IMPACT OF LANDFILLS ON GROUNDWATER QUALITY USING HYDROCHEMICAL AND ELECTRICAL RESISTIVITY METHODS AT APETE/AWOTAN AREA, IBADAN, SOUTHWESTERN NIGERIA

Abstract

Water is one of the determinants of the human-earth system. Diseases may spring up through water pollution, especially groundwater contamination, and rapidly spread beyond human expectations because of its flow mechanism. This study aims to assess the impact of landfills on groundwater quality in Apete/Awotan area, Ibadan, Oyo State, Southwestern Nigeria using The Electrical Resistivity and hydrochemical methods. The Electrical Resistivity method involves the use of 2D Electrical Resistivity Tomography (ERT) and Vertical Electrical Sounding (VES) techniques. The hydrochemical method involves the collection of seven water samples from boreholes and hand-dug wells, with sampling depths ranging from 9 to 75 m. Sixteen VES were carried out using Schlumberger array with current electrode spacing varying from 1 to 65 m, with 2-D ERT using Wenner array with an electrode spacing of 5 m interval and was used to determine the subsurface lithologies. The results from both methods indicate high levels of chemical contamination of the water from the boreholes and well water within and outside the dumpsite to a distance of 20 m away; health problems such as typhoid fever or worm infestation are imminent when such water is consumed. Good correlations exist between the Electrical Resistivity results and hydrochemical analysis for contamination in some strategically located notably S1, S2, and S3. 30 m away from the dumpsite are yet to be contaminated and can be relatively said to be of good water quality based on their locations and anions concentrations falling within the maximum permissible limit for water constituents by the World Health Organization.