Accumulation of heavy metals in surface sediments of Lere Lake, Chad

Thirty surface sediment samples collected from Lere Lake were analyzed for As, Co, Cr, Cd, Cu, Ni, Pb, Sb, Sn, Zn, Fe, pH, Electrical Conductivity (EC) and Organic Matter (OM) in order to assess the current pollution status in sediments of the study area. Sediment pollution assessment was carried out using Enrichment Factor (EF) and Geo-accumulation index (I (geo)). The potential ecotoxic effects were evaluated based on sediment quality guidelines. The calculated enrichment factor showed that the sediment was mostly enriched with Sb, Cd, Cu, and Cr. The results of the geo-accumulation index indicated that sediments were unpolluted with Sn, Co, Pb; moderately polluted with As, Cr, Cd, Cu, Ni, Zn, and strongly polluted with Sb. This pollution was attributed to anthropogenic activities caused by the sloping side of Lere Lake including consisting of mainly waste disposal, chemicals used in agriculture, and gold exploitation. Sites that exceeded TEL for Cr and Ni and PEL for Cr are ranked at the highest priority level in terms of potential ecological risk.