SMALL-MASS GRAPHITE PREPARATION FOR AMS C-14 MEASUREMENTS PERFORMED AT GIGCAS, CHINA

The sealed tube Zn reduction method has been applied for small-mass samples ranging from 15 to 100 mu g carbon preparation for accelerator mass spectrometry (AMS) radiocarbon (C-14) measurements at the AMS-C-14 Preparation Lab in Guangzhou Institute of Geochemistry, Chinese Academy of Sciences (GIGCAS). The volume of the sealed reactor tube is reduced to similar to 0.75 cm(3) in order to increase the yield of graphite. Graphite targets are measured at the Keck Carbon Cycle AMS Facility at the University of California, Irvine (KCCAMS). The targets generate a maximum C-12(+1) current of about 0.5 mu A per 1 mu g C. The modern-carbon background is estimated to be 0.25-0.60 mu g C, and dead-carbon background to be similar to 0.3-0.9 mu g C. Both modern-carbon background and dead-carbon background are size dependent, so the results can be corrected. The precision of the small-mass modern carbon standard samples is +/- 15-25 parts per thousand for the size of similar to 15-20 mu g C, +/- 5-10 parts per thousand for similar to 20-50 mu g C, and +/- 3-10 parts per thousand for 50-100 mu g C. Further reduction of dead-carbon and modern-carbon contamination is needed in preparation of small-mass samples at GIGCAS.Chinese Academy of Sciences Equipment Function Development and Technological Innovation [YZ2011046]; National Natural Science Foundation [41403098]SCI(E)ARTICLE3705-7115