Integrating electrical resistivity, geotechnical and geochemical techniques to assess soil and groundwater resources near Warri refinery, Niger Delta, Nigeria

Abstract

Underground water resources and soil are increasingly under threat due to refining activities near a residential area. Hydrocarbon contamination of groundwater and soil near the refinery in the Western part of the Niger Delta was carried out using the integrated techniques of electrical resistivity tomography (ERT), induced polarization, geotechnics, and geochemistry. Electrical imaging of the subsurface along the traverses in the site was taken through the use of an earth resistivity meter. Permeability of the soil was determined using a variable head permeameter and geochemical parameters of groundwater were deduced in an analytical laboratory. The resistivity imaging range is 10–2568 Ohm m, reflecting varying resistivity levels associated with lithology and liquid type. Low chargeability of 1–15 ms recorded in most parts implies that the sand has been infiltrated by a high-resistive plume. This low conductivity contaminant may be caused by hydrocarbon intrusion. The typical permeability of the soil is 6.00 × 10^–5 m/s, indicating fairly good drainage conditions. Groundwater sample analysis shows slight acidity with a pH value of 5.3–6.6. Conductivity ranges from 74.50 to 119.60 µS/cm, while Total Dissolved Solids (TDS) is 51920 to 69,350 µg/L. Iron content is slightly high (645–977 g/L). Gas chromatography (GC) examination reveals that oil and grease as total petroleum hydrocarbons (TPH) is > 31 µg/L. The impermeable clay before the confined aquifer filters the TPH, which accounts for its low quantity in the water samples. The results have shown that the area has been degraded. It could be recommended that periodic integrated methods be carried out in the area.