A Factor Model to Explain the Hydrochemistry and Causes of Fluoride Enrichment in Groundwater from the Middle Voltaian Sedimentary Aquifers in the Northern Region, Ghana

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Groundwater plays a pivotal role in the domestic water delivery system in Northern Ghana. The resource has sometimes been rendered unsuitable for use due to contamination from various sources. In this study, a factor model was developed to determine the major hydrochemical processes that control the variations in the concentrations of fluoride and other ions in the groundwater delivered by the Middle Voltaian aquifers in Savelugu and surrounding areas in the Northern Region of Ghana. This study finds that four major processes control the hydrochemistry of groundwater resources in the area: dissolution of soluble salts in the aquifers, the oxidation of organic carbon by nitrate, silicate mineral weathering and the dissolution of sulfate minerals in the aquifers. The present study finds that fluoride enrichment is related to the weathering of silicate minerals. A linear interpolation map, showing the distribution of fluoride concentrations in the groundwater system has been produced. Two major groundwater types have been distinguished in this study: fresh Na-KHCO 3 groundwater types, and Na-Cl groundwater types. The Na-Cl water types are associated with areas of high influence of chloride rich sedimentary beds, where groundwater has extremely high salinity and is therefore not suitable for domestic and several other uses. Mineral stability diagrams suggest that the most stable silicate mineral phase is montmorillonite which indicates restricted groundwater flow owing to the limited interconnectivity of the fracture systems that control the hydrogeological properties of the aquifers in the area.

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