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. Chem ical 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 HCO3
-. Basement rocks including horn blende 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.
