137Cs and 90Sr distribution peculiarities in soil and accumulation by pine tree wood and bark depending on edaphotops

The range of researches was made on 137Cs and 90Sr distribution regularities in pine tree plantations depending on different edaphic conditions. It is shown that total radionuclide amount in the forest litter depends on its thickness and is thought to be 10 to 70% for 137Cs and 20 to 60% for 90Sr. When soil fertility come increases from trophotop "A" to "C", 137Cs and 90Sr transfer factors for wood reduce. Soil humidity increase for each grade of trophic net results in increase of 137Cs transfer factors to wood and decrease for 90Sr. Total activity of 37Cs and 90Sr in pine wood plantation depends on plantation productivity and radionuclide transfer factors depending on different plantation conditions. In the most prevailing edaphotops pine wood accumulates 1-3% of 137Cs and 6-11% of 90Sr from total activity of radionuclides in biogeocenosis.     

137Cs and 90Sr accumulation in birch wood (Betula pendula Roth.) growing in regions with different soil conditions

The studies of 137Cs and 90Sr accumulation characteristics by birch wood (Betula pendula Roth.) growing in different edaphic conditions. Were conducted was stated that the increase in soil fertility from trophotops A to D results in 5-fold 137Cs transfer factor decrease and 2-fold decrease of 90Sr. Soil humidity increase for each grade of trophic net results happens the increase of 137Cs transfer factors to wood and decrease for 90Sr. Total activity of 37Cs and 90Sr in birch wood plantation depends on plantation productivity and on radionuclide transfer factors depending on different plantation conditions. In the most prevailing edaphotops (B2, B3, C2 and C3) birch wood accumulates 0.6-1.2% of 137Cs and 13-19% of 90Sr from total activity of radionuclides in biogeocenosis.     

The estimation of 90Sr and 137Cs excretion parameters from the organism of wild and laboratory small mammals in vivo, after natural contamination of them in the Chernobyl zone

In the course of laboratory experiment, parameters of 90Sr and 137Cs excretion were estimated in individuals of bank vole Clethrionomys glareolus, captured at one of the most contaminated sites of the Chernobyl zone. The animals were kept under laboratory conditions using "clean" feed during 50 days. The similar investigation was carried out with laboratory mice Mus musculus (Big Blue line) during a longer period (184 days). The measurements of 90Sr content in the animals' body were in vivo carried out, using a specially designed beta-spectrometer with appropriate software, and 137Cs one--by the gamma-spectrometer. During the experiment, the animals had lost less 0.4% of activity due to physical decay of radionuclides. The organism was depurated mainly through biological excretion. In accordance with parameters of one-component exponential decay equation, 99.3% of 137Cs initial content in vole was excreted with half-life period of 2.18 days, and mice--4.4 days (99%). 90Sr excretion had longer half-life period: 11.7 days (56%) in voles, and 49.9 days (87%) in laboratory mice. The rest radionuclides amount of given model was considered as non-excreted from the organism during the observation period. It was determined on the example of voles that 90Sr and 137Cs loss in males was faster than in females, and among females more intensive excretion was in lactating females. 137Cs excretion from the body of bank vole is mainly with urine (74.7%), whereas 90Sr one--with feces and urine in approximately equal amounts. Due to the birth of babies and consequent feeding female lose appreciably less amount of radionuclides body burden than at daily loss with urine and feces.     

Prognosis of accumulation of 137Cs and 90Sr in the herbage of the main types of the Belarus Polessje meadows using agrochemical soil properties

On the basis of long-term stationary experience it was established that the minimum accumulation quantities for 137Cs and 90Sr in the herbage of the dry, lowland and flood-plain types of the Belarus Polessje meadows contaminated with Chemobyl radionuclides are determined when the optimum of basic agrochemical soil properties is achieved with application of the scientifically reasonable protective measures. For remote prognosis of radionuclide contents in natural and cultural meadow herbage the use of transfer factors (TFa, (Bq/kg)(kBq/m2)) based on the complex agrochemical parameters--agrochemical cultivation soil index (Icd) and basic saturation degree (V, %), which take into account some soil characteristics simultaneously, is a streamlined approach. This paper provides the equations of linear and multiple regressions, which can be used to calculate the transfer factors for 137Cs and 90Sr uptake and the herbage contamination degree for the main types of meadows of the region, that will allow reducing the volume of forage production (hay, green bulk), which is not adequate to established permissible levels: "Republican allowable levels of the contents of 137Cs and 90Sr in agricultural raw material and forages".     

A mathematical model of 137Cs uptake and removal from the body of cattle in the event of chronic consumption of contaminated fodder

A two-chamber mathematical model of 137Cs uptake and removal from the body of cattle chronically consuming contaminated fodder has been developed; the model takes into account age dependence of radionuclide absorption from the gastro-intestinal tract. The model parameters were taken from the experiment on calves with chronic peroral uptake of contaminated fodder. In accordance with the model and experiment, 137Cs transfer factor to the muscular tissue one month after birth reaches a maximum value of 56% of the daily uptake per 1 kg of the tissue. By the model, the equilibrium processes of uptake and removal set in two years after the calves birth. The equilibrium TF for muscles in adults approximates 2.8% of the daily uptake per 1 kg tissue. Because of 137Cs absorption from the gastrointestinal tract changes with age, doses of internal exposure of calves over the first two years will be about 5 times higher than doses for any one of the two subsequent years.     

The optimization of the soil acidity of agrocenosis contaminated 137Cs and 90Sr: threshold parameters

During the field researches were determined the differences between agrochemical optimum of the acidity of the Sod-podzol loamy sand soil, which provides high productivity of the crops and the pH-value, which provides the minimal accumulation of 137Cs and of 90Sr by the biomass (the ecological optimum). On the average for the majority of the agricultural plants the minimal accumulations of 137Cs and of 90Sr are noticed under pHKCl 6.7, which is higher than agrochemical optimum on 0.7. The efficiency of liming under the discrimination of 137Cs and of 90Sr is much higher in soils with low values of pH. On the average, in crop rotation due to decreasing of the acidity in the soil from 4.9 to 5.9 pHKCl, the crop yield has grown on 9%, 137Cs contents has decreased on 16.7%, 90Sr--on 23.7%. The further decreasing of the soil acidity (from 5.9 to 6.8 pHKCl) was poorly effective: the productivity didn't change essentially. The transfer of 137Cs decreased on 8.9% and of 90Sr on 8.4%.     

The dependence of accumulation of 137Cs and 90Sr radionuclides in the forages cultivation degree of sod-podzolic soils

For prognosis of accumulation of 137Cs and 90Sr in forages harvested in radionuclide contaminated sod-podzolic soils, it is suggested to use transfer factors (TF9a) (Bq/kg)/(kBq/m2)) established not only by the content of mobile potassium (137Cs, r = -0.53) and the value of exchange acidity (90Sr, r = -0.73), but also by the index of agrochemical soil cultivation I(cd) (137Cs, r = -0.69; 90Sr, r = -0.64). The possibility of obtaining forages conforming to the state standards on the haymaking and pasture areas with high density of radioactive contamination of soils was shown by the example of "Sudkovo" collective farm. The approach is based on achievement of a high degree of cultivation (l(cd) - 0.81-1.0) due to a complex of protective measures, which resulted in a 10-fold decrease in the specific activity of 137Cs and a 4-fold decrease in the activity of 90Sr, compared to the soils with a low degree of cultivation (I(cd) - 0.41-0.60).     

Evaluation of parameters of radionuclide transition from soil particles and plant components of the upper layer of turf to cow's milk under pasture conditions

An experiment was conducted on feeding lactating cows with soil and turf additives contaminated with both 137Cs and 90Sr of the Chernobyl origin. The radionuclides transfer coefficients (%) in the food chain were for soil additives: for 137Cs--0.02 +/- 0.006, for 90Sr--0.01 +/- 0.002; for turf additives: for 137Cs--0.02 +/- 0.005, for 90Sr--0.06 +/- 0.035. Regarding 90Sr, there is no significant tendency to higher transfer rate for the radionuclide from turf component compared to that for soil component. A contribution of soil component as well as turf component of soil was evaluated as an additional source of milk contamination while grazing cattle. It was concluded that the contribution is not pronounced at the remedial period after the accident (approximately 3% from total activity consumed with ration) and it can be rejected in cattle breeding practice. The results achieved can be used for prediction of radionuclides concentrations in milk produce in cattle breeding under industrial contamination of agricultural lands.     

Assessing the potential of short rotation coppice (SRC) for cleanup of radionuclide-contaminated sites

A small-scale greenhouse investigation was undertaken using Goat willow (Salix caprea) and aspen (Populus tremula) to evaluate the potential of short rotation coppice for remediation of 137Cs- and 90Sr-contaminated sites. Results showed that both species were able to accumulate these radionuclides from a representative disposal soil (aged) and a spiked soil S. caprea accumulating greater levels of 137Cs than P. tremula, with no difference between species for 90Sr accumulation. For each radionuclide, the distribution in both species was similar, with 137Cs accumulation greatest in the roots, whereas 90Sr accumulation was greatest in the leaves. It was also evident that the soil-to-plant transfer factor (Tf) values for 90Sr were greater than for 137Cs, agreeing with differences in the reported bioavailailablity of these radionuclides in soil Based on the Tf values for S. caprea (conservative), estimated remediation times were 92 and 56 yr, for 137Cs and 90Sr, respectively. It is suggested that the selection of Salix species grown in a system of SRC provides a significant opportunity for removal of both 137Cs and 90Sr, primarily due to its higher biomass production. However, for 137Cs phytoremediation investigations into the appropriate use of soil amendments for increasing bioavailability are required.     

The level of aberrant cells in various tissues of bank vole depending on doses and radionuclide balance in organism

A regression analysis shows the direct linear relation between 137Cs accumulation in rodents and the level of aberrant cells. For 90Sr this trend was negative. The dose relationship was the same with 137Cs. The trends were negative 1 month later after feeding of animals with clean food. Correspondingly the dose relationship was also negative. The levels of cells with apoptosis features were different in animals from the control and the radiocontaminated sites. The analysis has revealed the correlation between the 90Sr content in animal body and the number of alveolar macrophages containing micronuclei. The relationship was revealed between the 137Cs content in the animal body and the number of intestinal epithelial cells with micronuclei.     

The migration of radionuclides from global fallout in the trophic chains of biogeocenoses in arid zones

Radionuclide (137Cs and 90Sr) content in soil, plants, terrestrial vertebrates and invertebrates has been studied in Kalmyk ASSR, Turkmenian SSR, and Great Gobi Reserve (Mongolia). The content of radionuclides accumulated by wild animals in arid zone biogeocenoses and the patterns of radionuclide migration along food chains have been estimated. 90Sr was found to be involved in biological cycles with participation of soil and terrestrial organisms 3-23 times more intensively than 137Cs.     

Disparity in 90Sr and 137Cs uptake in Alpine plants: phylogenetic effect and Ca and K availability

Background and aims

Uptake of ⁹⁰Sr and ¹³⁷Cs in plants varies widely between soil types and between plant species. It is now recognized that the radionuclide uptake in plants is more influenced by site-specific and plant-specific parameters rather than the bulk radionuclide concentration in soil. We hypothesized that the stress which Alpine plants experience because of the short growing season may enhance the phylogenetic effect on the ¹³⁷Cs and ⁹⁰Sr transfer factors as well as the dependency of the uptake by plant to the concentrations of exchangeable Ca and K of soils.

Methods

We carried out a field study on the ⁹⁰Sr and ¹³⁷Cs uptake by 11 species of Alpine plants growing on 6 undisturbed and geochemically different soils in the Alpine valley of Piora, Switzerland.

Results

Results show that a strong correlation exists between the log TF and the log of exchangeable Ca or K of the soils.

Conclusions

Cs uptake by Phleum rhaeticum (Poales) and Alchemilla xanthochlora (Rosales) is more sensitive to the amount of exchangeable K in the soil than the corresponding uptake by other orders. Moreover, the ⁹⁰Sr results indicate a phylogenetic effect between Non-Eudicot and Eudicots: the order Poales (Phleum rhaeticum) concentrating much less ⁹⁰Sr than Eudicots do.     

Radioecological research of the Irtysh-River's and Ob-River's water, base and flood depositions

The radioecological research of Irtysh-river and Ob-river was held. The content of 137Cs in Irtysh water was compounded 0.62-1.23 Bq/m3, in Ob-- 0.24-0.27 Bq/m3, and the one of 90Sr in Irtysh-- 10-20 Bq/m3, and in Ob-- 5-10 Bq/m3, that is much lower than the permissible sanitary-hygienic norms for the population. The 137Cs stores density on Irtysh-river input lease was compounded 2.7 kBq/m2, is almost in 11 times slashed downstream and is peer 245 kBq/m2 before the Irtysh-river lockin. The 90Sr stores density also was slashed in surveyed leases with 212 down to 106 Bq/m2. Two variants of integrated stores of 137Cs and of 90Sr in flood of the Irtysh-river was held. The balance calculation of annual radionuclides sinks confirms the dominant amount of 137Cs and of 90Sr in downstream Ob-river leases acts now on the Ob's sleeve, instead of from the Irtysh-river as it was supposed earlier. The 137Cs medial annual inflow from the Ob's sleeve almost is in 2 times, and the 90Sr inflow is in 2.3 times more, than are acts from Irtysh-river sleeve.     

Transfer of 85Sr and 134Cs from diet to reindeer foetuses and milk

Sr-85 and ¹³⁴Cs in aqueous solution of the chlorides were administered daily to four pregnant reindeer during the last part of gestation. Radionuclide concentrations were determined in calves sacrificed at birth, and secretion of the nuclides was measured in milk. Although the gastrointestinal absorption of ⁸⁵Sr was low, an apparently higher transfer of the absorbed fraction of ⁸⁵Sr than ¹³⁴Cs from the mother to the foetus led to similar accumulation of ⁸⁵Sr and ¹³⁴Cs in foetuses. At birth 1.4–1.6 and 1.5–2.5% of the total administered activities of ⁸⁵Sr and ¹³⁴Cs, respectively, were present in the calves‘ bodies. Transfer coefficients (F _m) for ⁸⁵Sr and ¹³⁴Cs from feed to milk were estimated at 0.0218±0.0026 and 0.185±0.025 day kg⁻¹, respectively, and the observed ratio (OR_milk-diet) for ⁸⁵Sr was 0.124±0.037. Transfer of radiostrontium to reindeer milk was in agreement with previously reported relationships between Ca intake and radiostrontium transfer in ruminants. These relationships suggest that the transfer of radiostrontium to foetuses and milk of free-ranging reindeer can be 3–4 times higher than observed in this experiment (due to lower Ca intake with natural forage), but the transfer to milk will not be as high as that of ionic ¹³⁴Cs. The concentrations of ⁸⁵Sr in milk suggested that the does mobilized skeletal stores of Ca and ⁸⁵Sr for milk production, although the diet appeared to satisfy the Ca requirements. In reindeer with radiostrontium intake during the whole year, radiostrontium concentrations in milk will therefore be higher than indicated by the F _m value observed in our study. No differences in half-times for ⁸⁵Sr and ¹³⁴Cs secretion in milk were detected. Both nuclides were secreted with short- and long-term half-times of 1–2 and 12–19 days, respectively. For ⁸⁵Sr, 80–90% of the activity was excreted with the short half-time, whereas the corresponding value for ¹³⁴Cs was 30–50%.     

Radioecological situation at the villages of the Techa river

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.     

Basic features of seasonal and multi-year dynamics of Cs-137 and Sr-90 in wood

Basic features of seasonal and multiyear dynamics of accumulation of Chernobyl-derived 137Cs and 90Sr in wood are considered. Seasonal variation in the radionuclide concentration are shown to be more regular and predictable than the multiyear variation. Seasonal dynamics of 137Cs is opposite by trend to that of 90Sr. The multiyear dynamics of both 137Cs and 90Sr in the wood is variable and depends on chemical nature of individual radionuclide, type of landscape, kinetics of the radionuclide plant-available forms, and irreversible fixation of the radionuclides in the root-abundant soil layer.     

The features of radioactive contamination of small birds in Chernobyl zone in 2003-2005

Radioactive contamination of small birds (484 individuals, 44 species) was investigated in the Chernobyl zone (Ukraine) in 2003-2005. Values variation of 90Sr and of 137Cs activity concentration reached 3-4 orders of magnitude even in one site, and maximum values amounted to hundreds Bq/g at the central plots of the zone. The biggest contamination is appropriate to birds in breeding season and to settled species, whilst migrants are the "cleanest". Change of contamination within a year reflects seasonal and short-term changes in birds diet and in behaviour. During breeding season females have higher activity concentration of 90Sr, while on 137Cs accumulation sexual differences are absent. In other seasons radioactive contamination of male and female does not differ if they live in similar conditions and have similar migratory behavior. Young birds during fledging and just after, as a rule, have higher levels of 90Sr contamination than adults, and actually do not differ on 137Cs accumulation. On a set of own and published data, it was assumed, that in small birds the half-life period of 137Cs extraction amounts to 1-2 days, and 90Sr- 5-10 days, and dynamic equilibrium of the radionuclides turnover in organism is reached over 4-7 and 17-34 days, respectively, after the birds arrival on the contaminated site. Among 44 studied species, those who search invertebrates in soil top layer or forest litter (thrushes). have noticeably higher accumulation of 90Sr and of 137Cs. Specific differences of radionuclides accumulation for the rest birds were not revealed due to small sample sizes of the species.     

Comparison of the accumulation of 137Cs and 90Sr by six spring wheat varieties

The uptake of ¹³⁷Cs and ⁹⁰Sr by six varieties of spring wheat (Triticum aestivum) was compared in field trials on land contaminated by the Chernobyl accident. All the experimental varieties are officially adopted for agricultural use in Belarus and are used in large-scale production. Under identical conditions of nutrition, the productivity of the varieties varied significantly by a factor of 1.3. The extent of ¹³⁷Cs and ⁹⁰Sr accumulation by wheat grain, quantified as the concentration ratio, differed between the varieties by as much as a factor of 1.6, for both radionuclides. There was a significant linear positive correlation between the ⁹⁰Sr activity concentration in grain and straw, and the calcium concentration. The correlation between ¹³⁷Cs and potassium was not significant. The results suggest that certain varieties of spring wheat used in normal agricultural practice accumulate less ¹³⁷Cs and ⁹⁰Sr into grain than others. Some spring wheat varieties accumulated relatively less ¹³⁷Cs, but did not accumulate less ⁹⁰Sr. One variety, Quattro, had a significantly lower uptake of both ⁹⁰Sr (for grain) and ¹³⁷Cs (for both grain and straw) than that of the other varieties tested. The reduction efficiency achieved by the use of these varieties, however, is not as high as that achieved by soil amelioration techniques in the past. Nevertheless, since there are no additional costs or production losses associated with these varieties, their use in the contaminated areas is worth considering as a simple, practical, and effective contribution to reducing the uptake of both ⁹⁰Sr and ¹³⁷Cs and allowing farmers to produce food-grade grain.     

切尔诺贝利核事故以来隔离区动物生态的研究概况

综述了切尔诺贝利核事故以来乌克兰Schmalhausen动物研究所(SIZ)对核工厂周围隔离区(exclusionzone ,EZ)的野生动物所进行的长达20年的放射生态学调查研究。基于乌克兰以往鸟类迁移的观察资料,评估了137Cs和 90Sr在隔离区候鸟体内的含量。而且还选择一些动物物种作为环境状况的标准指示生物,目的是为了阐明1 37Cs在隔离区脊椎动物体内的污染情况;整个第聂伯河流域、基辅行政区和隔离区软体动物贝壳内 90Sr的β活性。结果表明不同物种相对放射性核累积、迁移和累积因素呈有规律的季节性和长期性变化趋势,这些参数的运用可以大大地减少数据的波动和复杂性。直接辐射毁坏森林后,营养链的崩溃和病死树昆虫害虫的爆发导致了其次级生态变化。99 %的隔离区并不直接受辐射的影响,人员撤离、农业和森林管理停止以及大规模排除污染是这些区域生态变化的主要因素。在初始变化之后,由于自然资源、捕食者和偷猎者等的限制,隔离区的动物密度和分布达到一个稳定的极限值。数年前成功地在隔离区引入了一群蒙古野马,该群体保持了稳定增长。重新评估了以前划定的若干自然保护位点目前的保护状况,并提出了建议扩大这些自然保护区的范围等保护措施。