Fluoride and other inorganic constituents in groundwater of Guwahati, Assam, India

Abstract

Groundwater quality in Guwahati has been studied with special reference to the presence of fluoride. The Brahmaputra river in the north, hills to the east and south, and alluvial soil to the west surround the city. Fluoride, above the guideline values of WHO, has been found in groundwater of the eastern and southern plains of the city. The fluoride contents have positive correlation with Na + , K + , total alkalinity and depth of source, and negative correlation with Mg 2 + , Ca and total hardness. Negative correlation of fluoride with hardness and absence of any correlation with chloride indicate recharge of the aquifer by the Brahmaputra and/or rain. A few of the samples showed high nitrate and sulphate contents. The sources of fluoride and nitrate are suspected to be minerals from the Precambrian granite, which forms the basement of the city and also outcrops at several places in the city.