Application of three dimensional (3d) electrical resistivity imaging (eri) technique in a study conducted on oil contaminated experimental site in biust, palapye, botswana.

This study was aimed at evaluating the utility of electrical resistivity imaging (ERI) method in investigating and monitoring sites contaminated by spillage of oils. The geophysical investigation involved acquiring electrical resistivity data along eight (8) parallel profiles of 7.99 m length, using a dipole-dipole electrode configuration with a separation of 0.5 m between profiles and 0.17 m between electrodes. The initial ERI measurements were acquired before the oil contamination and the subsequent four datasets were acquired after the site was contaminated with engine oil, on a two weeks interval basis. The ERI datasets were inverted using the Res3Dinv and in ERTLab^TM 3D inversion and modeling software packages. The inversion of the datasets generated resistivity models and isosurfaces showing the distribution of electrical resistivity values. The 3D inverse resistivity models indicate that the contaminated zone at the site has relatively high resistivity values. The isosurface images indicate that the oil contamination is restricted to a depth range of 0.1 m to 0.8 m for the second dataset and to a depth range of 0.1 m to 0.4 m at the end of the experiment. This pattern was also evident in the horizontal sections from layer 2 (depth: 0.06-0.13 m) to layer 9 (depth: 0.82-1.00 m) in the second dataset models and from layer 3 (depth: 0.13-0.21 m) to layer 6 (depth: 0.40-0.52 m) at the end of the experiment. Both images reveal low resistivity clay dominated soils at the surface, in regions flanking the oil contaminated zone, and beneath the oil contaminated soil material.