Ecological Risk Assessment of Heavy Metals in Sediment of Ogbara Stream, Owo, Ondo State, Nigeria

ABSTRACT

Assessment of heavy metal concentration in sediment samples of rural fresh water is very important for the evaluation of potential risks for residents, especially children. Until recently, there has been very little data about fresh water pollution in Owo, Ondo State, Nigeria. The study aimed at evaluating the present health status of Ogbara Stream located in Owo using five pollution indices which comprises of two single pollution indices {Contamination Factor (CF) and Ecological Risk Factor (Er)} and three Integrated pollution indices {Pollution Load Indices (PLI), Potential Ecological Risk Index (RI) and Nemerow Pollution Index (Pnemerow)} to quantify the extent or degree of heavy metal contamination in the sediment. Eight (8) heavy metals (Zn, Fe, Mn, Cr, Cu, Pb, Cd and Ni) from sediment taken for three (3) months from the site were analyzed using Atomic Absorption Spectrophotometer. Heavy metal concentrations range from: Zn (0.817-1.210ppm), Fe (180.127-238.346ppm), Mn (0.529-0.811ppm), Cr (1.651-1.963ppm), Cu (0.348-0.516ppm), Pb (0.177-0.208ppm), Cd (0.025-0.080ppm), Ni (0.046-0.105ppm). All values were below the international standard for sediment and the pollution indices also reveals that the areas are not polluted and also with low potential ecological risk. Result of Pnemerow indicates the areas as safe domain for most living organisms. Continuous monitoring of this area is therefore recommended.