Environmental tracers in groundwater hydrology

Contact:
Stephan Klump

The PhD project of Stephan Klump deals with the application of environmental tracer methods in groundwater hydrology. Atmospheric noble gases, CFCs and SF6 are used as environmental tracers in aquatic systems. These tracers are transported from the atmosphere into the groundwater by gas exchange between seepage water and soil air. The thesis focuses on the gas exchange in the unsaturated zone. In this context, the formation of excess air is of special interest. The dissolution of entrapped air bubbles in the quasi-saturated zone yields supersaturations of atmospheric gases as it can be observed in most groundwater samples. In order to reliably interpret tracer concentrations in groundwater, the use of models that describe the formation of excess air is necessary. The goal of the thesis is the verification of those models by application to natural aquifers and field scale experiments.

The thesis is part of a research project that deals with the combination of tracer methods and groundwater modeling, i.e. the use of tracers for the calibration or validation of groundwater models. Two aquifers in Grenchen (Canton Solothurn, Switzerland) and Baltenswil (Canton Zurich, Switzerland) are being investigated in the framework of this project.

The joint research project is carried out together with the Institute of Hydromechanics and Water Resources Management, ETH Zurich and the Physics Institute, Dept. of Climate and Environmental Physics, University of Bern.

In addition, a further focus of the PhD project is the work on case studies of the application of environmental tracer methods in groundwater hydrology.

Field experiments for studying the formation of excess air

In order to investigate the formation of excess air irrigation experiments were carried out in Grueningen (Switzerland) and Munich (Germany). Seepage water and groundwater samples were taken for the analysis of dissolved noble gases. Preliminary results show good agreement between experimental data and modeled noble gas concentrations.

Tracer study in Bangladesh

Groundwater contamination is a widespread problem in South and Southeast Asia. One of the most severely affected countries is Bangladesh. Groundwater dating by environmental tracers (noble gases, tritium) provides important information on groundwater dynamics and therefore, contributes to the understanding of arsenic mobilization.