This Major Research Instrumentation grant supports acquisition of a high-sensitivity stable isotope ratio mass spectrometer (Delta V plus with Conflo IV universal interface) at the Stroud Water Research Center (SWRC). The new instrumentation will provide enhanced capabilities and greater sensitivity analyses than currently available at the SWRC. The new IRMS system will be put to use in several funded projects with the overall goal of exploiting hydrogen, nitrogen, oxygen and carbon stable isotopes to track organic matter cycling in soils and stream environments. Natural abundance measurements and heavy isotope tracers will be used to track energy and carbon flow in stream ecosystems. Data from these measurements will support the development of dynamic mathematical models describing the movement, quantity and quality and transformation of nutrients through surface earth hydrological processes. Studies in collaboration with regional scientists engaged in NSF-funded Long Term Research in Environmental Biology (LTREB) sites and a regional Critical Zone Observatory (CZO) will be facilitated.
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This Major Research Instrumentation grant supported the acquisition of a high-sensitivity Isotope Ratio Mass Spectrometer (IRMS) at the Stroud Water Research Center (SWRC) to apply of new analytical methods in novel ways to earth surface and environmental science questions. Natural abundance measurements and stable isotope tracers are valuable tools used to track energy and carbon flow in stream ecosystems. Data from these measurements will support the development of dynamic mathematical models describing the movement, quantity and quality and transformation of nutrients through surface earth hydrological processes. In year 1 of this project, we worked with the IRMS manufacturer (Thermo Scientific) to design a 12-cup custom collector array, ordered the customized Delta V Plus IRMS and their new Conflo IV Universal interface, and remodeled and reconfigured the isotope laboratory to accommodate the new instruments. In year 2 we focused on beginning use of our newly installed instruments by: finalizing laboratory configurations, testing the new instrument with each of our front-end peripherals, and re-implementing each of our primary applications in with the newly configured lab and instruments. In year 3 we focused on method optimization and development for our new IRMS instrument while simultaneously transitioning back into high levels of sample throughput for our routine analyses on both our new and old IRMS instruments. Our method development focused on two new applications: (1) Dissolved organic carbon (DOC) from streams with very low concentrations (<1mg/L); and (2) Dissolved gases N2, O2, Ar and CO2, and high precision N2/Ar ratios, on single water samples in order to assess stream community production, respiration and denitrification. We improved the sensitivity of our DOC analyses by a factor of 20x. A sensitivity gain of 4x was gained with the new Delta V Plus IRMS, which has a more sensitive design. We gained an additional 5x gain in sensitivity by developing a custom cryo-trapping system to focus the broad CO2 peak from the DOC analyzer and peripheral into narrower and taller (5x) peaks prior to analysis by the IRMS. This significant performance improvement now allows automated stable isotope analysis of DOC from all low carbon environments, such as deep groundwaters and streams draining volcanic soils. We further developed our all-dissolved-gases method on the new Delta V Plus IRMS. We had previously developed the automated sample preparation instrument methods to measure CO2, O2, N2, Ar all on a single sample by modifying our GasBench II interface, but we were not able to simultaneously measure all their isotopes due to limitations of our instrument. Our new 12-collector IRMS had allowed us to pursue the full implementation of this method. The new IRMS system has been put to use in several funded projects with the overall goal of exploiting hydrogen, nitrogen, oxygen and carbon stable isotopes to track organic matter cycling in soils and stream environments. These projects include collaborations with scientists in the region on field sites developed by our NSF-funded Long Term Research in Environmental Biology (LTREB) and the Christina River Basin Critical Zone Observatory (CRB-CZO) projects.
