TAGRA 2025

This study investigates groundwater contamination and aquifer vulnerability in the Ifewara area, Southwestern Nigeria, through an integrated geophysical and hydrochemical approach. Vertical Electrical Sounding (VES) was employed to characterize subsurface stratigraphy, while Atomic Absorption Spectrometry (AAS) analyzed trace metal concentrations in groundwater from five boreholes and five hand-dug wells. Hydrochemical results revealed elevated levels of toxic metals, including manganese (up to 1737 ppm), arsenic, lead, nickel, and copper (up to 94.2 ppm), exceeding WHO permissible limits and posing significant health risks. Health risk assessments using Average Daily Dose (ADD) and Hazard Quotient (HQ) calculations indicated chronic exposure concerns, with manganese exhibiting an ADD of 20.61 mg/kg-day and HQ of 147.22, highlighting neurotoxicity risks. Other metals such as arsenic and lead also showed HQ values far above safe thresholds.
Geophysical data delineated four subsurface layers: topsoil, lateritic hardpan, clayey saprolite, and fractured bedrock aquifers. The clayey saprolite acts as a semi-confining yet permeable layer, facilitating contaminant migration, consistent with hydrochemical contamination patterns. Integration of resistivity profiles with hydrochemical data effectively mapped contamination hotspots and elucidated geohydrological controls on contaminant transport.
The findings demonstrate that both natural geological factors within the Pan-African schist belt and anthropogenic activities, including mining and agriculture, significantly influence groundwater quality and aquifer vulnerability. The study underscores the urgent need for continuous groundwater quality monitoring, targeted remediation, and community education to mitigate health risks. The multidisciplinary methodology provides a robust framework for groundwater contamination assessment in complex tropical basement terrains, supporting sustainable water resource management and public health protection.