Acid mine drainage

Acid mine drainage is acidic, metal-rich water formed when sulfide minerals oxidize after exposure to air and water. It can persist long after mining ends.

Pyrite oxidation: The reaction of pyrite with oxygen and water, producing dissolved iron, sulfate, and acidity. It is a major source of acidity in drainage from exposed sulfide-bearing rock.
Heavy metal pollution: Environmental contamination by toxic or ecologically harmful metallic elements at elevated concentrations. Acidic drainage mobilizes metals from rock and mine waste into water.
Passive mine drainage treatment: Treatment systems that use natural chemical and biological processes with little ongoing mechanical input. Constructed wetlands and reactive beds can treat some mine drainage without continuous pumping.
Sulfide mineral: A mineral composed of sulfur combined with one or more metals or metalloids. Sulfide minerals are the source materials whose oxidation can produce mine drainage.
Acid mine drainage prediction: Assessment of whether mine materials will generate acidic drainage and at what rate. Predictions must account for uncertain mineral exposure, water flow, and reaction rates.
Acidithiobacillus ferrooxidans: An acid-tolerant bacterium that gains energy by oxidizing ferrous iron and reduced sulfur compounds. Its iron oxidation can accelerate pyrite weathering and acid production.
Metal bioavailability: The fraction of a metal present in forms organisms can absorb or encounter. Drainage pH and dissolved chemistry determine how readily organisms take up metals.
Constructed wetland: An engineered wetland designed to remove pollutants through sedimentation and biological and chemical processes. Wetlands can retain metals and promote neutralization in suitable drainage settings.
Pyrite: An iron sulfide mineral with the formula FeS₂, common in ore deposits and mine waste. Its abundance and reactivity make it a frequent source of mine-water acidity.
Mine water treatment sludge: Solid residues produced when treatment removes metals and other contaminants from mine water. Safe handling and long-term stability remain necessary after water treatment.

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