1. Dep. of Water Resources and Drinking Water Eawag, Swiss Federal Institute of Aquatic Science and Technology Dübendorf 8600 Switzerland
2. International Services and Projects, Nagra Wettingen 5430 Switzerland
3. Dep. of Environmental System Sciences, Institute of Biogeochemistry and Pollutant Dynamics ETH Zürich Zürich 8092 Switzerland
4. Dep. of Earth Sciences, Institute of Geochemistry and Petrology ETH Zürich Zürich 8092 Switzerland