Hydrochemical Characteristics of Open-Pit Groundwater from a Closed Metalliferous Mine in O'kiep, Namaqualand Region, South Africa

— O’kiep, a small town located in the arid to semi-arid Namaqualand region of South Africa is dependent on the Lower Orange River for its water needs, i.e. for domestic and agricultural use. The protection of groundwater resources in this region is important due to water shortages with no peripheral rivers. The town is characterised by an environment with a high proportion of mine tailings and dumps containing sulfidic ores, which can facilitate groundwater contamination. As such, open-pit groundwater (OPGW) samples were collected downstream from a closed metalliferous mine and analysed for physicochemical properties, to evaluate the fitness of OPGW for any potential use. A charge balance error (%CBE) of ±5% was used to interpret the hydrochemical properties of the OPGW, with results indicating that the water is mildly acidic, with a high concentration of SO42-, which suggested sulphide oxidation and weathering of the exposed rocks. Overall, the OPGW was under saturated in terms of metallic species such as Sb, AS, Cd, Cr, Co, Hg, Ni, Se, V and Zn. Furthermore, when the hydrochemical determinants were compared to national drinking water guidelines, it was determined that the OPGW is not suitable for drinking nor irrigation thus requires treatment prior to utilisation.