A review of methods used for equilibrium isotope fractionation investigations between dissolved inorganic carbon and CO2

Fractionation of stable carbon isotopes between individual dissolved inorganic carbon (DIC) species (H2CO3⁎, HCO3−, CO32 −) and gaseous CO2 (CO2(g)) at various temperatures has been studied by numerous authors. The maximum temperature, up to which experiments were conducted, was 286 °C, with most investigations only covering substantially lower temperature ranges. However, results of published data show discrepancies in their fractionation factors, especially at higher temperatures, where experimental data are scarce and results show significant scatter. The methodology and the experimental environment are considered the main reasons for the variable equilibrium fractionations. The largest discrepancies between published results were observed between CO32 − and CO2(g) and least between HCO3− and CO2(g). This review establishes an overview of the methods used to investigate the temperature-dependent isotope fractionation between the individual DIC species and CO2(g) and discusses the accompanying results.