Factors controlling fluoride contents of groundwater in north-central and northwestern Sri Lanka

Abstract

Chemical characterization has been made of groundwater bodies at 294 locations in four village districts in north-central and northwestern Sri Lanka, with special focus on fluorine contamination. High fluoride contents in groundwater are becoming a major problem in the dry zone of Sri Lanka, and dental fluorosis and renal failures are widespread. Field measurements of temperature, pH, and electrical conductivity were made during sampling. Chemical analyses of the water samples were later made using atomic absorption spectroscopy, spectrophotometry, and titration. Fluoride concentrations in the study area vary from 0.01 to 4.34 mg/l, and depend on pH and the concentrations of Na, Ca, and HCO 3 -. Basement rocks including hornblende biotite gneiss, biotite gneiss, and granitic gneiss seem to have contributed to the anomalous concentrations of fluoride in the groundwater. Longer residence time in aquifers within fractured crystalline bedrocks may enhance fluoride levels in the groundwater in these areas. In addition, elevated fluoride concentrations in shallow groundwater in intensive agricultural areas appear to be related to the leaching of fluoride from soils due to successive irrigation.

Fluoride in Drinking Water: Health Effects and Remediation

“…The granitic rocks with average fluoride concentration of 1939 mg/kg in Nagar Parkar area, Pakistan, contain fluoride in kaolin deposits between 468 and 1722 mg/kg and secondary kaolin deposits have 270 mg/kg which are the source of fluoride up to 7.85 mg/L in groundwater in this area (Naseem et al 2010). Studies on fluoride in groundwater in Sri Lanka carried out by Dissanayake (1991) and Young et al (2010) shows that the condition has not changed even after about two decades with fluoride above 4 mg/L in groundwater. It was found that high fluoride areas lie within low plains.…”

Fluoride in the environment: sources, distribution and defluoridation

“…Studies on fluoride in groundwater in Sri Lanka carried out by Dissanayake (1991) and Young et al (2011) show Environ Chem Lett that the condition has not changed even after about two decades with fluoride above 4 mg/L in groundwater. It was found that high-fluoride areas lie within low plains.…”

Worldwide contamination of water by fluoride

“…Fluorine-bearing minerals are usually associated with acidic igneous rocks, mineralized veins and sedimentary formations (Edmunds and Smedley 2001). Its presence in felsic rocks is significantly greater than mafic and metasedimentary rocks (Young et al 2011).…”