Acid Rain: Environmental Problem of Industrialization (GC-01)
Acid rain is precipitation with a pH of less than 5.6, the normal value of an uncontaminated atmosphere. It is caused by formation of weak carbonic acid as carbon dioxide is absorbed in raindrops.

A dramatic increase in acid rain occurs downwind from manufacturing centers, coal- and oil-fired power plants, sulfide-ore processing plants, etc., where pH 4 to 5 precipitation is not uncommon. Acid rain harms aquatic life, leaches nutrients from the soil and kills useful micro-organisms, and corrodes most surface materials it contacts.

Geologic factors that modify the effects of acid rain are: (1) silicious bedrock and soils that cannot neutralize the acid; (2) mountain ranges that concentrate acid precipitation on their windward side and thereby cleanse the atmosphere; and (3) carbonate-rich bedrock and soils that neutralize acids.

Our Hoosier State Beneath Us: Geochemistry/Geophysics

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