2021年第82回応用物理学会秋季学術講演会

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CS コードシェアセッション » 【CS.1】 2.3 加速器質量分析・加速器ビーム分析、7.5 イオンビーム一般のコードシェアセッション

[10p-N402-1~10] CS.1 2.3 加速器質量分析・加速器ビーム分析、7.5 イオンビーム一般のコードシェアセッション

2021年9月10日(金) 13:00 〜 15:45 N402 (口頭)

笹 公和(筑波大)、藤田 奈津子(原子力機構)

15:15 〜 15:30

[10p-N402-9] Speciation Distribution of Iodine Isotopes (127I and 129I) in the North Pacific Ocean

〇(D)Yuanzhi Qi1、Hiroyuki Matsuzaki1 (1.The Univ. of Tokyo)

キーワード:iodine-129, speciation analysis, seawater

Bulk inorganic 127I and 129I, as well as for iodide and iodate of these two isotopes, were measured in seawater of different depth profiles in the north Pacific Ocean. The bulk inorganic 129I concentrations were 1.16 ~ 1.71 × 107 atoms L-1 in surface waters, and the vertical profiles almost have same trend, which is that the 129I concentration decrease with depth from the subsurface layer, among all study stations. The same trend indicates that atmospheric deposition may be the overwhelming 129I source in the North Pacific Ocean. Based on the measured bulk 129I concentrations, the 129I inventories in the upper layer (to the depth of 800 m) of North Pacific Ocean are 5.0 ~ 9.1 × 1011 atoms m−2. As the thermodynamically stable form of iodine in normal seawater, iodate is the predominant 127I species (35.8 ~ 63.7 µg/L, accounting for 72.6 ~ 97.5% of bulk 127I) in the North Pacific Ocean. However, the 129I/127I ratio in iodide is much higher than which in iodate, indicating that 127I and 129I have different circulation pathway. Besides, due to the exist of eastern subtropical North Pacific oxygen minimum zones (ESTNP-OMZs), the 127I--127IO3- differences in the eastern Pacific Ocean are obvious less in comparison with which in the western Pacific Ocean, at the same time, the differences between 129I-/127I- and 129IO3-/127IO3- also decrease in the eastern Pacific Ocean. The results suggest that in-situ reduction from iodate to iodide occurs in the ESTNP-OMZs.