keywords: Leachate, groundwater, vertical electrical sounding, very low frequency, contaminant
The impact of leachate produced from waste on the soil and groundwater was studied in this research. Geophysical methods involving very low frequency (VLF), vertical electrical sounding and 2D electrical resistivity tomography (2D ERT) was adopted to investigate the impact of leachate on the geologic materials. Five traverses of the VLF survey were carried out at the study area to locate possible conductive zones and vertical electrical sounding coupled with 2D ERT on the established conductive zones. The VLF field data were analyzed using the Karous Hjelt and Microsoft excel software, WinResist for the VES and Res2DInv was used to analyze the 2D ERT data. The VLF result of the study area shows that few conductive zones even though the method was adopted as a reconnaissance method. The lithological unit acquired from the electrical resistivity result revealed topsoil, leachate infiltrated stratum, wet sand/ dry sand and sandy clay. The topsoil has resistivity value ranging from 12-895 Ωm, leachate infiltrated stratum having resistivity value ranging from 8 – 79 Ωm, dry sand with resistivity value of 149 – 4058 Ωm and sandy clay with resistivity value ranging from 752-1316 Ωm. The result of the integrated methods shows that larger portion of the dumpsite is polluted as a result of the permeable materials. From the results obtained, it shows that the entire dumpsite is not polluted yet, but may get polluted in future.