Using Pollution Load Index and Geoaccumulation Index for the Assessment of Heavy Metal Pollution and Sediment Quality of the Benin River, Nigeria

A study on the characterization of sediment quality was conducted along a stretch of the Benin River, Niger Delta, Nigeria, between June and December, 2011 to evaluate the impact of anthropogenic activities. Five stations were selected from Ajimele to Koko for the investigation. Samples were analysed using standard methods. The results showed that the sediment was slightly acidic across the study stations. There was no significant difference (P> 0.05) in the mean concentrations of organic carbon, total nitrogen, exchangeable anions and zinc, while electrical conductivity, chloride, nitrate, phosphate, sulphate, sodium, potassium, calcium, magnesium, exchangeable base, iron, chromium, manganese, lead and nickel showed significant difference (P<0.05). A posteriori Duncan Multiple Range (DMR) test revealed that with the exception of Nickel, the concentrations of these parameters at stations 4 and 5 were not significantly different from each other, but were significantly higher (P<0.05) than those of stations 1, 2 and 3. Estimated Pollution Load Index (PLI) and geo-accumulation index (Igeo) revealed that the sediments at all stations were practically uncontaminated by heavy metals. The significant spatial variation recorded in the concentrations of some parameters used in characterizing the sediment quality is a reflection of impacts of anthropogenic activity on quality of this river.