Integrated Geophysical and Geochemical Evaluation of Groundwater Vulnerability to Open Dumpsite: A Case Study of Part of Zango-Daji Groundwater, Lokoja, North Central Nigeria

This study aimed to assess the impact of dumpsite leachate plume on groundwater in Zango Daji, within Latitude 7⠰46’00†N to 7⠰50’00†N and Longitude 6⠰37’00†E to 6⠰41’00†E. It utilized geophysical methods, including six electrical imaging lines (three 2D resistivity and three Induced Polarization), nine Vertical Electrical Sounding (VES) data points, and groundwater analysis. The data were quantitatively and qualitatively processed using RES2DINV, WINRESIST and SURFER software. 2D resistivity and IP profiles taken at the dumpsite showed low resistivity (11.7–51.8 Ωm) and chargeability (-0.7 to 1.45 msec) in the topsoil and fractured basement zones, indicating leachate migration pathways. A profile 100 m west of the dumpsite showed moderate resistivity (11–422 Ωm) and chargeability (2–6.2 msecs), suggesting a clayey lithologic cover, which act to impede leachate plume flow to the subsurface groundwater. The eastern profile had lower resistivity (29–299 Ωm) and chargeability (>2.7 msec), indicating contamination. The VES results aligned with the 2D resistivity findings. Geochemical analysis of five water samples revealed slightly acidic to alkaline conditions, with cation concentrations following the order Ca > Na > Mg > K and anion concentrations Cl > SO4 > HCO3. Most physiochemical parameters were within WHO (2017) limits, except for chloride, TDS, COD, and lead, which exceeded limits at and east of the dumpsite. The eastern area’s low resistivity and chargeability were linked to elevated physiochemical parameters, likely due to contamination from the dumpsite. Geochemical plots indicated chlorine dominance in groundwater. The study concluded that groundwater quality was affected by anthropogenic activities rather than natural rock-water interactions, with contamination more evident in the eastern zone.