Chapter 4 Chapter 4

Chap

Regional Trend

File 05 Chap 4 Alm2013 p1-52.indd 1 
Chapter 4 Chapter 4

ARB Almanac 2013 – Chapter 4: Regional Trends and Forecasts 

IntroductionThis chapter provides an in-depth look at emissions and air quality in California’s five major metropolitan areas (data for individual counties are provided in Appendix B). The emissions data include the latest point source estimates provided by districts as well as inventory improvements from recent SIPs. The air quality statistics include values reflecting the national ambient air quality standards. Below, we will briefly discuss some of the statistics used to characterize ozone and PM air quality in this chapter.In addition to maximum concentrations and number of days above the standards, the ozone statistics include the annual 4th high 8-hour concentration and the design value. The annual 4th high 8-hour concentration is the annual number that goes into the calculation of the national 8-hour design value. We also provide the the maximum 1-hour concentration and the national 1-hour design value. The design values are related to the national 8-hour ozone standard and the national 1-hour ozone standard (revoked). These statistics are reported for the end year of the three-year period. For example, the 2011 design value reflects data for the years 2009 through 2011.The design values are concentrations that are compared to the standard for the purpose of determining attainment status. However, values for these statistics that are included in this almanac may not satisfy data completeness requirements or the boundaries of a nonattainment area, which may differ from county or air basin boundaries. Data conforming to the established design value requirements are available for the national 8-hour ozone standard on ARB’s website at www.arb.ca.gov/airqualitytoday under “recent year’s ozone air quality.” Historical data are available on the web at www.arb.ca.gov/adam.

Finally, it is important to note that air quality statistics based on a single year of data (for example, the yearly count of days above the standard) can fluctuate from year-to-year because of variations in 

File 05 Chap 4 Alm2013 p1-52.indd 2 
Chapter 4 Chapter 4

ARB Almanac 2013 – Chapter 4: Regional Trends and Forecasts 

(This page intenti

File 05 Chap 4 Alm2013 p1-52.indd 3 
Chapter 4 Chapter 4

ARB Almanac 2013 – Chapter 4: Regional Trends and Forecasts 

The South Coast Air Basin is California’s largest metropolitan region. The area includes the southern two-thirds of Los Angeles County, all of Orange County, and the western urbanized portions of Riverside and San Bernardino counties. It covers a total of 6,480 square miles, is home to more than 42 percent of California’s population, and generates about 24 percent of the State’s total NOx emissions and about 

16 percent of the State’s total PM2.5 emissions.

The South Coast Air Basin generally forms a lowland plain, bounded by the Pacific Ocean on the west and by mountains on the other three sides. In terms of air pollution potential, the warm sunny weather associated with a persistent high pressure system is conducive to the formation of ozone, commonly referred to as “smog.” The problem is further aggravated by the surrounding mountains, frequent low inversion heights, and stagnant air conditions. All of these factors act together to trap pollutants in the air basin.Pollutant concentrations in parts of the South Coast Air Basin are among the highest in the nation. As a result, controlling the contributing emission sources poses a great challenge to State and local air pollution control agencies.

South Coast Air BasinIntroduction - Area Description

File 05 Chap 4 Alm2013 p1-52.indd 4 
Chapter 4 Chapter 4

ARB Almanac 2013 – Chapter 4: Regional Trends and Forecasts 

South Coast Air Basin Emissions (tons/day, annual average)

Pollutant 2000 2005 2010 2015 2020 2025 2030 2035VOC 956 678 544 429 400 393 393 391

NOX 1106 888 603 451 357 289 266 257

SOX 53 50 19 18 17 17 18 20

DPM 22 21 12 7 5 4 4 4PM2.5 88 84 71 67 67 68 70 71PM10 179 175 160 155 161 165 170 172

NH3 123 107 92 96 93 91 93 92

Overall, since 2000 the emission levels for the ozone precursors NOxand VOC have been decreasing in the South Coast Air Basin and are projected to continue decreasing through 2035. The decreases are predominantly due to motor vehicle controls and reductions in evaporative emissions. In the South Coast Air Basin, on-road motor vehicles are the largest contributors to NOx, and VOC emissions. 

Other mobile sources are also significant contributors to NOx emissions. The emission levels for SOx have decreased since 2000. This 

is mainly due to the switch from fuel oil to natural gas for electric generation and to reduced sulfur content in fuels.

South Coast Air BasinEmission Trends and ForecastsTable 4-1 

File 05 Chap 4 Alm2013 p1-52.indd 5 
Chapter 4 Chapter 4

ARB Almanac 2013 – Chapter 4: Regional Trends and Forecasts 

South Coast Air BasinOzone Precursor Emission - Trends and Forecasts

Emissions of the ozone precursors NOx and VOC in the South Coast 

Air Basin are generally following the statewide downward trend. Motor vehicle miles traveled in the basin are increasing, but NOx and 

VOC emissions from on-road vehicles are dropping as more stringent vehicle emission standards have been adopted. These decreases in NOx and VOC emissions are projected to continue between 2010 

and 2035, as even more stringent motor vehicle standards are impleTable 4-3 

Figure 4-3 

0

100200

300400500600700800

2000 2005 2010 2015 2020 2025 2030 2035

Annual Average (tons/day) 

NOX Emission Trends 

Stationary Sources Area-wide Sources On-Road Mobile Other Mobile

NOX Emission Trends (tons/day, annual average)

Emission Source 2000 2005 2010 2015 2020 2025 2030 2035All Sources 1106 888 603 451 357 289 266 257

Stationary Sources 135 67 62 54 54 55 56 57Area-wide Sources 32 28 21 19 18 16 15 14On-Road Mobile 707 580 381 249 172 118 102 96 Gasoline Vehicles 399 246 173 111 73 52 40 31 Diesel Vehicles 308 334 208 138 99 65 61 65Other Mobile 232 214 139 128 113 99 93 91

 Gasoline Fuel 27 25 18 15 14 14 14 14 Diesel Fuel 175 164 101 94 79 66 59 56 Other Fuel 29 25 20 19 19 20 21 22

File 05 Chap 4 Alm2013 p1-52.indd 6 
Chapter 4 Chapter 4

ARB Almanac 2013 – Chapter 4: Regional Trends and Forecasts 

Direct emissions of PM2.5 have decreased in the South Coast Air 

Basin since 2000. Stationary source and area-wide source emissions have remained relatively flat. The bulk of the decline of PM2.5 emissions are from diesel mobile sources.

Particulate matter can be directly emitted into the air (primary PM) or, similar to ozone, it can be formed in the atmosphere (secondary PM) from the reaction of gaseous precursors such as NOx, SOx, VOC, 

and ammonia. The PM2.5 emission inventory includes only directly 

emitted particulate emissions.

South Coast Air BasinDirectly Emitted PM2.5 Emission - Trends and Foreca

File 05 Chap 4 Alm2013 p1-52.indd 7 
Chapter 4 Chapter 4

ARB Almanac 2013 – Chapter 4: Regional Trends and Forecasts 

South Coast Air BasinDiesel PM Emission - Trends and ForecastsDiesel PM emissions decreased from 2000 to 2010 primarily as a result of reduced exhaust emissions from diesel mobile sources. These decreases can be attributed to the efforts of ARB’s Diesel Risk Reduction Plan. Since its adoption in 2000, this program has achieved reductions in DPM emissions from on-road and off-road vehicles as well as stationary and portable diesel-fueled engines. This has been accomplished through new regulatory standards for all new diesel-fueled engines and vehicles along with retrofit requirements (e.g. catalyzed diesel particulate filters) for existing engines and vehicles. Additional reductions are being achieved through improvements to the quality of diesel fuel by the reduction of sulfur content.Through programs such as the Diesel Risk Reduction Program, emissions from diesel mobile sources are projected to continue to decrease through 2035.

File 05 Chap 4 Alm2013 p1-52.indd 8 
Chapter 4 Chapter 4

ARB Almanac 2013 – Chapter 4: Regional Trends and Forecasts 

Ammonia emissions have decreased in the South Coast Air Basin since 2000. Area-wide source emissions from livestock waste and pesticide usage are expected to remain relatively flat from 2020 through 2035. Ammonia emissions from stationary sources, mainly waste disposal and fuel combustion, are forecasted to increase slightly from 2015 to 2035, while on-road mobile source emissions remain flat during the same period.South Coast Air BasinAmmonia Emission - Trends and Forecasts

File 05 Chap 4 Alm2013 p1-52.indd 9 
Chapter 4 Chapter 4

ARB Almanac 2013 – Chapter 4: Regional Trends and Forecasts 

South Coast Air BasinOzone Air Quality TrendOzone air quality in the South Coast Air Basin has improved substantially over the last 50 years. During the 1960s, maximum 1-hour concentrations were above 0.60 ppm. Today, ozone levels rarely reach 0.15 ppm, and typical maximum daily values only occasionally reach the former federal standard of 0.124 ppm. The 2012 8-hour design value was 41 percent lower than the 1992 value. The number of days above the standards has also declined dramatically, and the trend for 1-hour ozone is similar to that for 8-hour. Today, nearly 60 percent of the population lives in areas that meet the 8-hour ozone standard.Although ozone has improved substantially over time, the rate of progress has been more modest in recent years. This may be attributable to changes in the mix and reactivity of precursor emissions in the South Coast. Continuing implementation of emissions control measures will ensure continued progress throughout the Air Basin.The South Coast is designated nonattainment for the 1-hour ozone standard and the 8-hour ozone standard. ARB and the South Coast Air Quality Management District have developed SIPs to demonstrate how the region will meet these standards. U.S. EPA has approved a SIP showing the Basin will meet the 0.08 ppm 8-hour ozone standard by 2023. ARB has also submitted a SIP to U.S. EPA demonstrating the area will meet the 1-hour ozone standard in 2022. These plans call for continuing NOx and VOC reductions needed to 

meet the ozone standards. These reductions result from regulations and incentive programs that lead to cleaner vehicles for on-road and 

Table 4-8 1 The national 1-Hour standard has been revoked. Current and historical 1-Hour data are provided for reference.

OZONE (ppm) 1992 1993 1994 1995 1996 1997 1998 1999 20Annual 4th High 8-Hour 0.183 0.172 0.163 0.166 0.154 0.135 0.183 0.133 0.8-Hour Design Value 0.180 0.177 0.171 0.165 0.161 0.148 0.154 0.147 0.Maximum 1-Hour Concentration 0.300 0.280 0.300 0.256 0.239 0.205 0.244 0.174 0.1-Hour Design Value1 0.300 0.300 0.280 0.250 0.231 0.215 0.217 0.211 0.2

Days Above Nat. 8-Hour Standard 191 183 164 150 141 155 120 120 

File 05 Chap 4 Alm2013 p1-52.indd 10 
Chapter 4 Chapter 4

ARB Almanac 2013 – Chapter 4: Regional Trends and Forecasts 

South Coast Air BasinOzone Contour Maps: 3-Year Average of National 8-H

1992 

Another way to look at ozone air quality is to evaluate how widespread the problem is within a region. The maps on this page illustrate how the number of days exceeding the national 8-hour standard have changed across the South Coast Air Basin over the last two decades. Three-year averages are used to help mitigate the impact of changes in meteorology.Overall, the two maps show a substantial reduction in the number of exceedance days over the last 20 years. During the 1992 time period, nearly all of the South Coast had more than 50 exceedance days, with more than 100 days in nearly one-third of the air basin. This is equivalent to more than three months during a year with ozone concentrations above the level of the standard. The coastal areas were cleaner 

Figure 4-9 

File 05 Chap 4 Alm2013 p1-52.indd 11 
Chapter 4 Chapter 4

ARB Almanac 2013 – Chapter 4: Regional Trends and Forecasts 

South Coast Air BasinPM2.5 Air Quality TrendSimilar to ozone, PM2.5 levels in the South Coast have decreased 

significantly since monitoring began in 1999. Figure 4-11 shows the 24-hour and annual average PM2.5 design values in the South Coast 

Air Basin from 1999 through 2011. Overall, the annual average design value has decreased 46 percent since PM2.5 monitoring began. 

The 24-hour PM2.5 design value has also declined 49 percent within 

the same period.The South Coast Air Basin is currently designated as nonattainment for both the annual and 24-hour PM2.5 standards. In 2012, the South 

Coast adopted the 2012 Air Quality Management Plan. The plan incorporates a comprehensive strategy aimed at controlling pollution from all sources, including stationary sources, on-road and off-road mobile sources and area sources. The 2012 plan demonstrates attainment of the federal 24-hour PM2.5 standard by 2014. In addition, U.S. EPA 

has approved a plan showing how the basin will meet the 15 μg/m3

annual PM2.5 standard by 2014. Measures adopted as part of the 

PM2.5 SIP, as well as programs to reduce ozone and diesel PM will 

continue to reduce public exposure to PM2.5 in this region. By 2016, 

the District will submit a new PM2.5 plan demonstrating how the 

region will meet the revised 12 μg/m3 annual PM2.5 standard.

The South Coast Air Basin meets the federal 24-hour PM10 standard.

Table 4-9 

PM2.5 (μg/m3) 1999 2000 2001 2002 2003 

98th Percentile of 24-Hr Conc. 85.6 83.0 74.3 66.3 76.6 24-Hour Design Value 76.0 73.0 72.0 Maximum Annual Average 30.2 28.3 31.0 27.5 24.8 Annual Design Value 29.8 28.9 27.8 

File 05 Chap 4 Alm2013 p1-52.indd 12 
Chapter 4 Chapter 4

ARB Almanac 2013 – Chapter 4: Regional Trends and Forecasts 

South Coast Air BasinNitrogen Dioxide Air Quality TrendOver the last 20 years, NO2 values have decreased significantly in the 

South Coast Air Basin. The national 1-hour design value for 2011 was over 67 percent lower than what it was during 1992.The national annual average standard has not been exceeded since 1991. A new national 1-hour standard was adopted by U.S. EPA in January 2010 and is intended to focus on near-road NO2 exposure. 

As a result, a new near-road monitoring network is in the process of being deployed. The South Coast federal 1-hour design value is 72 ppb, well below the national 1-hour standard of 100 ppb (98th percentile).NO2 is formed from NOx emissions, which also contribute to ozone. 

As a result, the majority of the future emission control measures will be implemented as part of the overall ozone control strategy. Many of these control measures will target mobile sources, which account for more than three-quarters of California’s NOx emissions.

Table 4-10 

NITROGEN DIOXIDE (ppb) 1992 1993 1994 1995 1996 1997 1998 1999 Maximum 1-Hour Concentration 300 260 247 239 250 200 255 307 1-Hour Design Value 223 190 171 168 151 138 127 133 Maximum Annual Average 51 50 50 46 42 43 43 51 

File 05 Chap 4 Alm2013 p1-52.indd 13 
Chapter 4 Chapter 4

ARB Almanac 2013 – Chapter 4: Regional Trends and Forecasts 

The San Francisco Bay Area is California’s second largest metropolitan area. The nine county area comprises all of Alameda, Contra Costa, Marin, Napa, San Francisco, San Mateo, and Santa Clara counties, the southern half of Sonoma County, and the southwestern portion of Solano County. The area is oriented north-south and covers about 400 square miles of the area’s total 5,340 square miles.About 19 percent of California’s population resides in the San Francisco Bay Area, and pollution sources in the region account for about 15 percent of the State’s total NOx emissions and about eleven percent of 

the State’s total PM2.5 emissions. The climate in the San Francisco 

Bay Area varies. Along the coast, temperatures are mild year-round. However, as one moves inland, temperatures show larger diurnal and seasonal variations. Overall air quality in the San Francisco Bay Area Air Basin is better than inland areas such as the South Coast, San Joaquin Valley, and Sacramento regions. This is due to a more favorable climate, with cooler temperatures and better ventilation. 

San Francisco Bay Area Air BasinIntroduction - Area Description

File 05 Chap 4 Alm2013 p1-52.indd 14 
Chapter 4 Chapter 4

ARB Almanac 2013 – Chapter 4: Regional Trends and Forecasts 

The emission levels for the ozone precursors NOx and VOC have 

been trending downward in the San Francisco Bay Area Air Basin since 2000. On-road motor vehicles are the largest contributors to VOC, and NOx emissions in the air basin. The implementation of 

stricter mobile source (both on-road and other) emission standards will continue to decrease vehicle emissions in this air basin. Controls on stationary source solvent evaporation and fugitive emissions will also continue to reduce VOC emissions. The emission levels for SOx

are also projected to decrease from 2000 to 2015. This is mainly due to the switch from fuel oil to natural gas for electric generation and to reduced fuel sulfur content.

San Francisco Bay Area Air BasinEmission Trends and Forecasts

Table 4-11 

San Francisco Air Basin Emissions (tons/day, annual average)

Pollutant 2000 2005 2010 2015 2020 2025 2030 2035VOC 502 352 293 236 222 217 217 216

NOX 591 445 345 272 219 191 181 176

SOX 71 60 30 24 25 26 28 30

DPM 10 9 6 3 2 2 2 2PM2.5 76 60 55 44 44 44 48 48PM10 157 133 129 119 121 122 127 129

NH3 33 32 30 31 30 30 31 31

File 05 Chap 4 Alm2013 p1-52.indd 15 
Chapter 4 Chapter 4

ARB Almanac 2013 – Chapter 4: Regional Trends and Forecasts 

San Francisco Bay Area Air BasinOzone Precursor Emission - Trends and Forecasts

Emissions of ozone precursors have decreased in the San Francisco Bay Area Air Basin since 2000 and are projected to continue declining through 2035. The Bay Area has a significant motor vehicle population, and the implementation of stricter motor vehicle controls has resulted in significant emissions reductions for NOx and VOC. 

NOX Emission Trends (tons/day, annual average)

Emission Source 2000 2005 2010 2015 2020 2025 2030 2035All Sources 591 445 345 272 219 191 181 176

Stationary Sources 87 49 43 40 40 40 41 42Area-wide Sources 20 16 15 16 17 18 19 20On-Road Mobile 354 267 187 127 84 59 51 46 Gasoline Vehicles 218 128 86 54 36 26 20 15 Diesel Vehicles 136 139 101 72 48 33 31 30Other Mobile 130 112 99 89 79 73 70 68

 Gasoline Fuel 13 12 8 7 7 6 7 7 Diesel Fuel 92 77 66 55 43 38 35 33 Other Fuel 25 24 25 27 29 29 29 29

0

50

100

150200250300350400

2000 2005 2010 2015 2020 2025 2030 2035

Annual Average (tons/day) 

NOX Emission Trends 

Stationary Sources Area-wide Sources On-Road Mobile Other Mobile

Figure 4-15 

Table 4-13 

File 05 Chap 4 Alm2013 p1-52.indd 16 
Chapter 4 Chapter 4

ARB Almanac 2013 – Chapter 4: Regional Trends and Forecasts 

Direct emissions of PM2.5 have declined in the San Francisco Bay 

Area Air Basin between 2000 and 2010 and are projected to increase slightly through 2035. Emissions from stationary sources declined, while area-wide sources are projected to slightly increase after 2015. This increase in area-wide sources is primarily due to growth in fugitive dust sources. Emissions of directly emitted PM2.5 from diesel 

motor vehicles have been decreasing since 2000 due to adoption of more stringent emission standards; even while population and VMT have increased steadily.Particulate matter can be directly emitted into the air (primary PM) or, similar to ozone, it can be formed in the atmosphere (secondary PM) from the reaction of gaseous precursors such as NOx, SOx, VOC, 

and ammonia. The PM2.5 emission inventory includes only directly 

emitted particulate emissions. 

San Francisco Bay Area Air BasinDirectly Emitted PM2.5 Emission - Trends and Foreca

File 05 Chap 4 Alm2013 p1-52.indd 17 
Chapter 4 Chapter 4

ARB Almanac 2013 – Chapter 4: Regional Trends and Forecasts 

San Francisco Bay Area Air BasinDiesel PM Emission - Trends and ForecastsDiesel PM emissions decreased from 2000 to 2010 primarily as a result of reduced exhaust emissions from diesel mobile sources. Emissions from diesel mobile sources are projected to continue to decrease through 2035.

File 05 Chap 4 Alm2013 p1-52.indd 18 
Chapter 4 Chapter 4

ARB Almanac 2013 – Chapter 4: Regional Trends and Forecasts 

Ammonia emissions are forecasted to remain flat in the San Francisco Bay Area Air Basin from 2000 through 2035. Most of the ammonia emissions are from area-wide sources, particularly from livestock waste and pesticide usage. Other sources of ammonia emissions are stationary sources, mainly waste disposal and fuel combustion, and on-road mobile sources.San Francisco Bay Area Air BasinAmmonia Emission - Trends and Forecasts

File 05 Chap 4 Alm2013 p1-52.indd 19 
Chapter 4 Chapter 4

ARB Almanac 2013 – Chapter 4: Regional Trends and Forecasts 

San Francisco Bay Area Air BasinOzone Air Quality Trend Ozone concentrations in the San Francisco Bay Area are much lower than in the South Coast and San Joaquin Valley Air Basins. The 1- and 8-hour design values have declined by an average of nearly 17 percent during the last 20 years. The number of days when national standards are exceeded shows a similar trend. The 2012 8-hour design value indicates that the area now meets the 2008 federal standard. Continuing implementation of statewide emissions control measures will ensure continued progress throughout the Air Basin.In September 2010, the Bay Area Air Quality Management District adopted the Bay Area 2010 Clean Air Plan. The 2010 plan defines a comprehensive multi-pollutant control strategy including 55 control measures to reduce emissions of ozone, PM, air toxics, and greenhouse gases from a wide variety of emission sources.

OZONE (ppm) 1992 1993 1994 1995 1996 1997 1998 1999 20Annual 4th High 8-Hour 0.082 0.082 0.082 0.099 0.099 0.072 0.096 0.093 0.08-Hour Design Value 0.082 0.081 0.082 0.087 0.093 0.090 0.089 0.086 0.0Maximum 1-Hour Concentration 0.130 0.130 0.130 0.155 0.138 0.114 0.147 0.156 0.11-Hour Design Value1 0.130 0.120 0.121 0.138 0.138 0.138 0.138 0.139 0.1

Days Above Nat. 8-Hour Standard 18 18 13 22 25 5 24 18 

Table 4-18 1 The national 1-Hour standard has been revoked. Current and historical 1-Hour data are provided for reference.

File 05 Chap 4 Alm2013 p1-52.indd 20 
Chapter 4 Chapter 4

ARB Almanac 2013 – Chapter 4: Regional Trends and Forecasts 

San Francisco Bay Area Air BasinPM2.5 Air Quality TrendThe San Francisco Bay Area has seen significant progress in both the 24-hour and annual average PM2.5 design values over the last 13 

years. The San Francisco Bay Area is in attainment of the national annual average PM2.5 standard and concentrations have decreased 

36 percent since 2001. The 24-hour design value has seen the biggest decline over the past 13 years, decreasing 62 percent.Although the Bay Area is designated as non-attainment for the 24-hour national PM2.5 standard, recent monitoring data now shows 

that the Bay Area meets the 24-hour PM2.5 standard. U.S. EPA 

approved a “clean data determination” for the 24-hour PM2.5 standard for the Bay Area on January 9, 2013.

The San Francisco Bay Area Air Basin also attains the national 24-hour standard for PM10. 

Table 4-19 

PM2.5 (μg/m3) 1999 2000 2001 2002 2003 

98th Percentile of 24-Hr Conc. 69.3 63.4 80.0 57.6 37.4 24-Hour Design Value 71.0 63.0 47.0 Maximum Annual Average 16.2 13.6 12.8 14.0 11.7 Annual Design Value 14.2 12.7 11.9 

File 05 Chap 4 Alm2013 p1-52.indd 21 
Chapter 4 Chapter 4

ARB Almanac 2013 – Chapter 4: Regional Trends and Forecasts 

San Francisco Bay Area Air BasinNitrogen Dioxide Air Quality TrendThe San Francisco Bay Area has attained the national NO2 standards 

for more than 20 years and ambient concentrations continue to be well below the level of the standard. The 1-hour design value has declined 36 percent since 1992 and design values are below the level of the 1-hour federal standard of 100 ppb.A new national 1-hour standard was adopted by U.S. EPA in January 2010 and is intended to focus on near-road NO2 exposure. 

As a result, a new near-road monitoring network is in the process of being deployed.NO2 is formed from NOx emissions, which also contribute to ozone. 

As a result, the majority of the future emission control measures will be implemented as part of the overall ozone control strategy. Many of these control measures will target mobile sources, which account for more than three-quarters of California’s NOx emissions.

Table 4-20 

NITROGEN DIOXIDE (ppb) 1992 1993 1994 1995 1996 1997 1998 1999 Maximum 1-Hour Concentration 110 120 107 116 108 118 98 128 1-Hour Design Value 110 97 85 90 87 84 78 82 Maximum Annual Average 25 27 28 27 25 25 25 26 

File 05 Chap 4 Alm2013 p1-52.indd 22 
Chapter 4 Chapter 4

ARB Almanac 2013 – Chapter 4: Regional Trends and Forecasts 

(This page intenti

File 05 Chap 4 Alm2013 p1-52.indd 23 
Chapter 4 Chapter 4

ARB Almanac 2013 – Chapter 4: Regional Trends and Forecasts 

The San Joaquin Valley Air Basin (Valley) occupies the southern two-thirds of California’s Central Valley. The eight-county area comprises Fresno, Kings, Madera, Merced, San Joaquin, Stanislaus, and Tulare counties and the western portion of Kern County. The Valley covers nearly 23,490 square miles. With very few exceptions, the San Joaquin Valley is flat, with most of the area lying below 1,000 feet in elevation and most of the population living below 500 feet. The Valley floor slopes downward from east to west, and the San Joaquin River winds its way along the western side from south to north.Similar to other inland areas, the San Joaquin Valley has cool wet winters and hot dry summers. Generally, the temperature increases and rainfall decreases from north to south.In contrast to other California areas, air quality in the San Joaquin Valley is not dominated by emissions from one large urban area. Instead, there are a number of moderately sized urban areas spread along the main axis of the Valley. Overall, about 10 percent of California’s population lives in the San Joaquin Valley, and pollution sources in the region account for about 15 percent of the State’s total NOx emissions and about 18 percent of the State’s total PM2.5 emissions.San Joaquin Valley Air BasinIntroduction - Area Description

File 05 Chap 4 Alm2013 p1-52.indd 24 
Chapter 4 Chapter 4

ARB Almanac 2013 – Chapter 4: Regional Trends and Forecasts 

San Joaquin Valley Air Basin Emissions (tons/day, annual average)

Pollutant 2000 2005 2010 2015 2020 2025 2030 2035VOC 486 441 408 344 345 352 356 358

NOX 567 529 363 272 212 173 159 153

SOX 27 15 12 10 10 10 11 11

DPM 16 16 11 6 5 4 3 3PM2.5 100 93 77 73 72 72 72 72

PM10 359 305 284 278 278 276 275 274NH3 379 408 434 390 417 444 446 448

The emission levels in the San Joaquin Valley Air Basin have been decreasing since 2000. The decreases are predominantly due to motor vehicle controls and reductions in evaporative and fugitive emissions. On-road motor vehicles, other mobile sources, and stationary sources are all significant contributors to NOx emissions. A significant portion of the stationary source VOC emissions is fugitive emissions 

from the extensive oil and gas production operations in the lower San Joaquin Valley. PM10 emissions are mostly fugitive dust from 

paved and unpaved roads, agricultural operations, and waste burning. The emission levels for SOx have also decreased since 2000. This is 

mainly due to the switch from fuel oil to natural gas for electric generation and to reduced fuel sulfur content.

San Joaquin Valley Air BasinEmission Trends and Forecasts

Table 4-21 

File 05 Chap 4 Alm2013 p1-52.indd 25 
Chapter 4 Chapter 4

ARB Almanac 2013 – Chapter 4: Regional Trends and Forecasts 

San Joaquin Valley Air BasinOzone Precursor Emission - Trends and ForecastsEmissions of the ozone precursors NOx and VOC are projected to 

decrease in the San Joaquin Valley Air Basin through 2020. While NOx continues to decline after 2020, VOC increases slightly. Both 

stationary source and motor vehicle NOx emissions have been 

reduced by the adoption of more stringent emission standards. 

NOX Emission Trends (tons/day, annual average)

Emission Source 2000 2005 2010 2015 2020 2025 2030 2035All Sources 567 529 363 272 212 173 159 153

Stationary Sources 75 59 41 30 28 28 27 28Area-wide Sources 15 16 13 13 13 13 14 14On-Road Mobile 324 310 205 138 91 67 65 65 Gasoline Vehicles 101 65 51 32 22 17 14 12 Diesel Vehicles 223 245 155 106 69 50 51 54Other Mobile 153 144 103 91 79 64 53 46

 Gasoline Fuel 55443333 Diesel Fuel 144 135 95 84 70 55 45 37 Other Fuel 44335555

0

50

100150200250300

350

2000 2005 2010 2015 2020 2025 2030 2035

Annual Average (tons/day) 

NOX Emission Trends 

Stationary Sources Area-wide Sources On-Road Mobile Other Mobile

Figure 4-25 

Table 4-23 

File 05 Chap 4 Alm2013 p1-52.indd 26 
Chapter 4 Chapter 4

ARB Almanac 2013 – Chapter 4: Regional Trends and Forecasts 

Direct emissions of PM2.5 decreased from 2000 to 2015 and are projected to remain flat after 2015. PM2.5 emissions in the San Joaquin 

Valley are dominated by emissions from area-wide sources, primarily fugitive dust from vehicle travel on unpaved and paved roads, dust from farming operations, waste burning, and residential fuel combustion (including wood).Particulate matter can be directly emitted into the air (primary PM) or, similar to ozone, it can be formed in the atmosphere (secondary PM) from the reaction of gaseous precursors such as NOx, SOx, ROG, 

and ammonia. The PM2.5 emission inventory includes only directly 

emitted particulate emissions.

San Joaquin Valley Air BasinDirectly Emitted PM2.5 Emission - Trends and Foreca

File 05 Chap 4 Alm2013 p1-52.indd 27 
Chapter 4 Chapter 4

ARB Almanac 2013 – Chapter 4: Regional Trends and Forecasts 

San Joaquin Valley Air BasinDiesel PM Emission - Trends and ForecastsDiesel PM emissions decreased from 2000 to 2010 primarily as a result of reduced exhaust emissions from diesel mobile sources. Emissions from diesel mobile sources are projected to continue to decrease through 2035.

File 05 Chap 4 Alm2013 p1-52.indd 28 
Chapter 4 Chapter 4

ARB Almanac 2013 – Chapter 4: Regional Trends and Forecasts 

Ammonia emissions are forecasted to remain relatively constant. About 92 percent of the emissions are from area-wide source emissions from livestock waste and pesticide usage.San Joaquin Valley Air BasinAmmonia Emission - Trends and Forecasts

File 05 Chap 4 Alm2013 p1-52.indd 29 
Chapter 4 Chapter 4

ARB Almanac 2013 – Chapter 4: Regional Trends and Forecasts 

San Joaquin Valley Air BasinOzone Air Quality TrendOzone levels in the San Joaquin Valley are among the most severe in the State. During the 1980s the Valley averaged nearly 60 federal 1-hour exceedance days per year. However, now the Valley only occasionally exceeds the 1-hour standard. Additionally, 8-hour design values have declined an average of nearly 17 percent, while the threeyear average of the national 8-hour exceedance days declined nearly 30 percent. Most of this progress has occurred since 2003. Today, nearly 16 percent of the population live in areas that meet the 8-hour ozone standard, compared with 20 years ago when the standard was exceeded throughout the Valley.Similar to the South Coast the San Joaquin Valley is designated nonattainment for the 1-hour and 8-hour ozone standards. ARB and the San Joaquin Valley Air Pollution Control District have developed SIPs to demonstrate how the region will meet these standards. U.S. EPA has approved a SIP showing the Valley will meet the 0.08 ppm 8-hour ozone standard by 2023. The District has also recently adopted a SIP demonstrating the area will meet the 1-hour ozone standard by 2017. These plans call for continuing NOx and VOC reductions needed to meet the ozone standards.These reductions result from regulations and incentive programs that lead to cleaner vehicles for on-road and off-road applications, less polluting consumer products, and industrial and commercial sources. By 2016, the District will submit a new plan 

OZONE (ppm) 1992 1993 1994 1995 1996 1997 1998 1999 20Annual 4th High 8-Hour 0.110 0.117 0.118 0.123 0.126 0.115 0.124 0.109 0.8-Hour Design Value 0.115 0.112 0.111 0.119 0.119 0.115 0.115 0.113 0.Maximum 1-Hour Concentration 0.160 0.160 0.175 0.173 0.165 0.147 0.169 0.155 0.1-Hour Design Value1 0.160 0.160 0.160 0.164 0.165 0.164 0.161 0.161 0.

Days Above Nat. 8-Hour Standard 155 144 137 142 143 138 112 153 

Table 4-28 1 The national 1-Hour standard has been revoked. Current and historical 1-Hour data are provided for reference.

File 05 Chap 4 Alm2013 p1-52.indd 30 
Chapter 4 Chapter 4

ARB Almanac 2013 – Chapter 4: Regional Trends and Forecasts 

San Joaquin Valley Air BasinOzone Contour Maps: 3-Year Average of National 8-H

1992 

Another way to look at ozone air quality is to evaluate how widespread the problem is within the Air Basin, using data for all sites. The maps on this page illustrate the reduction in days exceeding the national 8-hour standard over the last two decades throughout the basin. The use of three-year averages helps to mitigate year-to-year changes in meteorology.Similar to the South Coast, the two maps show a substantial reduction in the number of exceedance days over the last 20 years. During the 1992 time period, far more than half of the San Joaquin Valley had between 51 and 100 exceedance days. The worst site had 169 days, which is equivalent to nearly six months during a year with ozone concentrations above the level of the standard. Areas in the northern San Joaquin Valley were cleaner than areas in the central and southern Valley.

Figure 4-31 

File 05 Chap 4 Alm2013 p1-52.indd 31 
Chapter 4 Chapter 4

ARB Almanac 2013 – Chapter 4: Regional Trends and Forecasts 

San Joaquin Valley Air BasinPM2.5 Air Quality TrendWhile the San Joaquin Valley has unique geographical and meteorological challenges, the annual design value for PM2.5 shows an 

overall downward trend, decreasing 26 percent from 2001 to 2011. The 24-hour PM2.5 design value also declined 40 percent during this 

period, with the most pronounced progress between 2001 and 2004.The San Joaquin Valley Air Basin is currently designated as nonattainment for the annual and 24-hour PM2.5 standards. The San 

Joaquin Valley adopted their 2012 PM2.5 SIP in December 2012 that 

shows attainment of the 24-hour PM2.5 standard by 2019. The plan 

incorporates a comprehensive strategy aimed at controlling pollution from all sources, including stationary sources, on-road and off-road mobile sources and area sources. In addition, U.S. EPA has approved a plan showing how the Valley will meet the 15 μg/m3 annual PM2.5

standard in 2014. Measures adopted as part of the PM2.5 SIP which 

includes programs to reduce ozone and diesel PM will continue to reduce public exposure to PM2.5 in this region. In 2016, the District 

will submit a new PM2.5 plan demonstrating how the region will meet 

the revised 12 μg/m3annual PM2.5 standard.

The San Joaquin Valley attains the national 24-hour standard for PM10.

Table 4-29 

PM2.5 (μg/m3) 1999 2000 2001 2002 2003 

98th Percentile of 24-Hr Conc. 120.0 103.0 96.0 80.4 56.0 24-Hour Design Value 104.0 90.0 76.0 

Maximum Annual Average 27.6 23.9 22.5 24.1 19.6 Annual Design Value 24.7 23.2 21.8 

File 05 Chap 4 Alm2013 p1-52.indd 32 
Chapter 4 Chapter 4

ARB Almanac 2013 – Chapter 4: Regional Trends and Forecasts 

San Joaquin Valley Air BasinNitrogen Dioxide Air Quality TrendThe San Joaquin Valley has attained the national NO2 standards 

for more than 20 years and ambient concentrations continue to be well below the level of the standard. The 1-hour design value has decreased by 41 percent since 1992 and this downward trend is expected to continue.A new national 1-hour standard was adopted by U.S. EPA in January 2010 and is intended to focus on near-road NO2 exposure. As a 

result, a new near-road monitoring network is in the process of being deployed.NO2 is formed from NOx emissions, which also contribute to ozone. 

As a result, the majority of the future emission control measures will be implemented as part of the overall ozone control strategy. Many of these control measures will target mobile sources, which account for more than three-quarters of California’s NOx emissions.

Table 4-30 

NITROGEN DIOXIDE (ppb) 1992 1993 1994 1995 1996 1997 1998 1999 Maximum 1-Hour Concentration 190 160 144 119 110 103 112 108 1-Hour Design Value 100 97 95 97 89 84 78 82 Maximum Annual Average 27 27 24 29 29 24 24 27 

File 05 Chap 4 Alm2013 p1-52.indd 33 
Chapter 4 Chapter 4

ARB Almanac 2013 – Chapter 4: Regional Trends and Forecasts 

The San Diego Air Basin lies in the southwest corner of California and comprises all of San Diego County. However, the population and emissions are concentrated mainly in the western portion of the County. The Air Basin covers 4,200 square miles, includes about eight percent of the State’s population, and produces about five percent of the State’s NOx emissions and five percent of the State’s 

PM2.5 emissions. Because of its southerly location and proximity 

to the ocean, much of the San Diego Air Basin has a relatively mild climate. Higher temperatures and seasonal variations are experienced further inland.Air quality in the San Diego Air Basin is impacted not only by local emissions, but also by pollutants transported from other areas — in particular, ozone and ozone precursor emissions transported from the South Coast Air Basin and Mexico.

San Diego Air BasinIntroduction - Area Description

File 05 Chap 4 Alm2013 p1-52.indd 34 
Chapter 4 Chapter 4

ARB Almanac 2013 – Chapter 4: Regional Trends and Forecasts 

San Diego Air Basin Emissions (tons/day, annual average)

Pollutant 2000 2005 2010 2015 2020 2025 2030 2035VOC 198 160 139 119 114 111 111 111

NOX 202 155 120 90 68 56 51 49

SOX 33211112

DPM 43211111PM2.5 26 25 23 19 19 20 20 21

PM10 76 80 78 73 74 75 76 77NH3 16 15 15 14 14 14 14 14

Emissions of NOx and VOC in the San Diego Air Basin have been 

following the declining statewide trends since 2000. These trends are largely due to motor vehicle controls and reductions in evaporative emissions. Mobile sources (both on-road and other) are by far the largest contributors to NOx and VOC emissions in the San Diego Air 

Basin. The majority of the PM10 and PM2.5 emissions are from areawide sources. 

San Diego Air BasinEmission Trends and ForecastsTable 4-31 

File 05 Chap 4 Alm2013 p1-52.indd 35 
Chapter 4 Chapter 4

ARB Almanac 2013 – Chapter 4: Regional Trends and Forecasts 

San Diego Air BasinOzone Precursor Emission - Trends and ForecastsEmissions of the ozone precursors NOx and VOC have been decreasing overall since 2000. These decreases are mostly due to decreased 

emissions from motor vehicles, brought about by stricter motor vehicle emission standards. Stationary and area-wide source emisNOx Emission Trends (tons/day, annual average)

Emission Source 2000 2005 2010 2015 2020 2025 2030 2035All Sources 202 155 120 90 68 56 51 49

Stationary Sources 13 7 7 4 4 4 5 5Area-wide Sources 33333333On-Road Mobile 144 109 79 55 37 27 23 20 Gasoline Vehicles 90 52 38 25 17 13 10 8 Diesel Vehicles 53 57 42 30 20 14 13 12Other Mobile 42 37 32 28 24 22 21 21

 Gasoline Fuel 55444444 Diesel Fuel 30 25 21 17 13 11 11 10 Other Fuel 77677777

0

20406080

100120140160

2000 2005 2010 2015 2020 2025 2030 2035

Annual Average (tons/day) 

NOx Emission Trends 

Stationary Sources Area-wide Sources On-Road Mobile Other Mobile

Figure 4-37 

Table 4-33 

File 05 Chap 4 Alm2013 p1-52.indd 36 
Chapter 4 Chapter 4

ARB Almanac 2013 – Chapter 4: Regional Trends and Forecasts 

Direct emissions of PM2.5 decreased steadily in the San Diego 

Air Basin between 2000 and 2010 and are projected to increase slightly after 2020.Particulate matter can be directly emitted into the air (primary PM) or, similar to ozone, it can be formed in the atmosphere (secondary PM) from the reaction of gaseous precursors such as NOx, SOx, VOC, 

and ammonia. The PM2.5 emission inventory includes only directly 

emitted particulate emissions.

San Diego Air BasinDirectly Emitted PM2.5 Emission - Trends and Foreca

File 05 Chap 4 Alm2013 p1-52.indd 37 
Chapter 4 Chapter 4

ARB Almanac 2013 – Chapter 4: Regional Trends and Forecasts 

San Diego Air BasinDiesel PM Emission - Trends and ForecastsDiesel PM emissions decreased from 2000 to 2010 primarily as a result of reduced exhaust emissions from diesel mobile sources. Emissions from diesel mobile sources are projected to continue to decrease through 2035.

File 05 Chap 4 Alm2013 p1-52.indd 38 
Chapter 4 Chapter 4

ARB Almanac 2013 – Chapter 4: Regional Trends and Forecasts 

Ammonia emissions remain fairly flat from 2000 through 2035 in the San Diego Air Basin. The majority of the emissions are from areawide sources such as livestock waste and pesticide usage. Most of the remaining ammonia emissions are from on-road mobile sources.San Diego Air BasinAmmonia Emission - Trends and Forecasts

File 05 Chap 4 Alm2013 p1-52.indd 39 
Chapter 4 Chapter 4

ARB Almanac 2013 – Chapter 4: Regional Trends and Forecasts 

San Diego Air BasinOzone Air Quality TrendBoth the design value and the number of days above the national ozone standard have decreased substantially over the last 20 years. The 8-hour ozone design value shows an overall decline of 31 percent from 1992 to 2012. There were 105 national 8-hour standard exceedance days during 1992, compared with 10 during 2012, representing a decrease of 88 percent in the three-year average of the national 8-hour exceedance days. Today, 97 percent of the population live in 

areas meeting the standard.

San Diego County is nonattainment for the 0.075 ppm 8-hour ozone standard. The region met the level of the previous 0.08 ppm 8-hour ozone standard in 2011 resulting in the U.S. EPA issuing a Clean Data Finding and redesignating San Diego to attainment for the 0.08 ppm 8-hour ozone standard on July 5, 2013. Current ARB and local programs will provide the continuing reductions in NOx and 

VOCs required to bring San Diego County into attainment of the 0.075 ppm standard.

OZONE (ppm) 1992 1993 1994 1995 1996 1997 1998 1999 20Annual 4th High 8-Hour 0.110 0.112 0.107 0.107 0.099 0.093 0.114 0.092 0.08-Hour Design Value 0.118 0.112 0.109 0.108 0.104 0.099 0.102 0.099 0.Maximum 1-Hour Concentration 0.170 0.187 0.147 0.162 0.138 0.136 0.164 0.124 0.1-Hour Design Value1 0.170 0.154 0.150 0.146 0.141 0.137 0.133 0.131 0.

Days Above Nat. 8-Hour Standard 105 91 90 94 64 43 58 44 

Table 4-38 1 The national 1-Hour standard has been revoked. Current and historical 1-Hour data are provided for reference.

File 05 Chap 4 Alm2013 p1-52.indd 40 
Chapter 4 Chapter 4

ARB Almanac 2013 – Chapter 4: Regional Trends and Forecasts 

San Diego Air BasinPM2.5 Air Quality TrendThe San Diego Air Basin currently meets both the national annual PM2.5 standard of 15 μg/m3 and the 24-hour PM2.5 standard of 

35 μg/m3. San Diego Air Basin has seen a 42 percent decrease in the 

24-hour PM2.5 design value since 2001. San Diego’s annual design 

value has also decreased 26 percent since 2001.The San Diego Air Basin also attains the national 24-hour standard for PM10.

Table 4-39 

PM2.5 (μg/m3) 1999 2000 2001 2002 2003 

98th Percentile of 24-Hr Conc. 45.1 48.7 40.8 39.3 46.9 24-Hour Design Value 45.0 43.0 41.0 Maximum Annual Average 18.0 15.8 17.7 16.0 15.5 Annual Design Value 17.1 16.4 15.9 

File 05 Chap 4 Alm2013 p1-52.indd 41 
Chapter 4 Chapter 4

ARB Almanac 2013 – Chapter 4: Regional Trends and Forecasts 

San Diego Air BasinNitrogen Dioxide Air Quality TrendThe San Diego Air Basin attains the national NO2 standard. Since 

1990, ambient concentrations have been well below the levels of the national 1-hour and annual average standards. Data show that the 1-hour design value decreased nearly 38 percent from 1992 to 2011.A new national 1-hour standard was adopted by U.S. EPA in January 2010 and is intended to focus on near-road NO2 exposure. As a 

result, a new near-road monitoring network is in the process of being deployed.Because NOx emissions contribute to ozone, as well as to NO2, many 

of the ozone control measures help reduce ambient NO2 concentrations. Furthermore, NOx emission controls are a critical part of the 

ozone control strategy. As a result, these controls should ensure continued attainment of the national NO2 standard. 

Table 4-40 

NITROGEN DIOXIDE (ppb) 1992 1993 1994 1995 1996 1997 1998 1999 Maximum 1-Hour Concentration 190 130 157 140 124 142 132 172 1-Hour Design Value 120 109 104 99 95 94 88 91 Maximum Annual Average 27 23 24 26 22 24 23 26 

File 05 Chap 4 Alm2013 p1-52.indd 42 
Chapter 4 Chapter 4

ARB Almanac 2013 – Chapter 4: Regional Trends and Forecasts 

(This page intenti

File 05 Chap 4 Alm2013 p1-52.indd 43 
Chapter 4 Chapter 4

ARB Almanac 2013 – Chapter 4: Regional Trends and Forecasts 

Located in the northern portion of the Central Valley, the Sacramento Metropolitan Area is home to California’s capital. This area includes the southern part of the Sacramento Valley Air Basin as well as the western portion of El Dorado County and the western and central portions of Placer County. The Sacramento Metropolitan Area occupies 5,602 square miles and has a population of more than two million people, or just over six percent of the State’s population. This area produces about five percent of the State’s NOx emissions and 

six percent of the State’s PM2.5 emissions.

Because of its inland location, the climate of the Sacramento Metropolitan Area is more extreme than that of the San Francisco Bay Area or South Coast air basins. The winters are generally cool and wet, while the summers are hot and dry.Emissions from the urbanized portion (Sacramento, Yolo, Solano, and Placer Counties) dominate the emission inventory for the Sacramento Metropolitan Area, and on-road motor vehicles are the primary source of emissions.

Sacramento Metropolitan AreaIntroduction - Area Description

File 05 Chap 4 Alm2013 p1-52.indd 44 
Chapter 4 Chapter 4

ARB Almanac 2013 – Chapter 4: Regional Trends and Forecasts 

The emission levels in the Sacramento Metropolitan Area are trending downward from 2000 to 2035 for NOx and VOC. The decreases 

in NOx and VOC are largely due to motor vehicle controls and 

reductions in evaporative emissions. Mobile sources are by far the largest contributors to NOx and VOC emissions in the Sacramento 

Metropolitan Area. PM2.5 emissions decrease slightly from 2000 to 

2035 while PM10 emissions remain constant The emission levels for 

SOx are also fairly flat from 2000 to 2035.

Sacramento Metropolitan AreaEmission Trends and Forecasts

Sacramento Metropolitan Area Emissions (tons/day, annual average)

Pollutant 2000 2005 2010 2015 2020 2025 2030 2035VOC 158 126 110 99 94 93 95 94

NOX 187 165 118 96 74 62 57 54

SOX 33222222DPM 44211111PM2.5 32 28 24 25 25 25 26 27

PM10 86 83 80 83 84 84 86 87NH3 28 28 28 28 28 28 28 28

Table 4-41 

File 05 Chap 4 Alm2013 p1-52.indd 45 
Chapter 4 Chapter 4

ARB Almanac 2013 – Chapter 4: Regional Trends and Forecasts 

Sacramento Metropolitan AreaOzone Precursor Emission - Trends and ForecastsEmissions of NOx decreased from 2000 to 2010 and are projected 

to continue decreasing from 2010 to 2035. On-road motor vehicles and other mobile sources are by far the largest contributors to NOx

emissions. More stringent mobile source emission standards and 

NOX Emission Trends (tons/day, annual average)

Emission Sources 2000 2005 2010 2015 2020 2025 2030 2035All Sources 187 165 118 96 74 62 57 54

Stationary Sources 16 13 12 13 12 13 13 13Area-wide Sources 65566666On-Road Mobile 118 103 72 50 34 24 21 19 Gasoline Vehicles 68 42 31 20 14 10 8 7 Diesel Vehicles 51 61 41 30 19 14 13 12Other Mobile 47 43 30 27 23 19 17 15

 Gasoline Fuel 33333333 Diesel Fuel 42 37 24 21 17 14 11 10 Other Fuel 32233333

0

20406080

100120

140

2000 2005 2010 2015 2020 2025 2030 2035

Annual Average (tons/day) 

NOX Emission Trends 

Stationary Sources Area-wide Sources On-Road Mobile Other Mobile

Figure 4-47 

Table 4-43 

File 05 Chap 4 Alm2013 p1-52.indd 46 
Chapter 4 Chapter 4

ARB Almanac 2013 – Chapter 4: Regional Trends and Forecasts 

Direct emissions of PM2.5 have steadily declined in the Sacramento 

Metropolitan Area between 2000 and 2010 and then are projected to increase very slightly through 2035. Emissions are dominated by contributions from area-wide sources, primarily fugitive dust from paved and unpaved roads, fugitive dust from construction and demolition, particulates from residential fuel combustion (including wood), and waste burning. Emissions of directly emitted PM2.5 from mobile 

sources and stationary sources in the Sacramento Metropolitan Area have remained relatively steady. Particulate matter can be directly emitted into the air (primary PM) or, similar to ozone, it can be formed in the atmosphere (secondary PM) from the reaction of gaseous precursors such as NOx, SOx, ROG, 

and ammonia. The PM2.5 emission inventory includes only directly 

emitted particulate emissions.

Sacramento Metropolitan AreaDirectly Emitted PM2.5 Emission - Trends and Foreca

File 05 Chap 4 Alm2013 p1-52.indd 47 
Chapter 4 Chapter 4

ARB Almanac 2013 – Chapter 4: Regional Trends and Forecasts 

Sacramento Metropolitan AreaDiesel PM Emission - Trends and ForecastsDiesel PM emissions decreased from 2000 to 2010 primarily as a result of reduced exhaust emissions from diesel mobile sources. Emissions from diesel mobile sources are projected to continue to decrease through 2035.

File 05 Chap 4 Alm2013 p1-52.indd 48 
Chapter 4 Chapter 4

ARB Almanac 2013 – Chapter 4: Regional Trends and Forecasts 

Ammonia emissions are projected to remain fairly constant in the Sacramento Metropolitan Area. These emissions are dominated by area-wide sources such as livestock waste and pesticide usage. Other contributors of ammonia emissions are stationary sources and onroad mobile source.Sacramento Metropolitan AreaAmmonia Emission - Trends and Forecasts

File 05 Chap 4 Alm2013 p1-52.indd 49 
Chapter 4 Chapter 4

ARB Almanac 2013 – Chapter 4: Regional Trends and Forecasts 

Sacramento Metropolitan AreaOzone Air Quality TrendSince 1992, the 8-hour design value decreased approximately 10 percent. Although the trend is more variable for the number of days above the national standards. The three-year average of the national 8-hour exceedance days has declined nearly 45 percent since 1992. Additionally, the population living in areas below the standard has increased from five percent in 1992 to 36 percent in 2011.In March 2009, ARB approved the 2009 Sacramento Regional 8-Hour Ozone Attainment and Reasonable Further Progress Plan. This plan sets out a strategy for attaining the 1997 federal 8-hour ozone standard in the Sacramento Nonattainment Area by 2018. By 2016, the District will submit a new plan demonstrating how the region will meet the 8-hour ozone standard of 0.075 ppm by 2032. U.S. EPA finalized a “clean data determination” for the 1-hour ozone standard for the Sacramento Metropolitan Area on October 3, 2012.

OZONE (ppm) 1992 1993 1994 1995 1996 1997 1998 1999 20Annual 4th High 8-Hour 0.111 0.103 0.106 0.111 0.104 0.092 0.115 0.106 0.18-Hour Design Value 0.105 0.110 0.104 0.106 0.106 0.099 0.103 0.103 0.1Maximum 1-Hour Concentration 0.170 0.150 0.145 0.156 0.157 0.145 0.163 0.160 0.11-Hour Design Value1 0.160 0.150 0.142 0.145 0.145 0.145 0.149 0.149 0.1

Days Above Nat. 8-Hour Standard 90 48 73 64 76 45 60 80 

Table 4-48 1 The national 1-Hour standard has been revoked. Current and historical 1-Hour data are provided for reference.

File 05 Chap 4 Alm2013 p1-52.indd 50 
Chapter 4 Chapter 4

ARB Almanac 2013 – Chapter 4: Regional Trends and Forecasts 

Sacramento Metropolitan AreaPM2.5 Air Quality TrendThe Sacramento Metropolitan Area has seen significant progress in both the 24-hour and annual average PM2.5 design values over the 

last 13 years. The Sacramento Metropolitan Area is in attainment of the national annual average PM2.5 standard and concentrations have 

decreased 20 percent since 2001. The 24-hour design value has seen the biggest decline over the past 14 years, decreasing 51 percent.Although the Sacramento Metropolitan Area is designated as nonattainment for the 24-hour national PM2.5 standard, recent monitoring data now shows that the Sacramento Metropolitan Area meets the 

24-hour national PM2.5 standard. U.S. EPA finalized a “clean data 

determination” for the 24-hour PM2.5 standard for the Sacramento 

Metropolitan Area on July 15, 2013.The Sacramento Metropolitan Area also currently attains the national 24-hour standard for PM10. 

Table 4-49 

PM2.5 (μg/m3) 1998 1999 2000 2001 2002 

98th Percentile of 24-Hr Conc. 96 84 81 53 63 24-Hour Design Value 72 68 60 Maximum Annual Average 19.9 12.3 11.9 14.3 Annual Design Value 12.5 12.4 

File 05 Chap 4 Alm2013 p1-52.indd 51 
Chapter 4 Chapter 4

ARB Almanac 2013 – Chapter 4: Regional Trends and Forecasts 

Sacramento Metropolitan AreaNitrogen Dioxide Air Quality TrendThe Sacramento Metropolitan Area has attained the national NO2

standard for more than 20 years. The 2011 1-hour design value has declined by 43 percent from 1992 levels. The Sacramento Metropolitan Area shows more variability in maximum 1-hour concentrations than other areas of the State. This variability may be due to changes in emission sources and may also reflect year-to-year changes in meteorology. However, ambient concentrations are well below the level of both standards.A new national 1-hour standard was adopted by U.S. EPA in January 2010 and is intended to focus on near-road NO2 exposure. As a 

result, a new near-road monitoring network is in the process of being deployed.NO2 is formed from NOx emissions, which also contribute to ozone. 

As a result, the majority of the future emission control measures will be implemented as part of the overall ozone control strategy. Many of these control measures will target mobile sources, which account for more than three-quarters of California’s NOx emissions.

Table 4-50 

NITROGEN DIOXIDE (ppb) 1992 1993 1994 1995 1996 1997 1998 1999 Maximum 1-Hour Concentration 190 120 111 99 145 92 101 110 1-Hour Design Value 90 90 83 80 78 75 72 71 Maximum Annual Average 21 22 22 22 22 19 21 21 

File 05 Chap 4 Alm2013 p1-52.indd 52