Selected heavy metal levels in water and fish from winam gulf in Lake Victoria near Kisumu city, Kenya

Abstract

Lake Victoria is the largest freshwater and fishery lake in Africa. Kisumu City, located at the shore of Winam Gulf has industrial activities discharging effluents into the lake with potential of contaminating the lake water with heavy metals. The contribution of these activities to heavy metal loads of lake water and fish from the gulf is not fully quantified. The assessment of the influence of the surrounding anthropogenic activities and seasons on the metal levels in aquatic samples (water and fish) from Winam Gulf is reported. Water was sampled in triplicates from sites at Molasses Plant, Coca-Cola Plant, Rivers Kisat and Kisian discharge points at intervals of 50 m from the shoreline into the lake in the wet and dry seasons. Fish samples were also collected in triplicates from the lake near Kisumu City. The samples were analyzed for heavy metals (Cd, Cr, Cu, Fe, Mn, Pb and Zn) using a calibrated AAS (6200 Shimadzu Model) following standard methods. There were variations at (p ≤0.05) in the heavy metal levels with sites but not with seasons in both water and fish samples. The range of levels (µg/L) of all analyzed metals in lake water were: 0.20 (Cd) – 334 (Mn). The levels of all analyzed metals in the edible fish tissues (µg/g, dw) ranged from 0.40 (Pb) to 90.85 (Mn). The metal levels in lake water and fish were above WHO limits. The relatively high metal levels in water and fish were attributed to intense anthropogenic activities near the lake. Therefore, consumption of water and fish from Winam Gulf may pose health risks to the residents. There is need for regular environmental assessment of heavy metal levels in water and fish from the lake near Kisumu City.