Specific Activity Of Natural Radionuclides Research Articles

РАДИОЭКОЛОГИЧЕСКАЯ ОБСТАНОВКА В РАЙОНЕ ПЛОЩАДКИ УРАНОВОГО НАСЛЕДИЯ – ШАХТА «СТЕПНАЯ» (КАЛМЫКИЯ)

Purpose: To study the radio-ecological situation on the “uranium legacy” site of the former Stepnaya mine in the Republic of Kalmykia. Material and methods: To measure the ambient dose equivalent rate (ADER), the pedestrian gamma survey method was used using a portable spectrometric complex MKC-01A Multirad-M and dosimeter-radiometer MKC-AT6101c. The activity of gamma-emitting radionuclides in soil samples was measured using a stationary gamma spectrometer from CANBERRA. The activities of 210Po and 210Pb were measured using a radiometric installation UMF-2000 following their radiochemical separation from samples. Short-term measurements of activity concentration (AC) and equivalent equilibrium activity concentration (EEAC) of radon were carried out with an aerosol alpha radiometer for radon and thoron RAA-20P2 Poisk. Doses of radiation exposure to biological objects were estimated using dose coefficients provided by ICRP Publication 136 taking into account recommendations R52.18.820-2015. Results: Gamma ADER values at the mine site vary over the range from 0.1 to 0.36 µSv/h, and on 80 % of the area these values do not exceed the background value of 0.14 µSv/h. Along the road from the mine to Narta village the ADER values do not exceed background values with exception of the area around the dam, where in a local part of this area of about 300 m2 these values reach 0.49 µSv/h. The specific activities of natural radionuclides in the soil are below the criteria for classification as solid radioactive waste (SRW). Under the certain weather conditions, radon EEAC inside the buildings on the site reaches 13 kBq/m3, and on the territory 1-1.5 kBq/m3. Ecological risk for the terrestrial biological objects under consideration (grass, soil worm, snake and mouse-like rodents) does not exceed 0.025. Conclusions: The radiation situation at the Stepnaya mine site meets the requirements of SP LKP-91, which were in force until 2020. However, in order to transfer the facility to a local government body, reclamation work should be carried out in accordance with the Federal Law “On the Transfer of Lands or Land Plots from One Category to Another” dated December 21, 2004 No. 172-FZ and GOST R 59057— 2020 «Environmental Protection. Lands. General Requirements for Reclamation of Affected Lands». Doses of exposure to biological objects do not impact significantly on morbidity, reproduction and life expectancy of terrestrial biological objects.

Spatial distribution of 137Cs; 40K, 226Ra, 232Th in soils of Monchegorsk city (Murmansk region)

The purpose of the study was to establish the patterns of spatial distribution of radioactivity of technogenic 137Cs and natural radionuclides 232Th, 226Ra, 40K in urban soils of Monchegorsk. Location and time of the study. Soil samples, were collected in summer 2018 in the Monchegorsk city, Murmansk region, Russia. To study the specific activity of radiocesium and natural radionuclides, soil samples were taken from topsoil (0-5 cm) at 82 sites, including 68 sites within the city territory (urban soils) and 14 sites beyond the city limits in the subtorch areas strongly affected by the Severonickel factory. Similar studies of urban soils in Monchegorsk had not been carried out previously. Methods. During expeditionary work and laboratory research, soil, radiological, and mathematical and statistical methods were used. When carrying out gamma spectrometric measurements, radionuclides 137Cs, 226Ra, 232Th and 40K were determined on a low-background semiconductor gamma spectrometer ORTEC (USA) based on a high-purity coaxial germanium detector GEM10P4–70 (HPGe) with a SBS-75 pulse signal processor and Gamma-software. The resolution of the gamma spectrometer along the 1.33 MeV line (60Co) was 1.75 keV, and the relative efficiency was 15%. Calibration and quality control of gamma spectrometric measurements was carried out using volumetric activity measurements with 1-L Marinelli vessels of different densities (RITVERZ, Russia-Germany). Main results. The values of specific activity of radionuclides in soil samples were as following: in the technogenic 137Cs up to 31.3 Bq/kg and in the subtorch soils up to 63.4 Bq/kg. Specific activity of natural radionuclides in urban soils reached to 14.2 Bq/kg for 226Ra, whereas in the subtorch soils it reached 21.6 Bq/kg. The specific activity of 232Th in urban soils reached 18.3 Bq/kg, with 17 Bq/kg registered for the subtorch soils. As for 40K, its specific activity reached 498 Bq/kg in the urban soils and 317 Bq/kg. Conclusion. The gamma survey of the Monchegorsk territory did not reveal any anomaly in radiation. The dose rate of gamma radiation in the city does not exceed 0.074 μSv/hour, which is less than the values elsewhere in Russia, ranging from 0.04 to 0.20 μSv/hour. The obtained data about specific activity of technogenic 137Cs and natural radionuclides 232Th, 226Ra, 40K in the Monchegorsk soils are typical for the Murmansk region.

Radiometric measurements at uranium mined-out sitesbefore their reclamation

The article presents the results of radiometric measurements of various indicators for objects at uranium mined-out sites before their reclamation: specific activity of natural radionuclides, total effective activity, specific alpha activity, pH value of water extract, exposure dose rate of gamma radiation, equivalent equilibrium volumetric activity of radon, content of long-lived radioactive aerosols in the air, and density of radon molasses. The results were compared with the regulatory requirements established for both the population and personnel. The article shows that the radiation indicators at a man-made object differ from the background values for natural objects, i.e., uranium mining is a source of radioactive pollution of the environmen.

Natural radioactivity measurements and evaluation of radiological hazards in the soil of an iron beneficiation plant in China

The specific activities of natural radionuclides, 232Th, 226Ra, and 40K, in a Chinese iron beneficiation plant and surrounding soil were analyzed with the high purity germanium gamma (HPGe) spectrometer in this study. Average specific activities of 238U, 232Th, 226Ra and 40K lower than the Chinese averages. To assess radiation impact, various indicators, radium equivalent index (Rae q), absorbed dose rate (DR), annual effective dose (AED), excess lifetime cancer risk (ELCR), external hazard index (Hex), internal hazard index (Hin) and activity utilization index (AUI), were calculated. Mean values were below international limits, indicating no significant health hazards for the local population. Statistical analyses, including skewness and kurtosis calculations, along with techniques like frequency distribution, Pearson's correlation analysis, box plots and cluster analysis, were applied to comprehensively assess distribution patterns and interrelationships among radiological parameters. In summary, there are no potential health hazards associated with the soil in the study region for people.

Радиоэкологическая обстановка в районе вводимого в эксплуатацию рудника № 6 пао «Приаргунское горно-химическое производственное объединение»

Purpose: Study of the radioecological situation around mine No. 6 of PJSC ‘Priargunsky Industrial Mining and Chemical Association’ named after E.P. Slavskiy" before commissioning. Material and Methods: During the radiation survey, to measure the ambient dose equivalent rate, the pedestrian gamma survey method was used using the portable spectrometric complex MKS-01A ‘Multirad-M’ (Russia) and the dosimeter-radiometer MKS-AT6101s (Belarus). To study the specific activity of radionuclides in the soil, samples were taken in accordance with GOST 17.4.3.01-2017. The activity of gamma-emitting radionuclides was measured on a stationary gamma spectrometer manufactured by Canberra (USA). The activity of 210Po and 210Pb was measured on the radiometric system UMF-2000 (Russia) after their radiochemical extraction from samples. Dose assessment of exposure to biological objects was made using dose coefficients established in ICRP Publication 136, considering recommendations R52.18.820-2015. Results: The results of the study showed that the ambient dose equivalent rate of gamma radiation varied in a wide range from 0.1 to 4.9 µSv/h. The average value in the background areas is 0.14±0.02 µSv/h. The specific activity of natural radionuclides outside the rock dumps, except for 40K, in some areas exceeds the background values up to 10 times. The ecological risk for the considered terrestrial biological objects (grass, shrub, soil worm and mouse-like rodents) does not exceed 10‒2. Conclusion: There are areas on the territory with traces of anthropogenic activity, which led to man-made radiation contamination. The highest levels of ambient dose equivalent of gamma radiation occur near rock dumps. The rest of the territory has local areas with radioactive contamination. Doses of exposure to biological objects don’t have a significant effect on the incidence, reproduction, and life expectancy of terrestrial biological objects.

Особенности пространственного распределения 137Cs, 40K, 226Ra, 232Th в почвах города Кировска (Мурманская область)

The article presents the results of a study of soils in the city of Kirovsk. The purpose of the work is to establish the main regularities of the spatial distribution of natural and technogenic radionuclides in the urban soils of Kirovsk. To achieve this goal, soil samples were taken in all parts of the city. The following methods were used in the course of expeditionary work and laboratory research: soil, radiological, mathematical and statistical. The values of specific activity in samples of urban soils were: for technogenic 137Cs (from 3 to 48.3 Bq/kg), for natural radionuclides: 226Ra (from 11.8 to 44.2 Bq/kg), 232Th (from 9.8 to 34.8 Bq/kg), 40K (from 232.2 to 2086 Bq/kg). The values of the effective specific activity of natural radionuclides in urban soil samples ranged from 47 to 277 Bq/kg and 137Cs from 3.2 to 48.3 Bq/kg.

Modern method for determining the specific activity of natural radionuclides

The purpose of this work is to get acquainted with the basic properties and laws of interaction with the substance of gamma radiation. The practical part of the work includes an acquaintance with the technique and technique of gamma-ray spectroscopy by the example of recording the gamma spectrum of a Cs137 preparation with a spectrometer with a scintillation detector, followed by calibration of the energy scale. After that, on a calibrated spectrometer, it is proposed to determine the attenuation coefficient and estimate the energy of gamma quanta.

ASSESSMENT OF DOSE RATE USING GAMMA RAY OBSERVATIONS IN THE MINING WASTE SAMPLES OF SIMBERI GOLD MINE IN PAPUA NEW GUINEA

The specific activity of natural radionuclides were measured by gamma ray spectrometry with NaI(Tl) detector in the mining waste soil samples collected from Simberi gold mine in New Ireland province of Papua New Guinea. The isotope concentrations of 238U and 232Th in Simberi soil samples are 10.7 and 41.3 ppm respectively whereas the world average values are 2.64 and 11.1 ppm respectively. The average Radium equivalent activity in Simberi samples is 372.2±81.4 Bq/kg which is observed to be higher than the threshold safe value of 370 Bq/kg. The average internal hazard index for Simberi samples is found to be 1.4 which is higher than the maximum permissible value of 1.0. The Excess Lifetime Cancer Risk (ELCR) is calculated to be 0.00553±0.00122 in Simberi whereas the world average value is 0.00145. Radiation in Simberi is found to be higher which may be because Simberi is situated in the volcanic region of Papua New Guinea

Assessment of natural radioactivity and its dependence on clay minerals of the soil of Dakshina Kannada district, South India

ABSTRACT The current study is the first in-depth investigation into the natural radioactivity in soils and assessment of associated radiological risks to the population in Dakshina Kannada district of southern India. The specific activity of natural radionuclides was determined by NaI(Tl) gamma spectroscopy. The trace minerals found in the soil were detected by FTIR spectroscopy and their relative distribution is quantified by calculating the extinction coefficient. The specific activity of 226Ra, 232Th, and 40K range from 9.73 ± 0.7 to 59.97 ± 1.9 Bq kg−1 with a mean of 26.47 ± 1.2 Bq kg−1, 15.88 ± 0.8 to 78.8 5 ± 2.1 Bq kg−1 with a mean of 35.45 ± 1.2 Bq kg−1 and 147.06 ± 3.4 to 535.92 ± 6.7 Bq kg−1 with a mean of 403.11 ± 5.5 Bq kg−1, respectively. The normality of frequency distribution curves of radionuclide concentrations was confirmed by the Kolmogorov–Smirnov test. The estimated hazard indices were found to be within acceptable levels. Higher levels of 226Ra, 232Th and 40K in soils were detected in certain parts of Dakshina Kannada, which was linked to the mineralogy of the region. The specific activity of radionuclides was discovered to be dependent on the minerals kaolinite and calcite. The extinction coefficients of Kaolinite, Calcite, and Quartz in soil ranged from 33.11 to 63.98, 29.63 to 111.24, and 84.47 to 115.83, respectively.

Natural radioactivity and mineralogical composition of different particle size fractions of a river sediment from Calabria, southern Italy: a case study

The natural radionuclides (238U, 232Th and 40K) content and the mineralogical characteristics of three different particle size fractions of a sediment sample from the Amendolea river, Calabria region, southern Italy, were investigated.High Purity Germanium (HPGe) gamma spectrometry was employed for the radioactivity measurements and specific activity data were reported. X-Ray Diffraction (XRD) measurements were carried out to identify the mineral contents of each particle size fraction.This case study was developed with the aim of evaluating the specific activities of natural radionuclides and their relation to specific minerals. Data obtained can provide useful information in view of a deep understanding of the adsorption of radioactive elements and the influence of the sediment granulometry on the radionuclides specific activities.

Plant uptake and soil retention of radionuclides and metals in vineyard environments.

In most European countries, each adult citizen drinks on average more than 20 L of wine every year. Three popular wine-growing areas (Aleksandrovac, Topola, and Orahovac) in Serbia were studied in order to investigate the abundance and uptake of elements from vineyard soil to plants. The specific activities of radionuclides (226Ra, 232Th, 40K, 137Cs, and 7Be) were measured in soil, leaves, and grape berries. 226Ra and 232Th were positively correlated with silt and clay and negatively correlated with sand content in soil. Specific activities of natural radionuclides were also negatively correlated with soil pH and CaCO3. Significant correlations of 40K and 137Cs with organic matter in soil were found. Concentrations of fifteen metals (As, Cd, Co, Cr, Cu, Mn, Ni, Pb, Zn, Fe, K, Na, Ca, Mg, and Hg) were also measured in soil samples as well as in grapevine leaves. Analyzed soils were rich in Ni, Cu, Co, Cr, and Cd. High concentrations of Cu were probably caused by long-term use of Cu-based fungicides. Cu was correlated with Fe and organic matter content in soil. Soil-to-plant transfer factors (TF) were calculated to estimate the uptake of radionuclides and metals. Correlations obtained via PCA enable distinction between the sites Aleksandrovac and Topola relative to Orahovac. The first principal component (PC1) accounting for 30.70% of the total variance correlated significantly with soil pH (H2O), contents of CaCO3, Na, Ca, 40K, and 226Ra in soil, as well as with 226Ra, Na, Ca in plants and TFCa. The second principal component (PC2), with total variance of 17.21%, was mainly correlated with variables pertaining to Mg, Co, and Cr in the soil and TFK.

Non-destructive measurements of natural radionuclides in building materials for radon entry rate assessment

To control the specific activity of 226Ra in building materials of operated buildings, a non-destructive in situ method consisted in measurements of gamma spectra with a fixed geometry of the detector position in a room is suggested. The calculation of the average specific activity of natural radionuclides in building materials is carried out by comparing the calculated flux density of unscattered gamma quanta normalized to the specific activity of 100 Bq/kg, and the experimentally measured count rates in the photopeak. For the measured values of the average specific activity of 226Ra in building materials, the expected values of radon concentration in rooms were calculated. The developed method has been verified for rooms in modern multi-storey energy-efficient buildings. Concentrations of 232Th and 40K in building materials which contribute to the indoor external radiation exposure can be measured by developed method also.

Heavy metals and the "Chernobyl trace" in the bottom sediments of the internal reservoir: The Gulf of Kaliningrad

Introduction. The article contains the results of a study of environmental hazards and threats to public health from the accumulation of heavy metals (HM) and the activity of man-made and natural radionuclides (NRN) in the bottom sediments of the inner reservoir r - the Kaliningrad Bay at the turn of the XX-XXI centuries (1986-2019). The Consumption of polluted resources (seafood, bottom sediments as fertilizers, and mineral raw materials) can negatively affect residents’ health of not only this region. The problems are considered: 1) the mechanism and intensity of the long-term accumulation of Hg and other HMs, 2) the activity of the 137Cs isotope (“Chernobyl trace”) and NRN in comparison with the radiation state of the beach Sands in Latvia, 3) the biomedical threats from the factors considered. Results. The water’s closed area led to the role of the bay as a giant trap of sedimentary material and pollutants. Hg in the water reached dangerous concentrations of 0.15-0.6 mcg/l (MPC = 0.5 mcg/l). The accumulation of Hg in the bottom sediments of the Gulf estuary and Primorskaya Bay has reached a low level of pollution over 20 years (Norwegian criteria: from 50-90 to 155-252 mcg/kg) and has approached the safe limit - the target level (300 mcg/kg - the national, regional standard and Dutch lists of the pollutants). The Hg content also increased in the background (from 23 to 82 mcg/kg). The most dangerous foci of sanitary and toxicological hazard (Zc-t index (AgPbCoW) >6, up to 13) coincide with the borders of dangerous accumulation of the sum of HM (Zc(MnCrVNiCoAgZnPbSnW) >34, up to 61) and Hg (>100-150 mcg/kg). The initial activity of 137Cs in the Baltics decreased, Bq/kg: from 110 (beaches of Latvia) to 104 and 99 (bottom sediments; coasts of Lithuania, Kaliningrad region, and Poland). The specific activity of NRN in the bottom sediments of the Gulf (510-572 Bq/kg) is below the safe level (740 Bq/kg); handling them has no restrictions. Conclusions. An increase in the amount of Hg causes the danger. The trend requires research and monitoring, including Hg in seafood and biomonitoring.

Удельная активность радионуклидов и их взаимосвязь с валовым химическим составом почв

The total heavy metal content and activity concentration of natural radionuclides were obtained in native and anthropogenically transformed soil of the Rostov agglomeration (south of the Russia). The specific activity of natural radionuclides in soils of the has been comparable with indicators typical for chernozems of the Rostov region. Increased activity of 40K, 232Th is observed in the upper horizons, which is due to the origin of the radionuclides themselves and fertilization in the agrogenic period of soils, before the specified areas were included in the urban area. The correlation between activity concentration of radionuclide and total content of heavy metals were derived by Spearman's Rank-Order Correlation. The study was revealed that the activity concentration of thorium and radium doesn’t provide significant correlation with the total content of heavy metals. The group of buried horizons have shown a positive correlation with naturally occurring 40K in contrast with humus horizon (AU). The carbonates-accumulating group of horizons (BCA, [BCA]) have random correlation sign by each of metals. The most significant correlation was observed for the B horizons group.

Метод неразрушающего контроля удельной активности природных радионуклидов в строительных материалах

A method for non-destructive monitoring of the content of natural radionuclides in building materials has been developed. Spectrum measurements of gamma radiation are carried out with a pre-calibrated field gamma spectrometer. The calculation of the average specific activity of natural radionuclides in building materials is carried out by comparing the calculated flux density of unscattered gamma quanta normalized to the specific activity, and the experimentally measured count rates in the photopeak. calculated for the geometry of the room under study and the location of the detector. Application of the developed method makes it possible to estimate the average activity of natural radionuclides in building materials without destruction.

Radiological Risk Assessment of Oil waste in the Oilfields at Zubair district of Basrah

The specific activities of natural radionuclides in several samples were collected from the areas that exposed to triple-aggression which is Zubair province at Basrah governorate exactly. Those samples were studied and that concentrations calculated by using Gamma spectrometry system based on HpG detector with efficiency 40% was used for analysis of NORM. Then radiological risk of the natural radioactivity was estimated for study area that caused from exist the radionuclides in surface soil and water samples. The results have been revealed the contamination that occurring in some sites of Zubair district belonging to the natural radioactive material. Activity concentrations in Bq/kg of 238U, 232Th, and 40K with mean values of 95.8 Bq/kg, 31.6 Bq/kg, and 482.18 Bq/kg respectively. The outcome of soil samples were appeared higher values when compared with international calibrations. Whereas the results of Gamma absorbed dose (nGry/h), the exposure dose rate (µR/h) have mean values non-detected like; 52.5, 12.8 respectively, where under the international average by UNSCEAR 2008. Since the Radium equivalent activity (Ra-eq) has value 295.8 Bq/kg is higher than the standardizations.

The analysis of natural radionuclides activity in the soil and vegetation cover in the South of the Tyumen Region

The paper deals with the study of the radiation state of the soil and herbaceous vegetation represented by perennial grasses (Poa pratensis, Calamagrostis epigejos, Rubus saxatilis, Carex acuta, Phleum pratense) in the south of the Tyumen Region. The content and distribution of natural radionuclides in soil and herbaceous vegetation was studied in the Nizhnetavdinsky District of the Tyumen Region at the site of an underground nuclear explosion. Sampling and laboratory tests were carried out according to generally accepted methods. Soil samples were taken at the epicenter of the explosion and at the cardinal directions. Layer-by-layer sampling allowed us to study the vertical distribution of radionuclides in the soil profile. Sampling of perennial grasses was carried out at the same sampling points. Radiation studies of soil and vegetation samples were carried out on the Progress-2000 spectrometric complex. The authors have revealed specific activity of natural radionuclides (K-40, Th-232 and Ra-226) in the profile of grey forest soil in the Nizhnetavdinsky District. They have calculated effective specific activity of radionuclides in the soil. The comparative analysis of the obtained results with the data on administrative areas in the south of the Tyumen Region showed that in the soil of the Nizhnetavdinsky District specific activity of natural radionuclides is higher than in the South region in general. The specific activity of natural radionuclides in perennial grasses of the Nizhnetavdinsky District was determined, and the coefficient of accumulation of radionuclides was calculated.

Accumulation of natural radionuclides by soil and vegetation in the South of the Tyumen region

The article is focused on the results of studying the radiation condition of the soil and grassy vegetation represented by perennial grasses (meadow bluegrass, reed warbler, stonecrop, clover, sedge, timothy) in the South of the Tyumen region. The specific activity of natural radionuclides (K-40, Th-232 and Ra-226) in the profile of gray forest soil of the Nizhnetavdinsky district was established, the specific effective activity of radionuclides in the soil was calculated. Comparative analysis of the obtained results together with the data on administrative districts of the South of the Tyumen region showed that in the soil of the Nizhnetavdinsky district, specific activity of natural radionuclides exceeds the similar indicator typical for the South of the region.

Specific Activity and Radiation Hazard of Radionuclides in Wheat and Bean Produced Near Shazand, Iran

Introduction: Radionuclides found in foods are harmful to human health. Wheat and bean are among the most important food ingredients in the world. Therefore, this study aimed to determine the specific activity of natural radionuclides in wheat and bean produced near the refinery complex plant. Material and Methods: In order to determine the specific activity of radionuclides, the gamma-ray spectrometry method was used employing a high-purity germanium detector with a relative efficiency of 80%. Results: Our findings showed that the specific activity of the 226Ra isotope of radium had the ranges 232Th isotope of thorium was in the range of not detected (ND)-4.09 and ND-3.62 Bq/kg with the mean values of 2.19 and 2.69 Bq/kg for wheat and bean samples, respectively.The specific activity of the 40K isotope of potassium was obtained as 103.19-168.94 and 129.22-568.98 Bq/kg with the mean values of 142.21 and 458.37 Bq/kg for wheat and bean samples, respectively. The annual effective dose for wheat and bean intake was 0.11-0.52 and 0.02-0.18 mSv, respectively. Furthermore, the mean of excess lifetime cancer risk for wheat and bean samples was calculated as 1.06×10-3 and 0.11×10-3, respectively. The latter values are lower than the world average for bean samples. Conclusion: According to the results of this study, the radiological parameters of wheat were higher than the global average and reference value, which may be due to ash dispersion in this area. For bean, these parameters were lower than the mean value. As a result, it could be concluded that bean is not considered as a threat to consumer health.

Вміст радіонуклідів у фітопланктоні на різних ділянках Запорізького водосховища

The radionuclides, which have occurred in the aquatic ecosystem are quickly redistributed there. Most of them come through the water phase to the benthal deposit, while the other part of them accumulates in suspensions and hydrobionts. Even low concentrations of radionuclides in water contributes to its radioactive contamination that poses risks to the environment. The radionuclide contamination of freshwater ecosystems is particularly pressing issue, since water with low mineralization enhances the radionuclides activity in the sediments compared to the water by a factor of 10 or even more, and in the animals by hundreds and thousands of times. Phytoplankton is the fundamental autotrophic link of aquatic ecosystems. Due to a large total sorption surface, it is able to absorb, retain and transmit radionuclides along the food chains, leading to a deterioration of the environmental position of the reservoir. Phytoplankton was sampled in the summer of 2019 at 5 sites along the course of the Zaporizke reservoir, which differ in hydrological and hydrochemical conditions: Samara Bay, Festivalnyi pier, Monastyrsky island, creek of the Mokra Sura river and the lower section of the reservoir (near Viyskove village). The specific radioactivity of phytoplankton samples was determined using generally accepted radiochemical methods and gamma spectrometry. The specific radioactivity of radionuclides is given in bequerels per kilogram (Bq/kg) of fresh, natural weight. Statistical processing of research results was carried out using generally accepted methods of variation statistics for a small sample using the Excel 2010 software package. Purpose of the work. To determine the content of natural ( 232 Th, 226 Ra and 40 K) and artificial ( 137 Cs and 90 Sr) radionuclides in phytoplankton at different sites of the Zaporizke reservoir. The content of artificial radionuclides in the phytoplankton of the Zaporizke reservoir averaged as follows: 137 Cs – 7.61±0.501 Bq/kg; 90 Sr – 1.13±0.242 Bq/kg. The maximum values of the content of artificial radionuclides in phytoplankton were recorded in the area of the Festivalnyi pier and the minimum values were recorded near Viyskove village ( 137 Cs) and Samara bay ( 90 Sr). In total, phytoplankton has a relatively low content of artificial radionuclides, which is explained by its low content in water. Hydrobionts receive the main portion of radiation exposure from natural sources of radiation. About 300 natural radionuclides have been identified in the environment; among them 226 Ra, 232 Th and 40 K make a significant contribution to the total natural radioactivity. The specific activity of natural radionuclides in the water area of the Zaporizke reservoir on average was following: 226 Ra – 95.45±7,010 Bq/kg; 232 Th – 85.66±4,013 Bq/kg; 40 K – 185.26±23.74 Bq/kg. The lowest content of natural radionuclides was observed in the phytoplankton of the Samara bay. The maximum recorded specific activity of 226 Ra and 40 K was observed in the creek of the Mokra Sura river, which may indicate an increased content of radionuclides in the water of this river, because the river is polluted throughout its length by industrial, agricultural and municipal wastewater. It has been found that the specific activity of natural radionuclides 226 Ra, 232 Th and 40 K was 80-320 times higher than that of the artificial ones ( 90 Sr and 137 Cs). The distribution of radionuclides in the elements of the freshwater ecosystem is characterized by accumulation coefficients. According to the accumulation coefficients with respect to water, the sequence of accumulation of radionuclides in the phytoplankton of the Zaporizke reservoir has been arranged in descending order: 137 Cs> 232 Th> 226 Ra> 40 K> 90 Sr. The accumulation coefficients of 40 K and 90 Sr are 11-22 times less than those of 137 Cs and 232 Th, which is quite appropriately, because freshwater algae are more able to accumulate 137 Cs. For most of the radionuclides studied, the maximum values of accumulation coefficients have been recorded in phytoplankton in the area of the Festivalnyi pier ( 137 Cs, 90 Sr, 232 Th) and the creek of the Mokra Sura river ( 226 Ra, 40 K). The latter is associated with both the hydrochemical and hydrological conditions of these sites, and with increased anthropogenic impact, especially in the area of the river creek. The data obtained indicate that there is a potential threat of accumulation of radionuclides in phytoplankton and their transfer further along food chains. With reference to the above mentioned, it is important to monitor the content of radionuclides in phytoplankton in order to minimize their transmission through the food chain and preserve the biodiversity of aquatic ecosystems.