1. Environmental Geosciences, University of Basel, Bernoullistr. 30, CH-4056 Basel, Schwitzerland, BITÖK, University of Bayreuth, Dr.-Hans-Frisch-Str. 1-3, D-95440 Bayreuth, Germany, and UFZ-Umweltforschungszentrum Leipzig-Halle, Permoserstr. 15, 04318 Leipzig, Germany