ASSESSMENT OF HEAVY METAL CONTAMINATION IN NTSINI RIVER SEDIMENTS FROM THE COASTAL PROTECTED AREA OF LIBREVILLE, NORTHWEST GABON

To assess the trace element contamination status of sediments from the Ntsini River and the ecological risk to aquatic biocenosis, we analyzed physicochemical properties of six trace metal contents (Cd, Cu, Cr, Ni, Pb, and Zn) in twelve (12) sediment samples from four sampling sites (Ngwamba, Moka, Pages and Nende) using Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES). The results show that the sediments generally contain significant amounts of organic matter, have an acidic pH and exhibit similar concentrations of Cd, Cr, Cu, Ni, Pb and Zn, except for sediments from the Nende site, which are characterized by neutral pH and higher Cd concentrations. The contamination factors (CF) for Cd (CF > 2), Pb and Zn (1 CF < 2) and Cr, Ni, and Cu (CF < 1) indicate sediment contamination at the following sites :Moka for Cr and Pb, Pages for Zn and Nende for Cd. Only Cd potentially presents a moderate to considerable ecological risk for the studied sediments. The ecological risk index (RI) values in the most Cd-contaminated sediments from the Ngwambaand Nende sites (95 RI < 190) indicate a moderate contamination risk to biocenosis in the Ntsini River.