Acquisition of a Continuous Flow Combustion/Gas Chromatography Isotope Ratio Mass Spectrometer for Use in Biogeochemical Cycling and Atmospheric Chemistry Research

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Through this MRI grant, a stable isotope ratio mass spectrometer will be purchased, complete with front-end accessories including a preconcentrator/cryofocusing system, capillary gas chromatography system, and microcombustion furnace. Several faculty members in the UC Irvine Departments of Earth System Science (ESS) and Chemistry will use this system to make state-of-the-art isotopic measurements using gas chromatography on-line combustion and/or continuous flow mass spectrometry (GC/C/IRMMS). The currently available system has insufficient capacity for all ongoing projects. It is heavily used for isotope ratio measurements of methane, carbon monoxide, and carbon dioxide in air, soil, and freshwater, nitrous oxide in air, ocean carbon in dissolved and particulate organic carbon and inorganic carbon, coral, and soil organic and inorganic carbon and nitrogen. These measurements include the stable isotopes 13C/12C, D/H, 15N/l4N, and 180/160. In addition to increasing capacity, the new system will afford tremendous time savings associated with the GC/C/IRMMS technique because the need for laborious off-line preparation of samples will be eliminated.The extremely high sensitivity of IRMMS compared to IRMS will allow isotope studies of atmospheric chemistry and biogeochemical systems in which larger samples are difficult or impossible to acquire and/or species of interest are in very low abundance and impossible to measure with IRMS instrumentation. These studies include analyses of methane concentrations in soils and in the upper atmosphere, nitrous oxide in background air, halogenated hydrocarbons, and other non-methane hydrocarbons. Additional projects will include studies of kinetic isotope effects. Overall, stable isotope measurements are being used at UC Irvine to study an increasingly large number of complex processes. These include transfer rates among compartments of the biotic and abiotic environment including cycling of carbon, nitrogen, and other elements in various forms, atmospheric motion using trace gas species, global budgets of trace gases and their sources and sinks, and mechanisms of chemical and biochemical reactions.It is anticipated that a large number of principal investigators, but also graduate students, post-doctoral fellows, and other scientists will have access to this instrument and gain valuable research experience.