The effect of soil sterilization on the ¹³⁷Cs transfer from soil to radish (Raphanus sativus var. sativus). Transfer experiment involving sterilized soil

Three different types of soil were collected at each of three locations: a persimmon orchard, an ume (Prunus mume, so to speak, 'a Japanese apricot') orchard, and a paddy field located 50-55 km northwest from Fukushima Daiichi Nuclear Power Plant. The goal was to investigate the involvement of microbes inhabiting these soils on the behavior of ¹³⁷Cs. The soils were sterilized with gamma ray irradiation for 30 hours (absorbed dose of 60 kGy) or with high-pressure steam (autoclave sterilization) at 121°C for 20 minutes. A radish cultivar (Raphanus sativus var. sativus) was then cultivated in those soils for 45 days, and the harvested taproots and leaves were testing using a Ge semiconductor detector for concentration of ¹³⁷Cs. The result showed that the concentration of ¹³⁷Cs in radishes cultivated in the sterilized soils with autoclave sterilization or gamma ray irradiation were significantly higher than in those cultivated in the unsterilized soils. An increase in the plant available ¹³⁷Cs could be caused by NH₄⁺ arisen from the multiple effects of the structural change of the soil, decomposition of organic matter, and/or extinction of the microbes by sterilization. (author)