Kortatsi B.K., Tay C.K., Anornu G., Hayford E., Dartey G.A.
CSIR-Water Research Institute, P. O. Box M32, Accra, Ghana; Civil Engineering Department, KNUST, Kumasi, Ghana; Geology Department, University of Ghana, Legon, Accra, Ghana
Kortatsi, B.K., CSIR-Water Research Institute, P. O. Box M32, Accra, Ghana; Tay, C.K., CSIR-Water Research Institute, P. O. Box M32, Accra, Ghana; Anornu, G., Civil Engineering Department, KNUST, Kumasi, Ghana; Hayford, E., Geology Department, University of Ghana, Legon, Accra, Ghana; Dartey, G.A., CSIR-Water Research Institute, P. O. Box M32, Accra, Ghana
Alumino-silicate mineral dissolution, cation exchange, reductive dissolution of hematite and goethite, oxidation of pyrite and arsenopyrite are processes that influence groundwater quality in the Offin Basin. The main aim of this study was to characterise groundwater and delineate relevant water-rock interactions that control the evolution of water quality in Offin Basin, a major gold mining area in Ghana. Boreholes, dug wells, springs and mine drainage samples were analysed for major ions, minor and trace elements. Major ion study results show that the groundwater is, principally, Ca-Mg-HCO 3 or Na-Mg-Ca-HCO 3 in character, mildly acidic and low in conductivity. Groundwater acidification is principally due to natural biogeochemical processes. Though acidic, the groundwater has positive acid neutralising potential provided by the dissolution of alumino-silicates and mafic rocks. Trace elements' loading (except arsenic and iron) of groundwater is generally low. Reductive dissolution of iron minerals in the presence of organic matter is responsible for high-iron concentration in areas underlain by granitoids. Elsewhere pyrite and arsenopyrite oxidation is the plausible process for iron and arsenic mobilisation. Approximately 19 and 46% of the boreholes have arsenic and iron concentrations exceeding the WHO's (Guidelines for drinking water quality. Final task group meeting. WHO Press, World Health Organization, Geneva, 2004) maximum acceptable limits of 10 μg l -1 and 0.3 mg l -1, for drinking water. © 2007 Springer-Verlag.
Biogeochemistry; Catchments; Hydraulic conductivity; Oxidation; Silicate minerals; Arsenopyrite; Cation exchange; Ghana; Groundwater acidification; Hydrogeochemical evaluation; Offin basin; Groundwater; acidification; aluminosilicate; concentration (composition); dissolution; gold mine; groundwater; hydrogeochemistry; ion exchange; iron; oxidation; water quality; Africa; Ghana; Offin Basin; Sub-Saharan Africa; West Africa