Fukushima-derived radiocesium in the western North Pacific in 2014

Yuichiro Kumamoto; Michio Aoyama; Yasunori Hamajima; Hisao Nagai; Takeyasu Yamagata; Yoshimi Kawai; Eitarou Oka; Atsushi Yamaguchi; Keiri Imai; Akihiko Murata

doi:10.1007/s10967-016-5055-3

Fukushima-derived radiocesium in the western North Pacific in 2014

J Radioanal Nucl Chem. 2017;311(2):1209-1217. doi: 10.1007/s10967-016-5055-3. Epub 2016 Oct 3.

Authors

Affiliations

¹ Research and Development Center for Global Change, Japan Agency for Marine-Earth Science and Technology, 2-15 Natushima-cho, Yokosuka, Kanagawa 237-0061 Japan.
² Institute of Environmental Radioactivity, Fukushima University, 1-1 Kanayagawa, Fukushima, Fukushima 960-1296 Japan.
³ Low Level Radioactivity Laboratory, Kanazawa University, Wake, Nomi, Ishikawa 923-1224 Japan.
⁴ Department of Chemistry, College of Humanities and Sciences, Nihon University, 3-25-40 Sakurajousui, Setagaya Ward, Tokyo, 156-8550 Japan.
⁵ Atmosphere and Ocean Research Institute, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8564 Japan.
⁶ Graduate School of Fisheries Sciences, Hokkaido University, 3-1-1 Minato-cho, Hakodate, Hokkaido 041-8611 Japan.
⁷ School of Fisheries Sciences, Hokkaido University, 3-1-1 Minato-cho, Hakodate, Hokkaido 041-8611 Japan.

Abstract

In 2014, we measured activity concentration of radiocesium in the western North Pacific Ocean. In the north of Kuroshio Front high activity concentration of Fukushima-derived radiocesium in surface mixed layer in 2012 had been transported eastward by 2014. In the south of the front we found a radiocesium subsurface maximum in 200-600 m depth, which was similar to that observed in 2012. The subsurface maximum spread southward from 18°N to 15°N between 2012 and 2014, which suggests spreading of Fukushima-derived radiocesium into the whole western subtropical area by 2014 due to formation and subduction of the subtropical mode water.

Keywords: Fukushima Dai-ichi nuclear power plant accident; North Pacific Ocean; Radiocesium.