School of Environmental Studies, Moi University, P.O. Box 3900, Eldoret, KENYA

Concentrations of heavy metals in water, fish, and sediments of the Winam Gulf, Lake Victoria, Kenya

Water, sediments, and fish samples were collected once a month from 8 sites in the Winam Gulf of Lake Victoria, over the period of September 1997 to February 1988. The samples were analysed for contents of lead, cadmium, selenium, and arsenic, and comparisons made between sites to infer contamination from anthropogenic activities.

Mean concentrations of lead in Lake Victoria waters ranged from 0.12 ppm at site 8, to 0.45 ppm at site 2. Cadmium concentrations in water were 0.01 ppm at all sites, except site 13, which had 0.02 ppm. Arsenic concentrations in water ranged from 0.16 ppm at site 12, to 1.82 ppm at site 2. Selenium concentrations in waters ranged from 0.45 ppm at site 1, to 1.38 ppm at site 12.

Lead concentrations in sediments in the Gulf ranged between 21.2 and 76.2 ppm, while sediment cadmium concentrations ranged between 0.4 and 2.8 ppm. Arsenic concentrations in sediments ranged between 37.6 and 394.0 ppm, while selenium concentrations ranged between 36.8 ppm and 742 ppm.

Lead concentrations in fish from the Gulf showed concentrations ranging from 12.7 to 36.5 ppm dry weight, while cadmium concentrations in the fish were in the range 0.69 to 1.94 ppm. Arsenic concentrations in fish ranged from 24.4 ppm to 50.3 ppm, while selenium concentrations in fish were in the range 24.4 ppm to 50.3 ppm.

Lake Victoria waters within the Winam Gulf have trace metal concentrations that are above the recommended values for drinking water. Lead clearly has an anthropogenic source in Kisumu.
The trace metal concentrations obtained in this study for fish are within recommended levels for daily intake, even assuming a person feeds on 1 kg of fish every day. The levels are, however, above those obtained by other workers 10 years ago, showing that there is a steady increase in the levels of trace element contamination in the Winam Gulf of Lake Victoria. There is therefore need for continued monitoring of trace metal contamination in the Winam Gulf, and for strong recommendations to policy makers for the banning of leaded fuel in Kenya.