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Radionuclide Migration in Polluted Areas

#2786


Quantitative Assessment of Soil Particles-Bound Radionuclides Redistribution in Landscapes and Prediction of Their Environmental Behaviour (the Case Study in the Chernobyl Caesium Hotspot, Plavsk, Tula Region, Russia)

Tech Area / Field

  • ENV-RED/Remediation and Decontamination/Environment
  • ENV-WPC/Water Pollution and Control/Environment
  • OBS-NAT/Natural Resources and Earth Sciences/Other Basic Sciences

Status
3 Approved without Funding

Registration date
09.06.2003

Leading Institute
Scientific & Production Association “Typhoon”, Russia, Kaluga reg., Obninsk

Supporting institutes

  • FEI (IPPE), Russia, Kaluga reg., Obninsk\nMoscow State University / Department of Geography, Russia, Moscow

Collaborators

  • International Institute for Applied System Analysis (IIASA), Austria, Laxenburg\nCNRS / Laboratoire des Sciences du Climat et de l'Environnement, France, Gif-sur-Yvette Cedex\nUniversity of Exeter, UK, Exeter

Project summary

Objective of the proposed project

Studying and forecasting of the effects of man-made radioactive isotopes on the environment is one of the most important contemporary ecological issues. This has become especially important after the Chernobyl accident, which resulted in the pollution of large areas with long-lived radionuclides, primarily caesium-137 (137Cs). After redistribution in the atmosphere, radioactive 137Cs fallout reaches the Earth surface mainly in association with precipitation. At the surface it is rapidly and strongly absorbed by soil particles, primarily in the clay and silt fractions. Its subsequent landscape redistribution is therefore controlled by the movement of those particles. In anthropogenically transformed landscapes of the temperate zone dominated by fluvial processes, movements of soil particles are mostly associated with soil erosion by water. Hence, the knowledge of spatial and temporal patterns of soil erosion and deposition by water can help to assess the behaviour and transformation of the initial radioactive pollution within landscapes.

The proposed project aims to develop methods for the quantitative evaluation and forecast of radionuclide redistribution within catchments, transportation and re-deposition in rivers and delivery to natural and artificial water systems.

Current research in the study field

The Plava River basin was polluted by 137Cs as a result of atmospheric fallout of radioactive products of the Chernobyl accident. The delivery of this radionuclide into river water depends on the surface runoff erosion of the polluted catchment and the desorbtion from polluted channel and floodplain sediments. Every specific hydrological period (e.g. intensive snowmelt) is dominated by one of these processes. A reliable prediction of the radioactive pollution of river water would obviously require field investigations of all associated processes and their interaction at a polluted catchment area (experimental site) during typical periods of the hydrological cycle.

The Plava river basin could be an excellent experimental site for the proposed project because the Middle Plava River intersects the so-called “Plavsk caesium hotspot”. This could provide an opportunity to study the concentration of radioactive pollutants in water from the “clear” upper reach and through the radioactive pollution zone to the end of the hotspot area. The 137Cs pollution of the Plava River has been studied by the Roshydromet in the city of Plavsk since 1987. However, unlike that conventional monitoring, the proposed detailed investigations would contribute to the methodological improvement of the control of surface water radioactive pollution and provide parameters necessary for physical-based quantitative modelling of radioactive 137Cs migration in river water.

The initial pattern of the radioactive pollution has been substantially transformed in 16 years since the Chernobyl accident. This timespan is sufficient to evaluate the major trends and the transformation rates. Numerous investigations published to date mostly describe these aspects of the problem within some particular components of the geosystem (soils, water, etc.). Therefore an overall analysis of the entire landscape is required to improve the theoretical understanding of contemporary geomorphic processes as well as to resolve practical issues.

Impact of the proposed project on the progress in the study field

The aim project is to:

- identify all pathways of the radionuclide migration from cultivated interfluves to dry valley (balka) bottoms and further to river systems and their transport and re-deposition in water (including the distance of migration in a river system);

- quantitatively evaluate these processes and develop a modeling system supported by a database of fluvial geomorphic processes and radioactive pollution magnitude.

This is an important task because the radionuclide pollution of the environment is the result of atmospheric tests of nuclear weapons as well as non-military accidents. Further research in this field would help to enhance the understanding of modern surface processes and to develop some specific practical applications to evaluate radionuclide pollutant input to inpidual water bodies or landscape areas as well as to forecast the behaviour of radionuclide pollutants in the environment.

Competence of the project team

SPA "Typhoon"

SPA “Typhoon” is the leading Russian organization in the field of environmental radiation monitoring. Its scientists and specialists took part in the investigations of effects of nuclear weapon tests on the environment, radioecological results of radioactive accidents including PO “Mayak” and the Chernobyl atomic powerplant, radioactive pollution of the Techa and Enisey Rivers, radioactive waste dumping near the Novaya Zemlya archipelago, detailed monitoring of Chernobyl radioisotope migration within the Iput river basin; development and validation of ecological-geophysical models of radionuclide migration and redistribution at different landscape environments. They have significant experience of the collaboration on international projects supported by the ISTC (N 85, N 1404/99), the IAEA (VAMP, BIOMOVS, BIOMASS) and the EU (ARCTICMAR, EPIC).

Faculty of Geography of MSU

The Faculty of Geography of the Moscow State University has extensive experience in the research of processes of erosion and accumulation at cultivated catchments in various regions of the Russian Plain (the Voronezh, Saratov, Tambov, Kaluga, Tula Regions), the Caucasian Piedmont (the Stavropol Region) and the Southern Urals (the Orenburg Region). Studies of soil redistribution by water using 137Cs as a tracer have being carried out since 1986. Direct investigations of the spatial redistribution of this radioisotope in landscapes in association with soil erosion were initiated in 1991 with particular attention to areas with high levels of radioactive pollution such as the Plavsk hotspot. Data on the 137Cs redistribution in channel sediments were used for the pollution assessment at the Rein, Danube and Volga River deltas. Scientists from the Faculty of Geography of Lomonosov MSU took part in international projects supported by the IAEA (contract N 9044).

SSC RF-IPPE

The State Scientific Center of Russian Federation - Institute of Physics and Power Engineering (SSC RF-IPPE) is the leading research institute of the Russian Ministry of Atomic Energy (Minatom) in the fields of nuclear device design , strategies for the sustainable development of nuclear energy and economic and ecological aspects of nuclear technologies. SSC RF-IPPE substantial scientific potential provides solutions for significant scientific and technological problems in a number of fields including the non-military use of weapon radioactive materials, the development of advanced radiation technologies, nuclear power safety, nuclear risks analysis, the development of methods and software for computer modeling of the migration of radioactive matter in water. SSC RF-IPPE specialists took part in international projects supported by the ISTC (N 369, N 1443) and the IAEA.

Expected results and their applications

The creation of a database of radioactive pollution parameters for the study area – the Chernobyl caesium hotspot, the Plava River basin in the Tula Region (soil pollution density for different landscape environments within the model catchment, pollution pattern of channel sediment for the model water body and main river channel, specific activity of water). The proposed dataset would have a substantial research value as well as provide an example for developing such radioecological databases in other regions of Russia or other countries.

The development of methods for the synthetic analysis of radiological, geochemical, geophysical, hydrological and geomorphological information on aquatic and land components of geosystems for detailed assessment of the radioecological situation for a specific type of landscape. Such a methodology could incorporate some additional information and would provide an opportunity to expand the field of possible applications (e.g. the influence of redistribution of the initial pollution on biota, population, economy, etc.).

Concept development for complex regional radioecological modeling to predict radionuclide migration in anthropogenically transformed geosystems of polluted territories. An open system that is able to incorporate datasets from other research fields (economics, demography, etc.) would make it possible to more completely analyse the radioecological situation and its influence on a particular region.

Developing models of the radionuclide transfer in anthropogenically transformed geosystems with quantitative evaluation of uncertainly and calibrated/validated using experimental data. Such models would be useful for both forecasting of the behaviour of soil particle-bound radionuclides in other regions and for some specific applied tasks such as the quantification of radionuclide uptake by surface water systems (water quality control), biomass and food products, etc.

The project theme is consistent with the ISTC’s goals of supporting basic and applied research and especially in the field of environmental protection. Collaborating with scientists from France and the UK would help to enhance scientific collaborative links between the Russian and international communities.

Scope of activities

- creation of a computer database on fluvial geomorphic processes and initial radioactive pollution levels for soils and channel sediments, including information on the spatial variability of an initial pollution field;


- the assessment of radinuclide redistribution and migration parameters in land and surface water ecosystems and their validation;
- the development of a dynamic radiological model (incorporating an experimental database) of the radionuclide redistribution within catchments and migration into water systems;
- the calibration of the model and the assessment and forecast of the radioecological situation in geosystems of polluted territories.

Technical approaches and methodology

The proposed project is designed to assess quantitatively the redistribution of an initial fallout field of a soil particle-bound radioactive pollutant (137Cs) within land and surface water landscape components. The caesium isotopes redistribute only in association with soil particles. Therefore, it is necessary to determine the rates of erosion-deposition and geochemical processes as well as the spatial pattern of erosion and accumulation within a study catchment. Two related tasks are to be resolved concurrently: 1) the calibration of a quantitative model of catchment - sediment budget based on radioactive tracer inventory measurements at different geomorphological positions; 2) the assessment of initial pollution transformations using the catchment sediment budget model. The intensity of pollution at particular sites within a catchment or a water system depends on their landscape position and the interaction between the magnitude of an initial atmospheric fallout and soil particle detachment, transportation and re-deposition.

The proposed project will involve the cooperation of scientists and specialists from SPA “Typhoon”, Faculty of Geography of MSU and SSC RF-IPPE. Foreign collaborators in the proposed project are world-leading research groups in the field of studying radionuclide behaviour in the environment. The cooperation will be supported by the regular exchange of information during the project as well as joint collaborative seminars and workshops.


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