Evaluation of groundwater quality in Shakwatu community, part of Sheet 164 SW, Central Nigeria

Abstract

Geology, mineralogical composition of rocks and geotechnical properties (grain size and permeability) of the soil within the river in Shakwatu and environs part of Sheet 164 SW were studied. Physico-chemical characteristics of groundwater collected from boreholes, hand dug wells and river were also determined. Statistical techniques where applied to the groundwater samples to determine hydro-geochemical parameters in order to establish the relationship among the measured parameters and their sources. Results show that the area is part of the Kushaka schist belt that have been intruded by faulted gneiss, granites and quartzite. The mineralogical composition of the rocks includes biotite, feldspar and quartz. The soils falls under A – C group that consist of poorly sorted sand with low fines and are of medium to high permeability as shown from the result (2.434x10-02). The permeability of the soil could aid in the infiltration of harmful wastes from the illegal mining activities that is prevalent in the area.From various statistical analysis the cations (Ca2+, Mg2+, Na+, K+) and anions (Cl-, HCO3-, CO32-, SO42-, F-, NO3-, NO2-, PO43) fell within WHO and NSDWQ recommended standards. The dominant water type is CaHCO3 followed by CaNaHCO3 water type. Rock weathering and cation exchange are the major geochemical processes responsible for the water chemistry in the study area. The quality of the groundwater need to be monitored from time to time as well as improving the mining method in order to ensure safety of the groundwater. Twelve (12) water samples were collected and subjected to analysis according to APHA (2008) procedure. Twenty one (21) parameters were determined, namely, turbidity, pH , conductivity, Total Dissolved Solids (TDS), chloride, nitrite, bicarbonate, manganese, zinc, sodium, chromium, arsenic, calcium, copper, magnesium, sulphate, potassium, iron, carbonate, cadmium, lead. The revelation of the result shows the pH of the water samples ranges from 6.16 -7.47indicating a slight acidity to alkalinity of the groundwater. The presence of dissolved ions implies the wide variation between the maximum value and minimum value of Total Dissolved Solid (TDS) (1,105 mg/l) (42mg/l), electrical conductivity (EC) (1,700µ/cm) (64 µ/cm). The wide variation of the TDS does not pose any threat, but cases of TDS higher than NSDWQ and WHO permissible limit, it will affect the aesthetic acceptability, and taste of the groundwater in the study area. Chromium value ranges from 0mg/l to 10mg/l, with the highest value at the mining pit; this is a result of indiscriminate disposal of mine water.