35 YEARS AFTER THE CLOSURE OF THE SEMIPALATINSK TEST SITE: RADIOACTIVE CONTAMINATION AND PATTERNS OF RADIONUCLIDE BEHAVIOR IN THE MAIN ENVIRONMENTAL COMPONENTS

The article summarizes data on radioactive contamination of the main environmental components of the Semipalatinsk Test Site (STS), including soil and vegetation cover, wildlife, surface waters, atmospheric air, and snow cover. The occurrence and distribution patterns of ³H, ⁹⁰Sr, ¹³⁷Cs, ²⁴¹Am, and ^239+240Pu, as well as the main mechanisms of their transfer among ecosystem components, are considered. The contamination of the territory is characterized by pronounced spatial heterogeneity, with the highest radionuclide levels associated with the epicenters of surface nuclear tests, radioactive fallout traces, areas around borehole outlets, water-filled craters, and zones affected by contaminated watercourses. In soils, most of the ¹³⁷Cs, ²⁴¹Am, and ^239+240Pu remains concentrated in the upper horizons and is associated with the solid phase, whereas ⁹⁰Sr exhibits the greatest vertical mobility. Radionuclide accumulation in plants and animals is determined by the contamination characteristics of their habitats, radionuclide properties, and species-specific biological characteristics. The highest levels of contamination in surface aquatic ecosystems are observed in artificial water bodies, bottom sediments, and watercourses at the Degelen site. The release of radionuclides into the atmosphere is associated with the transfer of ³H from contaminated waters and soil moisture, as well as with the resuspension and atmospheric transport of soil particles. The results demonstrate that present-day radioactive contamination of the STS is predominantly localized and is determined by the types of nuclear tests conducted and the subsequent redistribution of radionuclides in the environment.

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