Concentration of caesium-137, cobalt-60 and potassium-40 in some wild and edible plants around the nuclear power plant in Bulgaria

Artificial radionuclides in the plant cover around nuclear fuel cycle facilities

This paper presents research on the assessment of the radioecological state of plant cover surrounding two research reactor facilities located within the Semipalatinsk Test Site (STS) as examples of nuclear fuel cycle facilities (NFC). Source data on the concentrations of artificial radionuclides in the plant cover were obtained. Quantitative values for 137Cs, 241Am, and 239+240Pu activity concentrations were determined in plants across the perimeters of the facilities, indicating that these compounds may be present in the associated media from the perspective of accumulative bioindication. The values determined for artificial radionuclides in the 'soil‒plant' system around the researched NFC facilities were attributed to radioactive contamination of the STS territory.

Aggregated transfer factors of fresh Cs and Sr pollution to various vegetables from six common European soils - mesocosm experiment

Aggregated transfer factors (Tag) were identified for three common vegetables grown in six common European soils freshly contaminated by 134Cs and 85Sr. The experiment was carried out as a mesocosm experiment in pots with an average soil weight of 15.8 kg per pot. The vegetables were grown one after the other during one vegetation season, in the order lettuce, onion, and radish (the order usually applied in private gardens and small farms). Despite the fact that lettuce was grown in the most contaminated soil, it had the lowest Tag (in m2/kg) of both radionuclides (3.6E-4 for Cs, 2.0E-2 for Sr), while onion had 6.4E-3 for Cs and 3.2E-2 for Sr and radish had 1.9E-3 for Cs and 8.1E-2 for Sr. Potassium supply did not show any statistically significant effect on Cs Tag; there was a significant impact of K on the decrease in Sr Tag. The experiments indicated that Tag is more affected by plant species than by soil type; therefore, selection of plants with a lower capacity to uptake radionuclides may be an important measure to reduce food contamination and thus minimize the committed effective dose.

Influence of operation of thermal and fast reactors of the Beloyarsk NPP on the radioecological situation in river ecosystems

The results of long-term radioecological monitoring of seven rivers in the 15-km zone of influence of the Beloyarsk Nuclear Power Plant have been presented. A comparative analysis of the content of a wide range of natural and artificial radionuclides in the main components of river ecosystems: surface waters, bottom sediments, floodplain soils, macrophytes and ichthyofauna has been made. The influence of waste technological waters of thermal (AMB-100 and AMB-200) and fast (BN-600 and BN-800) reactors of the Beloyarsk NPP on the content of radiologically significant isotopes in the water and bottom sediments of the Pyshma and Olkhovka rivers has been evaluated. It has been studied that the transition from thermal to fast reactors contributed to a significant decrease in the intake of artificial radionuclides into the rivers of the area where the Beloyarsk NPP is located. So, in the water of the Olkhovka river for the period 1978-2019 the decrease in the specific activity of ¹³⁷Cs was 480, ³H - 36, ⁹⁰Sr - 3.5 times. The maximum discharge of artificial radioisotopes into river ecosystems was noted during the period of recovery work after emergencies at the AMB-100 and AMB-200 reactors. In recent years, the content of artificial radionuclides in water, macrophytes and ichthyofauna of rivers in the zone of influence of the Beloyarsk NPP, except for the Olkhovka, is at the level of the regional background.

Anthropogenic 137Cs on atmospheric aerosols in Bratislava and around nuclear power plants in Slovakia

Nuclear power plants (NPPs) have been one of the sources of anthropogenic radionuclides in the environment. This work combines the results from monitoring stations around NPPs in Slovakia (Mochovce and Jaslovské Bohunice) and academic measurements at the Comenius University campus in Bratislava. Most of the atmospheric ¹³⁷Cs in this region come from the resuspension of the Chernobyl-derived ¹³⁷Cs, as well as caesium produced during nuclear weapons testing. By comparison of the obtained results at NPPs with Bratislava data, radiation impacts of the NPPs on the local environments have been estimated to be negligible.

Evaluation of internal dose to members of the public at the Kaiga site, India, due to the ingestion of primordial radionuclide 40K

Four 220 MWe pressurised heavy water reactors are under operation at Kaiga in the state of Karnataka in India. Environmental radiological survey of the surrounding areas of the Kaiga site is carried out by Bhabha Atomic Research Centre, Mumbai. The estimated dose to the members of the public due to ingestion of radioactive isotope of potassium, a natural radionuclide, in the surroundings of the Kaiga site is 136 μSv (13.6 mrem) per year. The value indicates that the dose to the public due to operation of the nuclear reactors in Kaiga is insignificant in comparison with the dose due to unavoidable natural radioactivity.

Leaves of higher plants as biomonitors of radionuclides (137Cs, 40K, 210Pb and 7Be) in urban air

Leaves of linden (Tilia tomentosa L. and Tilia cordata Mill.) and horse chestnut (Aesculus hippocastanum L.) were analysed as biomonitors of radionuclides in urban air. Samples of soils, leaves and aerosols were collected in Belgrade, Serbia. Activities of (137)Cs, (40)K, (210)Pb and (7)Be in the samples were measured on an HPGe detector by standard gamma spectrometry. "Soil-to-leaves" transfer factors were calculated. Student's t test and linear Pearson correlation coefficients were used for statistical analysis. Differences in local conditions at the sampling sites were not significant, and the mechanisms of the radionuclides' accumulation in both plant species are similar. Ceasium-137 was detected in some of the leaf samples only. Transfer factors for (137)Cs and (40)K were (0.03-0.08) and 1.3, respectively. The concentrations of (210)Pb and (7)Be in leaves were higher in autumn than in spring, and there were some similarities in their seasonal patterns in leaves and in air. Weak to medium correlation was obtained for the (210)Pb and (7)Be activities in leaves and aerosols. Large positive correlation was obtained for the (210)Pb activities in linden leaves and the mean activity in aerosols for the preceding months. Different primary modes of radionuclides accumulation in leaves were observed. Since large positive correlation was obtained for the (210)Pb activity in linden leaves and the mean in aerosols for the preceding months, mature linden leaves could be used as biomonitors of recent (210)Pb activity in air.

Measurement limits to 134Cs concentration in soil

We investigate the caesium concentrations in soils in mountain areas near Gori nuclear power plant in Korea, focusing on the measurement limits to the (134)Cs. In order to lower the minimum detectable amount (MDA) of activity for the (134)Cs, we have used the ammonium molybdophosphate (AMP) precipitation method to get rid of the (40)K existing in natural radioactivity, which reduces the MDA activity about 10 times smaller than those without the AMP precipitation method. The MDA results for the (134)Cs were found to be in the range between 0.015 and 0.044 Bq/kg-dry weight. In order to diminish the background, we also have measured a part of the soil samples in Yangyang, a small town in the east coast of Korea. However, it turns out that in order to detect the (134)Cs in the samples the MDA should be reduced to the level of mBq/kg-dry weight.

Cesium-137 contamination of oak (Quercus petrae Liebl.) from sub-mediterranean zone in South Bulgaria

This study focuses on the cesium-137 ((137)Cs) contamination in grass and in different compartments of oak trees growing in ecosystems, located in the zone with sub-mediterranean climate in South Bulgaria, characterized with high summer temperatures, low precipitation and often periods of drought. In 2008, three experimental sites - PP1, PP2, PP3 - were sampled in oak ecosystems from Maleshevska Mountain at 900 m above sea level. Samples from grass species and oak tree leaves, branches with different diameter, wood disks and bark were analyzed for (137)Cs activity with gamma-spectrometry. The soil-to-plant transfer factor (TF) values for (137)Cs were estimated differentiating different tree compartments. Our findings showed relatively high activity concentrations of (137)Cs in oak trees even 22 years after the Chernobyl accident. The grass under oak was less contaminated compared with the oak trees. The different organs of oak trees could be distinguished according to the (137)Cs contamination as follows: bark>branches (d<1 cm)>leaves>branches (d>3 cm)>wood. The relatively higher contamination of bark compared with the new-formed biomass suggested that a significant part of (137)Cs was accumulated as a result of direct adsorption at the time of the main contamination event. The TF values obtained and the presence of (137)Cs in the branches, leaves and in the wood formed after 1986 confirmed that 22 years after the contamination, the main mechanism of (137)Cs entrance in tree biomass was the root uptake.

Cobalt and secondary poisoning in the terrestrial food chain: data review and research gaps to support risk assessment

Cobalt is a naturally occurring element found in rocks, soil, water, plants, and animals and has diverse industrial importance. It is cycled in surface environments through many natural processes (e.g. volcanic eruptions, weathering) and can be introduced through numerous anthropogenic activities (e.g. burning of coal or oil, or the production of cobalt alloys). The environmental behaviour of cobalt in terrestrial environment is relatively poorly studied and in particular where Co is used in industrial processes, the baseline information to support wider and long-term environmental impacts is widely dispersed. To support the adoption of new EU regulations on the risk assessment of chemicals, we review here the various aspects of the environmental chemistry, fate and transport of Co across environmental interfaces and discuss the toxicology and potential for bio magnification and food chain accumulation. The soil-to-plant transfer of Co appears to be viable route to expose lower trophic levels to biologically significant concentrations and Co is potentially accumulated in biomass and top soil. Evidence for further accumulation through soil-invertebrate transfer and to higher trophic levels is suggested by some studies but this is obscured by the relatively high variability of published transfer data. This variation is not due to one particular aspect of the transfer of Co in terrestrial environments. Influences are from the variability of geological sources within soil systems; the sensitivity of Co mobility to environmental factors (e.g. pH) and the variety of life strategies for metal elimination/use within biological species. Toxic effects of Co have been suggested for some soil-plant animal studies however, uncertainty in the extrapolation from laboratory to field is a major limitation.

Distribution of gamma-ray emitting radionuclides in the environment of Burullus Lake: I. Soils and vegetations

The concentrations and distribution of gamma-ray emitting isotopes in Burullus Lake were investigated with the aim of evaluating the environmental radioactivity. Particularly in wetlands, natural properties of the environment can cause the actual inventory to be different from the activity originally deposited. The mean concentrations of (226)Ra, (232)Th and (40)K were 14.3, 15.5 and 224 Bq/kg, respectively, in the coastal soils. On the other hand, soil samples from the islands had mean concentrations of 13.5, 17.4 and 341 Bq/kg for (226)Ra, (232)Th and (40)K, respectively. Samples from coast and islands show evidence of possible transfer and accumulation of the (137)Cs radionuclide. The mean (137)Cs activity concentrations in the soil samples were 1.2 and 15.1 Bq/kg in the coast and islands, respectively. The vertical migration of (137)Cs was studied based on its content in the consequently located three soil layers down to 30 cm depth. The radium equivalent, dose rate in air and annual dose equivalent from the terrestrial natural gamma-radiation were evaluated. The mean activity concentrations of the gamma-ray emitting radionuclides in vegetation were relatively low.