MRI: Acquisition of A New Accelerator Mass Spectrometer for Radiocarbon Measurements

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This project will provide funds for new instrumentation at the National Ocean Sciences Accelerator Mass Spectrometry facility (NOSAMS) at Woods Hole Oceanographic Institution. The facility is dedicated to high quality measurements of the rare isotope of carbon (carbon-14 or radiocarbon), which can be used to date carbon samples in the ocean and the environment, and to understand the natural carbon cycle. The mission of the facility is to provide high quality radiocarbon measurements and expertise to the Ocean and Earth science communities and to develop innovative new radiocarbon methods. The researchers will purchase a new state-of-the-art Accelerator Mass Spectrometer (AMS) system designed specifically for radiocarbon measurements in different sample types, including new interfaces for direct measurements of carbon dioxide gas. Acquisition of the new instrumentation will result in improvements to the nature, quality, and quantity of analytical services provided, and will facilitate the development of new techniques and services. Access to state-of-the-art equipment and techniques is crucial to providing high quality training and research tools for the next generation of U.S. based earth and ocean scientists.The researchers will use the funds to purchase a new system, and to compare commercially available AMS systems to the Mini Carbon Dating System (MICADAS), manufactured by Ionplus, which was identified as the most appropriate based on documented precision and the availability of versatile gas interfaces. The newly developed gas interfaces will diminish the need to make elemental carbon (graphite) for some sample types. The new system will improve NOSAMS service to the science community by offering improved precision, greater efficiency, and new cutting edge measurement options. In particular, the newest AMS systems have the capability to produce high precision measurements on graphite and on relatively small amounts of carbon dioxide, using the hybrid gas ion source. Elimination of the graphitization process offers the potential of reduced blank and per-sample measurement cost. Applications that would be enhanced by the new AMS system include: measurements of carbon-14 in seawater, in carbonates, and in complex organic mixtures using Compound Specific Radiocarbon methods and Ramped Pyrolysis and Oxidation. One core NOSAMS mission is to produce high quality sea water measurements to constrain the time scales of ocean mixing and ventilation. Repeat hydrographic studies have revealed measurable changes in ocean mixing and ventilation on decadal time scales, including warming of the deep ocean, which has important implications for ocean circulation, sea level, and climate. Radiocarbon can provide independent time scales, but requires the highest precision to resolve small variations, and high through-put to allow spatial resolution. Carbonate measurement capabilities will be enhanced by higher precision (using graphite) and lower-cost high-sampling-density measurements (using gas ion source interface at moderate precision). Compound specific radiocarbon analysis and Ramped Pyrolysis and Oxidation can be used to determine the relative age and provenance of individual compounds and compound classes in complex organic mixtures.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.