Using Electrical Resistivity and Hydrochemistry to Investigate Groundwater Contamination in Oko Olowo, Nigeria

Abstract

This study investigates the extent of groundwater contamination resulting from leachate infiltration at the Oko Olowo dumpsite in Ilorin, Kwara State, Nigeria. The research aims to delineate the subsurface impact of indiscriminate waste disposal using the electrical resistivity method, specifically Vertical Electrical Sounding (VES) with Schlumberger array configuration. Fourteen VES stations were probed—five within the dumpsite and nine in the surrounding areas serving as control points. The analysis revealed predominantly low resistivity values (as low as 10.1 Ωm) within the dumpsite area, especially in the upper layers, indicating high conductivity associated with clayey soils, moisture saturation, and leachate presence. In contrast, control stations outside the dumpsite showed relatively higher resistivity values in deeper layers, though some exhibited signs of mild contamination, suggesting lateral leachate migration. Interpretation through partial curve matching and computer iteration (WINRESIST) indicated that the subsurface is composed of topsoil, weathered basement, partially weathered or clay-rich zones, and fresh basement rocks. The study concludes that the dumpsite has significantly impacted shallow aquifer systems, posing potential environmental and public health risks. The findings underscore the need for improved waste management practices and continuous groundwater monitoring in the area.