LEACHATE-INDUCED SOIL MINERALOGICAL ALTERATIONS AT THE GOSA DUMPSITE IN ABUJA, NIGERIA

Abstract

The exponential rise in Municipal Solid Waste (MSW) production driven by global urbanization necessitates a critical assessment of dumpsite leachate's impact on underlying soils. This study investigates the leachate-induced mineralogical alterations at the Gosa dumpsite in Abuja, Nigeria, focusing on two distinct AASHTO soil types: A-2-4 (sandy) and A-7-6 (clayey). Geochemical analysis characterized the leachate with a pH of 9.3 and an exceptional Electrical Conductivity (EC) of 38,700 µS/cm. Key contaminant concentrations were extremely high, including Chloride (Cl) at 3,980 mg/l and a Chemical Oxygen Demand (COD) of 6,380 mg/l. Elevated levels of heavy metals like Chromium (Cr) at 10.46 mg/l and Lead (Pb) at 4.23 mg/l were also detected. Quantitative XRD test determined the weight percentage (wt %) of crystalline phases. Key mineralogical alterations included the dissolution of primary minerals, such as feldspar and clay, and the precipitation of new, secondary mineral phases, specifically gypsum (CaSO₄.2H₂O) and iron oxides/hydroxides. Crucially, the clayey A-7-6 soil exhibited a demonstrably more pronounced reaction compared to the sandy A-2-4 soil, confirming its superior intrinsic natural attenuation capacity due to higher reactive surface area. These findings underscore the profound, soil type dependent changes in mineralogical composition, highlighting the necessity for advanced quantitative assessment and robust leachate management strategies to mitigate environmental and geotechnical risks at the site.