Prussian Blue to reduce radiocaesium accumulation in fish in lakes affected by the Chornobyl accident.

Fish in lakes situated within the Chornobyl exclusion zone have been highly contaminated since the accident and have not been utilized as food for humans. In the present study, field experiments with less-contaminated silver Prussian carp (Carassius gibelio (Bloch, 1782)) caged in contaminated lake within the Chornobyl exclusion zone was performed from June to October 2021 to investigate the effectiveness of clean feed containing potassium ferric hexacyanoferrate (KFCF) KFe[Fe(CN)6], a kind of Prussian Blue as a countermeasure to reduce 137Cs accumulation in fish. The addition of clean feed containing 0.1% or 1% KFCF resulted respectively in 2.4 ± 0.4 or 4.2 ± 0.7 times lower activity concentration of 137Cs in muscle tissue of the carp compared to control fish with clean feed without KFCF and in 7-16 or 12-27 times lower activities compared to fish without additional clean feeding. After 18 weeks exposure, 137Cs levels in all the caged fish except for the control group were below the European permissible level (600 Bq kg-1) for consumption. In contrast, KFCF did not affect the intake of 90Sr in fish, although additional feed increased the growth rate and thereby accumulation in bone tissues. Hence, the use of clean feed containing KFCF is judged to be an effective and inexpensive countermeasure to reduce the 137Cs contamination of edible fish muscles.

Variability of activity concentrations and radial distributions of 137Cs and 90Sr in trunk wood of Scots pine and Silver birch.

This study analyzes the variability of 137Cs and 90Sr concentrations in wood and their radial distributions in the trunks of Scots pine and Silver birch trees in the small uniformly contaminated forest stands in the Chornobyl Exclusion Zone. Concentrations of both radionuclides follow a lognormal distribution with a large scatter of values measured in the trees within the stands (GSD ranges from 1.6 to 2.0). No correlation was found between the concentrations of the two radionuclides measured in individual trees, or between their concentrations and tree diameter. The average 137Cs and 90Sr Tag were 8.4 × 10-4 m2 kg-1 and 8.8 × 10-3 m2 kg-1 for pine, respectively, and 9.3 × 10-4 m2 kg-1 and 1.1 × 10-2 m2 kg-1 for birch, indicating a much higher availability of 90Sr for uptake by the studied species. For 137Cs, the Tag values are within the range recommended by the IAEA Handbook (IAEA, 2010), while the values for 90Sr exceed the recommended range for birch and are close to its upper value for pine. The highest concentrations of 137Cs in pine at the height of 1.3 m were measured in the youngest sapwood rings; they were lower in the rest of the sapwood and decreased further in the heartwood, but remained relatively high even in annual rings that were the heartwood at the time of deposition, suggesting sapwood-to-heartwood translocation of the radionuclide by diffusion and/or ray transport. In contrast, 90Sr concentrations increased through the sapwood from the trunk periphery in pine trees up to 80 years old and remained stable through the sapwood in older trees (except for higher concentrations in the young annual rings), but dropped to zero in physiologically inactive heartwood tissues. In most birch trees, regardless of age, 137Cs concentrations demonstrated an increasing trend from the trunk periphery towards the pith, while concentrations of 90Sr were relatively stable in the whole trunk except in the oldest annual rings, where they increased sharply, likely indicating active transport of the radionuclide to senescing tissues.

Optimising sampling strategies for emergency response: Vegetation sampling.

The lessons learned from the plant sampling campaigns implemented in the most Chernobyl affected countries are described. The variability of 137Cs activity concentrations in plants taken from a variety of sampling sites, as well as the uncertainties around the aggregated transfer factors (Tag) from soil to plants were estimated. The sampling sites covered both agricultural and natural lands in different landscapes: floodplain, plains, and watershed meadows. To determine parameters of the lognormal distribution of the 137Cs activity concentration in plants and the values of corresponding aggregated transfer factor (Tag) values, from 25 to 49 plant and soil samples were collected at each sampling site with the grid increment that varied from 1 to 10 m. The gradients of deposition i.e. monotonic changes (trends) of the contamination density conditioned by the global (in respect to study area) gradient of fallout were not observed in any of the study sites. Therefore, the variability of radionuclide contamination density (and activity concentrations in the soil) within the study sites were determined by only random factors such as microheterogeneity of radioactive deposition in a sampling point. The mean standard deviation of the logarithms of 137Cs activity concentrations in plants sampled in all such sites and the corresponding transfer factors were similar for all sites studied and were not dependent on the mean soil contamination density at the site, the type of radioactive fallout and the vegetation type. The values of the average standard deviation of the 137Cs activity concentration logarithms in plants and the corresponding transfer factors for the vegetation sampling area ≥1 m2 and the relative activity measurement uncertainties ≤10% were estimated as 0.4 ± 0.1 and 0.5 ± 0.1, respectively. A new simple method for optimization of the number of linked (conjugated) plant and soil samples as well as estimates of the activity concentration and transfer factor uncertainties when measuring composite samples were proposed. Based on the results of these studies, the recommendations were made to the sampling of plants for radionuclides.

Monitoring in animal breeding in response to nuclear or radiological emergencies: Chernobyl experience.

The main techniques of animal product sampling used in different time periods after the Chernobyl accident are summarised and lessons learned from this analysis are presented. It was shown that simple instruments for measurement γ-radiation in the environment can also be effectively implemented for measurement of γ-emitters in animal products even though these were not originally developed to measure radioactivity in food. The lessons learned related to the major tasks of the monitoring such "what to sample", "where to sample" and "when to sample". The role and example of application of supplementary data on radionuclide of concern properties for sampling planning are also discussed. Based on the statistical analysis of the data obtained in the affected settlement it was shown that radionuclide concentration in the animal products can be fitted by the log-normal distributions whilst the dispersion of the logarithms of the activity 137Cs concentrations in milk is not dependent on the local settlement specific factors. Based on these findings the novel approach for justification of the number of samples that should to be taken to obtain the GM estimate with predefined precision for given variability of the data is suggested.

Current radiological situation in areas of Ukraine contaminated by the Chornobyl accident: Part 2. Strontium-90 transfer to culinary grains and forest woods from soils of Ivankiv district.

Some of the highest 90Sr activity concentrations recorded beyond the Chornobyl Exclusion Zone occur in the Ivankiv district of Ukraine, located approximately 50 km south of the power plant, an area which nonetheless remains important for agricultural production. Although characterized by soils with low exchangeable calcium values, which can enhance the bioavailability of certain radionuclides, information on the transfer of 90Sr to food crops and trees in the region has remained limited to date. Analysis of 116 grain samples (wheat, rye, oat, barley or Triticale) collected from fields in 13 settlements in the region between 2011 and 2019 revealed 90Sr and 137Cs activity concentrations above Ukrainian limits in almost half of those samples, with annual averages exceeding this limit in four of those nine years (most recently in 2018) and with no clear evidence for a declining trend over time. Analysis of paired sandy soil samples from the same fields yielded concentration ratios for transfer of 90Sr from soils to grains that were on average 3 times higher than that specified by the IAEA. In addition, three quarters of wood samples collected from the trunks of trees (primarily pines) from 12 locations in the same district between 2015 and 2019 contained 90Sr activity concentrations in excess of the Ukrainian limits for firewood (60 Bq/kg), with levels more than four times that limit at one location and again no evidence for decline over time. A single sample of ash collected from a domestic wood-burning oven in the district contained 90Sr at a level 25 times higher than in the most contaminated wood sample collected in this study. Overall these results reveal additional facets of the ongoing legacy of Chornobyl contamination within the Ivankiv district, and the diversity of pathways by which local residents may be exposed to radionuclides. They also highlight the dangers associated with the current lack of routine and comprehensive environmental and food monitoring programs within the region, especially at a time in which the use of locally-sourced wood for biomass energy generation is set to expand markedly.

Effects of radiation on radial growth of Scots pine in areas highly affected by the Chernobyl accident.

The effects of radiation on radial growth of Scots pine (Pinus sylvestris L.) affected by the Chernobyl accident were studied at five sites with different deposition levels. The study sites were chosen along a high gradient of depositions at the distance of a few hundred meters in the forests with similar forest characteristics. Air dose rates varied at the sites from the background values up to 30 µGy h-1 as of December 1, 2016. Scots pine trees exposed to sub-lethal doses of 8.6-13.2 Gy at the "Red Forest" site did not demonstrate deviations in formation of annual rings 30 years after the Chernobyl accident compared to trees with lower doses and control trees. Variation with time in annual rings thickness did reveal that the effect of radiation in trees growing at the sites with different contamination not detectable in 1986 and 1987. Conversely, the effects were clear observed in a later period in 1989-1991, i.e. 3-5 years after the accident. Until 2000, there were statistically significant differences in the annual rings growth rates of Scots pine trees exposed to external absorbed dose rates of 4.4-6.7 mGy h-1 as estimated for June 1, 1986 (or 19.5-30.0 µGy h-1 as of December 1, 2016) compared with the trees of the other sites studied. The results comply with the conclusions from research with acute pine exposure conducted in the Kyshtym area in 1975-1984.

Optimising sampling strategies for emergency response: Soil sampling.

The novel approach for optimising soil sampling strategies in areas affected by radionuclides is suggested. Major factors influencing the efficiency of soil sampling strategies, including (number of samples, sampling area size, sampling depth and spatial resolution of the sample sites are examined to provide optimisation of the soil sampling plan. The experimental field studies to validate the suggested approach were performed in 25 sampling units ranging from 1.2 × 1.2 m to 60 × 60 m size. The sampling units were selected on arable farmlands, natural meadow and former agricultural land), as well as coniferous and deciduous forests with contamination density of 137Cs ranging from 2.8 kBq·m-2 to 24.5 MBq·m-2. The studied areas were contaminated by both the global fallout and the Chernobyl radioactive particles of different types. To determine the values of standard deviation of the log of the soil contamination density of 137Cs, 25 to 256 soil samples were collected with an increment of 0.07-10 m within each sampling unit. It was found that the values of standard deviation of the log of the soil contamination density of 137Cs were not dependent on the mean contamination density, the type of radioactive deposition and the landscape features. The mean value of standard deviation calculated for all sites studied was estimated as 0.44 ± 0.15 and 0.30 ± 0.10 for the sampling area 0.001 m2 (∅37 mm) and 0.005 m2 (∅80 mm) at the relative measurement uncertainties lower than 10% (CI = 95%). Concentrations of 137Cs in the soil samples were statistically independent when sampling points were situated at a distance larger than 1 m one from each other. A simple method was developed for assessing minimum sample sizes required for estimation of the median or the geometric mean of radionuclide soil contamination with a relative uncertainty set by the user. The approach was also suggested for estimation of the uncertainty of soil contamination for the case of composite samples. The approach was implemented in the Ukrainian national requirements for assessment of quality of the soil.

Validation of a fuel particle dissolution model with samples from the Red Forest within the Chernobyl exclusion zone.

The contamination in the near exclusion zone of the Chernobyl nuclear power plant (ChNPP) with 90Sr, 238-240Pu and 241Am is associated with irradiated nuclear fuel particles. Fit for purpose models enabling long term prediction of mobility and bioavailability of particle-associated radionuclides are crucial for radiation protection of humans and the environment, as well as for planning of remediation measures and future land use. In the present work, a dynamic fuel particle dissolution model developed in 1999-2002 is described and validated using data based on sampling in 2015. The model is based on the characterization of the radionuclide source term of the waste in a shallow sub-surface radioactive waste storage, trench #22, in the Chernobyl Pilot Site (CPS) located in the Red Forest, 2.5 km west of the ChNPP, as well as the description of physical and chemical properties of the fuel particles and subsequent radionuclide leaching into the soil solution. Transformation rate constants of the fuel particle dissolution model related to topsoil, radioactive waste trench and submerged materials, and drained cooling pond sediments, should largely control the mobility and bioavailability of radionuclides (e.g., solubility in the soil, migration to groundwater and transfer to plants). The predicting power of the Chernobyl fuel particle dissolution model with respect to radionuclide leaching dynamics was validated using samples from the same experimental site, showing that predicted particle leaching and subsequent mobility and bioavailability were within 46 ± 3% of the observed data. Therefore, linking source- and release-scenario dependent characteristics of radioactive particles to their potential weathering can provide information that can be implemented in impact assessments models for existing contaminated areas as well as for future events.

Current radiological situation in areas of Ukraine contaminated by the Chernobyl accident: Part 1. Human dietary exposure to Caesium-137 and possible mitigation measures.

This study reports for the first time temporal trends for the period of 2011-2016 in 137Cs content in cow's milk originating from private farms and households of 14 settlements located in the territories of the Rivne region, Ukraine. These areas are still radioactively contaminated as a result of the accident at the Chernobyl Nuclear Power Plant (ChNPP) in 1986. In 2016, the average 137Cs activity concentration in milk exceeded the Ukrainian Permissible Level (PL) for adults of 100 Bq/l in samples from 6 settlements and the PL for children of 40 Bq/l in 8 settlements, reaching activity concentration of around 500 Bq/l in some samples. Estimated annual effective doses calculated utilizing two different methodologies were in the range of 1.4-2.6 mSv/year and 1.2-1.8 mSv/year, respectively. The estimated effective period of milk semi-purification (T1/2_eff) from 137Cs in these settlements was in the range from 8 to 17 years. The estimated ecological period of milk semi-purification (T1/2_eco) from 137Cs was in the range from 11 to 36 years. The optimization of the remedial actions strategy for investigated settlements exposed to an effective dose above 1 mSv/year (as estimated in 2016) has shown that a diversity of measures can decrease effective dose for a representative person to below 1 mSv/year. Such measures include application of Ferrocyn to cows, mineral fertilization of potato fields, information campaigns on consumption of wild mushrooms and other forestry products, and feeding pigs with uncontaminated fodder. The total costs of such measures are estimated to be about 71,000 Euro per year for the combined population (8336 inhabitants) of the six villages investigated in this study that showed the highest median residual 137Cs activity concentrations in milk, with a subsequent decrease in cost in the future. This would result in an averted collective dose of 11 man-Sv, at an average cost of 6.5 kEuro/man-Sv averted. In the absence of governmental programs for implementation of necessary protective measures to reduce radiological risks to impacted populations, the exceedance of PL for the activity concentration of 137Cs in cow's milk for adults of 100 Bq/l in the Chernobyl-affected areas of Ukraine could persist for many more years - until at least 2040.

Modification of (137)Cs transfer to rape (Brassica napus L.) phytomass under the influence of soil microorganisms.

After nuclear accidents, such as those experienced in Chernobyl and Fukushima, microorganisms may help purify contaminated soils by changing the mobility of radionuclides and their availability for plants by altering the physical and chemical properties of the substrate. Here, using model experiments with quartz sand as a substrate we investigate the influence of microorganisms on (137)Cs transfer from substrate to plants. The highest transition of (137)Cs from substrate to plants (50% increase compared to the control) was observed after Brassica napus L. seeds were inoculated by Azotobacter chroococcum. The best results for reducing the accumulation of (137)Cs radionuclides (30% less) were noted after the inoculation by Burkholderia sp.. Furthermore, Bacillus megaterium demonstrated an increased ability to accumulate (137)Cs. This research improves our prediction of the behavior of radionuclides in soil and may contribute towards new, microbiological countermeasures for soil remediation following nuclear accidents.

[Effect of soil microflora on 137Cs transition to plants].

The impact of certain types of microorganisms on 137Cs transfer from the substrate into the plant was analyzed in the experiment on artificial mediums. It was found that certain types of microorganisms could either reduce or increase the ratio of 137Cs transfer from the substrate to the plant. It is shown that this property is independent of the localization of the microorganism on the surface of the root, for all the analyzed bacteria belonging to the rhizospheric group. Azotobacter chroococcum UKM B-6003 stimulated the radionuclide transfer to plants up to 1.5 times, while the best bacteria for reducing its accumulation is Burkholderia sp IMER-B1 -53 - 1.3 times in comparison with the control. It was shown that the strain Bacillus megaterium UKM B-5724 from the collection of the Institute of Microbiology and Virology of NASU has a high ability to accumulate radionuclides.

Translocation of (125)I, (75)Se and (36)Cl to edible parts of radish, potato and green bean following wet foliar contamination under field conditions.

Specific translocation factor values (ftr) for (129)I, (79)Se and (36)Cl following foliar transfer are still missing from the IAEA reference databases. The translocation of the short-lived isotopes, (125)I, (75)Se, and (36)Cl, to radish, potato and green bean edible parts was measured under field conditions following acute and chronic wet foliar contamination at various plant growth stages in the absence of leaching caused by rain. The translocation factors obtained for (125)I ranged from 0.8 to 2.6% for radish, from 0.1 to 2.3% for potato and from 0.1 to 2.6% for bean. The translocation factors obtained for (75)Se ranged from 6.3 to 21% for radish, from 1.6 to 32.6% for potato and from 7.7 to 22.8% for bean (values similar to Cs or even higher). The translocation factors obtained for (36)Cl were close to those for (75)Se and ranged from 4.3 to 28.8% for radish, from 0.5 to 31.5% for potato and from 4.3 to 16.3% for bean. Iodide showed the lowest apparent mobility because of its preferential fixation in or on the leaves and a significant amount was probably volatilized. Selenite internal transfer was significant and possibly followed the sulfur metabolic pathway. Chloride was very mobile and quickly diffused throughout the plant. The translocation factors varied with the growth stage and depended on the development state of the edible tissue and its associated sink strength for nutrients and assimilates. For radish, translocation was high during the early vegetative stages. For potato, wheat and bean, a major peak in translocation was seen during the flowering growth stage and the concomitant growth of potato tubers. An additive effect of successive contamination events on translocated elements was shown in radish but not in bean and potato. The highest translocation value obtained for an acute contamination event was shown to be an adequate, conservative indicator of chronic contamination in absence of specific values. Due to the absence of rain leaching during the experiment this study probably provides translocation values among the highest that could be recorded.

[Qualitative composition of dominating forms of microorganisms isolated from radionuclide contaminated soil and their ability to accumulate 137Cs].

Qualitative composition of the dominating forms of microorganisms isolated from radionuclide contaminated soils has been studied. The ability to accumulate 137Cs by freshly isolated species and collection cultures that were not adapted to the presence of the radionuclide has been analyzed. It is shown that among the analyzed microorganisms the greatest ability to accumulate the radionuclide is inherent in the collection culture Bacillus megaterium UKMV-5724.

[Contamination of agricultural production with 90Sr in Ukraine at the late phase of the Chernobyl accident].

The specific activity of 90Sr in milk and vegetables for the last 15 years does not exceed the permissible level in Ukraine outside the Chernobyl exclusion zone. Exceeding the acceptable level of 90Sr is registered only in food grain. Specific activity of 90Sr in grain, which is produced in the high contaminated areas of the Kiev region, nowadays may reach 60-70 Bq/kg, which exceeds the permissible level of 20 Bq/kg for bread-grain. The part of 90Sr activity in the biologically available form has reached its maximum values for the post-accidental period due to the fuel particle dissolution. Contamination of grain with this radionuclide has slowly decreased in recent years. Values of concentration ratios and aggregated transfer factors of 90Sr from soil to rye, oat and winter wheat grain are inversely proportional to the exchangeable calcium content in soil. The transfer factors and dependences are in good accordance with those that have been obtained in our previous works and with generalized data of the IAEA for sandy soils. Application in Ukraine of such countermeasures as liming, fertilizing and manuring makes it possible nowadays to produce grain that meets the requirements of hygienic regulations on the 90Sr content in bread-grain.

Translocation of 125I, 75Se and 36Cl to wheat edible parts following wet foliar contamination under field conditions.

Apart from radiocaesium and radiostrontium, there have been few studies on the foliar transfer of radionuclides in plants. Consequently, specific translocation factor (ftr) values for (129)I, (79)Se and (36)Cl are still missing from the IAEA reference databases. The translocation of short - lived isotopes, (125)I and (75)Se, and of (36)Cl to wheat grain were measured under field conditions following acute and chronic wet foliar contamination at various plant growth stages in the absence of leaching caused by rain. The translocation factors ranged from 0.02% to 1.1% for (125)I (a value similar to Sr), from 0.1% to 16.5% for (75)Se, and from 1% to 14.9% for (36)Cl. Both (36)Cl and (75)Se were as mobile as Cs. The phenomenological analysis showed that each element displayed a specific behavior. Iodide showed the lowest apparent mobility because of its preferential fixation in or on the leaves and a significant amount probably volatilized. Selenite internal transfer was significant and possibly utilized the sulphur metabolic pathway. However bio - methylation of selenite may have led to increased volatilization. Chloride was very mobile and quickly diffused throughout the plant. In addition, the analysis underlined the importance of plant growth responses to annual variations in weather conditions that can affect open field experiments because plant growth stage played a major role in ftr values dispersion. The chronic contamination results suggested that a series of acute contamination events had an additive effect on translocated elements. The highest translocation value obtained for an acute contamination event was shown to be a good conservative assessment of chronic contamination if data on chronic contamination translocation are lacking. The absence of rain leaching during the experiment meant that this investigation avoided potential radionuclide transfer by the roots, which also meant that radionuclide retention on or in the leaves was maximized. This study was therefore able to obtain accurate translocation factors, which are probably among the highest that could be recorded.

[Effects of chronic irradiation of Scots pine (Pinus sylvestris L.) in Chernobyl exclusion zone].

The quantitative "dose rate-effect" dependences are presented for the cytogenetic damages in the seedlings and apical meristem of Scots pine growing in the Chernobyl zone. The specific patterns of dynamics of formation of the morphological effects in the studied species are considered for the conditions of the internal and external chronic irradiation. The correlation dependencies are established for the irradiation effects appearing at the morphological and cell level. The assumption concerning the mechanism of the morphological changes formation is done.

Transfer of Cl from herbage into tissues and milk products of dairy cattle and pigs.

Cl-36 is an important component of nuclear waste. The concentrations of stable chlorine (Cl) in pig and cow tissues were measured to provide information which can be used to parameterize models of (36)Cl transfer into agricultural animals. The concentration of stable Cl in cows' milk was 1.0 +/- 0.2 g L(-1), in cow muscle it was 0.7 +/- 0.2 g kg(-1) wet mass (wm) and in pig muscle 0.4 +/- 0.1 g kg(-1) wm. The concentration of stable Cl in cow and pig liver was 0.9 +/- 0.3 g kg(-1) wm, which was about two-fold higher than that in the kidney and lung. Due to homeostatic control, stable Cl concentrations in animal tissues are not related to the amount ingested daily in herbage at intake rates in the normal physiological range of up to 188 g day(-1) for cows and up to 40 g day(-1) for pigs. Therefore, the commonly used transfer coefficient is not suitable for use in quantifying the transfer of (36)Cl to milk and meat. Since the metabolism of stable Cl and (36)Cl in an animal's body is identical, the average equilibrium ratios of (36)Cl to stable Cl in the daily ration ((36)Cl (g kg(-1))/Cl (g kg(-1))) and animal tissues will be the same. We therefore conclude that the average equilibrium Cl isotopic ratio in the dietary daily intake should be used to predict the contamination of meat and milk with (36)Cl.

Radiochlorine concentration ratios for agricultural plants in various soil conditions.

Long-term field experiments have been carried out in the Chernobyl exclusion zone in order to determine the parameters governing radiochlorine ((36)Cl) transfer to plants from four types of soil, namely, Podzoluvisol, Greyzem, Phaeozem and Chernozem. Radiochlorine concentration ratios (CR=concentration of (36)Cl in the fresh plant material divided by its concentration in the dried soil in the upper 20 cm layer) were obtained in green peas (2.6+/-0.4), onions (1.5+/-0.5), potatoes (8+/-1), clover (90+/-26) and ryegrass (158+/-88) hay, oat seeds (36+/-23) and straw (305+/-159), wheat seeds (35+/-10) and straw (222+/-82). These values correlate with the stable chlorine values for the same plants. It was shown that (36)Cl plant/soil CR in radish roots (CR=9.7+/-1.4) does not depend on the stable chlorine content in the soil (up to 150 mgkg(-1)), soil type and thus, that stable chlorine CR values (9.4+/-1.2) can also be used for (36)Cl. Injection of additional quantities of stable chlorine into the soil (100 mgkg(-1) of dry soil) with fertilizer does not change the soil-to-plant transfer of (36)Cl. The results from a batch experiment showed that chlorine is retained in the investigated soils only by live biota and transfers quickly (in just a few hours) into the soil solution from dry vegetation even without decomposition of dead plants and is integrated in the migration processes in soil.

Transfer of chlorine from the environment to agricultural foodstuffs.

The factors governing chlorine transfer from Phaeozem and Greyzem soils to various important crop species (foodstuff and forage) were determined in natural conditions in the Kiev region of Ukraine. The stable chlorine concentration ratio (CR) values were the lowest in apple (0.5+/-0.3) and strawberry (2+/-1), higher in vegetables (5+/-3), seeds (15+/-7) and reached a maximum in straw (187+/-90). The average CR values of 36Cl were estimated for the most important crops using all experimental data on 36Cl and stable chlorine transfer into plants from various soils. It was experimentally shown that boiling potatoes in water leads to an equilibrium between 36Cl specific content in the water and moisture in the cooked potato. The 36Cl processing factor (PF) for boiling various foodstuffs is equal to the ratio of water mass in the cooked foodstuff to the total water mass (in the food and the decoction). 36Cl PF for cereal flour can be estimated as 1. The 36Cl processing factor for dairy products is equal to the ratio of residual water mass in the product to initial water mass in milk. At a 36Cl specific activity in soil of 1 Bq kg-1, the estimated annual dietary 36Cl intake into human organism (adult man) is about 10 kBq. Sixty to seventy percent of the above amount will be taken in via milk and dairy products, 7-16% via meat, 14-16% via bread and bakery items and 8-12% via vegetables. The highest annual 36Cl intake, 10.7 kBq, is predicted for 1-year-old children. The expected effective doses from annual 36Cl intake are higher for younger age groups, increasing from 0.008 mSv in adults to 0.12 mSv in 1-year-old children.

Resuspension and redistribution of radionuclides during grassland and forest fires in the Chernobyl exclusion zone: part II. Modeling the transport process.

To predict parameters of radionuclide resuspension, transport and deposition during forest and grassland fires, several model modules were developed and adapted. Experimental data of controlled burning of prepared experimental plots in the Chernobyl exclusion zone have been used to evaluate the prognostic power of the models. The predicted trajectories and elevations of the plume match with those visually observed during the fire experiments in the grassland and forest sites. Experimentally determined parameters could be successfully used for the calculation of the initial plume parameters which provide the tools for the description of various fire scenarios and enable prognostic calculations. In summary, the model predicts a release of some per thousand from the radionuclide inventory of the fuel material by the grassland fires. During the forest fire, up to 4% of (137)Cs and (90)Sr and up to 1% of the Pu isotopes can be released from the forest litter according to the model calculations. However, these results depend on the parameters of the fire events. In general, the modeling results are in good accordance with the experimental data. Therefore, the considered models were successfully validated and can be recommended for the assessment of the resuspension and redistribution of radionuclides during grassland and forest fires in contaminated territories.