Long term 7Be deposition in Romania Dovlete, C.; Sonoc, S.; Osvath, I. ...
Journal of environmental radioactivity,
December 2021, 2021-12-00, 20211201, Letnik:
240
Journal Article
Recenzirano
This study is based on monthly 7Be deposition data at 29 of the stations of Romania's National Environmental Radioactivity Surveillance Network (NERSN), with different geographical and climatological ...conditions, extending over periods up to 17 years (1979–1995). The 7Be activity in each monthly sample from each station was determined using high-resolution gamma-ray spectrometry performed at the Environmental Radioactivity Laboratory, Bucharest-Afumati.
The annual dynamics of atmospheric deposition of 7Be at each NERSN station showed a strong seasonal trend, very similar to the precipitation regime, with the highest values being observed in spring/summer and the lowest in winter. But the annual 7Be deposition fluxes varied broadly from station to station and year to year, from a minimum of 164 Bq/m2/y (Bechet, 1989) to a maximum of 1388 Bq/m2/y (Baia Mare, 1988). This large space-time variability of deposition was mainly due to the variability of the precipitation regime.
The analysis of experimental data confirms the strong correlation of 7Be deposition data with precipitation, air temperature and the number of sunspots.
Wet and dry deposition data are presented and discussed for four stations where separate dry and wet 7Be deposition measurements were performed.
•Long-term 7Be monthly deposition data from 29 monitoring stations across Romania were analysed in relation with precipitation, temperature and sunspot number.•A strong correlation of 7Be deposition with precipitation and temperature was found.•70% of the average annual deposition of 7Be across the country occurred between April and September.•Mostly the mean ratio of dry/total deposition varied between 13 and 23 %. Near the Black Sea coast this ratio was almost 40 %.
A baseline study on anthropogenic radioactivity in the Namibian marine ecosystem, which is part of the northern Benguela upwelling system, known as one of the most productive ocean areas in the ...world, has been performed. A scientific cruise carried out in 2014 covering inshore and offshore areas, exhibiting different oceanographic features, has provided a basis for better understanding the distributions, ratios and inventories of six anthropogenic radionuclides (90Sr, 137Cs, 238Pu, 239Pu, 240Pu and 241Am) in seawater. Although 3H was also measured, due to extremely low levels, its behaviour was not studied. The main source of 90Sr, 137Cs, 239Pu, 240Pu and 241Am in the samples analysed was proven to be global fallout, a finding further confirmed by 240Pu/239Pu and 90Sr/137Cs ratios. Furthermore, the 238Pu SNAP-9A satellite accident signal was confirmed once again through the determination of the 238Pu/239+240Pu activity ratio. Inshore and offshore samples showed different patterns due to the unique oceanographic features of this upwelling system. The levels of anthropogenic radionuclides, comprehensively assessed for the first time in this region, are comparable with the few existing data and filled a critical gap for the Southern Atlantic Ocean.
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•First dataset of anthropogenic radionuclides in Benguela upwelling system.•Distributions, ratios and inventories of anthropogenic radionuclides studied.•The main source of 90Sr, 137Cs and 239,240Pu is the global fallout and for 238Pu the SNAP-9A satellite accident.•Combination of radioanalytical and mass-spectrometry techniques used for measurements.•Typical behaviour of conservatives and particle reactive radionuclides in the seawater column observed and compared.
A brief overview of the current status on the subject of numerical modelling of radionuclide transport in the marine environment is given: main transport processes occurring in the sea, basic ...approaches to solve such processes numerically, up-to-date trends to deal with water/sediment interactions (in the case of non-conservative radionuclides), and topics in which work is currently in progress (like the integration of biological uptake models within marine transport models). A brief review of models applied to simulate Fukushima Daiichi nuclear power plant releases in the Pacific Ocean after the 2011 accident is also included, since the most recent modelling efforts have been focused in this problem. A discussion of the main sources of uncertainty in models is given, as well as the problems these uncertainties pose in relation to emergency modelling, which is one of the most relevant applications of dispersion models.
•Types of marine transport models presented.•Present trends to describe water/sediment interactions and other processes commented.•Main sources of uncertainties in models described.•Opinion given on the use of emergency models to support decision-making.
The
137
Cs bulk deposition samples measured in samples collected at Cluj-Napoca in 1965–1985 are analysed and compared with published
137
Cs deposition data from New-York, St. Petersburg, Helsinki ...and Bratislava covering partially/totally the period 1955–1985. A total
137
Cs deposition of 4.2 ± 0.9 kBq/m
2
at Cluj-Napoca is estimated for 1955–1985 based on the comparison of available data. The signature of the atmospheric nuclear tests performed in 1977–1980 is presented using the monthly measured bulk depositions of
106
Ru,
125
Sb,
137
Cs and
144
Ce (1978–1982) and
95
Zr,
103
Ru,
141
Ce for the year 1981, following the last atmospheric nuclear test of October 16, 1980.
Numerical modeling was used to provide a new estimate of the amount of 137Cs released directly into the ocean from the Fukushima Daiichi nuclear power plant (NPP) after the accident in March 2011 and ...to gain insights into the physical processes that led to its dispersion in the marine environment during the months following the accident. An inverse method was used to determine the time‐dependent137Cs input responsible for the concentrations observed at the NPP's two liquid discharge outlets. The method was then validated through comparisons of the simulated concentrations with concentrations measured in seawater at different points in the neighborhood of the plant. An underestimation was noticed for stations located 30 km offshore. The resulting bias in the release inventory was estimated. Finally, the maximum 137Cs activity released directly to the ocean was estimated to lie between 5.1 and 5.5 PBq (Peta Becquerel = 1015 Bq) but uncertainties remain on the amount of radionuclides released during the first few days after the accident. This estimate was compared to previous ones and differences were analyzed further. The temporal and spatial variations of the 137Cs concentration present in the coastal waters were shown to be strongly related to the wind intensity and direction. During the first month after the accident, winds blowing toward the south confined the radionuclides directly released into the ocean to a narrow coastal band. Afterwards, frequent northward wind events increased the dispersion over the whole continental shelf, leading to strongly reduced concentrations.
Key Points
Assessment of cesium‐137 released from Fukushima power plant
Dispersion of radionuclides induced by winds
Certified reference material (CRM) for natural (40K,210Pb,210Po,226Ra,228Ra,228Th,230Th,232Th,234U,235U, and238U) and anthropogenic (137Cs,239+240Pu, and241Am) radionuclides in marine sediment from ...the Baltic Sea (IAEA-465) has been developed. Information values are given for 238Pu,239Pu and240Pu. Altogether 27 laboratories participated in this exercise. Radiometric (alpha-spectrometry, gamma-spectrometry and beta counting, as well as mass spectrometry (ICP-MS and AMS) techniques were applied in measurements. The CRM is intended to be used for Quality Assurance/Quality Control of radionuclide analyses, for the development and validation of analytical methods, for the development of reference methods and for training purposes.
•IAEA-465 Certified Reference Material.•Radionuclides in Baltic Sea Sediment.•Radiometric techniques and mass spectrometry.•Quality Assurance, Quality Control purposes.•Development and validation of reference methods.
State-of-the art dispersion models were applied to simulate 137Cs dispersion from Chernobyl nuclear power plant disaster fallout in the Baltic Sea and from Fukushima Daiichi nuclear plant releases in ...the Pacific Ocean after the 2011 tsunami. Models were of different nature, from box to full three-dimensional models, and included water/sediment interactions. Agreement between models was very good in the Baltic. In the case of Fukushima, results from models could be considered to be in acceptable agreement only after a model harmonization process consisting of using exactly the same forcing (water circulation and parameters) in all models. It was found that the dynamics of the considered system (magnitude and variability of currents) was essential in obtaining a good agreement between models. The difficulties in developing operative models for decision-making support in these dynamic environments were highlighted. Three stages which should be considered after an emergency, each of them requiring specific modelling approaches, have been defined. They are the emergency, the post-emergency and the long-term phases.
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•Models applied to simulate 137Cs marine dispersion after nuclear accidents.•Not good agreement initially found in highly dynamic environments.•Difficulties in developing models for decision making after emergencies highlighted.
In February 2004, anthropogenic radionuclides (137Cs, 236U, 239Pu and 240Pu), transported from the Sahara Desert, were observed in the Monaco air, and later in water and sediment samples collected at ...the DYFAMED site in the northwest (NW) Mediterranean Sea. While 236U and 137Cs in Saharan dust particles showed a high solubility in seawater, Pu isotopes were particle reactive in the water column and in the sediment. The impact of the Saharan deposition was found at 0–1.0 cm of the sediment core for 236U and 137Cs, and between 1.0 and 1.5 cm for Pu isotopes. The excess of 236U was observed more in the water column than in the sediment, whereas the 239+240Pu total inventories were comparable in the water column and the sediment. This single-day particle event represented 72% of annual atmospheric deposition in Monaco. At the DYFAMED site, it accounted for 10% (137Cs) and 15% (239+240Pu) activities of sinking particles during the period of the highest mass flux collected at the 200 and 1000 m water depths, and for a significant proportion of the total annual atmospheric input to the NW Mediterranean Sea (28–37% for 137Cs and 34–45% for 239+240Pu). Contributions to the total 137Cs and 239+240Pu sediment inventories were estimated to be 14% and 8%, respectively. The Saharan dust deposition phenomenon (atmospheric input, water column and sediment) offered a unique case to study origin and accumulation rates of radionuclides in the NW Mediterranean Sea.
•Impact of Saharan dust events on radionuclide levels.•Gamma-spectrometry and Accelerator Mass Spectrometry.•Radionuclides in the NW Mediterranean Sea.•Sediment core DYFAMED station.•137Cs, 236U, Pu isotopes budget estimation.
Four radionuclide dispersion models have been applied to simulate the transport and distribution of 137Cs fallout from Chernobyl accident in the Baltic Sea. Models correspond to two categories: box ...models and hydrodynamic models which solve water circulation and then an advection/diffusion equation. In all cases, interactions of dissolved radionuclides with suspended matter and bed sediments are included. Model results have been compared with extensive field data obtained from HELCOM database. Inventories in the water column and seabed, as well as 137Cs concentrations along 5 years in water and sediments of several sub-basins of the Baltic, have been used for model comparisons. Values predicted by the models for the target magnitudes are very similar and close to experimental values. Results suggest that some processes are not very relevant for radionuclide transport within the Baltic Sea, for instance the roles of the ice cover and, surprisingly, water stratification. Also, results confirm previous findings concerning multi-model applications.
•Box and hydrodynamic models applied to Chernobyl 137Cs dispersion in the Baltic Sea.•Calculated concentrations in water and sediments compared with HELCOM database measurements.•Good agreement found between models and measurements.•Some processes surprisingly not relevant for radionuclide transport (stratification, ice).•Previous findings on multi-model applications have been confirmed.
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