Abstract
We investigated the relationship between radiocaesium(134Cs and 137Cs) concentration(specific radio activity:Bq/kg) in rice and the paddy soil in Iitate village where people evacuated because of the high levels of radioactive contamination caused by the Fukushima Daiichi nuclear disaster. The radiocaesium concentration was measured of paddy soil and of lowland rice grown on variously decontaminated paddy soil in the year 2012 and 2013. The results showed that the concentration of radiocaesium in the brown rice cultured in the field of Sasu and Maeda with 2000 - 6000Bq/kg(DW) soil(0 - 15cm depth) was below 40Bq/kg, which was below the new standard for food(100Bq/kg), and the concentration of radiocaesium in the brown rice depended on the decontamination level of the paddy soil. In addition, the radiocaesium in rice was reduced depending on the exchangeable K content of the soil, which comes to plateau around 20mg K2O/100g dry soil. However, in 2013, in the fields of Komiya where the radiocaesium concentration was higher than 8000Bq/kg(DW) even after decontamination, brown rice with higher than 100Bq/kg was harvested, indicating the necessity of further decontamination. Overall, our results show that the suitable decontamination and additional fertilization of K can make the radiocaesium concentration of rice much lower than the new standard.
