Das Projekt "Mineralogische Umwandlung amorpher Eisensulfide in See-sedimente: ein potenzieller Stellvertreter-Indikator fuer den Klimawandel" wird vom Umweltbundesamt gefördert und von Eidgenössische Anstalt für Wasserversorgung, Abwasserreinigung und Gewässerschutz, Wasserforschungs-Institut, Forschungszentrum für Limnologie durchgeführt. Precipitation of iron sulfides in sediments of deep lakes is linked to lake productivity and deep-water mixing. The concentration of iron sulfides in lake sediments may therefore contain information on the intensity of deep-water mixing, which is governed by climate variables such as wind speed and temperature. It is the goal of this project to make the geochemical information stored in iron sulfides in sediments more accessible for the reconstruction of past environmental conditions. Through an international collaboration with a group at the University of Grenoble the project will initiate a fundamental study of mineralogical transformations of iron sulfides in sediments. Synchrotron-based X-ray spectroscopy (EXAFS) offers new possibilities to obtain structural information from poorly cristallized samples. The method will be combined with in-situ analytical techniques to determine the sulfide record in different sedimentary environments (Lakes Baldegg and Lugano in Switzerland , Lake Baikal in Siberia and the Black Sea continental shelf). Leading Questions: The proposed study is focused on the following research goals: - To determine the local structure of amorphous iron sulfides derived from the reduction of different iron oxides and hydroxides by sulfide; - the apply this knowledge to the study of amorphous iron sulfides which prevail in lake sediments and to the crystal chemistry of intimately associated trace/minor elements; - to calibrate iron sulfides in sediments as a redox indicator of deep-water anoxia; - to apply this indicator for the reconstruction of aspects of continental climate variability in the last 10'000 years.