title: Regional and global contributions of anthropogenic iodine-129 in monthly deposition samples collected in North East Japan between 2006 and 2015.
abstract: We measured the monthly atmospheric deposition flux of129I at Rokkasho, Aomori, Japan-the location of a commercial spent nuclear fuel reprocessing plant-from 2006 to 2015 to assess the impact of the plant on environmental129I levels. The plant is now under final safety assessment by a national authority after test operation using actual spent nuclear fuel. During cutting and chemical processing in test operations from April 2006 to October 2008,129I was discharged to the atmosphere and detected in our deposition samples.129I deposition fluxes largely followed the discharge pattern of129I from the plant to the atmosphere, and most of the deposited129I originated from the plant. In and after 2009,129I deposition fluxes decreased dramatically to reach the background level; the129I deposition fluxes at Rokkasho were almost the same as those at Hirosaki, where an additional sampling point was set up as a background site 85 km from the plant in 2011. The background129I deposition fluxes showed seasonal variation-high in winter and low in the other seasons-at both Rokkasho and Hirosaki. The results of a backward trajectory analysis of the air mass at Rokkasho suggested that reprocessing plants in Europe were the origins of the high129I flux in winter. The contribution of129I released from the Fukushima Dai-ichi Nuclear Power Plant accident to the129I deposition flux at Rokkasho in 2011 was small on the basis of the129I/131I activity ratio.
authors.affiliation: Department of Radioecology, Institute for Environmental Sciences, 1-7 Ienomae, Obuchi, Rokkasho, Kamikita, Aomori 039-3212, Japan. Electronic address: hhidenao@ies.or.jp.
authors.forename: Hidenao
authors.initials: H
authors.lastname: Hasegawa
authors.affiliation: Department of Radioecology, Institute for Environmental Sciences, 1-7 Ienomae, Obuchi, Rokkasho, Kamikita, Aomori 039-3212, Japan.
authors.forename: Hideki
authors.initials: H
authors.lastname: Kakiuchi
authors.affiliation: Department of Radioecology, Institute for Environmental Sciences, 1-7 Ienomae, Obuchi, Rokkasho, Kamikita, Aomori 039-3212, Japan.
authors.forename: Naofumi
authors.initials: N
authors.lastname: Akata
authors.affiliation: Department of Radioecology, Institute for Environmental Sciences, 1-7 Ienomae, Obuchi, Rokkasho, Kamikita, Aomori 039-3212, Japan.
authors.forename: Yoshihito
authors.initials: Y
authors.lastname: Ohtsuka
authors.affiliation: Department of Radioecology, Institute for Environmental Sciences, 1-7 Ienomae, Obuchi, Rokkasho, Kamikita, Aomori 039-3212, Japan.
authors.forename: Shun'ichi
authors.initials: S
authors.lastname: Hisamatsu
mesh_terms: D000396:Air Pollutants, Radioactive / Q000032:analysis*; D000398:Air Pollution, Radioactive / Q000706:statistics & numerical data*; D001272:Atmosphere / Q000737:chemistry; D062406:Fukushima Nuclear Accident; D007457:Iodine Radioisotopes / Q000032:analysis*; D007564:Japan; D011834:Radiation Monitoring
chemical_list: D000396:Air Pollutants, Radioactive; D007457:Iodine Radioisotopes
keywords: (129)I; (129)I/(127)I atomic ratio; Fukushima Dai-ichi Nuclear Power Plant; Reprocessing plant