APPLICATION OF ELECTRICAL RESISTIVITY METHOD ON INVESTIGATION OF SUBSURFACE CONTAMINATION USING ELECTRICAL RESISTIVITY TOMOGRAPHY (ERT): A CASE STUDY OF EWHERHE, AGBARHO, DELTA STATE

ABSTRACT This study applies Electrical Resistivity Tomography (ERT) to assess possible subsurface contamination in Ewherhe Community, Agbarho, Delta State. Increasing land-use activities and poor waste-disposal practices in the area have raised concerns about near-surface pollution and its potential impact on soil and groundwater resources. The investigation is based on the geoelectrical principle that electrical resistivity varies with lithology, pore-fluid chemistry, moisture content, and the presence of contaminants, which typically lower resistivity due to increased ionic concentration. Data were collected using an ABEM Terrameter SAS-1000 with a dipole–dipole array along two 100-m traverses positioned across suspected contamination pathways. The acquired data were processed using the DIIPRO v4.01 inversion algorithm to produce two-dimensional resistivity models of the subsurface. These models revealed clear resistivity contrasts and aided the identification of anomalous zones. The inverted sections showed prominent shallow low-resistivity anomalies on both traverses, suggesting moisture-laden or contaminated subsurface layers. These anomalies coincide with areas of active human use, indicating localized pollution likely linked to anthropogenic activities. Higher resistivity zones were interpreted as relatively clean sands and moderately compacted units. The findings imply that contamination may be migrating laterally across shallow subsurface layers, posing potential risks to groundwater quality if unchecked. Overall, the study demonstrates that ERT is a reliable and non-invasive technique for delineating contamination, and the results provide essential baseline information for environmental monitoring, groundwater protection, and sustainable land-use planning within Ewherhe Community., environmental monitoring, and informed land-use planning within Ewherhe Community.