Investigating groundwater corrosion and overburden protective capacity in a low latitude crystalline basement complex of southwestern Nigeria

Abstract

ABSTRACT The total longitudinal conductance S obtained from the interpretations of vertical electrical soundings data acquired near 40 well bores was calibrated using total dissolved solids (measured in situ) in the sampled wells’ groundwater to determine the overburden protective capacity and groundwater corrosion in a crystalline basement complex of Ogbomoso North, southwestern Nigeria. The acidity (pH) and electrical conductivity (EC) were also measured. Groundwater corrosiveness was determined using the Langelier saturation index (LSI) and the aggressive index (AI). The computed S of predominantly H-, KH-, QH-, HA- and HKH- types resistivity curve was 0.037995– 1.10878 mhos. The TDS, pH and EC of the water samples measured 36–747 ppm, 6.15–9.3 and 74–1491 μS/cm, respectively. The regression equation of the TDS-based S calibration curve indicates a strong positive correlation (R2 = 0.8932) and revealed the overburden protective capacity ranged from excellent to good, fair and poor. The computed LSI and AI were −3.61 to 1.2 and 7.8–12.8, respectively. The high values of both LSI (0.2–1.2) and AI (11.2–12.8) in the southwestern part suggest groundwater there is strongly corrosive, while low values of −3.6 to −1.2 and 7.8–10.2 in the northwestern and southeastern parts indicate non-corrosive groundwater.