Papers by Gennady V Laptev
Nuclear Physics and Atomic Energy, 2015
Results of research showing the possibility of direct measurements of 90 Sr on liquid scintillati... more Results of research showing the possibility of direct measurements of 90 Sr on liquid scintillation spectrometer using registration of the Cherenkov luminescence and radiation in scintillation cocktail on a series of water samples, collected on territory with radioactive contamination after the Chernobyl accident, are shown. Solution for quench correction and accounting on presence within the sample of 137 Cs are also demonstrated. Results have shown good correspondence to that received by classical radiochemical analysis. The best performance in term of quality of registration was shown by the method of measurement with using scintillation cocktail.
Science of The Total Environment, May 1, 2023
Science of The Total Environment
Concentration-discharge relationships are widely used to understand the hydrologic processes cont... more Concentration-discharge relationships are widely used to understand the hydrologic processes controlling river water chemistry. We investigated how hydrological processes affect radionuclide concentrations (137Cs and 90Sr) in surface water in the headwater catchment at the Chornobyl exclusion zone in Ukraine. In flat wetland catchment, the depth of saturated soil layer changed little throughout the year, but changes in saturated soil surface area during snowmelt and immediately after rainfall affected water chemistry by changing the opportunities for contact between suface water and the soil surface. On the other hand, slope catchments with little wetlands, the water chemistry in river water is formed by changes in the contribution of "shallow water" and "deep water" due to changes in the water pathways supplied to the river. Dissolved and suspended 137Cs concentrations did not correlate with discharge rate or competitive cations, but the solid/liquid ratio of 13...
EGU General Assembly Conference Abstracts, Apr 1, 2019
EGU General Assembly Conference Abstracts, Apr 1, 2019
<p>Most of the territory of the Chernobyl Exclusion Zone (CEZ) is covered b... more <p>Most of the territory of the Chernobyl Exclusion Zone (CEZ) is covered by forest. Forest of CEZ have accumulated a significant part of the radioactive release and for many years have served as a barrier to the non spreading of the radionuclide contamination outside the CEZ.</p><p>According to the classification of wildfire danger, the forests of CEZ belong to high, above average and medium classes, making cases of wildfires as quite common.</p><p>Poor, sod-podzolic soils of Ukrainian Polesye contribute to the entry the activity of <sup>90</sup>Sr and <sup>137</sup>Cs in plant biomass. During wildfires some of the radionuclides contained in combustion products of biomass are emitted into the atmosphere. Biologically important radionuclides such as <sup>90</sup>Sr, <sup>137</sup>Cs, plutonium isotopes and <sup>241</sup>Am bound to fine aerosols - combustion products - can be transported with atmospheric flows over the long range, causing secondary radioactive fallout and forming additional inhalation dose loads on the population.</p><p>Lack of the actual information on the source term (rate of emission of radionuclides) does not allow reliable modeling of the radiological impact of wildfires. To address this issue, we have proposed a methodology that allows for operational assessments of the dynamics of radionuclide emissions into the atmosphere from wildfires in the CEZ.</p><p>The basic parameters for the calculations are</p><ul><li>cartographic data on the density of radionuclide contamination of the territory of the CEZ;</li> <li>classification of the territory of the CEZ according to the distributive features of forests and meadows;</li> <li>classification of CEZ forests according to taxa characteristics to estimate amount of stored fuel biomass (kg/m<sup>2</sup>);</li> <li>experimental data on the transfer of radionuclides from soil to the main components of biomass for the calculation of radionuclide inventory in fuel biomass (Bq/m<sup>2</sup>). Thus, for meadows the main fuel component is grass turf, while for forest these are litter, wood, bark and pine needles.</li> <li>experimental data on emission factors of radionuclides from fuel biomass.</li> </ul><p>Implementation of the proposed algorithm in the form of GIS application makes it possible to assess the dynamics of radionuclide emission into the atmosphere by delineation the fire areas on the CEZ map. The NASA WorldView interactive mapping web application can be used to estimate the temporal and spatial characteristics of the wildfire while it is being developed. The contouring of the area affected by fire is carried out according to the analysis of the cluster of thermal points. Also, operational contouring of wildfire can be carried out using data delivered from unmanned aerial vehicles.</p><p>The application of the proposed algorithm for the analysis of the dynamics of <sup>137</sup>Cs emissions into the atmosphere from the April 2020 wildfire showed a good agreement with the data reported by various authors who used the method of inverse simulation. Improving the accuracy of calculations according to the proposed algorithm can be done by rectifying radionuclide emission factors and taking into account fire intensity data, which in turn can affect both the radionuclide emission factor and the degree of burnout of plant biomass.</p>
<p>Undisturbed sediment cores have been obtained for the first time... more <p>Undisturbed sediment cores have been obtained for the first time in 2019 from mountain Lake Synevyr located at 989 ASL on the territory of eponymous National Nature Park in the Ukrainian Transcarpathian region. The sediment cores were collected from the northern and southern subbasin of the lake with the maximal depths ~22m verified by the bathymetric survey of the lake bottom.</p><p>Testing the water column physico-chemical profile (ToC, DO, TDS, pH, ORP) allowed to show that the Lake Synevyr has strong vertical  stratification as it was established by apparent thermocline and absence of DO at depth below ca. 10 m. Most likely this stratification occurs permanently whereby the bottom sediment showed quasi-laminated (varved) structure, with clearly distinguished fragments of sediment  accumulated on the bottom of the lake at different episodes of times.</p><p>Other local natural archives under study were small mountain swampy lake Diike, sphagnum oligotrophic swamps Zamshatka and Gluhanya, where samples of the sphagnum moss were collected and subjected for radiometric analysis to establish regional reference atmospheric flux of airborne radionuclides. </p><p>Radiometric dating of collected sediment cores using CRS and CIC models (1) applied to vertical profile of unsupported 210Pb was successfully carried out, allowing to quantify variations in sediment accumulation rate at the bottom of Lake Synevyr over the last 120 years (2).</p><p>To corroborate the validity of the results derived by 210Pb dating 137Cs and 241Am - anthropogenic radionuclides, products of nuclear testing in the atmosphere or due to major nuclear accidents, were used as the time markers. Radiometric chronological dates suggested by the 210Pb models  satisfactorily coincide with the vertical distribution of 137Cs and traces of 241Am, which clearly showed two resolved peaks dated as 1963 (global nuclear weapons tests) and 1986 (Chernobyl accident).</p><p>It has been established that variation of sedimentation rates in Lake Synevyr in general follow the regional atmospheric precipitation time pattern, instrumental records of which are available from 1947 on and show apparent ∼20y cycling oscillation. Most noticeable was presence in the sediment column records of impulse ingression of erosion products from the catchment due to mudflows caused by combination of extreme rainfall and snowmelt dated back to 1998 and 2001 when catastrophic floods devastated the entire Transcarpathia bringing numerous human losses. According to the sediment records these were the only episodes of extensive erosion that happened in the last century.</p><p>Taking into account that Lake Synevyr was formed as a result of massive landslide happened 10 thousand years ago, and located in pristine remote location far away from industrial sites with intensive human activity, one can consider it as a prospectus geochronological archive for studying the past environmental history and ongoing climate change (3).</p><p>1. Appleby P. G.Radiometric dating of sediment records in European mountain lakes. Limnol., 59 (Suppl. 1): 1-14, 2000.</p><p>2. Laptev, G. V., et al..Radiometric dating of bottom deposits of mountain lake Synevyr (Ukrainian Carpathians) by 210Pb. Kiev: INS, 2020 </p><p>3. Laptev G.V. The Black sea SST reconstruction for the past 2000 years using radiometrically dated sediment records from abyssal plain and continental slope. ISIH Monaco, 2011.</p>
<p>Bottom sediments of lakes and dam reservoirs can provide an insight into... more <p>Bottom sediments of lakes and dam reservoirs can provide an insight into understanding the dynamics of <sup>137</sup>Cs strongly bound to sediment particles. On this premise, a number of cores of bottom sediments were collected in deep parts of lakes Glubokoe, Azbuchin, and Cooling Pond in close vicinity of the Chernobyl NPP in Ukraine, in Schekino reservoir (Upa River) in the Tula region of Russia (2018) and in Ogaki reservoir (Ukedo River) in Fukushima contaminated area (2019). Each layer of bottom sediments can be attributed to a certain time of suspended particles sedimentation. With <sup>137</sup>Cs activity concentration in a given layer of bottom sediments corresponding to <sup>137</sup>Cs concentration on suspended matter at that point in time, we were able to reconstruct the post-accidental dynamics of particulate <sup>137</sup>Cs activity concentrations. Using experimental values of the distribution coefficient <em>K<sub>d</sub></em>, changes in the dissolved <sup>137</sup>Cs activity concentrations were estimated. The annual mean particulate and dissolved <sup>137</sup>Cs wash-off ratios were also calculated for the period after the accidents. Interestingly, the particulate <sup>137</sup>Cs wash-off ratios for the Ukedo River at Ogaki dam were found to be similar to those for the Pripyat River at Chernobyl in the same time period after the accident, while the dissolved <sup>137</sup>Cs wash-off ratios in the Ukedo River were an order of magnitude lower than the corresponding values in the Pripyat River. The estimates of particulate and dissolved <sup>137</sup>Cs concentrations in Chernobyl cases were in reasonable agreement with monitoring data and predictions using the semi-empirical diffusional model. However, both the particulate and dissolved <sup>137</sup>Cs activity concentrations and wash-off ratios in the Ukedo River declined faster during the first eight years after the FDNPP accident than predicted by the diffusional model, most likely, due to greater natural attenuation and, to some extent, remediation measures implemented on the catchments in Fukushima.</p><p>This research was supported by Science and Technology Research Partnership for Sustainable Development (SATREPS), Japan Science and Technology Agency (JST)/Japan International Cooperation Agency (JICA) (JPMJSA1603), by bilateral project No. 18-55-50002 of Russian Foundation for Basic Research (RFBR) and Japan Society for the Promotion of Science (JSPS), and JSPS Project KAKENHI (B) 18H03389.</p>
Japan Geoscience Union, 2020
Behavior of Radionuclides in the Environment II, 2020
Environmental Science & Technology, 2021
From early April 2020, wildfires raged in the highly contaminated areas around the Chemobyl nucle... more From early April 2020, wildfires raged in the highly contaminated areas around the Chemobyl nuclear power plant (CNPP), Ukraine. For about four weeks, the fires spread around and into the Chernobyl exclusion zone (CEZ) and came within a few kilometres of both the CNPP and radioactive waste storage facilities. Wildfires occurred on several occasions throughout the month of April. They were extinguished, but weather conditions and the spread of fires by airborne embers and smoldering fires led to new fires starting at different locations of the CEZ. The forest fires were only completely under control at the beginning of May, thanks to the tireless and incessant work of the firefighters and a period of sustained precipitation. In total, 0.7-1.2 TBq 137Cs were released into the atmosphere. Smoke plumes partly spread south and west and contributed to the detection of airborne 137Cs over the Ukrainian territory and as far away as Western Europe. The increase in airborne 137Cs ranged from several hundred pBq-m-3 in northern Ukraine to trace levels of a few pBq-m-3 or even within the usual background level in other European countries. Dispersion modeling determined the plume arrival time and was helpful in the assessment of the possible increase in airborne 137Cs concentrations in Europe. Detections of airborne 90Sr (emission estimate 345-612 GBq) and Pu (up to 75 GBq, mostly 241Pu) were reported from the CEZ. Americium-241 represented only 1.4% of the total source term corresponding to the studied anthropogenic radionuclides but would have contributed up to 80% of the inhalation dose. Synopsis Wildfires in highly radioactive environment can re-emit radionuclides into the atmosphere. Such emissions present a potential health risk for firefighters.
Behavior of Radionuclides in the Environment II, 2020
It has been shown that after the initial phase of the Chernobyl accident, for time periods longer... more It has been shown that after the initial phase of the Chernobyl accident, for time periods longer than 1 year, the changes in activity concentrations of radionuclides, both dissolved and particulate, are determined by changes in the concentrations of the upper soil layer for rivers or top layer of bottom sediments for lakes and ponds. The advantage of the proposed diffusion-based approach to describe the time dependence of radionuclide concentrations in rivers and lakes is that the middle- and long-term phases after the accident can be described by the same equation with the same parameters. Datasets for Chernobyl contaminated rivers and lakes have been used to test the model. The proposed semiempirical diffusional model of radionuclide dynamics in surface waters provides a tool for long-term predictions of river contamination in the future not only for Chernobyl but also for Fukushima contaminated areas or any other nuclear accident.
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Papers by Gennady V Laptev