# Chapter 2

PM2.5	Challenges	and	Trends	in	the	San	Joaquin Valley

2015 Plan for the 1997 PM2.5 Standard SJVUAPCDSan Joaquin Valley Unified Air Polluti on Control District April 16, 2015

Chapter 2: PM2.5 Challenges and Trends in the San Joaquin Valley 2015 Plan for the 1997 PM2.5 Standard This page intentionally blank.San Joaquin Valley Unified Air Polluti on Control District April 16, 2015

2-1 Chapter 2: PM2.5 Challenges and Trends in the San Joaquin Valley 2015 Plan for the 1997 PM2.5 Standard 

### Chapter 2: PM2.5 Challenges and Trends in the San Joaquin Valle y

Despite the unique geographical and meteorological challenges, the San Joaquin Valley (Valley) has made significant pr ogress in reducing total emissi ons of directly emitted emissions of particulate matter that is 2.5 microns or less in diameter (PM2.5) and PM2.5 precursor emissions and in improving air quality for Vall ey residents. Through progressively more stringent regul ations, improved control tech nologies, and innovative non-regulatory measures such as incentive programs, the annual average amount of directly emitted PM2.5 emissions has been steadily decreasing. Similarly, the overall amount of oxides of nitrogen (NOx ) and oxides of sulfur (SOx) e missions continue to decrease.

Achieving PM2.5 reductions has been challenging given frequent meteorological conditions conducive to PM2.5 fo rmation that are characteristic of the Valley, and which are outside human (and regulatory) control. Annual fluctuation s in weather patterns affect the Valley’s carrying c apacity (the ability to disperse pollutants), which is reflected in long and short-term ambien t air quality trends. Until the e xceptional weather conditions experienced due to th e recent drought, the Valley wa s on track to attain the 1997 annual PM2.5 standard before the federally mandated deadli ne of December 2014.

2.1 CHALLENGES OF THE NATURAL ENVIRONMENT

The Valley’s natural environm ent supports one of the most produ ctive agricultural regions in the country: the Sie rra Nevada provides the necessar y water for growing the abundance of crops, and a temperat e climate provides a long gro wing season. However, these same natural fact ors present significant challen ges for air quality: the surrounding mountains trap polluti on and block air flow, and th e mild climate keeps pollutant-scouring wi nds at bay most of the year. Despite the challenges, the San Joaquin Valley Air Poll ution Control District (District) and th e Valley are making progress in attaining the national ambi ent air quality standards (NAAQS) and improving public health for Valley citizens.

2.1.1 Unique Climate and Geography

The challenge of PM2.5 NAAQS atta inment in the Valley is ground ed in the unique topographical and meteorological conditions found in the region . The Valley, as seen in Figure 2-1, is an inter-mountain valley encompassing nearly 25, 000 square miles. Surrounded by mountain ranges to the west, east, and south, the air flow through the Valley can be blocked, leading to severely constrained dispersi on. During the winter, high-pressure systems can cause the atmosphere to become stagna nt for longer periods of time, where wind flow i s calm and air movement is mi nimal. These stagnant weather systems can also cause se vere nighttime temperature inv ersions, which exacerbate the build-up of PM2.5 and related precursors both be neath and above the evening inversion layer.San Joaquin Valley Unified Air Polluti on Control District April 16, 2015

2-2 Chapter 2: PM2.5 Challenges and Trends in the San Joaquin Valley 2015 Plan for the 1997 PM2.5 Standard Figure 2-1 San Joaquin Valley Air Basin

Under normal conditions, temperat ure decreases with increasing altitude, but during temperature inversions the norma l temperature gradient is rever sed, with temperatures increasing with altitude, causing warmer ai r to be above cooler air. Figu re 2-2 shows that this reversal of the “norma l” pattern impedes the upward f low of air, causes poor dispersion, and traps pollutants near the earth’s surface. Tem perature inversions are common in the Valley throughout the year. Since the inversion is often lower than the height of the surrounding mountain ranges, the Valley effective ly becomes a bowl capped with a lid that traps emi ssions near the surface. When horizontal dispersion (transport flow) and vertical d ispersion (rising air) are minim ized, PM2.5 concentrations can build quickly, especially in the winter. These naturally o ccurring meteorological conditions have the net effect o f spatially concentrating direc t PM2.5 concentrations near their sources; promoting t he formation and regional buildu p of secondary species, particularly ammonium nitrate ; and chemically aged organic carb on species, resulting in an increase in their relative to xicity. Given these challenges , the Valley needs even more effective emissions reducti ons to attain the PM2.5 NAAQS; and the District continues to pursue these reduc tions through its numerous air q uality attainment plans, prohibitory regulatory control st rategy and innovative non-regu latory emission reduction strategy, which includes a robus t incentive program, a comprehe nsive legislative platform, and rigorous outr each and education efforts.San Joaquin Valley Unified Air Polluti on Control District April 16, 2015

2-3 Chapter 2: PM2.5 Challenges and Trends in the San Joaquin Valley 2015 Plan for the 1997 PM2.5 Standard Figure 2-2 Atmosphere with and without a Temperature Inversion

Image source: http://ffden-2.phys.uaf.edu/212_spring2007.web.dir/Amber_Smith/ Effects_of_Inversions.htm

2.1.2 The Valley’s Carrying Capacity

In the context of air quality, c arrying capacity refers to the density of emissions that an air basin can “absorb” or “carry ” and still meet ambient air qu ality standards for a given pollutant. The key factors that shape variations in a regional carrying capacity include meteorology, climate, and the topography. Some air basins may have a high total pollutant emission rate (emission s per person or area), but if those emissions are easily dispersed or removed from the ba sin, that basin is much more li kely to meet air quality standards despite the high emi ssion rate. On the other hand, a n air basin may have aSan Joaquin Valley Unified Air Polluti on Control District April 16, 2015

2-4 Chapter 2: PM2.5 Challenges and Trends in the San Joaquin Valley 2015 Plan for the 1997 PM2.5 Standard lower emission rate, but becaus e of unfavorable environmental f actors (low air flow, stagnant air, inversions) those po llutant concentrations typica lly accumulate (possibly above the standard) and remain in the air basin until weather p atterns change. The latter scenario describes the Va lley, and the first scenario is analogous to the Los Angeles (L.A.) air basin, espec ially for NOx emissions and the formation of ozone.

As an example, total NOx emissi ons for the L.A. basin were 754 tons per day (tpd) in 2008. During that year, the L. A. basin recorded 80 days above the 1997 national 8-hour ozone standard. For the same year , the total NOx emissions for the Valley air basin were 409 tpd (over a much larger area), yet the Valley recorded 82 days above the standard. NOx dispersal is pri marily dependent on summertime w eather patterns. The L.A. basin experiences regular coastal winds through much of th e summer that not only disperse pollutants from the ai r basin, but also moderates temp eratures. Conversely, the Valley, surrounded by mountai n ranges, routinely experience s stagnant weather patterns (less wind) and extended periods of high temperatures, both of which build and concentrate ozone to levels ab ove the standard. In this real e xample, it is obvious that the Valley has a much lower carry ing capacity than the L.A. bas in for NOx, a precursor to ozone formation.

While not as drastic as the NO x-ozone example above (in terms o f emission rate), the Valley’s carrying capacity for PM2.5, when compared to the L.A. basin, is greatly affected by prevailing weather dur ing the winter months and the region’s topography (surrounding mountains). For 2008, the annual average direct P M2.5 emission rate for the L.A. basin was 80 tpd; duri ng that year, that basin recorde d 19 days above the national PM2.5 24-hour standard. F or the same year, the Valley ’s annual average direct PM2.5 emission rate was 82 tpd; however, the Valley reco rded 66 days above the 24-hour standard. During this sam e time period, the NOx and SO x emissions, which are also precursors to PM2.5, wer e significantly lower in the V alley compared to the L.A. Basin (NOx—409 tpd and 754 tpd, r espectively, as stated above; and SOx—13 tpd and 54 tpd, respectively). As noted in Section 2.2.1, temperature inversions are common during the winter months in the Valley. During these sometimes lengthy stagnant air episodes, PM2.5 emissions from da ily activities rapidly build u p to levels above the standard. It is during these event s (or anticipation of these events) that the District’s Check-Before-You-Burn program and Real-time Air Advisory Networ k (RAAN) system intervene to inform (or require) the public to limit activity t hat generates PM2.5 emissions.

The District uses quantitative ca rrying capacity analysis in it s modeling of attainment demonstrations. Such analyses can determine which combinations of PM2.5 and PM2.5 precursor emissions reduc tions can contribute to future a ttainment given anticipated population and activity growth, potential regulatio ns or control measures, and the unchanging natural ph ysical constraints.San Joaquin Valley Unified Air Polluti on Control District April 16, 2015

2-5 Chapter 2: PM2.5 Challenges and Trends in the San Joaquin Valley 2015 Plan for the 1997 PM2.5 Standard 2.2 THE VALLEY’S UN IQUE CHALLENGES

In addition to the climate and geography challenges discussed a bove, the Valley also has multiple other unique challenges that continue to impact th e Valley’s progress toward attainment of air qualit y standards. The Valley has sig nificant naturally occurring biogenic emissions. The California landscape also allows for a ir pollutant transport within the Valley, as well as bet ween the Valley and other air basins. The Valley is also one of the fastest growing regions in the state. From 2010 to 2020, the Valley’s population is expected to increas e by 18% (Table 2-1). In cont rast, the total population for the State of California is p rojected to increase by only 9% over the same time period. Increasing population generally means increases in air pollutan t emissions as a result of increased consumer product use and more automobile and truck tr avel. Between 2010 and 2020, the Valley’s total vehi cle miles traveled (VMT) will increase about 21%, 1 consistent with the Valley’s population growth. The Valley is also home to the state’s major arteries for goods and people movement, which adds to the increase in vehicular traffic.

Table 2-1 Estimated Valle y Population by County (2010-2020) 2

County Estimated 2010 Projected 2020

Fresno 932,926 1,083,889
Kern* 841,609 1,041,469 Kings 152,996 179,722
Madera 151,136 183,176
Merced 256,345 301,449 San Joaquin 686,651 795,631
Stanislaus 515,229 582,746
Tulare 443,567 536,429
Total 3,980,459 4,704,511 *Kern County is separated into tw o air districts: San Joaquin V alley and

Eastern Kern. This data is the Valley-portion of Kern only.

Although reducing mobile source emissions is critical to the Va lley’s attainment of air quality standards, the District does not have direct regulatory authority to reduce motor vehicle tailpipe emissions, whi ch are regulated by the U.S. Env ironmental Protection Agency (EPA) and California Air Resources Board (ARB). The Dis trict must collaborate with interagency par tners and use innovat ive approaches to redu ce mobile source emissions.

As Chapter 3 of this plan deta ils, the formation and compositio n of PM2.5 can be complex, with some species impa cting health more than others. Long-term trends show that PM2.5 concentrations thr oughout the Valley have declined s ince monitoring of this pollutant first began and are proj ected to continue on that tre nd. In addition to declining

1 California Air Resources Board : 2009 Almanac – Population and Vehicle Trends Tool. Retr ieved July 2012 from http://www.arb.ca.gov/app/emsinv/trends/ems_trends.php

2 California Department of Finan ce [DOF]: Interim Population Pro jects for California and its Counties 2010-2050. (May 2012). Retrieved from http://www.dof.ca.gov/research/demographic/reports/projections/ interim/view.phpSan Joaquin Valley Unified Air Polluti on Control District April 16, 2015

2-6 Chapter 2: PM2.5 Challenges and Trends in the San Joaquin Valley 2015 Plan for the 1997 PM2.5 Standard PM2.5 concentrations, most emissi ons inventories of PM2.5 precu rsors are also projected to decrease despi te future population growth.

The District also assesses long- term trends of PM2.5 concentrat ions by looking at the number of days per year that a m onitoring site measures concent rations over the 1997 24-hour PM2.5 NAAQS limit of 65 μg/m 3 . Figure 2-3 shows t he trend in numbers of days that air monitoring sites recorded 24-hour PM2.5 averages over 65 μg/m3 at the Modesto (Stanislaus County), Fres no-First/Garland (Fresno Count y), and BakersfieldCalifornia (Kern County) air moni toring sites. An overall down ward trend is apparent when comparing the early year s of 1999 and 2000 to recent years . The current pattern shows generally that the norther n Valley has the fewest days ov er the standard, that the southern Valley has the most day s over the standard, and that t he central Valley registers somewhere between the two.

Figure 2-3 Trend in Days over the 24-hour PM2.5 StandardSan Joaquin Valley Unified Air Polluti on Control District April 16, 2015

2-7 Chapter 2: PM2.5 Challenges and Trends in the San Joaquin Valley 2015 Plan for the 1997 PM2.5 Standard 2.3 PM2.5 EMISSIONS INVENTORY TRENDS

The emissions inventory is the f oundation for the attainment pl anning process. The District and ARB maintain an acco unting of PM2.5 and precursor emissions for the Valley based on known sources within the Va lley and those sourc es outside the Valley that influence Valley air qualit y (inter-region transport). Th e District requires detailed accounting of emissions from regu lated sources throughout the V alley. ARB makes detailed estimations of emissions from mobile, area, and geolog ic sources using known emissions factors for each source or activity and accounting fo r relevant economic and population data. Together, these f eed into the emissions inven tory that represents an estimate of how much direct po llution is going into the Valley air basin as a result of the cumulative pollutant-generati ng activities and sources.

The District uses the emissions i nventory to develop control st rategies, to determine the effectiveness of permitting and c ontrol programs, to provide in put into air quality modeling, to fulfill reasonable fu rther progress requirements, and to screen regulated sources for compliance investigations.

The following general list represent s the major inventory categ ories for which emissions are recorded and tracked. Appendix B to this plan contains the detailed accounting of the emissions inventor y with projected emi ssions based on antic ipated growth of each source and the antici pated control (regulat ory or non-regulator y) of each source, if applicable.

 Mobile sources – motorized vehicles

o On-road sources include autom obiles, motorcycles, buses, and t rucks

o Other or off-road sources incl ude farm and construction equipm ent, lawn and garden equipment, forklifts, loc omotives, boats, aircraft, and recreational vehicles

 Stationary sources – fixed sources of air pollution

o Power plants, refineries, and manufacturing facilities

o Aggregated point sources, i.e. fa cilities (such as gas station s and dry cleaners) that are not typically i nventoried indi vidually, but are estimated as a group and reported as a single source category

 Area sources – human activity that takes plac e over a wide geographic area

o Includes consumer products, res idential wood burning, controll ed burning, tilling, and unpaved road dust

 Natural sources – naturally occurring emissions

o Geologic sources, such as petroleum seeps

o Biogenic sources, such as emissions from plants

o Wildfire sources

Figure 2-4 shows the PM2.5 emissions inventory trend for the mo bile, stationary, and area source categories.San Joaquin Valley Unified Air Polluti on Control District April 16, 2015

2-8 Chapter 2: PM2.5 Challenges and Trends in the San Joaquin Valley 2015 Plan for the 1997 PM2.5 Standard Figure 2-4 Valley PM2.5 Wint er Emissions Inventory Trend

Because NOx is a significant P M2.5 precursor, the District reli es heavily on NOx emissions to also reduce PM2.5 e missions. Figure 2-5 summarizes the NOx emissions inventory trends for the mobile , stationary, and area source ca tegories. District and ARB control strategi es for NOx play a significant role in reduc ing both ozone and PM2.5 emissions. 0 10 20 30 40 50 60 70 80 90

2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 202 0PM2.5 Emissions (tons per day)

TOTAL STATIONARY TOTAL MOBILE TOTAL AREAWIDESan Joaquin Valley Unified Air Polluti on Control District April 16, 2015

2-9 Chapter 2: PM2.5 Challenges and Trends in the San Joaquin Valley 2015 Plan for the 1997 PM2.5 Standard Figure 2-5 Valley Winter NOx Emissions Inventory Trend

Emissions inventory trends show the progress made through progr essive regulatory and non-regulatory activities, e.g. as rules are amended with tight er emission limits, or as reduction technologies improve, overall emissions decrease. Fi gure 2-6 shows how the overall tons of PM2.5 emissions p er day have decreased in the p ast and are anticipated to continue decreasing in the fu ture based on anticipated growt h and controls. Figure 2- 6 also shows the comparative em issions inventory reduction of w inter PM2.5. Winter PM2.5 emissions have decreased s ignificantly, in large part due to the effectiveness of Rule 4901 (Wood Burning Fireplac es and Wood Burning Heaters). Continued emissions reductions are based on current control strategies th at will continue to take effect into the future. In li ght of the Valley’s projected inc rease in population, the projected emissions reductions h ighlight the success of the con trol measures adopted and enforced by the District, A RB, and other regulatory agencie s. 0 50 100 150 200 250 300 350 400 450 500

2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 202 0NOx Emissions (tons per day)

TOTAL STATIONARY TOTAL MOBILE TOTAL AREAWIDESan Joaquin Valley Unified Air Polluti on Control District April 16, 2015

2-10 Chapter 2: PM2.5 Challenges and Trends in the San Joaquin Valley 2015 Plan for the 1997 PM2.5 Standard Figure 2-6 Valley PM2.5 Annua l and Winter Inventory Trends

2.4 PM2.5 AIR Q UALITY TRENDS

As a public health agency charged with monitoring Valley air qu ality and ensuring progress toward meeting nationa l air quality standards, the Dis trict has established an extensive air monitoring netwo rk that provides ongoing data for evaluating such progress. Information from this extensive monitoring network, which began measuring PM2.5 concentrations in 1999, allow s the District to track air quality trends that show progress toward attainment and in form the planning process for reaching attainment.

2.4.1 Air Monitoring Network

Numerous pollutants and meteorol ogical parameter s are measured throughout the Valley on a daily basis using an extensive air monitoring netwo rk managed by the District, ARB, and other agencies . This network measures pollu tant concentrations necessary to show progress toward compliance with the NAAQS. T he network also provides real-time air quality m easurements used for daily air quality forecasts, residential wood-burning declara tions, Air Alerts, and RAAN. A ir quality monitoring networks are designed to monitor areas with high population den sities, areas with high pollutant concentrations, areas i mpacted by major pollutant sou rces, and areas representative of background concentrations. Together, the Dis trict and the ARB operate 33 air monitoring stat ions throughout the Valley; 20 of these sites measure PM2.5, either through the use o f filter-based monitors that mea sure each 24-hour period 0 10 20 30 40 50 60 70 80 90

2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020PM2.5 Emissions (tons per day)

ANNUAL AVERAGE WINTER AVERAGESan Joaquin Valley Unified Air Polluti on Control District April 16, 2015

2-11 Chapter 2: PM2.5 Challenges and Trends in the San Joaquin Valley 2015 Plan for the 1997 PM2.5 Standard or hourly monitors that use li ght energy to provide near-contin uous concentration levels. Figure 2-7 shows the Valley’s network of air monitoring sites.

Figure 2-7 Air Monitoring Sites in the Valley

PM2.5 is measured and expressed as the mass of particles contai ned in a cubic meter of air (micrograms per cubic meter, or μg/m 3 ). The data collected from the District’s network of PM2.5 monitors is us ed to calculate design values fo r the 24-hour and annual PM2.5 standards , as outlined in EPA guidance and regulat ions. 3,4

2.4.2 Air Quality Progress

Air quality progress can be assess ed in several ways. The calc ulation of design values is the official method used to determine whether an area is in attainment of a standard; however, other indicators can re veal more about the progress be ing made toward attaining that standard. Compar ing the days per year when each monitor exceeded the PM2.5 24-hour NAAQS threshold fr om year to year shows the progr ess in reducing the

3 Environmental Protect ion Agency [EPA]: Office of Air Quality P lanning and Standards. (1999, April). Guideline on Data Handling Conventions for the PM NAAQS (EPA-454/R-99-008). Retrieved from http://www.epa.gov/ttn/oarpg/ t1/memoranda/pmfinal.pdf

4 Interpretation of the National Ambient Air Quality Standards f or PM2.5, 40 C.F.R. Pt . 50 Appendix N (2012).San Joaquin Valley Unified Air Polluti on Control District April 16, 2015

2-12 Chapter 2: PM2.5 Challenges and Trends in the San Joaquin Valley 2015 Plan for the 1997 PM2.5 Standard number of days with the highest concentrations, while quarterly averages can help to show progress with respect to s easonal peaks in concentration l evels. Some of the conclusions from these analyses are included below, followed by a more detailed discussion in Appendix A, which a lso provides analysis results for a number of other air monitoring sites in the Valley.

Rather than using yearly maximum concentrations for the PM2.5 s tandards, EPA requires the use of design valu es for the attainment metric. D esign values represent a three-year average and help to s mooth out outlie r years with ex ceptional meteorology or exceptional events. Details on how PM2.5 design values are cal culated are provided in Appendix A of this plan. As seen in Figure 2-8, the Valley max imum 24-hour and annual average PM2.5 des ign value trends show that although the re is some year-toyear variation significant pr ogress has been m ade in reducing l ong-term PM2.5 concentrations. Valley 24-hour des ign value maximums have decr eased by 40% over the 1999–2013 time period.

This section intentionally blank.San Joaquin Valley Unified Air Polluti on Control District April 16, 2015

2-13 Chapter 2: PM2.5 Challenges and Trends in the San Joaquin Valley 2015 Plan for the 1997 PM2.5 Standard Figure 2-8 Historical PM2.5 24-hour and Annual Design Value Tr ends

Since monitoring began, the Bakers field-California and Bakersfi eld-Planz air monitoring sites in Kern County have cons istently been among the highest P M2.5 design values in the Valley. Figure 2-9 shows the trend of the 24-hour average design value at Bakersfield-California through 201 3, as demonstrated with the 2 011-2013 design value (3-year average). Figure 2-10 shows the trend o f the annual average design value atSan Joaquin Valley Unified Air Polluti on Control District April 16, 2015

2-14 Chapter 2: PM2.5 Challenges and Trends in the San Joaquin Valley 2015 Plan for the 1997 PM2.5 Standard Bakersfield Planz through 2013 , as demonstrated with the 2011–2 013 design value (3- year average).

Figure 2-9 Trend of 24-Hour Ave rage PM2.5 Design Values at Bak ersfieldCalifornia

Figure 2-10 Trend of Annual Averag e PM2.5 Design Values at Bak ersfield-Planz

Overall decreasing PM2.5 concent rations at the Bakersfield-Cali fornia and BakersfieldPlanz air monitoring sites are shown in the design value trends for those sites. The Bakersfield-California site now has a 24-hour design value at o r below the 1997 24-hourSan Joaquin Valley Unified Air Polluti on Control District April 16, 2015

2-15 Chapter 2: PM2.5 Challenges and Trends in the San Joaquin Valley 2015 Plan for the 1997 PM2.5 Standard PM2.5 standard of 65 μg/m 3 (see Figure 2-9). The annual a verage design value for 2011–2013 continues to trend lower fo r Bakersfield-Planz at 17. 3 μg/m 3 (see Figure 2- 10). This downward trend will need to continue at all sites wi thin the Valley as the Valley strives for attainment of increasingly stringent air qua lity standards.

Since the Valley’s highest PM2.5 concentrations occur during th e fall and winter months, the first (January through March) and four th (October through December) quarters tend to have the highest a verage concentrations. Obse rving the trend in these quarterly averages can shed light on how the peak of the PM2.5 season is changing over time.

Data from the Visalia monitoring site (Figure 2-11) is represen tative of fourth-quarter averages among the PM2.5 sites in the Valley. This data also s hows a downward trend of 1.20 μg/m3 per year. The Dist rict anticipates continuation of this trend as the Valley gets closer to attaining the annual average PM2.5 standard. Re fer to Appendix A for the detailed result s of this analysis.

Figure 2-11 Trend of Fourth-Quarter Average at Visalia

2.4.3 Impact of Exceptional Dr ought-Related Weather Conditions on Valley PM2.5 Concentrations

In 2012, the Bakersfield-Planz ai r monitoring site, which is th e current peak PM2.5 site in the District, recorded an annua l average value of 14.7 μg/m 3 , below the standard of 15.0 μg/m 3 . This site, along with the res t of the District’s PM2.5 air m onitoring sites, was making significant progre ss towards attaining the 1997 annu al PM2.5 standard. However, due to the exceptiona l weather conditions experienced during the winter ofSan Joaquin Valley Unified Air Polluti on Control District April 16, 2015

2-16 Chapter 2: PM2.5 Challenges and Trends in the San Joaquin Valley 2015 Plan for the 1997 PM2.5 Standard 2013-2014, exceedingly high PM2.5 concentrations were experienc ed, causing a 2013 annual average of 22.8 μg/m 3 for the Bakersfield-Planz s ite, and an annual design value (2011-2013) of 17.3 μg/m 3 (see Figure 2-10 above).

Due to the extreme weather and high values already experienced at this site in the 1 st quarter of 2014, the averages for the 2 nd , 3 rd , and 4 th quarters of 2014 would need to be zero for Bakersfield-Planz to r each attainment for the 2012-201 4 period (see Chapter 1). In addition, with the high values recorded in 2013 and 201 4, attainment during the 2013-2015 period is also impossibl e (see Chapter 4). The follo wing discusses the magnitude of the weather conditions experienced during the wint er of 2013-14, and its impact on the Valley’s ability to attain the 1997 annual PM2.5 standard.

Meteorology during the Winter Season of 2013-2014 This past winter, California Gove rnor Jerry Brown declared a st ate of emergency due to extreme drought conditions in th e state. This emergency declar ation was based on record-low precipitation in 2013 and snow pack levels at only 2 0 percent of the normal amount of snow to provide water fo r the year. Specifically in the Valley, 2013 represented the driest year since the start of r ecordkeeping in 1895. The Valley is currently experiencing an exc eptional level of drought not seen in at least 119 years.

Although the Valley has experie nced reductions in PM2.5 concent rations over the last 15 years since the pollutant fi rst began to be measured, the wi nter months of November through February continue to recor d the peak levels of each yea r. The following figure displays the relative comparison between the lower concentratio ns in March through October, and the higher concentra tions experienced during the w inter.

Figure 2-12 Average PM2.5 by M onth in 2013 in Stockton, Fresno , Bakersfield

0 10 20 30 40 50 60

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecAverage PM2.5 (μg/m3)

Stockton Fresno BakersfieldSan Joaquin Valley Unified Air Polluti on Control District April 16, 2015

2-17 Chapter 2: PM2.5 Challenges and Trends in the San Joaquin Valley 2015 Plan for the 1997 PM2.5 Standard Stable meteorology during the wi nter season can increase PM2.5 concentrations to high levels by providing strong tem perature inversi ons and low wind speeds. When this occurs, the PM2.5 concentrations during the winter months of No vember to February can climb to very high levels . As seen in Figure 2-13, the win ter of 2013-2014 experienced the strongest average atmospheric stability over th e last 15 years (period during which PM2.5 concentrati ons have been recorded), creating conducive conditions for the formation and retention of high PM2.5 concentrations. This was a result of a persistent, strong high pressure ridge over the eastern Pacific that effectively blocked weather disturbances from enterin g California, which inhibited dispersion during November, December, and January.

In addition to the historically strong atmospheric stability, t he winter of 2013-2014 also experienced record low precipitat ion totals, with some location s breaking records over 100 years old (see Table 2-2) . These unprecedented dry conditi ons exacerbated the air quality challenge durin g the winter of 2013-2014. As a result of the extreme meteorology experienc ed in the Valley, PM2.5 concentrations rea ched peak levels that had not been recorded in over a dec ade, which in turn has incre ased the Valley’s PM2.5 design values, making the journey to attainm ent of the PM2.5 st andards even more challenging.

Figure 2-13 Average Atmospheri c Stability per Winter Season

-1.5

-1 -0.5 0 0.5

1 1.5

2 2.5

3 3.51999-20002000-20012001-20022002-20032003-20042004-20052005-20062006-20072007-20082008-20092009-20102010-20112011-20122012-20132013-2014T850MB Stability Parameter ( ̊C)San Joaquin Valley Unified Air Polluti on Control District April 16, 2015

2-18 Chapter 2: PM2.5 Challenges and Trends in the San Joaquin Valley 2015 Plan for the 1997 PM2.5 Standard Table 2-2 Calendar Year Rainfa ll Totals for Select California Cities

City 1981-2010 Average (inches) 2013 Total (inches) Previous Record Low (inches) Previous Record Year
Modesto 13.11 4.70 5.70 1929
Merced 12.50 3.79 6.00 2007
Fresno 11.50 3.01 3.55 1947
Visalia 10.93 3.47 4.10 1910
Bakersfield 6.47 3.43 1.87 1959

Sacramento 18.52 5.81 6.67 1976
San Francisco 23.65 5.59 9.00 1917
San Jose 14.90 3.80 6.04 1929 Los Angeles 12.82 3.65 4.08 1953

San Diego 10.34 5.57 3.41 1953

2.5 CONDENSABLE PARTICULATES

Certain high-temperature proce sses emit gaseous pollutants that rapidly condense into particle form in the ambient air . After January 1, 2011, PM2.5 nonattainment areas are to consider these condensable par ticulates for purposes of esta blishing the emissions limits for Reasonable Further P rogress (RFP), Reasonably Availa ble Control Technology (RACT), and Reasonably Available Control Measures (R ACM). 5 In December 2010, EPA revised its “Method 202” stationary source t est method to measure condensable particulate matter. 6

While this issue may be new and mo re relevant to other regions, the District has historically included condensable particulate emissions in its definition of total particulate emissions, well ahead of federal and other states’ efforts to address this issue. This has included instit uting permit requirements for v arious emissions sources that include condensable particula tes as part of total particul ate emissions limitations, and associated emissions testi ng requiring that condensable par ticulates be measured (including utilizing an EPA-appr oved modified test method ahead of EPA’s official test method, Method 202). Condensable par ticulates are thus a part of the total PM2.5 inventory, and reductions in cond ensable particulate matter emi ssions were included in the District’s evaluation of v arious emission reduction opportu nities for directly emitted PM2.5.

2.6 INSIGNIFICANT PRECURSORS TO PM2.5 CONCENTRATIONS IN THE
VALLEY

The switch from CAA Subpart 1 to Subpart 4 (see Chapter 1) for PM2.5 implementation shifts the precursor presumpti on for planning purposes. Pursua nt to Subpart 1, areas

5 40 CFR 51.1002(c)

6 http://www.epa.gov/ttn/emc /methods/meth od202.htmlSan Joaquin Valley Unified Air Polluti on Control District April 16, 2015

2-19 Chapter 2: PM2.5 Challenges and Trends in the San Joaquin Valley 2015 Plan for the 1997 PM2.5 Standard were not required to address vo latile organic compounds (VOCs) 7 and ammonia unless technical demonstration shows t hat VOC reductions or ammonia re ductions contribute to PM2.5 attainment. Now, pursuant to Subpart 4 §189(e), areas must address potential precursors of PM2.5, i ncluding VOCs and ammonia, unle ss it is shown that they do not contribute to attainment.

In the Valley, there is extensiv e scientific research and techn ical analysis demonstrating that VOC reductions and ammonia reductions do not contribute to PM2.5 attainment. As such, the Valley’s VOC emissi ons and ammonia emissions do no t need to be reduced to address the federal P M2.5 standard. EPA concurs wit h the conclusion that VOC emissions do not contribute significantly to the formation of PM2.5 as stated in their proposed approval of the Distr ict’s plan to address the 2 006 PM2.5 standard:

“ Based on a review of the information prov ided by the District and other information available to EPA, we propose to determine t hat at this time VOC emissions do not contribute significantly to ambient PM2.5 levels ...” 8

Modeling shows that NOx controls are the most effective approac h to reduce PM2.5 nitrate concentrations, and once NO x controls are taken into co nsideration, VOC emissions reductions produce e ssentially no benefit. In fact, in some instances, VOC emissions reductions may actually lead to an increase in PM2.5 nitrate formation. Nitrogen-containing molecules can act as temporary sinks for NO 2. When VOCs are controlled, the reduced availabili ty of certain radicals which are generated from VOCs reduces the amount of NO2 that is sequestered, thereby increasi ng the availability of NO2 and enhancing ammoni um nitrate formation. 9

The extensive research mentione d above and summarized below dem onstrates that there is a relative abundance of a mmonia compared to nitric aci d, and that the amount of nitric acid drives the ultima te formation of ammonium nitrat e. Because of this regional surplus in ammonia, even substantial ammonia emissions reductions yield a relatively small reduction in n itrate. Reductions in nitrate c oncentrations of 30% to 50% were realized through a 50% reduc tion in NOx. Modeling a 50% r eduction in ammonia, while unrealistic because it’s not technologically achievable, would only realize less than a 5% reduction in nitrate concentrations. Due to the extensive body of science that clearly shows the much greater eff icacy of reducing NOx emissio ns relative to ammonia, ammonia reductions hav e not historically been consider ed a significant precursor to PM2.5 forma tion in the Valley.

7 EPA defines VOCs as any compound of carbon, excluding carbon m onoxide, carbon dioxide, carbonic acid, metallic
carbides or carbonat es, and ammonium carb onate, that participat es in atmospheric photochemical reactions to form ozone or particulates. A subse t of non-reactive VOCs does not contribute to ozone or parti culates and are exempt from regulatory controls. Many VO Cs are human-made chemicals us ed and produced in the ma nufacture of paints, adhesives, petroleum products , pharmaceuticals. The full EPA de finition is available at http://ecfr.gpoaccess.gov/cgi/t/tex t/text-idx?c=ecfr&rgn=div8&v iew=text&node=40:2.0. 1.1.2.3.8.1&idno=40

8 Approval and Promulgation of Im plementation Plan s; Designatio of Areas for Air Quality PlanningPurposes; California; San Joaquin Valley M oderate Area Plan and Reclassif ication as Serious Nonatta iemtn for the 2006 PM2.5 NAAQS; Proposed Rule, 80 Fed . Reg. 8. pp. 1816-1846. (p. 1826) (2015, January 13).

9 Meng, Z., Dabdub, D., and Seinfeld , J.H., 1997, Chemical Coupl ing Between Atmospheric Ozone and Particulate Matter, Science , 277, 116-119.San Joaquin Valley Unified Air Polluti on Control District April 16, 2015

2-20 Chapter 2: PM2.5 Challenges and Trends in the San Joaquin Valley 2015 Plan for the 1997 PM2.5 Standard 2.6.1 VOC Contribution to PM2.5 Concentrations

VOC emissions have t he potential to contribute to the formation of two different PM2.5 components: secondary organic aerosol s (SOAs) and ammonium nitr ate (nitrate). While these components contribute to observed PM2.5 concentrati ons in the Valley, their contribution is minim al. The anthropogenic VOC contribut ion (those not from biogenic sources) to both component s is so minimal, that invoki ng a VOC-centric control strategy is much less effective than primary PM2.5 controls or NOx controls, as shown through the recent res earch and modeling.

2.6.1.1 VOC Contributi on to SOA Formation Secondary organic aerosols form w hen intermediate molecular wei ght VOCs emitted by anthropogenic and biogeni c sources react and condense in the at mosphere to become aerosols. Lighter VOCs also par ticipate in the formation of at mospheric oxidants, which then participate in the formation of SOA. SOAs derived from an thropogenic VOC emissions account for only 1% to 2 % of the annual total PM2.5 c oncentrations throughout the Valley.

As part of the attainment dem onstration for the District’s 2008 PM2.5 Plan , ARB used the Community Multi-scale Air Q uality (CMAQ) model to show that primary PM2.5 emissions are the main contribut or to organic aerosols, with SO As being a small fraction of the total organic aerosol conc entration. Furthermore, SOAs are mostly formed during the summer and from predominantl y biogenic sources, when total PM2.5 concentrations are low. As such, SOAs derived from anthropogenic VOC emission s make up only 3% to 5% of the annual average or ganic aerosol concentrations.

Related to this finding, the Calif ornia Regional Particulate Ai r Quality Study (CRPAQS) also found that because of the do minance of primary PM2.5 organ ic matter, overall, a 50% reduction in anthropogenic VOC emissions has limited effect on the modeled PM2.5 organic matter. 10 Together, these study results show that for SOAs, further VOC reductions would have very limit ed effectiveness in reducing PM 2.5 concentrations.

2.6.1.2 VOC Contributi on to Nitrate Formation Nitrate forms by means of two prim ary chemical pathways: during the day, NO 2 is oxidized to nitric acid, some o f which then reacts with ammonia to form nitrate through interactions with sunlight, VOC s, and background ozone; and dur ing the night, when nitric acid is formed th rough oxidation of NO 2 (via N 2 O 5 ) by background ozone, which then reacts with ammonia to form nitrate. Several modeling stu dies 11,12,13,14 have

10 Pun, B.K., Balmori R.T.F, & Sei gneur, C. (1998). Modeling Wint ertime Particulate Ma tter Formation in Central California, Atmospheric Environment, 43 , 402-409.

11 Pun, B.K., & Seigneur, C. (1998) Conceptual Model of Particulate Matter Pollution in the California San Joaquin Valley. Prepared for Pacific Gas & Electric, Document CP045-1-98.

12 Pun, B.K. (2004). CRPAQS Task 2.7 when and where does high O3 co rrespond to high PM2.5? How much PM2.5 corresponds to photochemical end products? Prepared for the San Joaquin Va lleywide Air Pollution Study Ag ency. 13 Lurmann, F.W., Brown , S.G., McCarthy, M.C., & Roberts, P.T. (2 006). Processes Influencing Secondary Aerosol Formation in the San Joaquin Valley during Winter. Journal of Air and Waste Management Association, 56 , 1679-
1693.San Joaquin Valley Unified Air Polluti on Control District April 16, 2015

2-21 Chapter 2: PM2.5 Challenges and Trends in the San Joaquin Valley 2015 Plan for the 1997 PM2.5 Standard investigated the relative verac ity of these two mechanisms with in the Valley and attempted to determine the spec ific role and contribution of VO Cs on Valley nitrate concentrations. While the specific conclusions were mixed, the re was general agreement that the nighttime formati on of nitrate in the Valley would not be sensitive to VOC reductions.

Further modeling studies 15,16,17,18,19,20 evaluated the significance of VOC controls in reducing nitrate concentrations in the Valley. ARB evaluated e ach of these studies in the context of two key consi derations: whether further VOC redu ction would provide significant benefits to expedite attainment beyond the District ’s existing NOx control program, and what would be the feasible magnitude of any potent ial VOC reductions beyond the existing and already r igorous VOC control program. Nitrate was only responsive to a 50% reduction in VOCs at very high PM2.5 concen trations, concentrations that are no l onger reached in the Valley. In co ntrast, a 50% reduction in NOx can reduce signif icantly more nitrate at current PM2.5 conc entrations, one study 21 reporting a 38% reduction in nitrate.

Despite the insignificance of V OC emissions with regard to PM2. 5 concentrations in the Valley, VOC emissions have been reduced and will continue to be reduced through implementation of the 2007 Ozone Plan and the 2013 Plan for the Revoked 1-Hour Ozone Standard. A more detailed discussion o f the VOC influences on PM2.5 concentrations can be found in the 2012 PM2.5 Plan

. 22

2.6.2 Ammonia Contribution to PM2.5 Concentrations

Early air quality research in t he Valley identified ammonium ni trate (nitrate) as a predominant secondary PM2.5 specie s in the region, with high co ncentrations forming during the winter months. 23 Studies have continued to show that ammonium nitrate is a primary component of wintertime PM2.5 in the Valley, followed b y other species, such

14 Ying, Q., Lu, J., & Kleeman, M. ( 2009). Modeling Ai r Quality d uring the California Regiona l PM10/PM2.5 Air Quality Study (CRPAQS) Using the UCD/CIT Source-O riented Air Quality Mo del – Part III Regional S ource Apportionment of Secondary and Total Air borne Particulate Matter. Atmospheric Environment, 43 , 419-430.

15 Stockwell, W.R., Watson, J. G., Robinson, N.F., Steiner, W., & Sylte, W.W. (2000). The Ammonium Nitrate Particle Equivalent of NOx Emi ssions for Wintertime Conditions in Centra l California’s San Joaquin Valley, Atmospheric Environment, 34 , 4711-4717.

16 Pun, B.K., & Seigneur, C. (2001). Sensitivity of Particulate M atter Nitrate Forma tion to Precursor E missions in the California San Joaquin Valley. Environmental Science and Technology, 35 , 2979-2987.

17 Kleeman, M.J., Ying, Q., & Kadu wela, A. (2005). Control Strate gies for the Reduction of A irborne Particulate Nitrate
in California's S an Joaquin Valley. Atmospheric Environment, 39 , 5325-5341.

18 Meng, Z., Dabdub, D., & Seinfeld, J .H. (1997) Chemical Couplin g Between Atmospheric Ozone and Particulate
Matter. Science, 277, 116-119. DOI:10.1126/science.277.5322.116

19 Livingstone, P.L., M agliano, K., Gürer, K ., Allen, P.D., Zhang , K.M., Ying, Q., ... Byun, D. (2009). Simulating PM Concentrations during a Winter Epi sode in a Subtropical Valley: Sensitivity Simulations and Evaluation Methods. Atmospheric Environment, 43 , 5971-5977.

20 Pun, B.K., Balmori R.T.F, & Sei gneur, C. (2009). Modeling Wint ertime Particulate Ma tter Formation in Central
California. Atmospheric Environment, 43 , 402-409.

21 Ibid. 25

22 SJVAPCD. 2012 PM2.5 Plan (2013) http://www.valleyair. org/Air_Quality_Plans/PM25Plans2012.htm

23 Smith, T.B.; Lehrma n, D.E.; Reible, D.D .; and Shair, F.H. (198 1). The origin and fate of air borne pollutants within the San Joaquin Valley: Extended summary and special analysis t opics. Report No. 2. Prepared for the California Air Resources Board, and by the Calif ornia Institute of Technology, Pasadena, CA.San Joaquin Valley Unified Air Polluti on Control District April 16, 2015

2-22 Chapter 2: PM2.5 Challenges and Trends in the San Joaquin Valley 2015 Plan for the 1997 PM2.5 Standard as organic carbon, ammonium sul fate, and geologic material. 24 In addition, PM2.5 speciation data, collected for many years at four Valley urban monitoring locations, also shows nitrate’s substantial c ontribution to the Valley’s total PM2.5 concentrations, especially on days when peak 24- hour average concentrations are experienced.

2.6.2.1 Ammonium Nitrat e Formation and Precursors Formation of ammonium nitrate is described by Kleeman et al. (2 005, pp. 5326-7): 25

Particulate ammonium nitrate (NH 4 NO 3 ) forms when the concentration product of gas-phase ammonia (NH 3 ) and nitric acid (HNO 3 ) exceeds a saturation point dependent on tem perature, relative humidity, a nd the composition of the pre-existing particles that act as condensat ion substrate (Wexler and Seinfeld, 1991). 26 Ammonia is a relat ively stable compound directly emitted to the atmos phere that does not undergo signif icant chemical reaction on the time scale of i nterest to regional air quality problems. Nitric acid is an end product of the phot ochemical transformation of N Ox (NO + NO 2 ). The majority of the NOx in the SJV is emitted as NO that is then transformed into various species including NO 2 , NO 3 , HNO 2 , HNO 3 , HNO 4 , Peroxy Acetyl Nitrate (PAN), Parti culate Protein Nitrogen (PPN) , particulate nitrate, etc. The su m of NOx and the entire family of NOx reac tion products is called “reactive nitrogen” (NOy) . The fraction of reactive nit rogen that forms HNO 3 and/or nitrate depends on the c oncentration of NOx and VOC as well on meteorological conditions suc h as temperature, relative humi dity, and solar intensity (Aw and Kleem an, 2003; Nguyen and Dabdub, 2002)

. 27 28

Measurements taken at the remote Kern Wildlife St ation in the S an Joaquin Valley show that approximately 22% of the reactive nitrogen exi sts as particulate (ammonium) nitrate during typical winter conditions (Chow and Egami, 1997). 29

Nitrate buildup is a signature outcome of multi-day stagnation periods during the winter (similar buildup is not observed during warmer seasons). The m odeled regional variation of nitrate concentra tions is shown in Figure 2-14. H igher concentrations of nitrate occur in the southernmost Valley as a result of slower wind speeds and higher levels of reactive nitrogen and ammonia.

24 Ying, Q. & Kleeman, M.J., (2009). R egional Contri butions to Ai rborne Particulate Matter in Central California during a Severe Pollution Episode. Atmospheric Environment, 43 , 1218–1228.

25 Kleeman, M.J., Ying, Q., & Kadu wela, A. (2005). Control Strate gies for the Reduction of A irborne Particulate Nitrate
in California's S an Joaquin Valley. Atmospheric Environment, 39 , 5325–5341.

26 Wexler, A.S., Seinfe ld, J.H. (1991). 2nd-Generation inorganic aerosol model. Atmospheric Environment Part aGeneral Topics 25 (12), 2731–2748.

27 Aw, J., Kleeman, M.J. (2003). Evaluating the First-Order Effec t of Intra-Annual Temperatur e Variability on Urban
Air Pollution. Journal of Geophysical Research-Atmospheres 108 (D12).

28 Nguyen, K. & Dabdub, D. (2002). N Ox and VOC Control and Its Ef fects on the Formation of Aerosols. Aerosol Science and Technology 36 (5) , 560–572.

29 Chow, J.C. & Egami, R.T. (1997). San Joaquin Valley Integrated Monitoring Study: Docum entation, Evaluation, and Descriptive Analysis of PM10 and PM2.5, and Precursor Gas Measu rements. Technical support studies No. 4 and No. 8. Final Report prepared for t he California Air Resources Board, Sacramento, CA. Desert Research Institute, Reno, NV.San Joaquin Valley Unified Air Polluti on Control District April 16, 2015

2-23 Chapter 2: PM2.5 Challenges and Trends in the San Joaquin Valley 2015 Plan for the 1997 PM2.5 Standard Figure 2-14 Modeled Regional Dis tribution of Ammonium Nitrate 30

Both nitric acid and ammonia are needed to form ammonium nitrat e. The extensive research conducted through Califor nia Regional Particulate Air Quality Study (CRPAQS) and subsequent studies , as well as ongoing evaluation and modeling demonstrates that there is a rel ative abundance of ammonia (NH 3 ) compared to nitric acid (HNO 3 ), and that the amount of nitric ac id (resulting from NOx emiss ions) drives the ultimate formation of ammoni um nitrate. Figure 2-15 illust rates this ammonia abundance at the rural Angiola (Fre sno County) air monitoring s ite in the Valley during the CRPAQS field study. Ammonia concentrations are considerabl y higher than nitric acid concentrations throughout t he Valley, including urban area s with concentrated NOx emissions. 31 See Appendix G to the 2012 PM2.5 Plan for more information.

30 Chow, J.C., Chen, L.-W.A., Lowen thal, D.H., Doraiswamy, P., Pa rk, K., Kohl, S., Trimble , D.L., & Watson, J.G. (2005). California Regional PM 10/PM2.5 Air Quality Study (CRPAQ S) – Initial Data Analy sis of Field Program Measurements. Report No. 2497. P repared for California Air Reso urces Board, Sacramento, CA, by Desert Research Institute, Reno, NV.

31 Magliano, K. L. (2009) Science-Based Policies for Particulate Matter Air Quality Management in California. International Aerosol Modeling Algorithms Conference. Davis CA.San Joaquin Valley Unified Air Polluti on Control District April 16, 2015

2-24 Chapter 2: PM2.5 Challenges and Trends in the San Joaquin Valley 2015 Plan for the 1997 PM2.5 Standard Figure 2-15 Ammonia versus Nitric Acid Measurements at Angiola 32

2.6.2.2 Reducing Ammonium Nitrate Because of the regional surplus i n ammonia, even substantial am monia emissions reductions yield a relatively sm all reduction in nitrate. Figu res 2-16 and 2-17 provide a simplified illustration of this situation. As seen in Figure 2 -18, a comparable modeling analysis based on CRPAQS observa tional data found a higher disp arity between the efficiency of NOx versus ammoni a controls. Reductions in nitra te concentrations of 30% to 50% were realized through a 50% reduction in NOx. Model ing a 50% reduction in ammonia, while unrealistic because it is not technologically achievable, would only realize less than a 5% reduction in nitrate concentrations. Fi nally, Figure 2-19 provides clear correlative evidence from observed data that NOx controls are effectively reducing ammonium nitrate, despite an in crease in the regional ammonia i nventory over the same time period.

32 McCarthy, M. (2005) The Role of Nighttime Chemistry in Winter A mmonium Nitrate Formation in the San Joaquin Valley . American Association for Aero sol Research (AAAR), Supersites Conference, February 2005, Atlanta, GA.San Joaquin Valley Unified Air Polluti on Control District April 16, 2015

2-25 Chapter 2: PM2.5 Challenges and Trends in the San Joaquin Valley 2015 Plan for the 1997 PM2.5 Standard Figure 2-16 Abundance of Ammoni a in the San Joaquin Valley 33

Figure 2-17 NOx Control Reduces A mmonium Nitrate Most Efficien tly

33 Stockwell, W.R., Watson, J.G., Robinson, N.F., Steiner, W., & Sylte, W.W. (2000). The Ammonium Nitrate Particle Equivalent of NOx Emi ssions for Wintertime Conditions in Centra l California’s San Joaquin Valley, Atmospheric Environment, 34 , 4711-4717.San Joaquin Valley Unified Air Polluti on Control District April 16, 2015

2-26 Chapter 2: PM2.5 Challenges and Trends in the San Joaquin Valley 2015 Plan for the 1997 PM2.5 Standard Figure 2-18 Modeled Ammonium N itrate Response to Ammonia vs. N Ox Controls 34

Figure 2-19 Correlation betwee n NOx Reductions and Observed Am monium Nitrate in Fresno 35

34 Stockwell, W.R., Watson, J.G., Robinson, N.F., Steiner, W., & Sylte, W.W. (2000). The Ammonium Nitrate Particle Equivalent of NOx Emi ssions for Wintertime Conditions in Centra l California’s San Joaquin Valley, Atmospheric Environment, 34 , 4711-4717.

35 Stockwell, W.R., Watson, J.G., Robinson, N.F., Steiner, W., & Sylte, W.W. (2000). The Ammonium Nitrate Particle Equivalent of NOx Emi ssions for Wintertime Conditions in Centra l California’s San Joaquin Valley, Atmospheric Environment, 34 , 4711-4717.

-60% -50% -40% -30% -20% -10%

0%

50% NOx Reduction 50% Ammonia ReductionSan Joaquin Valley Unified Air Polluti on Control District April 16, 2015

2-27 Chapter 2: PM2.5 Challenges and Trends in the San Joaquin Valley 2015 Plan for the 1997 PM2.5 Standard Due to this extensive body of science that clearly shows the mu ch greater efficacy of reducing NOx emissions relative to ammonia, ammonia reductions have not historically been considered a significant pre cursor to PM2.5 formation in t he Valley. However, the District and ARB have continued to examine the potential role o f ammonia with regard to PM2.5 formation (see Appendices F and G of the 2012 PM2.5 Plan ).

The modeling sensitivity analysi s shows that reductions in ammo nia emissions achieve insignificant reductions in the PM 2.5 design values compared to reductions of direct PM2.5 and NOx emissions. Relativ e to the other pollutants, amm onia reductions at the Bakersfield-California site are only 2.3% as effective as direc t PM2.5 reductions, and only 10% as effective as NOx r eductions. Ammonia is not a sign ificant precursor to PM2.5 values in the Valley.San Joaquin Valley Unified Air Polluti on Control District April 16, 2015

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