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Atmospheric Measurement Techniques An interactive open-access journal of the European Geosciences Union
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Articles | Volume 7, issue 8
Atmos. Meas. Tech., 7, 2421–2435, 2014
Atmos. Meas. Tech., 7, 2421–2435, 2014

Research article 08 Aug 2014

Research article | 08 Aug 2014

Calibrated high-precision 17O-excess measurements using cavity ring-down spectroscopy with laser-current-tuned cavity resonance

E. J. Steig1,2, V. Gkinis2,3, A. J. Schauer1, S. W. Schoenemann1, K. Samek1, J. Hoffnagle4, K. J. Dennis4, and S. M. Tan4 E. J. Steig et al.
  • 1Δ*IsoLab, Earth & Space Sciences, and Quaternary Research Center, University of Washington, Seattle, WA 98195, USA
  • 2Centre for Ice and Climate, Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen, Denmark
  • 3Institute of Arctic and Alpine Research, University of Colorado, Boulder, CO 80309, USA
  • 4Picarro Inc. Santa Clara, CA 95054, USA

Abstract. High-precision analysis of the 17O / 16O isotope ratio in water and water vapor is of interest in hydrological, paleoclimate, and atmospheric science applications. Of specific interest is the parameter 17O excess (Δ17O), a measure of the deviation from a~linear relationship between 17O / 16O and 18O / 16O ratios. Conventional analyses of Δ17O of water are obtained by fluorination of H2O to O2 that is analyzed by dual-inlet isotope ratio mass spectrometry (IRMS). We describe a new laser spectroscopy instrument for high-precision Δ17O measurements. The new instrument uses cavity ring-down spectroscopy (CRDS) with laser-current-tuned cavity resonance to achieve reduced measurement drift compared with previous-generation instruments. Liquid water and water-vapor samples can be analyzed with a better than 8 per meg precision for Δ17O using integration times of less than 30 min. Calibration with respect to accepted water standards demonstrates that both the precision and the accuracy of Δ17O are competitive with conventional IRMS methods. The new instrument also achieves simultaneous analysis of δ18O, Δ17O and δD with precision of < 0.03‰, < 0.02 and < 0.2‰, respectively, based on repeated calibrated measurements.

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