Assessment of Groundwater Contamination Using Geo-Electric Methods in Aba, Abia State

This study applies geo-electric methods to assess the extent of groundwater contamination associated with industrial waste disposal in Aba, Abia State, South East Nigeria. Aba is one of Nigeria's most densely industrialised cities, and unregulated disposal of effluents from leather tanning, textile dyeing, and chemical manufacturing into open pits and unlined lagoons poses a significant threat to shallow aquifer water quality. This study uses a combination of Schlumberger vertical electrical soundings and Wenner electrical resistivity profiling along eight traverses around three major industrial waste disposal sites in Ogbor Hill and Aba South. A total of 24 VES stations and 3.2 kilometres of profiling data are acquired. Resistivity interpretation identifies anomalously low-resistivity zones indicative of electrolytic contamination of shallow sands. Water samples from 18 hand-dug wells within and outside the identified low-resistivity anomaly zones are analysed for pH, total dissolved solids, heavy metals, and bacterial indicators to validate the geophysical interpretation. Findings reveal a correlation between low resistivity values below 5 ohm-metres and elevated total dissolved solids exceeding 1,500 milligrams per litre and heavy metal concentrations above WHO guidelines in wells located within 200 metres of disposal sites. The contamination plume extends approximately 350 metres downgradient from the principal disposal site, following the local hydraulic gradient. The study concludes that geo-electric mapping effectively delineates the contamination plume geometry and recommends its integration into Aba's urban groundwater protection planning framework.

Keywords: geo-electric methods, groundwater contamination, industrial waste, Aba, resistivity profiling.