Estimation of soil water evaporation from isotope hydrology methods in an agricultural field

These data are from this publication: Oerter, E. J., Perelet, A., Pardyjak, E., & Bowen, G. (2017). Membrane inlet laser spectroscopy to measure H and O stable isotope compositions of soil and sediment pore water with high sample throughput. Rapid Communications in Mass Spectrometry, 31(1), 75-84.

Abstract:
RATIONALE: 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 7h1. 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.

本研究数据源自于Oerter等（2017）的出版物：Oerter, E. J., Perelet, A., Pardyjak, E., & Bowen, G. (2017). 水膜进样激光光谱法在测量土壤和沉积物孔隙水中氢和氧稳定同位素组成（δ2H和δ18O值）中的应用：一种快速且精确的方法。快速通讯质谱分析，31(1)，75-84。

摘要：
研究缘起：土壤和沉积物孔隙水中氢和氧稳定同位素组成（δ2H和δ18O值）的快速与精确测量，对于扩大这些同位素在土壤和 vadose hydrology领域的应用仍存在一定的阻碍。本研究旨在描述一种测量土壤和沉积物孔隙水中δ2H和δ18O值的方法及其校准，该方法通过将水蒸气渗透探头与同位素比率红外光谱分析仪相结合实现。
方法：我们比较了水蒸气探头法与蒸汽直接平衡法、真空提取与液体水分析等方法。在美国大盆地东部一个管理型沙漠农业生态系统中的四个研究地点，我们使用水蒸气探头测量了土壤深度剖面中的δ2H和δ18O值。
结果：我们验证了该方法在准确性上与直接头空间平衡法和真空提取技术相当，其在应用上的便捷性有所提高，且分析通量率超过7小时。
土壤深度氢和氧稳定同位素剖面显示，土壤特性如对比土壤质地和成土土壤层次控制了同位素剖面的形状，这反映了土壤内部当地的蒸发条件。
结论：我们得出结论，该水蒸气探头法有望在更短的时间内，以比现有方法更简便的方式产生大量的土壤和沉积物水氢和氧稳定同位素分析数据。