Assessment of heavy metals in sediments and associated ecological risks in Ikwu river, Umuahia, Nigeria

Abstract

Sediments can act as pollutant sink as well as source of secondary contamination in aquatic ecosystems. The pollution characteristics of eight heavy metals in the sediments of Ikwu River, Umuahia were investigated using eight assessment indices. The study was carried out between January and June 2022 in three stations. Results showed that cadmium exceeded permissible limit, copper exceeded limit only in February 2022 while others were within limits. The values in Stations 2 and 3 were slightly higher, attributed to localized anthropogenic influence; though other human activities in the watershed especially agriculture were not ruled out in the area. Different levels of heavy metal pollution were observed in the sediments as indicated by the indices but Cd was the principal pollutant. The indices indicated the following - Contamination Factor: Zn and Cu (moderate) and Cd (very high), Degree of Contamination (very high), Ecological Risk: Cd (high) and Cu (considerable), Potential Ecological Risk (high), Pollution Load Index (>1), Enrichment Factor: Zn and Cu (moderate) and Cd (extremely high), Geo-accumulation Index: Cd (very highly polluted) and Quantification of Contamination: Cd and Cu (anthropogenic). The sediments were polluted with toxic metals that may be detrimental to humans and aquatic biota.