Changes of absorbed dose rate in air in metropolitan Tokyo relating to radiocesium released from the Fukushima Daiichi Nuclear Power Plant accident: Results of a five-year study


Autoři: Kazumasa Inoue aff001;  Hiroshi Tsuruoka aff001;  Hideo Shimizu aff001;  Moeko Arai aff001;  Nimelan Veerasamy aff001;  Mizuho Tsukada aff001;  Ken Ichimura aff001;  Shuto Nakazawa aff001;  Yoshiaki Taguchi aff001;  Masahiro Fukushi aff001
Působiště autorů: Department of Radiological Sciences, Graduate School of Human Health Sciences, Tokyo Metropolitan University, Arakawa-ku, Tokyo, Japan aff001;  Department of Radiological Sciences, Tsukuba International University, Tsuchiura, Ibaraki, Japan aff002
Vyšlo v časopise: PLoS ONE 14(10)
Kategorie: Research Article
doi: 10.1371/journal.pone.0224449

Souhrn

Car-borne surveys were carried out in metropolitan Tokyo, Japan, in 2015, 2016, 2017 and 2018 to estimate the transition of absorbed dose rate in air from the Fukushima Daiichi Nuclear Power Plant accident. Additionally, the future transition of absorbed dose rates in air based on this five-year study and including previously reported measurements done in 2014 by the authors was analyzed because central Tokyo has large areas covered with asphalt and concrete. The average absorbed dose rate in air (range) in the whole area of Tokyo measured in 2018 was 59 ± 9 nGy h-1 (28–105 nGy h-1), and it was slightly decreased compared to the previously reported value measured in 2011 (61 nGy h-1; 30–200 nGy h-1). In the detailed dose rate distribution map, while areas of higher dose rates exceeding 70 nGy h-1 had been observed on the eastern and western ends of Tokyo after 2014, the dose rates in these areas have decreased yearly. Especially, the decreasing dose rate from radiocesium (Cs-134 + Cs-137) in the eastern end of Tokyo which is mainly covered by asphalt was higher than that measured in the western end which is mainly covered by forest. The percent reductions for the eastern end in the years 2014–2015, 2015–2016, 2016–2017 and 2017–2018 were 49%, 21%, 18% and 16%, and those percent reductions for western end were 26%, 18%, 6% and 3%, respectively. Additionally, the decrease for dose rate from radiocesium depended on the types of asphalt, and that on porous asphalt was larger than the decrease on standard asphalt.

Klíčová slova:

Islands – Pacific Ocean – Surveys – Urban areas – Dosimetry – Dust – Nuclear power – Porous materials


Zdroje

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2019 Číslo 10