期刊
MARINE CHEMISTRY
卷 190, 期 -, 页码 28-34出版社
ELSEVIER
DOI: 10.1016/j.marchem.2016.12.008
关键词
U-236; U-236/U-238 atom ratios; Coral core; Northwest Pacific Ocean; AMS
资金
- Hiroshima Earth Environment Information Center
- Ministry of Education, Culture, Sports, Science and Technology, MEXT, Japan [24110008]
- National Institute for Environmental Studies Tsukuba
- Grants-in-Aid for Scientific Research [16K13911, 15H02340, 15H02149, 17K05685] Funding Source: KAKEN
The temporal distribution of U-236 in the Northwest Pacific Ocean was reconstructed through measurements of the annual changes in U-236/U-238 atom ratios in a coral core collected from Kume Island located within the Kuroshio Current region. In total, 74 years (1940-2014) of temporal trend of U-236/U-238 atom ratios were reconstructed using Accelerator Mass Spectrometry (AMS). The annually resolved U-236/U-238 ratios showed a strong increase from 1952, and two prominent peaks were found in the annual bands for 1954 (11.0 +/- 1.2 x 10(-9)) and 1958 (8.55 +/- 1.17 x 10(-9)); also an enhanced peak was observed for the band of 1963 (3.51 +/- 0.20 x 10(-9)). These peaks coincided with the occurrence of large nuclear tests in the Pacific Proving Grounds and/or the highest global fallout rate, suggesting a clear influence of these nuclear events on U-236/U-238 atom ratios. Furthermore, the coral results showed some disagreement with the annual changes for U-236 in East Asian corals collected at the entrance to the Sea of Japan. Based on these results, the mixing ratios of the surface seawater currents in the Northwest Pacific Ocean have been estimated. (C) 2017 Elsevier B.V. All rights reserved.
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