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Amélioration de la chronologie des retombées initiales de radionucléides pour reconstruire les taux de redistribution de sol dans les bassins versants agricoles d’Amérique du Sud

Abstract : The Green Revolution of the 1960s led to a significant increase in cultivated land at the expense of natural ecosystems in South America. Consequently, soil erosion processes have rapidly increased, threatening the sustainability of agricultural systems and leading to the siltation of rivers and reservoir siltation. However, only limited information is available at the scale of this continent to quantify the impact of soil erosion and promote effective management strategies to reduce soil losses. To overcome this lack of data, this doctoral project synthesised all the data related to the artificial radionuclide fallout (137Cs, plutonium) in soils of South America between 1952 and 1980 following atmospheric nuclear weapon testing.Fallout radionuclides bound to fine-grained sediment are widely used to date sedimentary sequences and reconstruct soil redistribution rates a posteriori. A spatialization of 137Cs inventories in soils at the sub-continental scale of South America is proposed, as well as a sampling strategy to improve this map in the future. Then, the potential of 240Pu/239Pu atom ratio analyses in soils and sediment to refine these temporal reconstructions is demonstrated. Finally, as an application, a novel approach to sample and analyse 137Cs in 80 soil profiles collected across a representative 800-km² catchment of an intensively cultivated region of Brazil for the period 1970-2020 is proposed, and its limitations are discussed.
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Submitted on : Sunday, July 3, 2022 - 1:02:52 AM
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  • HAL Id : tel-03712266, version 1

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Pierre-Alexis Chaboche. Amélioration de la chronologie des retombées initiales de radionucléides pour reconstruire les taux de redistribution de sol dans les bassins versants agricoles d’Amérique du Sud. Environnement et Société. Université Paris-Saclay, 2021. Français. ⟨NNT : 2021UPASJ018⟩. ⟨tel-03712266⟩

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