Triple oxygen isotope equilibrium fractionation between carbon dioxide and water

The growing number of recent high precision triple oxygen isotope data of water and atmospheric gases requires the reinvestigation of the major isotope fractionation processes between the hydro-, bio- and atmosphere. Here we present the experimental triple oxygen isotope fractionation factor between CO2 gas and water in the temperature range between 2 and 37 °C. We have determined the triple oxygen isotope fractionation factor, θ = ln17α/ln18α, for CO2–water equilibrium and found that θCO2–water = 0.522 ± 0.002 (t0.95 × SEM). No temperature dependence was resolved. Knowledge on the triple oxygen isotope equilibrium fractionation between CO2 and water is crucial for estimating the triple oxygen isotope composition of tropospheric CO2. Model predictions combined with high-precision Δ17O analysis of tropospheric CO2 might reveal new information on biosphere–atmosphere interactions or the influx of anomalous stratospheric CO2.