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Application de la chromatographie d'exclusion stérique multi-détection à l'étude de la spéciation de la matière organique dissoute en milieu estuarien et côtier

Abstract : Dissolved organic matter (DOM) is one of the most important vector of carbon to the ocean.However, DOM is deeply altered during its transit through estuarine waters and its residence time in Coastal waters. The purpose of this thesis is to bring new insights on the DOM composition, role in biogeochemical cycles during land-sea transfer and fate in Coastal areas. DOM analysis was performed with a global and semi-specific tool: size-exclusion chromatography multi-detection (SEC-mDEC), which allow the separation of DOM into six size fractions of different nature. Dynamics of these compounds are studied seasonally in the Aulne estuary and the bay of Brest. The coupling between SEC-mDEC and 3D fluorescence was studied in the estuary.Initially design for freshwater analysis, the adapted SEC-mDEC for estuarine and marine water analyses permitted the demonstration that DOM is involved in several biogeochemical processes. In the Aulne estuary, DOM tracks the contribution of both riverine and marine sources. Substantial changes are made to the DOM by microorganisms and flocculation processes upstream. In the Bay of Brest, ail fractions enable to design a reactivity continuum from the bacterial degradation of the phytoplanktonic bloom.Results demonstrate that the single use of the global dissolved organic carbon is not enough to constrain DOM dynamic in the land-sea continuum.
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Submitted on : Friday, October 2, 2020 - 4:17:08 PM
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Johann Breitenstein. Application de la chromatographie d'exclusion stérique multi-détection à l'étude de la spéciation de la matière organique dissoute en milieu estuarien et côtier. Autre. Université de Bretagne occidentale - Brest, 2019. Français. ⟨NNT : 2019BRES0074⟩. ⟨tel-02956331⟩

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