DistributionofheavymetalsinsedimentsofMwanzaGulf_of_Lake_Victoria,_Tanzania文献.pdf

Environment International 28 (2003) 619– 625 /locate/envint Distribution of heavy metals in sediments of Mwanza Gulf of Lake Victoria, Tanzania M.A. Kishe a,*, J.F. Machiwab a Tanzania Fisheries Research Institute, P.O. Box 475, Mwanza, Tanzania b Department of Zoology and Marine Biology, University of Dar es Salaam, P.O. Box 35064, Dar es Salaam, Tanzania Abstract Sediment samples were analyzed for Cd, Cr, Cu, Pb, Hg and Zn by AAS. The highest concentrations (ppm) for Cu (26.1 F4.8), Hg (0.2 F 0.05), Pb (30.7 F 5.6) and Zn (45.4 F 13.1) were found at approximately 25 m from the shoreline. Generally, heavy metals concentration in the sediment decreased with increasing distance from the shoreline except for Cd and Cr whose highest concentrations were found at approximately 2000 m from the shoreline. The data also indicated that sediment samples which were collected at the shores within the urban area of Mwanza showed elevated levels of Pb (54.6 F 11.1 ppm) and Zn (83.7 F21.5 ppm). However, the highest concentrations of Cd (7.0 F2.1 ppm), Cr (12. 9 F 1.0 ppm) and Hg (2.8 F 0.8 ppm) were recorded at sampling stations which were adjacent to river mouths. D 2002 Elsevier Science Ltd. All rights reserved. Keywords: Sediment; Heavy metals; Mwanza Gulf; Lake Victoria; Tanzania 1. Introduction revealed that mercury levels were significantly higher than the permissible level of 1 Ag l 1 in drinking water. Kahatano Bottom sediments serves