Heterogeneity of soil contamination by 90Sr and its absorption by herbaceous plants in the East Ural Radioactive Trace area.

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 90Sr 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 90Sr 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 m2) selected at the site (1000 m2) 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 90Sr for six species of herbaceous plants (Rumex confertus, Leonurus quinquelobatus, Arctium tomentosum, Urtica dioica, Lathyrus pratensis, Bromopsis inermis). The range of concentration ratios (CRwo-soil) for 90Sr was 0.003-0.49, and the diapason of aggregated transfer factors (Tag) was 0.56-7.3. The 'plant species' factor determined about 55% of the total variability of CRwo-soil and Tag.

Radioactive contamination of the soil-plant cover at certain locations of Primorsky Krai, Sakhalin Island and Kamchatka Peninsula: Assessment of the Fukushima fallout.

The contamination densities of soil-plant cover at certain locations within the Primorsky Krai, Sakhalin Island and Kamchatka Peninsula attributable to 90Sr, 137Cs and 239,240Pu 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 90Sr and 137Cs contamination densities, as well as additional 137Cs 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 137Cs 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%.

[Man-made radionuclides and their accumulation by plants of different taxonomic groups from the soils of the eastern ural radioactive trace].

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.

[Radioecological investigation of the soil cover of eastern Urals State radioactive reserve and neighboring 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.

[Allozyme variation in pygmy wood mouse Apodemus uralensis (Rodenita, Muridae) in the Ural region].

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.

[Remote effects in plant populations from zones of radiation and chemical pollution].

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.

Radionuclides in terrestrial ecosystems of the zone of Kyshtym accident in the Urals.

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.

[The impacts of permanent irradiation on the flora of the eastern ural radioactive trace].

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 clonal structure of dandelion coenopopulations under conditions of radioactive contamination in the Urals].

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.

[Variability of enzyme systems in the coenopopulation of Taraxacum officinale s.l. from the zone of East-Ural- radioactive trace]. / Izmenchivost' fermentnykh sistem v tsenopopuliatsiiakh oduvanchika lekarstvennogo iz zony vostochno-ural'skogo radioaktivnogo sleda.

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.

[Radioecological situation at the villages of the Techa river]. / Radioékologiceskiaia situatsiia v raionakh naselennykh punktov beregovoi zony r. Techna.

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.

Environmental radioactivity in the South Urals 1990-1997. An international study supported by INTAS, EC and national funding.

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.

[Remote effect of irradiation on a heterogenesis of apomictic plants]. / Otdalennye posledstviia deistviia radiatsii v chrede pokolenii u rastenii-apomiktov.

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.

Radioactive contamination of the Techa River, the Urals.

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.