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Hypothesis: Because reactive oxygen species are involved in the regulation of biological rhythms, we hypothesized that intra-annual variability of seed progeny quality at low doses of ionizing radiation (LDIRs) would differ from that of background plants., Materials and Methods: We conducted 12 consecutive experiments using the roll culture method by germinating seeds (monthly for 3 weeks) of six herbaceous plant species ( Bromus inermis , Geum aleppicum , Plantago major , Rumex confertus , Silene latifolia , and Taraxacum officinale ) growing under conditions of chronic radiation in the East Ural Radioactive Trace (EURT). We assessed physiological (seed viability and abnormality frequency) and biochemical (low-molecular-weight antioxidants, LMWAs) parameters of seedlings., Results: Total absorbed dose rates of maternal plants (TADR plants ) and seed embryos (TADR seeds ) in the EURT exceeded background levels by 1-3 and 1-2 orders of magnitude, respectively. Nonlinear dependencies on TADR were mainly characteristic of physiological and biochemical parameters. For most populations of the studied species ( B. inermis , G. aleppicum , R. confertus , and S. latifolia ), seedling survival and root length decreased in the autumn-winter period, while the frequency of abnormal seedlings increased. The content of LMWAs could be ranked as R. confertus  > B. inermis  > G. aleppicum  > S. latifolia , in good agreement with the presence of anthocyanin pigmentation in the plants. The lowest synthesis of antioxidants in seedlings was observed in winter. A high LMWA content promoted growth and reduced the frequency of abnormal seedlings., Conclusions: These results underscore a multistage nature of the impact of LDIRs on intra-annual biological rhythms in plants. High heterogeneity in reference group 'wild grasses' and diversity of their radiobiological effects should help to develop methods of radiation protection for natural ecosystems and facilitate approaches used by the International Commission on Radiological Protection.HighlightsAbsorbed dose rates for six plant species in the East Ural Radioactive Trace (EURT) area range from 0.11 to 73.89 µGy h -s (plants) and 0.11 to 6.88 µGy h -s (seed embryos).Intra-annual rhythms of physiological and biochemical parameters in the EURT zone differ from those in background seedlings.Plants in the EURT area exhibit a wide range of trait variability, asynchrony of the manifestation of the effects, nonlinear dose-response relations, and hormesis.A high content of low-molecular-weight antioxidants (LMWAs) is associated with low frequency of developmental abnormalities and high viability of seed progeny.

The effects of low-dose radiation that are observed in plant populations in radioactively contaminated areas are variable. One of the reasons is the influence of fluctuating weather conditions and the interaction of radiation with weather factors. This article summarizes results of 12-year research on the viability and radioresistance of greater plantain ( Plantago major L.) seed progeny growing in the East Ural Radioactive Trace (EURT) zone and in control (nonradioactive) areas, with consideration of weather conditions' variability. The EURT was formed by the Kyshtym accident, which occurred in 1957 at the Mayak Production Association. Absorbed dose rates of P. major parental plants in the pollution gradient were 14.5-165.9 μGy h -1 , which correspond to a low-dose range. Seed progeny quality was evaluated as seed weight, the survival rate, and root length of 21-day seedlings. Interannual variability in the studied parameters was high, and their ranges overlapped between EURT groups of seeds and control groups in most cases. The number of significant correlations between the parameters of seed quality and weather conditions was higher in EURT groups than in control populations. In the control groups of seeds, 88.9% of correlations were negative, whereas in the EURT groups, 78.5% were positive.

On 29 September 1957, the so-called Kyshtym accident occurred at the USSR's first nuclear weapons plutonium production facility. The East Ural State Reserve (EUSR) was established in the most contaminated part of the radioactive trace, where a substantial part of the forests died in the first years after the accident. The purpose of our study was to evaluate the natural restoration of forests and to verify and update the taxonomic parameters that characterize the current state of forest stands in the EUSR. Data on the forest inventory of 2003 and results of our research of 2020 performed by the same methods on 84 randomly selected sites served as the basis for this work. We developed models to approximate growth dynamics and then updated the 2003 taxation-related forest data for the entire EUSR. According to these models and ArcGIS construction of new data, forest-covered lands make up 55.8% of the whole EUSR territory. The proportion of birch forests in the forest-covered lands is 91.9%; 60.7% of wood resources are located in mature and overmature (81-120-year-old) birch forests. The total timber stock in the EUSR is > 1385 thousand tons. It was revealed that ~ 4.2 × 10 14  Bq of 90 Sr is situated within the EUSR. The main stock of 90 Sr is found in soils. The 90 Sr stock in the stands is ~ 1.6-3.0% of the total content in the forests. Only a part of the EUSR forest stands can be used for practical applications., (© 2023. The Author(s), under exclusive licence to Springer Nature Switzerland AG.)

Hypothesis: The differences in viability, root length, and pro/antioxidant features of Plantago major seedlings identified in seed progeny formed in areas of radioactive and chemical contamination can persist in subsequent generations after the elimination of the stress., Materials and Methods: The seed mixtures of F1 generation were collected from P. major natural populations (P plants) growing for a long time in the East Ural Radioactive Trace, the Karabash Copper Smelter zone, and background area. The seeds of F2 generation were obtained from F1 generation plants grown on experimental plots with 'clean' agricultural background; F3 generation was grown from F2 generation on the same plots. The viability of seed progeny was estimated by survival rate and root length. Pro/antioxidant features were determined spectrophotometrically by malondialdehyde content, superoxide dismutase and catalase activities, and total content of low molecular weight antioxidants in seedlings., Results and Conclusions: The hypothesis about the persistence of effects from chronic exposure to ionizing radiation and chemical contamination in the generations' sequence of P. major after the removal of stress was confirmed only partially. The data obtained indicated that changes in the prooxidant and antioxidant features of plants in response to low doses of ionizing radiation can persist for at least in two generations after the stress removal. In the case of long-term exposure to chemical contaminants, we observed the persistence of the effect in a succession of generations only on the morphological indicator of root length.

This study was conducted in 2010-2020 at the head of the East Ural Radioactive Trace (EURT), which was formed in 1957 as a result of the Kyshtym accident at the Mayak Production Association. The main contaminant in this zone is the long-lived radionuclide Strontium-90 (90Sr). Secondary forests dominated by silver birch (Betula pendula) occupy 45% of the EURT area. Concentration of 90Sr in birch leaves and small branches was higher than that in the trunks. The 90Sr content in birch sapwood varied slightly in the radial direction and did not depend on tree age. This was due to the dynamic equilibrium of the migration processes responsible for the accumulation and horizontal transfer of 90Sr. The 90Sr concentration increases in false heartwood, which is formed as a result of the secondary metabolism of dying parenchyma in the inner part of sapwood and is characterised by a high content of ash elements. The concentration of radionuclides in the aboveground organs of birch increased and the aggregated transfer factors (Tag) decreased with an increase in the soil contamination density, in accordance with the power function. The reasons for these patterns are also discussed., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

The variability of nine microsatellite loci was studied for Plantago major L. populations from radioactive (East-Ural Radioactive Trace, EURT) and chemical (Karabash Copper Smelter, KCS) contaminated areas (Urals, Russia). The absorbed dose rates in the EURT area were 178-1455 times higher than background, and the indices of the total toxic load in the KCS area were 13-42 times higher than background values. In total, 65 alleles were identified in P. major populations, while the number of alleles per locus in the EURT and KCS samples was lower than in the background samples. The expected heterozygosity in all loci significantly exceeded the observed, indicating a high level of inbreeding. The largest number of rare alleles (11-21) was found in background samples, of which 3-7 alleles were private. In the technogenically disturbed zones, 8-11 rare alleles (1-2 private) were noted. The Bayesian analysis (K = 3) showed that no unique groups were found in any of the areas; descendants of all founders (pioneers) were represented in each population, but in different proportions. However, only 4.1% of the variability was distributed between local P. major populations (F ST  = 0.041) and 95.9% was concentrated within the samples. A pairwise comparison revealed genetic differentiation between all EURT samples. In the KCS area, there was no significant differentiation in pairs of samples that were at a distance of 3-4 km from each other. For samples from the KCS and background sites, the Mantel test showed a statistically significant relationship between geographical and genetic distances, therefore, the intensity of migration flows between these areas is high. For samples from the EURT and background areas, no such dependence was found. In both impact zones, P. major populations showed reduced genetic diversity. This article discusses the causes of this phenomenon., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

A nuclear accident occurred at the production association Mayak in the Urals in 1957. Approximately 74 PBq of radioactive substances were released into the environment, which resulted in the contamination of a vast area, named the East Ural Radioactive Trace (EURT). We have studied the current levels of contamination of soils and plants by 90 Sr in the head part of the EURT. The heterogeneity of soil contamination (concentrations and contamination densities) in the EURT zone was considered at three scales. 1) At the macro-level, the soil contamination by 90 Sr decreased by three orders of magnitude in the cross section of the zone. 2) At the meso-level, the variability of the soil contamination was estimated within several sectors, selected by the results of macro-scale mapping. 3) At the micro-level, differences in soil contamination between individual samples (0.01 m 2 ) selected at the site (1000 m 2 ) exceeded the one order of magnitude. The similarity of geometric mean (GM) values of the soil contamination was shown, based on the measurements of 3, 25 and 30 soil samples at the micro-level. In 57% of cases, the value of the GM obtained by 3 measurements differed by no >20% from the GM value by 25 measurements. In the most of cases, the differences in GM obtained by these two methods did not exceed 40%. Thus, in small sites it is possible to take only three soil samples to assess the level of soil contamination. We evaluated the absorption variability of 90 Sr for six species of herbaceous plants (Rumex confertus, Leonurus quinquelobatus, Arctium tomentosum, Urtica dioica, Lathyrus pratensis, Bromopsis inermis). The range of concentration ratios (CR wo-soil ) for 90 Sr was 0.003-0.49, and the diapason of aggregated transfer factors (T ag ) was 0.56-7.3. The 'plant species' factor determined about 55% of the total variability of CR wo-soil and T ag ., (Copyright © 2018 Elsevier B.V. All rights reserved.)

The evaluation of radiation exposure in 14 species of herbaceous plants from the East-Ural Radioactive Trace (EURT) zone was performed, using the ERICA Tool, v. 1.2. Recent (up to 2015) levels of radionuclide activity concentration were measured in soil and vegetative plant mass. 239,240 Pu content was used for the first time to estimate external dose rates for herbaceous plant species along the pollution gradient. In addition, a new approach to assessing the geometry of objects was adopted, including not only aboveground but also underground plant organs. This improved approach to the evaluation of radiation exposure confirms previous findings that herbaceous plant populations currently exist under low-level chronic exposure in the EURT area. This reassessment based on new data suggests a 48-977-fold increase in the total dose rate per plant organism at the most polluted site compared to background areas. The highest capacity for the transfer of 90 Sr and 137 Cs was observed in Taraxacum officinale and Plantago major. In these species, the total dose rate per plant exceeded 150 μGy h -1 due to 90 Sr +  137 Cs +  239,240 Pu radionuclide anthropogenic pollution in the EURT zone. All estimated total dose rates per plant were below the dose rate screening value of 400 μGy h -1 .

The contamination densities of soil-plant cover at certain locations within the Primorsky Krai, Sakhalin Island and Kamchatka Peninsula attributable to 90 Sr, 137 Cs and 239,240 Pu were 500-1390 Bq m -2 , 980-2300 Bq m -2 and 37-74 Bq m -2 , respectively. These values do not exceed average global background levels, typical for mid-latitudes of the Northern Hemisphere. The spatial distribution of radionuclides depends on the climatic conditions of the region. A positive dependence of the 90 Sr and 137 Cs contamination densities, as well as additional 137 Cs from NPP "Fukushima" in the soil, was determined based on the sum of annual atmospheric precipitation within the study areas. No trends in the spatial distribution of Pu isotopes were observed. The 137 Cs contribution from the "Fukushima" NPP constitutes 11-300 Bq m -2 in the Primorsky Krai, Sakhalin Island and at the Kamchatka peninsula, i.e., 1-22% of the total amount of radionuclides in the soil. The contribution of this radionuclide to the contamination of moss-lichen vegetation ranged from 7 to 42%., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Hypothesis: The multiple stressors, in different combinations, may impact differently upon seed quality, and low-level doses of radiation may enhance synergistic or antagonistic effects., Results: During 1991-2014 we investigated the quality of the dandelion (Taraxacum officinale s.l.) seed progeny growing under low-level radiation exposure at the East-Ural Radioactive Trace (EURT) area (result of the Kyshtym accident, Russia), and in plants from areas exposed to background radiation. The viability of the dandelion seed progeny was assessed according to chronic radiation exposure, accounting for the variability of weather conditions among years. Environmental factors (temperature, precipitation, and their ratio in different months) can modify the radiobiological effects. We found a wide range of possible responses to multiple stressors: inhibition, stimulation, and indifferent effects in different seasons., Conclusion: The intraspecific variability of the quality of dandelion seed progeny was greatly increased under conditions of low doses of chronic irradiation. Temperature was the most significant factor for seed progeny formation in the EURT zone, whereas the sums of precipitation and ratios of precipitation to temperature dominantly affected organisms from the background population.

The effect of radiation pollution on genetic variation in natural populations of Melandrium album was investigated at the head part of the East-Ural Radioactive Trace (EURT) and background areas. The highest genetic differentiation estimated using F ST was revealed between compared pairs of the background and impact samples in populations of M. album. The highest rate of polymorphism was observed at the closest to nuclear accident, Impact-1 site. The unique alleles (Mdh-3 104 , Pgi-2 106 , Lap 105 , Mdh-2 96 , and Dia 94 ) were discovered at the EURT. Individuals from chronically low-level irradiated sites were genetically closer than to plants from background sites using Nadhdh locus. The increase of the frequency of unique homozygous and heterozygous genotypes was identified in populations of M. album growing under chronic radiation exposure conditions. The largest contribution to the group of unique heterozygous genotypes at the EURT was made by three loci - Lap, Pgi-2, and Nadhdh; the main role in interpopulation differentiation of samples was made by the alleles Sod-2 115 , Skdh 100 , and Nadhdh 100 . Our results provide evidence for the correlation between the increase of genetic variation other than the «genetic erosion» and chronic radiation exposure factor in natural plant populations.

Investigations of the spatial and vertical distribution of 90Sr, 137Cs and 239, 240Pu in the soils of the Eastern Ural Radioactive Trace (EURT) and accumulation of these radionuclides by plants were carried out in 2003-2011. Investigations showed that the spatial distribution of the radionuclides with increasing distances from the epicenter of the accident is satisfactorily approximated by the exponential function. During the post-accidental period the essential amount of radionuclides is located in the 15-20 cm root layer of the soil. Uptake by plants of 90Sr is determined, first of all, by the level of the soil contamination. For 137Cs, reliable differences in its accumulation ability between representatives of the higher plants and lower ones are remained in the whole gradient of contamination.

We carried out a comparative study of seed progeny taken from the dandelion (Taraxacum officinale s.l.) coenopopulations exposed for a long time to radioactive or chemical contamination originated from the East-Ural radioactive trace zone (EURT) or Nizhniy Tagil metallurgical combine impact zone (NTMC), respectively. Coenopopulations from EURT, NTMC and background areas significantly differ from each other with respect to the qualitative and quantitative composition of allozyme phenes. An analysis of clonal diversity showed the uniqueness of all coenopopulations in terms of their phenogenetics. P-generation seed viability was found to decrease in a similar manner as all types of the industrial stress increased. Studies of F (1)-generation variability in radio- and metal resistance by family analysis showed that seed progeny from EURT impact zone possessed high viability that, however, was accompanied by development of latent injuries resulting in low resistance to additional man-caused impacts. In F (1)-generation originated from NTMC zone, high seed viability was combined with increased resistance to provocative heavy metal and radiation exposure. No significant differences in responses to 'habitual' and 'new' factors, i.e. pre-adaptation effect, were found in samples from the contaminated areas.

The contamination levels and spatial distribution of 90Sr and 137Cs in the soil cover of the Eastern Ural State Radioactive Reserve and neighboring areas have been studied. Situated in the Chelyabinsk region, the Reserve embraces the frontal part of the Eastern Urals Radioactive Trace. This Trace emerged in 1957 as a result of the nuclear accident at the Production Association "Mayak". In the studied areas, the content of radionuclides in soils decreases exponentially as the distance from the source of contamination increases. 90Sr received by the soil cover as a result of the accident in 1957 has remained the main contaminant of the Reserve central part (97% of the total contamination). Its contribution throughout western neighboring areas reduces up to 67%, which decreases the effect of 90Sr on the environment. Within eastern neighboring areas, soil is mainly contaminated by 137Cs received as a result of the wind disseminated dried sediments from the shores of Lake Karachay (1967) that was used for dumping high-level radioactive waste. Also observed was enrichment of forest litters with this radionuclide due to current atmospheric fallout.

Variation of 17 allozyme loci was examined in 530 Apodemus uralensis individuals caught in the Ural region in 2005 through 2007. In the populations examined, the mean value of the population genetic differentiation index F(ST) constituted 0.169. It was demonstrated that F(ST) values for the samples obtained from the 1-km2 plot in different years, as well as for the samples trapped at a distance from 0.3 to 5 km during one year, could be remarkably higher than the mean value, pointing to their high, statistically significant differentiation. It seems likely that this differentiation was caused by spatial population subdivision, associated with the mice migrations, temporal change of the population structure, and the gene drift. In A. uralensis, inhabiting the zone of East Ural radioactive trace, no differences in the allozyme sets and their frequencies were observed.

A comparative research of dandelion seed progeny from the coenopopulations growing for a long time in a gradient of radioactive (zone of the East-Ural radioactive trace--EURT) or chemical (zone exposure Nizhny Tagil Metallurgical Plant--NTMP) pollution was carried out. It was revealed that the viability of seeds declined similarly in gradient of the man-caused stress regardless of its nature. Dandelion coenopopulations from the EURT zone, NTMP and the background area significantly differed in the qualitative and quantitative allozyme specifications. The analysis of clonal diversity revealed phenogenetic uniqueness of all coenopopulations. Study of F1-generation metal and radio resistance showed that the seed progeny from the impact EURT zone possessed a high viability but had hidden damage that led to a low resistance to additional man-caused influences. High viability of the seeds in the F1-generation from the NTMP zone combined with increased resistance to the provocative effects of radiation and heavy metals. Significant differences in responses to the "habitual" and "n ew" factors of influence, i.e. effect of pre-adaptation in samples from EURT and NTMP zones were not found.

It was shown that along the Eastern Ural Radioactive Trace central axis, about 100 km in length, decrease of the (90)Sr and (137)Cs deposition densities in soil samples may be described as an exponential function. At the western and eastern periphery of the trace, (90)Sr contents in soils approached to the background level due to global fallout. (90)Sr and (137)Cs concentrations in seeds of some herbaceous plants have been determined. The radionuclide concentrations and the resulting dose loads upon plant seeds showed an excess over the background level of about two or three orders of magnitude., (Published by Elsevier Ltd.)

In the Eastern Ural Radioactive Trace, concentrations of 90Sr, the main contaminant, in the upper topsoil was estimated to be 40-17000 times over the global level. The density of contamination decreased with the distance from the accident plot according to exponential law. The resulting doze loads shown an excess over the background level of about 1-3 orders of magnitude. Vegetation in the head part of the EURT is represented with synanthropic and seminatural communities undergoing different phases of degradations and recovery successions. Phytocenosis degradation is caused by the failures during the accident, subsequent reinstatement and restoration activities and also by the initial anthropogenic load. The ecological and genetic effects of permanent ionizing radiation on plants are evident from a wider spectrum of variability for all indicators of the living ability of seed posterity and their increased mutability. The effect of radioadaptation, i.e. increased the resistance to the additional irradiation, in the EURT plants was not found.

The diversification of rare and unique morphs of some ferment systems and the clonal structure of dandelion coenopopulations, growing in radioactive contaminated drained watershed and flood-land ecosystems in the Ural region was studied. Drained watershed and flood-land dandelion coenopopulations significantly differed in the number of rare and of unique morphs and in the clonal structure. In the gradient of contamination in the drained watershed coenopopulations (zone of East-Urals radioactive trace) the share of rare morphs in most ferments systems increased, while the number of clones decreased. In two flood-land coenopopulations of the Techa River essential differences in the enzyme structure were observed, but these peculiarities were not connected with the level of radioactive contamination.

Levels of soil contamination with 90Sr and 137Cs radionuclides on the plots within the zone of Eastern-Ural radioactive trace exceed values of the global level 4-240 times. We have carried out allozyme analysis of apomict species Taraxacum officinale s.l. from this zone. Zimogrammes were interpreted as allozyme phenotypes. In condition of chronic irradiation the plants had increased phenogenetic variability of majority enzymes systems and high frequency of rare morphs. Thus, in plant coenopopoulations situated in radioactive-polluted zone, genomic recombination processes show higher intensity. High enzymatic variability provides the material for natural selection and increase the adaptive potential of coenopopulations.

The Techa river was contaminated in 1949-1956 from the nuclear enterprise "Mayak". The investigations were carried out in flood plain of the Techa river in 1992-2001. 90Sr and 137Cs stores were calculated in the soil-vegetation cover. There is uneven character of the spatial radionuclides contamination of the investigated area. The store with 90Sr changes from 25 to 930 kBq/m2 (0.7-25.0 Ci/km2) and that with 137Cs--from 30 to 1700 kBq/m2 (0.8-46.0 Ci/km2). In the preriver-bed soils the ratio 90Sr/137Cs increases with further from discharge point. Individual effective dose was calculated for the Brodocalmak population. 90Sr was revealed in the flood plain soils of the Iset river. The contribution of the contaminated Techa river and its flood plains soils accounted for as by incorporated radionuclides as background gamma-radiation does not exceed 0.13-0.17 mSv/yr if the contaminated Techa river utilization is limited. In other case the contribution of the contaminated Techa river increases to 1.6-3.0 mSv/yr. These values exceed international safety norms.

Dandelion seeds were singly exposed to gamma-rays in a wide range of damaging doses. It was studied how the exposure influenced viability, mutability and radiosensitivity of seed descendants in a sequential turn of generations F1-F5. Non-lethal damages to genome, replicated in a sequence of generations, alongside with other effects, were found. Phenotypically the descendants showed the increasing loss of acrospires, the augmentation of abnormal shapes percentage in the sampling, the extension of span of variability of morphological features, the ambiguity of reactions to additional radiation impact. In the fifth generation the linear dependence of the effects on the doses received by the precursors disappeared.

Radioecological studies carried out in a joint co-operation between Russian, Ukrainian and Danish Laboratories are reported. The environmental impact of routine, discharges as well as accidental events, notably the Kyshtym accident in 1957 and the Karachay wind dispersion in 1968 have been studied. From measurements and based on model assumptions it has been estimated that the Ob river system outside Mayak, i.e. first of all the Techa and Iset rivers and their floodplains contain 0.1 PBq 90Sr, 0.3 PBq 137Cs and 0.8 TBq 239, 240Pu. The uncertainty of these estimates is a factor of 3-4. The present contamination from the Kyshtym accident outside the Mayak area is calculated to 0.1-0.5 PBq 90Sr and from the Karachay incident the contamination is 0.05-0.1 Bq 137Cs. The environmental contaminations with Pu from these two events are in the order of 1 TBq. The occurrence of 99Tc, 129I and 237Np in highly contaminated Techa river sediments collected outside Mayak is for the first time reported.

The Techa River in the Urals was contaminated with high-level radioactive waste from the MAJAK nuclear installation around 1950. The total discharge to the river amounted to 100 PBq with 90Sr and 137Cs contributing approximately 10 PBq each. This study has shown that the river presently contains approximately 0.3 TBq 90Sr, > 6 TBq 137Cs, and approximately 8 GBq 239,240Pu. The estimates were made for the part of the river starting 50 km from the point of discharge and ending 240 km downstream at the confluence with the Iset River. Radioactivity was measured only in the upper 0.10-m sediments layer. The external dose rates from the contamination range from 0.1-30 microGy h-1. The activity concentrations decrease exponentially or by power functions with distance.