Evaluation of petroleum hydrocarbons contamination in soils and groundwater using electrical resistivity and hydrochemical methods-Case study: Ayetoro, Osogbo southwestern Nigeria

Abstract

The presence of Petroleum Hydrocarbons (PHCs) in hand-dug wells has become a concern to the residents of Ayetoro area, Osogbo. Consequently, the detection of PHCs was evaluated using, nine Vertical Electrical Soundings (VES) and 2D electrical resistivity tomography surveys. Soil samples collected were analyzed for porosity and permeability. Hand-dug well water samples were screened for PHCs. VES revealed that second layer had high apparent resistivity of 14415.0 Ωm, indicating presence of PHCs that had penetrated to maximum depth of 19.1 m. The highest resistivity of the control points was 48.0 Ωm, indicating absence of PHCs. The 2D resistivity revealed highest value of 3622 Ωm and had migrated to a depth of 10.0 m. The porosity (0.40) and permeability (6.87516 x 10^–4 cm/s) were typical of silty clay which allowed passage of PHCs. Hydro-chemical analysis indicated presence of PHCs (0.50–11.00 mg/L). The study has established presence of PHCs in soils and hand-dug wells.

Keywords: Petroleum Hydrocarbons, Soil, Groundwater, Electrical resistivity tomography