Pollution of Surface Water Close to an Artisanal Gold Mining Area: the Case of Macalder Mine, Kenya

This study investigated the contribution of artisanal gold mining and processing activities at the Macalder Mine, Kenya to iron (Fe), copper (Cu), lead (Pb), zinc (Zn), and nickel (Ni) levels in the drinking water of the nearby Macalder Stream and River Kuja. A tailings dump of an abandoned gold mine in the area is the source of the residual ore that is being reprocessed by the artisanal miners. The artisanal mining operations are 60 m and 1200 m upstream of the Macalder Stream and River Kuja, respectively. Pb and Ni levels in gold tailings were within previous reported metal concentrations in gold tailings while, Fe, Cu and Zn exceeded the reported concentrations. The mean Fe, Cu, Pb, Zn and Ni concentrations in Macalder Stream as well as mean Fe, Pb, and Ni concentrations surpassed the World Health Organisation (WHO) recommended standard limits values for drinking water, though mean Cu and Zn concentrations in River Kuja were within permissible WHO standards for drinking water. The similarity between the compositions and concentrations of Fe, Cu, Zn, Pb, and Ni in the reprocessed tailings and water from the stream suggests that the artisanal mining activities are a contamination source. The abrupt improvement in water quality in the River Kuja is likely due to dilution by the relatively unpolluted River Kuja water.