Cs and K annual fluxes in a cropland and forest ecosystems twenty-four years after the Chernobyl accident.

Biological cycles of the Chernobyl originated cesium-137 (Cs, radiocesium) and the natural potassium (K) in oak, birch, and pine forest, and wheat cropland in Russian Federation, approximately 500 km northeast of the Chernobyl Nuclear Power Plant, were subject to a multiyear monitoring. By 2010, the annual return of Cs from forest vegetation to the soil in dead tree components still exceeds its annual accumulation in the tree phytomass by a factor of 4-6, apparently due to residual surface contamination in the external bark and the ongoing process of tree stand decontamination following the initial fallout. In the cropland, both ascending and descending fluxes of Cs are close to the steady state.

Spatial Distribution of ¹³⁷Cs in Soil of Spruce Forest in the Distant Zone of Chernobyl Fallout.

The vertical distribution of ¹³⁷Cs in Albeluvisols of the spruce forest in the Roslavl district of Smolensk region was investigated. The statistical characteristics of spatial variability and distribution laws for the activity con- centrations and activity depositions of ¹³⁷Cs in upper soil layers (forest litter, 0-5, 5-10, 10-19 cm) were de- termined. Positive correlations between the height, crown length of spruce trees and the content of ¹³⁷Cs in the soil under them were revealed.

[On the problem of biodiagnostics under conditions of radioactive contamination].

The possibilities of biodiagnostics methods (bioindication and bioassay) have been analyzed for conditions of radioactive contamination of natural ecosystems components. The prospects of using biodiagnostics data to address some practical radioecology problems are discussed. The data on dynamics of long-term indicators in the ecosystems contaminated after the Chernobyl accident are shown.

[The role of vegetation cover in regulation of fluxes of the technogenic radionuclides at the different stages after radioactive fallout].

In remote period after the radioactive fallout the biological cycle of 137Cs in pine forests of northern forest-steppe zone and Bryanskoe Polissye become different. In pine forests (northern forest-steppe zone) with dark grey forest soil 137Cs flux to the soil with litterfall exceeds its influx to the vegetation by a factor of 5. Thus biological cycle of 137Cs differs from the cycle of stable K and till now its main characteristic feature is domination of 137Cs flux to the soil with litterfall.

[The concentration and distribution of 137Cs in soils of forest and agricultural ecosystems of Tula Region].

The paper deals with a comparative study of 137Cs contamination in forest, old arable and cultivated soils of Tula Region. Initial interception of Chernobyl derived 137Cs is higher in forest ecosystems: oak-forest > birch-forest > pine-forest > agricultural ecosystems. Vertical migration of 137Cs in deeper layers of soils was intensive in agricultural ecosystems: cultivated soils > old arable soils > birch-forest soils > oak-forest soils > pine-forest soils.

[Radioecological problems in coastal landscapes of the Sea of Azov].

The features of the spatial distribution, of the migration, and of the accumulation of natural (232Th) and manmade (137Cs) radioactive nuclides in the coastal landscapes of the Sea of Azov are studied. It was shown, that the specific activity of 232Th in the accumulation of the so-called "black sands" was shown as high as 6000 Bq/kg, that increases the natural geochemical background in 200 times. The impact of aerial transfer of the "black sands" on 232Th migration and accumulation in the soil-plant system was clarified.

[137Cs distribution and accumulation in the tissues of cultivated fungi (Pleurotus ostreatus)].

The authors examined 137Cs accumulation and distribution in different structures and tissues of Pleurotus ostreatus cultivated under laboratory conditions. The fungi were shown to concentrate 137Cs. A higher concentrations of the radionuclides in the fungi compared to their substrate is manifested at the first stages of the fruit body formation, the maximum content of 137Cs is accumulated by fungi in the middle of bearing stage.

[Basic features of seasonal and multi-year dynamics of Cs-137 and Sr-90 in wood].

Basic features of seasonal and multiyear dynamics of accumulation of Chernobyl-derived 137Cs and 90Sr in wood are considered. Seasonal variation in the radionuclide concentration are shown to be more regular and predictable than the multiyear variation. Seasonal dynamics of 137Cs is opposite by trend to that of 90Sr.

[The biogeochemistry of the radionuclides of the Chernobyl release in the forest ecosystems of the European portion of the CIS].

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.

Cs-137 content in the mushrooms of radioactive contaminated zones of the European part of the CIS.

Samples of different species of mushrooms were collected in the forests contaminated by Chernobyl (ChNPP) accident fallout debris. Sampling sites were located at a distance of 5-200 km from Chernobyl NPP. Transfer factors (TF) for Cs-137 from soil to mushrooms varied from 12 to 5060 nCi kg-1/Ci km-2; TF variability depended on the distance from ChNPP, mushroom species and growth conditions.