1. Department of Environmental Chemistry, Swiss Federal Institute of Aquatic Science and Technology─Eawag, Überlandstrasse 133, 8600 Dübendorf, Switzerland
2. Institute of Biogeochemistry and Pollutant Dynamics, ETH Zürich, Universitätstrasse 16, 8092 Zürich, Switzerland
3. Department of Aquatic Ecology and Water Quality Management, Wageningen University, P.O. Box 47, 6700 Wageningen, The Netherlands