A review
Excerpt
ACID precipitation is a major environmental issue being discussed in scientific journals and other news media. Unfortunately, acid rain and snow have been intensively studied for a relatively short time—less than 10 years in the United States. Because of the short-term records and the extreme complexity of the problem, reporting is sometimes controversial, and important discrepancies have developed within the scientific community. For example, some scientists believe that acid precipitation is causing widespread degradation of both aquatic and terrestrial ecosystems. Others are not convinced that it is more than a localized problem.
What is the problem?
In the absence of natural or man-made atmospheric pollution, the pH of rainfall is about 5.6—the equilibrium value for distilled water in the presence of atmospheric carbon dioxide. The measured pH of rainfall in the northeastern United States during the last decade averaged between 4.0 and 4.6, depending upon location (14, 26). Because pH is measured on a logarithmic scale, the hydrogen ion concentration observed in precipitation today is 6 to 40 times higher than the theoretical value that would occur at the nonpolluted pH level of 5.6.
The pH values can be misleading …
Footnotes
J. D. Helvey is project leader at the Timber and Watershed Laboratory, Forest Service, U.S. Department of Agriculture, Parsons, West Virginia 26287. Samuel H. Kunkle is program manager of the Forestry Support Program, Agency for International Development and Forest Service, U.S. Department of Agriculture, Washington, D.C. 20013. David R. DeWalle is a professor of forestry hydrology in the School of Forest Resources. The Pennsylvania State University, University Park, 16802. Use of trade, firm, or corporation names in this article is for the information and convenience of readers. Such use does not constitute official endorsement or approval by USDA or the Forest Service of any product or service to the exclusion of others that may be suitable.
- Copyright 1982 by the Soil and Water Conservation Society
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