انجمن ملی ژئوفیزیک ایران مجله ژئوفیزیک ایران 2008-0336 20 3 2026 07 23 Geoelectric investigation and physicochemical analysis of parts of Niger Delta, Nigeria, for groundwater quality assessment Geoelectric investigation and physicochemical analysis of parts of Niger Delta, Nigeria, for groundwater quality assessment 167 186 226465 10.30499/ijg.2025.530972.1709 FA Chimezie Charles Ofoha Ph.D., Department of Physics, Edwin Clark University, Kiagbodo, Delta State, Nigeria Ikechukwu Chukwuocha Ph.D. Student, Department of Physics, University of Port Harcourt, Port Harcourt, Rivers State, Nigeria Chukwuemeka Ngozi Ehirim Professor, Department of Physics, University of Port Harcourt, Port Harcourt, Rivers State, Nigeria Journal Article 2025 06 22 <span>Geoelectrical methods integrated with physicochemical analyses of borehole samples were employed to determine groundwater contamination levels in the area. Vertical electrical sounding (VES) and 2D resistivity techniques were conducted along the area's four transverses. The field data were processed using the RES2DINV and IPI2WIN software. Groundwater samples were collected from three boreholes in the area and one borehole outside the mechanic village area as a control. The results of the VES indicated that at depths beyond 18 m, resistivity greater than 200 Ωm suggested that fresh gasoline oil spills increased the electrical resistivity of the groundwater. Additionally, at depths beyond 2 m, with a resistivity range of less than 85 Ωm, biodegraded hydrocarbon spills in the auto mechanic village were evident, making the groundwater less electrically resistive. The 2D resistivity results showed two types of anomalies: high and low resistivity zones. The high resistivity zones indicate uncontaminated areas, while the low resistivity zones indicate contaminated areas. The physicochemical analyses and heavy metal groundwater samples revealed that gasoline oil infiltrated the subsoil down to the water table as a free-phase hydrocarbon. The depths of the water table and aquifer extended beyond 10 and 36 m, exhibiting high resistivity ranges greater than 287.7 and 548.6 Ωm, respectively. In conclusion, the gasoline oil spills saturate the unsaturated zone and subsequently leach into the groundwater aquifer at depths beyond 18 m, showing a high resistivity range greater than 350 Ωm. </span> <span>Geoelectrical methods integrated with physicochemical analyses of borehole samples were employed to determine groundwater contamination levels in the area. Vertical electrical sounding (VES) and 2D resistivity techniques were conducted along the area's four transverses. The field data were processed using the RES2DINV and IPI2WIN software. Groundwater samples were collected from three boreholes in the area and one borehole outside the mechanic village area as a control. The results of the VES indicated that at depths beyond 18 m, resistivity greater than 200 Ωm suggested that fresh gasoline oil spills increased the electrical resistivity of the groundwater. Additionally, at depths beyond 2 m, with a resistivity range of less than 85 Ωm, biodegraded hydrocarbon spills in the auto mechanic village were evident, making the groundwater less electrically resistive. The 2D resistivity results showed two types of anomalies: high and low resistivity zones. The high resistivity zones indicate uncontaminated areas, while the low resistivity zones indicate contaminated areas. The physicochemical analyses and heavy metal groundwater samples revealed that gasoline oil infiltrated the subsoil down to the water table as a free-phase hydrocarbon. The depths of the water table and aquifer extended beyond 10 and 36 m, exhibiting high resistivity ranges greater than 287.7 and 548.6 Ωm, respectively. In conclusion, the gasoline oil spills saturate the unsaturated zone and subsequently leach into the groundwater aquifer at depths beyond 18 m, showing a high resistivity range greater than 350 Ωm. </span> https://www.ijgeophysics.ir/article_226465_cb972dbe36c53bba66e2df440f17e9b5.pdf