Qualitative Evaluation of Groundwater Condition from Part of Gusau Metropolis Zamfara State, Northwestern Nigeria

Abstract

This research is aimed at assessing the impact of three major waste dumpsites situated within Gusau metropolis on shallow groundwater quality. Fifteen (15) representative groundwater samples were collected from hand-dug well taping shallow aquifers in different locations within the study area. The results revealed pH values that range between 7.26 to 8.12 with mean value of 7.50, whereas, recorded Total dissolve solid (TDS) range between 377 to 1393mg/L with average concentration of 751.27mg/L. The mean value recorded is > 500mg/L which is the limit set by WHO for drinking water. All the major and minor ions indicate moderate concentration in studied water samples compare to their various WHO, 2011 set up standard, except of sodium (Na+) which show elevated values above the threshold of permissible limit for domestic water use. Among the heavy metal, Cr+2 and Pb+2 revealed average concentrations higher than the permissible limit set by WHO for drinking water while Fe+2 and Cu+2 average concentrations were within the set up limit. The result of the correlation matrix shows that virtually all the major and minor ions are significantly correlated, suggesting similar source of their enrichment, which is not far from the mineral dissolution from the lithological framework due to chemical weathering. Similarly, they equally show significant relationship with total dissolve solids (TDS) and pH indicating their control efficiency of the groundwater within the study area. However, Fe+2 and Pb+2 are significantly correlated, this may not be unconnected with anthropogenic inputs, particularly from the waste dumpsites. The well-water samples in the study area are basically ‘Alkali waters’ that are predominantly SO4 2- and Cl-. The relative abundance of the three (3) dominant water types are as thus: Na-SO4> NaCa-SO4> Na-SO4-Cl. The relative abundance of cations is: Na++K+> Ca2+> Mg2+; while the relative abundance of the
anions is: SO4  2-> Cl-> HCO3-. The Gibb’s diagram highlights the supremacy of weathering of rocks, with a slight influence of evaporation-crystallization, in controlling the geochemistry of the well-water samples in the study area.