The 9-years dynamic of Chernobyl-derived radionuclides in the vegetation and soil covers of the forest ecosystems of the European part of the CIS is considered. The quantitative estimation has been done for main fluxes of Cs-137 in the forests of automorphic landscapes: influx to the vegetation, return with the litterfall, stem flow and throughfall, vertical migration in the soil profile (including intrasoil flow), and redistribution within the system of geochemically connected landscapes.

This paper reports on research on the migration of radionuclides, resulting from post Chernobyl fallout, in various types of natural soil. Experimental sites were established in 1987 at distances of 5-27 km from the site of the accident, corresponding to a deposition range of 0.2-300 MBq/m(2). Radionuclide distribution of (134,) (CS)-C-137, Sr-90,Ce-144 and Ru-106 in the soil profiles were studied in order to determine their migration characteristics. Today, eight years after the accident, forest litter still remains a major repository of radionuclides released into the forest ecosystems in the vicinity of the Chernobyl nuclear power plant.Radionuclide migration occurs mostly in the wet landscapes with boggy-peat soils, and especially in high-water landscapes with specific alluvial soils. Minimal migration activity is observed in the meadow-dry soils of watersheds. (CS)-C-134, 137 and Sr-90 are found to be equally mobile in the dry sandy soils of watersheds, while Sr-90 is distinctly more mobile in agrillaceous alluvial soils of the Pripyat river valley. Distribution of radionuclide composition down the profile of alluvial soils suggests that lessivage-like processes are taking place, with direct migration of the fallout particles occurring within the soil profile. The so-called hydromorphic (wet) landscapes, such as pear bogs and river valleys, are characterized by maximum radionuclide migration activity, while the minimum is observed in dry (automorphic) sandy soils.