Uranium-236 as a new oceanic tracer: A first depth profile in the Japan Sea and comparison with caesium-137

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• 作者：Aya Sakaguchi^a ; ^{ayaskgc@hiroshima-u.ac.jp} ; Akinobu Kadokura^a ; Peter Steier^b ; Yoshio Takahashi^a ; Kiyoshi Shizuma^c ; Masaharu Hoshi^d ; Tomoeki Nakakuki^a ; Masayoshi Yamamoto^e
• 关键词：the Japan Sea ; GEOTRACES ; U-236 ; Cs-137 ; global fallout
• 刊名：Earth and Planetary Science Letters
• 出版年：2012
• 期刊代码：18_0012821x
• 类别：ph
• 出版时间：1 June, 2012
• 卷：333-334
• 期：Complete
• 页码：165-170
• 文件大小：464 K

摘要

We present a feasibility study for using ²³⁶U as an oceanic circulation tracer based on depth profiles of ²³⁶U and ¹³⁷Cs in the Japan/East Sea. The concentration of the predominantly anthropogenic ²³⁶U, measured with Accelerator Mass Spectrometry (AMS), decreased from (13卤3)脳10⁶ atom/kg in surface water to (1.6卤0.3)脳10⁶ atom/kg close to the sea floor (2800 m). The profile has a smooth trend with depth and concentration values are generally proportional to that of ¹³⁷Cs for the same water samples, but with a slightly lower ratio of ¹³⁷Cs/²³⁶U below 2000 m. The cumulative inventory of dissolved ²³⁶U in the water column was estimated to be (13.7卤0.9)脳10¹² atom/m², which is similar to the global-fallout level (17.8脳10¹² atom/m²) in Japan. Additional analyses of suspended solids (SS) and bottom sediments yielded negligible amounts of ²³⁶U. Our results suggest that ²³⁶U behaves as a conservative nuclide in seawater, with potential advantages over other tracers of oceanic circulation.