Das Projekt "Redox processes along gradients" wird vom Umweltbundesamt gefördert und von Universität Bayreuth, Lehrstuhl für Hydrologie, Limnologische Forschungsstation durchgeführt. The relevance of biogeochemical gradients for turnover of organic matter and contaminants is yet poorly understood. This study aims at the identification and quantification of the interaction of different redox processes along gradients. The interaction of iron-, and sulfate reduction and methanogenesis will be studied in controlled batch and column experiments. Factors constraining the accessibility and the energy yield from the use of these electron acceptors will be evaluated, such as passivation of iron oxides, re-oxidation of hydrogen sulfide on iron oxides. The impact of these constraints on the competitiveness of the particular process will then be described. Special focus will be put on the evolution of methanogenic conditions in systems formerly characterized by iron and sulfate reducing condition. As methanogenic conditions mostly evolve from micro-niches, methods to study the existence, evolution and stability of such micro-niches will be established. To this end, a combination of Gibbs free energy calculations, isotope fractionation and tracer measurements, and mass balances of metabolic intermediates (small pool sizes) and end products (large pool sizes) will be used. Measurements of these parameters on different scales using microelectrodes (mm scale), micro sampling devices for solutes and gases (cm scale) and mass flow balancing (column/reactor scale) will be compared to characterize unit volumes for organic matter degradation pathways and electron flow. Of particular interest will be the impact of redox active humic substances on the competitiveness of involved terminal electron accepting processes, either acting as electron shuttles or directly providing electron accepting capacity. This will be studied using fluorescence spectroscopy and parallel factor analysis (PARAFAC) of the gained spectra. We expect that the results will provide a basis for improving reactive transport models of anaerobic processes in aquifers and sediments.
Das Projekt "Methane Turnover in Alpine Glacier Forefields" wird vom Umweltbundesamt gefördert und von Eidgenössische Technische Hochschule Zürich, Institut für Biogeochemie und Schadstoffdynamik durchgeführt. Lead As atmospheric CH4 is an important contributor to climate change, understanding CH4 turnover is crucial for global climate modeling and potential mitigation strategies. In this project we will quantitatively assess CH4 turnover in alpine glacier forefields through specifically adapted methods. Hintergrund Methane (CH4) is among the most abundant greenhouse gases in the atmosphere with a significantly higher global-warming potential than CO2. The CH4 cycle is largely microbially mediated, with anaerobic methanogenic archaea responsible for CH4 production, and aerobic or anaerobic CH4 oxidizing bacteria (MOB) responsible for consumption. Little is known about CH4 turnover and MOB abundance and diversity in pioneer ecosystems such as glacier forefields. Here, a transition occurs from partially anaerobic, methanogenic subglacial sediments to largely aerobic, well-developed CH4 consuming soils in alpine meadows or forests. An initial field survey confirmed substantial CH4 production and consumption in several Swiss glacier forefields, but was limited in its scope by currently available methods to assess CH4 turnover. Ziel The project's overall goal is to quantitatively assess CH4 turnover in alpine glacier forefields through specifically adapted methods. The project will fill a gap in knowledge regarding CH4 turnover during the transformation of soils from the subglacial to the proglacial environment. This is especially valuable for evaluating potential feedback of deglaciation to climate change, and will lead to an improved understanding of colonization patterns of MOB. Bedeutung Methane is a potent greenhouse gas that contributes to global warming. To date, information on CH4 turnover in glacier forefields is extremely scarce. Thus, it will be important to rigorously assess the occurrence and magnitude of CH4 turnover in this environment. Effects of soil age as well as seasonal effects on CH4 turnover during the transition from an anaerobic, subglacial environment to postglacial, aerobic alpine meadows or forests are hitherto unexplored. However, changes in CH4 turnover during this transition may represent an important feedback to the climate system, in particular in light of glaciers predicted to continue their rapid retreat.
Das Projekt "Methansenkende Wirkung von Fettsaeuren beim Wiederkaeuer: Ursachen und Entwicklung" wird vom Umweltbundesamt gefördert und von Eidgenössische Technische Hochschule Zürich, Institut für Nutztierwissenschaften, Professur Tierernährung durchgeführt. Fettsaeuren haben eine betraechtliche und individuell unterschiedliche selektive Toxizitaet fuer methanogene Mikroben im Pansen. Das Ziel der vorliegenden Studie ist die Bestimmung der mikrobiellen Ursachen und der Entwicklung dieser methanunterdrueckenden Effekte. Dies wird einerseits in vitro mit dem Pansensimulationssystem Rusitec untersucht und andererseits mit Milchkuehen. Die Methanfreisetzung der Milchkuehe wird dabei in Respirationskammern erfasst, welche nach dem Prinzip der offenen Kalorimetrie arbeiten. Ein besonderes Augenmerk wird den Mikroben geschenkt, welche fuer die Methanfreisetzung verantwortlich sind, naemlich den Ciliaten und den Methanogenen. Das Projekt ist als Doktorarbeit ausgelegt und wird von Dipl.-Ing. agr. Frigga Dohme durchgefuehrt.