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Updated: May 12, 2026

Separation of Uranium and Thorium for 230Th-U Dating of Submarine Hydrothermal Sulfides
Published on: May 20, 2019
Uranium-236 as a new oceanic tracer: A first depth profile in the Japan Sea and comparison with caesium-137
Aya Sakaguchi1, Akinobu Kadokura, Peter Steier
1Graduate School of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima 739-8526, Japan.
Abstract:
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±3)×106 atom/kg in surface water to (1.6±0.3)×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±0.9)×1012 atom/m2, which is similar to the global-fallout level (17.8×1012 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.
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