1. Environmental Chemistry and Ecotoxicology Laboratory, ENAC-ISTE-CECOTOX, Ecole Polytechnique Fédérale de Lausanne (EPFL), Station 2, 1015 Lausanne, Switzerland, and CABE (Analytical and Biophysical Environmental Chemistry), University of Geneva, 30, quai Ernest Ansermet, 1211 Geneva 4, Switzerland