Source identification and human health risk assessment of heavy metals in water sources around bitumen field in Ondo State, Nigeria

The concentrations of Cr, Cu, Fe, Mn, Pb, Ni, V and Zn in sediment, surface and groundwater were determined in a total of 180 samples acquired bi-monthly for one year to evaluate the impact of bitumen spills. Principal component analysis (PCA) and cluster analysis (CA) were also used to identify the possible sources of contamination. The concentrations of heavy metals in groundwater, surface water and sediment as follows: Fe > Mn > Zn > Cu > Pb > Ni > V > Cr, Mn > Fe > Zn > Cu > Pb > Ni > V > Cr and Mn > Fe > Zn > Pb > Ni > V > Cu > Cr respectively. The average concentrations of Fe, Pb and Mn in groundwater were found to be above the World Health Organization (WHO) drinking-water quality standard of 0.1, 0.003 and 0.4 mg L-1 respectively. Multivariate analysis suggests significant intrusions of two diagnostic heavy metals (Ni and V) into groundwater samples indicating the migration of these trace metals from bitumen into the water sources. Data from this study showed that the child hazard quotient (HQ) for Pb and Mn were all >= 1, contributing up to 55.5% towards the Hazard Index (HI). Furthermore, Cr, Pb and Ni in groundwater were the predominant contributors towards carcinogenic risks with Ni contributing an average of 81.7% towards the aggregate cancer risk. These results showed significant petroleum contamination that could lead to heavy metal bioaccumulation in residents with a potential threat to public health. Conclusively, these results provide a useful reference for water system management of metals in Agbabu environment.