Operation of a National Ocean Sciences Accelerator Mass Spectrometry Facility at the Woods Hole Oceanographic Institution

Woods Hole Oceanographic Institution, Woods Hole MA

Investigators

Abstract

0228996 Hayes This 5-year cooperative agreement award to Woods Hole Oceanographic Institution in Massachusetts provides support for continued operation of the National Ocean Sciences Accelerator Mass Spectrometry (NOSAMS) facility. NOSAMS provides analyses of 14C at natural abundance levels. Such data are essential for radiocarbon dating, for studies of dynamic geophysical processes in earth's surface environment (for example, the circulation of the oceans), and for studies of the biogeochemical cycling of carbon. The facility accepts samples from all qualified laboratories and charges fees that vary according to the difficulty of the analysis and the nature of the project. During the four years ending 31 March 2002, the facility completed more than 18,000 analyses and recovered more than 56% of its operating costs from user fees. The facility provides both sample-preparation services and quantitative analyses of 14C. Graphite suitable for mass spectrometric analysis is prepared from samples of carbonate minerals, organic carbon, or inorganic carbon dissolved in water. Quantitative analyses are obtained using a mass spectrometer system for which the minimum sample size is 25 micrograms of C. Attainment of full precision (+/- 3.5 parts per thousand for the 14C /12C ratio) requires a sample size of at least 500 micrograms C. During the five-year period of the cooperative agreement, the capabilities of the facility will be enhanced. A gas-accepting ion source will be installed in order to allow analyses of 14C in a continuously flowing stream of carrier gas. This development will provide tens of low-precision analyses per hour for samples as small as 0.1 micrograms C and will be uniquely applicable to surveys and to monitoring of highly diluted radiocarbon tracers. Procedures for treatment of sediments and other samples containing organic carbon will be automated. The capacity of the sample-preparation laboratory to respond to surges of sample submissions and thus to minimize increases in turnaround time will be increased. Components of the mass spectrometer itself will be rebuilt in order to improve and to stabilize performance. As these improvements are made, the facility will continue to serve the ocean sciences research community, promptly providing radiocarbon analyses as needed each year. ***