Contribution of Catchment and Anthropogenic Activities to Metal Bioavailability in the Lake Victoria Sediments using Sequential Extraction and Radiotracer Analysis

Sequential extraction and radiotracer analyses were used to evaluate the geochemical partitioning of metals (Pb, Cd, Cr, and Cu) in the sediments of Lake Victoria to partition the contribution of catchment areas. Highest total concentration and enrichments of Pb, Cd and Cr occurred near river inlets from polluted urban areas discharging municipal effluents into the rivers. Partitioning coefficient (Kd) of all metals were lowest in lake sediments at the sites receiving water with high concentration of metals, which showed an apparent decrease with increasing metal enrichment. The exchangeable phase and Fe/Mn oxides were the most important binding phases for Pb, Cd and Cr at the sites receiving industrial and municipal wastes, indicating that these sediments were subjected to recent anthropogenic metal pollutants. Cu partitioned in the residual phase at the site with high geological Cu suggesting Cu enrichment from the natural sources. At the reference sites, metals were bound to the secondary (residual) phase suggesting natural sources. This study demonstrates that the partitioning of metals in the sediments at the shore of the recipient waterbodies are characteristic signatures for anthropogenic activities in the catchment areas.