Concentrations, Ecological and Health Risk Assessment of Heavy Metals in Surface Water and Sediments of Ogun River in Owode Onirin,

Industrial processes, including scrap yards, can contaminate surface waters with heavy metals, posing a risk to aquatic habitat and human health. Thus, the concentrations, ecological and health risks of heavy metals in surface water and sediment of the Ogun River in Lagos was investigated. Surface water and sediments collected from the Ogun River were analyzed for some physicochemical parameters and heavy metals using standard procedures. The results indicated that physicochemical parameters such as temperature and COD were within the standard limits while pH, TDS, EC and TSS for site 1 exceeded the USEPA standard. The distribution of heavy metals at the sampling points was Pb>Cr>As>Cd and Pb>Cr>Cd>As for water and sediments, respectively. The ranges of heavy metals in water were 0.461-0.954, 0.001-0.023, 0.457-1.426 and 0.002-0.645 mg/L and in sediments were 1.034-3.661, 0.882-1.780, 1.005-3.802 and 0.009-0.404 mg/kg for Pb, Cd, Cr and As, respectively. Pb and Cr at all sampling sites exceeded safety limits for drinking water, with the highest concentration found at sites 1 and 4, respectively. The contamination factor (CF) of all the studied heavy metals had a low degree (CF < 1) while geo-accumulation index (Igeo) showed that there was no contamination in the sediment. The values of the pollution load index (PLI) were less than one (<1), indicating moderate contamination of the sediment quality. The results of the HQ and HI values of the heavy metals for dermal and ingestion pathways were below the safety level (HQ and HI < 1) for adults and children. However, the carcinogenic risk of Pb, Cr and As in the sediment exceeds the acceptable limit (1 × 10−6), suggesting a potential risk to human health in this regard.