Integrated ecological and health risk assessment of heavy metals in surface water, soil and vegetables along Asa River, Ilorin, Nigeria

This study examined the multimedia pollution status, ecological and health risks of heavy metals (Cd, Mn, Fe, Cu, Pb, Zn, Cr) in water, soil and vegetable sampled along Asa River, Ilorin, Nigeria. Ten (10) soil, water, and vegetable samples were taken specifically from areas where the river is commonly used for irrigation. The collected samples were prepared and evaluated for metal contents with Atomic Absorption Spectrometer. The pollution and ecological states of soil, water, and vegetables samples were assessed using already established indices whereas health risks were evaluated by both carcinogenic and non-carcinogenic risk indices. The results revealed that Fe concentration was highest in soil, water and vegetables with range 988.32–3407.60 mg/kg, 1.32–10.31 mg/kg, and 15.12–68.04mg/kg respectively. The computed values of contamination factor and geo-accumulation index showed low contamination from individual metals while the overall pollution index showed that sites 5, 6, and 7 were polluted with the metals. All the metals combined presented low ecological and potential ecological risks in all sites investigated. Results of heavy metal toxicity load showed both Cu and Zn were within the permissible limit whereas Mn exceeded the limit across A4 to A10. All the metals combined showed low toxicity effect on the water quality as estimated by heavy metal pollution index. The vegetables samples had low potential for heavy metal bioaccumulation. Findings revealed that exposure to soil, water, and vegetables in the study area poses low health risk to humans and insignificant cancer risk due to heavy metals.