Evaluation of trace-metal pollution in sediment cores from Lake Edku, Egypt

Abstract

Sediments in nine short cores (<40 cm) from Lake Edku, a brackish coastal basin located east of Alexandria, Egypt, were analyzed to determine distributions of eight metals (Fe, Cd, Cr, Cu, Ni, Pb, As and Zn) and to assess the magnitude of pollution and potential biological effects. Aluminum concentrations were determined as a normalization factor. Sediments also were analyzed for texture, total carbonate, and % organic matter. Trace-metal concentrations generally increased upward in the cores, reflecting increasing influence of human activities over time. Concentrations of trace metals were strongly correlated with Fe, % clay, and % organic matter, all increased eastward across the lake. Contamination factors ranked Cd >> Pb > Cu > Zn > As > Fe > Ni > Cr. Pollution quantification methods indicated that Cd and Pb concentrations present high and moderate ecological risk for living organisms, respectively, and increased use of both elements are associated with changes in human activities over the past several decades. Contamination by Cd likely reflects the increased necessity for use of phosphate fertilizers in the watershed, and contamination by Pb may reflect its increased use in anti-corrosive paints and fuels, for example, in fishing boats. Overall, the study highlights significant anthropogenic contributions in terms of trace-metal pollution.