[1] Univ Innsbruck, Inst Ecol, A-6020 Innsbruck, Austria
[2] Paul Scherrer Inst, CH-5232 Villigen, Switzerland
[3] Univ Vienna, Fac Life Sci, Dept Chem Ecol & Ecosyst Res, A-1090 Vienna, Austria
[4] Forschungszentrum Karlsruhe, Inst Meteorol & Climate Res, Atmospher Environm Res Div IMK IFU, D-82467 Garmisch Partenkirchen, Germany