Application of expanding probe electrical resistivity method in delineating leachate contamination zone at Farri Open Dumpsite, IJEBU ODE, Southwestern Nigeria

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Abstract

An evaluation of subsurface contamination in the Farri dumpsite area of Ogun State, Southwestern Nigeria, has been carried out with the aim of determining the degree of contamination and infiltration of leachate into the subsurface soil using the vertical electrical sounding (VES) method. Twenty VES points were probed using the Schlumberger array with a current electrode spacing (AB/2) of 80 m. The resistivity values recorded were processed via the partial curve matching approach, and modelling with WINRESIST software was employed to generate the geoelectric parameters of the subsurface. The interpretation of the data obtained shows the presence of three underlying lithological layers with Q and H geophysical curve type geometry. The lithological layer present in the study area includes topsoil, clayey, sandy clayey and compacted sandy layer with resistivity values ranging from 10.9 to 1091.3 Ωm, 11.4 to 110.9 Ωm, 141.7 to 275.6 Ωm and 1293.7 to 9880.9 Ωm. Overburden thickness varies from 0.5 to 3.2 m across the study area. Three contamination categories (uncontaminated, moderately contaminated and contaminated) were adopted for rating contamination. The geospatial representation of the calculated longitudinal conductance shows that the protective capacity is low in the northwestern part, moderate within the central region, and high in the southeastern and southern parts of the study area.

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NRIAG Journal of Astronomy and Geophysics
Volume 14, Issue 1
December 2025
Pages 1-13

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