Heavy Metal Pollution Risk Assessment and Source Analysis in Warri River Sediments

Abstract

Contaminated river sediment poses a threat to aquatic life and public health. The focus of this study was to investigate possible contamination of sediments from the Warri River. Triplicate samples were collected from ten sites of intense industrial activities. The sediments were analysed for heavy metals (HMs), anions, and physicochemical properties, including total hydrocarbon content (THC), an indicator of hydrocarbon contamination. The contamination level was evaluated using the following indices: contamination factor index (CF), geo-accumulation index (I_geo), enrichment factor (EF), ecological risk index (ERI), modified degree of contamination (mC_d), pollution load index (PLI), risk index (RI) and sediment quality guidelines (SQG). Principal component analysis (PCA) and hierarchical clustering analysis (HCA) were used to identify the sources of HM contamination. The aggregate contamination indices (mC_d, PLI and RI) indicate no contamination/pollution or ecological risk. Similarly, the single contamination indices (CF, I_geo, and ERI) showed low contamination and ecological risk for almost all heavy metals except for Cd, which was high in many sample locations. Most of the heavy metals exhibited values below both the threshold-effects level (TEL) and the probable-effects level (PEL), except for Cd, where 80% of locations recorded levels between TEL and PEL, suggesting possible ecological risk for Cd. PCA suggests that PC1, loaded with Fe, Zn, Ni, Cd and Cr, indicates anthropogenic activity. PC2, loaded with Mn and Pb, suggests both anthropogenic and geogenic origins. In conclusion, the possible HM contamination necessitates urgent government intervention to protect aquatic ecosystems and public health.