Spatial datasets of radionuclide contamination in the Ukrainian Chernobyl Exclusion Zone

The dataset “Spatial datasets of radionuclide contamination in the Ukrainian Chernobyl Exclusion Zone” was developed to enable data collected between May 1986 (immediately after Chernobyl) and 2014 by the Ukrainian Institute of Agricultural Radiology (UIAR) after the Chernobyl accident to be made publicly available. The dataset includes results from comprehensive soil sampling across the Chernobyl Exclusion Zone (CEZ). Analyses include radiocaesium (134Cs and 134Cs) 90Sr, 154Eu and soil property data; plutonium isotope activity concentrations in soil (including distribution in the soil profile); analyses of “hot” (or fuel) particles from the CEZ (data from Poland and across Europe are also included); and results of monitoring in the Ivankov district, a region adjacent to the exclusion zone. The purpose of this paper is to describe the available data and methodology used to obtain them. The data will be valuable to those conducting studies within the CEZ in a number of ways, for instance (i) for helping to perform robust exposure estimates to wildlife, (ii) for predicting comparative activity concentrations of different key radionuclides, (iii) for providing a baseline against which future surveys in the CEZ can be compared, (iv) as a source of information on the behaviour of fuel particles (FPs), (v) for performing retrospective dose assessments and (vi) for assessing natural background dose rates in the CEZ. The CEZ has been proposed as a “radioecological observatory” (i.e. a radioactively contaminated site that will provide a focus for long-term, radioecological collaborative international research). Key to the future success of this concept is open access to data for the CEZ. The data presented here are a first step in this process. The data and supporting documentation are freely available from the Environmental Information Data Centre (EIDC) under the terms and conditions of the Open Government Licence: https://doi.org/10.5285/782ec845-2135-4698-8881-b38823e533bf

⁹⁰Sr Content in the Stemwood of Forests Within Ukrainian Polissya

The consequences of the Chernobyl disaster continue to threaten humans and ecosystems across fallout gradient in Northern Ukraine and nearby. Forest ecosystems contain substantial stocks of long-lived radionuclide 90Sr which was leached from the fuel matrix during the disaster. Nowadays, there is a lack of information about current transfer factors (TF) of this radionuclide from soil to the stemwood of native tree species. We have estimated 90Sr content in the forest stemwood of three tree species utilizing models of their growth and yield and collected woody samplings. TFs provided here vary greatly across studied tree species (18.0 × 2.1±1, 8.7 × 2.8±1, and 10.4 × 6.0±1 n×10−3 m2·kg−1 (geometrical mean (GM) ± geometrical standard deviation, GSD) for the above species, respectively) and together with indicators of soil contamination allow us to reliably assess local stocks in the stemwood. Silver birch stands are estimated to deposit the highest 90Sr stocks. Herewith, at 25 years old Black alder stands could accumulate higher stocks (up to 35 MBq·ha−1) under rich growth conditions. TFs obtained in this study substantially exceed values provided by the International Atomic Energy Agency for studied tree species and thus could entail respective restrictions on use of firewood across large areas in Ukrainian Polissya. Data provided here may be harnessed to support decisions of respective stakeholders to provide credibly safe management of the contaminated forest ecosystems

Wildfires in the Chornobyl Exclusion Zone – risks and consequences

Following the 1986 Chornobyl accident an area of approaching 5000 km2 surrounding the nuclear plant was abandoned, creating the Chornobyl Exclusion Zone (CEZ). Whilst this area likely contains the most radioactive terrestrial ecosystem on earth, over the nearly 35 years since the accident the absence of humans and associated activities has resulted in increases in wildlife numbers. Both the Belarussian and Ukrainian components of the CEZ are now designated as nature reserves; together they form one of Europe's largest protected areas and have been described as an iconic example of rewilding. Forests and former agricultural land (now scrub) dominate the CEZ and wildfires are an annual event. In April 2020, the CEZ suffered its most widespread fires to date when >800 km2 of the 2600 km2 Ukrainian portion of the CEZ was burnt. Largescale fires in the CEZ have implications for wildlife, as they do elsewhere, but they also pose additional radioecological and radiological protection questions. We discuss the implications of wildfires in the CEZ, considering effects on wildlife and changes in radionuclide mobility. We also demonstrate that the risk to firefighters and the wider public from the inhalation of radionuclides in smoke resulting from fires in the CEZ is likely to be low. However, further experimental and modelling work to evaluate potential doses to firefighters from inhaled radioactive particles would be valuable, not least for reassurance purposes

THE DYNAMICS OF LITTERFALL, THROUGHFALL AND STEMFLOW IN RADIOACTIVELY CONTAMINATED PINE STANDS

Наведено результати спостережень низхідних потоків речовини та вмісту у них 137Cs для радіоактивно забруднених деревостанів сосни звичайної, у вигляді опаду та дощових вод. Виділено такі компоненти опаду: хвоя, кора, гілки і генеративна частина (шишки, бруньки, насіння та їх частини). Дощові води, що проникають крізь крони дерев, класифіковано на такі групи: стовбурові та кронові. Відбір зразків здійснено рівномірно протягом періоду дослідження. Охарактеризовано помісячну динаміку структури і запасів елементів опаду на основі 2,5 років спостережень (2014-2016 рр.) за сосновим деревостаном. Виявлено закономірності помісячної динаміки та структури компонентів опаду. Наведено дані зміни питомої активності 137Cs та маси в перерахунку на 1 м3для компонентів опаду і дощових вод з 01.10.2015 р. по 05.10.2016 р. На основі отриманих вихідних показників за зазначений період розраховано річні середньозважені показники для досліджуваних елементів низхідного потоку: середньорічна питома активність 137Cs, сумарна маса в абсолютно сухому стані на 1 м2 та загальна активність 137Cs на 1 м2. Попередні дослідження низхідних потоків 90Sr у соснових деревостанах свідчать про значні відмінності порівняно із 137Cs у співвідношеннях питомої активності компонентів дощової води та опаду, що потребує детальнішого дослідження закономірностей динаміки формування опаду і дощових вод на біогеохімічний кругообіг 90Sr у насадженнях сосни звичайної.Представлены результаты наблюдений нисходящих потоков вещества и содержания в них 137Cs для радиоактивно загрязненных древостоев сосны обыкновенной, в виде опада и дождевых вод. Выделены следующие компоненты опада: хвоя, кора, ветви и генеративная часть (шишки, почки, семена и их части). Дождевые воды, которые проникают сквозь кроны деревьев, классифицированы на следующие группы: стволовые и кроновые. Отбор образцов осуществлено равномерно в течение периода исследования. Охарактеризована помесячная динамика структуры и запасов элементов опада на основе 2,5 лет наблюдений (2014-2016 гг.) по сосновым древостоям. Выявлены закономерности помесячной динамики и структуры компонентов опада. Приведены данные изменения удельной активности 137Cs и массы в пересчете на 1 м3 для компонентов опада и дождевых вод с 01.10.2015 г. по 05.10.2016 г. На основе полученных исходных показателей за указанный период рассчитаны годовые средневзвешенные показатели для исследуемых элементов нисходящего потока: среднегодовая удельная активность 137Cs, суммарная масса в абсолютно сухом состоянии на 1 м2 и общая активность 137Cs на 1 м2. Предыдущие исследования нисходящих потоков 90Sr в сосновых древостоях указывают на значительные различия по сравнению с 137Cs в соотношениях удельной активности компонентов дождевой воды и опада, что требует более детального исследования закономерностей динамики формирования опада и дождевых вод на биогеохимический круговорот 90Sr в насаждениях сосны обыкновенной.The authors present the data of the study of the downflow of a matter of small biological cycle in radioactively contaminated forest ecosystems of Scots pine (Pinus sylvestris L.) as a result of the Chornobyl accident. During the accident, a large number of radionuclides came into the surrounding environment. Currently, 90Sr and 137Cs are the most dangerous for forest phytocoenoses, so as they are included in the biogeochemical cycle through the trophic chains. In this research, the downfall of the matter of the tree stand was divided into two groups: solid parts (litterfall) and liquid fraction (rainwater). In turn, the structure of litterfall was classified as follows: needles, bark, branches and generative organs (cones, buds, seeds and their parts). Rainwater is separated as throughfall and stemflow. Using the obtained data from field observations for 2.5 years (2014-2016), we estimated the dynamics of the formation of litterfall components in calendar months. Experimental materials, collected in the interval from 01.10.2015 to 05.10.2016, are also used to represent the regularities of 137Cs activity concentration for downfall components. The analysis of field data confirmed the presence of a maximum values for litterfall formation at the end of the growing season (September-October) due to the drop of the needles from crown. For other components of litterfall, clearly expressed regularities are not revealed. We calculated summary annual parameters for the components of the downfall: the average 137Cs activity concentration, the accumulated weight and the total activity of 137Cs per 1 m2 of the investigated forest area. 137Cs activity concentration in litterfall samples (1287-6310 Bq·kg-1) is much bigger than in rainwater (1.28-11.2 Bg·kg-1). However, due to much larger amounts of throughfall per unit area of the surface of the site, it has a decisive role in the formation of the return of 137Cs from the elements of the pine stand to the soil (42.3 %). Other components of the downfall are characterized by a much lower percentage in the return of 137Cs to the forest soil: needles (25.7 %), generative organs (13.7 %), bark (12.2 %), branches (3.8 %), stemflow (2.2 %). Previous studies of 90Sr in components of downfall show that this radionuclide differs significantly from 137Cs: it is much more accumulated in the dead parts of pine stand and less washed away by rain than 137Cs. Therefore, the experimental data on the main depots and fluxes of 90Sr must be obtained very quickly for adequately predict the radiological condition in the forests of the Chоrnobyl exclusion zone

Assessment of the radiological situation resulted by the accidental release of fuel particles

Physical-and-chemical properties of Chernobyl hot particles (radionuclide and dispersal composition, nuclear fuel burn-up and radionuclides fractionation, composition of particle matrix etc.) including the fuel particles as specific form of Chernobyl radioactive fall-out were studied [1]. Attempt to reconstruct the conditions of the fuel particles (FP) formation during the accident was done [2,3]. Oxidisation of nuclear fuel was shown to be one of the main mechanisms of FP formation during the ChNPP accident [4]. Maps of the near zone of Chernobyl accident contamination with radionuclides contained in deposited fuel particles were built [5]. It was shown that previous assessments of 90Sr and transuranic elements contents in soils of the 30-km zone has been 3-4-times overestimated. Dependencies of the fuel particles dissolution rate on level of FP matrix oxidation and acidity of a medium both for natural conditions, and model media were obtained [6,7]. Prognosis of the plants contamination dynamics along the fuel traces of radioactive fall-outs was done [6,8]. Problems of the secondary radionuclides transfer in natural conditions, due to technogenic action to soil [9] and forest fires [10], as well as a significance of the FP inhalation intake into human body [11,12] are considered. Parameters of metabolism of FP-associated radionuclides in agricultural animals organism were obtained [13]

Assessment of the radiological safety of Pridneprovskiy chemical plant's tailings

Analysis of the influence of the tailings of uranium production from Pridneprovsk chemical plant of agricultural products with heavy natural radionuclides (210Pb, 210Ро, 226Ra, 232Th, 238U) in adjacent areas of agricultural assignment was performed. Additional radiation doze to the population, living in the zone of influence of the tailings was determined