Determination of manganese, iron, copper, zinc, cadmium and lead in fish species, and sediments from Mombasa town and the Winam Gulf of Lake Victoria
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Manganese, iron, copper, zinc, cadmium and lead were determined on 218 fish and 20 sediment samples collected from selected sites in Winam Gulf of Lake Victoria and Mombasa Old Town on the Indian Ocean (Kenya) were analysed using atomic absorption spectrophotometry. The concentrations of all the six elements obtained in fish muscle tissues from Lake Victoria and Indian Ocean were found to be relatively low and below maximum recommended values (International Standards) and thus posed no potential danger to the consumers. Generally the metal content of the marine fish were found to be higher than freshwater fish. The concentrations of these elements were several orders of magnitude higher in fish scales than in muscle tissues. Oreochromis niloticus and Labeo victorianus exhibited species specificity in the accumulation of manganese in the scales, while Caranx armatus exhibited a similar feature of zinc. The concentrations of the elements in L. niloticus and O. niloticus were uniform irrespective of locality. For sediment samples from Winam Gulf, certain localities known to be polluted like the boat jetty and River Kassat exhibited elevated concentrations of some of the metals indicating localised pollution. The study revealed Winam Gulf to be clean with low heavy metal content in fish with average values of concentration similar for L. niloticus and O. niloticus.