Geo-electrical evaluation of leachate infiltration into the aquifer of the agirifon dumpsite, Ilutitun Southwest Nigeria

Abstract

The effect of leachate inltration from the Agirifon dumpsite to the aquifer system of Ilutitun was investigated using the Electrical Resistivity methods. The investigation was aimed at determining the geoeletric geometry of leachate plume at the subsurface of the dumpsite. Six traverses were established to cover the entire study area, Dipole-Dipole electrode configuration was employed using electrode separation of 5m and 10 m. The expansion factor n was varied from 1-5meters and 1-10meters respectively. The 2-D resistivity structures delineated virtually a single type of subsurface formation (Coastal Plain Sands) which can be divided into three zones; the topsoil or upper zone made up of sandy clay/clayey sand/sand, the intermediate zone made up of clayey sand/sand and the lower zone majorly made up of sand. The three zones generally transit into one another. The 2-D Resistivity imaging revealed a radial migration of leachate in the range 7.2Ωm in the NW/SW direction of the study area from the topsoil to a depth of 30 m beneath the dumpsite facility. The leachates were observed to have infiltrated through the porous and permeable layers into the subsurface aquifers, subsequently contaminating the underlying groundwater resource. It could therefore be concluded that the leachates produced from the dumpsite has gradually inltrated into the subsurface (shallow and deep) aquifers in the study area.