Hydrogeochemical and Geoelectrical Characterisation of Groundwater around Agudu, Egbeda Area, Ibadan, Southwestern Nigeria

Abstract

Water is an essential resource for the sustainability of the human race and other biotic lives. This study emerged from variation observed in the groundwater distribution coupled with its quality within the Agudu neighbourhood. This investigation was centred on the geophysical and geochemical characterizations of the aquiferous units. Electrical resistivity method involving Vertical Electrical Sounding (VES) technique and geochemical assessment of groundwater were adopted for the study. A total of twenty VES points were occupied using the Schlumberger electrodes array and the current electrode separation (AB/2) ranged from 2 to 80 m. The data were subjected to both manual processing and computer base iteration using WinResist software. Twenty water samples were collected from wells across the community and subjected to physicochemical assessment. Flame photometry was used in analyzing the cations (Mg2+, Ca2+, Na+ , K+ ) while spectrophotometry was used for chloride, sulphate, bicarbonate, and nitrate. The VES sections revealed two to five geo-electric layers, the weathered and the fractured units were the aquiferous zones. The Dar-Zarrouk parameters were used in establishing the groundwater potential map and classifying the aquifer potential zones. The concentration of major cations was in the order Ca2+>Mg2+>Na+>K+ while that of anions were HCO3>Cl->SO4 -2>NO-3 . The pH values fall within the World Health Organisation’s recommended value, it ranged from slightly acidic to slightly alkaline. All the parameters fall within the permissible level except Ca2+ and water hardness at some locations. The techniques engaged were able to reveal the groundwater distribution and also characterised the chemistry of groundwater.