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

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: 118-12

Application of ecological risk indicators for the assessment of Greek surficial sediments contaminated by toxic metals

Τhe present research investigates the partitioning of six selected toxic metals (Ni, Cr, Pb, Zn, Cu, and As) in eight sediment samples; half of them were collected from Elefsis Gulf, and the other half were taken from Koumoundourou Lake, Athens, Greece. Each one of them was treated by applying Tessier’s five-step sequential extraction procedure. Regarding gulf sediments, the results indicated that Cu exhibits a strong affinity to the organic matter with percentages ranging from 65 to 78 %. Considerable amount of Zn (32–40 %) is bound to the Fe-Mn fraction and the non-residual fraction, while Cr and Ni are bound to the organic fraction, an observation that suits all toxic metals examined. Regarding lake sediments, Pb is the predominant metal bound to Fe-Mn (48–51 %). It is also noteworthy that the percentage of Zn bound to carbonated fraction (5–15 %), indicating biological availability. In conclusion, the application of several ecological risk indicators demonstrated that Elefsis Gulf sediments correspond to a moderate pollution level, with Pb and Ni being less bioavailable than in the lake’s samples, in contrast to Zn which is more bioavailable. Finally, Koumoundourou Lakes’ basin is characterized of “low risk.