^<18>O/^<16>O Activity Ratio at 0℃ of Salt Water of Don Juan Pond and Lake Bonney, Dry Valleys, Antarctica

Abstract

The oxygen isotope ratio determined from CO_2 equilibrated isotopically with the water sample provides the oxygen isotope activity ratio of the water sample. The solution of certain salts causes the oxygen isotope activity ratio to differ from the concentration ratio of the water sample. These effects are expected to increase with decreasing temperature. The oxygen isotope ratio is usually determined from CO_2 equilibrated at 25 ℃ with water. The salt water in the Dry Valleys, Antarctica is not assumed to register the oxygen isotope ratio determined at 25 ℃. So, the oxygen isotope ratio of the salt water was determined at 0℃. The CO_2-H_2O isotope fractionation factor determined at 0℃ is 1.0459. Using this value, the oxygen isotope ratio of salt water of Don Juan Pond and Lake Bonney at 0℃ was determined. The oxygen isotope ratio at 0℃ is fairly different from that at 25℃ and the difference varies greatly according to the kind of salt.