The Geophysical Investigation of Leachate Formation in Mgbuka Obosi, Idemili North Local Government Area of Anambra State, Nigeria

Abstract

The contamination of leachates (a polluted liquid made up of various toxic substances) from landfills is a significant environmental concern, especially in developing countries.This contaminated fluid is formed when rainwater interacts with refuse and travels through the pore spaces in soil. Constant migration of this fluid poses a significant threat to the quality of both surface and groundwater in and close to the landfill area. To determine the extent of leachate formation, the study used both Very Low-Frequency Electromagnetic (VLF-EM) and Electric Resistivity Tomography (ERT) to locate and define the spatial distribution of the leachate plume migration pathway at Mkpuka Obosi Dumpsite in Idemili North LGA of Anambra, Nigeria. Seven profiles were surveyed for both the VLF-EM and ERT. The VLF-EM survey, with a profile length of 100 to 200m and a 10m interstation spacing, revealed the presence of a conductive pollutant (leachate plume) in the subsurface. The results from the 2D ERT survey that employed a Wenner array with a profile length of 100 to 200m and an electrode spacing of 5m, divided the subsurface into six zones with an unusually low resistivity ranging from 0-250\(\Omega\)m. The leachate plumes were interpreted as the zone with the lowest resistivity of 0 to 25\(\Omega\)m, having an average thickness of approximately 10m and extending beyond the probed depth of 50m. Additionally, the percentage of leachate was found to be concentrated primarily at the center of the landfill and gradually decreasing proportionally from the center. Thus, emphasizing the importance of addressing the issues in landfill management.