Geophysical Assessment of Groundwater Contamination at the Sabo Waste Dumpsite in Okitipupa, Southwestern Nigeria

Abstract

Electrical resistivity method is one of the geophysical methods that have been found effective in investigating the subsurface and evaluate the impact of dumpsite on soil and groundwater. This was carried-out around Sabo waste dumpsite, Okitipupa, southwestern part of Nigeria. The geophysical investigation involve the techniques of electrical resistivity geophysical methods using vertical electrical sounding in order to investigate the groundwater quality of the study area as it happens to fall on an abandoned dumpsite area turned to residential area. A total of nine (9) traverses were established in the SE to NW, NW to SE and S-N orientation covering a total distance of 100m and a total of seventeen (17) vertical electrical soundings were acquired. Seventeen (17) vertical electrical resistivity (VES) stations were established using schlumberger configuration with half-current electrode spacing that ranged from 1 to 100 m while dipole–dipole profiling was carried-out along Nine (9) profiles. Results show that the typical curve types in the area are A, K and H curves. The vertical electrical Sounding (VES) interpreted result delineated three subsurface layers comprising, the topsoil, clay/clayey sand and sandy clay. While the dipole–dipole result shows that the topsoil and clay layer has been virtually merged with characteristic 12.6-76.5 Ωm It was observed on the results of the two techniques that the dumpsite has generated a leachate within the subsurface that are conductive and give rise to the low resistivity within the abandon dumpsite to the depth of about 22m, whereas in the control traverse, there are high resistivity that indicate the area has not been contaminated.