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%.     

Assessing the Potential of Phytoremediation at a Site in the U.K. Contaminated With 137Cs

Spinacia oleracea L. cv. ‘Bloomsdale’, Beta vulgaris L. cv. ‘Flavescens’, Brassica juncea L. ‘OB825’, and Helianthus annuus L. cv. ‘Oranges and Lemons’ were grown for 8 weeks at a site contaminated with ¹³⁷Cs at Bradwell Nuclear Power Station, UK. The site was a trench approximately 1.5 m deep, 2 m wide, and 100 m long in ‘made ground’ consisting of alluvium with traces of illites, kaolinites, and smectites. ¹³⁷Cs activity concentration was measured in individual plants after 8 weeks growth and the soil in which they grew. The biomass produced and total ¹³⁷Cs removed to shoots differed significantly between species but ¹³⁷Cs activity concentrations and Transfer Factors (TFs) did not. B. vulgaris produced the most biomass and removed the greatest amount of ¹³⁷Cs. For all plants, and within each taxon, plants growing at low soil ¹³⁷Cs activity concentrations had significantly greater TFs than those growing at high soil ¹³⁷Cs activity concentrations. It is concluded that selecting plant taxa suited to a particular site can be an effective way of improving phytoremediation rates, that there is much scope for adjusting harvesting intervals to 8 weeks or less without affecting TFs, and that estimates of time taken for ¹³⁷Cs removal by phytoremediation should consider that TFs may increase as soil concentrations decrease. With refinements in methodology, phytoremediation has the potential to contribute significantly to decontamination of the site at Bradwell.     

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.     

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.     

Concentration of Strontium-90 at Selected Hot Spots in Japan

This study is dedicated to the environmental monitoring of radionuclides released in the course of the Fukushima nuclear accident. The activity concentrations of β⁻ -emitting ⁹⁰Sr and β⁻/γ-emitting ¹³⁴Cs and ¹³⁷Cs from several hot spots in Japan were determined in soil and vegetation samples. The ⁹⁰Sr contamination levels of the samples were relatively low and did not exceed the Bq⋅g⁻¹ range. They were up four orders of magnitude lower than the respective ¹³⁷Cs levels. This study, therefore, experimentally confirms previous predictions indicating a low release of ⁹⁰Sr from the Fukushima reactors, due to its low volatility. The radiocesium contamination could be clearly attributed to the Fukushima nuclear accident via its activity ratio fingerprint (¹³⁴Cs/¹³⁷Cs). Although the correlation between ⁹⁰Sr and ¹³⁷Cs is relatively weak, the data set suggests an intrinsic coexistence of both radionuclides in the contaminations caused by the Fukushima nuclear accident. This observation is of great importance not only for remediation campaigns but also for the current food monitoring campaigns, which currently rely on the assumption that the activity concentrations of β⁻-emitting ⁹⁰Sr (which is relatively laborious to determine) is not higher than 10% of the level of γ-emitting ¹³⁷Cs (which can be measured quickly). This assumption could be confirmed for the samples investigated herein.     

Verification of radiocesium decontamination from farmlands by plants in Fukushima

The purpose of this study was to verify radiocesium decontamination from Fukushima farmland by plants and to screen plants useful for phytoremediation. Thirteen species from three families (Asteraceae, Fabaceae, and Poaceae) of crops were grown in shallow and deeply cultivated fields (0–8 and 0–15 cm plowing, respectively). To change plowing depth was expected to make different contacting zone between root system and radiocesium in soil. The radioactivity values of the plants due to the radiocesium ¹³⁴Cs and ¹³⁷Cs were 22–179 and 29–225 Bq kg dry weight^?1, respectively. The ¹³⁴Cs and ¹³⁷Cs transfer factors for plants grown in the shallow field ranged from 0.021 to 0.12 and fro 0.019 to 0.13, respectively, with the geometric means of 0.051 and 0.057, respectively. The ¹³⁴Cs and ¹³⁷Cs transfer factors for plants grown in the deep field ranged from 0.019 to 0.13 and from 0.022 to 0.13, respectively, with the geometric means of 0.045 and 0.063, respectively. Although a reducing ratio was calculated to evaluate the decrease in radiocesium from contaminated soil during cultivation (i.e., phytoremediation ability), no plant species resulted in a remarkable decrease in radiocesium in soil among the tested crops. These results should be followed up for several years and further analyses are required to evaluate whether the phytoremediation technique is applicable to radioactively contaminated farmlands.     

Short rotation coppice as alternative land use for Chernobyl-contaminated areas of Belarus

Field experiments were conducted in the Chernobyl-affected area to assess if short rotation coppice (SRC) for energy production is a feasible alternative for contaminated land. Four willow clones were planted on sandy and peaty soil and the radiocaesium (137Cs) and radiostrontium (90Sr) transfer factors (TF) and yield relevant parameters were recorded during four growing seasons. The 137Cs and 90Sr soil-to-willow wood TF on sandy soil (second growing season) were on average 1.40+/-1.06 x 10(-3) m2 kg(-1) and 130+/-74 x 10(-3) m2 kg(-1), respectively. The 137Cs TF recorded for the peaty soil (fourth growing season or end of the first rotation cycle) was on average 5.17+/-1.59 x 10(-3) m2 kg(-1). The 90Sr-TF was on average 2.61+/-0.44 x 10(-3) m2 kg(-1). No significant differences between clones for the 137Cs and 90Sr-TF were observed. Given the high TFs and the high deposition levels, Belarus exemption levels for fuel wood were highly exceeded. The annual average biomass production for one rotation cycle on the peaty soil ranged from 7.8 to 16.0 t ha(-1) y(-1) for one of the clones, comparable with average annual yield figures obtained for western Europe. On the sandy soils, first-year yields were 0.25 t ha(-1) y(-1). These soils are not suitable for SRC production and should better be dedicated to pine forests or drought-resistant grasses.     

Evaluation of Chlorella as a Decorporation Agent to Enhance the Elimination of Radioactive Strontium from Body

Background

Release of radionuclides, such as ¹³⁷Cs and ⁹⁰Sr, into the atmosphere and the ocean presents an important problem because internal exposure to ¹³⁷Cs and ⁹⁰Sr could be very harmful to humans. Chlorella has been reported to be effective in enhancing the excretion of heavy metals; thus, we hypothesized that Chlorella could also enhance the elimination of ¹³⁷Cs or ⁹⁰Sr from the body. We evaluated the potential of Chlorella as a decorporation agent in vitro and in vivo, using ⁸⁵Sr instead of ⁹⁰Sr.

Methods

In vitro experiments of adsorption of ¹³⁷Cs and ⁸⁵Sr to Chlorella were performed under wide pH conditions. The maximum sorption capacity of Chlorella to strontium was estimated using the Langmuir model. A ⁸⁵Sr solution was orally administrated to mice pretreated with Chlorella. At 48 h after ⁸⁵Sr administration, the biodistribution of radioactivity was determined.

Results

In the in vitro experiments, although ⁸⁵Sr barely adsorbed to Chlorella at low pH, the ⁸⁵Sr adsorption ratio to Chlorella increased with increasing pH. The maximum sorption capacity of Chlorella to strontium was 9.06 mg / g. ¹³⁷Cs barely adsorbed to Chlorella under any pH conditions. In the biodistribution experiments, bone accumulation of radioactivity after ⁸⁵Sr administration was significantly decreased in the Chlorella pretreatment group compared with the non-treatment control group.

Conclusions

In conclusion, these results indicated that Chlorella could inhibit the absorption of ⁹⁰Sr into the blood and enhance the elimination of ⁹⁰Sr from the body through adsorption in intestine. Further studies are required to elucidate the mechanism and the components of Chlorella needed for adsorption to strontium and could promote the development of more effective decorporation agents.     

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。     

Accumulation of radionuclids in amphibians (<Emphasis Type="Italic">Pelophylax ridibundus</Emphasis> Pall.) in the Middle Urals

The accumulation levels of anthropogenic ⁹⁰Sr and ¹³⁴Cs and ¹³⁷Cs radionuclides in the marsh frog have been studied in the areas of the Beloyarskii water-storage reservoir (an industrial storm-water discharge channel of the nuclear power station) and the Verkhnii Tagil water-storage reservoir (the Tagil River down-stream of the dam). No significant distinction in the radionuclide accumulation (⁹⁰Sr and ¹³⁷Cs) depending on the amphibian sex and age is detected. Comparable levels of the accumulation of radionuclides in the marsh frog, when compared to the other representatives of the water ecosystem, are estimated. An assumption of the presence of some unidentified source of radioactive contamination of marsh frogs has been made; cesium-137 may be transferred from it to the Tagil River by the frogs.     

Soil-to-grain transfer of fallout 90Sr for 28 winter wheat cultivars

In order to identify wheat cultivars with minimum soil-to-grain transfer of fallout ⁹⁰Sr, 28 winter wheat cultivars were investigated at three different sites with different soil types in Upper Bavaria. Each cultivar was grown on an area of 10 m² and harvested in August 1999. Mean soil-to-grain concentration ratios (C _r) were 0.151 ± 0.029, 0.205 ± 0.035 and 0.060 ± 0.012, respectively. The C _r values obtained varied by factors of up to 2.6 for the different cultivars at a given site, and by factors of up to 5.0 for the different sites and a given cultivar. Site-averaged normalized concentration ratios (SANC_r) ranged from 0.666 ± 0.062 to 1.503 ± 0.161. The cultivars Convent, Ludwig, and Semper, showed the lowest uptake of ⁹⁰Sr compared to the mean of all cultivars at each site. A cultivar that shows both minimum uptake of ⁹⁰Sr and ¹³⁷Cs could not be identified. The results suggest that ⁹⁰Sr rather than ¹³⁷Cs might be the limiting radionuclide concerning the use of contaminated land for wheat production. Thus, more efforts might be necessary identifying wheat cultivars with minimum ⁹⁰Sr uptake.     

Plutonium,241Am,90sr,and137cs concentrations in some antarctic matrices

A radioecological survey in Antarctica shows that the^239+240Pu,²³⁸Pu,²⁴¹Am,⁹⁰Sr, and¹³⁷Cs activities were detectable in nearly all the samples. The activity level of^239+240Pu,²⁴¹Am, and¹³⁷Cs in antarctic sediments was about 5–20 times lower than in the northern Adriatic Sea sediments, but the²³⁸Pu activities were relatively high. It was interesting to note that the⁹⁰Sr concentrations in all the sediments tended to be low, which could be the result of the easier exchangeable behavior of⁹⁰Sr in water. High concentrations were detected in mosses and lichens and their activity levels were comparable to those in central Italy. The radionuclide ratio analyses show that the major part of^239+240Pu,²⁴¹Am,⁹⁰Sr, and¹³⁷Cs was a result of nuclear weapon tests. The higher²⁴¹Am/^239+240Pu ratio was observed and it could perhaps be the result of fallout of nuclear weapon tests prior to 1962. The²³⁸Pu/^239+240Pu ratio in the antarctic matrices was about seven times higher than in the Northern hemisphere and it could be inferred that the major part of²³⁸Pu was originating from the SNAP-9A satellite accident.     

Concentration of 137Cs, 65Zn,and 85Sr by fresh-water algae

Differences in the concentration and retention of ¹³⁷Cs by unicellular diatoms, filamentous green algae, and filamentous blue-green algae were demonstrated under both batch and continuous-flow culture conditions. ¹³⁷Cs concentration factors were generally higher by a factor of 2 in batch tests than in continuous flow tests. In retention studies, ¹³⁷Cs was desorbed more rapidly from algae under continuous-flow conditions. Studies with blue-green algae indicate that ¹³⁷Cs concentrations in the various species were more closely related to the surface-to-volume ratios of algal cells than to the systematic relationships of the three species. Continuous-flow studies indicated no differences among three species of filamentous green algae in the concentration of ¹³⁷Cs, ⁶⁵Zn, and ⁸⁵Sr. However, the average concentration factors of the radionuclides were considerably different: 3800 for ⁶⁵Zn, 460 for ¹³⁷Cs, and 230 for ⁸⁵Sr. These radionuclides were rapidly desorbed following the transfer of algae to nonradioactive media. The desorption rate was inversely related to the concentration rate.     

Reconstruction and forecast of doses due to ingestion of <Superscript>137</Superscript>Cs and <Superscript>90</Superscript>Sr after the Chernobyl accident

The assessment doses due to ingestion of ¹³⁷Cs and ⁹⁰Sr for the population suffering from the Chernobyl accident was performed on the basis of the new mechanistic ecological model for assessment of radiological consequences of agricultural lands contamination (EMARC). The EMARC model allows estimation of internal doses based on ecological factors influencing the contamination of foodstuff, for the post-accidental years in the countries of the former Soviet Union. The EMARC model allows estimation of all quantities required in radiation hygiene practice. For example, the proposed analytical method may be used for both retrospective dose reconstruction and prospective estimates of annual dose and integrated “life-time” dose, for different age intervals. According to the EMARC model, estimated reference “life-time” doses for adults are between 7 and 269 μSv kBq⁻¹ m² for ¹³⁷Cs, and between 25 and 235 μSv kBq⁻¹ m² for ⁹⁰Sr. Maximal doses were estimated for persons who were 3, 9 and 11 years old, at the time of the accident and these doses exceed those for adults by a factors of 1, 5 for ⁹⁰Sr, and 1.4 for ¹³⁷Cs.     

Caesium,potassium and ammonium distributions in different organs of tropical plants

In the present work the distribution of ions in aboveground plant parts was studied in order to establish the suitability of using radiocaesium as a tracer for the plant absorption of nutrients, such as potassium (K⁺) and ammonium (NH₄⁺). We present the results for the distributions of ¹³⁷Cs, ⁴⁰K and NH₄⁺ from four tropical plant species: lemon (Citrus aurantifolia), orange (Citrus sinensis), guava (Psidium guajava) and chili pepper (Capsicum frutescens). Activity concentrations of ¹³⁷Cs and ⁴⁰K were measured by gamma spectrometry and concentrations of free NH₄⁺ ions by a colorimetric method. Similarly to potassium and ammonium, caesium showed a high mobility within the plants, exhibiting the highest values of concentration in the growing parts of the tree (fruits, new leaves, twigs, and barks). A significant correlation between activity concentrations of ¹³⁷Cs and ⁴⁰K was observed in these tropical plants. The K/Cs discrimination ratios were approximately equal to unity in different compartments of each individual plant, suggesting that caesium could be a good tracer for ⁴⁰K in tropical woody fruit species. Despite the similarity observed for the behaviour of caesium and ammonium in the newly grown plant compartments, ¹³⁷Cs was not well correlated with NH₄⁺. Significant temporal changes in the NH₄⁺ concentrations were observed during the development of fruits, while the ¹³⁷Cs activity concentration alterations were not of great importance, indicating, therefore, that Cs⁺ and free NH₄⁺ ions could have distinct concentration ratios for each particular plant organ.     

Doses from external irradiation and ingestion of 134Cs, 137Cs and 90Sr of the population of Belarus accumulated over 35 years after the Chernobyl accident

This study considers the exposure of the population of the most contaminated Gomel and Mogilev Oblasts in Belarus to prolonged sources of irradiation resulting from the Chernobyl accident. Dose reconstruction methods were developed and applied in this study to estimate the red bone-marrow doses (RBMs) from (i) external irradiation from gamma-emitting radionuclides deposited on the ground and (ii) ¹³⁴Cs, ¹³⁷Cs and ⁹⁰Sr ingestion with locally produced foodstuffs. The mean population-weighted RBM doses accumulated during 35 years after the Chernobyl accident were 12 and 5.7 mGy for adult residents in Gomel and Mogilev Oblasts, respectively, while doses for youngest age groups were 20–40% lower. The highest mean area-specific RBM doses for adults accumulated in 1986–2021 were 63, 56 and 46 mGy in Narovlya, Vetka and Korma raions in Gomel Oblast, respectively. For most areas, external irradiation was the predominant pathway of exposure (60–70% from the total dose), except for areas with an extremely high aggregated ¹³⁷Cs soil to cow’s milk transfer coefficient (≥?5.0 Bq L^?1 per kBq m^?2), where the contribution of ¹³⁴Cs and ¹³⁷Cs ingestion to the total RBM dose was more than 70%. The contribution of ⁹⁰Sr intake to the total RBM dose did not exceed 4% for adults and 10% for newborns in most raion in Gomel and Mogilev Oblasts. The validity of the doses estimated in this study was assessed by comparison with doses obtained from measurements by thermoluminescence dosimeters and whole-body counters done in 1987–2015. The methodology developed in this study can be used to calculate doses to target organs other than RBM such as thyroid and breast doses. The age-dependent and population-weighted doses estimated in this study are useful for ecological epidemiological studies, for projection of radiation risk, and for justification of analytical epidemiological studies in populations exposed to Chernobyl fallout.

     

Radiostrontium contamination of soil and vegetation within the Semipalatinsk test site

The Semipalatinsk nuclear test site (STS) in the Republic of Kazakhstan was an important site for testing atomic bombs and other civil and military nuclear devices of the former Soviet Union. Results are presented from investigations on the extent of radiostrontium contamination in soils and vegetation at the technical areas of the STS, where the tests were conducted and in pastures used by farmers for grazing animals or for hay production. Our data are compared with those reported largely in the recent Russian language literature that has been reviewed. The extent of ⁹⁰Sr contamination of soil is highly variable over the STS with the highest values associated with the technical areas, particularly the Degelen mountains. Recently measured values in both the present data and the Russian language literature confirm the relatively high current contamination of soil and vegetation in the vicinity of tunnels and associated watercourses in the Degelen area. The proportion of ⁹⁰Sr in soil which could not be extracted with 6 M HCl was only an average of 20%, which is low compared to other test site areas and possibly indicates a relatively high mobility in this area, because the ⁹⁰Sr is derived from leakage from explosion tunnels along watercourses rather than being associated with fused silicates. A comparison of relative activity concentrations in soil and vegetation suggests that the transfer of ⁹⁰Sr to vegetation on the STS is high compared to that of ¹³⁷Cs and plutonium.     

Estimating Total Effective Dose Equivalents from Terrorist Use of Radiological Dispersion Devices

Radiological dispersion devices (RDDs), commonly called “dirty bombs,” utilize a conventional explosive to deliberately disperse non-fissile material as an aerosol. This analysis models total effective dose equivalent (Sv) at various locations down-wind from the detonation site subsequent to terrorists detonating a ²⁴¹Am, ¹³⁷Cs, ⁶⁰Co, ¹⁹²Ir, or⁹⁰Sr RDD. A source term for each isotope equaling 3.7 × 10¹³ Bq with an instantaneous release by either high explosives or low explosives at street level is assumed in order to evaluate total effective dose equivalent (TEDE) under various meteorological scenarios for intentional releases of non-fissile materials by terrorists. The inhalation pathway on average contributes most to TEDE. The inhalation pathway accounts for 96% (0.22 Sv) of the mean exposure estimate of 0.2321 Sv and occurs over an extremely short time frame (i.e., a few minutes). Ground shine, on average, contributes the second most to TEDE estimates accounting for approximately 4% (0.009 Sv) of the estimate. A cautionary note with regard to ground shine is warranted, however, because Hotspot estimates for this pathway are based on the assumption that a person is exposed for 4 days (96 hours). The TEDE for submersion (i.e., passing through the plume without inhaling particles) is negligible for the scenarios evaluated contributing less than 1% (5.2 × 10^?6 Sv) to the TEDE estimate averaged across all 140 model runs (5 nuclides × 2 rainfall scenarios × 2 explosive scenarios × 7 wind and atmospheric stability scenarios). The TEDE value for ²⁴¹Am from inhalation is much greater, on average, than the inhalation TEDE value for ⁶⁰Co, ¹³⁷Cs, ¹⁹²Ir, or ⁹⁰Sr. This underscores the potentially high risk to human health posed by exposure to ²⁴¹Am. Ground shine is the primary exposure pathway for ⁶⁰Co and ¹³⁷Cs due to the energetic and penetrating gamma rays those radionuclides emit. ¹⁹²Ir and ⁹⁰Sr have relatively low mean TEDE values for all of the pathways examined.     

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.     

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.