Correlation studies of heavy metals concentration with sediment properties of some rivers surrounding the Lagos lagoon

Abstract

Lagos lagoon is a highly polluted water body, which receives enormous amount of domestic and industrial wastes from rivers and streams. In this study, two main Lagos urban rivers Odo-Iyaalaro and Shasha rivers that receive industrial effluents and empty into the Lagos Lagoon were examined. The sediments at the bottom of waters play a role in the study of pollution in the rivers. Upstream of Odo-Iyaalaro River (Point 1) receives the largest volume of effluents and showed the highest level of heavy metals in sediments with concentrations of 108.3mg/l for Pb, 805mg/l for Zn, 94.5mg/l for Cu, 31mg/l for Cr and 42.1 mg/l for Cd. Down the river, the levels decreased to 25mg/l for Pb, 64.5 mg/l for Zn, 22mg/l for Cu, 15.9 mg/l for Cr and 1.9 mg/l for Cd. A good correlation was found to exist between the level of Zn in water and sediment, and also between the CEC and %silt-clay of sediments. Shasha River receives relatively fewer amounts of industrial effluents, but is relatively the main receptacle for municipal and land-based waste. The levels of heavy metals in Shasha River were lower compared with that of Odo-Iyaalaro River, with the upstream points showing concentrations of 20.5mg/l for Pb, 25.3mg/l for Zn, 7.9mg/l for Cu, 30.8 mg/l for Cr and 1.5mg/l for Cd. A good correlation exists between the CEC and all the metals determined, and between the %organic carbon and all the metals determined. Compared with literature data, the results of heavy metals gave an indication of pollution.

KEYWORDS: correlation, heavy metals, sediments, caution exchange capacity, rivers, lagoon

Nigerian Journal of Health and Biomedical Sciences Vol. 5(1) 2006: 118-122