Pollution and Ecological Risk Assessment of the Bioactive Trace Metals in the Sediment of Cross River Estinary, South South Nigeria

Abstract

The bioactive elements (Fe, Zn, Mn, Mg, Ni, Cd, Cr and Pb) of the surface sediments of five stations (CE 1,2,3,4,5) along the Cross River Estuary Calabar was investigated. Their levels of contamination/pollution and ecological risk on the sediments were assessed using acceptable indices. This was carried out for both dry and wet seasons of the year to ascertain how seasons could affect their distributions. The results obtained revealed that the sum of the average concentrations in all the locations increased in the order Cd < Cr < Mn < Pb < Zn < Ni < Mg < Fe both for dry and wet seasons. The concentrations for all the elements except Mg were within the tolerance limit for sediment. However, distributions were strongly affected by location. The enrichment factor (EF) index revealed that all the elements were sourced through anthropogenic activities, except Mn in Station CE 3 during the dry season that indicated geological origin. The contamination factor (CF) revealed low degree of contamination (C<1) for all the elements at both season which is also confirmed by the negative values obtained in the geoaccumulation index results. While Ecological and Potential Ecological Risk Indices revealed low risk for all the locations.