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FIGURE 4-12. PM10 emissions from 1993 to 2002. (From EPA, Latest Findings on National Air Quality 2002 Status and Trends, Office of Air Quality Planning and Standards, U.S. Environmental Protection Agency, U.S. Government Printing Office, Washington, D.C., August 2003.)

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Fuel Combustion H Industrial Processes ^Transportation

93 94 95 96 97 98 99 00 01 02 1993-02: 17% decrease

FIGURE 4-13. Direct PM2.5 emissions from 1993 to 2002. (From EPA, Latest Findings on National Air Quality 2002 Status and Trends, Office of Air Quality Planning and Standards, U.S. Environmental Protection Agency, U.S. Government Printing Office, Washington, D.C., August 2003.)

Carbon Monoxide

Carbon monoxide (CO) is a component of motor vehicle exhaust, which contributes about 60% of all CO emissions nationwide. Other sources of CO emissions include industrial processes, nontransportation fuel combustion, and natural sources such as wildfires. Nationally, the 2002 ambient average CO concentration was nearly 65% lower than that for 1983, which is illustrated in Figure 4-14 [62]. CO emissions decreased about 42% over the last 10 years despite an approximately 23% increase in vehicle miles traveled. Transportation sources are the largest contributors to CO emissions, with fuel combustion accounting for about 7% of the CO emissions. Electric utilities account for less than 0.5% of the total CO emissions [4]. The trend in CO emissions is shown in Figure 4-15 [62].

Lead

In the past, automotive sources were the major contributor of lead (Pb) emissions to the atmosphere. The emissions of lead from the transportation sector have greatly declined over the last 20 years as leaded gasoline was phased out. Today, industrial processes, primarily metals processing, are the major sources of lead emissions to the atmosphere. As a result of the phase-out

1983-02: 65% decrease 1993-02: 42% decrease

FIGURE 4-14. CO air quality from 1983 to 2002. (From EPA, Latest Findings on National Air Quality 2002 Status and Trends, Office of Air Quality Planning and Standards, U.S. Environmental Protection Agency, U.S. Government Printing Office, Washington, D.C., August 2003.)

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FIGURE 4-14. CO air quality from 1983 to 2002. (From EPA, Latest Findings on National Air Quality 2002 Status and Trends, Office of Air Quality Planning and Standards, U.S. Environmental Protection Agency, U.S. Government Printing Office, Washington, D.C., August 2003.)

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1983-02: 41% change 1993-02: 21% increase

FIGURE 4-15. CO emissions from 1983 to 2002. (From EPA, Latest Findings on National Air Quality 2002 Status and Trends, Office of Air Quality Planning and Standards, U.S. Environmental Protection Agency, U.S. Government Printing Office, Washington, D.C., August 2003.)

1983-02: 94% decrease 1993-02: 57% decrease

FIGURE 4-16. Lead air quality from 1983 to 2002. (From EPA, Latest Findings on National Air Quality 2002 Status and Trends, Office of Air Quality Planning and Standards, U.S. Environmental Protection Agency, U.S. Government Printing Office, Washington, D.C., August 2003.)

1983-02: 94% decrease 1993-02: 57% decrease

FIGURE 4-16. Lead air quality from 1983 to 2002. (From EPA, Latest Findings on National Air Quality 2002 Status and Trends, Office of Air Quality Planning and Standards, U.S. Environmental Protection Agency, U.S. Government Printing Office, Washington, D.C., August 2003.)

of leaded gasoline, lead concentrations and emissions have decreased significantly, as shown in Figures 4-16 and 4-17, respectively [62]. The 2002 average air quality concentration for lead is 94% lower than in 1982, and lead emissions decreased by 93% over the same period. Lead emissions from electric utilities are less than 10% of the total (i.e., less than 500 short tons [4]), and the only violations of the lead NAAQS that occur today are near large industrial sources such as lead smelters and battery manufacturers [62].

Acid Rain

As discussed earlier, acid rain or acidic deposition occurs when emissions of sulfur dioxide and nitrogen oxides in the atmosphere react with water, oxygen, and oxidants to form acidic compounds. These compounds then fall to Earth in either dry form (gas and particles) or wet form (rain, snow, and fog). In the United States, about 63% of annual SO2 emissions and 22% of NOZ emissions are produced by electric utility plants that burn fossil fuels [62]. The EPA's Acid Rain Program will reduce annual SO2 emissions by 10 million short tons from 1980 levels by 2010. The program sets a permanent cap of 8.95 million short tons on the total amount of SO2 that may be emitted by power plants nationwide, which is about half of that emitted in 1980 [62]. Approximately 3000 units are now affected by the Acid

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^Fuel Combustion [v| Industrial Processes [^Transportation

1982-02: 93% decrease 1993-02: 5% decrease

FIGURE 4-17. Lead emissions from 1982 to 2002. (From EPA, Latest Findings on National Air Quality 2002 Status and Trends, Office of Air Quality Planning and Standards, U.S. Environmental Protection Agency, U.S. Government Printing Office, Washington, D.C., August 2003.)

Rain Program. Figure 4-18 shows the SO2 reductions achieved as of 2002 and illustrates that SO2 emissions were reduced to about 10 million short tons in 2002 [62]. The NOZ component of the Acid Rain Program limits the emission rate for all affected utilities, resulting in an NOx reduction of 2 million short ton from 1980 levels by 2000. NOZ emissions, shown in Figure 4-19, have declined since 1990, with NOZ emissions from ~1000 affected sources totaling slightly more than 4 million short tons in 2002 [62]. In the atmosphere, sulfate concentrations, which are a major component of fine particles, especially in eastern United States, have decreased since 1990 [19]. In 2001, concentrations in the Northeast and Mid-Atlantic were 8 to 12 mg/m3, as much as 8 mg/m3 lower than in 1990. Wet sulfate deposition, a major component of acid rain, has also decreased since 1990. In 2001, deposition in the Northeast and Midwest was 20 to 30 kg/ha/yr, as much as 12 kg/ha/yr lower than in 1990 [19]. Wet nitrate deposition has not decreased regionally because of the overall increase in NOx emissions. Acid-neutralizing capacity, a major indicator of recovery in acidified lakes and streams, is beginning to rise in streams in the Northeast, including the Adirondacks. This is an indictor that recovery from acidification is beginning in those areas.

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