The concentration of manganese, iron, copper, zinc, cadmium and lead in sediments and fish from the Winam gulf of lake Victoria and fish bought in Mombasa town markets

Abstract

Manganese, iron, copper, zinc, cadmium and lead concentrations were determined on a total of 218 fish and 20 sediments using atomic absorption spectrophotometry. Representative fish species were collected from different localities within the Winam gulf of Lake Victoria and Mombasa Town (Indian Ocean), viz. Latest ni1oticus, Oreochromis niloticus, Labeo victorianus, Haplochromis sp., Synodontis victoriae and shilbe mystus (from lake victoria) and Caranx armatus, Va1amugil sehe1i, Pel10na ditchela, Lethrinus miniatus, Mega1aspis cordyla, Ab1ennes hians, sphyraena forsteri, Archamia macroptera, Gazza minuta and Pempheris oualensis (from Mombasa). The destruction of organic matter (fish muscle) was achieved but the wet-oxidation method with nitric and sulphuric acids., The method incorporates use of an anti-foam, and sample sizes up to 109 can be processed in an aluminium block, with improved detection limits. Factors affecting the determinatio~n of the trace metals .... .. have been studied and the resu lt s"are repo rt ed ; : Two < methods fOT the analysis of the sediment samples were compared: using nitric acid and nitric-su1phuric acids in combination. The analytical procedures were optimized and verified with regard to precision and accuracy (reproducibility) and by use of IAEA certified reference materials viz: Lake Sediment, fish solubles, milk powder and freeze- dried animal blood, and the results obtained are in agreement with certified values. Quantitation was performed by a standard addition technique. Evaluation of the method was further done by analysis of cigarettes. The detection limits were determined both experimentally, as well as deduced from the results obtained for each element, thus completing qualification of the procedure. Mean recoveries obtained for spiked samples were: 98-108% for manganese, 97-102% for iron, 95-106% for copper, 94-103% for zinc, 96-102% for cadmium and 92-107% for lea,p.