Distribution, Sources, and Possible Adverse Biological Effects of Trace Metals in Surface Sediments of a Tropical Estuary

Metal (Cu, Zn, Pb, Cd, Ni, Co, and Fe) contamination in sediments from a tropical estuary (Ebrie Lagoon, Ivory Coast) was assessed using pollution indices, multivariate analyses and sediment quality guidelines (SQGs). The results demonstrate that increased input of the studied metals occurred over the past 6years compared to that from 20years ago, due to rapid population growth, along with the increase of industrial and agricultural activities in the vicinity of the estuary. Ebrie Lagoon was also found to be one of the most contaminated tropical coastal estuaries. Very high average total organic carbon (TOC) content was found (1.9-3.70%) with significant spatial variation as a result of the influence of anthropogenic activities. This study also found that TOC plays an important role in the distribution of Cu, Zn, Co, and Cd in the Ebrie Lagoon sediments. Moderate to high sediment contamination was observed for Cd and Cu, moderate contamination was observed for Zn and Pb, while low contamination was observed for Ni, Co, and Fe. Cluster analysis (CA) and principal component analysis (PCA) investigation revealed that Cu, Zn, Cd, and Co result mainly from anthropogenic sources while Pb, Ni, and Fe may be of natural origin. The pollution-loading index (PLI) indicated that all of the sites close to wastewater discharges were highly polluted. The sediments are likely to be an occasional threat to aquatic organisms due to Cu, Zn, Pb, Cd, and Ni contents, based on the SQGs approach.