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Long-term and long-range migration of radioisotopes in terrestrial systems: Mechanisms of radioisotope (Cs, Sr, Pu, Am) mobilisation in soils

English title Long-term and long-range migration of radioisotopes in terrestrial systems: Mechanisms of radioisotope (Cs, Sr, Pu, Am) mobilisation in soils
Applicant Froidevaux Pascal
Number 115915
Funding scheme Project funding (Div. I-III)
Research institution Institut de Radiophysique Département de Radiologie Université de Lausanne/CHUV
Institution of higher education University of Lausanne - LA
Main discipline Geochemistry
Start/End 01.04.2007 - 31.03.2010
Approved amount 198'514.00
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Keywords (8)

radioactive fallout; radioecology; soil solution; colloids; radiochemistry; radio-ecology; radio-chemistry; radioisotope migration models

Lay Summary (English)

Lay summary
We study the long-term and long-range migration of artificial radioactive elements in the terrestrial (soil) environment. Our goal is a broad understanding of the radio-ecology of the radioisotopes cesium-137, radio-strontium, plutonium, and americium. These elements have been released to the environment by fallout from nuclear weapon tests (NWT) and nuclear accidents (Chernobyl and others).
In the present project we investigate the behaviour of radioisotopes in an alpine catchment, Val Piora, Ticino. This site has been chosen because we find there a variety of soils developed on gneisses, carbonate rocks, and moraines. Moreover, due to its high altitude (2000 m and more) the area received more radioactive deposition than a low land site.
We will, in a first step, determine the radioisotope distribution within the different soil types. Then the focus will be on the soil water and on the colloids (i.e. the tiniest particles, which are suspended in the soil water). Previous studies have shown, that even insoluble elements such as Plutonium, may be transported with the soil water or with groundwater, if these elements are attached onto colloids.
Soil water will be sampled using suction lysimeters and the colloids will be separated using cross-flow ultrafiltration. For the fieldwork a good scientific infrastructure is available on the site (the "Piora centre for alpine biology"). Later, in the laboratory, the radioisotopes in the various samples will be analyzed using well-established methods combining chemical separation and alpha spectrometry. Regarding the concentrations of the actinides in the soil solutions we will develop/adapt mass spectrometric methods in collaboration with a sector-field ICP-MS laboratory. Radiochemical analyses will be supplemented with detailed analyses of geochemical and hydrological parameters. Complementary samples (vegetation, surface water, and milk) will be taken in order to assess other pathways of radioisotope elimination from the soil, such as e.g. plant uptake.
The obtained data set will serve to construct a realistic radioisotope budget for the studied catchment area. This information may then be used in radio-ecological models.
The outcomes of our study will contribute to a better understanding of the role of colloids for the migration of contaminants in soils. By analogy our results will help the understanding of the behaviour of other contaminants, such as heavy metals or persistent organic pollutants. The studied processes are relevant for the mitigation of contaminated sites and the conception of waste disposal sites. This work involves one PhD student.
Direct link to Lay Summary Last update: 21.02.2013

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