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The results of analysis of 137Cs aggregated transfer factors (Tag) to crops (cereals, potatoes, and vegetables) produced in the districts of Bryansk region, which were affected by the Chernobyl accident, are presented. In subsequent years, the aggregated transfer factors in the year of the deposition, as well as the dynamics of Tag, depended considerably on the fertility of contaminated soils. The transfer factors of 137Cs to crops were 3–8 times lower in areas with higher fertility (depending on the plant species) than in areas with low fertility and the most significant differences were observed for cereals. The decrease in Tag values was irregular. The half-lives of 137Cs aggregated transfer factors for the period from 1986 to 2021 have been calculated. It is shown that the first half-life values calculated for the period of intensive application of countermeasures (1987–1991) were 0.7 to 1.4 years. The second half-life values varied from 7.3 to 17.3 years for cereals. In some districts, a slow increase in 137Cs aggregated transfer factors was recorded after a strong reduction in 137Cs concentrations in crops after 1994, which can be explained by insufficient compensation for the reduction by the geochemical binding of 137Cs in the soil. Later, the dynamics of crop contamination was determined by multidirectional processes: an increase in 137Cs transfer to plants and a natural decrease in radionuclide bioavailability in soils under the influence of geochemical processes. In areas with intensive application of countermeasures, the reduction of Tag in crops was determined mainly by the effect of agrochemical countermeasures. In areas with limited application of countermeasures, natural biogeochemical processes determining radionuclide binding by the soil-absorbing complex made the predominant contribution to the reduction in Tag. The limitations of the approach based on the estimation of half-lives and the necessity of using the history of countermeasures, as well as the soil fertility for predicting the 137Cs intake by plants, have been recorded. [ABSTRACT FROM AUTHOR]

The data on the dynamics of the 137Cs transfer coefficients (Tf) for fodder in the long term after the Chernobyl accident (2008–2020) are presented. It is shown that the ecological half-lives of transfer coefficients varied from 7.8 to 28.9 years. The obtained estimates are consistent with the second half-life periods of transfer coefficients estimated based on data for the first eight years after the Chernobyl accident. The peculiarities of the dynamics of Tf to fodder were in good agreement with the scales of remedial actions carried out in the contaminated territories. [ABSTRACT FROM AUTHOR]

A methodological approach to substantiating the control levels of 137Cs in cattle feeds is presented based on the probabilistic nature of the parameters of transfer of 137Cs to cattle feeds and cattle milk and meat. A comparative analysis of global and Russian data on the parameters of 137Cs transfer from feed to livestock products has been made. It is shown that milk with 137Cs remains safe when the concentration of this radionuclide in the feed is at the existing control levels; however, this does not guarantee compliance with the hygienic standards for the content of 137Cs in meat. Based on the methodological approach, control levels are proposed for monitoring 137Cs in the feeds of dairy and beef cattle in areas contaminated after the Chernobyl accident. The use of the proposed control levels makes it possible to optimize livestock breeding technologies in the Russian areas contaminated after the Chernobyl accident. [ABSTRACT FROM AUTHOR]