Occurrence of Trace Elements in Soils, Plants, Water and Stream Sediments of the Tin-Tantalum Mining Area of Gatumba, Rwanda.

Artisanal (small-scale) mining has become one of the most important sources of toxic elements in the environment. Contamination of soils, plants and water with toxic elements represents a great threat to human health due to its high potential to enter into the food chain. In 2010 and 2011, a systematic study on trace elements in soils, plants, water and stream sediments was conducted in the Gisuma-Kibilira catchment of the Gatumba area of western Rwanda. The geochemical fingerprint of soil, plant, water (springs and surface water in dry and rainy season) and stream sediment samples revealed elevated concentrations of Li, Rb, Cr, and Cs, and low As and U abundances at or below the global average. Trace element contents of soils and most plant materials were below internationally accepted guideline values. All water samples analyzed met the World Health Organization (WHO) drinking water guidelines, and the stream sediments were below critical values of the Holland list. These data provide a baseline for other environmental impact studies for rare-metal mining in Central Africa.