Half-life Of 137Cs Research Articles

Ecological Half-Life of 137Cs in Fish

In this study, the long-term (i.e., over a 27-year period) dynamics of 137Cs content are presented for seven species of fish in both the cooling pond (CP) of the Chornobyl Nuclear Power Plant and the Kaniv Reservoir (KR). The decline of 137Cs specific activity in fish exhibits various patterns. For certain years in the KR, fish belonging to different ecological groups experienced an increase rather than a decrease in specific activity levels of 137Cs. From 2012 to 2014, the concentration of 137Cs in all studied species in the KR ranged from 4 to 23 Bq/kg. In the CP during 2012–2013, fish still showed high contamination levels, ranging from 770 to 8300 Bq/kg. The ecological half-life (Teco) was determined for all the studied fish species. For most fish species (i.e., P. fluviatilis, B. bjoerkna, A. brama, S. lucioperca, A. aspius), the shortest 137Cs Teco values were obtained in the CP, being a highly radiocaesium-contaminated waterbody. In contrast, two fish species (R. rutilus and S. glanis) in the CP exhibited a considerably slower rate of 137Cs removal from their bodies compared to even the relatively cleaner KR. Moreover, the 137Cs Teco in R. rutilus and S. glanis was nearly twice as long as that observed in other species within the CP. We assume that the redistribution of 137Cs in the body of fish is affected by multidirectional mechanisms: accumulation, retention, and/or excretion. The functioning of these mechanisms can vary among different fish species. The observed level of 137Cs content in a particular fish species at a given time point results from the combined effects of these mechanisms. Fish likely have the ability to absorb and accumulate radiocaesium in their bodies selectively, and this demand appears to be species-specific.

Impact of long-term operation of nuclear power plants on the marine ecosystem of Daya Bay

Based on the monitoring data of Daya Bay in 2011–2017, the impact of long-term operation of nuclear power plants (NPPs) on the marine ecosystem was accessed. 137Cs and 90Sr in seawater and sediment of Daya Bay decreased with time. The environmental half-lives of 137Cs and 90Sr in seawater, 137Cs in sediment were 7.1 a, 11.7 a and 13.9 a, respectively. The total dose rates of the marine organisms ranged from 230.5 to 853.9 nGy/h, lower than the ERICA screening benchmark (10 μGy/h). 210Po, 226Ra and 232Th were the main dose contributors. 137Cs and 90Sr contributed to ~0.01 %–~0.06 % of the total radiation. 137Cs contributed to <0.6 ‰ of the committed effective dose for humans. There were almost no radiation effects on the marine ecosystem of Daya Bay from NPPs before 2017. In the future, there will be no radiation risk for the long-term discharge of low-level radioactive waste to Daya Bay.

Thirty-year simulation of environmental fate of 137Cs in the Abukuma River basin considering the characteristics of 137Cs behavior in land uses

The Fukushima Daiichi Nuclear Power Plant accident caused a radioactive contamination of deposited radionuclides, including 137Cs, on the land surface. Cesium-137 deposited on the land surface was strongly adsorbed on soil particles and was then washed off through soil erosion. Trends of temporal variation of 137Cs wash-off varied greatly depending on land use. Therefore, it is important to reflect the characteristics of 137Cs migration processes in each land use to clarify the long-term fate of 137Cs. In this study, a 30-year simulation of environmental fate of 137Cs was conducted using a distributed radiocesium prediction model, taking into account the characteristics of the 137Cs behavior in each land use. Overall, in the Abukuma River basin, the 137Cs transported into the ocean for 30 years was estimated to correspond to 4.6 % of the initial deposition in the basin, and the effective half-life of 137Cs deposited in the basin was estimated to be 3.7 years shorter (by 11.6 %) than its physical half-life. These results suggested that 137Cs deposited from the accident could still remain for decades. Based on the analysis of the 137Cs behavior in land use, in 2011, the contribution of 137Cs export to the ocean from urban lands was estimated to correspond to 70 % of the total 137Cs export. Meanwhile, from 2012 to 2040, the contribution of 137Cs export from agricultural lands was estimated to correspond to 75 % of the total 137Cs export. The reduction ratios excluding radioactive decay of 137Cs remained in areas with and without human activities for 30 years after the accident, defined as the ratios of the total outflow to the initial deposition, were estimated to be 11.5 %–17.7 % and 0.4 %–1.4 %, respectively. These results suggested that human activities enhance the reduction of 137Cs remaining in land in the past and future.

Dynamics of &lt;sup&gt;137&lt;/sup&gt;Cs Transfer Factors to Agricultural Products after the Chernobyl Accident: Grain, Potatoes, and Vegetables

The results of the analysis of the 137Cs aggregated transfer factors (Tag) to crops (cereals, potatoes, and vegetables) produced in the districts of the Bryansk region affected after the Chernobyl accident are presented. The aggregated transfer factors in the year of the deposition as well as the dynamics of Tag in the subsequent years depended considerably on the fertility of soils subjected to contamination. The transfer factors of 137Cs to crops in the areas with higher fertility were 3–8 times lower (depending on the plant species) than in the areas with low fertility, and the most significant differences were observed for cereals. Decrease in Tag values was of irregular nature. The half-lives of 137Cs aggregated transfer factors for the period from 1986 to 2021 were calculated. It is shown that the first half-life values calculated for the period of intensive application of countermeasures (1987–1991) were from 0.7 to 1.4 years. The second half-lives varied from 7.3 to 17.3 years. In some areas, after a strong reduction in 137Cs concentrations in crops after 1994, there was a slow increase in 137Cs aggregated transfer factors, which can be explained by insufficient compensation for this decrease of geochemical binding of 137Cs in the soil. Later the dynamics of crop contamination was determined by multidirectional processes: i.e., increase in 137Cs transfer to plants and natural decrease of radionuclides bioavai-lability in soils under the influence of geochemical processes. In areas with intensive application of countermeasures, the reduction of Tag to crops was determined to a greater extent by the influence of agrochemical countermeasures. In the areas with limited application of countermeasures, the natural biogeochemical processes determining radionuclide binding by the soil-absorbing complex made the predominant contribution to the Tag reduction. Limitations of the approach based on the estimation of half-lives and the necessity of using the history of countermeasures implemented, as well as the soil fertility for prediction of the 137Cs intake by plants is noted.

Effective half-lives for 137Cs in dairy milk from alpine ecosystems and the controlling factors

Alpine regions in the federal state of Salzburg (Austria) have been intensively contaminated by Chernobyl fallout, necessitating long-term monitoring programs. The sites predominately affected are those in areas with soil developed on silicate bedrock, as these soils tend to be acidic, favouring high transfer factors for 137Cs. In addition, nutrient deficiency, low mineral and high organic matter content, and tough climatic conditions are causing the slow migration of 137Cs in the soil, which are associated with long effective half-lives in the biosphere.As a quantitative measure for effective half-lives, milk has been collected at nine alpine seasonal stock farming sites since 1988; at four sites, the monitoring is still ongoing (2020). For the period between 1999 and 2020, the decrease of 137Cs can be reasonably fitted with one effective half-life describing the time-trend. The effective half-lives obtained by this procedure vary between 9.3 ± 0.9 years and 18.8 ± 3.4 years. The effective half-lives show a weak negative correlation with the half-value depth of 137Cs, defined as the depth of the upper soil layer containing half of the deposited fallout inventory. The majority of the inventory is bound in the rooting zone of 0–10 cm, which is reflected by the small half value depths in the range between 3.2 and 4.4 cm.The soils investigated are acidic with pH values between 3.78 and 4.88, showing a pronounced negative correlation with the effective half-lives of 137Cs in milk. The data indicate that in these soils rich in organic matter, which are also almost totally devoid of clay minerals and have a very low clay size fraction, pH may be the dominating factor influencing the effective half-lives of 137Cs plant uptake and the subsequent contamination of milk.

Using environmental tracers to understand soil organic carbon and soil erosion on a steep slope hillslope in south-east Australia

Context It is well recognised that soil organic carbon (SOC) can be transported and deposited along the same pathways as those of soil erosion and deposition. Aims To examine the viability of environmental tracers 137Cs and unsupported 210Pb (210Pbex) as tools to inform soil erosion and deposition patterns as well as that of the distribution of SOC. Methods Multiple soil cores were collected along two transects of similar length and aspect in a steep-slope soil mantled environment in south-east Australia. Key results Average SOC concentration was high for both transects (~6% and 4%). SOC decreased moving downslope suggesting loss of SOC by erosion. There were strong and significant positive relationships of SOC with 137Cs and 210Pbex (both r &gt; 0.77, P &lt; 0.0001). At this site, SOC concentration appears related to erosion and deposition patterns. Conclusion The hillslope distribution of 137Cs and 210Pbex were very similar, indicating that both tracers were viable in this environment (r = 0.9, P &lt; 0.0001). The different origins and half-lives of 137Cs and 210Pbex also demonstrate that the patterns of erosion and deposition are consistent at decadal time scales. Implications The use of 210Pbex provides an alternative method for understanding erosion and deposition patterns as well as that of SOC, given that the viability of 137Cs (half-life of 30.1 years) is now questionable due to no new replenishment.

Ecological Half-Life of 137Cs in Fungi

The ecological half-life of 137Cs was calculated individually for four symbiotrophic fungi species (Boletus edulis, Imleria badia, Suillus luteus, Paxillus involutus) at 10 sampling sites in the Chornobyl exclusion zone and in the Kyiv region. It was found that the maximum rate of excretion of 137Cs from the fungi organisms is characteristic for the territory with the maximum levels of soil contamination, i.e., for a zone near Chornobyl Nuclear Power Plant. In areas with low 137Cs content, a slowing down of the excretion rate predominates. These results reveal different fungal response to the distinct concentration levels of 137Cs in forest ecosystems. This observation further suggests that radiocaesium can be selectively accumulated by fungi and used in their life processes. Presence of this 137Cs retention mechanism in fungi leads to a longer contamination of woody plants-symbionts.

The association between upper gastrointestinal endoscopic findings and internal radiation exposure in residents living in areas affected by the Chernobyl nuclear accident.

Many people living around the Chernobyl Nuclear Power Plant (CNPP) have been exposed to 137Cs for several decades after the CNPP accident. Although half-life of 137Cs is about 30 years, some wild forest foodstuffs are contaminated by 137Cs even now. We pointed out in a previous report that low-dose internal radiation has been occasionally detected in people's body. Moreover, some doctors in local hospitals have claimed that internal exposure from contaminated foodstuffs may affect the digestive organs and possibly cause gastrointestinal (GI) diseases. Thus, we attempt to assess whether internal radiation exposure affects digestive organs or not, and the possible factors that influence digestive organs. Overall, 1,612 residents were assessed for internal 137Cs concentration using Whole-Body Counter and their digestive organs were screened with upper GI endoscopy from 2016-2018 in the Zhytomyr region, Ukraine. All participants answered to the questionnaire including their background, intake of wild forest foodstuff, intake frequency, smoking habits, and alcohol consumption. We checked the number of upper GI endoscopic diagnosis per person to assess the extent of damage to the upper digestive organs. Next, we statistically analyzed associations between this number and age, sex, level of internal exposure dose, alcohol consumption, wild forest foodstuff intake, and smoking. Consequently, we revealed that the number of GI diagnosis is significantly increased by factors such as sex, intake of wild forest foodstuff, and alcohol consumption. However, the average level of internal exposure of 137Cs and smoking did not relate to the number of GI diagnosis. Thus, the results of multiple regression revealed that alcohol consumption is independently related to the number of GI diagnosis that is most likely accompanied by the intake of wild forest foodstuff. In conclusion, the low-dose internal exposure may not affect the digestive organs of residents living around CNPP.

Exemplifying the “wild boar paradox”: dynamics of cesium-137 contaminations in wild boars in Germany and Japan

Wild boars (Sus scrofa) are notorious for accumulating high contamination levels of 137Cs in their meat. Publicly available data of 137Cs contamination levels in wild boars from 2011 to 2019 were used to determine some radioecological characteristics in Germany (affected by Chernobyl-fallout, 1986) and Japan (affected Fukushima, 2011). The effective half-life of 137Cs in wild boar meat was much longer in Germany (7.3 y) than in Japan (2.6 y), respectively. Wild boars in Germany thus show much more persistent contamination levels than other game or forest animals. This unusual behavior has been termed “wild boar paradox.” In German wild boars, the data sets reveal a distinct geographical and seasonal dependence with higher activity concentrations in winter than in summer. In Japan, contamination levels only exhibit a distinct decline behavior.

Improvement in potassium budget with water outflow reduction through reducing excessive irrigation in a paddy field

ABSTRACT Countermeasures to reduce radiocesium uptake by crops have been implemented in farmlands affected by the accident at Tokyo Electric Power Company’s Fukushima Daiichi Nuclear Power Plant in 2011. A widely practiced countermeasure is the application of K. Long-term maintenance of soil K is crucial due to the long physical half-life of 137Cs (30 years). Plant-available K budgets can be used as an indication of sustainable maintenance. Our previous study found that large water outflow, especially percolation, associated with excessive irrigation caused major K outflow and a negative K budget in a paddy field in Fukushima in 2018. The present study evaluated whether decreasing the water outflow by reducing the irrigation volume from 6300 to 1900 mm reduced K outflow and improved the K budget in the field during the cropping period in 2019. K concentrations in soil solution were comparable in both years, and the percolation water volume decreased to 37% that of 2018, resulting in a 53% reduction in the K output from 392 to 184 kg ha–1. The input via irrigation also decreased (−35 kg ha–1), but the output via surface runoff showed a greater reduction (−58 kg ha–1) owing to a 70% decrease in the water volume compared with 2018. Consequently, the K budget was substantially improved (from −289 to −57 kg ha–1), highlighting the importance of controlling water outflow, particularly percolation, for soil K maintenance in paddy fields with high permeability.

Environmental recovery from 137Cs contamination in Japanese coastal waters shown by comparison of temporal distributions with European seas

We compared the spatiotemporal distributions of 137Cs in the European Baltic Sea (semi-enclosed) and the North and Norwegian Seas (open to the ocean) after the Chernobyl Nuclear Power Plant (CHNPP) accident, with those in Japanese coastal regions, including the waters off Miyagi, Fukushima, and Ibaraki prefectures, open to the western North Pacific, after the Fukushima Nuclear Power Plant accident. The effective half-lives 1–9 years after each accident were shortest (1.6–4.7 y) in Japanese coastal waters, 4.9 y in the North Sea, and 14.4 y in the Baltic Sea, suggesting that decreases in 137Cs concentrations are largely dependent on the local geography, and that the dilution–diffusion effect of seawater was greater in the Japanese coastal waters. The effective half-lives of 137Cs in the surface waters of European seas, based on 30 years of data after the CNPP accident, became longer, ranging from 8.4 to 11.9 y. This may be due to the influence of rivers, and a delay in the decrease in 137Cs levels caused by the small difference in radioactivity concentrations between the seas and diluting waters. These results could contribute to the prediction of contamination levels in Japanese coastal waters in the future.

Benthic food web structures as an explanation for prolonged ecological half-life of 137Cs in flatfish species in the Fukushima coastal area

After the accident at the Fukushima Daiichi Nuclear Power Plant (FDNPP), Japan, in March 2011, 137Cs in demersal fish had, between 2011 and 2015, a prolonged ecological half-life when compared to pelagic fish. Using stable isotope mixing models combined with gut content analysis and 137Cs activity concentrations, this study investigated the hypothesis that an unexplored food web structure could be a contributing factor explaining the ecological half-life of 137Cs in benthic flatfish. Benthic invertebrates and demersal fish species sampled in 2015 still showed 137Cs activity concentrations higher than pre-accident. The mixing models of stable N and C isotopes and gut content analysis identified deposit, suspension and filter feeders to be the main flatfish food items in the benthos. There was a significant correlation between 137Cs activity concentrations in specific flatfish species and benthos, and between 137Cs activity concentrations in benthos and surface sediment. The results of this study partially explained the 137Cs activity concentrations found in the analysed demersal fish, suggesting that the benthos can be a continuous source of 137Cs for the demersal fish during this period of time. Extending monitoring programmes to include invertebrates that are not food species for humans would greatly improve our ability to understand the role of trophic transfer pathways and take appropriate management actions.

Eight-year variations in atmospheric radiocesium in Fukushima city

Abstract. After the Fukushima nuclear accident, atmospheric 134Cs and 137Cs measurements were taken in Fukushima city for 8 years, from March 2011 to March 2019. The airborne surface concentrations and deposition of radiocesium (radio-Cs) were high in winter and low in summer; these trends are the opposite of those observed in a contaminated forest area. The effective half-lives of 137Cs in the concentrations and deposition before 2015 (0.754 and 1.30 years, respectively) were significantly shorter than those after 2015 (2.07 and 4.69 years, respectively), which was likely because the dissolved radio-Cs was discharged from the local terrestrial ecosystems more rapidly than the particulate radio-Cs. In fact, the dissolved fractions of precipitation were larger than the particulate fractions before 2015, but the particulate fractions were larger after 2016. X-ray fluorescence analysis suggested that biotite may have played a key role in the environmental behavior of particulate forms of radio-Cs after 2014. However, the causal relationship between the seasonal variations in particle size distributions and the possible sources of particles is not yet fully understood. The current study also proposes an evaluation method of the consistency of a numerical model for radio-Cs resuspension and suggests that improvements to the model are necessary.

Evaluation of transfer factor and ecological half life of 137Cs in terrestrial matrices around Kakrapar Gujarat Site, India during 1993–2019

Evaluation of transfer factor and ecological half life of 137Cs in terrestrial matrices around Kakrapar Gujarat Site, India during 1993–2019

Two stages in the accumulation of 137Cs by mushroom Suillus luteus after the Chornobyl accident

Studies of the 137Cs content in fruit bodies of Suillus luteus in the territory of the Chornobyl exclusion zone and Kyiv region outside the zone were carried out during the period 1986 - 2020. It was found that the dynamics of 137Cs activity in the mushroom can be described as a two-stage process. The first stage since 1986 was characterized by the annual increase in levels of specific activity of 137Cs for the following 10 - 12 yrs. During the second stage, there has been a gradual decrease in concentrations of 137Cs. The ecological half-life of 137Cs in the mushroom at the second stage differs for different sampling sites. Its minimum values were noted at villages Yaniv and Novo-Shepelychy sampling sites inside the exclusion zone. The maximum of 137Cs ecological half-life in Suillus luteus was observed on the Rzhyshchiv sampling site, which is the most remote from the Chornobyl Nuclear Power Plant outside the exclusion zone.

Вплив додаткового «чистого» годування на вміст 90Sr і 137Cs в карасях сріблястих (Carassius Gibelio) у Чорнобильській зоні відчуження

Under natural conditions, in one of the most radioactively contaminated water bodies of the Chornobyl exclusion zone, lake Glyboke in 2020, experimental studies were carried out to assess the effectiveness of the use of additional "clean" feeding to reduce the levels of radioactive contamination of 90Sr and 137Cs in fish. The radiological efficiency of decreasing the 137Cs intake into the muscle tissue of fish with the use of additional "clean" feeding, mainly due to biological dilution, was 2.9 ± 0.4 times. The biological half-life of 137Cs in the muscle tissue of radioactively contaminated fish was 115 ± 25 days with the consumption of natural and additional "clean" food, which is approximately 2 times longer compared to the case when the fish consumes only clean food. In contrast to 137Cs, using additional "clean" feeding led to an increase of 90Sr content in the fish organism as compared to the control (up to 5 times) in proportion to the relative increase in the mass of fishbone tissue, which contains the bulk of strontium.

Seasonal changes in uptake and depuration of 137Cs and 90Sr in silver Prussian carp (Carassius gibelio) and common rudd (Scardinius erythrophthalmus)

Dynamic transfer of radionuclides to fish was studied in a series of experiments under field condition in two lakes within the Chernobyl exclusion zone during 2016–2020. “Clean” common rudd (Scardinius erythrophthalmus) and silver Prussian carp (Carassius gibelio) were transported to the contaminated Glubokoye Lake and kept in cages during several months of exposure, while contaminated Glubokoye fish were kept in cages in the “clean” Starukha Lake. Radiocaesium (137Cs) and radiostrontium (90Sr) were determined in intestine contents, muscle and bone tissues based on repeated samples during several months of exposure.During summer, the activity concentrations of 137Cs and 90Sr increased with time of exposure in clean fish caged in the contaminated lake. During autumn and winter, however, minor changes in fish uptake occurred during several weeks of exposure to the contaminated water. Furthermore, depuration in the contaminated fish was significant during summer, while insignificant during winter when exposed in the «clean» water. The rate constant of 137Cs uptake in muscle was between 8.0 and 22 day−1 during summer, while 0.2 to 1.0 day−1 during autumn-winter. Similarly, the rate constant of 90Sr uptake in bone was between 1.4 and 1.6 day−1, while 0.08–0.52 day−1 during autumn-winter. Biological half-lives of 137Cs in fish muscle tissue in summer were 77 ± 10 days, while exceeded 230 days during seasons at low water temperature.The results demonstrated that the transfer of 137Cs and 90Sr to fish was highly dependent upon seasons, in particular the water temperature. The transfer data obtained during low water temperature seasons deviated significantly from transfer data in literature and handbooks. Thus, seasonal changes in radionuclide transfer to fish should be taken into account when radiological impact to fish is assessed.

INTENSITY OF CESIUM-137 ACCUMULATION IN FLOWER POLLEN OF CORN AT DIFFERENT pH OF SOIL ENVIRONMENT

137Сs is concentrated in soils and is in a continuous cycle, the intensity of movement of which depends on a number of factors, in particular on the type of soil, its composition and properties, botanical origin of plants and others. . It was found that under the same ecological conditions the accumulation coefficient of 137Cs in the distribution of honey plants can differ up to 3 times. The migration of radionuclides into vegetation is lower on soils with high levels of nutrients, compared to low-nutrient soils. This feature is inherent in both agricultural and forest soils. High migr ation of radionuclides was observed on sod-podzolic sandy soils, while on chernozems it was relatively lower. Soils of honey lands in the studied areas are mainly sod-podzolic. They are characterized by a low content of humus and trace elements, sometimes with high acidity, which can increase the translocation of radionuclides in plants and their products, in particular pollen. After the half-life of 137Cs, which was released into the environment after the Chernobyl accident, there is a certain pattern of intensity of contamination of protein products of beekeeping depending on its type, harvesting period and intensity of contamination of honey lands. Along with this, it should be noted that the exceedance of permissible levels is observed only for cesium-137 in the territory of honey lands in the soil of which this element exceeded 4 Ki / km2. On the basis of the fact that pollen is the main raw material for the production of protein products of beekeeping, further research was aimed at studying measures to improve the quality of this raw material in order to reduce cesium-137 in bee pollen and persimmon. The intensity of 137Cs contamination of corn pollen was studied. It was found that lowering the soil pH from 4.6 to 7.7 contributes to a decrease in the pollen of maize pollen activity 137Cs from 9.7 Bq / kg to 5.8 Bq / kg, hazard factor from 0.049 to 0.029 and accumulation factor from 0 , 28 to 0.14.

Achieving highly efficient and selective cesium extraction using 1,3-di-octyloxycalix[4]arene-crown-6 in n-octanol based solvent system: experimental and DFT investigation.

Due to the long half-life of 137Cs (t1/2 ∼ 30 years), the selective extraction of cesium (Cs) from high level liquid waste is of paramount importance in the back end of the nuclear fuel cycle to avoid long term surveillance of high radiotoxic waste. As 1,3-di-octyloxycalix[4]arene-crown-6 (CC6) is suggested to be a promising candidate for selective Cs extraction, the improvement in the Cs extraction efficiency by CC6 has been investigated through the optimization of the effect of dielectric media on the extraction process. The effects of the feed acid (HNO3, HCl, and HClO4) and the composition of the diluents for the ligand in the organic phase on the extraction efficiency of Cs have been investigated systematically. In 100% n-octanol medium, Cs is found to form a 1 : 1 ion-pair complex with CC6 (0.03 M) providing a very high distribution ratio of DCs ∼ 22, suggesting n-octanol as the most suitable diluent for Cs extraction. No significant interference of other relevant cations such as Na, Mg and Sr was observed on the DCs value in the optimized solvent system. Density functional theory (DFT) based calculations have been carried out to elucidate the reason of ionic selectivity and enhanced Cs extraction efficiency of CC6 in the studied diluent systems. In addition to the ionic size-based selectivity of the crown-6 cavity, the polarity of the organic solvent system, the hydration energy of the ion, and the relative reorganization of CC6 upon complexation with Cs are understood to have roles in achieving the enhanced efficiency for the extraction of Cs by the CC6 extractant in nitrobenzene medium.

Виведення 137Cs з організму карася сріблястого (Carassius gibelio) за різної температурі води у природних умовах Чорнобильської зони відчуження

After the accident at the Chernobyl nuclear power plant, the activity concentration of radionuclides in fish reached hundreds of kBq kg-1. Determination in the dynamics of the content of radionuclides in the body of fish is necessary for the radiation protection of humans and the environment. The data presented in the literature are extremely contradictory and such large differences in the main parameters of radionuclide metabolism in fish require clarification in nature conditions. The aim of this work was to determine the rate of excretion (biological half-life) of 137Cs from the body of silver Prussian carp (Carassius gibelio) at different water temperatures (1-29 °С) depending on the weight of the fish (20±5 and 40±6 g) in real conditions of the Chernobyl Exclusion Zone. As a result of experimental studies, the values of the biological half-life of 137Cs for silver carp was 193-495 days at water temperature 3.7±0.9 °C and 63-92 days at water temperature 22±4 °С were obtained. Due to an increase in the weight of fish (biodilution) at water temperatures &gt; 13 °C, the half-life of the activity concentration of 137Cs in the muscle tissue of fish decreased to 39-58 day-1. The obtained data correspond to the previously obtained values in aquarium experiments. The results obtained in this work show that the level of radioactive contamination of fish in winter will change slightly compared to summer time, which is also confirmed by experimental data obtained in aquarium experiments.