Depth profiles of radioactive cesium in soil using a scraper plate over a wide area surrounding the Fukushima Dai-ichi Nuclear Power Plant, Japan

福島第一原子力発電所周辺の広い範囲でのスクレーパー・プレートを用いた土壌中放射性セシウムの深度分布

松田 規宏  ; 三上 智   ; 下浦 享*; 高橋 純子*; 中野 雅和; 島田 清貴*; 宇野 騎一郎; 萩原 成朝; 斎藤 公明  

Matsuda, Norihiro; Mikami, Satoshi; Shimoura, Susumu*; Takahashi, Junko*; Nakano, Masakazu; Shimada, Kiyotaka*; Uno, Kiichiro; Hagiwara, Shigetomo; Saito, Kimiaki

Depth profiles of radioactive cesium from the Fukushima accident in soils was obtained using a scraper plate three times between December 2011 and December 2012. In most of the obtained depth profiles, it was possible to fit the concentration to a function of mass depth as either an exponential or sech function. By using those functions, following three parameters were estimated: (1) relaxation mass depth (g cm), (2) effective relaxation mass depth (g cm), and (3) 1/10 depth L (cm). It was observed that depth profiles at some study sites deviated from the typical exponential distributions over time. Downward migration rate V (kg m y) estimated by the sech function were in good agreement with those found by a realistic approach using a diffusion and migration model.