Determination of Aquifer Geometry and Assessment of Groundwater Quality in some Parts of Benin Metropolis, Nigeria

Abstract

There is thus the need to assess the quality of groundwater sources because water quality assessments form an important aspect of environmental studies. This study is aimed at understanding the aquifer geometry and assessing the quality of groundwater of two boreholes 4.2 km apart at Okabere on 6o1.6’23.6’’N and 5o39’38.6’’E and Evbuabogun on 6o1.6’23.6’’N and 5o39’38.9’’E in Recent to Miocene Benin Formation (FM) Benin City, South-South Nigeria. Water and soil samples from the borehole were collected and analysed for physico-chemical parameters, grain size and heavy minerals analysis using standard laboratory method while heavy metals were determined with Atomic Absorption Spectrometer (AAS) unican series model 969 with air acetylene flame. The results obtained revealed that PO4 3-, K+, Cr+6, Ni+, Pb+2,Fe+2, were above the maximum threshold value permissible for drinking water proposed by WHO. The aquifer are shallow ranging with depths 54.90m and 45.76m respectively, grain size analysis revealed that the aquifer geometry were semi confined to unconfined and mainly of fine to coarse sand grains with intercalation of clay/shale. Heavy mineral analysis shows a preponderance of zircon, rutile, staurolite, gamet, tourmaline and kyanite suggesting that the sediments were from basement complex source. The foregoing revealed that the aquifer is vulnerable to contamination, the authors’ advocates for routine treatment of such water before consumption while remediation measure is advice.