Environmental isotope (18O, 2H, 3H, 13C, 34S and 87Sr/86Sr) studies on CO₂-rich waters in the Kangwon Province were carried out to elucidate the origin, residence time, water-rock interaction and mixing process of their δ18O and δD data indicate that CO₂-rich waters were derived from the local meteoric water. It also shows that each type of CO₂-rich water has distinct isotopic composition and Na-HCO₃type water (-10.8 to -12.1‰, δ18O) is lighter than other type waters. These depleted isotopic values supposedly indicate that, considering the altitude effect of isotope in Korea, the recharge area of Na-HCO₃type water can be estimated to be relatively higher in elevation than those of Ca-HCO₃type water, confirming a long residence time and the possibility of a CO₂inflow into the auifer at great depth. These isotope data also show that the Ca-HCO₃type water has undergone mixing process with surface water during ascanding at depth, whereas Na-HCO₃type water was less mixed with surface waters. The carbon isotope data (-8.8 to +0.8‰, δ13C) indicate that dissolved carbon in the CO₂-rich waters was possibly derived from deep seated CO₂gas. The high δ34S) values (up to 38.1‰) of dissolved sulftes suggest that sulfate reduction by microbial activity had occurred at depth. Strontium isotopic data (87Sr/86Sr) of CO₂-rich waters indicates that the chemistry of the CO₂-rich waters is determined by water-rock (granite) interaction.
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