Iodine transfer from agricultural soils to edible part of crops

Abstract

Information about the distribution and cycling of stable iodine (I) in the environment is useful for dose estimation from its long-lived radioiodisotpe, 129 I, which is one of the most critical radionuclides to be managed for the safe disposal of nuclear fuel waste. The soil-to-plant transfer factor (TF) is an important parameter to predict internal radiation exposure pathways through the food chains using mathematical models. Therefore, we have measured stable I and bromine (Br) for comparison, in 142 crop samples and associated agricultural field soil samples collected throughout Japan. The crops were classified into eight groups, i.e. leafy vegetables, white part of leeks, fruit vegetables, tubers, root crops, legumes, wheat and barley (WB), and rice. The results showed that Br and I concentrations were higher in upland field soil samples than in paddy field soil samples. However, when we compared TF values of WB and brown rice, no statistical difference was observed. The highest geometric mean of TF for I, 1.4 × 10 2 , was obtained for leafy vegetables and fruit vegetables and that for Br, 1.5, was for fruit vegetables. TF for I was much lower than Br, as reported previously, maybe due to their different chemcial forms in soil and uptake behaviors by plant roots.