Andrey Ivanovich Sanzharov

From 1978 to 2021, the migration parameters and dynamics of the distribution of ¹³⁷Cs in arable and virgin soils of the Tula region were studied. Identical patterns of distribution of ¹³⁷Cs from global and Chernobyl fallout in the soil profile of leached chernozems were revealed. On arable land, agrotechnical measures contribute to the uniform distribution of ¹³⁷Cs in the arable soil layer. In virgin soil horizons of chernozem soils of meadow phytocenoses, the processes of redistribution of radionuclides in the surface layers were most active in the first 10-year period after the fallout, which this contributed to the equalization of ¹³⁷Cs content in layers 0–2 and 2–5 cm and its increase in the 5–10 cm layer to more than 30% by the beginning of 2000. Nowadays, more than 75% of the ¹³⁷Cs content in virgin chernozem soils of the Tula region is concentrated in the upper 15 cm layer, and the penetration depth of radionuclides reaches 40–45 cm.

The article discusses the processes of transition to the aqueous phase and uptake from it by plants of stable (Cd) and radioactive (¹⁰⁹Cd) isotopes. Regularities of the distribution of Cd/¹⁰⁹Cd between different forms of their chemical compounds in the soil were revealed by means of sequental extraction procedure (SEP) according to the Tessier-Förstner method. It was shown that content of labile and conditionally labile forms of compounds (fraction F1-F3) of stable Cd was 1,2–1,8 times less than that of radioactive ¹⁰⁹Cd and, conversely, 2,4–5,3 times more fixed conservative forms of metal compounds (fraction F4-F6). The Cd concentration, ¹⁰⁹Cd activity concentration, distribution and concentration coefficients of natural Cd and ¹⁰⁹Cd radionuclide, accumulation and removal of metal by plants were evaluated. Values of enrichment coefficients of natural (stable) Cd contained in sequentially extracted chemical fractions by ¹⁰⁹Cd radioisotope were determined, the value of stock of labile cadmium compounds in studied soil was calculated. Based on the results of solid-state ¹³C NMR spectrometry, the qualitative composition of high-molecular organic compounds of the soil solution was determined and their ability to specifically sorb heavy metal cations was assessed.