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Title: Groundwater flow traced by bomb pulses of ³⁶Cl and tritiogenic ³He in a borehole
Authors: Mahara, Yasunori
Ohta, Tomoko
Author's alias: 馬原, 保典
Keywords: Global fallout
Bomb pulse
³⁶Cl
³H
Tri³He
Piston flow
Issue Date: 15-Sep-2019
Publisher: Elsevier B.V.
Journal title: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms
Volume: 455
Start page: 140
End page: 145
Abstract: In 2001, a borehole was drilled to 400 m depth below the ground surface of a tableland in northern Japan, where horizontal porous sedimentary rock strata are deposited. Fresh drill-core and groundwater samples were collected from the borehole for estimating global fallout bomb pulses of ³H, which becomes tritiogenic ³He (tri³He) through β-decay, and ³⁶Cl. In the northern hemisphere, the maximum fallout deposition of ³⁶Cl from nuclear testing was observed during 1954–1957, and that of ³H in 1963. Most ³H (half-life 12.3 y) in the rock porewater had decayed to tri³He during the 38 years between 1963 and 2001. In the borehole, bomb pulses were observed in profiles of tri³He and ³⁶Cl/Cl at 101 m and around 138 m depth below the ground surface, respectively. The downward groundwater velocity was estimated to be 2.9–3.1 m/y from the depth of the ³⁶Cl/Cl bomb pulse and 2.7 m/y from the depth of the tri³He bomb pulse. Although the two velocity estimates differ by 10–15%, it is possible to model groundwater flow in the tableland as downward piston flow without diffusion.
Rights: © 2018. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/
The full-text file will be made open to the public on 15 September 2021 in accordance with publisher's 'Terms and Conditions for Self-Archiving'.
この論文は出版社版でありません。引用の際には出版社版をご確認ご利用ください。
This is not the published version. Please cite only the published version.
URI: http://hdl.handle.net/2433/243002
DOI(Published Version): 10.1016/j.nimb.2018.12.023
Appears in Collections:馬原 保典

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