EAGER: Measurement of the Oxygen and Hydrogen Isotope Composition of Evaporating Water Using a Novel Cavity Ring-Down Technique

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The Principal Investigator (PI) plans to: (1) To refine and apply a new experimental technique to measurements of the kinetic isotopic fractionation of water associated with evaporation and condensation; and (2) to calibrate a said instrument with traditional mass spectrometry techniques focusing on relatively low water vapor concentrations (6000 ppmv) and on the deuterium excess of water vapor. It is expected that both of these goals will be beneficial to a wide range of scientists with interest in hydrology and atmospheric climate dynamics. The PI has developed a novel experimental technique for measuring the fractionation associated with evaporation and condensation that takes advantage of the rapid analytical capabilities of newly commercially available laser-based cavity ring-down spectrometers (CRDS). The new technique has several advantages over traditional mass spectrometry as simultaneous, real-time measurements of water vapor concentration and water vapor hydrogen and oxygen isotopic ratios may be made. Preliminary evaporation data corroborate the published equilibrium fractionations (100% relative humidity), suggesting that this approach may provide a new way to advance understanding of isotopic fractionation during disequilibrium evaporation and condensation. This work is exploratory in nature and the approach largely untested and thus qualifies for an EAGER. This work will provide a foundation for future research in a wide range of hydrologic and atmospheric research. The research methodologies developed in this project will be published in peer-reviewed journals and presented at national conferences, and the project will partially fund the Ph.D. research of a female Ph.D. student.