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Laboratoire d'Ecogéochimie des Environnements Benthiques
UMR 8222

Leonardo Contreira-Pereira (2009-2012)

Autonomous voltametric and potentiometric sensors: toward long-term monitoring of sulfur dynamics at redox-interfaces.

Directrice de thèse : Nadine Le Bris

Sulfide, and other reduced sulfur compounds, are among the most important chemical parameters in many marine environments characterized by redox gradients (e.g. hydrothermal vents, methane seeps, as well as organic matter enriched sediments). The variability of their concentration over time is likely to constitute an important driver of biodiversity establishment and chemosynthetic inorganic carbon fixation in these environments. Tools are however lacking to monitor these compounds within dynamic redox interfaces over periods of days to months.

Electrochemical techniques have proven to be particularly relevant for the monitoring of dynamic redox interfaces (e.g.: sulphidic sediments associated with hydrothermal vents, methane seeps or organic matter degradation), but they still need improvement for long-term use. The project aims to further develop these methods for the monitoring of deep and shallow-water marine environment.

The work will be based on recently developed autonomous probes and in situ voltammetric and potentiometric methods for reduced sulphur species (e.g. hydrogen sulfide, aqueous iron sulfide, polysulfides, thiosulfate, sulfite). The objective is to improve existing methods and electrode design to optimize measurement temporal stability. Validation of the methods will be performed on field-test stations at variable depth under the frame of the EC SENSENET Marie Curie Network.

This work will also contribute to the interdisciplinary study of marine communities relying on sulfide-oxidizing bacteria in deep and shallow-water environments, as part of current European collaborative projects (GDRE DiWOOD, IP-HERMIONE). The sensors will be integrated into a modular experimental plateform designed to investigate colonization processes in relation to chemical changes in various chemosynthetic habitats (hydrothermal vents, mangrove swamp, massive wood fall).

Leonardo Contreira (leonardo.contreira @ obs-banyuls.fr) - 10/11/19

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