(Abbreviated as AMD) Form of mine pollution that affects river systems. AMD occurs when sulfide-bearing minerals, usually mine tailings, are exposed to air and water. This creates sulfuric acid, which causes heavy metals to dissolve and leech into nearby stream/river systems.

AMD has dramatic effects on water quality, often killing fish and destroying aquatic habitats. Such potential for environmental destruction is largely due to the fact that it is extremely acidic, and can contain up to 300 times the acid concentrations of acid rain. Acid Mine Drainage is virtually impossible to treat with current anti-contamination technologies, and can continue for centuries after the appearance of toxic waste.