The ecological and toxicological assessment of the of the soil and vegetation cover at the Streletskaya Steppe site of the V.V. Alekhin Central Chernozem Reserve is presented. The contents of a number of heavy metals (HM) and radionuclides in the typical chernozem are determined. The values of concentration clarks of HM (Cc), geoaccumulation indices (Igeo) for As, Cd, Co, Cs, Cu, K, Pb, Sr, Zn, 232Th, 238U and pollution indices (PI) for individual HM in chernozem were calculated. It is shown that increased values of the pedogeochemical background in comparison with clark values in the lithosphere are observed only with respect to Cd and As. At the same time, for the studied HM (As, Cd, Cu, Pb, Zn), it can be argued that they do not pollute the soil. The content of radionuclides (40K, 137Cs, 232Th, 238U), HM and potassium in various types of natural steppe vegetation was determined. Based on the plant accumulation coefficients of HM and radionuclides, the degree of biophilicity of radionuclides and HM was estimated. The values of the aggregated transfer factors (Cag) 137Cs and 40K from soil to plants were also determined and a comparative analysis of the bioavailability of cesium and potassium during root uptake was carried out. The vertical distribution of 137Cs and 40K radionuclides in the root-inhabited soil layer of 0–20 cm was studied. It was established that 40K is evenly distributed in the root layer of the soil The features of the vertical distribution of 137Cs in the soil profile are noted, consisting in the displacement of the maximum from a depth of 0–5 to 5–10 cm. Based on the data obtained, the value of the migration coefficient 137Cs is calculated, taking into account the convective and diffusion components of the radionuclide translocation process in a typical chernozem.

The ecological and toxicological assessment of the soil and plant cover of a key site in the Streletskaya Steppe in the V.V. Alekhin Central Chernozem Reserve is presented. The content of heavy metals (HMs) and radionuclides in typical chernozem is determined. The clarkes of concentration of HMs (Cc); geoaccumulation lithogeochemical indices (Igeo) for As, Cd, Co, Cs, Cu, K, Pb, Sr, Zn, 232Th, and 238U; and pollution indices (PI) for individual HMs in chernozem have been calculated. It is shown that the pedogeochemical background is higher in comparison with the lithosphere clarkes only for Cd and As. In may be concluded that soils are not polluted with the studied HMs, namely, As, Cd, Cu, Pb, and Zn. The content of radionuclides (40K, 137Cs, 232Th, and 238U), HMs, and potassium in various types of natural steppe vegetation has been determined. Based on the plant accumulation coefficients of HMs and radionuclides, the biophilicity of radionuclides and HMs was estimated. The transfer factors (TFs) of 137Cs and 40K from soil to plants have been calculated, and a comparative analysis of the bioavailability of cesium and potassium during root uptake is performed. The vertical distribution of 137Cs and 40K radionuclides in the root-inhabited soil layer from 0- to 20-cm-thick is studied. It is shown that 40K is evenly distributed in the root-inhabited layer. The vertical distribution of 137Cs in the soil profile is characterized by the shift of the maximum from a depth of 0–5 to that of 5–10-cm. Based on the data obtained, the migration coefficient of 137Cs is calculated, taking into account the convective and diffusion components of the radionuclide translocation in typical chernozem.

The transfer of zinc (natural stable Zn and radioactive tracer 65Zn) to aqueous phase and its uptake by barley have been studied using a specially designed vegetation testbench comprising a lysimeter unit filled with coarse-textured soil and drainage and the vegetation vessels with aqueous barley culture. Although the zinc migration to soil aqueous phase and its uptake by plants are spatially separated, they are sequentially coupled. The patterns of Zn(65Zn) distribution among different compounds (chemical fractions) in soil were determined using parallel and sequential fractionation procedures. The relative content of native (stable) Zn in labile and conventionally labile forms is 2.1–6.5-fold lower as compared with the relative content of radionuclide 65Zn and, vice versa, 2.8–3.0-fold higher for conservative (fixed) fractions of the metal in soil. The dynamics of the following parameters were assessed: Zn concentration, 65Zn specific activity, distribution and concentration factors of natural Zn and 65Zn, and uptake and removal of the metal by plants. The enrichment factors of stable Zn, contained in sequentially extracted chemical fractions, with radioisotope 65Zn, were determined, and the pool of the labile zinc compounds in the studied soil was evaluated.

One of the sources of radionuclides released into the environment are radioactive waste storage. The plutonium isotopes concentration in the soils of the territory adjacent to the former radioactive waste storage facility in Obninsk was estimated. The cause of pollution was the depressurization of one of the storage tanks and the release of radionuclides due to its overflow with surface and ground waters in the period from 1998 to 1999. Samples were analyzed by alpha spectrometry with preliminary radiochemical isolation with complete decomposition of soil samples. The Pu-239+240 content range in the surface soil layer was 3.7-9.6 Bq/kg, with an average value of 6.7 Bq/kg, which is an order of magnitude higher than the level of its global fallout. In some samples, significant amounts of Pu-238 are observed, the relative content of which is 10-50% of Pu-239+240, that exceeds the its relative content due to the global fallout which is 2-5%. The depth distribution of plutonium isotopes has been studied. It has been established those significant concentrations of plutonium are observed to the depth of 95 cm for this territory. There is no definite dependence of the distribution of plutonium isotopes along the vertical soil profile. The random distribution of plutonium to the soil depth indicates that the source of Pu-239+240 are groundwater. Elevated concentrations of plutonium isotopes in the soil surface of the territory under consideration, its significant concentrations at soil depth indicates that the contamination is a consequence of the leakage of plutonium isotopes from the radioactive waste storage facility in Obninsk. The same concentrations can be expected in the lowland of the adjacent territory.

This study is devoted to the estimation of radionuclides global fallout levels in the soils of Commonwealth of Independent States (CIS) and Eastern Europe territory as a result of nuclear explosions. 58 standard soil samples were used, which were selected in different soil and climatic areas of the territory of CIS and Eastern Europe in 1978-2018. All samples were measured by gamma spectrometry. Determination of plutonium isotopes and strontium was performed according to the method of the joint determination of these radionuclides from one sample. IN the samples considered in this work, the content of( 60)Co,Eu- 154,Eu- 155 was below the detection limits, which were 0.4; 1.0 and 1.0, respectively. Natural radionuclides analysis results indicated that the obtained samples are typical soil samples without its abnormal contents. The content of( 137)Cs, Sr-90,Pu 239+240 in a 20 cm soil layer due to global fallout is (3.9 +/- 1.7), (2.2 +/- 0.8), (0.18 +/- 0.08) Bq/kg respectively, which considering the distribution of these radionuclides by depth and average soil density is (1.2 +/- 0.5) kBq/m(2) for Cs-137, (0.42 +/- 0.15) kBq/m(2)- Sr-90 and (55.0 +/- 24.0) Bq/m(2)-Pu 239+240. The isotopic ratios(137)Cs/Sr-90 and Cs-137/Pu239+240 for the territory of CIS and Eastern Europe are at the level (2.0 +/- 0.71) and (25 +/- 15), respectively.

The article provides a radiation-hygienic assessment of the current state of drinking water supply sources for the population in the observation area of the the Beloyarsk NPP and the Institute of Nuclear Materials. We determined the content of natural (234U, 238U, 226Ra, 228Ra, 210Po, 222Rn, 210Pb, 228Th, 230Th, 232Th) and technogenic (3H, 14C, 60Co, 90Sr, 134Cs, 137Cs, 238Pu, 239,240Pu, 241Am) radionuclides in drinking water of tap water, water boreholes and water wells in test settlements located at different distances and directions from radiation hazardous facilities. Results of monitoring of water sources in 2012–2013 and 2019 showed the radiation safety of drinking water in the vicinity of the Beloyarsk NPP according to several criteria. Thus, the maximum levels of the gross specific alpha-activity of radionuclides in water samples were 3.9 times lower than the control level (0.2 Bq/kg), the gross specific beta-activity was 5.7 times lower than the control level (1 Bq/ kg). Over the entire observation period, none of the drinking water samples exceeded the control levels both for individual radionuclides and for the sum of the ratios of specific activities to control levels. The content of natural and artificial radionuclides in drinking water near the Beloyarsk NPP decreases in the following order: water wells > water boreholes > tap water. For the past 20 years, there was a decrease in tritium specific activity in drinking water of the Beloyarsk NPP region by 20–35%, depending on the source of water supply. It was noted that the launch of the BN-800 reactor also did not lead to an increase in the content of other artificial radionuclides (90Sr, 137Cs) in groundwater. The average annual effective dose of internal exposure of the population due to drinking water consumption in the vicinity of the Beloyarsk NPP is 0.05 mSv, according to conservative estimates – 0.07 mSv, which is below the radiation safety threshold (0.1 mSv/a) recommended by the WHO. Natural radionuclides play the primary role in the formation of the annual average effective dose for internal irradiation (98.9%) due to drinking water consumption on the considered territories. 210Po makes the largest contribution to the dose from natural radioisotopes – 43%, somewhat less is made by 210Pb – 25%. The third place in the dose formation from natural radionuclides belongs to 234U (8%), 228Ra (7%), 226Ra (6%) and 230Th (6%). The contribution of other natural radioisotopes in the formation of the internal radiation dose from drinking water consumption does not exceed 2-3%. The contribution of technogenic radionuclides to the annual average effective dose from the consumption of drinking water is negligible (about 1%). Of the technogenic components, 90Sr (60%), 3H (20%), and 241Am (12%) play the most significant role in the formation of the internal exposure dose.