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.     

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.     

Monte-Carlo prediction of changes in areas of west Cumbria requiring restrictions on sheep following the Chernobyl accident

Following the 1986 Chernobyl accident radiocaesium levels in sheep meat in some upland areas of the United Kingdom were above the national intervention limit. West Cumbria was one of these areas and restrictions are currently still in place. In addition to deposition from the Chernobyl accident, Cumbria has been subject to radiocaesium deposition from atmospheric nuclear weapons tests, the 1957 Windscale accident and routine releases from the Sellafield nuclear reprocessing plant. A Monte-Carlo approach has been used to try to predict areas in west Cumbria where radiocaesium activity concentrations in lamb meat would require the imposition of restrictions at different times after the Chernobyl accident. The approach models the transfer of radiocaesium from soil to vegetation, based upon soil organic matter, and from vegetation to lamb meat. Spatial inputs are soil organic matter and total post-Chernobyl (137)Cs and (134)Cs deposition; a ratio of Chernobyl (137)Cs to (134)Cs deposition has been used to differentiate Chernobyl and pre-Chernobyl (137)Cs deposition. Comparisons of predicted radiocaesium transfer from soil-vegetation and the spatial variation in lamb (137)Cs activity concentrations are good and predicted restricted areas with time after Chernobyl compare well to the restricted areas set by UK government. We predict that restrictions may be required until 2024 and that in some areas the contribution of pre-Chernobyl (137)Cs to predicted lamb radiocaesium activity concentrations is significant, such that restrictions may only have been required until 1994 as a consequence of Chernobyl radiocaesium deposition alone. This work represents a novel implementation of a spatial radioecological model using a Monte-Carlo approach.     

Genotypic effects in phytoavailability of radiocaesium are pronounced at low K intensities in soil

The differences in radiocaesium uptake between species were analysed in a series of solution culture and pot trials. Since radiocaesium uptake is very sensitive to the solution potassium (K) concentration, it was hypothesised that species depleting K in the rhizosphere to a larger extent, will have a higher radiocaesium uptake. Five species (bean, lettuce, winter barley, ryegrass and bentgrass) were grown for 18–21 days in nutrient solution spiked with ¹³⁷Cs and at 4 K concentrations between 0.025 and 1.0 mM. Shoot ¹³⁷Cs activities all decreased between 17- and 81-fold with increasing K supply. Shoot ¹³⁷Cs activities were 4-fold different between species at the lowest K supply and 3.4-fold different at high K supply. The same five species were grown in two ¹³⁴Cs spiked soils with contrasting exchangeable K but similar clay content. Shoot ¹³⁴Cs activities were up to 19-fold higher in the soil with lowest exchangeable K. Differences in shoot activity concentrations between the species were only 4.5-fold in the high K soil, but were 15-fold in the low K soil. Bulk soil solution ¹³⁴Cs and K concentration data were combined with radiocaesium uptake characteristics measured in solution culture to predict radiocaesium uptake from soil. Predictions were within 1.6-fold of observations in the high K soil but largely underestimated ¹³⁴Cs uptake in lettuce, ryegrass and barley in the low K soil. A solute transport model was used to estimate K and radiocaesium concentrations in the rhizosphere. These calculations confirmed the assumption that higher radiocaesium uptake is found for species that deplete K in the rhizosphere to a larger extent.     

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.     

Body concentration of caesium-137 in patients from Western Isles of Scotland.

OBJECTIVES--To compare caesium-137 concentrations in patients from the Western Isles Health Board, Glasgow area, and other parts of the Scottish mainland, and to investigate the source of 137Cs in patients from the Western Isles. DESIGN--Study of hypertensive patients having electrolyte concentrations measured, including 137Cs. Interview by questionnaire of island subjects about intake of foods likely to contain radiocaesium and the source of these foods. Measurement of 137Cs and 134Cs in food, urine, and vegetation. SETTING--Scottish mainland and Western Isles, 1979-86. All measurements before Chernobyl nuclear accident. PATIENTS--413 consecutive patients referred to the blood pressure unit for investigation of hypertension. 60 from the Western Isles, including 44 from North Uist; 32 from North Uist participated in the dietary analysis. MAIN OUTCOME MEASURES--Concentration of radiocaesium in the body, urine, food, and vegetation. Islanders'' consumption of local produce. RESULTS--Patients from the Western Isles had five times higher body concentrations of 137Cs (median 2.54 (interquartile range 1.25-3.73)) Bq/gK) than did patients from around Glasgow (0.47 (0.26-0.66) Bq/gK) and other parts of the Scottish mainland (0.42 (0.24-0.71) Bq/gK). Islanders often consumed local milk and mutton, but ate local fish rarely. 137Cs and 134Cs were present in coastal (21.6 Bq/kg 137Cs, 0.25 Bq/kg 134Cs) and moorland (135.9, 0.65 Bq/kg) grasses and in islanders'' urine (2.01, 0.013 Bq/l). Lower concentrations (0.336, 0.004 Bq/l), were found in the urine of Glasgow controls (p less than 0.001 for both isotopes). CONCLUSIONS--Islanders have excess body 137Cs concentrations, most of which probably comes from local milk and lamb. The radioactivity is not above the recommended safety limit. The presence of 134Cs suggests that nuclear reprocessing is the source of some of the radiocaesium.     

Radioecological problems in coastal landscapes of the Sea of Azov

The features of the spatial distribution, of the migration, and of the accumulation of natural (232Th) and manmade (137Cs) radioactive nuclides in the coastal landscapes of the Sea of Azov are studied. It was shown, that the specific activity of 232Th in the accumulation of the so-called "black sands" was shown as high as 6000 Bq/kg, that increases the natural geochemical background in 200 times. The impact of aerial transfer of the "black sands" on 232Th migration and accumulation in the soil-plant system was clarified. The 232Th distribution down the soil profile suggests that the "black sands" are likely the product of the erosion of the coastal parent materials enriched by natural radionuclides. In general, the specific activity of 137Cs in the beach sand is not high and it is close to the background (global fallout) value. It was determined that 137Cs content in the coastal ecosystems is connected only by aerial pathway as a part of global and Chernobyl-born fallout.     

Comparison of the post-Chernobyl 137Cs contamination of mushrooms from eastern Europe, Sweden, and North America.

A comparison was made of 134Cs and 137Cs contamination in fungi from eastern Europe and eastern North America. Mean activities of 25 Ukrainian, 6 Swedish, and 10 North American collections were 4,660, 9,750, and 205 Bq/kg (dry weight), respectively. Additional measurements were made on samples from the Moscow, southern Belarus, and Yugoslavia/Bulgaria regions. Activity values were found to vary by several orders of magnitude within all geographic areas, even for the same mushroom species. Significantly higher specific activities were observed in mycorrhizal species than in saprophytic and parasitic fungi. Unfortunately, many of the European mycorrhizal species considered as prized edibles contained unacceptably high levels of 137Cs (> 1,000 Bq/kg [dry weight]) and should be used sparingly as food. By contrast, no mushrooms collected in Ontario or northern Michigan exceeded 1,000 Bq of 137Cs per kg (dry weight). The excessive 137Cs contamination was evident in mushrooms from areas that had substantial fallout from the 1986 accident in reactor 4 at the Chernobyl nuclear power station. However, observations suggest that about 20% of the 137Cs in eastern Europe (Moscow area, Belarus, and Ukraine) is of non-Chernobyl origin.     

Effect of biotite,zeolite, heavy clay,bentonite and apatite on the uptake of radiocesium by grass from peat soil

Biotite is a potassium rich mineral, which is used as a fertilizer in organic farming and as a soil amendment in conventional farming. Its ability to reduce ¹³⁴Cs uptake by ryegrass from peat soil was studied in pot experiments and compared with zeolite, heavy clay, bentonite and apatite. In addition, the long-term effect of biotite on ¹³⁷Cs uptake from peat soil was studied in the peat field. In the pot experiments in the first cut of ryegrass, the minerals decreased ¹³⁴Cs uptake by plants in the following order: zeolite > heavy clay > bentonite > biotite > apatite. Apatite did not have any effect on the plant ¹³⁴Cs level. In the later cuts, the uptake of ¹³⁴Cs from biotite-treated soil decreased further while that from soils treated with other minerals remained unchanged or even increased. In general, ¹³⁴Cs uptake by plants decreased with increasing mineral level. The decrease of ¹³⁴Cs uptake became more efficient, especially at the early growth stage, by mixing small amounts of zeolite in biotite. The results of the field experiment indicated the long-term effect of biotite on reducing ¹³⁴Cs uptake by plants. Biotite application rate was 30 t ha-1. The five-year mean of the plant/soil concentration ratio of ¹³⁷Cs was 0.05 for biotite-treated soil, in contrast to 0.14 for the control soil. On the whole, biotite reduced considerably the ¹³⁷Cs level of plants on peat soil and this effect was long-lasting. For an effective reduction of plant radiocesium a great quantity of biotite is needed and therefore it is most suitable for greenhouse cultivation where contaminated slightly decomposed peat is used as a growing medium.     

The analysis of coefficient of 137Cs transfer from soil into potato in relationship with 137Cs content in soil and plant mineral feed

The soil-potato transfer factor for 137Cs (TF) was estimated by using results of 137Cs activity concentration measurements in 214 samples of soil and potato taken at fields with various level of contamination with 137Cs. The relationships between the coefficient TF and soil characteristics (acidity pH (KCl), content of K2O, P2O5, CaO and MgO in soil) and soil contamination with 137Cs have been analysed. The results show that the TF values tend to decrease with increasing concentration of 137Cs, K2O, P2O5, and CaO in considered sod-podsolic sandyloam soil. The regression function describing the TF dependence of 137Cs, K2O, P2O5, and CaO content in soil has been derived.     

Model for calculation of fish contamination by 137Cs and its application for Lake Kozhanovskoe (Bryansk Region)

A dynamic model was developed for evaluation of the fish contamination by 137Cs. The dynamics of the accumulation of the radionuclide and the elimination is calculated taking into account the ecological and physiological characteristics of the fish, such as growth and metabolic rates, its position in the food chains of the aquatic ecosystem. The biological elimination of 137Cs from the freshwater fish is proportional to the metabolic rate of the fish. The dimensionless coefficient of the proportionality is equal to epsilonA = 0.3 +/- 0.1. The model was applied for the reconstruction of the long-term dynamics of 137Cs in the food chain "goldfish-pike" from Lake Kozhanovskoe (Bryansk Region, Russia). In 1990-1999 the specific activity of 137Cs in goldfish (generation of 1990) varied in range about 5-20 kBq/kg, whereas the specific activity of 137Cs in pike (generation of 1989) varied in range about 20-40 kBq/kg. The comparison with the data of the observations confirmed that the presented method allows to evaluate adequately the levels and the dynamics of 137Cs accumulation by the freshwater fish.     

Radioactivity in mushrooms,mosses and soil samples of defined biotops in SW Bavaria-two years after “Chernobyl”

Summary Mushrooms, the moos/grass layer and soil samples have been collected in autumn 1987 from two sites in SW-Bavaria in continuation of a former investigation (Elstner et al. 1987). There were still relatively high amounts of ¹³⁷Cs and ¹³⁴Cs in all samples. The ratio ¹³⁷Cs/¹³⁴Cs changed according to the different half-life times of the two radioisotopes, indicating in nearly all cases the Chernobyl accident as source. The distribution of the radioisotopes within the mushroom populations shows considerable variation, even within the same species and location. Besides ¹³⁷Cs, ¹³⁴Cs and ⁴⁰K no other radioisotopes were detected.     

The assessment of 137Cs accumulation by pine tree plantations in the closest radioactive fallouts originated from the Chernobyl Nuclear Power Plant

The assessment of 137Cs accumulation by wood is made by using a chamber model of radionuclide behavior. Maximum of 137Cs specific activity in wany wood was in the midst of 1990s, with subsequent decrease in activity and half-time up to 22 to 25 years.     

Reduction of Radiocesium Transfer to Animal Products Using Sustained Release Boli with Ammoniumiron(III)-Hexacyanoferrate(II)

A sustained release bolus with the cesium binder ammoniu-miron(III) - hexacyanoferrate (AFCF) has been developed as a countermeasure for small ruminants grazing pastures contaminated by radiocesium (134Cs+137Cs). The boli (40-50 g) are produced by compression of a mixture of AFCF, barite and wax. The release of AFCF from boli labelled with 137Cs-iron-hexacyanoferrate complex was studied in laboratory sheep. The release rate followed first order kinetics during the 108 d of observation and decreased from 40 to 22, 110 to 35 and 280 to 25 mg d−1 in sheep treated with 1, 2 or 3 boli respectively. The efficiency of boli in reducing radiocesium transfer to meat and milk was tested in laboratory studies with goats fed 134Cs tracer. Until 40 d after treatment the transfer of radiocesium to milk was reduced by 35%, 60% and 85% in goats given 1, 2 or 3 boli, respectively. The reduction in radiocaesium transfer persisted for 90 d but with a lower efficiency. A similar relationship was found between number of boli and the reduction in radiocesium transfer to meat with an observed maximal reduction of 60%.     

Long-term development of the radionuclide exposure of murine rodent populations in Belarus after the Chernobyl accident

As a determinant of the associated health risks, the behavior of radionuclides in natural ecosystems needs to be better understood. Therefore, the activity concentration of various long-lived radionuclides released due to the Chernobyl accident, and the corresponding contributions to the whole-body dose rate, was studied as a function of time in mammalian indicator species inhabiting the natural forest ecosystems of Belarus, the bank vole (Clethrionomys glareolus) and the yellow-necked mouse (Apodemus flavicollus). The activity concentrations of ¹³⁷Cs, ¹³⁴Cs, ⁹⁰Sr, ²³⁸Pu, ^239,240Pu, ²⁴¹Pu and ²⁴¹Am in soil and in animals were measured at five monitoring sites with different ground deposition of radionuclides at different distances from the destroyed reactor. The observed temporal pattern of the radionuclide activity concentration in the studied animal populations reflects the changes in biological availability of these isotopes for biota, mostly due to fuel particle destruction and appearance of dissolved and exchangeable forms of radionuclides. The time course of ^134+137Cs activity concentrations in animal populations appeared as a sequence of increase, peak and decrease. Maximal levels of radiocesium occurred 1–2 years after deposition, followed by an exponential decrease. Concentrations of incorporated ⁹⁰Sr increased up to the tenth year after deposition. The activity concentrations of transuranic elements (²³⁸Pu, ^239,240Pu, ²⁴¹Pu and ²⁴¹Am) were much lower than those of the other radionuclides, in the studied animals. A considerable activity of ²⁴¹Am in animals from areas with high levels of contamination was firstly detected 5 years after deposition, it increased up to the tenth year and is expected to increase further in the future. Maximal values of the whole-body absorbed dose rates occurred during the year of deposition, followed by a decrease in the subsequent period. Generally, this decrease was monotonic, mainly determined by the decrease of the external γ-ray dose rate, but there were exceptions due to the delayed maximum of internal exposure. The inter-individual distributions of radionuclide concentrations and lifetime whole-body absorbed doses were asymmetric and close to log-normal, including concentrations and doses considerably higher than the population mean values.     

Yeast associations with mosquitoes of the genus Aedes Mg. (Diptera, Culicidae) in the Tom-Ob river region

The inner microflora of blood-sucking mosquitoes genus Aedes inhabiting different biotops of aspen-birch woods of the Tomsc Priob region has been investigated. 120 strains of yeasts genera Pichia, Hansenula, Saccharomyces, Torulaspora, Metschnicowia, Rhodotorula, Cryptococcus, Candida and Aueobasidium have been isolated, the most number of species belong to the genus Pichia. Yeasts P. guilliermondii, A. pullulans and M. pulcherrima have been found during all periods of insects collection. The most number of yeasts species has been found in mosquitos of mass species--A. diantaeus, A. excrucians. A. punctor and A. communis. It is supposed that isolated yeasts are collected by mosquitoes off natural substrates in the course of their development.     

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.     

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).     

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.