Arsenic and polymetallic contaminants in groundwater of the arid regions of South Africa

In South Africa, the majority of rural water supply comes from groundwater hosted within the weathered and fractured crystalline rocks. The main minerals that are responsible for arsenic release into groundwater in South Africa are arsenopyrite (FeAsS), lollingite (FeAs2) and scorodite (FeAsO4 center dot 2H(2)O), where scorodite is an alteration product of arsenopyrite due to prolonged water-rock interaction process. Owing to the release of arsenic from highly mineralized rocks, its concentration in the groundwater reaches up to 253 mu g L-1 (south western part of the country), 6150 mu g L-1 (west of Johannesburg), about 500 mu g L-1 in the Karoo aquifers. Acid mine drainage is also found to be important source of arsenic and other toxic metals in the environment.