Spéciation du cuivre en milieu hydrothermal profond et dans les zones de suintements froids

Abstract : This work presents the copper speciation in the deep ocean and the exchanges existing between different size fractions : particulate, dissolved and colloidal. It focus on the mixing zone between deep sources and seawater. The enhancement of our knowledge and the optimization of instrumentation make possible the development of sampling and analysis strategies accorded with the nature and the accessibility of these extreme environments. A part of this work consisted in the development of effective analysis methods for the quantification of copper and copper’s ligands. Our results showed that physical speciation seems to be essentially controlled by the variations of pH and oxydoreductive caracteristics during the dilution of the hydrothermal fluid by seawater. The chemical speciation of copper seems essentially controlled by sulfide ligands and the oxydative caracteristics of the environment. The environment is generally more complexing on Lucky Strike vent field than in Guaymas Basin. Around each vent, pseudopolarography and complexing capacities showed that the environment is more complexing in the anoxic zone, near the source, than in the oxic zone. In the oxic zone, copper is generally labile and its concentrations (they can reach 100 nM) exceed the ligands concentrations. In the oxic zone, around 27% of the complexes are dissociated, whereas around 73% remains stabilised.
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Virginie Aumond. Spéciation du cuivre en milieu hydrothermal profond et dans les zones de suintements froids. Autre. Université de Bretagne occidentale - Brest, 2013. Français. ⟨NNT : 2013BRES0043⟩. ⟨tel-01057808⟩

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