The chemical characteristics of acid mine drainage with particular reference to sources, distribution and remediation: The Witwatersrand Basin, South Africa as a case study

摘要: Abstract Water quality in the immediate vicinity of mine tailings and around Johannesburg, South Africa was investigated. Pollution is derived primarily from Au dumps that are disused or undergoing retreatment to extract remaining Au, dispersed by way groundwater plumes. These discharge into perennial streams area. manifests itself form low pH (>2) high SO 4 2 - concentrations (exceeding 7,000 mg L−1 some cases). improves away loads were found be higher at end rainy season, due a rise water table hence increased seepage. Polluted usually has Eh (300 mV) (2–3), EC (up 8 mS cm−1 instances). Oxidation Fe occurs as emerges on surface, further lowering pH, establishing an Fe(III)-Fe(OH)3 redox equilibrium, which operates for many kilometres downstream. Various processes occur increase compositional heterogeneity water, amongst evaporation, dissolution efflorescent crusts dilution unpolluted water. Wetland environments characterised Eh, appear influenced sulfide–sulfate system, under metals removed, increased. Lakes mining area have normal quality, arises combination metal removal wetlands (most lakes their inlets) rain groundwater. They offer potential method passively treating polluted arising dumps.