Determination of iodine mobility in the soil vadose zone using long-term column experiments

129I is emitted continuously in large amounts by reprocessing plants in La Hague and Sellafield. For determination of mobility in soil, we provide results of column experiments with undisturbed natural soils. Directly after short-term (28 days) contact with water from the bottom, iodine shows high upwards mobility only due to capillary forces. Furthermore, desiccation of the contaminated tracer reservoir led to an even stronger migration effect, which indicates remobilization of iodine from the drying soil layers. Chemical speciation proves difficult, as either gaseous iodine or organically bound iodine attached to dissolved organic matter are possible for the upward migration processes.