Concentrations, hydrochemistry and risk evaluation of selected heavy metals along the Jimi River and its tributaries at Obuasi a mining enclave in Ghana

Abstract

Surface water represents significant source of fresh water for irrigation and drinking purposes and therefore preserving the availability and quality of this resource is extremely important. Surface water samples within the catchment area of the Obuasi mine were analysed to assess dissolved concentrations, hydrochemistry, risk evaluation of selected metals and their effects on drinking water quality. Water samples were collected from the Jimi River and its tributaries and analysed for physico-chemical parameters and heavy metals using standard analytical methods. Health risk assessment of As, Pb, Fe, Cd, Ni and Zn based on the average daily dose, hazard quotient and cancer risk was also determined. The results indicated that, most of the physico-chemical parameters are within WHO guidelines except conductivity, turbidity, alkalinity and total hardness. The mean concentrations of heavy metals and ionic dominance pattern follow the order: Cd < As < Pb < Zn < Ni < Fe, Ca2+ > Mg2+ > K+ > Na+ and HCO3 − > SO4 2+ > Cl−. The health-risk assessment revealed that hazard quotient (HQing) and hazard index (HIing) values were below the acceptable limit, indicating non-carcinogenic risk to the recipient via oral intake and dermal contact of the water. The calculated values for chronical daily intake (CDI) were found in the order of Fe > Zn > As > Pb > Cd > Ni in both adults and children. The carcinogenic risk (CRing) via ingestion route for As, Cd, and Pb were higher than the acceptable limit (10−6). Multivariate statistical analysis results revealed that natural processes and anthropogenic activities were the main sources of water contamination. The results suggested multiple natural processes and anthropogenic activities like mining significantly contribute to the considerable environmental pollution contamination of the Jimi River and its tributaries. Our findings have important public health implications, and we suggest that a system of sentinel surveillance is being implemented that, in turn, can guide adequate responses.