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 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%.     

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 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).     

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.     

90Sr and 137Cs in higher aquatic plants of the Chernobyl nuclear plant exlusion zone]

The content of radionuclides 90Sr and 137Cs in higher aquatic plants of water objects within Chernobyl NPP exclusion zone has been analysed. Biodiversity of phytocenose was studied and species-indicators of radioactive contamination were revealed. The seasonal dynamics of radionuclide content in macrophytes was studied and the role of main aquatic plant clumps in processes of 137Cs and 90Sr distribution in abiotic component of biohydrocenose was demonstrated.     

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.     

向日葵(Helianthus annuus L.)对133Cs、88Sr的吸收和分布

通过盆栽试验研究了向日葵(Helianthus annuus L.)对土壤中不同处理浓度¹³³Cs和⁸⁸Sr的吸收,以及¹³³Cs和⁸⁸Sr在向日葵不同部位的分布。结果表明：随着处理浓度的增加,植物中¹³³Cs或⁸⁸Sr的含量增加。同一处理浓度下,⁸⁸Sr含量约比¹³³Cs含量高一个数量级。¹³³Cs和⁸⁸Sr在植物不同部位分布不同。根部中¹³³Cs含量高于植物的其他部位（茎、叶、花）。不同于¹³³Cs在植物中的分布,⁸⁸Sr除在根中的分布外,主要转运到了叶片。¹³³Cs和⁸⁸Sr在向日葵体内的分布与目前对放射性¹³⁷Cs和⁹⁰Sr的研究结果相似,所以¹³³Cs和⁸⁸Sr可分别预测¹³⁷Cs和⁹⁰Sr的运转。向日葵是治理大面积低放核素污染土壤的较佳植物种类。     

Radionuclide accumulation in fruit bodies of macromycetes

Coefficients of 137Cs accumulation and 90Sr were determined in macromycetes of different trophic groups (137Cs in 43 species and 90Sr in 19 species) in the conditions of droughty year (1992). Their variability in forest formations was determined in the period from 1992 to 1998. In the year with increased atmospheric humidity (1998), two-fold rise of 137Cs accumulation in fruit bodies was registered on average. The pollution of Boletus edulis correlates with photosynthetically active part of Betula pendula and Pinus silvestris closer than with soil pollution. This shows the possibility to indicate the pollution of short-living fruit bodies of fungi by the pollution of plants-symbiotrophs.     

The content in soil and the mobility of artificial radionuclides in the region of the regional radioactive waste storage situation

The objects of researches are the soil and wild vegetation in the region of the radioactive waste storage situation. In result of monitoring it was recognized 137Cs unlike 90Sr did not spread out of storage territory in spite of trench destruction and migration of radionuclides with surface and ground waters. The forms of 137Cs, 90Sr and natural radionuclide 226Ra in soils and coefficients of 90Sr accumulation for the different kinds of plants growing at the territory of storage and 50-m zone around it were researched. The low specific activities of mobile forms of 90Sr were recognized for samples of soils selected from lowland by the terrace. The considerable differences were found for specific activities of radionuclides for different soil layers. Essential irregularity of soil surface and vegetation contamination at the test points disposed at a short distances from each other also was found. The interpretation of obtained results is presented.     

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".     

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.     

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.     

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.     

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.     

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.     

Phytoplankton in reservoir R-11 of Techa reservoir cascade of Industrial Association "Maiak"

Phytoplankton of reservoir R-11 was investigated at vegetative seasons of 2007 and 2008. R-11 is a locking reservoir in the cascade of Mayak PA reservoirs. The specific activity in water of R-11 ranged from 0.9 to 1.8 kBq/dm for 90Sr and from 0.98 to 3.97 kBq/dm3 for 137Cs; in bottom sediments it ranged from 20 to 400 kBq/kg for 90Sr and from 0.35 to 220 kBq/kg for 137Cs. Concentration of SO4- exceeded the maximum permissible concentration for fishing reservoirs in 5-7 times. The content of 90Sr in the phytoplankton has made 400 kBq/kg (for dry weight), and 137Cs--2.20 kBq/kg (for dry weight). The absorbed dose of irradiation for the phytoplankton calculated under the content of 137Cs and 90Sr in water and in phytoplankton (the external irradiation from activity of bottom sediments was not considered) has made 901 mGy per year. Altogether the phytoplankton of reservoir R-11 included 107 species. Such species of Cyanobacteriae as Oscillatoria agardhii Gom. was the dominant in phytoplanktonic community. Another Cyanobacteriae, Lyngbya limnetica Lemm. and Aphanizomenonflos-aquae (L.) Ralfs. acted the most important part in a complex of species-subdominants. According to quantitative development of the phytoplankton the reservoir R-11 can be classified as P-mezosaprobe waters.     

The transfer of 90Sr and of 137Cs radionuclides in the chain of soil-fodder-animal products in the area contaminated as a consequence of the Chernobyl AES accident

The database on 137Cs and or 90Sr transfer factors in the soil-fodder-animal products chain compiled in the framework of the project "Radioecological Consequences of the Chernobyl Accident" under the French-German Initiative was analyzed. The 137Cs transfer factors were determined into 10 fodder types for farm animals. The 137Cs and 90Sr transfer from daily diet to milk is practically independent from milk yield and season and is about 0.83% and 0.16%. 137Cs transfer factor into beef (adult animals) is about to 2.4% from the daily uptake with fodder per 1 kg meat.     

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.