ISOTOPE HYDROGEOCHEMICAL INVESTIGATIONON THE OCCURRENCE OF FLUORIDE INGROUNDWATERS OF ALAPPUZHA DISTRICT,KERALA, INDIA

摘要

Environmental isotopes ( 2H, 18O, 3H, 13C and 14C) along with hydrochemical andhydrogeological information were used to understand the source and mechanism offl uoride release into the groundwaters of a heavily exploited multilayered regionalaquifer system in Alappuzha district, Kerala, India. The results of the study showthat the shallow Quaternary aquifers are uncontaminated whereas the deep Tertiaryaquifers are contaminated with fl uoride (up to 2.6 mg/L). The observed positivecorrelation of F - with pH, alkalinity, Na+ and 13C and negative correlation with Ca2+along the fl ow path point out that the leaching of fl uoride bearing aquifer material isresponsible for the release of fl uoride into the groundwater. F – versus 18O plot alsoconfi rms the leaching process. The rate of fl uoride release is different in various fl owpaths and it depends upon the residence time of groundwater and length of the fl owpath. 2H, 18O, 3H and 14C data indicate that the contaminated groundwater is veryold with 14C ages varying from 15 to 30 ka B.P. in the down gradient and probablyrecharged during an arid climate in the past.