Dynamics of 134 + 137Cs accumulation in insects inhabiting the 30-kilometer zone of Chernobyl Nuclear Power Station

Accumulation of the specific activity of 134 + 137Cs in insects was investigated in the most typical biogeocenoses within the 30-km zone of the Chernobyl NPP. The studied biogeocenoses had different rates of the exposure doses. It was shown that the specific activity of 134 + 137Cs in the insects inhabiting forest biotops was of the same order that in the crown, whereas in the insects inhabiting open biotops the specific activity was higher than in plants. Two periods of the increased 134 + 137Cs content in insects were found: May and September. Along with seasonal activity variations, a tendency to decreasing and stabilization of 134 + 137Cs content was observed during the period of the study.     

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.     

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.     

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.     

Relations between resuspension and the content of 137Cs in freshwater fish in some Swedish lakes

In many Swedish lakes, the fallout of ¹³⁷Cs from the Chernobyl accident in April 1986 has largely accumulated in the sediments. The availability and transfer of deposited ¹³⁷Cs to biota is influenced by factors such as resuspension. The frequency of resuspension and the ¹³⁷Cs-content of different fish species was studied in three shallow lakes in Uppland, central Sweden, and in one deeper lake in northern Sweden. Resuspension was measured by the use of sediment traps. Sedimentation rates measured from the traps in the shallower lakes were 5–10 times higher than normal for this type of lake, indicating that resuspension was an important factor. The decrease of the ¹³⁷Cs-content in muscle tissue of pike, perch and roach was slow in each of the shallow lakes. ¹³⁷Cs decreased by about 30% over a period of 2 years in the shallowest lake (maximum depth 4 m), whereas ¹³⁷Cs decreased by 50% in the deeper lakes (maximum depth 10 m). The slower rates of decline of ¹³⁷Cs in biota from the shallow lakes, are probably a function of sediment dynamics (mainly influenced by lake morphometry, wind direction and strength). They may be influenced, also, by bioavailability of resuspended sediment material. In the deepest northern lake, much of the ¹³⁷Cs-containing material collected in the sediment traps originated from the catchment area. Resuspension was minimal, and the high activity of ¹³⁷Cs in the sediment had no effect on content or decline of ¹³⁷Cs in lake fish.     

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.     

Transfer of 137Cs from water to fish is not linear in two northern lakes

Empirical data on the behavior of radionuclides in the biosphere are needed for validating radioecological models. In this study, data collected from two lakes in Northern Finland were used to investigate the transfer of ¹³⁷Cs from lake water into fish during a 20-year period after the Chernobyl nuclear power plant accident. The results indicated that transfer of ¹³⁷Cs in the food chains investigated is nonlinear: the water-to-fish concentration ratios (CRs) decreased with increasing ¹³⁷Cs concentration in water. Major deviation from linearity (constant CR) commonly assumed in radioecological modeling was observed only at low ¹³⁷Cs concentrations in water. Other findings of potential importance for radioecological models were that ¹³⁷Cs concentrations were threefold higher in piscivores than in non-piscivores and that no differences in ¹³⁷Cs uptake were found between the two piscivorous species (pike and perch) studied or between three non-piscivorous species (vendace, white fish, and roach) representing different feeding habits (planktivore, benthivore, and mixed diet).     

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.     

Distribution and dynamic of 137Cs in arboreal plants

Dynamics of 137Cs specific activity (SA) in woody plants was examined. It was found that interseasonal variations of SA are connected mainly with precipitations and related oxygen in soil as well as Eh level. The rate of daily variation in SA in an individual tree can reach 19%. Acropetal or basipetal 137Cs distribution in the bole depends on physiological condition category (PCC) of a tree, weather and environment; SA ratio of higher and lower PCC depends on the same factors. In winter compared to summer higher SA correlation of tree separate parts was observed. Trees with 137Cs acropetal distribution in bark had proven lower general CA level.     

The formation of absorbed doses of 137Cs in the body of the female and her progeny during suckling

The transfer of 137Cs with maternal milk to progeny was studied in rats. The rats were administered with 25 kBq/g of 137Cs nitrate (pH = 6) in a single oral dose immediately after delivery. Nonpregnant females served as control. Absorbed doses per activity unit to lactating rats were 23% lover than to nonlactating ones. Over the suckling period, absorbed doses to young rats amounted to about 35% of the absorbed dose to the nursing female. For nonlactating females, the internal dose approximately equalled the sum of doses to the nursing female and young rats.     

Analysis of factors determining the biological availability of 137Cs in forest ecosystem soils

On five forest plots varying in species composition of woody plants and soil properties, 137Cs accumulation by vegetation of the forest understorey has been studied. Differences in 137Cs availability for root uptake are shown to be dependent on a vertical distribution of 137Cs content over the soil profile, percentage of exchangeable 137Cs and distribution of plant root systems (fungous mycelium) in soil. A 137Cs-bioavailability index is suggested and its non-linear relationship with 137Cs transfer factors to different plant species in the understorey is shown.     

137Cs vertical migration in boggy soils in the long term after the Chernobyl accident

137Cs vertical migration in boggy soils has been studied 15 years after the Chernobyl accident. The rate of vertical migration of the radionuclide is shown to be dependent on the peculiarities of formation of peatbogs, their moistening regime and soil properties. 137Cs migration in a high-land peatbog is characterized by higher intensity then in lowland or transitional peatbogs. Differences in 137Cs vertical migration are to a large extent caused by the contents in soil of exhangeable and mobile radionuclide forms. The derived experimental data that describe 137Cs distribution over the profiles of peaty soils of different type are used for parameterization of two-component convective-diffusion model. Ecological and effective half-life periods of 137Cs content reduction in the soil root layer have been calculated. A long-term prediction is given of the dynamics of the radionuclide content in the root layer of peaty soils.     

Long-term trends and variation in <Superscript>137</Superscript>Cs activity concentrations in brown trout (<Emphasis Type="Italic">Salmo trutta</Emphasis>) from Øvre Heimdalsvatn,a Norwegian subalpine lake

The Norwegian mountain lake, Øvre Heimdalsvatn, received major fallout from the Chernobyl accident in the spring of 1986. Activity concentrations of ¹³⁷Cs have been monitored annually in the brown trout (Salmo trutta) population of the lake over a 22-year period since 1986. The activity concentrations of ¹³⁷Cs in brown trout have declined over the period, although in recent years there has been little or no reduction in activity concentrations. Throughout the period, there has been considerable individual variation in ¹³⁷Cs activity concentrations. Within a single year, fish weight was the most significant factor affecting activity concentrations of ¹³⁷Cs in individual fish, although sex and age·weight were significant explanatory variables. The “size effect” was not significant during the initial period after fallout and in some recent years. During the first years after fallout, the ecological half-life of ¹³⁷Cs in brown trout was 3–4 years, but during the last decade this has increased significantly and has approached the physical half-life of 30 years for ¹³⁷Cs, suggesting a dynamic equilibrium between catchments inputs, possible remobilisation from lake sediments and lake outputs of ¹³⁷Cs.     

A long-term study of catchment inputs of <Superscript>137</Superscript>Cs to a subalpine lake in the form of allochthonous terrestrial plant material

The input of allochthonous plant material, largely terrestrial in origin, during the spring spate is a major source of primary production for montane lake ecosystems such as Øvre Heimdalsvatn and is readily incorporated into the food chain leading to fish. The transport from the lake catchment of allochthonous plant material contaminated with Chernobyl ¹³⁷Cs in 1986 was investigated from 1989 to 2008. ¹³⁷Cs activity concentrations were determined for both total samples before sorting and for the separate components in the two main tributary streams, Brurskardbekken and Lektorbekken, as well as the outflow river, Hinøgla. The total samples showed a similar long-term decline at all sites, although ¹³⁷Cs activity concentrations were generally somewhat higher in Hinøgla compared to the tributary streams. For the total samples, ecological half-lives were in the region of 4–5 years. However, there were major differences between components. The ¹³⁷Cs activity content of most components, including mosses, leaves of willow and woody material, decreased significantly over time. Lichens and juniper declined, but the relationship was not significant, while leaves of mountain birch and dwarf birch showed no obvious trend over the 20-year period.     

137Cs distribution and accumulation in the tissues of cultivated fungi (Pleurotus ostreatus)

The authors examined 137Cs accumulation and distribution in different structures and tissues of Pleurotus ostreatus cultivated under laboratory conditions. The fungi were shown to concentrate 137Cs. A higher concentrations of the radionuclides in the fungi compared to their substrate is manifested at the first stages of the fruit body formation, the maximum content of 137Cs is accumulated by fungi in the middle of bearing stage. The fungus tissues are different by their accumulative capacity as follows (ascending range): central, more dense part of the stipe < stipe < mycelium < cap < generative tissues. 137Cs accumulation in the fruit bodies depends also on the fungus size and age.     

Identification of processes governing long-term accumulation of 137Cs by forest trees following the Chernobyl accident

The regularities of ¹³⁷Cs distribution in trees (Pinus sylvestris and Betula pendula) growing in different types of forest ecosystems were investigated. High levels of heterogeneity of ¹³⁷Cs activity concentrations in different parts of the trees, resulting from their varied metabolism have been shown. The data obtained demonstrate a non-uniform character of ¹³⁷Cs distribution along the trunks, which can be explained by radio- nuclide fixation by the xylem vessel walls and by geometry changes along the tree trunk. It has been found that the radial distribution of ¹³⁷Cs in the tree trunk is dependent on the availability of ¹³⁷Cs in soil, which governs the transfer of this radionuclide via xylem sap and on the properties of the xylem. The accumulation of ¹³⁷Cs by trees was influenced by the vertical distribution and availability of ¹³⁷Cs in the soil as well as by the root biomass distribution in different soil horizons. A bioavailability factor, which takes into account the vertical distribution of radiocesium in soil, bioavailability of this radionuclide and distribution of root biomass in different soil horizons is proposed for comparative analyses of ¹³⁷Cs transfer from soil to trees in different types of forest ecosystems. Received: 8 February 2000 / Accepted: 1 December 2000     

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.     

Forecast of collective radiation dose decrease of the population of Belarus as the result of optimization of moveable potassium contents in soils contaminated by 137Cs

Results of study on an efficiency of potassium moveable content for decrease of a collective dose from 137Cs to the population of Belarus are presented. On the basis of the "cost-benefit" analysis it is shown, that expenses for decreasing averted collective dose due to increase of potassium contents on arable lands amounts to more than 80 thousand US dollars per 1 man.-Sv depending on density of soil contamination of rural districts by 137Cs. It is found that high effect (costs less than 40 thousand US dollars per 1 man.-Sv on hectare of arable land) on averted collective dose from 137Cs at cultivation of cereals can be expected at an optimization of mobile potassium contents in sod-podzolic loamy sand soils with density of 137Cs contamination more than 925 kBq/m2, sand soils--more than 1184, light loam soils--more than 629 kBq/m2.     

Changes in radiocaesium uptake and distribution in wheat during plant development: a solution culture study

Spring wheat plants were grown in a ¹³⁷Cs labelled nutrient solution, either in the presence or absence of NH₄ as a secondary N source. Between 11 and 64 days after sowing (DAS), plants were harvested on nine occasions. The plants supplied with NH₄ and NO₃ had lower root ¹³⁷Cs Activity Concentrations (AC) than those supplied with NO₃ only. Shoot AC were equal in both nutrition treatments. Shoot and root ¹³⁷Cs AC (dry weight basis) showed the same trends with plant age in both nutrition treatments. Shoot AC almost doubled between 11 and 28 DAS after which they gradually decreased concomitant with a similar decrease in K concentrations. Root AC were always higher than shoot AC and increased to a maximum at 35 DAS after which they fluctuated. Expressed on a tissue water basis, the ¹³⁷Cs AC varied less during plant age than did dry weight based AC. Furthermore, root and shoot AC expressed on a tissue water basis were almost equal. It is shown that the initial increase in ¹³⁷Cs AC in both root and shoot can largely be explained by the initial dilution of absorbed ¹³⁷Cs in the unlabelled seedling tissues. No correlation was found between K and ¹³⁷Cs distribution among ears, leaves, stems and roots in 64 old wheat plants. NH₄ as a secondary N source in a nitrate nutrient solution marginally affected ¹³⁷Cs distribution.Abbreviations AC activity concentrations - DAS days after sowing FAX no corresponding author: +3216321997     

Method of assessment of 137Cs biological availability in forest soil

A method for quantitative assessment of 137Cs availability to plants in forest ecosystems on the basis of soil properties has been developed. It is shown that the experimental dependencies of 137Cs soil-to-plant transfer factor (TFag) for fern and bilberry on the bioavailability factor calculated on the basis of soil characteristics of root layer: 137Cs exchangeability, exchangeable Ca, effective selectivity coefficient, were satisfactory described by linear function. The advantage of the proposed method is that the necessary soil characteristics can be taken from the reference literature, evaluated using empirical correlations or determined with standard agrochemical procedures.