Geophysical investigation of groundwater contamination in urban areas: a case study of active dumpsites in oyo town, Nigeria

Abstract

nvironmental safety is a pressing global concern, particularly in Africa, where poor sanitation and contaminated water sources contribute to rising health issues. Active dumpsites are recognized as a source of groundwater pollution, yet their specific impact on water quality remains insufficiently documented. Therefore, this study aimed to evaluate potential groundwater contamination resulting from active dumpsites in the Ilaka area of Oyo town, Nigeria. Electrical Resistivity Tomography was established on two traverses at the study area with a total length of 150 m and 5 m electrode spacing. Eight Vertical Electrical Sounding points were sounded at the established profiles. The geoelectric sections revealed three distinct layers: the topsoil, the weathered layer, and the fresh basement. In Traverse One, the recorded layer resistivity ranges from 29 to 938 Ωm, while in Traverse Two, it ranges from 30 to 1243 Ωm. The corresponding layer thickness varies from 0.8 to 21 m in Traverse One and from 2.5 to 24 m in Traverse Two, indicating a shallow overburden thickness. The 2D image of ERT revealed extremely low resistivity values in all the traverses across the dumpsites which suggests the presence of clay formation underlying the topsoil which may have been trapped in the contaminant plumes. Groundwater from the study area was found to be free from contaminants.