Yearly Changes in Rice and Soil Radiocaesium Concentrations in Minamisoma City, Fukushima Prefecture, Japan—Monitoring Results from 2013 to 2016

• Published in: RADIOISOTOPES 2019/01/15, Vol.68(1), pp.1-12
• Main Authors: Suzuki, Yoshimasa, Shoji, Ryousuke, Tsurumaki, Takahiro, Matsubara, Tatsuya, Tamaki, Syouhei, Nakajima, Kousei, Tsuruta, Ryousuke, Yoshikawa, Natsuki, Ishii, Hideki, Nogawa, Norio, Nonaka, Masanori, Harada, Naoki
• Format: Article
• Language: English
• Subjects: caesium-137; Fukushima Dai-ichi Nuclear Power Plant Accident; Minamisoma; planar distribution in paddy; rice
• ISSN: 0033-8303; 1884-4111
• DOI: 10.3769/radioisotopes.68.1

We monitored soil and rice radiocaesium concentrations in paddy fields in Minamisoma City, Fukushima Prefecture, Japan, from 2013 to 2016. As a result, brown rice samples collected in 2013 contained average 67 Bq/kg-dry weight (dw) of 137Cs. Five in the 9 samples exceeded 100 Bq/kg radiocaesium, which is the limit for food radioactive contamination in Japan. This is presumably due to radiocaesium fallout led by debris removal operations in the Fukushima Dai-ichi Nuclear Power Plant on 19 August 2013. 137Cs concentrations in the brown rice samples collected in 2014–2016 contained only 2–8 Bq/kg-dw. The soil and rice samples collected near water inlets of the paddy fields showed higher 137Cs concentrations than those collected at center and near water outlets. Transfer factors of 137Cs from soil to brown rice also tended to be higher at the water inlets except 2013, suggesting that irrigation water can affect on radiocaesium concentration in rice plants.