Partitioning of heavy metals in the sediments of Lake Naivasha, Kenya

Abstract

Metal fractionation is a powerful tool for studying the mobility, bioavailability and toxicity of metals in sediments and soils. A seven-step sequential extraction technique was used to determine the potential mobility of selected heavy metals (Fe, Mn, Zn, Cu, Pb, Cd and Ni) in the sediments of Lake Naivasha. Results indicate that residual fraction was the most important phase for the elements Fe, Mn, Cu and Zn. However, Pb and Cd are highly enriched in the non-residual phases. Nickel on the other hand was distributed evenly between the non-residual and the residual fractions.The total concentrations of the heavy metals suggested a decreasing order of iron ≫> manganese ≫ zinc > nickel > copper ≫ lead > cadmium. However, the detailed sequential extraction data indicated an order of release or mobility of cadmium > lead ≫ nickel ≫ zinc > manganese > copper > iron. The high percentage of Cd and Pb in the mobile fractions suggests high bioavailability of these two elements in the study area and maybe a pointer to anthropogenic input of the two elements in the study area.