Chronic radiation exposure as an ecological factor: Hypermethylation and genetic differentiation in irradiated Scots pine populations.

Genetic and epigenetic changes were investigated in chronically irradiated Scots pine (Pinus sylvestris L.) populations from territories that were heavily contaminated by radionuclides as result of the Chernobyl Nuclear Power Plant accident. In comparison to the reference site, the genetic diversity revealed by electrophoretic mobility of AFLPs was found to be significantly higher at the radioactively contaminated areas. In addition, the genome of pine trees was significantly hypermethylated at 4 of the 7 affected sites.

[Influence of γ-Irradiated Seeds on the Enzyme Activity in Barley Seedlings].

Influence of γ-irradiation of barley seeds (Nur variety) at the doses of 8-50 Gy on catalase, pyruvate kinase, glucose-6-phosphate dehydrogenase, and guaiacol peroxidase activities was studied in the seedlings on the 3, 5 and 7 days after germination. It has been shown that activities of the studied enzymes increase in the dose range that causes the growth stimulation in the seedlings (16-20 Gy).

[Assessment of Cyto- and Genotoxicity of Underground Waters from the Far Eastern Center on Radioactive Waste Treatment Site].

This study has been completed in the frames of activities on the environment assessment in the vicinity of the Far Eastern center (FEC) on radioactive waste treatment (a branch of Fokino, Sysoev Bay). Underground waters collected at the FEC technical site were surveyed both with instrumental techniques and bioassays. Concentrations of some chemicals (ranged to the third hazard category) in the samples collected are over the permitted limits. Activities of 137Cs and 90Sr in waters amount up to 3.8 and 16.2 Bq/l, correspondingly. The integral pollution index is over 1 in all the samples and could amount up to 165. The Allium-test application allows the detection of the sample points where underground waters have an enhanced mutagenic potential. Dependencies between biological effects and pollution levels are analyzed. The findings obtained could be used for the monitoring optimized and decision making on rehabilitation measures to decrease negative influence of the enterprise on the environment.

Characterization of biocenoses in the storage reservoirs of liquid radioactive wastes of Mayak PA. Initial descriptive report.

As a result of operation of the Mayak Production Association (Mayak PA), Chelyabinsk Oblast, Russia, an enterprise for production and separation of weapon-grade plutonium in the Soviet Union, ecosystems of a number of water bodies have been radioactively contaminated. The article presents information about the current state of ecosystems of 6 special industrial storage reservoirs of liquid radioactive waste from Mayak PA: reservoirs R-3, R-4, R-9, R-10, R-11 and R-17. At present the excess of the radionuclide content in the water of the studied reservoirs and comparison reservoirs (Shershnyovskoye and Beloyarskoye reservoirs) is 9 orders of magnitude for (90)Sr and (137)Cs, and 6 orders of magnitude for alpha-emitting radionuclides. According to the level of radioactive contamination, the reservoirs of the Mayak PA could be arranged in the ascending order as follows: R-11, R-10, R-4, R-3, R-17 and R-9. In 2007-2012 research of the status of the biocenoses of these reservoirs in terms of phytoplankton, zooplankton, bacterioplankton, zoobenthos, aquatic plants, ichthyofauna, avifauna parameters was performed. The conducted studies revealed decrease in species diversity in reservoirs with the highest levels of radioactive and chemical contamination. This article is an initial descriptive report on the status of the biocenoses of radioactively contaminated reservoirs of the Mayak PA, and is the first article in a series of publications devoted to the studies of the reaction of biocenoses of the fresh-water reservoirs of the Mayak PA to a combination of natural and man-made factors, including chronic radiation exposure.

[Polymorphism of Glucose-6-phosphate Dehydrogenase in the Chronically Irradiated Scots Pine Populations].

Polymorphism of glucose-6-phosphate dehydrogenase enzyme was studied in the Scots pine populations growing in the sites of Bryansk region which were radioactively contaminated as a result of the Chernobyl accident. It was revealed that the frequency of mutations in isozyme loci increased along with the level of a dose rate (7-130 mGy/year) in the sites under the study. Significant changes in the activity of this enzyme did not depend on the level of radiation exposure.

[Modification of Barley Development at Early Stages after Exposure of Seeds to γ-Irradiation].

The reaction of barley seeds (Nur and Grace varieties) to γ-irradiation in the dose range of 2-50 Gy was studied. The length and weight of a root, the length of a seedling and germination rate were investigated. The dose range in which we observed stimulation of plant development was evaluated. It was shown that the increase of root and seedling sizes after irradiation of seeds at stimulating doses is associated with the rise in the developmental speed, rather than with their earlier germination. Also the effects of a dose rate, a quality of seeds, humidity and a period of storage on the manifestation of radiation exposure were studied.

[Specific Features of Scots Pine Seeds Formation in the Remote Period after the Chernobyl NPP Accident].

The results of long-term (2007-2011) observations on the quality of seed progeny in Scots pine populations inhabiting the sites within the Bryansk region contaminated as a result of the Chernobyl NPP accident are presented. Formed under the chronic exposure seeds are characterized by a high interannual variability, which is largely determined by weather conditions.

[V.I.Vernadskii's theory of the biosphere and modern problems of radioecology].

The importance of Vernadsky's scientific heritage for the present stage of science development was substantiated. His role in the formation of radioecology as an independent scientific discipline was emphasized. The ecological consequences of an anthropogenic increase of the radiation background and the prospects of nuclear energy development were considered.

[Antioxidant enzyme activities in Scots pine populations growing under chronic radiation exposure].

The activities of superoxide dismutase, catalase and peroxidase in Scots pine populations growing in the contaminated areas of Bryansk region were investigated. The dose rate at the experimental sites ranged from 7 to 130 mGy/year. It has been identified that the activities ofantioxidant enzymes do not depend on the radiation factor under these dose rates. These doses were found to be insufficient for forming significant physiological effects.

[Evaluation of the partial contribution of naturally occurring radionuclides and nonradioactive chemically toxic elements in formation of biological effects within the Vicia cracca population inhabiting the area contaminated with uranium-radium production wastes in the Komi Republic].

The site contaminated with uranium-radium production wastes in the Komi Republic was studied. The activity concentration of naturally occurring radionuclides (226Ra, 228Th, 238U, 230Th, 232Th, 210Po, and 210Pb), as well as concentrations of nonradioactive chemically toxic elements (Pb, Zn, Cu, As, V, Mo, Sr, Y, and Ba) in the soil samples from the experimental site is 10-183 times higher than reference levels. A chronic exposure to alpha-emitters and nonradioactive chemically toxic elements causes adverse effects in tufted vetch (Vacia cracca L.) both at the cellular (aberration of chromosomes) and population (decrease in the reproductive ability) levels. Radionuclides are the main contributors to the decrease in the reproductive capacity and an increase in the level of the cytogenetic damage in root tip cells of tufted vetch seedlings. As and Pb significantly influence the reproductive capacity of plants. Sr, Zn, Y and P modify the biological effects caused by exposure to radionuclides. Moreover, P and Zn reduce the adverse effects of radionuclides; however, Sr and Y enhance these effects.

[Assessment of cyto- and genotoxicity of natural waters in the vicinity of radioactive waste storage facility using Allium-test].

Efficacy of bioassays of "aberrant cells frequency" and "proliferative activity" in root meristem of Allium cepa L. is studied in the present work for a cyto- and genotoxicity assessment of natural waters contaminated with 90Sr and heavy metals in the vicinity of the radioactive waste storage facility in Obninsk, Kaluga region. The Allium-test is shown to be applicable for the diagnostics of environmental media at their combined pollution with chemical and radioactive substances. The analysis of aberration spectrum shows an important role of chemical toxicants in the mutagenic potential of waters collected in the vicinity of the radioactive waste storage facility. Biological effects are not always possible to explain from the knowledge on water contamination levels, which shows limitations of physical-chemical monitoring in providing the adequate risk assessment for human and biota from multicomponent environmental impacts.

[An assessment of relative contribution of DNA reparation and glutathione-dependent pathway of detoxification in response of Chlorella algae to uranium].

Toxicity of 238U (as uranyl nitrate) in the range of 0.04-84 micromol/L for Chlorella (Chlorella vulgaris Beijerink) was investigated. The best approximation for relationship between the toxic effect in Chlorella and 238U Concentrations is observed using the hormetic Brain-Cousens model. A significant increase in Chlorella biomass, estimated as the optical density of suspension, as well as the level of fluorescence of chlorophyll was observed in the range of 17-29 micromol/L with the maximum at a 23 micromol/L. It was found that 38 micromol/L of 238U induced a significant toxic effect; while at 53 micromol/L inhibition of Chlorella biomass by 50% was observed. According to our observations, the toxic effect of low concentrations of 238U was increased in the presence of 0.02 micromol/L caffeine (used as inhibitor of DNA repair processes) or DL-buthionine-(S, R)-sulfoximine (used as a selective inhibitor of the key glutathione biosynthetic pathway).

[Database on effects of ionizing radiation in plants: experience and application perspectives].

Information available in the literature about the effects of ionizing radiation on flora and fauna species is a basis for the development of a methodology for radiation protection of the environment. International experience in the creation of databases of radiation effects in biota is discussed. Here presented and described are the structure and the content of the database "Biological effects of radiation in plants" which at present contains more than 5000 datasets and about 19000 "radiation impact-biological effect" pairs of data. Experience and perspectives of applying the database management systems in radiobiology and radiation protection are discussed.

[Polymorphism of superoxiddismutase in chronically irradiated Scots pine populations].

Polymorphism ofsuperoxidedismutase in Scots pine populations from the Bryansk region radioactively contaminated as a result of the Chernobyl accident was studied. The frequency of mutations in the isozyme loci, the effective number of alleles, intrapopulation diversity, as well as the frequency of rare morphs were significantly increased along with the level of radioactive contamination. Changes in the genetic makeup of the populations under study were due to the increased frequency of rare alleles.

[Radiation risk assessment for plant reference species (Pinus sylvestris and Vicia cracca) from the area of radium production waste storage].

The risk of an enhanced level of radionuclides of the uranium and thorium decay series in the environment for reference plant species (Pinus sylvestris and Vicia cracca) was assessed. 238U, 230Th, 226Ra, 210Po, 232Th and 228Th concentration factors for plants were found to be lower than one. The aboveground parts of Vicia cracca sampled from the area of the radium production waste storage mainly accumulated 22Ra, Pinus sylvestris branches--210Pb, 226Ra and 210Po. LOEDR calculated for the chromosome aberration frequency in both plant studies was 17-71 microGy/h. LOERD values for the reproductive capacity decrease in P. sylvestris and V. cracca were 17-71 microGy/h and 116-258 microGy/h, correspondingly. EDR10 for the chromosome aberration frequency in P. sylvestris and V. cracca were 148 and 347 microGy/h, that is, correspondingly, 255 and 708 times higher that background values. EDR10 for the plant reproductive capacity was 11-34 microGy/h, which 19-69 times increases the background values.

[Regularities of lateral distribution of uranium and thorium decay series radionuclides in the anthropogenically changed soils from the area of radium production waste storage].

Cartographical investigations of the territory of radium production waste storage has shown some changes in lateral differentiation of radionuclides of uranium and thorium decay series to occur during 27 years (1981-2008). Those changes are caused mostly by flat denudation typical for fluvial terrace. At present radionuclides of uranium and thorium decay series are concentrated mostly in flood lands and relief depressions. At the same time, decrease in the radionuclide activity concentration in 0-20 cm soil layer is observed with changes in lateral distribution. Total stocks of 226Ra, 210Pb and 210Po within catena soils studied in the northern and southern parts of the waste storage decreased 3-6 times, 238U - 2 times, and did not significantly change in case of 232Th during 27 years. Nonetheless, most of the samples studied are referred to radioactive waste both according to Russian standards (SPORO-2002) and IAEA safety norms (IAEA, 2004).

Effects of chronic exposure in populations of Koeleria gracilis Pers. from the Semipalatinsk nuclear test site, Kazakhstan.

Morphological and cytogenetic abnormalities were examined in crested hairgrass (Koeleria gracilis Pers.) populations inhabiting the Semipalatinsk nuclear test site (STS), Kazakhstan. Sampling of biological material and soil was carried out during 3 years (2005-2007) at 4 sites within the STS. Activity concentrations of 10 radionuclides and 8 heavy metals content in soils were measured. Doses absorbed by plants were estimated and varied, depending on the plot, from 4 up to 265 mGy/y. The frequency of cytogenetic alterations in apical meristem of germinated seeds from the highly contaminated plot significantly exceeded the level observed at other plots with lower levels of radioactive contamination during all three years of the study. A significant excess of chromosome aberrations, typical for radiation exposure, as well as a dependence of the frequency of these types of mutations on dose absorbed by plants were revealed. The results indicate the role radioactive contamination plays in the occurrence of cytogenetic effects. However, no radiation-dependent morphological alterations were detected in the progeny of the exposed populations. Given that the crested hairgrass populations have occupied the radioactively contaminated plots for some 50 years, adaptation to the radiation stress was not evident. The findings obtained were in agreement with the benchmark values proposed in the FASSET and ERICA projects to restrict radiation impacts on biota.

[Assessment of soil degradation in regions of nuclear power explosions at Semipalatinsk Nuclear Test Site].

Degree of the soil cover degradation at the "Balapan" and "Experimental field" test sites was assessed based on Allium-test of soil toxicity results and international guidelines on radioactive restriction of solid materials (IAEA, 2004) and environment (Smith, 2005). Soil cover degradation maps of large-scale (1 : 25000) were made. The main part of the area mapped belongs to high-contaminated toxic degraded soil. A relationship between the soil toxicity and the total radionuclide activity concentrations was found to be described by power functions. When the calculated value (equal to 413-415 Bq/kg of air dry soil) increases, the soil becomes toxic for plants. This value is 7.8 times higher than the maximal value for background territories (53 Bq/kg) surrounding SNTS. Russian sanitary and hygienic guidelines (Radiation safety norms, 2009; Sanitary regulations of radioactive waste management, 2003) underestimate the degree of soil radioactive contamination for plants.

[Dynamics and ecological-genetic variability of cytogenetic disturbances in Scots pine populations experiencing technogenic impact].

Scots pine (Pinus sylvestris L.) populations in the vicinity of nuclear industry facilities were monitored. Aberrant cells occurrence in root meristem of germinated seeds from the impacted pine populations was found to be significantly above the reference level during all six years of observations. In the reference population, changes of cytogenetic disturbances with time appeared to be cyclic while in the impacted populations, technogenic stress was strong enough to destroy the natural regularities. The increase in cytogenetic disturbances was accompanied by growth of fluctuations magnitude; deviations of basic oscillation parameters from the reference values rose along with technogenic impact level. Variability in cytogenetic response increased under technogenic stress. Inter-family component of variability predominated, though its contribution slightly decreased in impacted populations. A tendency for destabilization of a repetition coefficient dynamics was found under technogenic impact. A portion of the seeds was exposed to 15 Gy of gamma-rays, and higher radio-resistance in the impacted populations was observed. In the reference population, a family-related analysis of cytogenetic variability components after acute y-exposure revealed significant contributions of "family" and "germination conditions" factors as well as their interactions. On the contrary, in populations existing under chronic stress, considerable modifications in the structure of ecological-genetic variability were found, their degree increasing with technogenic impact severity.

[Biological effects of chronic radiation exposure on plant populations].

The findings from long-term field studies on biological effects in plant populations inhabiting radioactively contaminated territories contrast in levels and compositions of dose-forming radionuclides are presented. Plant populations developing under radioactive impact show enhanced frequencies of gene and chromosome mutations, and their reproductive potential is inferior to reference populations. Even relatively low levels of technogenic impact are able to increase genetic diversity and destroy regularities inherent for intact populations. Chronic radiation exposure from a certain level appears to be an ecological factor changing genetic structure of wild populations. Data presented indicate the presence of adaptation processes in plant populations in territories with technogenic impact. Under ecological stress, there are selection processes for resistance improvement in plant populations. But an appearance and rate of this process can essentially differ in dependence on radioecological conditions.