title: Modelling radioiodine transport across a capillary fringe.
abstract: Due to its long radioactive half-life, iodine-129 is considered to be an important radionuclide in the context of underground radioactive waste disposal safety assessment. Iodine speciates as iodide (I-) in reducing conditions and iodate (IO3-) in oxidizing conditions. As iodate is more reactive, it is much less mobile than iodide. Consequently, in considering vertically upward transport within a soil profile, iodine will tend to accumulate at the top of the capillary fringe. In this paper, a model of iodine transport across a capillary fringe is developed by coupling equations for variably saturated flow, oxygen dynamics and rate-limited sorption. Model parameters are obtained by consideration of literature values, calibration on soil column data and other supporting laboratory experiments. The results demonstrate the importance of rate kinetics on the migration and bioavailability of radioiodine in the near-surface environment.
authors.affiliation: Department of Civil and Environmental Engineering, Imperial College, London, UK. simon.matthias@imperial.ac.uk
authors.forename: Simon A
authors.initials: SA
authors.lastname: Mathias
authors.forename: Adrian P
authors.initials: AP
authors.lastname: Butler
authors.forename: Howard S
authors.initials: HS
authors.lastname: Wheater
mesh_terms: D001692:Biological Transport; D002138:Calibration; D004784:Environmental Monitoring / Q000379:methods*; D004867:Equipment Design; D006863:Hydrogen-Ion Concentration; D007454:Iodides / Q000032:analysis; D007455:Iodine / Q000737:chemistry; D007457:Iodine Radioisotopes / Q000737:chemistry; D007700:Kinetics; D008962:Models, Theoretical; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry; D011834:Radiation Monitoring / Q000379:methods*; D012990:Soil Pollutants, Radioactive / Q000032:analysis*; D014872:Water Movements
chemical_list: D007454:Iodides; D007457:Iodine Radioisotopes; D012990:Soil Pollutants, Radioactive; D007455:Iodine; D010100:Oxygen