Fig. 1　Relative inventory of components in urban areas (2015)

Those figures present the percentages of inventories relative to the values of the inventories on planar permeable fields measured in 2015 and converted to those immediately after the accident. The relative inventories four years after the accident were significantly low on paved ground and on building surface materials in the evacuation zone in which decontamination had not been conducted. These results indicate that large amounts of radioactive Cs deposited in residential areas were removed by the initial runoff and subsequent wash-off effects of rainfall, even without decontamination.

Fig. 2　Relative inventory of surface materials of roofs and rooftops

Porous materials such as mortar showed significantly higher relative ¹³⁷Cs inventories than others; smooth-surface materials such as glazed tile and metallic slate showed obviously smaller values. This indicates that ¹³⁷Cs deposited on smooth-surface materials are easily and quickly removed from the surface.

Related articles

• Is there any way to efficiently remove radioactive Cs from contaminated soil?

References

1. Yoshimura, K., Saito, K., and Fujiwara, K. (2017): Distribution of ¹³⁷Cs on Components in Urban Area Four Years after the Fukushima Dai–Ichi Nuclear Power Plant Accident, Journal of Environmental Radioactivity, vols.178–179, 48–54. https://doi.org/10.1016/j.jenvrad.2017.07.021
2. 長尾郁弥, 新里忠史, 佐々木祥人, 伊藤聡美, 渡辺貴善, 土肥輝美, 中西貴宏, 佐久間一幸, 萩原大樹, 舟木泰智, 鶴田忠彦, 御園生敏治, 吉村和也, 中間茂雄, 操上広志, 町田昌彦, 山田進, 板倉充洋, Malins, A., 奥村雅彦, Kim, M., Liu, X., 山口正秋, 石井康雄, 武藤琴美, 田籠久也, 齊藤宏, 武宮博, 関暁之, 北村哲浩, 飯島和毅(2019): 福島における放射性セシウムの環境動態研究の現状（平成30年度版）, JAEA-Research 2019-002, 235p. https://doi.org/10.11484/jaea-research-2019-002