Simultaneous measurement of δ2H, δ17O, and δ18O in H2O using a commercial cavity ringdown spectrometer

• 17O/16O ratio determination method using existing commercial spectrometer is detailed.
• Method is verified vs. isotope ratio mass spectrometry.
• Method is used to measure the isotopic fractionation (δ17O and δ18O) associated with the evaporation of water.
• Method is also used to measure anomalous (Δ17O) content of laboratory samples and to simulate reservoir mixing.
• Ease of implementation should enable new applications in a variety of fields in chemistry, geochemistry, and astrochemistry.

We demonstrate that a commercial instrument that provides measurements of 18O/16O and D/H ratios in water samples can be modified to also provide measurements of 17O/16O. This additional capability and associated precision allows for the discernment between conventional mass-dependent processes, such as isotope exchange and evaporation and mass-independent processes that arise from non-equilibrium chemical and photochemical processes. We demonstrate this resolution by performing a series of experiments including evaporation and reservoir-mixing with 17O enriched water samples followed by evaporation. The ability to simultaneously measure 16O, 17O, and 18O abundances in water samples using the procedures described here should help to facilitate multi-isotopic studies of water (and other compounds) in astrochemical, geochemical, and biological studies.

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