A GC-MS/GC-IRMS for the molecular-level analyses of organic matter and the isotopic characterization of inorganic and organic compounds in aquatic and terrestrial ecosystems

Stable isotopes represent a valuable means to constrain specific biogeochemical processes in natural environments. The main objective of the project is to develop an Environmental Laboratory for Aquatic and Terrestrial Biogeochemistry, which will support research that will make use of molecular-level characterization and (compound-specific) isotope ratio determination methods to assess a wide spectrum of biogeochemical transformations in the natural environment and in the laboratory, and to study sources and the fate of organic compounds in marine, freshwater, and soil systems.The requested infrastructure includes the following instruments:

•    Gas Chromatograph coupled to a quadrupole mass spectrometer (MS) with two detectors (FID and MS) for organic compound recognition. Through the GC-C III interface, the GC will be coupled to the IRMS for isotope measurements on single target molecules.
•    Gas source stable isotope ratio mass spectrometer (IRMS), Gasbench-II Interface, accessories for 18O and H/D analysis in GC eluates, and autosampler for high-precision isotope ratio determination.

One of the major goals of the projects that make use of the new instrumental capacities is to understand the interactions of the bio- with the geo- and atmosphere with respect to the transport of organic materials and the transformation of   inorganic and organic compounds by plants and microorganisms, which is of ultimate importance for the reduction of green house gases and the cycling of elements in aquatic and terrestrial ecosystems. A prime objective will be to use stable isotope measurements to constrain specific biogeochemical and metabolic processes, as well as sources, transport and degradation of organic matter in aquatic and terrestrial environments, and, in turn, to use these constraints to obtain improved estimates on global and regional C and N fluxes, in modern environments as well as in the past.

Planned research themes include: I) using lipid biomarker approaches to study microbial communities in various marine and freshwater environments, II) characterizing organic matter components in lacustrine sediments as well as in soils, and identifying the mechanisms responsible for the longer-term sequestration and degradation of organic C and the emission of greenhouse gases, III) understanding the metabolic pathways of C and N during the symbiosis between microorganisms and plants, and IV) generating data sets for the isotopic composition of nitrate and other N species in various aquatic systems in order to characterize the controls on isotope fractionation of specific N cycle reactions. The spectrum of investigated ecosystems will range from Swiss soil and groundwater systems and small lakes to hydrothermal vent systems in the deep ocean, and the spatial scale of the planned research extends from enzyme biogeochemistry to ocean-scale circulation.

Planned projects address a diverse range of topics, yet they share the common goal of using biomarker and isotope analyses to address important and innovative questions regarding a) the cycling of C and N in terrestrial and aquatic systems on the organism-level, regional and global scales, b) the role of microbes for greenhouse gas emissions and c) the use of C and N stable isotope ratios as environmental tracers, in modern environments and in the past.