Hydrochemical characterization and evaluation of groundwater quality of zamfara area, northwest, nigeria

Abstract

This study deals with hydrochemical assessment of groundwater within the lithological framework underlain Zamfara State, Northwestern Nigeria with the aim of ascertaining its suitability for human consumption. Groundwater samples were collected from boreholes tapping the aquifer of the area and analyzed for various physico-chemical parameters, such as total dissolve solids, electrical conductivity (Ec), pH, temperature, Na⁺, K⁺, Ca²⁺, Mg²⁺, HCO₃, Cl^-, SO₄, NO₃, PO₄, and trace elements (Mn, Cu, Zn, Fe, Pb and Cr). The results obtained were subjected to multivariate statistical analysis, water quality index method, and hydrochemical variation plots for proper characterization. As far as suitability is concerned most of the studied physic-chemical parameters trace elements (iron, lead and chromium ions) revealed average concentrations lower than the permissible limit set for domestic water use by World Health Organization. However, the compiled overall water quality index for the studied groundwater shows ‘very poor water quality’. Due to the fact that WQI rating reflect the composite influence of different water quality parameters. The result of the multivariate statistical analysis, as applied to the chemical data set of the studied groundwater provides an insight into the underlying controlling hydrochemical processes in the area. Four factors including factor-1 (total hardness, chloride, nitrate, manganese, bicarbonate and alkalinity), factor-2 (TDS, conductivity, total hardness, magnesium and calcium), factor-3 (Temperature, sodium, potassium, copper, zinc, iron and chromium), factor-4 (calcium, magnesium and nitrate) represents the signatures from dissolution of bedrock through which the groundwater passes, ionic mixing, leaching from the lateritic overburden, agricultural activities (fertilizer application) and effluent from waste dumpsites in the study area. The distribution of major ions in the groundwater shows relative abundance of cations: Na⁺+K⁺ > Ca²⁺ > Mg²⁺; while the relative abundance of the anions is: Cl^- > HCO₃^- > SO₄^2-. Groundwater in the aquifer of the study area are majorly of evolved type with mixing of ionic concentrations. Alkali’s are more in abundant to that of alkaline earth, while Cl and HCO₃ dominate SO₄ and NO₃ concentration. The water samples are basically ‘Alkali waters’ with ‘Earth Alkaline’ components that are predominantly HCO₃^- and Cl^-.The relative abundance of the three (3) dominant water types are as thus: Na-HCO₃-Cl > Ca-Mg-HCO₃-Cl > Na-Ca-Cl. Simple mineral dissolution or mixing processes is mainly responsible for the variation in the hydrochemistry of the groundwater of the study area.