iments with the characteristic yellow, red or orange colourings (D.E.P. 2, 2002; U.S.G.S.; U.S.E.P.A., 2002). The rate that A.M.D. advances is also influenced by the presence of certain bacteria (Doyle; U.S.G.S). A.M.D that has dissolved heavy metals such as copper, lead and mercury can contaminate ground and surface water. Especially at risk are
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