Input of 137Cs and 90Sr into plants from the surface of soil aggregates and the intraped space

Soil aggregates with different localization of radionuclides—(a) only on the aggregate surface, (b) only in the intraped space, and (c) uniformly distributed throughout the aggregate volume—have been obtained under laboratory conditions, which has allowed separately assessing the roles of different aggregate parts in the uptake of radionuclides by plant roots and the reaggregation rate of the soil material. The uptake rate of the radionuclides localized on the surface of soil aggregates, especially 137Cs, by plants manifold exceeds their uptake observed at the localization of pollutants throughout the aggregate volume or only in their intraped material. The input rate of radionuclides into plants decreases with time. For 137Cs, this decrease is due to the strengthening of the sorption fixation of the radionuclide (about 15%) and the reaggregation of the soil material (85%). Under natural conditions, at a depth of 10 cm in the dark gray forest soil of a forest belt, aggregates 7–10 mm in size are subjected to 40–75% destruction and reaggregation on the average within a year, which corresponds, with consideration for the statistical dispersion of the initial data, to the aggregate lifetime of 1.5 to 3 years.