Acid Mine Drainage

Acid drainage from abandoned mines is a widespread problem, but even more acute in the desert where freshwater sources are scarce.

When water comes into contact with pyrite in coal and the rock surrounding it (overburden), chemical reactions take place which cause the water to gain acidity and to pick up in solution iron, manganese and aluminum. Water that comes into contact with coal has a characteristic orange-red, yellow (sometimes white) color. The metals stay in solution beneath the earth due to the lack of oxygen. When water emerges from the mine or borehole it reacts with the oxygen in the air or dissolved in the stream and deposits iron, manganese and aluminum on rocks and the stream bed. Each of the chemical characteristics of acid mine drainage (AMD) is toxic to fish and aquatic insects in moderate concentrations. At high concentrations all plant life is killed.

Photo by G. Donald Bain The Geo-Images Project
Keystone Canyon, New York Mountains, East Mojave National Scenic Area, CA

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