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.     

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).     

The accumulation of radionuclides 137Cs and 90Sr by different kinds and grades legumes crops

The decision of protein problem on contaminated by radionuclides territories as a result of the accident on Chernobyl NPP is not possible without increase of the sowing areas legumes crops (peas, lupine, soybean). Introduction in agricultural manufacture of grades with a low level of accumulation radionuclides (peas--Aist, Polesskay, Gomelskay Agat; soybean--Severnaya zvezda, Mageva) will allow to receive agricultural production adequate "Republican allowable levels of the contents of 137Cs and 90Sr in agricultural raw material and forages" on arable lands at their higher density of radioactive contamination: 137Cs--1300-1480 kBq/m2 (35.0-40.0 Ci/km2): 90Sr--18.5-37.0 kBq/m2 (0.50-1.00 Ci/km2).     

Prognosis of accumulation of 137Cs and 90Sr in the herbage of the main types of the Belarus Polessje meadows using agrochemical soil properties

On the basis of long-term stationary experience it was established that the minimum accumulation quantities for 137Cs and 90Sr in the herbage of the dry, lowland and flood-plain types of the Belarus Polessje meadows contaminated with Chemobyl radionuclides are determined when the optimum of basic agrochemical soil properties is achieved with application of the scientifically reasonable protective measures. For remote prognosis of radionuclide contents in natural and cultural meadow herbage the use of transfer factors (TFa, (Bq/kg)(kBq/m2)) based on the complex agrochemical parameters--agrochemical cultivation soil index (Icd) and basic saturation degree (V, %), which take into account some soil characteristics simultaneously, is a streamlined approach. This paper provides the equations of linear and multiple regressions, which can be used to calculate the transfer factors for 137Cs and 90Sr uptake and the herbage contamination degree for the main types of meadows of the region, that will allow reducing the volume of forage production (hay, green bulk), which is not adequate to established permissible levels: "Republican allowable levels of the contents of 137Cs and 90Sr in agricultural raw material and forages".     

Dynamic study of the cytogenetic effects in blood lymphocytes from humans living in the Chernobyl Atomic Energy Station exclusion zone without permission

The cytogenetic examination of a group of people, self-residing in ChNPP Exclusion Zone with soil contamination density 137Cs 74-477 kBq/m2, 90Sr 33-289 kBq/m2, 238, 239 + 240Pu 1.5-10.0 kBq/m2, was conducted in 1998-1999 and also 2001. It is shown, that after 12-15 years of the accident the level of chromosome damages in Zone self-residents' lymphocytes detected by a routine analysis is higher then at the residents of control Yagotin district, Kiev region and comes to a plateau. Lymphocytes with multiple chromosome damages are detected. The probability of its transuranium elements induction which are present in the Zone is discussed at present.     

Radioecological situation at the villages of the Techa river

The Techa river was contaminated in 1949-1956 from the nuclear enterprise "Mayak". The investigations were carried out in flood plain of the Techa river in 1992-2001. 90Sr and 137Cs stores were calculated in the soil-vegetation cover. There is uneven character of the spatial radionuclides contamination of the investigated area. The store with 90Sr changes from 25 to 930 kBq/m2 (0.7-25.0 Ci/km2) and that with 137Cs--from 30 to 1700 kBq/m2 (0.8-46.0 Ci/km2). In the preriver-bed soils the ratio 90Sr/137Cs increases with further from discharge point. Individual effective dose was calculated for the Brodocalmak population. 90Sr was revealed in the flood plain soils of the Iset river. The contribution of the contaminated Techa river and its flood plains soils accounted for as by incorporated radionuclides as background gamma-radiation does not exceed 0.13-0.17 mSv/yr if the contaminated Techa river utilization is limited. In other case the contribution of the contaminated Techa river increases to 1.6-3.0 mSv/yr. These values exceed international safety norms.     

The optimization of the soil acidity of agrocenosis contaminated 137Cs and 90Sr: threshold parameters

During the field researches were determined the differences between agrochemical optimum of the acidity of the Sod-podzol loamy sand soil, which provides high productivity of the crops and the pH-value, which provides the minimal accumulation of 137Cs and of 90Sr by the biomass (the ecological optimum). On the average for the majority of the agricultural plants the minimal accumulations of 137Cs and of 90Sr are noticed under pHKCl 6.7, which is higher than agrochemical optimum on 0.7. The efficiency of liming under the discrimination of 137Cs and of 90Sr is much higher in soils with low values of pH. On the average, in crop rotation due to decreasing of the acidity in the soil from 4.9 to 5.9 pHKCl, the crop yield has grown on 9%, 137Cs contents has decreased on 16.7%, 90Sr--on 23.7%. The further decreasing of the soil acidity (from 5.9 to 6.8 pHKCl) was poorly effective: the productivity didn't change essentially. The transfer of 137Cs decreased on 8.9% and of 90Sr on 8.4%.     

Radioecological research of the Irtysh-River's and Ob-River's water, base and flood depositions

The radioecological research of Irtysh-river and Ob-river was held. The content of 137Cs in Irtysh water was compounded 0.62-1.23 Bq/m3, in Ob-- 0.24-0.27 Bq/m3, and the one of 90Sr in Irtysh-- 10-20 Bq/m3, and in Ob-- 5-10 Bq/m3, that is much lower than the permissible sanitary-hygienic norms for the population. The 137Cs stores density on Irtysh-river input lease was compounded 2.7 kBq/m2, is almost in 11 times slashed downstream and is peer 245 kBq/m2 before the Irtysh-river lockin. The 90Sr stores density also was slashed in surveyed leases with 212 down to 106 Bq/m2. Two variants of integrated stores of 137Cs and of 90Sr in flood of the Irtysh-river was held. The balance calculation of annual radionuclides sinks confirms the dominant amount of 137Cs and of 90Sr in downstream Ob-river leases acts now on the Ob's sleeve, instead of from the Irtysh-river as it was supposed earlier. The 137Cs medial annual inflow from the Ob's sleeve almost is in 2 times, and the 90Sr inflow is in 2.3 times more, than are acts from Irtysh-river sleeve.     

The agronomical and radiological estimation of application of different kinds and dozes of organic fertilizers at improvement waterless valley types meadows contamination 137Cs and 90Sr

On the basis of agronomical, economic and radiological estimations of results of long-term researches with organic fertilizers (peat, sapropel, manure, mixes manure and peat) it is established, that is effective at improvement of the waterless meadows on sod-podsolic sandy soils contaminated by radionuclides to bring in 40-60 t/ha mixes manure and peat or covering the manure, on a background liming and mineral fertilizers (level of profitability--4.8-8.7%), providing reception of the maximal increase of a crop (6.0-7.5 t/ha of hay) and decrease to 10 times of size of transfer factors of 137Cs and to 3.0 times 90Sr in a crop of long-term cereal herbs (size of the prevented collective doze, deltaD - 0.0060-0.0065 man-Sv per one year; cost of the prevented collective doze, deltaepsilon--11500-13000 $ on 1 man-Sv annually. The application of 40 and 60 t/ga of peat and sapropel in the pure state on a background liming and mineral fertilizers is not expedient, as cost of additional production does not cover total expenses for their entering (level of profitability--20-32.0%), the and cost of the prevented collective doze exceeds 20000 $ US per 1 man-Sv annually.     

Horizontal migration of 137Cs with water erosion of soils

The results of research of horizontal migration of 137Cs with soils water erosion are presented. It was found that quantitative parameters of 137Cs migration depended on radioactive pollution of cultivated soil layer, volume of water erosion of soils and character of usage of sloping lands. Activity of 137Cs in lower parts of slopes was 37-295 kBq/m2 higher than in the middle and apex parts of slopes. Increase in 137Cs activity varied from 10 to 18 percent in accumulation zone as compared to outwash zone with soil losses 5.0 t/ha and from 17 to 35 percent with soil losses 5.1-10.0 t/ha and from 30 to 127 percent with soil losses 10. 1-20.0 t/ha.     

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

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

Microbial biomass and growth kinetics of microorganisms in chernozem soils under different farm land use modes

The carbon content of microbial biomass and the kinetic characteristics of microbial respiration response to substrate introduction have been estimated for chernozem soils of different farm lands: arable lands used for 10, 46, and 76 years, mowed fallow land, non-mowed fallow land, and woodland. Microbial biomass and the content of microbial carbon in humus (Cmic/Corg) decreased in the following order: soils under forest cenoses-mowed fallow land-10-year arable land-46- and 75-year arable land. The amount of microbial carbon in the long-plowed horizon was 40% of its content in the upper horizon of non-mowed fallow land. Arable soils were characterized by a lower metabolic diversity of microbial community and by the highest portion of microorganisms able to grow directly on glucose introduced into soil. The effects of different scenarios of carbon sequestration in soil on the reserves and activity of microbial biomass are discussed.     

The effect of internal exposure to 90Sr on hematopoietic stem cells in CBA mice

After acute intake of 90Sr the changes of d-9 CFUs number in mice (CBA) bone marrow, spleen and peripheral blood were investigated. The obtained results indicated similar quantitative changes in bone marrow and spleen CFUs on exposure to the 90Sr when radiation doses did not cause the decrease in life-time (1.11 kBq/g). Sarcomogeneous doses of 90Sr (29.6 kBq/g) resulted in drastic changes of hemopoietic system: spleen haematopoiesis activation and suppression of bone marrow functions. On the first day after 90Sr injection (29.6 kBq/g) the increase in number of peripheral blood CFUs (circulating pool) was observed.     

Evaluation of parameters of radionuclide transition from soil particles and plant components of the upper layer of turf to cow's milk under pasture conditions

An experiment was conducted on feeding lactating cows with soil and turf additives contaminated with both 137Cs and 90Sr of the Chernobyl origin. The radionuclides transfer coefficients (%) in the food chain were for soil additives: for 137Cs--0.02 +/- 0.006, for 90Sr--0.01 +/- 0.002; for turf additives: for 137Cs--0.02 +/- 0.005, for 90Sr--0.06 +/- 0.035. Regarding 90Sr, there is no significant tendency to higher transfer rate for the radionuclide from turf component compared to that for soil component. A contribution of soil component as well as turf component of soil was evaluated as an additional source of milk contamination while grazing cattle. It was concluded that the contribution is not pronounced at the remedial period after the accident (approximately 3% from total activity consumed with ration) and it can be rejected in cattle breeding practice. The results achieved can be used for prediction of radionuclides concentrations in milk produce in cattle breeding under industrial contamination of agricultural lands.     

The content in soil and the mobility of artificial radionuclides in the region of the regional radioactive waste storage situation

The objects of researches are the soil and wild vegetation in the region of the radioactive waste storage situation. In result of monitoring it was recognized 137Cs unlike 90Sr did not spread out of storage territory in spite of trench destruction and migration of radionuclides with surface and ground waters. The forms of 137Cs, 90Sr and natural radionuclide 226Ra in soils and coefficients of 90Sr accumulation for the different kinds of plants growing at the territory of storage and 50-m zone around it were researched. The low specific activities of mobile forms of 90Sr were recognized for samples of soils selected from lowland by the terrace. The considerable differences were found for specific activities of radionuclides for different soil layers. Essential irregularity of soil surface and vegetation contamination at the test points disposed at a short distances from each other also was found. The interpretation of obtained results is presented.     

Radiostrontium contamination of soil and vegetation within the Semipalatinsk test site

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

The main radionuclides and dose formation in fish of the Chernobyl NPP exclusion zone

The results of the researches of spices-specificity, accumulation dynamics and distribution of 90Sr, of 137Cs and of transuranic elements in fish of the Chernobyl NPP exclusion zone are analysed. The data of estimations of absorbed doze rate from incorporated radionuclides for pray fish and predatory species are given. For the fish from the lake of the left-bank floodplain of the Pripyat River the increase of 90Sr specific activity is registered which is presumably connected with the dynamics of the physical-chemical forms of the radionuclide in soils and their wash out in water bodies from the catchment basin. Now about 90% of internal dose rate of fish from closed aquatic ecosystems within the Chernobyl NPP exclusion zone is caused by 90Sr incorporation.     

Reconstruction of 90Sr intake for breast-fed infants in the Techa riverside settlements

The Techa River (Southern Urals, Russia) was contaminated as a result of radioactive releases by the Mayak plutonium production facility during 1949-1956. The persons born after the onset of the contamination have been identified as the "Techa River Offspring Cohort" (TROC). The TROC has the potential to provide direct data on health effects in progeny that resulted from exposure of a general parent population to chronic radiation. The purpose of the present investigation is the estimation of (90)Sr intake from breast milk and river water in the period from birth to 6 months of life, necessary for an infant dose calculation. The investigation is based on all available data concerning radioactive contamination due to global fallouts and Mayak releases in the Southern Urals where extensive radiometric and radiochemical investigations of human tissues and environmental samples were conducted during the second half of the twentieth century. The strontium transfer factor from mother's daily diet to breast milk was estimated as 0.05 (0.01-0.13) d L(-1). Based on this transfer factor and data on (90)Sr water contamination, the average total (90)Sr intake for an infant born in the middle Techa River region was found to be equal to 60-80 kBq in 1950-1951. For the same period, calculations of (90)Sr intake using ICRP models gave values of 70-100 kBq. From 1952 onwards, the differences in intakes calculated using the two approaches increased, reaching a factor of 2-3 in 1953. The Techa River data provide the basis for improving and adapting the ICRP models for application to Techa River-specific population.     

The cytogenetic consequences of chronic irradiation in rodent populations inhabiting the Eastern Urals Radioactive Trace zone

In bone marrow cells of rodents (Apodemus (Sylvaemus) uralensis Pall., 1811, Apodemus agrarius Pall., 1771) inhabiting the Eastern Urals Radioactive Trace (EURT) zone (Kyshtym radiation accident 1957) and adjacent areas of Urals, the chromosome instability and 90Sr accumulation in bones were investigated. Intensive mutagenic process in both species from impact plots (the soil pollution by 90Sr 2322-16690 kBq/m2) was found. Significant positive correlation of aberrant cells frequencies and 90Sr was shown. Possible causes of the lack of resistance to long-term mutagenic factor (over 100 generations since 50 years from the accident) such as migration of animals and specific configuration of the EURT zone (narrow extended territory with sharply falling gradient of radionuclide pollution), which considerably decrease the probability that certain changes will be fixed and inherited in a series of generations of rodents, are discussed.     

The characteristics of 90Sr accumulation and elimination in residents of the Urals region in the period of 1957-1988

A number of radiation accidents occurred at the "Mayak" plutonium production complex (Southern Urals, Russia) in 1950-60s that resulted in environmental contamination of large territories in the Southern and Middle Urals with long-lived radionuclides (90Sr, 137Cs). The results of long-term radiological monitoring were compiled into special databases at the Urals Research Center for Radiation Medicine, which allow the study of 90Sr behaviour in the environment and its accumulation in the human body. Retrospective analysis of the data on postmortem measurements of 90Sr in bones performed on residents of the Urals region over 1957-1988 were conducted for the first time. A time-dependence of 90Sr accumulation in the human body upon its density in soils was observed. Age and gender characteristics of 90Sr retention in bones were studied. It was shown that the levels of 90Sr in residents of large territories north and north-east of Chelyabinsk region, and of bordering territories of Sverdlovsk region were several times higher than the average values for the Russian Federation. Based on the measurements the direct dependence of 90Sr content in the skeleton on 90Sr density in soils was observed 30 years after the 1957 accident (the so called "Kyshtym accident"). However, for individual settlements this dependence may be weakened as a result of the influence of different biological and social factors. No influence of gender on 90Sr accumulation in the skeleton was found in the study. The analysis of age characteristics of 90Sr accumulation in bone, as influenced by skeleton growth and maturation, showed maximal levels of 90Sr from global fallout to be accumulated in bones of the persons born in 1949-1955.