In a recent article published in the prestigious international journal Hydrology and Earth System Sciences, researchers from the Institute of Hydrodynamics of the Czech Academy of Sciences present a newly developed method for extracting soil water intended for the analysis of hydrogen and oxygen stable isotopes.
Kocum, J., Haidl, J., Gebouský, O., Falátková, K., Šípek, V., Šanda, M., Orlowski, N., Vlček, L. (2025). Technical note: A new laboratory approach to extract soil water for stable isotope analysis from large soil samples. Hydrology and Earth System Sciences. 29(13), 2863–2880.
The isotopic composition of these elements in soil water provides valuable insights into hydrological processes occurring within the soil profile—such as the origin of water (e.g., whether it derives from winter or summer precipitation) and its residence time in the soil. These insights are essential for studying interactions between soil water and vegetation, including how deep plant roots extend and what age and source of water plants rely on. However, to obtain accurate isotopic data, it is crucial to extract water from the soil without altering its natural isotopic composition.
The new method is based on the principle of complete evaporation and subsequent condensation of soil water in a closed-loop system, where flowing air serves as the carrier medium. Laboratory tests using various soil types and simulated moisture conditions demonstrated that the method achieves high extraction precision with minimal isotopic fractionation, even in technically challenging samples such as clay-rich soils with low water content. Compared to the most widely used technique today—cryogenic vacuum extraction—the new method produced comparable or even superior results. In some cases, its precision exceeded that of other available methods by an order of magnitude.
Unlike cryogenic vacuum extraction, which requires complex conditions including high vacuum, liquid nitrogen, and extreme temperatures (up to 300 °C), the newly designed system operates using commonly available equipment. Accurate results can be achieved using a standard temperature of 105 °C and tap water for cooling. The entire extraction process is free of chemicals and vacuum systems, significantly simplifying and enhancing the accessibility of the extraction.
