Transfer Factor of Radiocesium from Soil to Vegetables Grown in Decontaminated Soil in Fukushima.

In Fukushima, Japan, where soils were contaminated by radiocesium (Cs134+Cs137) due to the accident of the Fukushima Daiichi Nuclear Power Plant in 2011, farmlands were decontaminated by scraping a top 5 cm fertile soil layer containing most of fallout radiocesium as well. Decontaminated farmlands received a 5–10 cm thick rediocesium-free yet less-fertile sandy soil. We applied a cloud-based fertigation system to grow vegetables in the less-fertile sandy soil mixed with the original soil in a greenhouse. The radiocesium concentration in the sandy soil that we planted vegetables was 1,448 Bq/kg whereas that in a contaminated soil as a control was 30,351 Bq/kg. The radiocesium concentration of tomato grown in the decontaminated soil ranged between 0.3 and 0.8 Bq/kg, meaning the transfer factor (f=radiocesium concentration in vegitable/radiocesium concentration in soil) ranged between 0.0002 and 0.0006, whereas that of bell pepper ranged between 5.4 and 7.2 Bq/kg (f=0.004-0.005). The radiocesium concentration of spinach ranged between 6.2 and 9.0 Bq/kg (f=0.0042-0.0063), for a normal K application, but the radiocesium concentration decreased to 2.2 Bq/kg (f=0.0015) for a doubled K application. Spinach grown in the high radiocecium concentration soil contained 139.3 Bq/kg for the normal K application (f=0.0046) whereas the doubled K application reduced the radiocesium to 77.0 Bq/kg (f=0.0025). The transfer factors of spinach grown in either radiocesium concentration soil were similar although the K addition might be less effective to reduce a transfer rate in the high concentration of radiocesium soil.