SOIL CORROSIVITY AND OVERBURDEN PROTECTIVE CAPACITY OVER AQUIFER SYSTEM IN KWAL KANKE NORTHENTRAL NIGERIA

Abstract

A geophysical survey was carried out in Kwal, Kanke Local Government Area of Plateau State,
northcentral Nigeria using electrical resistivity soundings method. This study aimed to demarcate
zones that are very susceptible to groundwater contamination from surfacepollutants and
subsurface soils that are corrosive to utility pipes. Schlumberger configurations were used to
delineate the subsurface geologic layers, corrosivity level and aquifer protective capacity. Fourty
(40) Vertical Electrical Sounding (VES) data were acquired using ABEM Terrameter SAS 300B
and ABEM 2000 booster resistivity meter with half-current electrode separation (AB/2) of 1 to
125 m. The interpretations of the data collected were aided by computer assisted iterative using
the computer iteration algorithm WINRESIST Version 1.0, MS Excel 2016 and surfer 11
software. The curve types obtained include: A, Q, H, K, AK, HA, QH, AA, KH and HK types.
Four (4) distinct geoelectric layers were identified namely: topsoil, clayey layer, fractured
basement and fresh basement. The topsoil is composed of moderately corrosive materials
depicted with green colour having resistivity values in the range of 10 to 60 Ωm with frequency
distribution of 22.50%. Slightly corrosive materials with resistivity values of 60 < ρ < 180 Ωm
and frequency distribution of 57.50% is symbolized with yellow colour while the practically
non-corrosive with resistivity values in excess of 180 Ωm have 20.00% frequency distribution
represented with pink colour. The second layer is made up of moderately corrosive materials
having resistivity values in the range of 10 to 60 Ωm (green colour) with frequency distribution
of 30.00%. Slightly corrosive materials having resistivity values of 60 to 180 Ωm have frequency
distributions of 20.00% is denoted with yellow colour. The practically non-corrosive portions
have resistivity values above 180 Ωm and frequency distribution values of 50.00% are depicted
with pink colour. Zones of moderate (pink colour), weak (green colour) and poor (yellow colour)
overburden protective capacity were delineated, with longitudinal conductance (S) values of 0.2
< S < 0.69, 0.1 < S < 0.19 and S < 0.1 mhos, respectively. On a regional consideration, 25.00%,
52.50% and 22.50% of the study area is characterised by overburden materials of poor, weak and
moderate protective capacity respectively. The measured overburden thickness ranges from 2.6 to
29.6 m. Zones of moderate protective capacity have thick aquifer with thick clay materials above
the aquifer that act as seal while areas with poor to weak protective capacity are susceptible to
infiltrating contaminating fluid.