Institute of Environmental Geosciences, University of Basel, Bernoullistrasse 30, 4056 Basel, Switzerland

Institute of Ecology, University of Innsbruck, Sternwartestrasse 15, 6020 Innsbruck, Austria

Agroscope Reckenholz-Taenikon Research Station ART, Air pollution/Climate group, Reckenholzstrasse 191, 8046 Zurich, Switzerland

Institute of Plant Science, ETH Zurich, Universitaetsstrasse 2, 8092 Zurich, Switzerland

Institute of Ecology, University of Innsbruck, Sternwartestrasse 15, 6020 Innsbruck, Austria

Desert Research Institute, Division of Atmospheric Sciences, 2215 Raggio Parkway, Reno, NV 89512, USA

Institute of Environmental Geosciences, University of Basel, Bernoullistrasse 30, 4056 Basel, Switzerland