ASSESSMENT OF POTENTIAL LEACHATE MIGRATION AND WATER QUALITY AROUND THE KABAMA MUNICIPAL SOLID-WASTE DUMPSITE, ZARIA, NIGERIA, USING VLF-EM EL AND PHYSICOCHEMICAL ANALYSIS

Abstract

Groundwater and surface-water contamination by municipal solid waste (MSW) leachate is an important environmental concern, particularly in rapidly urbanizing areas where inadequate waste management can promote contaminant infiltration. This study assessed potential leachate migration and water quality around the Kabama municipal solid waste dumpsite, Zaria, northwestern Nigeria, using Very Low Frequency Electromagnetic (VLF-EM) surveying and physicochemical analysis of water samples. Six VLF-EM traverses were conducted across the dumpsite, with measurements acquired at 5 m station intervals and processed using Fraser and Karous–Hjelt filtering techniques to delineate subsurface conductive anomalies. In addition, two hand-dug well-water samples and one stream-water sample were collected and analysed for pH, electrical conductivity (EC), total dissolved solids (TDS), biochemical oxygen demand (BOD), chemical oxygen demand (COD), chloride, and selected heavy metals. The VLF-EM results revealed several pronounced conductive anomalies from near surface to an apparent depth of about 25 m across the investigated profiles, particularly within and around the dumpsite, indicating zones of enhanced subsurface conductivity potentially associated with leachate-affected materials, clay-rich units, or buried metallic waste. The physicochemical results showed pH values of 6.57, 6.71and 6.51 for the well, stream and control well samples, respectively, while EC values were 850, 984 and 800 µS/cm and TDS values were 620, 671 and 350 mg/L. Elevated organic pollution indicators were observed, with BOD values of 415, 523 and 50 mg/L and COD values of 745, 751 and 35 mg/L. Chloride concentrations were 314, 479 and 100 mg/L, while Pb, Fe, and Mn concentrations ranged from 0.051, 0.060 and 0.011; 0.310, 0.403 and 0.290; then 0.163, 0.191 and 0.050 mg/L, respectively. These elevated concentrations indicate deteriorating water quality near the dumpsite. Increases in the physicochemical parameters measured in water samples from the existing well and stream suggest that solid waste leachate deposition has contaminated the groundwater, supporting the geophysical data.