Geophysical Investigation of Groundwater Contamination Risk and Radiological Assessment of Soil around Kurata Dumpsite, Southwestern Nigeria

Abstract

Inadequate solid waste management can lead to groundwater contamination and radiological pollution. This study assessed subsurface conditions, groundwater vulnerability, and radiological health risks at the Kurata dumpsite using integrated geophysical and radiological methods. Fifteen 2D electrical resistivity imaging traverses and Vertical Electrical Sounding (VES) surveys were conducted to characterize the subsurface and evaluate the protective capacity of overburden materials. The results identified subsurface layers consisting of topsoil, peat/leachate, clay, clayey sand, sand, and dry sand. Low-resistivity zones (<15 Ωm) indicated leachate accumulation and possible contaminant migration, especially in areas where the protective clay layer was thin or absent. Longitudinal conductance values ranged from 0.0503 to 0.938 mho, indicating poor to good protective capacities across the site. Radiological analysis showed that the mean activity concentrations of ⁴⁰K, ²³⁸Ra, and ²³²Th were within internationally accepted background levels. Radiological hazard indices, annual effective dose, and excess lifetime cancer risk were all below recommended safety limits, indicating minimal radiological risk. Correlation analysis revealed a weak to moderate relationship between topsoil resistivity and radionuclide concentrations, with K-40 showing the strongest association, while Ra-226 exhibited very little correlation. The low correlation coefficients suggest that radionuclide distribution is influenced by factors such as lithology, weathering, mineral composition, and environmental conditions rather than resistivity alone. Overall, while leachate may threaten groundwater quality, radiological risks remain low, highlighting the need for continuous environmental monitoring and improved waste management practices.