Effects On Soil

Acid precipitation can affect soil chemistry, leaching, and microbiological processes. In addition, various types of soils exhibit a range of sensitivities to the effects of acid rain; for example, some soils are more sensitive than others. Factors influencing soil sensitivity to acidification include the lime capacity, soil profile buffer capacity, and water-soil reactions (Bache 1980). Wiklander (1980) reviews the sensitivity of various soils, and Peterson (1980) identifies soil orders and classifications according to their response to acid precipitation.

Two important effects of acid precipitation on soil are associated with changes in the leaching patterns of soil constituents and with the potential removal and subsequent leaching of chemical constituents in the precipitation. For example, Cronan (1981) describes the results of an investigation of the effects of regional acid precipitation on forest soils and watershed biogeochemistry in New England. Key findings include the following:

1. Acid precipitation can cause increased aluminum mobilization and leaching from soils to sensitive aquatic systems

2. Acid deposition can shift the historic carbonic acid/organic acid leaching regime in forest soils to one dominated by atmospheric H2SO4

3. Acid precipitation can accelerate nutrient cation leaching from forest soils and can pose a threat to the potassium resources of northeastern forested ecosystems

4. Progressive acid dissolution of soils in the laboratory is an important tool for predicting the patterns of aluminum leaching from soils exposed to acid deposition.

Soil microorganisms and microbiological processes can be altered by acid precipitation. The effects of acid precipitation include changes in bacterial numbers and activity, alterations in nutrient and mineral cycling, and changes in the decomposition of organic matter.

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