Deposition rate, eastern North America

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. 

Phosphorites (manne apatites) are dense, hght-brown-to-black concretions, ranging in size from sands to nodules and irregular masses. Phosphorites have been found off Argentina, Chile, Japan, Mexico, Peru, South Africa, and Spain, and several islands in the Indian Ocean. Some also have been found off the west coast of North America and on the eastern North American continental shelf These deposits occur where water upwelling transports phosphorus and where the rate of sedimentation is slow. The... 

North America In North America, most of the northeastern United States, portions of southeastern Canada, and the western coast of the United States now receive acidic precipitation (U.S. NAPAP, 1991). The spatial distribution of volume-weighted pH for eastern and western North America is shown in Figure 20.24. Measured sulfate, nitrate, and ammonium wet deposition rates are shown in Figure 20.25. 

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