A theoretical description of diffusion and migration of Cs-137 in soil

Careful measurements of activity concentrations of Cs-137 in soil samples t aken layer by layer in autumn of 1999 in Slovenia are confronted with a pre diction based on the diffusion-convection equation with a boundary conditio n which - unlike the boundary conditions applied in the literature so far - conserves the deposited activity over time, except for the natural decay. It is shown that it is essential to consider the deposits from atmospheric nuclear weapons tests and the Chernobyl accident to arrive at a good fit to the measured data. The corresponding Green's function as well as the diffu sion constant and migration speed based on the analysis are given. (C) 2001 Elsevier Science Ltd. All rights reserved.