title: Uranium-236 as a new oceanic tracer: A first depth profile in the Japan Sea and comparison with caesium-137.
abstract: We present a feasibility study for using236U as an oceanic circulation tracer based on depth profiles of236U and137Cs in the Japan/East Sea. The concentration of the predominantly anthropogenic236U, measured with Accelerator Mass Spectrometry (AMS), decreased from (13±3)×106atom/kg in surface water to (1.6±0.3)×106atom/kg close to the sea floor (2800 m). The profile has a smooth trend with depth and concentration values are generally proportional to that of137Cs for the same water samples, but with a slightly lower ratio of137Cs/236U below 2000 m. The cumulative inventory of dissolved236U in the water column was estimated to be (13.7±0.9)×1012atom/m2, which is similar to the global-fallout level (17.8×1012atom/m2) in Japan. Additional analyses of suspended solids (SS) and bottom sediments yielded negligible amounts of236U. Our results suggest that236U behaves as a conservative nuclide in seawater, with potential advantages over other tracers of oceanic circulation.
authors.affiliation: Graduate School of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima 739-8526, Japan.
authors.forename: Aya
authors.initials: A
authors.lastname: Sakaguchi
authors.forename: Akinobu
authors.initials: A
authors.lastname: Kadokura
authors.forename: Peter
authors.initials: P
authors.lastname: Steier
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Takahashi
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Shizuma
authors.forename: Masaharu
authors.initials: M
authors.lastname: Hoshi
authors.forename: Tomoeki
authors.initials: T
authors.lastname: Nakakuki
authors.forename: Masayoshi
authors.initials: M
authors.lastname: Yamamoto
keywords: Cs-137; GEOTRACES; U-236; global fallout; the Japan Sea
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