Lithologic Influence on the Hydrogeochemical Characteristics of Groundwater in Zango, North-West Nigeria.

Abstract

The influence of bedrock on the quality of groundwater in Zango, North-west Nigeria was evaluated in this study. Water quality parameters such as pH, electrical conductivity, temperature, total dissolved solids, nitrate, sulphate, chloride, phosphate, bicarbonate, fluoride, calcium, magnesium, potassium, sodium, iron, manganese, lead, zinc, cadmium, chromium and copper were used in assessing the impact of bedrock geochemistry on groundwater quality. Zango Local Government Area of Katsina State is underlain by Gundumi Formation, Chad Formation, Basement Complex Rocks and Younger Granites suites. The groundwater in the area shows characteristics signatures in major and elemental composition. Based on these signatures, the geochemical evolution of groundwater from the four different aquifer-types is quantitatively described by the interaction of the groundwater with the rock-forming minerals released into the groundwater system through natural processes of weathering and dissolution in the flow path. High concentration of fluoride, major and trace elements were observed in areas outcropped by Basement Complex Rocks and Younger Granites suites. The observed concentration ranges of fluoride, major and trace elements is a reflection of the natural background concentration and a landmark in geochemical characterization of groundwater from different aquiferous units. The result of the analysis is an indication that groundwater can be grossly contaminated by critical element. The concentration map developed for fluoride and other elements for the study was in agreement within the interpretation as the area dominated with sedimentary formations show low concentration while the region occupy by younger granites show high fluoride concentration. This implies that the granites in the area are composed of mineral containing these elements. Communities living in the granite/rhyolite dominated region where cases of fluorosis and heavy metal contamination have been observed should discontinue the use of groundwater from the area for domestic and drinking purposes. The Government should provide an alternative source of drinking water for the people.