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The concentration and sorption behavior of 237 Np on the bottom sediments of water bodies in the Far East region of Russia (Lake Khanka and Peter the Great Bay) were studied for the first time. The 237 Np concentrations vary from 1.06 × 10 -6 to 4.43 × 10 -5 mBq g -1 in the bottom sediments of Lake Khanka and from 1.05 × 10 -4 to 2.52 × 10 -3 mBq g -1 for Amur Bay. The experiment on the adsorption of Np on marine and lake sediment showed that it is sorbed through complexation with silicates (albite, leucite). The Np sorption isotherm on marine sediments is described by the Langmuir equation; the distribution coefficients (Kd) of Np vary from 57 to 588 mL g -1 . For lake sediments, the isotherm is described by the Henry equation; the Kd value reaches 935 mL g -1 ., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Kuzmenkova Natalia reports financial support was provided by Russian Science Foundation. Hou Xiaolin reports financial support was provided by National Natural Science Foundation of China. Co-author is an assocaited editor in Journal of Environmental radioactivity., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

The purposes of this study are to determine the content and origin of anthropogenic fallout radionuclides (FRN) in soils of Mount Khuko, located in the western sector of the Caucasus Mountains and to assess the possibility to use them for evaluation of sediment redistribution for the alpine grasslands,. The field study was carried out in August 2019 near the top of Mount Khuko, located in the western part of the main Caucasus Mountain Ridge. Integral and incremental soil samples were collected from the different morphological units of the studied area. The content of 137 Cs and 241 Am in soil samples was evaluated using laboratory gamma-spectrometry. A part of samples was selected for Pu isotopes extraction and then alpha-spectrometric analysis. It was established that the 137 Cs contamination of soils in the studied area has at least two sources of origin. The first source is the 137 Cs bomb-derived fallout after the bomb tests in 1950-60th, which is widespread across the globe. The second source is 137 Cs Chernobyl-derived fallout High random variability (Cv = 25-42%) was found within reference sites, located at the undisturbed areas on the local flat interfluves due to high variability of soil characteristics (grain size, density, organic matter content etc.). However minimum spatial variability (range 12,2-14,3 kBq/m 2 ) was identified for the mean value of 137 Cs inventories for all 5 reference sites located in the different parts of the studied area. It is difficult to separate individual peaks of the bomb-derived and Chernobyl-derived 137 Cs falloutin sediment sinks with low sedimentation rates. Application 239,240 Pu as an additional chronological marker allows to identify the origin of above mention peaks in the soils of alpine grasslands and of dry lake bottom., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

About ten years have passed since the last published report in Russian on the speciation and distribution features of radionuclides in the bottom sediment of Production Association (PA) "Mayak" (further mentioned as Mayak) artificial reservoirs. Herein, the desorption parameters of 137 Cs, 90 Sr, 241 Am, and 238,239+240 Pu and their association with bottom sediment components were investigated in two Mayak reservoirs (R-17 (decommissioned) and R-4 (still in use) with big differences in size, activity and water regime). It was established that 137 Cs and 90 Sr desorption from the R-17 bottom sediment reach constant values after 24 h, and the desorption degree is not dependant on pH but on ionic strength. Sequential extraction indicated that the main accumulation mechanism of 137 Cs is incorporation into the clay minerals. The maximum plutonium content was detected in the residual fraction of the R-17 bottom sediment, which could be associated with the effects of precipitation aging. In R-4, plutonium is equally distributed between residual and bound to organic matter fractions. The 241 Am is associated with carbonates in the R-17 bottom sediment and with organic matter in the R-4 bottom sediment and to lesser extent with iron-manganese oxides. The radionuclides are becoming less environmentally available with time since deposition., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

The specific activities of natural ( 210 Pb, 226 Ra, and 232 Th) and artificial ( 137 Cs, 239,240 Pu, and 241 Am) radionuclides in the sediments of two North Caucasus lakes were determined. The two lakes, Lake Khuko and Lake Donguz-Orun, differ in their sedimentation conditions. Based on the use of unsupported 210 Pb ex and both Chernobyl-derived and bomb-derived 137 Cs as chronological markers, it was established that the sedimentation rates in Lake Khuko over the past 55-60 y did not exceed 0.017 cm y -1 . Sedimentation rates in Lake Donguz-Orun were found to be more than an order of magnitude higher. In the latter case, the sedimentation rates for the period from 1986 to the present were over 1.5 times higher than they were for the period 1963-1986. The differences in sedimentation rates were due to differences in the rates of denudation of their respective catchment areas. The specific activities of artificial radionuclides ( 137 Cs, 2600 Bq kg - 1 ; 239,240 Pu, 162 Bq kg - 1 ; and 241 Am, 36 Bq kg - 1 ) and their ratios in the sediments of Lake Khuko show that their deposition was mainly due to global stratospheric fallout of technogenic radionuclides associated with nuclear bomb testing during 1954-1963-rather than fallout from the Chernobyl accident. Several factors, including the mode of precipitation, features of the surface runoff, and location of Lake Khuko, were responsible for the accumulation of artificial radionuclides., Competing Interests: Declaration of competinh interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

In April and August 2015, a massive fire occurred in the Chernobyl Exclusion zone. The fire spread to neighboring areas due to the prevailing strong winds. In this paper, we analyze the peat fires as a unique source of radioactive contamination. After an expedition directly to the peat fire site (the evacuation zone of the Bryansk region), we collected a number of aerosol samples. We came to the conclusion that peat fires cannot be the reason for radioactive particle transport in the Bryansk region as well as in the Chernobyl evacuation zone. During the peat fire, radioactive contamination was not transferred by aerosols beyond 500 m. The 137 Cs concentration in the aerosol filters varied between 0.55 and 0.64 Bq/m 3 , and that at the same distance from the fire seat and peat edge was 4.4∙10 -3 Bq/m 3 ; the activity values in the peat bog and in the nearest inhabited locality did not exceed the background values. Strontium-90 was not found in aerosol samples. The soil-to-air transport rate of 137 Cs was 2.7∙10 -6 . After the Chernobyl accident, the majority of the 137 Cs was incorporated into the structure of clay minerals, and these did not change during the peat fire. The mobility of 137 Cs in the flight peat material particles was established. To confirm the territory status of the evacuation zone, we also collected some food samples. Berries and mushrooms consumed at the assumed rate for dose estimation would result in doses that exceed the public dose limit by approximately a factor of five., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)