Baseline Information on the Metallic Pollution of Sediments of the Lakes of the Ossa Complex, Dizangue, Cameroon

The aim of this study was to evaluate the state of metallic pollution of the sediments of the three main Lakes (Mevia, Ossa and Mwembe) of the Ossa lake complex by the analysis of some heavy metals from May to July 2011. Copper, Nickel, Lead, Zinc, Cadmium and Iron were measured using atomic absorption spectrophotometry method. According to the standard values of GESAMP (group of Experts on the Scientific Aspects of Marine Pollution), lead concentrations were low in Lake Mwembe (4.985±0.060 mg.kg-1, dry weight), closer to standard values in Lake Mevia (12.935±0.815 mg.kg-1, dry weight) and very high in Lake Ossa (39.935±2.480 mg.kg-1, dry weight). As for Zinc and Cadmium, the contents were superior to standard values in the three lakes.

The level of sediment contamination was evaluated using the Pollution Index (PI) and Enrichment Factor (EF). Only cadmium had a PI value greater than 3 and the highest EF (491.456 in Lake Mevia, 480.310 in Lake Ossa and 1761.099 in Lake Mwembe). All heavy metals presented EF values superior to 50 exception being observed for lead in Lake Mwembe (EF value less than 30). Generally, gross values of the different heavy metals measured, associated with EF values, indicated an anthropogenic pollution of these waters. This pollution could be linked to the use of chemical fertilizers and biocides around the neighborhood of Ossa lake complex by the African Forestry and Agriculture Company of Cameroon (SAFACam).