Time course profile of Chlorine-36 in Greenland SE dome ice core

Prof. Hiroyuki Matsuzaki1, Ms. Miwako Toya1, Dr. Kazuho Horiuchi2, Dr. Yoshinori Iizuka3

1MALT, The University Of Tokyo, Tokyo, Japan, 2Hirosaki University, Hirosaki, Japan, 3Hokkaido University, Sapporo, Japan

Chlorine-36 (half life: 3.01E5 yr) is a neutron activated nuclide from Cl-35. In the process of atmospheric nuclear weapon testing held on the ocean, seawater is blew up and Cl-35 in seawater is irradiated by neutron flux, consequently, vast amount of Cl-36 is produced. In the case of nuclear weapon testing on the continent, Cl-36 is considered not to be produced. Produced Cl-36 is transported by the atmospheric circulation and falls down on various sites on the earth including the polar regions. The ice core is a good archive that preserves a time-course records of various atmospheric nuclides including Cl-36. In this study, a time-course record of Cl-36 in Greenland SE-dome ice core was analyzed with high time resolution.
Greenland SE-dome is located at 7.18 deg. North, 36.37 deg West at the altitude 3170 m. The ice core this study analyzed was taken in 2015 and covers years 2015 to 1955 [1, 2]. Concentration of major elements and oxygen isotopic ratio had been analyzed and published [3]. We analyzed Cl-36 from 1956 to 1983 with about half year time resolution or better. A clear peak corresponding to the nuclear weapon testing was observed. The time course profile of our study is quite different from that of Iodine-129 taken from the same ice core previously [4]. I-129 takes its one peak at around the weapon testing and after the peak increases again towards to the present which is due to the operation of the spent fuel reprocessing plant. The peak positions of Cl-36 and I-129 are also different. These observation is considered to reflect the difference of the production processes between two nuclides.

References:
[1] Y. Iizuka, et al. (2016) Bulletin of Glaciological Research, 34, 1-10.
[2] R. Furukawa, et al. (2017) J. of Geophysical Research: Atmospheres, 122, 10873–10887.
[3] Y. Iizuka, et al. (2018) J. of Geophysical Research: Atmospheres, 123, 574-589.
[4] A.T. Bautista VII, et al. (2018) J. of Environ. Radioactivity, 184-185, 14-21.


Biography:

Head of MALT (Micro Analysis Laboratory, Tandem accelerator), The University of Tokyo. The speciality is AMS and Isotope Geochemistry. He had developed methods of AMS for various nuclides. In the application field, he stresses on the Iodine isotope system. He is also a faculty member of Department of Nuclear Engineering and Management, School of Engineering and studies and teaches mainly nuclides analysis and environmental impact assessment of artificial nuclides.

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Date

Nov 17 2021

Time

WEDNESDAY
11:45 am - 12:40 pm