Hydro-geochemical and Geophysical Study of Groundwater in the Suburb of Osogbo, South Western Nigeria

Abstract

In an attempt to carry out the assessment of groundwater quality from hand dug wells and streams in Onibu-Eja and Aduramigba communities, suburb of Oshogbo, South Western Nigeria, with a view to determine the impact of a nearby dumpsite on the groundwater quality, twenty (20) water samples were taken randomly at varying depths within the vicinity. The cation and heavy metal analyses were done in accordance to APHA standard using the Atomic Absorption Spectrophotometry (AAS) while the anion analyses were carried out using the ion chromatography and titrimetric methods. Physical parameters were measured on the field. The results observed showed that the water in the study area contains a relatively high amount of calcium, magnesium, and bicarbonate, an indication of temporary hardness. The hydro-geochemical contour maps of the ions shows that cations, anions and heavy metal content where mostly concentrated in the western and eastern parts of the study area. The analyses of the water samples and streams in the study area fall within the acceptable range of World Health Organization (WHO) and the Nigerian Standard of potable drinking water with the exception of the stream despite their proximity to the dumpsite. Vertical Electrical Sounding (VES) carried out on the dumpsite showed that the study area is overlain by a 0.3 to 1.1 m thick lateritic topsoil with resistivity values between 104 ohm m and 437 ohm m which serves as a hard pan over a 7 to 13 m thick predominantly clayey / weathered layer interval with a resistivity value between 35 to 80 ohms meter. Both of these prevent the leachate from percolating into the groundwater in the study area.