Acid deposition in eastern

As treated in other chapters of this book, air masses often transport acidic pollutants thousands of kilometres from their original source prior to deposition. Because air mass and storm movements tend to follow regular patterns, there is a strong linkage between the sources of pollutants and the areas that receive the acidic deposition. In eastern North America, the air mass movements and storm tracks are, on the average, from southwest towards the northeast. This serves to carry the emitted pollutants from the industrial "heartland over the more rural and comparatively pristine area of the northeast United States and southeastern Qmada (14). The spatial distribution of sulphate deposition over the eastern United States and Canada in 1980 is shown in Figure 4 (17). 

Emissions from U.S. sources also contribute to acidic deposition in eastern Canada, where the soil is very similar to the soil of the Adirondack Mountains, and the lakes are consequently extremely vulnerable to chronic acidification problems. The Canadian government has estimated that 14,000 lakes in eastern Canada are acidic. 

Schnoor J. L., Lee S., Nickolaidis N. P., and Nair D. R. (1986) Lake resources at risk to acid deposition in eastern United States. Water Air Soil Pollut. 31, 1091—1101. 

Since SO2 and NO2 are criteria pollutants, their emissions are regulated. In addition, for the purposes of abating acid deposition in the United States, the 1990 Clean Air Act Amendments require that nationwide SO2 and NO emissions be reduced by approximately 10 million and 2 million t/yr, respectively, by the year 2000. Reasons for these reductions are based on concerns which include acidification of lakes and streams, acidification of poorly buffered soils, and acid damage to materials. An additional major concern is that acid deposition is contributing to the die-back of forests at high elevations in the eastern United States and in Europe. 

The Eastern Canadian Acid Rain Program was highly successful at reducing SO2 emissions and sulfate wet deposition in eastern Canada (see Figure 10). Sulfur emissions actually declined more than the desired 50% by 1994, and have continued to decline modestly in the present. These SO2 emissions in the United States have also reduced dramatically, particularly since the implementation of the Canada-United States Air Quality Accord in 1991. This has been especially important to the aquatic and terrestrial ecosystems in eastern Canada, since US emissions are responsible for a large proportion of the acid deposition received in eastern Canada due to transboundary transport. 

Bashkin, V. N., Kozlov, M. YA., Golinets, O. M. (1996)c. Risk assessment of ecosystem sustainability to acid forming compounds in the North-Eastern Asia In Proceedings of International Conference on Acid Deposition in East Asia, Taipei, May 28-30, 1996, 347-356. 

In Canada, nearly 45% of the land area is considered sensitive to acid deposition. Lakes and watersheds located on the Canadian Shield are considered the most vulnerable, due to the low buffering capacity of the typically shallow soils that overlay the Shield bedrock. A large portion of eastern Canada, including much of Ontario and Quebec as well as parts of the Atlantic Provinces are underlain by silicate bedrock these areas also receive the highest levels of acid deposition in the country. 

Lucas, A.E. and Cowell, D.W. (1984). Regional assessment of sensitivity to acidic deposition for eastern Canada. In Geological Aspects of Acid Deposition (ed. by O.P. Bricker), Add Precipitation Series 7, Ann Arbor. Butterworth, Boston. 

Four general considerations argue that acid rain is a serious and even urgent problem that needs to be addressed without delay. First, the number of resources threatened by acid rain is large. About one quarter of the smrface water in the eastern U.S. — some 14,000 square miles — is moderately to highly sensitive to acid rain. In Canada, nearly 11,000 square miles of surface water are highly sensitive to acid rain. According to U.S. and Canadian estimates, the number of acidified lakes in eastern North America will double by 1990 at current rates of acid deposition. In addition, nearly 75% of the forest area in the eastern U.S. now receives at least moderately acidic deposition. 

The impact of acid deposition on forests depends on the quantity of acidic components received by the forest system, the species present, and the soil composition. Numerous studies have shown that widespread areas in the eastern portion of North America and parts of Europe are being... 

Whelpdale, D. M., and Barrie, L. A., ]. Air Water Soil Pollut. 14, 133-157 (1982). National Research Council, "Acid Deposition Atmospheric Processes in Eastern North America." National Academy Press, Washington, DC, 1983. 

Acid deposition is of greatest concern wherever there are large amounts ol lossil fuel combustion upwind of an area. Eastern North America, large areas of Europe, and eastern Asia all receive acidic deposition. Acidic deposition is especially a concern when poorly buffered soils, with little acid-neutralizing capacity, are impacted. In North America, large areas of eastern Canada, the Adirondack Mountains of upstate New York, and sections of New England all are considered acid sensitive areas, where resistant bedrocks and thin soils prevent significant neutralization of acidity. 

Acid deposition is clearly a widespread phenomenon in the eastern third of the country. 

Acid deposition is a regional problem wherever large amounts of fossil fuels are consumed. There have been significant efforts in both Europe and North America to reduce acid deposition because of its many deleterious effects. This effort has focused mainly on the reduction of SO, emissions. In the future acid deposition tvill have to be addressed in eastern Asia, where rapid industrialization and increased use of fossil fuels is likely. 

Environmental benefits of Emission Controls. Information in Figure 5 illustrate that the emission of sulphur in eastern North America has declined over the past decade. This decline allows for a possible verification of the dose-response relationships on which the environmental concerns for emissions have been based. A decline in sulphate deposition in Nova Scotia has apparently resulted in a decrease in acidity of eleven rivers over the period 1971-73 to 1981-82 (47), In the Sudbury, Ontario area where emissions have dechned by over 50% between 1974-76 and 1981-83, a resurvey of 209 lakes shows that most lakes have now become less acidic. Twenty-one lakes that had a pH < 5.5 in 1974-76 showed an average decline in acidity of 0.3 pH units over the period (48), Surveys of 54 lakes in the Algoma region of Ontario have shown a rapid response to a decline in sulphate deposition. Two lakes without fish in 1979 have recovered populations as pH of the water moved above 5.5 (49). Evidence is accumulating to support the hypothesis of benefits that were projected as a consequence of emission controls. This provides increased confidence in the projections. 

Lynch-Stewart, P. Wiken, E.B. Ironside, G. Acid Deposition on Prime Resource Lands in Eastern Canada, Canada Land Inventory Rept, No. 18, Lands Directorate, Environment Canada, Ottawa, Ontario, 1987. 

Zakshek EM, Puckett KJ, Percy KE. 1986. Lichen sulfur and lead levels in relation to deposition patterns in Eastern Canada. International Symposium on Acidic Precipitation, Muskoka. Ontario, Canada, Sept. 15-20,1985. Water Air Soil Pollut 30 161-169. 

Since environmental damage due to acid deposition has largely been limited to the eastern parts of Canada (east of the Manitoba-Ontario border) and the USA (east of the Mississippi River), most of the emission reductions have occurred in those areas. Figure 8 illustrates the SO2 emission totals in eastern Canada, eastern USA and total North America. 

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