Cs-137 vertical migration and contamination density in the soil of southern Transbaikale

The mechanism of vertical migration of radionuclides along the soil profile is studied. For large averaging, the process can be described by the sum o f the rates of effective diffusion and vertical advection of a radionuclide . The results of theoretical calculations of the Cs-137 concentration profi les in light and heavy soils for actually observed atmospheric fallout in 1 954-1999 are compared with the experimental profiles in mountain frozen-tai ga and mountain frozen-forest tundra soils of southern Transbaikal. The rat e of vertical migration is estimated and the reasons for the high Cs-137 co ntamination density of soil in this region are discussed. 4 figures, 27 ref erences.