Transfer of 137Cs to wild vegetables

For the evaluation of internal radiation dose, it is needed to estimate the amount of radionuclide incorporated to human body using a simulation model. 137Cesium (Cs) is easily transferred associating with food intake as well as potassium and so, Cs is an important nuclide for evaluation of internal radiation. 137Cs concentrations in wild vegetables are higher than those of cultured vegetables and milk. Therefore, the transfer coefficients of 137Cs from soil to wild vegetables were estimated in this study. Wild vegetables and soils of their farms were collected in the Hakkoda Mountain range of Aomori Prefecture. The levels of 137Cs in wild vegetables were 0.42-18.35 (Bq/kg), whereas those in cabbage and spinach were 0.08 and 0.01 (Bq/kg), respectively, indicating that the Cs level is dozens to several hundreds times higher in wild vegetables than cultured ones. And the transfer coefficient was estimated as 0.003-0.94 for the former and 0.001-0.8 for the latter. On the other hand, 137Cs levels of the soils on which wild vegetables grew was 28.0 Bq/kg and it was 3.9 Bq/kg for the farm soil. Furthermore, the effects of water content and pH of the soil on the transfer coefficient were studied. (M.N.)