No abstract

This study aimed to evaluate the effect of rice plant root activity on the chemical form of stable iodine (I) in a cultivated soil solution. Concentrations of I−, IO3− and organic-I were analyzed 4 days after exposure I− or IO3− solutions to each of the cultivated soil surface. When exposed to I−, its concentration in the cultivated soil was approximately the same as that in the non-planted soil. When the rhizosphere was exposed to IO3−, the I− concentration in the soil increased under cultivation conditions. IO3− remained undetected in the soil solution. The organic-I concentration in the cultivated soil solution was higher than that in the non-cultivated soil. Concentrations of organic-I increased under IO3− addition compared to I− addition. A weak positive correlation was observed between the TTC-reducing activity of plant roots, and the total and organic-I concentrations in the soil solution. It was suggested that the amount of organic I formed from IO3− was determined by the reducing activity of the roots.

Apple is an important agricultural product in Aomori Prefecture, Japan, where the first commercial nuclear fuel reprocessing plant is currently under construction. As the behavior of radioiodine deposited on the surface of apple leaves is not well known, we studied the absorption and transfer to fruit of stable iodine applied onto the leaf surface. Droplets of NaI solution were applied to the leaf surface $\sim$86–89 days after flowering. The leaves were collected periodically and washed with detergent solution, followed by determination of iodine amounts absorbed or remaining on the leaf surface. Subsequently, iodine levels were determined separately for each part of the apple tree. Our results indicated that iodine applied on the surface of the leaf was absorbed and accumulated inside the leaf, but the transfer of absorbed iodine to the fruit was negligible; hence, iodine was less likely to accumulate in the fruit.

We investigated the transfer of stable Cs + and I− applied as droplets directly on the fruit surface of 3-y-old plumleaf crab apple trees to the fruit interior at different developmental stages. The proportions of Cs and I transferred to the fruit flesh by harvest time were 21–66% and 41–53%, respectively, with decreasing trends as the developmental stage progressed. Most of the Cs+ was gradually transferred from the surface to the skin and flesh, while I− rapidly penetrated the fruit in the days after the application, followed by slow transfer of small proportions. For both elements, prompt penetration of the flesh occurred 1–2 d after application. A compartment model for simulating each element’s behavior was constructed using all the data obtained. The Cs transfer model to the flesh can simulate the measured values well. For the model of I, prompt distribution to the skin is also necessary.