Fluoride incidence in groundwater in an area of Peninsular India

Groundwater samples were collected from Anantapur District, Andhra Pradesh, India. The district is mainly underlain by Peninsular Gneisses of Archaean age. The samples were analysed for fluoride (F-) along with other chemical parameters. The results suggest that the main sources of F- in groundwater in the district are the country rocks, in which fluorine is strongly absorbed in soils consisting of clay minerals. A strong positive correlation between F- and lithogenic sodium reflects weathering activity. This is responsible for the leaching of F-, which is also caused by the semi-arid climate and intensive irrigation in the area. An alkaline environment of circulating water in the investigated area mainly facilitates leaching of F- from the soils, contributing to high F--containing groundwater. A longer residence time of water in the aquifer zone, caused by a high rate of evapotranspiration and a weathered zone of low hydraulic conductivity, which promotes the dissolution of fluorine-bearing minerals, is another factor that further increases the F- content in groundwater. Suggestions are made to improve groundwater quality and, thus, the health status of the population.