Groundwater quality assessment and subsurface mapping at a reclaimed waste dumpsite in Enugu, Nigeria: implications for sustainable urban development

This study assesses groundwater Quality and subsurface lithology in a residential area built on a reclaimed municipal waste dumpsite in Enugu, Nigeria. It addresses the potential environmental and health impacts of such sites, aligning with SDG 6 (Clean Water and Sanitation) and SDG 11 (Sustainable Cities and Communities). The objectives include groundwater Quality evaluation, subsurface characterization, and groundwater suitability assessment. Water samples from hand-dug wells were collected during both rainy and dry seasons over 2 years. Electrical Resistivity Tomography (ERT) was employed to identify subsurface leachate pathways, while Atomic Absorption Spectrometry (AAS) was used to analyze eight heavy metals and 13 physicochemical parameters for groundwater quality index (WQI) calculation. ERT results revealed zones of low resistivity (0.5–7 Ωm) at depths of 5–16 m, indicating leachate presence. These zones were bordered by moderately resistive lateritic materials (58–199 Ωm). Most parameters fell within WHO permissible limits, except for cadmium (dry, 0.02 mg/L; wet, 0.17 mg/L), cobalt (dry, 0.02 mg/L; wet, 0.04 mg/L), temperature (dry, 28 °C; wet, 25 °C), and TSS (dry, 290 mg/L; wet, 110 mg/L). During the dry season, lead (0.15 mg/L) and total solids (TS) (720 mg/L) exceeded acceptable limits. pH values were slightly acidic, ranging from 5.0 (dry) to 5.5 (wet). The WQI scores of 987 (dry) and 3005 (wet) indicated high contamination in both seasons. Statistical analysis showed no significant seasonal variation in contaminant levels. Overall, geophysical and laboratory findings confirm that the groundwater is highly contaminated and poses serious health risks to residents.