Ecological risk assessment of Cd, Cr, Ni and Pb metals in Sambreiro river estuary sediment in the Niger Delta Region of Nigeria

The characteristic ecological risk of Cd, Cr, Ni and Pb metals in sediment sampled from an estuary (Sambreiro River) in the Niger Delta Region of Nigeria was assessed with the application of some pollution indices and multivariate analysis under quality-controlled conditions. Concentration of Cd and Cr in the stations was in the trend: Cd - St2 > St4 >St1 > St5 > St9 > St8 > St6 > St3 > St10, Cr - St2 > St7 > St5 > St9 > St4 > St8 > St3 > St10 > St1. The relationship between Effects range low- Effects range median (ERL-ERM) and environmental concentration of the metals [M] showed adverse effect occurring occasionally on the sediment biological (i.e. ERL <= [M] < ERM) is in the order: St2 > St4 > St1 > St5 > St9 > St8 > St6 > St7 for Cd, only St2 for Cr, and St3 for Pb; while other stations revealed minimal effect (i.e. [M] < ERL) for Cd, Cr, Ni and Pb. The values of mean Effects range median Quotient (m-ERM-Q) indicate that St1, St2, St4, St5, St6 and St9 had 21% probability of toxicity; while St3, St7, St8 and St10 had 9% probability of being toxic. The percentage potential ecological risk factor (%) for the metals across the stations correspond to Cd (70.55) > Pb (22.74) > Ni (4.27) > Cr (2.43); indicating the contribution of Cd as highest to the degree of an ecological risk index for the studied river. Multivariate analysis determined that the possible source of metals in this study location was from the boats manufacturing and fabrication activities taking place in the some of the stations.