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.     

Radioecological investigation of the soil cover of eastern Urals State radioactive reserve and neighboring areas

The contamination levels and spatial distribution of 90Sr and 137Cs in the soil cover of the Eastern Ural State Radioactive Reserve and neighboring areas have been studied. Situated in the Chelyabinsk region, the Reserve embraces the frontal part of the Eastern Urals Radioactive Trace. This Trace emerged in 1957 as a result of the nuclear accident at the Production Association "Mayak". In the studied areas, the content of radionuclides in soils decreases exponentially as the distance from the source of contamination increases. 90Sr received by the soil cover as a result of the accident in 1957 has remained the main contaminant of the Reserve central part (97% of the total contamination). Its contribution throughout western neighboring areas reduces up to 67%, which decreases the effect of 90Sr on the environment. Within eastern neighboring areas, soil is mainly contaminated by 137Cs received as a result of the wind disseminated dried sediments from the shores of Lake Karachay (1967) that was used for dumping high-level radioactive waste. Also observed was enrichment of forest litters with this radionuclide due to current atmospheric fallout.     

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.     

Measurements of radioactivity in environmental samples from the Southern Urals

A region between Chelyabinsk and Ekaterinburg in the Southern Urals has been heavily contaminated due to operational and accidental releases from the first Soviet plutonium production facility Mayak. In 1992 and 1993, the German Federal Office for Radiation Protection organized a measuring campaign involving two Russian institutes to assist with the validation of former Soviet measurement data. The results of this measuring campaign are reported here. Environmental samples were collected from areas affected by significant radioactive releases into the Techa river, which started in 1948, and by fallout from the explosion of a fission product storage tank in 1957. Soil, sediment, water, milk and food samples were independently analysed for ⁹⁰Sr, ¹³⁷Cs and plutonium by the three institutes involved. This paper presents data on the present levels of environmental radioactivity. The highest contamination of areas accessible to the local population was found in the vicinity of the Techa river around Muslumovo. Activity concentration of floodplain samples reached up to 37 000 Bq ⋅ kg^{–1 137}Cs, 5 600 Bq ⋅ kg^{–1 90}Sr and 9.9 Bq ⋅ kg^–1 Pu. Milk and potatoes from private farms in Muslumovo showed low activity in the range from 0.7 Bq ⋅ kg^–1 to 25 Bq ⋅ kg^{–1 90}Sr. The results of the three independent measurement teams showed sufficient agreement. One Russian laboratory obtained plutonium activities that exceeded the results of the other laboratories by about 20%. Contrary to the International Chernobyl Project, there was no overestimation of ⁹⁰Sr activities in the Russian analyses. Therefore, the validity of earlier data sets acquired with same methodology and quality control can be considered a valuable basis for further assessments and for dose reconstruction in epidemiological projects. Received: 18 July 1997 / Accepted in revised form: 19 December 1997     

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

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

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.     

The Techa River Cohort: study design and follow-up methods

Residents living on the banks of the Techa River in the Southern Urals region of Russia were exposed to radioactive contamination from the Mayak plutonium production and separation facility that discharged liquid radioactive waste into this river. This paper describes the methods used to establish and follow the Extended Techa River Cohort (ETRC), which includes almost 30,000 people living along the Techa River who were exposed to a complex mixture of radionuclides, largely 90Sr and 137Cs. The system of regular follow-up allows ascertainment of vital status, cause of death and cancer incidence. With over 50 years of follow-up and over 50% deceased, the ETRC now provides a valuable opportunity to study a wide range of health effects, both early and late, associated with protracted internal and external radiation exposures. The wide range of doses allows analysis of the nature of the dose-response relationship based on internal comparisons. Other features of the cohort are the high proportion (40%) exposed under age 20, and the inclusion of both sexes. The limitations of the study include loss to follow-up due to difficulties in tracing some cohort members and migration and incomplete ascertainment of cause of death.     

Normal axial skeleton structure in common roach Rutilus rutilus (Actinopterygii: Cyprinidae) and malformations due to radiation contamination in the area of the Mayak (Chelyabinsk Province, Russia) nuclear plant

This study was designed to describe normal axial skeletal structure in common roach Rutilus rutilus from putative unaffected environmental conditions, and the occurrence of skeletal malformations in the fish from an area under radiation contamination. Specimens were collected from water bodies of the Techa Cascade Reservoirs located near the Mayak atomic industry plant in the River Ob' drainage, Chelyabinsk Province, Russia. One sample was collected from Lake Irtyash, a reservoir of drinkable water, supplying the town of Ozersk, and the other one from a technical reservoir which is a storage of liquid radioactive waste from Mayak and characterized by high radioactive contamination (mostly (90)Sr and (137)Cs). A comparison was made with historical material collected from the River Ob' before the middle of the 20th century, i.e. before the environment became affected by radioactive contamination. A high number of abnormalities of the axial skeleton were detected in both Mayak samples, in 94 and 97% of examined specimens, in contrast to about 20% in the historical specimens. The abnormalities were in both the unpaired fins and the vertebral column, including the caudal complex and included supernumerary elements, fusions, deformities and displacement of the elements. Most axial skeleton abnormalities, however, were minor, such as splitting, shortening or deformation of spines. Severe defects, such as extensive scolioses, lordoses and kyphoses, were not found. The causes of the abnormalities were not identified in this study, but the high incidence of malformations may be attributed to genetically determined imbalance during development. The almost equal distribution of abnormalities among the fish from non-contaminated and radioactive contaminated reservoirs may be explained by either recent gene flow within the population of R. rutilus in the River Techa system or the effect of unknown unfavourable environmental factors such as chemical pollution.     

Current radioecological conditions of Malyĭ Igish lake located on the axial part of the East-Urals radioactive trace

The paper presents data on the current radioecological situation at Lake Maly Igish located on the axial part of the East-Urals radioactive trace formed after the 1957 accident at the Mayak PA. The chemical composition of the water and bottom deposits, as well as the distribution of 90Sr, 137Cs, and of the microelements in the main components of the water reservoir were studied. The current species composition of higher aquatic plants and of the species-specific concentration of 90Sr and of 137Cs was identified.     

Current radiation status of the ecosystem of the Lake Bolshoi Igish situated along the axial part of the East-Urals radioactive trace

Data on the current radioecological status of lake Bolshoi Igish in the Middle Ural are presented in the paper. The lake is situated on the central axis of the East-Urals radioactive trace which was formed as a result of the 1957 nuclear accident at the Mayak Production Association. The distribution of 90Sr and 137Cs in the major components of the water basin is shown. Seasonal dynamics of the specific activity of radionuclides in water and in bottom deposits has been investigated. The current community of the higher water plant species has been studied. The paper discusses the concentration of 90Sr and 137Cs in the macrophyts of lake Bolshoi Igish depending on their species.     

Radioactive contamination of bottom sediments in the upper reaches of the Techa river: analysis of the data obtained in 1950 and 1951

A stationary sorption model has been developed for re-evaluating and analysing archive data from 1950-1951 on the radioactive contamination of Techa river bottom sediments close to the site of liquid radioactive waste discharge. In general, good agreement was obtained between calculations and measurements, which substantiates further the assumptions and conclusions in two preceding articles, on the radionuclide composition of discharged liquid radioactive waste. Estimates on the effective liquid radioactive waste discharges given here are significantly different from those deduced in the 1950s, i.e. in summer 1950 and October 1951. The results are discussed in relation to the Techa River Dosimetry System 2000 (TRDS-2000) that has recently been presented to serve as a means for estimating doses to the Techa river residents. Parameter values describing the exponential decrease of bottom sediment contamination along the river due to short-lived radionuclides, such as (106)Ru, and (144)Ce, agree reasonably with those used in TRDS-2000. However, for other radionuclides, such as (95)Zr, (95)Nb, (91)Y, (90)Sr and (137)Cs, substantial differences are found. It is demonstrated that water flow rate, width of the river, and surface area of bottom sediments are important parameters which were not adequately taken into account in TRDS-2000. Also, the stirring-up of contaminated bottom sediments and their subsequent transport by the water flow are seen to be an important mechanism that governs the radionuclide transport downstream. This mechanism was not included in the TRDS-2000 model. It is concluded that the sorption model used in TRDS-2000 for the reconstruction of radioactive contamination of water and bottom sediments of the Techa river in 1949-1951, is subject to considerable errors. While the present paper is focussed on details of the dosimetric modelling, the implications for the Techa river dosimetry are major. They will be further elucidated in a forthcoming paper.     

Estimation of rate constant for dissolution of radioactive fuel particles

Some theoretical of the experimental investigation of solubility of radioactive aerosols were examined. Filters, which were exposed during October-November 1987 in Pripyat town, were studied. Measurements on 22 November 1987 showed that an activity in the air was 12.1-20.8 mBq/m3 for 137Cs, 34.9-89.3 mBq/m-3 for 144Ce, 24.3-30.5 mBq/m-3 for 106Ru. Disperse structure of aerosol hot particles and the number of hot particles on each filter fragment was estimated by radiography. To determine a dissolution rate constant a static system with two 0.14 micron pore size membrane MFE filters (Dubna, Russia) enclosing fragments of Petryanov filters was selected. The composition was held in Gamble's solution lung fluid anf then in 0.1 mol/l HCl as dastic juice simulation. The activity of 90Sr, 238Pu, 239 + 240Pu, 241Am and 244Cm in aerosol filters and solutions was measured by radiochemical methods. It was shown that leaching of radionuclides from aerosol hot particles in lung fluid simulation decreases in line 137Cs > 90Sr > 239 + 240Pu > or = 241Am, depending om particle diameter and time. Dissolution constants were presented. Dissolution of aerosol particles in 0.1 mol/l HCl is also shown (dissolution time was 3 days). A radionuclide transition to HCl solution decreases in line 90Am 241Am > 137Cs > 239 + 240Pu. A transition degree reached 21% for 90Sr and extraction of 241Am was 3-17%.     

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.     

Pilot study of the Urals population by tooth electron paramagnetic resonance dosimetry

During 1949–1956, about 76 × 10⁶ m³ of radioactive liquid waste containing a total activity of 10¹⁷ Bq was discharged into the Techa River by the first Russian industrial nuclear facility Mayak. As a consequence, the population living in the river valley received considerable internal and external radiation doses. The results of a first application of electron paramagnetic resonance (EPR) of tooth enamel for a retrospective individual dose evaluation of the residents of the Techa riverside are presented. Three main contributions to the dose absorbed in tooth enamel have been considered: external exposure mainly from the Techa River sediments, internal exposure mainly due to ⁹⁰Sr; and background radiation including all other sources of exposure except the Techa River. The teeth of 86 inhabitants of the town Kamensk-Uralskii were analysed to determine the age-dependent contribution of the background radiation to the enamel dose. For 22 residents of the middle and lower Techa riverside, measurements of the ⁹⁰Sr whole-body content and EPR measurements of the absorbed dose in enamel were used to establish a correlation between these two quantities. Finally, absorbed doses in the enamel of five residents of the upper Techa riverside were determined by the EPR method. Contributions of the background radiation and the internal ⁹⁰Sr contamination were subtracted to determine the external exposure of the residents.     

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.     

Dose assessment for the Metlino and Muslyumovo populations who lived along the Techa river from 1949 to 1954

In the period from 1949 to 1956, liquid radioactive waste was routinely and accidentally discharged by the Mayak Production Association, Southern Urals, Russia, into the Techa river. Based on a novel approach, the contamination of the Techa river water, the bottom sediments and the adjacent flood plains was modelled, and internal and external doses were estimated for two villages located downstream of the site of liquid radioactive waste release. Altogether, 11 radionuclides that occurred in the liquid radioactive waste were included in the calculations. The results suggest significantly higher doses than previously assumed, with the major contribution in the year 1951. Radionuclides with half-lives of less than 1 year, such as ⁸⁹Sr, ¹³¹I, ⁹⁵Zr+⁹⁵Nb, ¹⁰³Ru+^103mRh, ¹⁴⁰Ba+¹⁴⁰La, and ¹⁴⁴Ce+¹⁴⁴Pr, represent the major sources and, in contrast, long-lived radionuclides, such as ⁹⁰Sr and ¹³⁷Cs that have so far been assumed to be most important, did not dominate the doses. For adults from the village Metlino, located 7 km downstream of the site of liquid radioactive waste discharge, the committed effective doses due to intake of radionuclides were calculated to be about 2.3 Sv, while the external doses were between about 1.2 Sv and 6.9 Sv. On the other hand, for adults from Muslyumovo, located 75 km downstream, the commited effective doses due to intake of radionuclides were calculated to be about 0.5 Sv, while the external doses were between 0.5 Sv and 2.0 Sv. The values for the skin doses to the Metlino and Muslyumovo populations were about 7.1 Sv and 1.3 Sv, respectively. It is concluded that the current dose estimates for the residents of the Techa river need, therefore, reevaluation.     

Modelling of long-term radionuclide migration in a non-running fresh-water reservoir

A mathematical model is presented for radionuclide migration in a non-running fresh-water reservoir that takes into account removal of microimpurities from water as a result of both molecular and ion exchange sorption at the bottom sediments water interface and detritus formation. The model was tested for sensitivity to precisely estimate experimental parameters. The test showed that the model is universal. Prediction was made of reduction in water of 137Cs and 90Sr contents and distribution of these radionuclides in the water body affected by the accident at the "Mayak" chemical plant.     

The features of radioactive contamination of small birds in Chernobyl zone in 2003-2005

Radioactive contamination of small birds (484 individuals, 44 species) was investigated in the Chernobyl zone (Ukraine) in 2003-2005. Values variation of 90Sr and of 137Cs activity concentration reached 3-4 orders of magnitude even in one site, and maximum values amounted to hundreds Bq/g at the central plots of the zone. The biggest contamination is appropriate to birds in breeding season and to settled species, whilst migrants are the "cleanest". Change of contamination within a year reflects seasonal and short-term changes in birds diet and in behaviour. During breeding season females have higher activity concentration of 90Sr, while on 137Cs accumulation sexual differences are absent. In other seasons radioactive contamination of male and female does not differ if they live in similar conditions and have similar migratory behavior. Young birds during fledging and just after, as a rule, have higher levels of 90Sr contamination than adults, and actually do not differ on 137Cs accumulation. On a set of own and published data, it was assumed, that in small birds the half-life period of 137Cs extraction amounts to 1-2 days, and 90Sr- 5-10 days, and dynamic equilibrium of the radionuclides turnover in organism is reached over 4-7 and 17-34 days, respectively, after the birds arrival on the contaminated site. Among 44 studied species, those who search invertebrates in soil top layer or forest litter (thrushes). have noticeably higher accumulation of 90Sr and of 137Cs. Specific differences of radionuclides accumulation for the rest birds were not revealed due to small sample sizes of the species.     

Plutonium,241Am,90sr,and137cs concentrations in some antarctic matrices

A radioecological survey in Antarctica shows that the^239+240Pu,²³⁸Pu,²⁴¹Am,⁹⁰Sr, and¹³⁷Cs activities were detectable in nearly all the samples. The activity level of^239+240Pu,²⁴¹Am, and¹³⁷Cs in antarctic sediments was about 5–20 times lower than in the northern Adriatic Sea sediments, but the²³⁸Pu activities were relatively high. It was interesting to note that the⁹⁰Sr concentrations in all the sediments tended to be low, which could be the result of the easier exchangeable behavior of⁹⁰Sr in water. High concentrations were detected in mosses and lichens and their activity levels were comparable to those in central Italy. The radionuclide ratio analyses show that the major part of^239+240Pu,²⁴¹Am,⁹⁰Sr, and¹³⁷Cs was a result of nuclear weapon tests. The higher²⁴¹Am/^239+240Pu ratio was observed and it could perhaps be the result of fallout of nuclear weapon tests prior to 1962. The²³⁸Pu/^239+240Pu ratio in the antarctic matrices was about seven times higher than in the Northern hemisphere and it could be inferred that the major part of²³⁸Pu was originating from the SNAP-9A satellite accident.     

90Sr, 137Cs, 238Pu, 239+240Pu,and 241Am radionuclides in macrophytes within the Krasnensky flood plain: species specificity of concentration and distribution in phytocenosis components

The analysis of the content of radionuclides 90Sr, 137Cs, 238Pu, 239 + 240Pu and 241Am in water vegetation of flood plain reservoirs has allowed studing features of radionuclide accumulation by various species of macrophytes and revealing bioindicators of radionuclide contamination. Thus species-specificity of radionuclide accumulation can essentially change the contribution of different species to a percentage ratio of the radionuclide content in phytomass of reservoirs in comparison with fund of higher aquatic plants.