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

[0228996Hayes]这项授予马萨诸塞州伍兹霍尔海洋研究所的5年合作协议为国家海洋科学加速器质谱（NOSAMS）设施的持续运行提供了支持。NOSAMS提供自然丰度水平的14C分析。这些数据对于放射性碳定年、研究地球表面环境中的动态地球物理过程（例如海洋环流）以及研究碳的生物地球化学循环都是必不可少的。该设施接受来自所有合格实验室的样品，并根据分析的难度和项目的性质收取不同的费用。在截至2002年3月31日止的四年内，该设施完成了超过18,000次分析，并从用户费用中收回了超过56%的运营成本。该设施提供样品制备服务和14C的定量分析。适合质谱分析的石墨是由碳酸盐矿物，有机碳或溶解在水中的无机碳的样品制备的。使用质谱仪系统进行定量分析，最小样本量为25微克c。达到完全精度（14C /12C比例为+/- 3.5‰）需要至少500微克c的样本量。在合作协议的五年期间，该设施的能力将得到加强。将安装一个气体接受离子源，以便在连续流动的载气流中分析14C。这一发展将提供每小时数十次低精度分析，样品小至0.1微克C，将独特地适用于调查和监测高度稀释的放射性碳示踪剂。沉淀物和其他含有有机碳的样品的处理程序将实现自动化。样品制备实验室应对样品提交激增的能力将得到提高，从而最大限度地减少周转时间的增加。质谱仪本身的组件将被重建，以改善和稳定性能。随着这些改进的进行，该设施将继续为海洋科学研究界服务，每年根据需要及时提供放射性碳分析

0228996Hayes 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.***