 2 3 4 5 6 7 8 9 101987198819891990199119921993199419951996199719981999200020012002200320042005PM10 Nitrate (ug/m3)

0 1 2 3 4 5NOx(pphm)
NO3-

NOxB-19 Figure 17: Long-Term Trends in Three- Year Average Concentrations of PM10 Sulfate and NOx in the San Joaquin Valley

Three-year Average Concentrations of PM10 Sulfate
and SO 2 in the SJV

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.01987198819891990199119921993199419951996199719981999200020012002200320042005PM10 Sulfate (ug/m3)

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0SO2(pphm)
SO4--

SO2 SO2 monitoring discontinued
in 1997

Emission Trends

At the same time that ambient concent rations have been declining, the emissions of pollutants that contribute to the di fferent components of PM2.5 have been decreasing. Figure 18 illustrates the recent emission trends in the San Joaquin Valley air basin from 2001 through 2005. The greatest decrease in emissions occurred in ROG with a decrease of 33 t pd or 8 percent. NOx also decreased slightly, with a decline of 28 tpd, or 4 percent. Direct PM2.5 emissions showed a decrease of 7 tpd, or 7 percent, while SOx emissions did not change.

The combined downward trends in PM2.5 components, precursor concentrations, and emissions all indicate that over both in the short- and longterm the ongoing control progr am has had substantial be nefits in improving air quality and that similar em ission reductions in the future should provide continuing progress towards attain ing the federal PM2.5 standards.B-20 Figure 18: PM2.5 and PM2.5 Precursor Emission Trends in the San Joaquin Valley

Annual Emission Inventory Trends 2001-2005

0 100 200 300 400 500 600 700

2001 2002 2003 2004 2005Emissions (tpd) NOx
ROG
SOx
PM2.5

3. OBSERVATIONAL MODELS AND DIAGNOSTIC ANALYSES

Observational models take advantage of monitored data to draw conclusions about the relative importance of different types of emissions and precursors as factors contributing to obs erved PM2.5 concentrations. According to U.S. EPA guidance, observational m odels can be used to corroborate the effects of prior control strategies, as well as identi fy the potential effectiveness of proposed control approaches. U.S. EPA recomm ends using both source apportionment (receptor models) and indicator spec ies approaches. The two most widely applied receptor modeling ap proaches are multi-variat e statistical models such as positive matrix factorization (PMF ) and the chemical mass balance model (CMB). Receptor models are particula rly useful in identifying the source contributions to directly emitted PM. Th is section summarizes results from prior source apportionment studies as well as both PMF and CMB applied to recent data. In addition, previous work usi ng an indicator species approach to assess the limiting precursor in secondary nitrate formation in the San Joaquin Valley is discussed.B-21 a. Observational Models

Prior Source Apportionment Studies

The Chemical Mass Balance (CMB), and the Positive Matrix Factorization (PMF) and UNMIX (named for its function, which is to "unmix" the concentrations of chemical species measured in the ambi ent air to identify the contributing sources) multivariate receptor models have been applied to PM 2.5 data collected in the San Joaquin Valley. Chow, et al. 2 used the CMB sour ce apportionment model to estimate the contribution of sources to PM2.5 in Fresno during high PM2.5 days occurring from December 15, 2000 through February 3, 2001 illustrated in Figure 19. Secondary ammoni um nitrate is the most significant source, contributing 32 percent to t he measured PM2.5. Residential wood combustion constitutes 30 percent of PM 2.5. Vehicle emissions account for 13 percent of PM2.5, with similar contributions from gasoline (7 percent) and diesel (6 percent) fueled vehicles. C ooking accounts for 12 percent of PM2.5.

Figure 19: Source Contribution to PM2.5 Concentrations at Fresno Estimated Using the Chemical Mass Balance (CMB) Method

2 J .C. Chow, J. G. Watson, D. H. Lowenthal, L.-W. A. Chen, B. Zelinska, L. R. Rinehart, and K. L. Magliano: Evaluation of organic markers for chemical ma ss balance source apportionment at the Fresno Supersite, Atmospheric Chemis try and Physics Discussions, 6, 10341 – 10372, 2006 PM2.5 Source Contribution (CMB) in Percent Fresno - 2000/2001 Winter Average

Wood Burning

30% Ammonium Nitrate

32%

Ammonium Sulfate

2% Cooking
12% Vehicle Exhaust (Gasoline)
7% Unknown
11% Vehicle Exhaust (Diesel)

6%B-22 Chen, et al. 3 applied the PMF and UNMIX models to chemically speciated PM2.5 measurements from 23 sites operated in t he in the San Joaquin Valley during the 2000/2001 Central California PM Air Quality Study (CRPAQS) to estimate source contributions. Figure 20 ill ustrates the resulting s ource contribution throughout the Valley, estimated for the period w hen high PM2.5 concentrations occurred (November through January). PMF and UNM IX source contribution estimates are similar. Particles formed through c hemical reactions in the atmosphere, including ammonium nitrate and sec ondary organic compounds are the major contributors, accounting for 48 percent (P MF) and 51 percent (UNMIX) of PM2.5. Residential wood combustion follows, wit h a contribution of 23 percent (PMF) and 24 percent (UNMIX). Particles directly emitted from moto r vehicles account for 10 percent (PMF) and 15 per cent (UNMIX) of PM2.5. In addition, the zinc component resulting from the PMF analysis is thought to be related to brake and tire wear and contributes 9 percent to PM2.5.

Figure 20: Source Contribution to PM2.5 in the San Joaquin Valley Estimated Using the Positive Matrix Factorization (PMF) and the UNMIX Models

Recent Studies

To evaluate the major PM2.5 sources and th eir contributions in the San Joaquin Valley using recent data, two different source appor tionment techniques were applied to data collected in 2003 through 2006. The Chemical Mass Balance model (CMB) uses measured source pr ofiles and chemical speciation data in combination to determine source cont ributions. A fundam ental underlying assumption is that the source pr ofiles used as input are appropriate and

3 L.-W. A. Chen, J. G. Watson, J. C. Chow, and K. L. Magliano: Quantifying PM2.5 Source Contributions for the San Joaquin Valley with Mu ltivariate Receptor Models, submitted for publication, 2006. Source Contibution (PMF) in Percent San Joaquin Valley - 2000/2001 Winter Average

Motor Vehicle
10% Residential

Wood Combustion
23% Zinc
9% Cooking
3% Fugitive Dust
5% Ag-Dairy
2%

Ammonium Nitrate and Secondary

Organic

48% Source Contribution (UNMIX) in Percent San Joaquin Valley - 2000/2001 Winter Average

Motor Vehicle
15% Ag-Dairy
2% Fugitive Dust
3%

Residential

Wood Combustion
24% Ammonium Nitrate and Secondary

Organic

51% Cooking

5%B-23 representative for the region. In cont rast, PMF does not require the input of source profiles, but rather evaluates t he covariance of the chemical species to determine a set of factors, which are ty pically interpreted as source types. Source contributions are then calculated for each of the factors. Because the factors reflect species which vary in ti me in a similar manner, the factors may reflect the impacts of primary sources, as well the secondary species that have condensed on these primary particles. Since each technique has strengths and weaknesses, combined the two source apportionment techniques provide complementary results.

Positive Matrix Factorization

The PMF2 model was applied to chemical ly speciated PM2.5 data collected at the Fresno-First St. and Bakersfield-Califo rnia Ave. Speciation Trends Network (STN) monitoring sites from July 2 003 through December 2006. The average source contribution estimates illustrated in Figure 21 show ammonium nitrate is the major contributor to PM 2.5 at both sites (41 perc ent at Fresno and 45 percent at Bakersfield). Biomass smoke contri butes similar percentages at both sites (8 percent at Fresno, 7 per cent at Bakersfield) as does the total aged aerosol (10 percent at Fresno, 11 per cent at Bakersfield). The main differences in source contribution between the two sites include particles directly emitted from motor vehicles, which at Fresno acc ount for 23 percent of PM2.5, the 2 nd major component, while at Bakersfield account for 13 percent. Ammonium sulfate accounts for 10 percent of PM2.5 at Fresno and 14 percent at Bakersfield. Airborne soil is a minor contributor to PM2.5 at Fresno (3 percent), with a 9 percent contribution at Bakersfield.

Figure 21. Average Source Contri butions Estimated Using PMF2 (2003-2006)

July 2003 - Dec. 2006 Average Source Contribution in Fresno-1st Street

Airborne

soil 3% Secondary nitrate 41% Aged aerosol with sea

salt2 5%

Motor vehicle

23% Industrial 5%

Biomass smoke

8% Aged aerosol with sea

salt1 5%

Secondary Sulfate

10% July 2003 - Dec. 2006 Average Source Contribution in Bakersfield-California Ave.

Secondary

nitrate 45% Airborne

soil 9% Industrial 1% Aged aerosol with sea

salt2 7%

Motor vehicle

13% Aged aerosol with sea

salt1 4%

Biomass smoke

7%

Secondary Sulfate

14%B-24 Chemical Mass Balance Modeling

Annual average source contributions at Bakersfield-5558 California Avenue (BAC) and Fresno-1st Street (FSF) were also estimated by applying the Chemical Mass Balance (CMB 8.2) m odel to individual PM2.5 sample concentrations collected between Januar y 1, 2004 and December 31, 2006 and using source profiles for PM2.5 develo ped during previous studies. Source contribution estimates were calculat ed based on the 2004-2006 annual average of the individual samples. Figure 22 shows the calculated contributions to ambient fine particulate matter made by sources included in the model. Ammonium nitrate was the most signific ant source contributing 44% and 39% of the PM2.5 mass at Bakersfi eld and Fresno, respectively. Ammonium sulfate accounted for 12% at Bakersfield and 10% at Fresno. The motor vehicle exhaust (diesel and gasoline combined) contributi on was 9% at both si tes. Vegetative burning, which included residential wood combustion and agricultural and prescribed burning, contributed 9% and 14%, respectively, of the PM2.5 mass. The sea salt contribution was negligible at both sites. The ‘Other OC’, which represents contributions from secondary organic carb on, other unidentified primary sources, and the po ssible positive sampling arti facts of organic carbon, accounted for 20% to 23% of the PM2.5 mass.

Figure 22. CMB Model Calculat ed 2004-2005 Average PM2.5 Source Contributions.

BAC Modeled 2004-2006 Avg

Ammonium
Nitrate
45%

Ammonium

Sulfate

12% Sea Salt

0% Biomass Burning

9% Other OC

20% Airborne Soil
4% Tire/Brake
1%

Motor
Vehicle

9% FSF Modeled 2004-2006 Avg

Ammonium
Nitrate
39%

Ammonium

Sulfate

10% Sea Salt

0% Biomass Burning

14% Other OC

23% Airborne Soil
4%

Motor
Vehicle

9% Tire/Brake
1%B-25 While the specific contributions vary to some extent, taken together these sources apportionment studies highli ght the importance of secondary ammonium nitrate contributions to both the 24-hour and annual average concentrations. In addition, biomass bur ning and mobile sources were found to be significant contribut ors to primary PM2.5.

Diagnostic Analyses

Indicator Species Approach

As discussed in prior sections, trends in ammonium nitrate concentrations have tracked well with concurrent reductions in NOx, suggesting that NOx control is an effective approach for ensuri ng further reductions in a mmonium nitrate. An indicator species approach provides an add itional method to investigate which chemical precursor a secondary species such as ammonium nitrate is most responsive to control of. Ammonium nitrate is formed in the atmosphere through the reactions of precursor nitrogen oxides (NOx), reactive organic gases (ROG), and ammonia (NH3). The amount of each precursor in the atmosphere relative to each other determines how much ammoni um nitrate is formed. The chemistry is complex, but essentially the precursor in shortest supply will limit how much ammonium nitrate is produc ed. Reducing emissions of this limiting precursor provides the best opportunity to cut ammoni um nitrate levels. In simple terms, photochemical reactions of NOx and ROG fo rm nitric acid (HNO3). Nitric acid then reacts with ammonia (NH3) to form ammonium nitrate. Lurmann, et al. 4 compared ammonia and nitric acid ambient concentrations measured in the San Joaquin Valley during the win ter of 2000/2001, as part of CRPAQS. Figures 23 and 24 show the concentrations of nitric acid and ammonia measured at the rural Angiola site and at the urban Fresno site. At both sites ammonia concentrations are generally at least an order of m agnitude higher than the nitric acid concentrations. These ammonia-rich conditions throughout the Valley indicate that, during the winter, nitric acid is the limiting prec ursor.

4 F. W. Lurmann, S. G. Brown, M. C. McCa rthy, and P. T. Roberts: Processes Influencing Secondary Aerosol Formation in the San Joaquin Valley during Winter, Journal of Air and Waste Management Association, 56, 1679-1693, 2006.B-26 Figure 23: Comparison of Ammonia and Nitric Acid Concentrations Measured at Angiola during the Wi nter of 2000/2001 as Part of CRPAQS

Figure 24: Comparison of Ammonia and Nitric Acid Concentrations Measured at Fresno during the Wint er of 2000/2001 as Part of CRPAQS

Comparison of Ammonia and Nitric Acid Concentrations Fresno - Winter 2000/2001

-4 0 4 8 12 16 20

-2 0 2 4 6 8 HNO3 Concentration (ug-N/m 3 )NH3 Concentration (ug-N/m3)

1:1 Line Comparison of Ammonia and Nitric Acid Concentrations Angiola - Winter 2000/2001

-10

0 10 20 30 40 50 60

-2 0 2 4 6 8 10 12 14 16 18 HNO3 Concentration (ug-N/m3)NH3 Concentration (ug-N/m3)

1:1 LineB-27 4. AIR QUALITY MODELING

a. Rollback Modeling

In addition to the evaluation of air quality trends and the observational and diagnostic analyses, a rollback modeling analysis was conducted by the District to estimate the impacts of future emission reductions on resulting air quality. An extensive discussion of the rollback met hodology and the results are provided in Chapter 3 and associated spreadsheets of the District Plan. The rollback modeling showed that Fresno and Corc oran would attain the annual PM2.5 standard with baseline emission reductions in 2014. With the addition of the ARB and District proposed control strat egy, both Visalia and Bakersfield-Planz would attain in 2014 as well.

b. Grid-Based Modeling

As stipulated in the EPA Modeling Guidance, a grid-based photochemical model is necessary to perform the modeled attainment test for PM2.5 (EPA, 2007 5 ). Such models offer the best available r epresentation of important atmospheric processes and are an essential tool in analyzing the impacts of proposed emissions controls on pollutant c oncentrations. The EPA recommends guidelines for choosing a model for use in the attainment test. For example, the model source code should be free or lo w cost, modeling elements should have undergone rigorous scientific peer-review , and it should have been shown to perform well in the past for similar applications.

The Community Multiscale Air Qualit y Modeling System (CMAQ) has been selected for use in the PM 2.5 modeled attainment demonstration for the San Joaquin Valley Air Pollution Control District. CMAQ is a state-of-the-science “one-atmosphere” system t hat treats major atmospheric and land processes (e.g., advection, diffusion, gas phase c hemistry, gas-particle mass transfer, nucleation, coagulation, wet and dry depos ition, aqueous phase chemistry, etc.) and a range of species (e.g., anthr opogenic and biogenic, primary and secondary, gaseous and particulate) in a comprehensive framework (EPA, 1999 6 ; CMAS, 2007 7 ).

5 U.S. Environmental Protection Agency. ( 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. EPA-454/B-07-002

6 U.S. Environmental Protection Agency (199 9) Science Algorithms of the EPA Models-3 Community Multiscale Air Q uality (CMAQ) Modeling System

. EPA/600/R-99/030. http://www.epa.gov/asmdnerl/CMAQ/CMAQscienceDoc.html

7 Community Modeling and Analysis System ( 2007) CMAQ v4.6 Operational Guidance Document. http://www.cmaq-model.org/op_guidance_4.6/manual.pdfB-28 CMAQ was run for the year 2000 to provi de the basis for the model performance evaluation. It was during 2000 that t he California Regional PM10/PM2.5 Air Quality Study (CRPAQS) took place. The study resulted in a wealth of data with which to evaluate model performance. As it is necessary to execute simulations for a model reference year and a futu re year to perform the recommended modeled attainment demonstration, 2005 and 2014 were also simulated. Simulations for all years were driven by the meteorological inputs for 2000, while emissions varied from year to year.

Regional air quality modeling only represents a portion of the attainment test. In order to perform the EPA-recommended Spec iated Modeled Attainment Test, or SMAT, the relative response between t he modeled reference and future years must be considered in conjunction with obs ervations. This approach minimizes the uncertainties in predicting future year attainment that result from potential model bias in predicting absolut e species concentrations.

Federal Reference Method (FRM) PM2.5 mass measurem ents provide the basis for nonattainment designations. For this reason it is recomm ended that the FRM data also be used to project future air quality and progress towa rds attainment of the health-based National Ambient Air Q uality Standard (NAAQS) for PM2.5. However, given the complex physicochemical nature of PM2.5, it is necessary to consider individual species as well. While the FRM measurements give the mass of the bulk sample, a method for appor tioning this bulk mass to individual PM2.5 components is a first step towa rds determining the best targets for emissions controls in order to reach N AAQS levels in a timely manner. Given that (1) attainment status is cu rrently dependent upon FRM measurements and (2) concentrations of individual PM2.5 species need to be considered in order to understand the nature of and efficient ways to ameliora te the PM2.5 problem in a given region, a method has been developed to speciate bulk FRM PM2.5 mass with known FRM limitations in mind. This method is referred to as the measured S ulfate, A djusted N itrate, D erived W ater, I nferred C arbonaceous material and estimated acidity ( H +) approach or “SANDWICH” . SANDWICH is based on speciated measurements from other (often co-located) samplers, such as those from the Speciated Trends Network (STN), and the k nown sampling environment of the FRM. The approach serves to provide mass closure, reconciliation between speciated and bulk mass concent ration measurements, and the basis for a connection between observations, modeled PM2.5 concentrations, and the air quality standard.

The SMAT procedure was applied to FRM m onitors operating in the San Joaquin Valley with minimal deviations from U.S. EPA’s recommended procedure. The 2006 design value was used as a basis fr om which to project forward to estimated future year design values for the year 2014. Specia tion data for four STN (speciation) sites was used to specia te the FRM mass for all FRM sites. For those sites not collocated with STN m onitors, “surrogate” speciation sites were determined based on analysis of CRPAQS data to determine which sitesB-29 had similar speciation profiles. The com position was assumed to be the same at all three Bakersfield sites (BAC, BG S, and BEP). Similarly, the percent composition at the two Fresno sites (F SF and FSH) was assumed to be the same. In addition, Sto ckton (SOH), Clovis (CLO), Corcoran (COP), and Modesto (MRM), were assumed to have the same s peciation as one of the four speciation sites based on CRPAQS data analysis.

Quarterly average species concentrations were calculated at each STN site using the SANDWICH procedure. Modeled concentrations for the reference year (2005) and future year (2014) for each component were extracted for the FRM sites as a nine-cell average. The relati ve response factors were calculated for each component for each quarter. These calculations were performed using all modeled days, as we assumed that t he selected FRM measurements provided a stable quarterly average value.

These quarterly species percentages were then multiplied against the base year design value for 2006 (the average FRM PM2.5 concentrations for 2004, 2005, and 2006). The quarterly observed species concentrations were then multiplied by the RRFs and summed and averaged to get a future year PM2.5 design value at each FRM site. See Table 3 for the predicted baseline and controlled 2014 PM2.5 design values. For the “controll ed” 2014 emissions sensitivity scenario described above, future annual PM2.5 concent rations at all FRM sites are below the annual PM2.5 NAAQS of 15.0 μ g/m 3 , and, therefore, the San Joaquin Valley has passed the speciated modeled attain ment test for the annual PM2.5 NAAQS.

A similar procedure to the attainm ent demonstration fo r the annual PM2.5 standard was followed for the 24-hour PM2. 5 standard attainment demonstration. The exception was that only the top 25% of the measured and modeled days for each quarter were used instead of all avai lable days. The top 25% of the days are expected to be more representative of the 24-hour desi gn value than would all available days for a given quarter.

Table 4 shows the predicted 2014, 24-hour PM2.5 design va lues for the top five 2006 design value sites for the controlled emissions case. As shown, all sites in the SJV attained the 24-hour standard in 200 6, and further emissions controls do not cause any monitors to become non-attainment.B-30 Table 3. Reference and future year annual design values for SJV FRM sites

Site Code Speciation 2006 DV 2014 Baseline DV 2014 "Controlled" DV Bakersfield - 5558 California BAC BAC 18.51 15.86 14.28

Bakersfield - 410 E Planz Road BEP BAC 18.86 16.26 14.70

Bakersfield - Golden State BGS BAC 18.64 15.98 14.39

Clovis - N Villa Avenue CLO FSF 16.39 14.10 12.72

Corcoran - Patterson Avenue COP VCS 17.24 14.75 13.27

Fresno - 1st Street FSF FSF 16.68 14.43 13.01
Fresno - Hamilton and Winery FSH FSF 17.16 14.93 13.47

Merced - 2334 M Street MRM M14 14.69 12.85 11.76
Modesto - 14th Street M14 M14 14.10 12.52 11.44
Stockton - Hazelton Street SOH M14 12.93 11.77 10.87
Visalia - N. Church Street VCS VCS 18.20 16.05 14.47

Table 4. Reference and future year 24-hour design values for SJV FRM sites

Site Code Speciation 2006 DV 2014 "Controlled" DV Bakersfield - 5558 California BAC BAC 62.4 46.2

Bakersfield - 410 E Planz Road BEP BAC 65.2 45.9

Bakersfield - Golden State BGS BAC 64.4 45.3
Fresno - 1st Street FSF FSF 58.0 41.2
Fresno - Hamilton and Winery FSH FSF 58.5 41.7

5. SUMMARY

In summary, the San Joaquin Valley has experienced tremendous progress in reducing PM2.5 concentrations since initial monitoring began in 1990. Between 1990 and 1998, PM2.5 annual average concent rations dropped by approximately 40 percent throughout the Basin. Since 1999, when the offi cial regulatory monitoring program for comparison to the federal PM2.5 standard began, PM2.5 annual average concentrations have dropped a further 19 to 29 percent. While the peak annual average design value in the basin was 24.7 ug/m 3 in 2001, approximately one and a half times the leve l of the standard, it has dropped to 18.9 ug/m 3 in 2006. Currently, annual design values in the northern portion of the Valley are below the standard. In addition, based on 2004-2006 data, the San Joaquin Valley attains the f ederal 24-hour standard of 65 ug/m 3 . Although concentrations remain the highest in t he central and southern portions of theB-31 Valley, the rate of decrease in PM2. 5 in response to ongoing control programs has been significant.

Unlike ozone, PM2.5 consis ts of many different co mponents. Analysis of the trends in different components of PM2.5 has shown that over the last six years, decreases in carbonaceous aerosols and ammonium nitrate have had the greatest contribution to dec lining PM2.5 mass trends, with carbonaceous aerosol concentrations dropping by 16 to 37 percent and ammonium nitrate concentrations dropping by 23 to 24 percent. During this same time period, ambient NOx concentrations, a precursor to ammonium nitrate, decreased by 15 percent, while NOx emissions dropped by 4 percent. Looking back to the late 1980s, both ammonium nitrate and ammonium sulfate have declined significantly, along with concu rrent declines in ambient NO 2 and SO 2 concentrations and NOx and SOx emissions. These significant trends in declining PM2.5 concentrations, ambi ent precursor concentrations, and associated emissions all suggest that a continuing focus on further NOx reductions, as well as sources which contribute to carbonaceous aerosols will provide significant further progress in attaining the annual PM2.5 standard.

In order to estimate the impact of further emission reductions on future PM2.5 concentrations, both linear rollback and grid-based aerosol modeling were conducted. PM2.5 annual average c oncentrations in 2014 based on emission reductions achieved from both the ongoing control program, as well as new State and local measures, were estimated wit h both methods. Substantial further emission reductions for all key pollutant s will occur between 2005 and 2014.

Based on the grid-based modeling, seve ral sites in the District would be expected to attain the annual standar d in 2014 with baseline emission reductions. With the addition of the new State and local measures focusing on NOx, carbon, and directly-emitted combusti on emissions, the si tes with the most severe problems – Visalia and Bakersfiel d – would also attain in 2014 with a maximum predicted design value of 14.7 in Bakersfield. The linear rollback modeling showed similar re sults, providing a cons istent assessment of attainment prospects. It also appears that 2014 is the earliest feasible attainment date. This is due to consideration of t he following factors: 1) baseline emission reductions that occur during the peri od up to 2014 are not sufficient alone to provide for attainment at all sites, 2) the additional emission reductions that will result from the State Strategy will not phase in prior to 2014 due to the extraordinarily complex and innovative nature of developing and implementing these new measures, and 3) the San Joaquin Valley has experienced periods of slower air quality progre ss due to the influence of me teorology, suggesting that the full timeframe up to 2014 will be needed to ensure attainment.

Therefore, considering all of the informa tion available, the weight-of-evidence analyses provide a consistent assessment that the San Joaquin Valley will attainB-32 the annual average PM2.5 stand ard throughout the District in 2014. This is due to the following considerations:

 The significant progress that has already occurred, a 6 ug/m3 drop in annual average design value between 2001 and 2006, which represents two-thirds of the progress needed to attain the annual standard by 2014;

 The positive response of ammonium nitrate, ammonium sulfate, and carbon concentrations to past reduc tions in NOx, SOx, and primary PM2.5 emissions;

 The substantial future emission reductions that will occur due to both baseline commitments as well as new measures from NOx, and primary PM2.5 emissions t hat have worked in the past;

 Linear rollback modeling which indi cates attainment in 2014; and,

 Grid-based aerosol modeling which also indicates attainment in 2014 at all sites in the District.