Geological and anthropogenic impacts on inorganic water quality at rural clinics in the Limpopo Province, South Africa
Van Heerden, Karien
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This study gives insight to the origin of pollution in the water resources of the Limpopo province of South Africa. The Limpopo province is the largest rural province in South Africa. Up to 40% of the total population does not have access to sufficient water supply, resulting in adverse health effects. The purpose of this study is to determine (1) the degree of inorganic pollution of borehole water; (2) to identify the pollution sources, and (3) to determine whether the pollution is inherited from the surface water that recharges the groundwater or is caused on site near the bore holes. In order to achieve these objectives, surface water quality data (14 675 samples) and borehole water data (340 samples) at health facilities were analysed. A pollution index, defined by the following ratio: Pollution index (%) = 100 x ([Cl–] + 2[SO4^-2] + [NO3-] + 3[PO4^-3]) ÷ ([Cl-] + 2SO4^-2 + [NO3-] + [PO4^-3] + [HCO3-]) was used to determine the percentage of contribution of each chemical species towards pollution. This ratio is based on the fact that bicarbonate is released during chemical weathering of rocks whereas sulphate, nitrate, chloride, and phosphate are anthropogenic in origin. The pollution index shows that 6% of the surface waters and 21% of the borehole water is severely polluted. The pollution of the surface water is characterized by high concentrations of sulphate whereas the pollution of the borehole water is characterized by high concentrations of chloride. This indicates that the pollution of the borehole water is not so much the result of the infiltration of polluted surface water, but rather the result of on–site pollution on the surface near the bore holes.