The occurrence and behaviour of fluoride in the groundwater of the Lower Vamsadhara River basin, India

Abstract

Reports on the occurrence of fluoride in natural water resources and the associated health hazards due to human consumption have been made from many parts of India during the last decade. With the objective of organizing a systematic scientific programme to understand the behaviour of fluoride in natural water resources in relation to the local hydrogeological and climatic conditions and agricultural use, a typical area constituting the lower Vamsadhara River basin was chosen for a detailed study. High fluoride concentrations in the groundwater reaching a maximum of 3.4 mg 1⁻¹ were observed to be associated with weathered formations of pyroxene amphibolites and pegmatites. The groundwater in the clayey soils contained much less fluoride as compared to the sandy soils. The complex depositional pattern of these sandy and clayey soils plays an important role in the uneven spatial distribution of fluoride in the groundwater. The contribution of fluoride from geological formations is far greater than that from agriculture: the maximum yield of fluoride by superphosphate fertilizer to irrigation water is observed to be 0.34 mg 1⁻¹. The fluoride concentration is expected to be increased in the future as the groundwater is subsaturated with respect to fluorite. An inverse relationship between F and Ca and positive relationships of F with Na, HCO₃, PO₄ and electrical conductivity were observed. Best relationships were obtained in the fluoride range of 1.0–3.4 mg 1⁻¹.