Spatial Distribution and Speciation of Heavy Metals in Sediment of River Ilaje, Nigeria

Speciation of heavy metals (Zn, Fe, Cr, Cd, Cu and Pb) was carried out on the top and bottom sediment samples of two sampling sites in river Ilaje, Nigeria during the dry and rainy seasons. The samples were subjected to sequential extraction method and the extracts were analyzed for heavy metals using atomic absorption spectrophotometer. The result shows that Zn and Fe are abundant in reducible fraction, oxidizable fraction and highest in residual fractions in both seasons. The concentrations of Cr and Cd varied greatly with the seasons, while the highest concentration of Pb occurs in residual fraction for both seasons. The concentration of Cu occurs abundantly in oxidizable fraction and residual fraction, Cu and Pb shows a low concentration in exchangeable fraction and carbonate fraction. This study reveals that the mobility and bioavailability of the heavy metals in the sediment for the two seasons are in this order: Fe > Cr > Zn > Pb > Cu > Cd. It was observed that the origin of metals in the environment is likely to be lithogenic.