Acid mine drainage refers to water (leachate, drainage or seepage) that has come into contact with oxidised rocks or overburden that contains sulphide material (coal, zinc, copper, lead). (Keller, 2000; U.S.G.S.; U.S.E.P.A., 2002). A common sulphide is pyrite, or iron disulfide (FeS2), and throughout this essay it will be pyrite that will be the primary sulphide considered. Acid mine drainage is not a new phenomenon, early mining techniques utilized gravity to avoid water pooling, resulting in the water becoming polluted by acid, iron, sulphur and aluminium (U.S.E.P.A., 2002). It is most commonly associated with coal mining, especially with soft coal, coal that has high sulphu

Contamination of the water poses risks to health and integrity of structures, as well as economical loss. In high quantities, heavy metals can affect plant life. Not only is the A.M.D. detrimental to the health of the plant, plants that uptake heavy metals will pass them onto animals within the food chain. Growth and reproduction can be adversely affected in both aquatic animals and in terrestrial animals where drinking water is contaminated. Aquatic species are most at risk, as many are not tolerant of pH fluctuations, with most species having a defined pH tolerance range. Physical structures can be compromised as acid corrodes infrastructures such as bridges (D.E.P. 2, 2002; Keller, 2000; U.S.G.S.; U.S.E.P.A., 2002). Economically, areas affected by A.M.D. can suffer through reduced tourism due to pollution; a decline in recreational sports such as fishing, swimming and other outdoor activities (U.S.E.P.A., 2002).

Other prevention techniques that are also remediation techniques are the construction of artificial wetlands (D.E.P. 2, 2002). Aerobic wetlands are only able to effectively treat water with net alkalinity. Through oxidation reactions metals are precipitated out to form oxides and hydroxides. In anaerobic or compost wetlands the rate of decomposition and mineralization are slowed. The wetland has a reducing nature with the organic environment promotes both microbial and chemical processes that generate alkalinity and increase pH levels. The oxygen is removed from the system by compost, allowing the sulphate to be reduced and also prevents the metals from oxidising.

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