Groundwater pollution and risk assessment using indexed-based models: a case study of Igbo-Etiti area, eastern Nigeria

Water is one of the most abundant resources on earth not evenly distributed. Due to the high shortage of water sources in Igbo-Etiti and intensive agricultural practices in the area, assessment of groundwater pollution and its potential risk to contamination is imperative, as its remediation when contaminated is extremely challenging. Vertical electrical sounding (VES) and physicochemical analysis were carried out in twenty (20) locations and five groundwater samples, respectively, with the aim to evaluate the groundwater pollution indices and the ecological and human health risk associated with its pollution. The VES results delineated five geologic layers and ten characteristic curve types. The fourth layer with the aid of the VES results constrained by the borehole lithologic information on the water bearing geologic unit was delineated as the major exploitable aquifer layer. Results of groundwater vulnerability to pollution classified the area into low (15%), moderate (60%), and high (20%) vulnerability. Physicochemical analysis results on the studied groundwater revealed acidic (pH 4.6) to alkaline (pH 7.2) groundwater conditions. Pollution index of groundwater results delineated a moderate to very high pollution index, with cadmium and arsenic consistently identified as the heavy metals contaminating the groundwater. Ecological risk assessment revealed a moderate to very high integrated potential ecological risk, while human health risk results delineated a target hazard index greater than one in all the studied groundwater samples. This study will serve as a guide to the residents and society in sustainable development decision-making that will preserve the quality of the study area groundwater.