137Cs and 90Sr behavioural regularities in the southeastern part of the Baltic Sea

Variations in 137Cs concentrations were investigated over the period 1986-1997 in the southeastern part of the Baltic Sea, following the Chernobyl power plant accident. The rate of "self-cleaning" was demonstrated to be very slow, the average concentration of 137Cs in 1996 being almost the same as that measured directly after the accident, in 1986. Measurements of both 137Cs and 90Sr concentrations generally revealed homogeneous distributions in this region of the Baltic Sea, though patchy distributions did develop under some hydrometeorological conditions. Specifically, the 137Cs concentration distribution became heterogeneous with values varying in the range 60-92 Bq/m3 under south-southwesterly wind conditions whilst the 90Sr concentration distribution developed similar characteristics with values ranging from 15 to 64 Bq/m3 under east-southeasterly wind conditions. In addition, in coastal waters, over extensive periods of north-northwesterly winds in 1995, 137Cs concentrations increased to values 1.5-2 times the overall average concentration, which was registered in 1986 and 1996. These data therefore reveal a continuing significant pollution of the waters of the Baltic Sea resulting from the Chernobyl power plant accident, a pollution compounded by the slow rate of radionuclide self-cleaning and significant probability of sudden regional concentration increase.     

Contamination of the southern Baltic Sea with 137Cs and 90Sr over the period 2000-2004

Changes of the (137)Cs activity concentrations in the southern Baltic Sea waters were investigated over the period 2000-2004 and distribution of the (90)Sr concentrations was determined in 2004. In the discriminated period further decrease of (137)Cs concentrations was observed. The average activity concentration of (137)Cs declined from 59.4Bq/m(3) in 2000 to 45.1Bq/m(3) in 2004. The greatest changes of (137)Cs activities occurred in 2003 as a consequence of the medium-size inflow of a saline waters from the North Sea. This inflow affected (137)Cs activities as well as its distribution in the Baltic Sea. Changes in (90)Sr activity concentrations proceeded at much slower rate. The average activity concentration of (90)Sr was equal to 8.7Bq/m(3) in 2004. The annual fluvial (137)Cs fluxes from the Vistula river were also estimated. In 2000, the (137)Cs load from Vistula was of an order of 0.15TBq/year, and in 2004 0.05TBq/year.     

Anthropogenic radionuclides in the Japan Sea: their distributions and transport processes

The anthropogenic radionuclides, (90)Sr, (137)Cs and (239+240)Pu, were measured in the water column of the Japan Sea/East Sea during 1997-2000. The vertical profiles of radionuclide concentrations showed: exponential decrease with depth for (90)Sr and (137)Cs, and surface minimum/subsurface maximum for (239+240)Pu. These results do not differ substantially from results reported previously. The area-averaged concentrations of radionuclides in the Japan Sea are higher than those found in the Northwest Pacific Ocean below surface layer showing the accumulation of the radionuclides in the deep waters in the Japan Sea. Concerning spatial distributions, the area of high (137)Cs inventory extends from the Japan Basin into the Yamato Basin. It is suggested that wintertime convection of water, occurring mainly in the Japan Basin, causes the radionuclides to sink. The nuclides then advect into the Yamato Basin after detouring around the Yamato Rise.     

Distribution of 90Sr and 137Cs in Arctic soil profiles polluted by heavy metals

Effects of industrial pollution on the behaviour of radionuclides in spruce forest ecosystems were studied along a gradient from of a copper-nickel smelter in Monchegorsk, NW Russia. A reference site was situated in Lapland, Finland, 152 km west of Monchegorsk. Most of the total 137Cs activity in soil was in mineral (E and B) horizons, except at the reference site where the major part was still in the organic surface layer. Most of the total 90Sr activity still remaining in the soil profile was found in the surface layer, but the relative amount decreased with increasing level of industrial pollution. Pollutants from the smelter clearly affected the chemical speciation of radionuclides. Smaller amounts of exchangeable radionuclides were present in the organic surface layer at the most polluted sites. The decline of 137Cs with decreasing distance from the smelter correlated strongly with a similar depletion in exchangeable K and Mg. Total concentrations of 137Cs and 90Sr showed high correlations with exchangeable cations, particularly in the E and upper B horizon. A sudden change in behaviour of 137Cs in the lower B horizon may be associated with changes in clay mineralogy along the soil profile caused by weathering.     

90Sr, 137Cs and (239,240)Pu concentration surface water time series in the Pacific and Indian Oceans--WOMARS results

Under an IAEA's Co-ordinated Research Project "Worldwide Marine Radioactivity Studies (WOMARS)" 90Sr, 137Cs and (239,240)Pu concentration surface water time series in the Pacific and Indian Oceans have been investigated. The Pacific and Indian Oceans were divided into 17 latitudinal boxes according to ocean circulation, global fallout patterns and the location of nuclear weapons test sites. The present levels and time trends in radionuclide concentrations in surface water for each box were studied and the corresponding effective half-lives were estimated. For the year 2000, the estimated average 90Sr, 137Cs and (239,240)Pu concentrations in surface waters of the Pacific and Indian Oceans varied from 0.1 to 1.5 mBq/L, 0.1 to 2.8 mBq/L, and 0.1 to 5.2 microBq/L, respectively. The mean effective half-lives for 90Sr and 137Cs in surface water were 12+/-1 years for the North, 20+/-1 years for the South and 21+/-2 years for the Equatorial Pacific. For (239,240)Pu the corresponding mean effective half-lives were 7+/-1 years for the North, 12+/-4 years for the South and 10+/-2 years for the Equatorial Pacific. For the Indian Ocean the mean effective half-lives of 137Cs and (239,240)Pu were 21+/-2 years and 9+/-1 years, respectively. There is evidence that fallout removal rates before 1970 were faster than those observed during recent decades. The estimated surface water concentrations of 90Sr, 137Cs and (239,240)Pu in latitudinal belts of the Pacific and Indian Oceans for the year 2000 may be used as the average levels so that any new contribution from nuclear facilities, nuclear weapons test sites, radioactive waste dumping sites and from possible nuclear accidents can be identified.     

Spatial distribution of 3H, 90Sr, 137Cs and (239,240)Pu in surface waters of the Pacific and Indian Oceans--GLOMARD database

The data stored in the IAEA's Global Marine Radioactivity Database (GLOMARD) developed in the framework of the IAEA's project "Worldwide Marine Radioactivity Studies (WOMARS)" have been evaluated for Pacific and Indian Ocean surface waters. Four anthropogenic radionuclides-- 3H, 90Sr, 137Cs and (239,240)Pu --have been chosen as the most representative of anthropogenic radioactivity in the marine environment, comprising beta, gamma and alpha-emitters which are the most frequently analysed in the marine environment and which have (with the exception of tritium) the highest potential contribution to radiation doses to humans via seafood consumption. For the purposes of this study, the Pacific and Indian Oceans were divided into latitudinal boxes for which average radionuclide concentrations were estimated for the year 2000. The highest concentrations have been observed in the Japan Sea/East Sea and the North-West Pacific Ocean, the lowest in the Southern Ocean.     

The effective and environmental half-life of 137Cs at Coral Islands at the former US nuclear test site

The United States (US) conducted nuclear weapons testing from 1946 to 1958 at Bikini and Enewetak Atolls in the northern Marshall Islands. Based on previous detailed dose assessments for Bikini, Enewetak, Rongelap, and Utirik Atolls over a period of 28 years, cesium-137 (137Cs) at Bikini Atoll contributes about 85-89% of the total estimated dose through the terrestrial food chain as a result of uptake of 137Cs by food crops. The estimated integral 30, 50, and 70-year doses were based on the radiological decay of 137Cs (30-year half-life) and other radionuclides. However, there is a continuing inventory of 137Cs and 90Sr in the fresh water portion of the groundwater at all contaminated atolls even though the turnover rate of the fresh groundwater is about 5 years. This is evidence that a portion of the soluble fraction of 137Cs and 90Sr inventory in the soil is lost by transport to groundwater when rainfall is heavy enough to cause recharge of the lens, resulting in loss of 137Cs from the soil column and root zone of the plants. This loss is in addition to that caused by radioactive decay. The effective rate of loss was determined by two methods: (1) indirectly, from time-dependent studies of the 137Cs concentration in leaves of Pisonia grandis, Guettarda specosia, Tournefortia argentea (also called Messerschmidia), Scaevola taccada, and fruit from Pandanus and coconut trees (Cocos nucifera L.), and (2) more directly, by evaluating the 137Cs/90Sr ratios at Bikini Atoll. The mean (and its lower and upper 95% confidence limits) for effective half-life and for environmental-loss half-life (ELH) based on all the trees studied on Rongelap, Bikini, and Enewetak Atolls are 8.5 years (8.0 years, 9.8 years), and 12 years (11 years, 15 years), respectively. The ELH based on the 137Cs/90Sr ratios in soil in 1987 relative to the 137Cs/90Sr ratios at the time of deposition in 1954 is less than 17 years. The magnitude of the decrease below 17 years depends on the ELH for 90Sr that is currently unknown, but some loss of 90Sr does occur along with 137Cs. If the 15-year upper 95% confidence limit on ELH (corresponding to an effective half-life of 9.8 years) is incorporated into dose calculations projected over periods of 30, 50, or 70 years, then corresponding integral doses are 58, 46 and 41%, respectively, of those previously calculated based solely on radiological decay of 137Cs.     

Distribution and sources of (129)I in rivers of the Baltic region

The concentration of (129)I was measured in 54 river waters discharging into the Baltic Sea from Sweden, Finland, Estonia, Latvia, Lithuania, Poland and Germany. Sample collection was performed during a well-bracketed time interval (June-July 1999), thus allowing comparison of the rivers over a wide latitude range without the effect of long temporal spread. Although there is no direct input of anthropogenic (129)I in the watersheds, the concentration of the isotope is about two to three orders of magnitude higher than the expected pre-nuclear era natural values in the rivers of Finland and northern Sweden, and in the rivers of southern Sweden, Lithuania, Estonia, Latvia, Poland and Germany; the (129)I concentration may reach five orders of magnitude higher. Furthermore, there are significant correlations between the (129)I concentration and latitude and/or distance from the North Sea and between (129)I and Cl. These findings suggest seawater as a main source of (129)I to the rivers through atmospheric transport. Of the many chemical parameters investigated, the pH may account for some of the variability in (129)I concentrations of the rivers. The contribution from nuclear weapon tests and the Chernobyl accident to the riverine (129)I is insignificant compared to the releases from the nuclear fuel reprocessing facilities. The total flux of (129)I by rivers to the Baltic Sea and related basins represents minor amounts of the isotope pool in these marine waters. External radioactivity hazards from (129)I are considered to be negligible in the Baltic region. However, as the main (129)I intake to the human body is likely through water, due to the large amount of daily water consumption, more concern should be given to internal radioactivity hazard that may be associated with the isotope's localized elevated concentration in the human organs.     

An analysis of the environmental mobility of radiostrontium from weapons testing and Chernobyl in Finnish river catchments

The mobility of radiostrontium within the Arctic environment and surrounding area has been studied by analysing the mobility of 90Sr in river catchments that are within Finland. The environmental mobility of 90Sr deposited by both nuclear weapons testing and the Chernobyl accident has been investigated in five Finnish river catchments. Different models assessing the time-dependent mobility of 90Sr have been evaluated. No significant differences were found between the mobility of 90Sr from nuclear weapons tests and from the Chernobyl accident. Model parameters obtained by fitting to the measurements of the deposition and runoff rates of the nuclear weapons test fallout gave predictions which were consistent with the mid- and long-term contamination by the Chernobyl fallout. A comparison of 90Sr with 137Cs showed that they had similar mobility on deposition but, as time passed, the relative mobility of 90Sr increased with respect to 137Cs over a period of 5-8 years. Once the relative migration of 90Sr with respect to 137Cs reached equilibrium, its runoff rate was, on average, approximately an order of magnitude greater than 137Cs.     

Assessment of current exposure levels in different population groups of the Kola Peninsula

Activity concentrations of 137Cs and 90Sr in samples of vegetation and natural food products collected in the Kola Peninsula in 1998 and 1999 indicate a very slow decrease in contamination levels during the last decade, mainly due to the physical decay of the radionuclides. The activity concentrations of 137Cs in reindeer meat decreased with a half-life of about 9 years. 137Cs in lichen, moss and fungi is significantly higher than in natural vegetation (grasses) and agricultural plants (potatoes). The activity concentrations of 137Cs in reindeer meat were two orders of magnitude higher than those in locally produced beef and pork. Consumption of reindeer meat, fish, mushrooms and berries constituted the main contribution to the internal dose from 137Cs and 90Sr for reindeer-breeders in the Lovozero area. The estimated committed doses due to 137Cs intake in this group were about 10 microSv per month in summer 1998 and 15 microSv per month in winter, 1999. There was good agreement between internal dose estimates based on intake assessment and whole body measurements. The population of Umba settlement, which is not involved in reindeer breeding, received individual committed doses due to 137Cs intake of about 0.5 microSv per month, about a factor of 20 less than the reindeer-breeders in Lovozero. In this case, the main contribution to the internal dose of the general population came from consumption the of 137Cs in mushrooms and forest berries. The contribution of 90Sr to the internal dose varied from 1% to 5% in the different population groups studied.     

239+240Pu, 90Sr and 137Cs inventories in surface soils of Vietnam

Fallout 239+240Pu, 238Pu, 90Sr and 137Cs inventories in surface soils were measured for 20 locations in northern Vietnam yielding the mean values (+/- standard error) of 26.5+/-3.8 Bq m(-2) for 239+240Pu, 1048+/-143 Bq m(-2) for 137Cs and 212+/-28 Bq m(-2) for 90Sr. The concentrations of 137Cs and plutonium isotopes strongly correlate with each other resulting in a stable 239+240Pu/137Cs inventory ratio of 0.025+/-0.002. Among soil parameters, organic matter and fulvic acids strongly correlate with caesium and plutonium isotopes, especially in the 0-10 cm layer. 137Cs and 239+240Pu are distributed rather similarly over the 0-10 cm and 10-20 cm layers. At locations with high contents of sand (82-93%) along the South China Sea coast, the downward percolation by rainwater results in a higher accumulation of 239+240Pu and 137Cs in the 10-20 cm layer. The mean 137Cs/ 90Sr inventory ratio is 9.3+/-2.2, and the correlation is weak between these isotopes.     

Anthropogenic radionuclides in sediment in the Japan Sea: distribution and transport processes of particulate radionuclides

Distributions of anthropogenic radionuclides ((90)Sr, (137)Cs and (239+240)Pu) in seabed sediment in the Japan Sea were collected during the period 1998-2002. Concentration of (90)Sr, (137)Cs and (239+240)Pu in seabed sediment was 0.07-1.6 Bq kg(-1), 0.4-9.1 Bq kg(-1) and 0.002-1.9 Bq kg(-1), respectively. In the northern basin of the sea (Japan Basin), (239+240)Pu/(137)Cs ratios in seabed sediment were higher and their variation was smaller compared to that in the southeastern regions of the sea. The higher (239+240)Pu/(137)Cs ratios throughout the Japan Basin were considered to reflect production of Pu-enriched particles in the surface layer and substantial sinking of particulate materials in this region. In the southern regions of the Japan Sea (<38 degrees N), both inventories and (239+240)Pu/(137)Cs ratios in sediment were larger than those in the other regions. In the southern Japan Sea, observations suggested that supply of particulate radionuclides by the Tsushima Warm Current mainly enhanced accumulation of the radionuclides in this region.     

137Cs and 90Sr transfer to milk in Austrian alpine agriculture

The alpine regions of Austria were among the most contaminated territories outside of the former USSR after the Chernobyl accident. In the investigated province of Salzburg the median (137)Cs surface deposition was 31.4 kBq m(-2) with maximum values exceeding 90 kBq m(-2) (May 1986). To quantify the transfer of (137)Cs and (90)Sr from vegetation to milk in these seminatural conditions nine seasonally grazed alps were identified and vegetation and milk sampled during summer 2002 and summer 2003. Mean+/-SD milk transfer coefficients (fm) for (137)Cs and (90)Sr were 0.0071+/-0.0009 d l(-1), and 0.0011+/-0.0004 d l(-1), respectively; which for (137)Cs is markedly higher than those fm values found in intensive agricultural systems. Transfer kinetics for (137)Cs into cow milk were approximated using a 2-compartment model with a short and a long-term component. Fitting the model to empirical data results in reliable estimates of the time constant of the short-term component, biological half-life 1.06+/-0.28 d, whereas the estimates of the long-term component are subject to high uncertainties.     

A comparison of 90Sr and 137Cs uptake in plants via three pathways at two Chernobyl-contaminated sites

Foliar absorption of resuspended 90Sr, root uptake and contamination adhering to leaf surfaces (i.e. soil loading) were compared at two Chernobyl-contaminated sites, Chistogalovka and Polesskoye. Although foliar absorption of resuspended 90Sr was quantifiable, its contribution amounted to less than 10% of the plants' total, above-ground contamination. Root uptake was 200 times greater than foliar absorption at the near-field site of Chistogalovka and eight times greater at Polesskoye, where the fallout consisted of the more soluble condensation-type, rather than fuel particles. Strontium's bioavailability exceeded that of 137Cs (analyzed in the same plants) by orders of magnitude when compared using concentration ratios. Simplistic, cumulative effective dose calculations for humans ingesting 90Sr- and 137Cs-contaminated plants revealed that the dose at Chistogalovka was greater from 90Sr (185 mSv vs. 3 mSv from 137Cs), while at Polesskoye the dose from 137Cs (66 mSv) was 30 times greater than from 90Sr (2 mSv).     

Sources and pathways of Sr in the North Atlantic–Arctic region: present day and global warming

The spatial and temporal distributions of the anthropogenic radionuclides ¹³⁷Cs and ⁹⁰Sr, originating from nuclear bomb testing, the Sellafield reprocessing plant in the Irish Sea (UK), and from the Ob and Yenisey river discharges to the Arctic Ocean, have been simulated using the global version of the Miami Isopycnic Coordinate Ocean Model (MICOM). The physical model is forced with daily atmospheric re-analysis fields for the period of 1948–1999. Comparison of the temporal evolution of the observed and the simulated concentrations of ⁹⁰Sr has been performed in the Kara Sea. The relative contributions of the different sources on the temporal and spatial distributions of the surface ⁹⁰Sr are quantified over the simulated period. It follows that the Ob river discharge dominated the surface ⁹⁰Sr over most of the Arctic Ocean and along the eastern and western coasts of Greenland before 1960. During the period of 1980–1990, the atmospheric fallout and the Ob river discharge were equally important for the ⁹⁰Sr distribution in the Arctic Ocean. Furthermore, an attempt has been made to explore the possible dispersion of accidental released ⁹⁰Sr from the Ob and Yenisey rivers under a global warming scenario (2 × CO₂). The difference between the present-day and the global warming scenario runs indicates that more of the released ⁹⁰Sr from the Ob and Yenisey rivers is confined to the Arctic Ocean in the global warming run, particularly in the near coastal, non-European part of the Arctic Ocean.     

Radionuclide tracing of water masses and processes in the water column and sediment in the Algerian Basin

Caesium-137 and (239,240)PU were analysed in the water column along the Algerian coast. The (137)Cs activity concentration in surface water increased from the west to the east from 1.6 to 3.3 mBq L(-1), documenting a presence of Modified Atlantic Water (MAW) in the region. Higher concentrations observed in deep waters may be due to an intrusion of Levantine Intermediate Water (LIW), which has been carrying higher levels of (137)Cs from Chernobyl accident. The (239,240)Pu sub-surface concentration peaked at about 250 m water depth as a result of biogeochemical processes in the water column. The observed (239,240)Pu/(137)Cs activity ratio at the surface (0.003) was significantly lower than that in global fallout (0.04). This decrease exceeds that expected from radioactive decay of (137)Cs, and confirms that Pu due to its adsorption on sinking particles is more effectively removed from surface layers than is (137)Cs. An increase of the (239,240)Pu/(137)Cs activity ratio with depth suggests that (239,240)Pu, similarly as (137)Cs, should be also transported by advection to maintain the observed ratios in deep waters. An intrusion of LIW may enhance therefore both the (137)Cs and (239,240)Pu concentrations in deep waters. The average (238)Pu/(239+240)Pu activity ratio in seawater was 0.03+/-0.02, confirming a global fallout origin of Pu in the Algerian Basin. Caesium-137 and (239,240)Pu inventories in the water column were estimated to be from 2.7+/-0.5 kBq m(-2) to 3.8+/-0.7 kBq m(-2), and from 13.8+/-2.6 Bq m(-2) to 41+/-7B qm(-2), respectively. The (137)Cs massic activities in surface sediment were almost constant, the average activity was 9.0+/-0.8 Bq kg(-1). Sedimentation rates obtained using the (210)Pb method were from 0.1 to 0.7 cm y(-1), and resulting penetration depths of (137)Cs in the sediment cores were from 15 to over 40 cm. The (137)Cs peaks found in the sediment cores were associated with the Chernobyl accident (1986) and global fallout (1964). The (137)Cs inventories in the sediment were increasing from the west (180 Bq m(-2)) to the east (350 Bq m(-2)).     

A rapid method for 90Sr determination in the presence of 137Cs in environmental samples

A rapid method for the determination of 90Sr in the presence of 137Cs using the Cherenkov radiation technique is described. The contribution of 137Cs to gross Cherenkov radiation (90Y + 137Cs) was examined for 137Cs /90Sr ratios ranging from 0.09 to 2.50 for 137Cs activities ranging from 2 to 1,211 Bq. Results from direct Cherenkov radiation measurement and results after radiochemical separation of 90Y from 90Sr for samples containing both 90Sr and 137Cs were compared. Errors below 5% were obtained for 137Cs /90Sr ratios lower than 1, when no separation was performed, independently of the activity level. However, errors between 10% and 35% were obtained for 137Cs/90Sr ratios higher than 1. In order to determine 90Sr activity in the presence of 137Cs using the Cherenkov technique, a multiple linear regression analysis model was established to correct the data for 137Cs content. The mathematical correction proposed was validated using 66 artificially contaminated lettuce samples in a laboratory experiment by taking into account the activity levels of 137Cs and 90Sr and the radionuclide ratios. Comparison of mathematically corrected radionuclide ratios with the results obtained without correction shows that, for radionuclide ratios higher than 1, error values for measuring 90Sr activity using the mathematical model were much smaller than when no radiochemical separation was performed. On the other hand, for ratios lower than 1, error values when measuring 90Sr activity with radiochemical separation were smaller than when mathematical correction was performed. In spite of this, the mathematical correction is an appropriate way of reducing the time needed to determine radiostrontium using the Cherenkov radiation technique. The method proposed could be a powerful tool for environmental research whenever the contents of 90Sr and 137Cs have to be determined.     

The transfer of 137Cs and 90Sr from feed to rabbits

Radiological assessment of the impact of nuclear weapons testing on the local population in the Semipalatinsk Test Site (STS) requires comprehensive site-specific information on radionuclide behaviour in the environment. However, information on radionuclide behaviour in the conditions of the STS is rather sparse and, in particular, there are no data in the literature on parameters of radionuclide transfer from feed to rabbit products which have been identified as contributors to internal dose to the inhabitants. The transfer of (137)Cs and (90)Sr to rabbit meat was studied under laboratory conditions in a controlled experiment with 32 locally bred rabbits maintained in the Kazakh Agricultural Research Institute. The equilibrium transfer coefficients for (137)Cs and (90)Sr from feed to rabbit meat were estimated to be 0.4 d kg(-1) and 0.15 d kg(-1), respectively. The biological half-lives were estimated to be 0.1 d for (137)Cs and 0.14 d for (90)Sr. Whereas for (137)Cs the distribution in the body is relatively homogeneous, there are large differences between the organs and tissues for (90)Sr for which, as expected, the highest concentrations were found in bone.     

Current contamination by 137Cs and 90Sr of the inhabited part of the Techa river basin in the Urals

Previous discharges of radioactivity from the Mayak Production Association plant in the Urals have resulted in considerable radionuclide contamination of the Techa River, and consequent high radiation doses during the late 1940s and 1950s to residents of villages along the Techa river. The most contaminated villages close to the site were evacuated in the period 1954-1962. The objective of this recent study was to conduct a preliminary assessment of the current radioactive contamination of soil, vegetation and foodstuffs in the two remaining villages closest to the Mayak site, Muslyumovo and Brodokalmak. The highest contamination levels in soil were found in the floodplain at 5.5 MBq m(-2) for 137Cs and 1.0 MBq m(-2) for 90Sr. Radionuclide contamination in soil of the villages was much lower, but exceeded that expected from global fallout. Data from 1207 measurements of 137Cs in milk and 1180 for 90Sr in milk for the period 1992-1999 were collated. There was no change with time in the 90Sr or 137Cs activity concentration in milk over the measured period. There were significantly higher 137Cs activity concentrations in milk sampled during the housed winter period in Muslyumovo compared with the grazing summer period, but compared to that for Brodokalmak or for either settlement for 90Sr. The highest measured activity concentrations in food products of 137Cs and 90Sr were found in river fish, waterfowl, poultry and milk. The measured activity concentrations of 137Cs and 90Sr in some animal products were higher than that expected from soil and vegetation from fields and pasture in the villages (not including the floodplain) confirming that the highly contaminated floodplains are contributing to contamination of some animal products.     

The current content of artificial radionuclides in the water of the Tobol-Irtysh river system (from the mouth of the Iset River to the confluence with the Ob River)

Data on content of (90)Sr, (137)Cs, (239,240)Pu and (3)H in water of the Tobol-Irtysh part of the Techa-Iset-Tobol-Irtysh-Ob river system (through which the "Mayak" PA radioactive wastes are transported) are presented and discussed. The data were received in 2004-2005 under the ISTC project on radioecological monitoring of the Tobol and Irtysh rivers. Monthly observations of (137)Cs, (90)Sr and (3)H content in water in the area of the Tobol and Irtysh confluence have been conducted starting from May 2004. To obtain information on the investigated river system as a whole, the radioecological survey of the Tobol and Irtysh rivers at the section from the mouth of the Iset River to the confluence with the Ob River was carried out in 2004. It is shown that the impact of "Mayak" PA waste transport by (90)Sr is distinctly traced as far as the area of the Irtysh and Ob confluence.