title: Membrane inlet laser spectroscopy to measure H and O stable isotope compositions of soil and sediment pore water with high sample throughput.
abstract: BACKGROUND
  The fast and accurate measurement of H and O stable isotope compositions (δ2H and δ18O 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 δ2H and δ18O 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 δ2H and δ18O 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.
authors.affiliation: Department of Geology and Geophysics, University of Utah, 115 South 1460 East, Salt Lake City, UT, 84112, USA.|Global Change and Sustainability Center, University of Utah, 257 South 1400 East, Salt Lake City, UT, 84112, USA.
authors.forename: Erik J
authors.identifier: http://orcid.org/0000-0001-8816-1754
authors.initials: EJ
authors.lastname: Oerter
authors.affiliation: Department of Mechanical Engineering, University of Utah, 100 South 1495 East, Salt Lake City, UT, 84112, USA.
authors.forename: Alexei
authors.initials: A
authors.lastname: Perelet
authors.affiliation: Department of Mechanical Engineering, University of Utah, 100 South 1495 East, Salt Lake City, UT, 84112, USA.|Global Change and Sustainability Center, University of Utah, 257 South 1400 East, Salt Lake City, UT, 84112, USA.
authors.forename: Eric
authors.initials: E
authors.lastname: Pardyjak
authors.affiliation: Department of Geology and Geophysics, University of Utah, 115 South 1460 East, Salt Lake City, UT, 84112, USA.|Global Change and Sustainability Center, University of Utah, 257 South 1400 East, Salt Lake City, UT, 84112, USA.
authors.forename: Gabriel
authors.initials: G
authors.lastname: Bowen