1. Environmental Biophysical Chemistry, GR-SLV-IIE-ENAC, Ecole Polytechnique Fédérale de Lausanne (EPFL), Station 2, CH-1015 Lausanne, Switzerland, IBB/CBME, Department of Physical Chemistry and Colloid Science, Wageningen University and Research Centre, Dreijenplein 6, 6703 HB Wageningen, The Netherlands, and Department of Chemistry, University of Lleida, Avda Rovira Roure 191, 25198 Lleida, Spain