A study of the trends in the physico-chemical properties of the surface water and the heavy metals composition of the bottom sediments of Ijana river, Warri, Delta State, Nigeria

A study was carried out to investigate the concentrations, distribution and speciation of some heavy metals such as Cd, Cu, Pb, and Cr in the bottom sediments of Ijana River which has been contaminated by effluent from petroleum exploitation activities. The total concentration levels of Cd, Pb, Cu, and Cr were determined specifically at upstream, effluent zone, downstream and recipient of storm water of the river. Pb, Cu, and Cr were found to be the most abundant metals in the river. The distribution pattern of the river indicates the source of pollution to be land-based. Sequential extraction showed that 30 -60% of Cd, were exchangeable fraction, indicating that Cd in the sediments posed a high risk to local environments while Cu, Pb and Cr were at moderate risk levels. From the relationship between percentage fraction of metal speciation and total metal concentration, it was found that the distribution of Cd, Cu, and Pb in some fractions were dynamic in the process of pollutants migration and the stability of metals in sediment of the Ijana River decreased in the order Cr > Pb > Cd > Cu. The correlation analysis suggest that some of the metals are strongly associated, indicating a common source or chemical similarity. The pollution load index (PLI) of the studied area ranged from 0.10 to 50.78 which indicated the sediments were polluted while the index of geoaccumulation showed that all the sampling points may face a severe metal pollution/contamination problem in the future.