The stable isotope signature of pore water provides an integral fingerprint of water origin, flow path, transport processes, and residence time and can thus serve as a powerful tracer of vadose zone hydrological processes. However, the full potential of stable isotopes to quantitatively characterize vadose zone water dynamics under varying conditions is yet unfolded. A major reason is that different sample procedures which have been developed in the last years are sampling water over a wide range of pore classes. Hence the results are difficult to interpret, especially because no one tested the relationship of isotopic signature and pore size until now. This knowledge can help to understand sampled isotopic water fractions and reveal if there are mobile and immobile fractions of water depending on the pore size. Furthermore, the results may improve nutrient and pollutant transport models.

The aim is to combine retention und pore stable isotopes data of soil samples to see the effect of pore size and equilibration time on the sampled isotopic water composition. This shall enhance both our physicochemical understanding of the processes involved and our ability to measure the stable isotope signature of soil water.

The thesis work will include planning, execution, and evaluation of suitable lab experiments to achieve the defined goal. This involves the application of pressure chambers to sample desorption solutions from soil samples labelled with water of different isotopic composition. The generated data will then be analyzed and interpreted to understand the observed behavior of pore water stable isotopic composition at different water tensions.

Markus Weiler und Natalie Orlowski

natalie.orlowski@hydrology.uni-freiburg.de; markus.weiler@hydrology.uni-freiburg.de Tel. +49 (0)761 / 203-3530

The work involves laboratory experiments and may involve collection of suitable soil material in the vicinity of Freiburg. Stable Isotope Hydrology; Soil Hydrology/Physics; Laboratory Experimentation; Data Analysis

Deutsch oder Englisch

Sprenger et al. (2015), Established methods and new opportunities for pore water stable isotope analysis