Effect of Site-Specific Parameters on the Transfer of 137Cs and 90Sr into Freshwater Fishes1,2

The content of ¹³⁷Cs in fallout, fish, and water was measured with the aim to study the role of site-specific parameters on the transfer of ¹³⁷Cs into fishes. The temporal changes of 137Cs and 90Sr in various types of fishes were studied at two sites of Lake Saimaa. The ¹³⁷Cs content in fishes in the Ukonvesi area, which is the north-western part of the lake, was clearly lower than that in the southern parts of the lake, in Ala-Saimaa, although the fallout of ¹³⁷Cs to the Ukonvesi area was somewhat higher than that to Ala-Saimaa. The fallout in 1986 was about 6 kBq m^{- 2} to the Ukonvesi area and about 3 kBq m^{- 2} to the southern parts of the lake. The ¹³⁷Cs content in fishes was the highest in 1988-1989 in Ala-Saimaa, approximately 700 Bq kg^{- 1}, while that in the Ukonvesi area was only about 300 Bq kg^{- 1}, where the values were the highest in 1987. In Ukonvesi the ¹³⁷Cs content in fishes decreased rapidly, being already in 1990 almost at the same level as in 2000. In the southern parts of the lake the decrease in the ¹³⁷Cs content in fishes was much slower. Also the ⁹⁰Sr content in fishes in Ukonvesi was lower than that in Ala-Saimaa. The ¹³⁷Cs content of the water in the Ukonvesi area decreased rapidly, being about 7 Bq m^{- 3} in 1998, while that in the lower areas of the lake was still 15 Bq m^{- 3} in 2000. The ⁹⁰Sr content in water was approximately the same at the both sampling sites (7-8 Bq m^{- 3}). The water chemical parameters, such as potassium, total phosphorus, total nitrogen, chlorophyll a, and electrical conductivity were significantly higher in Ukonvesi than in Ala-Saimaa.     

Cesium-137 of Chernobyl origin in lake–river systems of Eastern Fennoscandia: 30 years after the accident

Contamination of waters of lake–river systems after many-year migration of ¹³⁷Cs in water bodies was studied. In lakes with the ¹³⁷Cs fallout density lower than 8 kBq m^–2, the radionuclide concentrations in water after 24–29 years did not exceed 2–3 Bq m^–3, and at a fallout level of 37 kBq m^–2 it was in the range 11–34 Bq m^–3. The natural half-clearance time Т of lake waters from ¹³⁷Cs was 6–7 years at the exposure of up to 20 years. The ¹³⁷Cs migration in the lake–river systems that occurred during ~30 years did not lead to structural changes in the water contamination: The initially low ¹³⁷Cs level in lake waters did not become high, and vice versa. Among rivers feeding Lake Ladoga, the ¹³⁷Cs level in the Vuoksa River is ~3 times higher than in waters of the Volkhov and Svir rivers. During the period 1988–2015, 21.3 TBq of ¹³⁷Cs was supplied to Lake Ladoga with Vuoksa waters. The Vuoksa source from the Saima lake system with increased contamination with ¹³⁷Cs of Chernobyl origin leads to long-term supply of this radionuclide to Lake Ladoga.     

Distinctive Features of the Formation and Migration of Radioactive Contamination in the Iput River after the Accident at the Chernobyl Nuclear Power Plant

With the example of the Iput river, studies are performed and based on them an analysis is made of the formation of contamination of elements of a river system by radionuclides ¹³⁷Cs and ⁹⁰Sr after the accident at the Chernobyl Nuclear Power Plant. It has been revealed that before the years 1990–1994 the contamination of the river system was mainly formed by the primary fallout of radionuclides on the water surface of the river but after the year 2000 it will be determined only by the ingress of radioactive contaminants with surface flow from a water catchment. The studies have shown that the contamination of the Iput river in the territory of Belarus is substantially influenced by the transfrontier transfer of radionuclides from the territory of Russia. According to our estimates, at the end of 1986, this contribution amounted to 30% for ¹³⁷Cs and 96% for ⁹⁰Sr; as of now, it is 86% and 65% for ¹³⁷Cs and ⁹⁰Sr, respectively.     

Artificial radioactivity of the White Sea

Vertical profiles of ¹³⁷Cs in bottom sediments collected from various sites of the White Sea are reported. From these profiles, the ¹³⁷Cs inventory in the bulk of sediment was estimated to be 270–3300 Bq m^?2, and the surface contamination of sediment, 7.1–46.5 Bq kg^?1. In the most of the sediment cores, ¹³⁷Cs was detected to a depth of >20 cm. The highest activity of ¹³⁷Cs was usually observed in the 1–2-cm layer. The mean specific radioactivity of ¹³⁷Cs in the seawater was 4.1 Bq m^?3.     

Plutonium Contamination Level and Isotopic Composition in Soils around St. Petersburg

Plutonium isotopic composition including ²³⁸Pu, ²³⁹Pu, ²⁴⁰Pu, and ²⁴¹Pu and the Pu contamination level are determined in soils around St. Petersburg using an advanced procedure involving radiochemical separation stage followed by the -ray spectrometric and mass spectrometric determination. The Pu specific activity in surface horizons (0-25 cm) ranges from 0.2 to 0.44 Bq kg^-1. The mean ²³⁸Pu/239,240Pu activity ratio is found to be 0.033±0.007. The Pu contamination level of the surface horizon (0-25 cm) is 62±5 Bq m^-2. The ²³⁸Pu/²³⁹Pu, ²⁴⁰Pu/²³⁹Pu, and ²⁴¹Pu/²³⁹Pu isotopic ratios are (2.0±0.5)×10^-4, 0.172±0.004, and 0.003±0.002, respectively. These ratios are close to the values typical of plutonium from the global radioactive fallout due to nuclear weapons tests in the atmosphere. The effect of the Chernobyl accident and regional potential contamination sources, including the Leningrad NPP, on the Pu isotopic composition and contamination level in the soil is insignificant.     

Association of 90xSr, 137Cs, 239,240Pu, 241Am,and 244Cm with Soil Absorbing Complex in Soils Typical of the Vicinity of the Chernobyl NPP

Association of the main long-lived radionuclides ¹³⁷Cs, ⁹⁰Sr, ^239,240Pu, ²⁴¹Am, and ²⁴⁴Cm with various components of the soil absorbing complexes from soil samples collected along the western, northwestern, and northern tracks of radioactive fallout in the vicinity of the Chernobyl NPP was studied by the sequential leaching. In the samples of the sandy soil collected in the floodplain of the Pripyat river along the northwestern radioactive track, more than 85% of ⁹⁰Sr, 55% of ^239,240Pu, and 75% of ²⁴¹Am and ²⁴⁴Cm are associated with various components of the soil absorbing complex and are potentially mobile species. In the soil samples collected along the narrow western track, 80-85% of ¹³⁷Cs, ⁹⁰Sr, ^239,240Pu, ²⁴¹Am, and ²⁴⁴Cm are incorporated in hot particles. The degree of ¹³⁷Cs, ⁹⁰Sr, ^239,240Pu, ²⁴¹Am, and ²⁴⁴Cm association with different components of the soil absorbing complex is a function of the radionuclide type and physicochemical features of soil.     

Current radiation situation in near area of air nuclear explosion conducted at Totskoe Testing Ground (Orenburg oblast) on September 14, 1954

Results obtained in 1996–2000 at the Radium Institute on the radiation situation in the epicenter and near trace areas of nuclear explosion conducted at the Totskoe Testing Ground (Orenburg oblast) in 1954 are reviewed, including analysis of available data on the Totskoe 1954 war games and also on global fallout levels typical of the Orenburg oblast. The specific activities of long-lived radionuclides (⁹⁰Sr, ¹³⁷Cs, and ^{239 + 240}Pu) in the soil are determined. At the epicenter, the specific activities of induced radionuclides (⁶⁰Co and ¹⁵²Eu) are determined. The surface and vertical distributions of radionuclides are studied. The contamination levels of the epicenter and near trace areas with explosion-derived radionuclides are estimated taking into account the global fallout levels characteristic of the Orenburg region. For the first time, a comprehensive regular-grid examination of radiation situation in the indicated territory is made. The isotopic composition of Pu in the soil corresponds to that of the global fallout, but not to weapons-grade Pu, suggesting the lack of contamination with long-lived fission products derived from Totskoe 1954 explosion, or indicating that the contamination levels with these products are within the fluctuations typical of the global fallout.Translated from Radiokhimiya, Vol. 46, No. 6, 2004, pp. 564–568.Original Russian Text Copyright © 2004 by Dubasov, Trifonov, Arshanskii, Skovorodkin, Smirnova.     

The long-term decrease of 90Sr availability in the environment and its transfer to man after a nuclear fallout

Due to its long physical half-life, and the fact that its long-term mobility in the environment as well as its radiotoxicity is higher than that of 137Cs, the long-term bio-availability of 90Sr in the environment is of importance with regard to the long-term population exposure after fallout from nuclear weapons detonations or a severe reactor accident. It will also substantially influence the time-span required until re-utilisation of highly contaminated territory is possible again. An assessment of the long-term decrease of the activity concentration in all foodstuffs relevant for internal exposure after severe 90Sr fallout was performed. The observed effective half-lives were approximately 1.8-2.1 years in the first 2-3 years after the end of fallout and 8-10 years in the following three decades. This is equivalent to a biological half-life of about 13.2 years and results in a total 50 year dose of 6.2 times the first year exposure. Due to this decline in 90Sr-availability, the average annual activity intake of 90Sr in Austria has decreased from 840 Bq at the climax of the nuclear weapons tests to about 42 Bq in 1997 for adults, and from 500 Bq to about 35 Bq for 1 year old infants. This is equivalent to a 90Sr ingestion dose of 1.2 microSv for adults and 2.5 microSv for 1 year old infants in 1997 or less than 0.4% of the ingestion dose by natural radionuclides in the diet.     

Levels of 90Sr and 137Cs in the urine of Finnish people

The aim of this study was to estimate the current concentrations of 90Sr and 137Cs in the urine of Finnish people and to estimate the doses. Two to three daily urine samples were collected from 18 adult Finnish volunteers in connection with studies of 137Cs body burdens in 1999-2001. The 90Sr activities in urine varied between 1.4 and 11 mBq l(-1). The 137Cs activity in urine varied between 0.36 and 56 Bq l(-1). The daily urinary excretion was found to be 4.8-17 mBq for 90Sr and 0.81-68 Bq for 137Cs. Assuming that the daily 90Sr intake was constant and that 18% of the ingested activity was excreted in urine, the mean intake in the investigated group would vary between 27 and 96 mBq d(-1). Based on these estimated intake values, the respective annual effective internal doses from 90Sr and 90Y varied from 0.3 to 1.0 microSv and from 137Cs from 4 to 350 microSv during the sampling period.     

Effect of basic chemical characteristics of soils on mobility of radionuclides in them

Interplay between the basic chemical characteristics of soils of the Belarussian Polessie and the tightness of fixation of Chernobyl-derived ¹³⁷Cs and ⁹⁰Sr in them is studied. The mobility of radionuclides in the soil proved to be controlled essentially by the soil type and organic matter content. In the investigated soils, nonexchange sorption of ¹³⁷Cs and exchange sorption of ⁹⁰Sr dominate.     

Soil Contamination with Fuel Component of Chernobyl Radioactive Fallout

Radionuclide activity ratios in the fuel component of the Chernobyl fallout are reestimated on the basis of new experimental data, and maps of the density of contamination of the Chernobyl 30-km zone with ¹⁵⁴Eu, ²³⁸Pu, ^239+240Pu, and ²⁴¹Am as of January 1, 2000 are compiled. The total radionuclide inventories in the top 30-cm horizon of the soil of the 30-km zone (minus the NPP service area, cooling pond, and radioactive waste disposal sites) on January 1, 2000 were estimated to be (Bq): ⁹⁰Sr 7.7×10^{1 4}, ¹³⁷Cs 2.8×10^{1 5}, ¹⁵⁴Eu 1.4 × 10^{1 3}, ²³⁸Pu 7.2 × 10^{1 2}, ^239+240Pu 1.5 × 10^{1 3}, and ²⁴¹Am 1.8 × 10^{1 3}, which makes up to 0.4-0.5% of the total amount of these radionuclides produced in the 4th block of CNPP. This value is lower by a factor of 3 than that generally accepted so far. The radionuclide inventories in other objects of the 30-km zone and beyond it are also estimated. The total amounts of radionuclides fallen out with fuel particles beyond the NPP service area are reestimated. The resulting value (1.5±0.5% of the total produced in the reactor by the accident time) is lower by half as compared to the previous estimates. Two thirds of these amounts are found on the Ukrainian territory.     

Distribution of <Superscript>137</Superscript>Cs, <Superscript>90</Superscript>Sr, <Superscript>239 + 240</Superscript>Pu, <Superscript>241</Superscript>Am,and <Superscript>244</Superscript>Cm among Components of Organic Matter of Soils in Near Exclusion Zone of the Chernobyl NPP

Distribution of Chernobyl-derived ¹³⁷Cs, ⁹⁰Sr, ^{239 + 240}Pu, ²⁴¹Am, and ²⁴⁴Cm among organic fractions of soddy-podzolic, sandy, soddy-meadow, and peat soils collected from the Chernobyl Exclusion Zone along the North-Western radioactive fallout track was determined. Regardless of the soil type, 80–85% of ¹³⁷Cs is tightly fixed on the mineral fraction of the soil. Depending on the soil type, 50–70% of ⁹⁰Sr and 15– 45% of ²⁴¹Am are associated with fulvic acid fractions. ²⁴¹Am and ²⁴⁴Cu are similarly distributed among the organic acid fractions. In all the soil types studied, ^{239 + 240}Pu is associated essentially with humic acid fractions. Natural ^{230, 232}Th and technogenic ^{239 + 240}Pu are similarly distributed among the organic fractions.__________Translated from Radiokhimiya, Vol. 47, No. 1, 2005, pp. 91–96.Original Russian Text Copyright © 2005 by Odintsov, Pazukhin, Sazhenyuk.     

Role of Suspended Matter and Dissolved Organic Substances in Behavior and Migration of Anthropogenic Radionuclides in River-Sea Aquatic Systems

Distribution of Cs, Sr, and Pu nuclides between suspended matter and the aqueous phase and the features of interaction of these radionuclides with dissolved organic matter are studied, to gain a better insight into the radionuclide behavior in the Ob and Yenisei estuaries and adjacent Kara Sea. For radionuclide speciation, the experimental study included determination of the radionuclide activities in aqueous solutions after filtration and ultrafiltration of large-volume water samples and membrane fractionation of small-volume water samples by passing the solution through a cartridge with filters of regularly decreasing pore size followed by mass-spectrometric determination of elements. In the water-soluble fraction, the ¹³⁷Cs activity increases with increasing salinity, whereas that of ⁹⁰Sr decreases, which can be attributed to the differences in the physicochemical behavior of the radionuclides in solutions and also to the effect of contamination sources. In seawater, suspended material can retain 1-10% of ¹³⁷Cs and ⁹⁰Sr. In the estuarine zones, these values can be 20-40%. More than 50% of ⁹⁰Sr and ^239,240Pu are associated with dissolved organic matter. In saline water this effect is less pronounced.     

In situ long-term monitoring system for radioactive contaminants

A long-term in situ subsurface instrument for monitoring radioactive contaminant plumes, as an alternative to soil analysis, is described. A portable, laser-based reader optically stimulates luminescence from sensors, each containing an Al2O3:C dosemeter. The sensors, designed for placement at various subsurface locations around a waste site, are allowed to accumulate dose for a predetermined time that is based on the instrument's minimum detectable dose (MDD). The reader is then attached to the sensor by fibre optic cable to read the accumulated dose; an increase above natural background levels indicating the presence of leaked radioactivity. Based on an MDD of 5 microGy, it is shown that the sensor can measure soil concentrations of 1.85 Bq cm(-3) after an exposure time of 50 h for 137Cs and 67 h for 90Sr/90Y. Discrimination between beta and gamma radiation is possible using an end cap placed over one of the two paired sensors, allowing simultaneous measurement of 137Cs and 90Sr/90Y in a mixed field. The monitor system represents a substantial improvement over quarterly soil sampling because of a greatly increased measurement frequency and the ability to perform measurements reproducibly.     

Sorption of 137Cs and 90Sr Ionic Species on Soil of Various Types

Sorption of ¹³⁷Cs and ⁹⁰Sr ionic species on soils with different agrochemical features was studied. The dependence of ¹³⁷Cs sorption on peaty-bog soil on the ratio of the solid and liquid phases shows that sorption occurs by the ion-exchange mechanism. The correlation between the potassium content in soils and     

Coprecipitation of Trace Amounts of <Superscript>137</Superscript>Cs and <Superscript>85</Superscript>Sr with [Na(18-Crown-6]BPh<Subscript>4</Subscript> from Neutral and Alkaline Solutions

Coprecipitation of ¹³⁷Cs and ⁸⁵Sr with [Na(18-crown-6]BPh₄ solid phase from aqueous, aqueous-ethanolic, and alkaline solutions is studied. ¹³⁷Cs and ⁸⁵Sr cocrystallize with [Na(18-crown-6]BPh₄ from aqueous and aqueous-ethanolic solutions. The cocrystallization coefficients D of ¹³⁷Cs and ⁸⁵Sr from aqueous solutions are 2.6±0.5 and 3.3±0.3, respectively. For aqueous-ethanolic solutions, the corresponding values are 4.4±0.5 and 3.4±0.4. In the alkaline solutions (0.1 and 1 M NaOH), 54–74% of ¹³⁷Cs and 37–51% of ⁸⁵Sr pass into the [Na(18-crown-6]BPh₄ solid phase, depending on the crown ether concentration in the system.__________Translated from Radiokhimiya, Vol. 47, No. 3, 2005, pp. 257–260.Original Russian Text Copyright © 2005 by Kulyukhin, Konovalova, Rumer, Kamenskaya, Mikheev.     

Artificial radioactivity in human body and the environment

The ¹³⁷Cs and ⁹⁰Sr fallout in Finland and the content of these nuclides in milk samples, water reservoirs, fishes, and human bodies were measured. Published in Russian in Radiokhimiya, 2006, Vol. 48, No. 6, pp. 562–566. The text was submitted by the authors in English. Reported at the 7th Russian-Finnish Symposium on Radiochemistry (St. Petersburg, November 2005).     

Sorption of 90Sr and 137Cs on Natural Sorbents in Model Environmental Systems

Sorption of ⁹⁰Sr and ¹³⁷Cs from both tap drinking water and water of Beloyarsk storage basin on samples of natural ion exchangers, glauconite concentrate and white alluvial clay, was studied under static conditions. The distribution coefficients of ⁹⁰Sr and ¹³⁷Cs between these sorbents and water were studied as influenced by the equilibration time and water type. With white alluvial clay and glauconite concentrate the sorption equilibrium is reached within 90 and 270 days, respectively. Sorption characteristics of these natural sorbents allow them to be recommended for water decontamination from ⁹⁰Sr and ¹³⁷Cs.     

Sorption of 137Cs and 90Sr by potassium production wastes, clay-salt slimes

Sorption of ¹³⁷Cs and ⁹⁰Sr by clay-salt slimes from model aqueous salt solutions (4.0–40.0 g l^?1 NaCl + KCl) was studied under static conditions. The influence of the sorption parameters (time, specific consumption, salt content) on the efficiency of the ¹³⁷Cs and ⁹⁰Sr recovery with finely dispersed sorbents was studied. The activity of the aqueous salt solution decreases by two orders of magnitude owing to the recovery of ¹³⁷Cs.     

Radioactive Contamination of the Neva River-Lake Ladoga Aquatic System

Many-year monitoring data on the ⁹⁰Sr and ¹³⁷Cs levels in water of the Neva River and Lake Ladoga are presented. In 1970-1990, the ⁹⁰Sr level in the Neva River steadily increased. In 1991, a radiological survey was made of the Kit experimental vessel with radioactive wastes in its holds, which was on berthing in the northwesteren part of Lake Ladoga. ⁹⁰Sr, ¹³⁷Cs, and ^239,240Pu were monitored in water and bottom sediments near the Kit vessel berthing after it was towed outside Lake Ladoga. In 2001, the ⁹⁰Sr concentration in water of Lake Ladoga and the Neva River considerably decreased.