The impact of acid mine drainage in South Africa
2011; Academy of Science of South Africa; Volume: 107; Issue: 5/6 Linguagem: Inglês
10.4102/sajs.v107i5/6.712
ISSN1996-7489
Autores Tópico(s)Mining and Resource Management
Resumoof late and the number of short courses and workshops devoted to the topic has mushroomed.The current interest was prompted mainly by concern arising from the decanting of contaminated water from the old gold mines in the Krugersdorp area into the Cradle of Humankind.This led to the establishment of an interministerial committee on AMD in late 2010.As part of this initiative, a technical task group was formed to investigate the problem and to recommend possible solutions.The report was finalised in December 2010, 1 and focused primarily on the immediate problems arising from gold mining and in particular on the now defunct mines in the Western Basin (Krugersdorp area), the Central Basin (Roodepoort to Boksburg) and the Eastern Basin (Brakpan, Springs and Nigel area).However, the problem of AMD is of far wider extent and to understand it in its entirety it is necessary to take a much broader geographic view. The origin of acid mine drainageAcid mine drainage (also sometimes referred to as acid rock drainage) is a well-understood process 2 and arises primarily when the mineral pyrite ('fool's gold' or iron disulphide) comes into contact with oxygenated water.The pyrite undergoes oxidation in a two-stage process, the first producing sulphuric acid and ferrous sulphate and the second orange-red ferric hydroxide and more sulphuric acid.Pyrite is a common minor constituent in many mineral deposits and is associated with our coal (it is the main host of sulphur in coal, the source of acid rain) and the gold deposits of the Witwatersrand Basin.During normal weathering of these mineral deposits, acid is produced but at a very slow rate, so slow that natural neutralisation processes readily remove the acidity.
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