Behavior of <Superscript>137</Superscript>Cs in the soil-rhizosphere-plant system (by the example of the Yenisei River floodplain)

¹³⁷Cs speciation and distribution in the components of the biogeocenosis of the Yenisei River floodplain such as soils, rhizosphere, and plants were studied. The study was carried out near zones of influence by the Krasnoyarsk Mining and Chemical Combine (MCC). Variation in the specific activity of radionuclides with increasing distance from the pollution source and its ratio in the soil and rhizosphere and distribution in the plant body were studied. A variety of occurrence forms of ¹³⁷Cs, including mobile ones, was revealed. The amount of ¹³⁷Cs leached from plants during flooding was calculated from the results of laboratory experiments.     

Reconstruction of the contamination of the Techa River in 1949–1951 as a result of releases from the “MAYAK” Production Association

More accurate reconstruction of the radioactive contamination of the Techa River system in 1949–1951 has been made on the basis of refined data on the amounts and the rate of discharge of radionuclides into the Techa River from the Mayak Production Association; this has led to the development of a modified Techa River model that describes the transport of radionuclides through the up-river ponds and along the Techa River and deposition of radionuclides in the river-bottom sediments and flooded areas. The refined Techa River source-term data define more precisely the time-dependent rates of release and radionuclide composition of the releases that occurred during 1949–1951. The Techa River model takes into account the time-dependent characteristics of the releases and considers (a) the transport of radionuclides adsorbed on solid particles originally contained in the discharges or originating in the up-river ponds as a result of stirring up of contaminated bottom sediments and (b) the transport of radionuclides in soluble form. The output of the Techa River model provides concentrations of all source-term radionuclides in the river water, bottom sediments, and floodplain soils at different distances from the site of radioactive releases for the period of major contamination in 1950–1951. The outputs of the model show good agreement with historical measurements of water and sediment contamination. In addition, the river-model output for ⁹⁰Sr concentration in the river water is harmonized with retrospective estimates derived from the measurements of ⁹⁰Sr in the residents of the Techa Riverside villages. Modeled contamination of the floodplain soils by ¹³⁷Cs is shown to be in agreement with the values reconstructed from late measurements of this radionuclide. Reconstructed estimates of the Techa River contamination are being used for the quantification of internal and external doses received by residents of the Techa Riverside communities.     

Age-dependent accumulation of <Superscript>137</Superscript>Cs by pike <Emphasis Type="Italic">Esox lucius</Emphasis> in the Yenisei River

Age-dependent accumulation of ¹³⁷Cs in the muscles and bodies of the pike Esox lucius (aged two to seven years) inhabiting a section of the Yenisei River polluted with artificial radionuclides has been studied. The content of ¹³⁷Cs in muscles varied from 0.5 to 7.0 Bq/kg of fresh weight. The maximum content of the radionuclide has been found in juveniles. The content of ¹³⁷Cs in pike muscles and body decreased considerably with age. The high content of ¹³⁷Cs in the muscles of juveniles is probably a consequence of their higher intensity of feeding as compared to older individuals, which is due to the intense growth of juveniles.     

Artificial radionuclides in aquatic plants of the Yenisei River in the area affected by effluents of a Russian plutonium complex

The Yenisei River, one of the largest rivers in the world, is contaminated with artificial radionuclides released by one of the Russian nuclear plants, which produces weapons-grade plutonium and has been in operation for many years. The aim of the study that was conducted between 1997 and 2002 was to investigate accumulation of artificial radionuclides by aquatic plants of the Yenisei River. The aquatic plants sampled were: Potamogeton lucens (shining weed) and Fontinalis antipyretica (water moss). The -spectrometric analysis of the samples of aquatic plants for artificial radionuclides has revealed a wide spectrum of long-lived and short-lived radionuclides. Artificial radionuclides such as ⁵¹Cr, ⁵⁴Mn, ⁵⁸Co, ⁶⁰Co, ⁶⁵Zn, ¹³⁷Cs, and ¹⁵²Eu were found in aquatic plants collected both near the plutonium complex and 194 km downstream in the river. The radiochemical analysis of aquatic plants revealed strontium and isotopes of plutonium. Fontinalis antipyretica had very high concentration factors of the principal radionuclides: 14220, 3110 and 500 of ⁵¹Cr, ⁴⁶Sc and ²³⁹Np, respectively.     

Radioecological monitoring of the Yenisei River and citological characterization of a submerged aquatic plant Elodea canadensis

The study was devoted to investigation of the contents of radionuclides and of heavy metals and to evaluate the frequency of chromosomal aberrations in samples of Elodea canadensis, a submerged plant, collected in different parts of the Yenisei River. The samples were collected in the area subjected to radioactive impact of the Mining-and-Chemical Combine (MCC) at Zheleznogorsk and in the control area, upstream of the MCC. The investigations shown that elodea biomass in the area affected by MCC operation contained a long inventory of artificial radionuclides typical for the MCC discharges. The upstream of the MCC, in the control sampling area, the sediments and the elodea biomass contained only one artificial radionuclide--137Cs. Thus, the exposure doses to elodea shoots and roots upstream of the MCC are small (not more than 8 microGy/d) and the main contribution info the dose is made by natural radionuclides. At the MCC discharge site (the village of Atamanovo) and at the downstream of it, the total dose rate increases almost an order of magnitude, reaching its maximal values--72 microGy/d for elodea shoots and 58 microGy/d for its roots. Cytogenetic investigations of elodea roots shown that at the MCC discharge site (the village of Atamanovo) and at downstream of it the occurrence of chromosomal aberrations in ana-telophase and in metaphase cells of elodea was considerably higher than in the control area. It is highly probable that this simultaneous dramatic increase in the total exposure rate and the occurrence of chromosomal aberrations in elodea is associated with the radiation factor. It is suggested that elodea is affected not only by the radiation factor but also by the chemical factor--toxicity of heavy metals.     

The accumulation of the technogenic radionuclides by mushrooms in the area affected by the activity of the Krasnoyarsk mining-and-chemical industrial complex

The radionuclide content was measured in mushrooms collected in different sites situated in the zone of the radiation influence on the Mining-and-Chemical Combine at Zheleznogorsk and on the control site, near Krasnoyarsk, in 2002-2004. The analytical investigations of fruiting bodies of 12 mushroom species have revealed three gamma-emitting radionuclides: 7Be, 40K (natural) and 137Cs (artificial). It was found that only three species contain 7Be; activity concentration of 40K is not species- and site-dependent, averaging 1600 Bq/kg. All collected samples contain 137Cs, and its accumulation by mushrooms is species-specific. Suillus concentrates more 137Cs activity than other species and can be used as a bioindicator of soil contamination with radiocesium. The average activity concentration of 137Cs in Suillus granulatus collected in the sites subjected only to aerosol discharges of the MCC is more than twice higher than 137Cs content of the mushrooms collected in the control site--"Krasnoyarsk". The maximum activity concentration of 137Cs in Suillus samples collected in the sites that receive 137Cs with the flood water is an order of magnitude higher, amounting to 8624 Bq/kg. The analysis of the radionuclide distribution in a mushroom shows that 40K activity concentration is the same in caps and stems of Suillus, and 137Cs concentration in Suillus caps is 1.7-2.3 times higher than in stems. Binding of radionuclides by mushroom biomass was determined by chemical fractionation; it was found that the highest activities of 137Cs and 40K are in the exchange-adsorption fraction (56 to 71% of the total content of a radionuclide) and in the organic fraction (23 to 37%). Calculations were made for determination of the coefficients of 40K and 137Cs transfer from the soil to the fruiting body of Suillus.     

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.     

Testicular steroidogenesis is not altered by 137 cesium Chernobyl fallout,following in utero or post-natal chronic exposure

The testis is especially sensitive to pollutants, including radionuclides. Following the Chernobyl nuclear power plant accident, several of these radionuclides were emitted and spread in the environment. Subsequently, children presented some disruptions of the endocrine system. To determine whether these disruptions were due to 137 cesium (¹³⁷Cs) exposure, the effects of chronic contamination with low doses of ¹³⁷Cs in utero or from birth on testicular steroidogenesis in rats were studied. Contamination was continued for 9 months. No modification was observed in circulating level of hormones (17β-estradiol, testosterone, follicle-stimulating hormone, luteinizing hormone) following in utero or post-natal contamination. Expression of several genes involved in testicular steroidogenesis was affected (cyp19a1, fxr, sf-1), without modification of protein expression or activity. Our results suggest that growing organisms may be affected at the molecular level by ¹³⁷Cs contamination at this post-accidental dose.     

Radionuclides in siberian Thymallus from radiation-contaminated area in the middle stream of the Yenisei River

Concentration of artificial radionuclides in bodies of arctic grayling from the radioactively contaminated zone of the Yenisei River in the vicinity of the Mining-and-Chemical Combine of Rosatom was investigated in 2007-2010. Gamma-spectrometric analysis revealed artificial radionuclides in all the organs and tissues of fish. The isotope composition was the most diverse (60Co, 65Zn, 85Sr, 99Mo, 106Ru, 137Cs, 144Ce) in internal organs of grayling. The activity of radionuclides increased in internal organs including liver and kidney and in the content of digestive tract of grayling during winter and spring, which coincided with the change in the feeding spectrum of grayling. The trophic transfer factor of radionuclides from zoobenthos (Philolimnogammarus spp.) to whole bodies and muscles of grayling was over 1 (1.8-2.4) only for natural radionuclide 40K. The trophic transfer of artificial radionuclides (60Co, 65Zn, 137Cs) to muscles and bodies of grayling was one-two orders of magnitude less effective.     

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.     

Experimental estimation of the possible use of submersed macrophytes for biotesting bottom sediments of the Yenisei River

The laboratory testing of bottom sediments (BSs) from the Yenisei River containing different concentrations of technogenic radionuclides, heavy metals, and biogenic elements (N and P) based on aquatic such plants as Elodea canadensis (Canadian waterweed) and Myriophyllum spicatum (Eurasian watermilfoil) has revealed a higher sensitivity of roots to the general quality of BSs than shoots: shoot length (9%) < root length (11%) < root number (15%) in M. spicatum; shoot length (22%) < root length (42%) < root number (44%) in E. canadensis. In contrast to M. spicatum, the growth parameters of roots and shoots in E. canadensis have differed in a significant statistical manner between most BS samples. A reverse correlation has been found between the increase in shoot length and the activity of technogenic radionuclides in BSs, which is mostly significant in E. canadensis (r ² = 0.90–0.95, p = 0.05). Since the growth of shoots and roots in E. canadensis has turned out to be more sensitive to changes in the quality of BSs than that in M. spicatum, E. canadensis can be considered more prospective for biotesting BSs.     

The first results of using the <Emphasis Type="Italic">Allium</Emphasis> test in estimating the chemical and radiation toxicity of bottom sediments in the Yenisei River

The first results of the use of the Allium test for estimation of toxicity of bottom sediments in the Yenisei River and the effect of external γ-radiation under laboratory conditions are presented. The effect of stimulation of the onion root growth, i.e., the absence of toxicity was discovered in toxicological experiments using bottom sediments and under external γ-radiation. The stimulating effect of radiation on the growth of onion roots limits the use of the Allium test for testing samples from the Yenisei River ecosystem in the zone subjected to the impact of radioactive discharges from the Mining and Chemical Combine.     

Trophic position and metabolic rate predict the long-term decay process of radioactive cesium in fish: a meta-analysis

Understanding the long-term behavior of radionuclides in organisms is important for estimating possible associated risks to human beings and ecosystems. As radioactive cesium (¹³⁷Cs) can be accumulated in organisms and has a long physical half-life, it is very important to understand its long-term decay in organisms; however, the underlying mechanisms determining the decay process are little known. We performed a meta-analysis to collect published data on the long-term ¹³⁷Cs decay process in fish species to estimate biological (metabolic rate) and ecological (trophic position, habitat, and diet type) influences on this process. From the linear mixed models, we found that 1) trophic position could predict the day of maximum ¹³⁷Cs activity concentration in fish; and 2) the metabolic rate of the fish species and environmental water temperature could predict ecological half-lives and decay rates for fish species. These findings revealed that ecological and biological traits are important to predict the long-term decay process of ¹³⁷Cs activity concentration in fish.     

Measurement of resuspended aerosol in the Chernobyl area

Results of measurements of the resuspended radioactive aerosols in the Chernobyl area are presented which were obtained soon after the Chernobyl reactor accident and in a European project in 1992–1993. The measurements were carried out with the intention of obtaining a data base for dose assessment of resuspended radioactive particles. Potential significant dose contributions may result from inhalation and secondary contamination due to resuspended radionuclides. In this first article of a series of three papers, the instrumentation and the measurement uncertainties are discussed. An effort was made to sample quantitatively giant aerosol particles (particles larger than 10 μm aerodynamic diameter) as well. The comparison of the samplers shows, in general, an agreement of concentration measurements of ¹³⁷Cs and ⁷Be within a factor of two. One sampler was identified with larger discrepancies and needs additional investigation of its sampling characteristics; for another device, the recalibration of the analysing system is recommended. Ordinary integrating samplers have a loss of about 30% in ¹³⁷Cs activity compared to an isokinetic sampler collecting giant particles as well. The mean ratio of ¹³⁷Cs activity concentration between an instrument sampling only particles larger than 10 μm and an ordinary integrating sampler is 0.39 ± 0.15 during anthropogenic-enhanced resuspension. These findings demonstrate the significant contribution of giant particles to resuspended airborne radioactivity. The results of this study concerning integral measurements during wind-driven resuspension proved to be in good agreement with previously published data on resuspension. Received: 15 May 1997 / Accepted: 4 August 1997     

Radioactive contamination of Kiev vacationers after the Chernobyl accident. Biological half-life of Cs

Two young women vacationing in Kiev just after the Chernobyl accident received light radioactive contamination in and on their bodies, and on their clothing. The internal and external body contaminations were determined using a whole body counter and a pure germanium detector on two dates, 80 days apart. The total body activity that could not be diminished by washing corresponded to 50 kBq at the time of contamination. Important internal radionuclides were ¹³¹I, ¹³⁷Cs and ¹³⁴Cs causing a committed effective dose equivalent of 0.4 mSv. The biological half-life of Cs was 60 days. In the clothing 16 different radionuclides, including ²³⁹Np, were found at various levels of activity.     

Evaluation of Environmental Contamination and Estimated Radiation Doses for the Return to Residents’ Homes in Kawauchi Village,Fukushima Prefecture

To evaluate the environmental contamination and radiation exposure dose rates due to artificial radionuclides in Kawauchi Village, Fukushima Prefecture, the restricted area within a 30-km radius from the Fukushima Dai-ichi Nuclear Power Plant (FNPP), the concentrations of artificial radionuclides in soil samples, tree needles, and mushrooms were analyzed by gamma spectrometry. Nine months have passed since samples were collected on December 19 and 20, 2011, 9 months after the FNPP accident, and the prevalent dose-forming artificial radionuclides from all samples were ¹³⁴Cs and ¹³⁷Cs. The estimated external effective doses from soil samples were 0.42–7.2 µSv/h (3.7–63.0 mSv/y) within the 20-km radius from FNPP and 0.0011–0.38 µSv/h (0.010–3.3 mSv/y) within the 20–30 km radius from FNPP. The present study revealed that current levels are sufficiently decreasing in Kawauchi Village, especially in areas within the 20- to 30-km radius from FNPP. Thus, residents may return their homes with long-term follow-up of the environmental monitoring and countermeasures such as decontamination and restrictions of the intake of foods for reducing unnecessary exposure. The case of Kawauchi Village will be the first model for the return to residents’ homes after the FNPP accident.     

Soil-to-plant and soil-to-grain transfer of 137Cs in field-grown maize hybrids during two contrasting seasons: assessing the phenotypic variability and its genetic component

Field-grown maize hybrids were assessed for variability in ¹³⁷Cs accumulation in vegetative parts of young and mature maize shoots and grains during 2 years with contrasting climatic conditions. Trials were carried out at different sites in the Tula region of Russia, which is characterized by a highly homogenous soil classified as Luvic Chernozem according to FAO/UNESCO, and average contamination levels of about 509–564 Bq ¹³⁷Cs kg⁻¹ soil. In the first year, 19 hybrids were tested. The two hybrids with the highest and the two with the lowest ¹³⁷Cs concentration ratios (C _r) were also tested in the second year, together with another 11 hybrids. All samples were additionally assessed for their potassium content. In both investigation periods ¹³⁷Cs accumulation in vegetative shoots and grains was found to vary up to more than twofold between hybrids. However, C _r values of those hybrids that showed a relatively low ¹³⁷Cs accumulation in the first year were not necessarily low in the second year, and the ratio between the ¹³⁷Cs C _r of low- and high-accumulating hybrids was much smaller than in the year before. In both vegetative shoots and grains the variance caused by the different years was larger than the genotypic variance, thus indicating the limits of genotype selection for this trait. Significant correlations were determined between the ⁴⁰K and ¹³⁷Cs C _r values in the same tissue, but for one hybrid indications for uncoupling of the two traits were found. Average Cs/K ratios in young shoots, mature shoots and grains were 0.06, 0.05 and 0.02, respectively, indicating tissue- and stage-specific regulation of accumulation within each plant. The findings are discussed with respect to new approaches towards a better understanding of ¹³⁷Cs accumulation and its potential reduction in plants. Katharina Schneider was deceased.     

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.     

Micronuclei and nuclear anomalies in urinary exfoliated cells of subjects in radionuclide-contaminated regions

¹³⁷Cs contamination in living or agricultural environments may contribute to significant human internal exposure and cause adverse health effects. Contamination by ¹³⁷Cs and other radionuclides was detected in a river valley in northern Taiwan, in the 1990s. Given that the radioactivity appeared to be widely distributed in soil, rice and several other food plants in the areas surrounding several communities in the late 1990s [Y.B. Nabyvanents, T.F. Gesell, M.H. Jen, W.P. Chang, Distribution of ¹³⁷Cs in soil along Ta-han River Valley in Tau-Yuan County in Taiwan, J. Environ. Radioact. 54 (2001) 391], its possible impact on local occupants was further studied.Ten subjects in three families residing continuously in the highly contaminated valley and 10 non-exposed subjects matched for age, sex, and cigarette smoking habits from neighboring communities were evaluated for micronucleus frequencies and for degenerative nuclear changes in urinary exfoliated epithelial cells (EE cells). Micronucleus frequencies (‰) were significantly higher in the exposed subjects (4.79±1.21‰) than in the reference subjects (2.73±0.59‰; Wilcoxon 2-sample test, P value 0.0004). There were also higher frequencies of EE cells with karyolysis and condensed chromatin in the exposed subjects than in reference subjects. These results indicate that genotoxic and/or mutagenic effects on urinary epithelial cells occur in human subjects who have resided for a long time in a radioactively contaminated environment.     

Transfer of radionuclides to ants, mosses and lichens in semi-natural ecosystems

There is a scarcity of data on transfer of both natural and anthropogenic radionuclides to detritivorous invertebrates for use in the assessment of radiation exposure. Although mosses and lichens have been extensively used in biomonitoring programs, the data on transfer of radionuclides to these species are limited, particularly for natural radionuclides. To enhance the available data, activity concentrations of ¹³⁷Cs, ²²⁶Ra and ²²⁸Ra were measured in ants, mosses and lichens and corresponding undisturbed soil collected from semi-natural ecosystems in Serbia and Montenegro and biota/soil concentration ratios (CR) calculated. Since the majority of internal dose to biota is expected to come from ⁴⁰K, the activity concentrations of this radionuclide were also determined. The mean CR values for ¹³⁷Cs, ²²⁶Ra and ²²⁸Ra in ants analyzed in this study were found to be 0.02, 0.06 and 0.02, respectively. The mean CR values of radionuclides in mosses were found to be 2.84 for ¹³⁷Cs, 0.19 for ²²⁶Ra and 0.16 for ²²⁸Ra, while those in lichens were found to be 1.08 for ¹³⁷Cs, 0.15 for ²²⁶Ra and 0.13 for ²²⁸Ra. The CR values obtained in this study were compared with default CR values used in the ERICA Tool database and also with those reported in other studies.