Assessment of Heavy Metal Contamination in Sediments of the Bonny River, Rivers State

Heavy metal pollution in marine sediments poses significant ecological risks to aquatic organisms and human health through bioaccumulation. This study assessed the concentration of heavy metals including lead, cadmium, zinc, copper, and mercury in surface sediments collected from five stations along the Bonny River in Rivers State, South South Nigeria. Samples were collected during wet and dry seasons over a period of six months using a Van Veen grab sampler. Standard atomic absorption spectrophotometry was used for metal analysis following acid digestion procedures. Results were compared against international sediment quality guidelines to determine contamination status. Physicochemical parameters such as pH, temperature, total organic carbon, and grain size were also measured to assess their influence on metal distribution. Findings revealed elevated concentrations of lead and cadmium at stations proximate to industrial discharge points, particularly near the Eleme Petrochemical Complex. The geo-accumulation index and pollution load index were applied to quantify contamination severity. Seasonal variation significantly influenced metal concentrations, with higher levels recorded during the dry season. The study concludes that anthropogenic activities are the dominant source of heavy metal enrichment in the Bonny River sediments. Recommendations include stricter enforcement of industrial effluent standards and regular sediment monitoring programs to safeguard the estuarine ecosystem. Keywords: heavy metals, sediment contamination, Bonny River, atomic absorption spectrophotometry, bioaccumulation.