Describing the observed vertical transport of radiocesium in specific soils with three time-dependent models

In this paper three transport models are applied to describe the vertical migration process of Cs-137 in undisturbed soil. The same experimental data set is used for the calibration of each model. These data were obtained from areas in northeast Italy, where the Cs-137 deposition following the Chernobyl accident ranged from 20 to 40 kBq m(-2). A diffusion model (called DSF) is presented, which takes into account three states of cesium in the soil matrix: mobile, sorbed and bound. It is shown that this model provides a reasonably good description of the temporal evolution of the radiocesium profile in soil. In addition, a new version of the RABES model (called RABES I) is proposed, with only two free parameters: the rate of change of the vertical profile and the diffusion length in the equilibrium. This paper includes a critical evaluation among the DSF, RABES and RABES I models, considering, mainly, their predictive aspect about the temporal change of the radiocesium profile in soil. (C) 2001 Elsevier Science Ltd. All rights reserved.