Membrane inlet laser spectroscopy to measure H and O stable isotope compositions of soil and sediment pore water with high sample throughput

Erik J Oerter; Alexei Perelet; Eric Pardyjak; Gabriel Bowen

doi:10.1002/rcm.7768

Membrane inlet laser spectroscopy to measure H and O stable isotope compositions of soil and sediment pore water with high sample throughput

Rapid Commun Mass Spectrom. 2017 Jan 15;31(1):75-84. doi: 10.1002/rcm.7768.

Authors

Erik J Oerter^{1

2}, Alexei Perelet³, Eric Pardyjak^{3

2}, Gabriel Bowen^{1

2}

Affiliations

¹ Department of Geology and Geophysics, University of Utah, 115 South 1460 East, Salt Lake City, UT, 84112, USA.
² Global Change and Sustainability Center, University of Utah, 257 South 1400 East, Salt Lake City, UT, 84112, USA.
³ Department of Mechanical Engineering, University of Utah, 100 South 1495 East, Salt Lake City, UT, 84112, USA.

PMID: 27766702
DOI: 10.1002/rcm.7768

Abstract

Rationale: The fast and accurate measurement of H and O stable isotope compositions (δ² H and δ¹⁸ O values) of soil and sediment pore water remains an impediment to scaling-up the application of these isotopes in soil and vadose hydrology. Here we describe a method and its calibration to measuring soil and sediment pore water δ² H and δ¹⁸ O values using a water vapor-permeable probe coupled to an isotope ratio infrared spectroscopy analyzer.

Methods: We compare the water vapor probe method with a vapor direct equilibration method, and vacuum extraction with liquid water analysis. At a series of four study sites in a managed desert agroecosystem in the eastern Great Basin of North America, we use the water vapor probe to measure soil depth profiles of δ² H and δ¹⁸ O values.

Results: We demonstrate the accuracy of the method to be equivalent to direct headspace equilibration and vacuum extraction techniques, with increased ease of use in its application, and with analysis throughput rates greater than 7 h^-1 . The soil depth H and O stable isotope profiles show that soil properties such as contrasting soil texture and pedogenic soil horizons control the shape of the isotope profiles, which are reflective of local evaporation conditions within the soils.

Conclusions: We conclude that this water vapor probe method has potential to yield large numbers of H and O stable isotope analyses of soil and sediment waters within shorter timeframes and with increased ease than with currently existing methods. Copyright © 2016 John Wiley & Sons, Ltd.