Health risk assessments of surface water and groundwater quality for drinking using heavy metal indicators in the Opa drainage basin, Osun state, Southwestern Nigeria
摘要
Natural and human activities within the Opa Drainage Basin impact the water chemistry and can adversely affect human health, hence the need to assess the health risk involved in the consumption of the water. The health risk assessments of surface water and groundwater quality using heavy metal indicators in Opa Drainage Basin, Osun State, Southwestern Nigeria were carried out in this study. Forty (40) water samples, comprising ten (10) surface water samples and ten (10) groundwater samples, were collected for both the wet and dry seasons and were subjected to heavy metal analysis in the laboratory using Atomic Absorption Spectrometry (AAS). The mean concentrations of As, Cd, Co, Cu, Fe, Mn, Pb and Zn were 0.007, 0.026, 0.022, 0.139, 10.974, 0.325, 0.242 and 0.326 mg/L for the surface water and 0.014, 0.011, 0.144, 0.127, 0.489, 0.080, 0.061 and 0.163 mg/L for the groundwater, respectively. The hydrochemical data revealed variations in heavy metal concentrations from 0.00 to 37.95 mg/L, and from 0.00 to 45.65 mg/L for the surface water and groundwater samples, respectively. As and Co showed increased concentration from wet to dry season in the surface water and dry to wet season in the groundwater, while Cd, Fe, Mn, Pb and Zn showed decreased concentration from wet to dry season in the surface water and dry to wet season in the groundwater. The water samples were classified as suitable for consumption (100%) based on the HMPI assessment, hence were all suitable for consumption in their natural state. The mean heavy metal chronic daily intake, hazard quotient, hazard index and incremental lifetime cancer risk of 6.90 × 10− 2, 3.997, 31.33 and 1.80 × 10− 3 in the surface water were higher than their corresponding values of 7.65 × 10− 3, 3.556, 28.74 and 1.46 × 10− 3 in the groundwater. Hence, the consumption of surface water predisposes both populations of adult and children more to health risks compared to groundwater. This study provides significant information on the long-term health risks of consuming the water resources from the Opa Drainage Basin, emphasizing on policy enforcement and need for pre-consumption treatment.