Acid Mine Drainage

Abandoned mines and mine spoiled represented a major source of environmental contamination through acidic drainage. Cole is often associated with pyrite. when mining exposed the cole to air, a combination of autooxidation and microbial Fe and S oxidation produce acid. the subsequently acidic damage is environmentally harmful to life and physical structure. stream pH may decrease from near-natural to 2 to 4.5. Sulfate concentration is stream may range from 1000 to 20000 mg/l. ferrous ion may become non-degradable in the water but that stream becomes blood-red with precipitated Fe+.

Acid mine drainage is a result of chemical and microbial reactions. At natural pH, pyrite (FeSo2) oxidation is rapid and spontaneous, but below pH 4.5 autooxidation slows. in the range of pH 3.5 to 4.5, the ion bacterium Metallogenium catalyzes pyrite oxidation, while at pH < 3.5, Thiobacillus species and Leptospirillus species become important. At this stage microbially catalyze oxidation is several hundred times higher than spontaneous oxidation. 


The Fe(OH)3 forms a red precipitate that is a classic indicator of acid mine drainage in the stream.

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