Evaluating the geologic controls on Fluoride concentrations in Groundwater from Northern and Southern Ghana: A case study of Bongo and Afigya Sekyere Districts (original) (raw)

ABSTRACT Groundwater is the most appropriate portable and widely used source of drinking water for many rural communities in Ghana and its quality has special health significance and needs great attention of all concerned since it is the major alternate source of domestic, industrial and drinking water supply in Ghanaian communities. Fluoride is a common constituent of groundwater and its sources are connected to various types of rocks and to volcanic activity, Agricultural (use of phosphate fertilizers) and industrial activities. Fluoride contamination in drinking water is a public health problem in many areas around the world. Chronic ingestion of high doses has been linked to the development of dental fluorosis, abnormal thyroid function and other hormonal disturbances and in extreme cases, skeletal fluorosis. High doses have also been linked to cancer (Marshall, 1990) and (Ilamiiton, 1992). The study was carried out to evaluate the geologic controls on fluoride concentrations in groundwater from northern and southern Ghana on the West African Craton. Groundwater from active pumping wells and rock samples from outcrops were collected from various communities from northern and southern Ghana for fluoride and petrological (thin section) analysis. The fluoride concentration in groundwater in some communities of northern Ghana was recorded up to 4.0 mg/l and the overall water quality found was unsatisfactory with respect to fluoride for drinking purposes without any treatment and 0.8mg/l for the south which is considered to be good for drinking. The petro logical analysis indicates that the geological source of fluoride in groundwater is related to leaching of minerals from rocks thus metamorphic (gneissic) rocks and granitoids (Bongo granites) which are rich in mica, quartz and sericite as well as microcline. Among the fluoride-bearing minerals, only biotite was abundant in rock samples. There was a Positive correlation between fluoride concentration in the groundwater and the percentage of biotite composition in rock samples. Therefore, the high fluoride concentrations in the groundwater are more likely to result from the dissolution of biotite (K (Mg,Fe)3AlSi3O10(F,OH)2) which contain fluorine at the OH− sites of the octahedral sheet.