Factors controlling fluoride contents of groundwater in north-central and northwestern Sri Lanka |
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| Authors: | Sansfica M Young A Pitawala H Ishiga |
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| Institution: | (1) Department of Geosciences, Shimane University, Matsue 690-8504, Japan;(2) Department of Geology, University of Peradeniya, Peradeniya, Sri Lanka; |
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| 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 HCO3
−. 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. |
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