Effect of aging on availability of iodine in grassland soil collected in Rokkasho, Japan

Time-dependent changes in the availability of iodine in soil were investigated for 23 months. Stable iodine was added to a grassland soil collected in Rokkasho, Japan. Whether iodine was added as I − or IO 3 − , its water extractability decreased drastically for first 4 months after addition and then slightly decreased thereafter. These results indicate that most of the I − and IO 3 − added to the soil was rapidly converted to an insoluble form. The soil-to-grass transfer factor of the added iodine showed a double exponential decline with time, similar to the decline observed for the water-extraction yield.