The Migration of ¹³⁷Cs and⁹⁰Sr in Multilayered Soils: Results from Batch, Column, and Fallout Investigations

Rates of migration, retardation factors, and distribution coefficients of ¹³⁷Cs and ⁹⁰Sr were determined in the various horizons of three typical soils (podsol, ranker, and brown soil) by employing batch procedures, column experiments, and evaluating the measured distribution of these radionuclides in the field as a result of their deposition from worldwide fallout. To obtain the distribution coefficients of the radionuclides for each soil horizon from the column experiments, the radionuclide distribution in the undisturbed soil monoliths (1 m long, 30-cm diam) was determined from the outside by a scanner technique after various times. The columns were irrigated with rainwater using the same quantities as observed at the site of sampling. Tritium labeled rainwater was used to obtain the hydrodynamic properties of the soil columns (pore water velocity, dispersion coefficient, and volumetric moisture content). Assuming that the fallout investigations yielded the most realistic results, the observations suggest that column experiments performed in the laboratory under approximately natural conditions can be used to obtain fairly realistic information about the migration of ¹³⁷Cs and ⁹⁰Sr in these soils. The use of distribution coefficients from batch methods for the prediction of radionuclide movement, on the other hand, can be misleading, especially in soil horizons rich in organic matter.