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Acid Rain - Are Efforts To Reduceacid Rain Working?

emissions figure nitrogen annual

The Good News

During the years since the enactment of the Acid Rain Program, much progress has been made in reducing power plant emissions across the nation, particularly in the Ohio Valley and the Northeast, where emissions have been historically highest. Figure 9.6 shows the average sulfur dioxide emissions from power plants by state for the year 1990 and for the two phases of the Program.

Figure 9.7 and Figure 9.8 present average power plant emissions of nitrogen oxide for the same time periods. Here one sees that the areas showing the most improvement are the Ohio Valley and the state of Texas.

According to the EPA's Acid Rain Program, 2003 Progress Report, great improvement has been made in reducing the pollutants that cause acid deposition. Sulfur dioxide emissions from power plants were reduced 38% between 1980 and 2003, though emissions were up slightly from 2002 to 2003. (See Figure 9.9.) Power plant emissions of nitrogen oxides over the period 1990–2003 were reduced 37%, from 6.7 million tons to 4.2 million tons. (See Figure 9.7.)

In 2003, the fourth year of the Acid Rain Program's Phase II implementation, all but one of the 3,497 Phase II affected utility units complied with the requirements to hold sufficient allowances to cover their sulfur dioxide emissions.

These reductions are even more encouraging in light of increased economic activity. The reduced sulfur and nitrogen oxide rates were achieved during a period of economic growth in which the amount of fuel burned to produceelectricityincreasedby28%.WithouttheAcid Rain Program's mandated reductions in emission rates, both sulfur dioxide and nitrogen oxide emissions from power plants would have been expected to rise in most parts of the nation as fossil fuel use rose. The fact that utility plant emissions of these pollutants have declined in the face of rising electrical production is very encouraging.

This news is offset somewhat by the contents of a report published by the U.S. Government Accountability Office, Air Pollution, Meeting the Future Electricity Demand Will Increase Emissions of Some Harmful Substances (October 2002). The report presents a forecast of energy requirements that was prepared by the Energy Information Administration. By the year 2020 electricity generation is expected to have risen by 42%. Emissions of pollutants by electric utilities are also expected to rise over this period. The good news in the report was that acid deposition producing pollutants were not expected to rise despite a significant increase in the production of electricity. Figure 9.10 presents pollution emissions by type that were projected to accompany the rise in electricity generation.

The Bad News

Important reductions in the emissions of acid rain producing pollutants have been documented. However, the ground-level data being collected on actual acid deposition has provided a somewhat less optimistic assessment. The Clean Air Status and Trends Network (CASTNET) is a scientific monitoring network established by the EPA under a mandate set forth in the 1990 Clean Air Act Amendments. FIGURE 9.6
State-by-state sulfur dioxide emissions levels, 1990–2003
SOURCE: "Figure 4. State by State SO2 Emissions Levels," in Acid Rain Program 2003 Progress Report, U.S. Environmental Protection Agency, September 2004, http://www.epa.gov/airmarkets/cmprpt/arp03/2003report.pdf (accessed April 14, 2005)
The network is operated jointly by the EPA and the National Park Service.

In Clean Air Status and Trends Network 2002 Annual Report (November 2003), CASTNET presents data on the concentrations of sulfate and nitrogen particulates in the precipitation that has fallen on eastern states over the period 1990–2002. These data differ from the emissions data seen earlier. The power plant emissions of these two chemicals are down over the period in question. Their concentrations in precipitation are also down, but only slightly.

Figure 9.11, Figure 9.12, Figure 9.13, and Figure 9.14 present the sulfur particulate concentrations in precipitation collected by CASTNET in their eastern collection sites. Sulfate (SO42−) concentrations were down between 1990 and 2002, but by less than sulfate dioxide (SO2) emissions were over the same period.

Nitrate (NO3) concentrations presented for the same geographical area and time frame showed a more discouraging result. Figure 9.15 and Figure 9.16 show that nitrate concentrations in the eastern states showed no real decline over the period 1990–2001 despite declining utility plant emissions of nitrogen oxides over the period. Here again, the fact that nitrogen oxide emissions are down from sources participating in the Acid Rain Program does not mean that all human-made emissions are down.

Rising Nitrogen Oxide Emissions

A detailed analysis of the nitrogen oxide emissions data presented for all sources of emissions in the EPA's report National Air Quality and Emissions Trends Report 1999 (March 2001) shows clearly that total nitrogen oxide emissions were higher in 1999 than in 1970, 1980, and 1990.

FIGURE 9.7
Nitrogen oxide emissions under the Acid Rain Program, 1990–2003
SOURCE: "Figure 9. NOX Emissions under the Acid Rain Program," in Acid Rain Program 2003 Progress Report, U.S. Environmental Protection Agency, September 2004, http://www.epa.gov/airmarkets/cmprpt/arp03/2003report.pdf (accessed April 14, 2005)

Nitrogen oxide emissions from transportation sources were responsible for the greatest portion of the increase between 1970 and 1999, rising from 9.3 million short tons to 14.1, an increase of nearly 52%. The transportation category is divided into two sections, on-road vehicles and non-road engines and vehicles. The on-road portion rose but at a much slower pace than the non-road portion. On-road vehicle emissions, which include all automobiles and trucks, rose from 7.4 million short tons in 1970 to 8.6 million short tons in 1999, an increase of 16%. The non-road engine and vehicle category includes recreational vehicles, construction machinery, lawn and garden equipment, airplanes, railroad machinery, and marine vessels. This category rose from 1.9 million short tons in 1970 to 5.5 million in 1999, an increase of 189%. Nitrogen oxide emissions from fuel combustion sources, the second largest category in 1999, remained statistically unchanged over the period.

The Acid Rain Program had greater success in stemming sulfur dioxide emissions than it had, as of 1999, in stemming nitrogen oxide emissions.

A 1999 Assessment

In April 1999 the National Acid Precipitation Assessment Program released findings from the study National Acid Precipitation Assessment Program Biennial Report to Congress: An Integrated Assessment. The study warned that, despite important strides in reducing air pollution, acid deposition remains a serious problem in sensitive areas and provided more evidence that acid deposition is more "complex and intractable than was believed ten years ago." Among the findings were:

  • New York's Adirondack Mountain waterways suffer from serious levels of acid. Even though sulfur levels are declining, nitrogen levels are still climbing. The agency predicted that by 2040, about half the region's 2,800 lakes and ponds would be too acidic to sustain life.
  • Chesapeake Bay is suffering from excess nitrogen, which is causing algae blooms that can suffocate other life forms.
  • High elevation forests in Colorado, West Virginia, Tennessee, and Southern California are nearly saturated with nitrogen, a key ingredient in acid deposition. (Nitrogen saturation is a condition where the nitrogen levels in the soil exceed the plant needs with the result that excess nitrogen is flushed into streams where it can cause undesirable plant growth. As the nitrogen moves through the soil it strips away chemicals essential for forest fertility, increasing lake and stream acidity).
  • High elevation lakes and streams in the Sierra Nevada, the Cascades, and the Rocky Mountains may be on the verge of "chronically high acidity."

In conclusion, the report recognized the important strides made in reducing sulfur dioxide emissions since passage of the 1990 Clean Air Act Amendments. However, the slow recovery that was being recorded in lakes, streams, and forests indicated that further reductions in sulfur and nitrogen were necessary.

Anticipated Benefits of Further Abatement

There are many anticipated benefits of recovering from the effects of acid rain. Table 9.3 summarizes some of them. The benefits to human health are believed to be reduced illness and death from lung disorders and heart disease, resulting in decreased need for medical services and medical treatment. Aquatic systems and forests are expected to experience less stress, thereby preserving vital habitat and resources important to the nation's economy. In some locations, the return of badly damaged ecosystems to healthy, thriving ecosystems is another anticipated benefit.

Reduced destruction of human-made objects is also a potential benefit of further abatement of acid deposition. The reduced deterioration of vehicles, buildings, monuments, and other structures should reduce the costs that society has to pay to repair and correct destruction of this kind, and a reduction in damage and loss of cultural objects preserves our heritage for future generations.

Taken together, the overall benefits of further reducing acid deposition should be a healthier, more environmentally sound habitat for people and all living organisms.

FIGURE 9.8
State-by-state nitrogen oxide emissions levels, 1990–2003
SOURCE: "Figure 10. State by State NOX Emissions Levels," in Acid Rain Program 2003 Progress Report, U.S. Environmental Protection Agency, September 2004, http://www.epa.gov/airmarkets/cmprpt/arp03/2003report.pdf (accessed April 14, 2005)

FIGURE 9.9
Sulfur dioxide emissions under the Acid Rain Program, 1980–2003
SOURCE: "Figure 1. SO2 Emissions under the Acid Rain Program," in Acid Rain Program 2003 Progress Report, U.S. Environmental Protection Agency, September 2004, http://www.epa.gov/airmarkets/cmprpt/arp03/2003report.pdf (accessed April 14, 2005)

FIGURE 9.10
Projected percentage change in emissions by electric utilities, by pollutant, 2000–20
SOURCE: Adapted from "Figure 7. Percent Change in Emissions under Three Scenarios, 2000–2020," in Air Pollution: Meeting Future Electricity Demand Will Increase Emissions of Some Harmful Substance s, U.S. General Accounting Office, October 2002

FIGURE 9.11
Annual mean SO2 concentrations (µg/m3), 2002
SOURCE: "Figure 2-1. Annual Mean SO2 Concentrations (µg/m3) for 2002," in Clean Air Status and Trends Network (CASTNET) 2002 Annual Report, U.S. Environmental Protection Agency, Office of Atmospheric Programs, November 2003, http://www.epa.gov/castnet/library/annual02.html (accessed April 14, 2005)

FIGURE 9.12
Trends in annual SO2concentrations ( μg/m3) in eastern states, 1990–2002
SOURCE: "Figure 2-2. Trend in Annual SO2 Concentrations (µg/m3)—Eastern United States," in Clean Air Status and Trends Network (CASTNET) 2002 Annual Report, U.S. Environmental Protection Agency, Office of Atmospheric Programs, November 2003, http://www.epa.gov/castnet/library/annual02.html (accessed April 14, 2005)

FIGURE 9.13
Annual mean SO2−4 concentrations (µg/m3), 2002
SOURCE: "Figure 2-3. Annual Mean SO2−4 Concentrations (µg/m3) for 2002," in Clean Air Status and Trends Network (CASTNET) 2002 Annual Report, U.S. Environmental Protection Agency, Office of Atmospheric Programs, November 2003, http://www.epa.gov/castnet/library/annual02.html (accessed April 14, 2005)

FIGURE 9.14
Trends in annual SO2−4concentrations ( μg/m3) in eastern states, 1990–2002
SOURCE: "Figure 2-4. Trend in Annual SO2−4 Concentrations (µg/m3)—Eastern United States," in Clean Air Status and Trends Network (CASTNET) 2002 Annual Report, U.S. Environmental Protection Agency, Office of Atmospheric Programs, November 2003, http://www.epa.gov/castnet/library/annual02.html (accessed April 14, 2005)

FIGURE 9.15
Trends in annual NO3 concentrations ( μg/m3) in eastern states, 1990–2002
SOURCE: "Figure 2-8. Trend in Annual NO3− Concentrations (μg/m3)—Eastern United States," in Clean Air Status and Trends Network (CASTNET) 2002 Annual Report, U.S. Environmental Protection Agency, Office of Atmospheric Programs, November 2003, http://www.epa.gov/castnet/library/annual02.html (accessed April 14, 2005)

FIGURE 9.16
Trends in annual NH+4 concentrations (μg/m3) in eastern states, 1990–2002
SOURCE: "Figure 2-12. Trend in Annual NH+4 Concentrations (μg/m3)—Eastern United States," in Clean Air Status and Trends Network (CASTNET) 2002 Annual Report, U.S. Environmental Protection Agency, Office of Atmospheric Programs, November 2003, http://www.epa.gov/castnet/library/annual02.html (accessed April 14, 2005)

TABLE 9.3
Effect of acid rain on human health and selected ecosystems and anticipated recovery benefits
SOURCE: Adapted from "Appendix I. Effect of Acid Rain on Human Health and Selected Ecosystems and Anticipated Recovery Benefits," in Acid Rain: Emissions Trends and Effects in the Eastern United States, U.S. General Accounting Office, March 2000

Human health and ecosystem Effects Recovery benefits
Human health In the atmosphere, sulfur dioxide and nitrogen oxides become sulfate and nitrate aerosols, which increase morbidity and mortality from lung disorders, such as asthma and bronchitis, and impacts to the cardiovascular system. Decrease emergency room visits, hospital admissions, and deaths.
Surface waters Acidic surface waters decrease the survivability of animal life in lakes and streams and in the more severe instances eliminate some or all types of fish and other organisms. Reduce the acidic levels of surface waters and restore animal life to the more severely damaged lakes and streams.
Forests Acid deposition contributes to forest degradation by impairing trees' growth and increasing their susceptibility to winter injury, insect infestation, and drought. It also causes leaching and depletion of natural nutrients in forest soil. Reduce stress on trees, thereby reducing the effects of winter injury, insect infestation, and drought, and reduce the leaching of soil nutrients, thereby improving overall forest health.
Materials Acid deposition contributes to the corrosion and deterioration of buildings, cultural objects, and cars, which decreases their value and increases costs of correcting and repairing damage. Reduce the damage to buildings, cultural objects, and cars, and reduce the costs of correcting and repairing future damage.
Visibility In the atmosphere, sulfur dioxide and nitrogen oxides form sulfate and nitrate particles, which impair visibility and affect the enjoyment of national parks and other scenic views. Extend the distance and increase the clarity at which scenery can be viewed, thus reducing limited and hazy scenes and increasing the enjoyment of national parks and other vistas.
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