Article ID Journal Published Year Pages File Type
4700303 Chemical Geology 2009 5 Pages PDF
Abstract

Oxygen isotope fractionation and equilibration kinetics between CO2 and H2O have been investigated at 313 K for salinities (S) ranging from 0 to 250 g L− 1. In this range of salinity, times needed to reach oxygen isotope equilibrium between CO2 and H2O increase from 4 h to 12 h. Isotopic exchanges are comparable for KCl and NaCl-like (sea salt) solutions and are described by first-order kinetic reactions with ln(k) = − 8.1485(± 0.0057) − 0.00474(± 3.87 × 10− 5)S. The oxygen isotope fractionation factor between CO2 and H2O increases with salinity for both sea salt and KCl solutions with concentrations ranging from 0 to 250 g L− 1 according to the following equation: 1000 ln(αCO2–H2O)sea salt = 37.02(± 5 × 10− 3) + 3.96 × 10− 3(± 1.1 × 10− 4)S − 6.38 × 10− 6(± 4.5 × 10− 7)S2 (R2 = 0.998). The oxygen isotope analysis of seawater samples with a salinity of 35 g L− 1 requires minor corrections of − 0.15‰ (V–SMOW). However, oxygen isotope ratios are overestimated by 0.4‰ to 0.6‰ in the case of highly saline natural waters (100 < S < 250 g L− 1). Corrections of the oxygen isotope ratios due to changes in the salinity-dependent fractionation factors between CO2 and H2O must be taken into account during the study of waters sampled from salt marshes, hypersaline lakes and lagoons, or hydrothermal brines.

Related Topics
Physical Sciences and Engineering Earth and Planetary Sciences Geochemistry and Petrology
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