Spatial radionuclide deposition data from the 60 km radial area around the Chernobyl nuclear power plant: results from a sampling survey in 1987

The data set “Spatial radionuclide deposition data from the 60 radial km area around the Chernobyl nuclear power plant: results from a sampling survey in 1987” is the latest in a series of data to be published by the Environmental Information Data Centre (EIDC) describing samples collected and analysed following the Chernobyl Nuclear Power Plant accident in 1986. The data result from a survey carried out by the Ukrainian Institute of Agricultural Radiology (UIAR) in April and May 1987 and includes sample site information, dose rate, radionuclide (zirconium-95, niobium-95, ruthenium-106, caesium-134, caesium-137 and cerium-144) deposition, and exchangeable (determined following 1M NH4Ac extraction of soils) caesium-134 and 137. The purpose of this paper is to describe the available data and methodology used for sample collection, sample preparation and analysis. The data will be useful in reconstructing doses to human and wildlife populations, answering the current lack of scientific consensus on the effects of radiation on wildlife in the Chernobyl Exclusion Zone and evaluating future management options for the Chernobyl-impacted areas of Ukraine and Belarus. The data and supporting documentation are freely available from the EIDC under the terms and conditions of the Open Government Licence (Kashparov et al., 2019; https://doi.org/10.5285/a408ac9d-763e-4f4c-ba72-73bc2d1f596d)

A New Route for Preparation of Hydrophobic Silica Nanoparticles Using a Mixture of Poly(dimethylsiloxane) and Diethyl Carbonate

Organosilicon layers chemically anchored on silica surfaces show high carbon content, good thermal and chemical stability and find numerous applications as fillers in polymer systems, thickeners in dispersing media, and as the stationary phases and carriers in chromatography. Methyl-terminated poly(dimethylsiloxanes) (PDMSs) are typically considered to be inert and not suitable for surface modification because of the absence of readily hydrolyzable groups. Therefore, in this paper, we report a new approach for surface modification of silica (SiO2) nanoparticles with poly(dimethylsiloxanes) with different lengths of polymer chains (PDMS-20, PDMS-50, PDMS-100) in the presence of diethyl carbonate (DEC) as initiator of siloxane bond splitting. Infrared spectroscopy (IR), elemental analysis (CHN), transmission electron microscopy (TEM), atomic force microscopy (AFM), rotational viscosity and contact angle of wetting were employed for the characterization of the raw fumed silica and modified silica nanoparticles. Elemental analysis data revealed that the carbon content in the grafted layer is higher than 8 wt % for all modified silicas, but it decreases significantly after sample treatment in polar media for silicas which were modified using neat PDMS. The IR spectroscopy data indicated full involvement of free silanol groups in the chemisorption process at a relatively low temperature (220 °C) for all resulting samples. The contact angle studies confirmed hydrophobic surface properties of the obtained materials. The rheology results illustrated that fumed silica modified with mixtures of PDMS-x/DEC exhibited thixotropic behavior in industrial oil (I-40A), and exhibited a fully reversible nanostructure and shorter structure recovery time than nanosilicas modified with neat PDMS. The obtained results from AFM and TEM analysis revealed that the modification of fumed silica with mixtures of PDMS-20/DEC allows obtaining narrow particle size distribution with uniform dispersity and an average particle size of 15–17 nm. The fumed silica nanoparticles chemically modified with mixtures of PDMS-x/DEC have potential applications such as nanofillers of various polymeric systems, thickeners in dispersing media, and additives in coatings

Cleavage of Organosiloxanes with Dimethyl Carbonate: A Mild Approach To Graft-to-Surface Modification

In this work, we explore the depolymerization of poly­(dimethylsiloxane) (PDMS-100) and poly­(methylphenylsiloxane) (PMPS) using dimethyl carbonate (DMC) and develop a surface functionalization method by utilizing the DMC-imparted active methoxy end groups of the partially depolymerized polysiloxanes. The efficiency of dimethyl carbonate as a reagent for organosiloxane cleavage was confirmed by means of ¹H NMR spectroscopy, size-exclusion chromatography, and viscosity measurements. The reaction of fumed silica with organosiloxanes (PMPS, PDMS-50) in the presence of DMC was investigated using the ζ-potential, ²⁹Si and ¹³C solid-state NMR spectroscopy, IR spectroscopy, CHN analysis, contact angle goniometry, thermogravimetric analysis, scanning and transmission electron microscopy (TEM), and rheology. It was found that the interaction of PMPS/DMC with an SiO₂ surface produced hydrophobic and thermally stable moieties (up to 550 °C) with a densely packed (average 2.2 groups/nm²) alkylsiloxane network for SiO₂/PMPS + DMC in comparison with SiO₂/PMPS (average 1.4 groups/nm²). Surface functionalization was successfully attained at a relatively moderate temperature of 200 °C. Scanning electron microscopy data show that the average size of aggregates of PMPS/DMC-modified silica nanoparticles is smaller than that of the initial silica and silica modified with neat PMPS. TEM images reveal uniform distribution of the PMPS/DMC mixture across the SiO₂ surface. Rheology studies show thixotropic behavior in industrial oil (I-40A), a fully reversible nanostructure and shorter structure recovery time for fumed silica modified in the presence of DMC

Application of a tuning-free burned area detection algorithm to the Chornobyl wildfires in 2022

Abstract The wildfires in the Chornobyl Exclusion Zone (ChEZ) have caused widespread public concern about the potential risk of radiation exposure from radionuclides resuspended and redistributed due to the fires in 2020. The wildfires were also confirmed in ChEZ in the spring of 2022, and its impact needed to be estimated accurately and rapidly. In this study, we developed a tuning-free burned area detection algorithm (TuFda) to perform rapid detection of burned areas for the purpose of immediate post-fire assessment. We applied TuFda to detect burned areas in the ChEZ during the spring of 2022. The size of the burned areas in February and March was estimated as 0.4 km2 and 70 km2, respectively. We also applied the algorithm to other areas outside the boundaries of the ChEZ and detected land surface changes totaling 553 km2 in northern Ukraine between February and March 2022. These changes may have occurred as a result of the Russian invasion. This study is the first to identify areas in northern Ukraine impacted by both wildfires and the Russian invasion of Ukraine in 2022. Our algorithm facilitates the rapid provision of accurate information on significant land surface changes whether caused by wildfires, military action, or any other factor

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

publishedVersio

Modelling of the Fate of ¹³⁷Cs and ⁹⁰Sr in the Chornobyl Nuclear Power Plant Cooling Pond before and after the Water Level Drawdown

During the accident in April 1986, the Cooling Pond (CP) of the Chornobyl Nuclear Power Plant (ChNPP) was heavily contaminated by fuel particles and radionuclides of cesium-137 (137Cs) and strontium-90 (90Sr). Starting from the end of 2014, a gradual decrease of the CP water level began leading to the transformation of the whole reservoir into eight separate sectors and raising the concern of the fate of 137Cs and 90Sr in the future. In this study, two mathematical models were applied to reproduce radioactive contamination of the CP from 1986 to 2021 and to provide a forecast of 137Cs and 90Sr concentrations in the CP water from 2022 to 2030. The hydrodynamic model THREETOX provided three-dimensional (3D) currents in the CP corresponding to hydrological conditions before and after water level drawdown, and these currents were used in the box model POSEIDON-F for the long-term simulations of the changes in 137Cs and 90Sr concentrations in water, bottom sediments, and biota. Seasonal changes in the distribution coefficient (Kd) describing the partition of 137Cs between water and sediments were considered in the box model, which allowed us to reproduce the observed variations of concentration. Calculated concentrations of 137Cs and 90Sr in water and freshwater fish occupying different trophic levels agreed well with measurements for the entire post-accident period. After the water level drawdown, concentrations of 137Cs in the CP water slightly increased in all eight sectors, while 90Sr concentrations significantly increased in sectors close to ChNPP, which was explained by an additional 90Sr source when comparing the simulation results and measurement data. Using the model forecast from 2022 to 2030, we predict that the concentration of both radionuclides will gradually decrease in new water bodies of the Cooling Pond except in the northern sectors, where the suggested additional source of 90Sr will lead to a stabilization of 90Sr concentrations

Biogeochemical recycling of K and Cs isotopes in deciduous forest stands on the long term after deposition

International audienceDue to atmospheric releases from the Chernobyl and Fukushima accidents, Cs-137 long half-live (30y) and its incorporation into the biogeochemical cycle of elements lead to its persistence within forest ecosystems, affecting forest ecosystem services even more since their decontamination is hardly possible. Predicting its behavior and transfer dynamics over time is of key importance to help recovering benefit from forest products. Such assessment studies require the transfer processes to be documented with numerous data to encompass the variability of environmental factors (e.g. species, age, climate, deposit). To date, the root-uptake which is known to be the major process of Cs-137 intake in trees after the transition phase (&gt;10y) couldn’t be robustly assessed due to the remaining contribution of initial foliar uptake. More, data remain scarce for deciduous trees as most post-Chernobyl and post-Fukushima field studies mainly focused on evergreen species.Relying on stands monitoring data collected during the post-accident long-term phase (&gt;30y) in 4 various deciduous forest stands (France, Ukraine), we compared their Cs-137 concentrations and inventories distributions in trees as well as those of stable chemical analogues (Cs-133, K). To differentiate annual root-uptake from internal translocations fluxes in trees, we assessed their biogeochemical cycling fluxes (mass balance approach).On the long-term, the Cs-137 initial foliar uptake contribution was no more visible at our sites due to biomass dilution and Tag (aggregated transfer factor) values were one order of magnitude lower than reference ones (IAEA, 2009) likely indicating a long-term decrease of Cs-137 bioavailability in soil. The concentrations of Cs-133 and Cs-137 normalized by the exchangeable inventories in soil were linearly correlated (r&gt;0.7, p&lt;0.05) and differences between isotopes were explained by the soil depth root density. The Cs isotopes were more sequestered than K in roots. Compared to evergreen coniferous forests, uptake rates (y-1) were up to twice higher for K but up to 10 times lower for Cs isotopes, consequently exhibiting a stronger Cs/K discrimination. In a Q. serrata stand sampled in 2014-2018 (Japan, early-medium stage) where dynamics were slower than for coniferous, use of Cs-133 and K to assess the magnitude of Cs-137 root uptake rate is underway.2 376 / 5 000En raison des rejets atmosphériques des accidents de Tchernobyl et de Fukushima, la longue demi-vie (30 ans) du Cs-137 et son incorporation dans le cycle biogéochimique des éléments conduisent à sa persistance au sein des écosystèmes forestiers, affectant d'autant plus les services écosystémiques forestiers puisque leur décontamination est difficilement possible. . Prédire son comportement et sa dynamique de transfert dans le temps est d’une importance capitale pour aider à récupérer les bénéfices des produits forestiers. De telles études d'évaluation nécessitent que les processus de transfert soient documentés avec de nombreuses données pour englober la variabilité des facteurs environnementaux (par exemple, espèces, âge, climat, gisement). À ce jour, l’absorption racinaire, connue pour être le processus majeur d’absorption du Cs-137 dans les arbres après la phase de transition (&gt; 10 ans), n’a pas pu être évaluée de manière robuste en raison de la contribution restante de l’absorption foliaire initiale. De plus, les données restent rares pour les arbres à feuilles caduques, car la plupart des études de terrain post-Tchernobyl et post-Fukushima se sont principalement concentrées sur les espèces à feuilles persistantes.En nous appuyant sur les données de suivi des peuplements collectées pendant la phase post-accidentelle à long terme (&gt;30 ans) dans 4 peuplements forestiers feuillus différents (France, Ukraine), nous avons comparé leurs concentrations et répartitions des stocks de Cs-137 dans les arbres ainsi que celles des composés chimiques stables. analogues (Cs-133, K). Pour différencier l'absorption racinaire annuelle des flux de translocations internes dans les arbres, nous avons évalué leurs flux de cycles biogéochimiques (approche bilan de masse).À long terme, la contribution initiale de l'absorption foliaire du Cs-137 n'était plus visible sur nos sites en raison de la dilution de la biomasse et les valeurs du Tag (facteur de transfert agrégé) étaient d'un ordre de grandeur inférieures à celles du Cs-137. ceux de référence (AIEA, 2009) indiquant probablement une diminution à long terme de la biodisponibilité du Cs-137 dans le sol. Les concentrations de Cs-133 et de Cs-137 normalisées par les inventaires échangeables dans le sol étaient linéairement corrélées (r&gt;0,7, p&lt;0,05) et les différences entre les isotopes étaient expliquées par la densité des racines en profondeur du sol. Les isotopes Cs étaient plus séquestrés que K dans les racines. Comparés aux forêts de conifères à feuilles persistantes, les taux d'absorption (y-1) étaient jusqu'à deux fois plus élevés pour le K mais jusqu'à 10 fois plus faibles pour les isotopes du Cs, présentant par conséquent une discrimination Cs/K plus forte. Dans un peuplement de Q. serrata échantillonné en 2014-2018 (Japon, stade précoce-moyen) où la dynamique était plus lente que celle des conifères, l'utilisation du Cs-133 et du K pour évaluer l'ampleur du taux d'absorption racinaire du Cs-137 est en cours