Delineating Leachate Plume Migration at the Alaro Municipal Dumpsite using Electrical Resistivity Imaging

Abstract This study aimed to map and assess the environmental degradation caused by unmanaged municipal solid waste disposal at the Alaro municipal dumpsite in Southwestern Nigeria, with a focus on leachate contamination. Electrical resistivity imaging (ERI) was applied to define the subsurface geology of the area using five resistivity profiles acquired with a dipole-dipole electrode configuration. Each electrode transect spanned 100 meters with dipole spacings ranging from 2 m to 12 m. Analysis of the uncontaminated segment of the subsurface geology revealed a three-layered geo-electric (lithologic) succession, with resistivity ranges characteristic of loose alluvium, hybrid stratum, and faulted sandstone. Significant decreases in resistivity values, from 3 Ωm to 182 Ωm, were observed around and within the dumpsite, indicating extensive surface contamination by leachate. Three contamination zones were further characterized as leachate-saturated, leachate-concentrated, and leachate-infiltrated sands. In the study area, leachate infiltration extended to a depth of 20 meters, with a marked resistivity contrast between clean and contaminated segments. The likelihood of a normal fault along the control profile further justify leachate migration concerns, highlighting the severity of environmental pollution within the Quaternary sand formation. The contaminated segment poses a significant environmental hazard, that requires immediate mitigation action. Waste recycling, biomass energy generation, and the application of geotextile materials should be prioritized to remediate the dumpsite.