Natalia Torres-Rodriguez, D. in Environmental Sciences, specialising in Chemical Oceanography, was awarded this Wednesday 10 December 2025, the 2025 thesis prize awarded by the City of Marseille.
His doctoral work focused on the following subject: Dynamics and distribution of marine mercury species.
Mercury is a pollutant that poses a threat to humans and ecosystems around the world. The United Nations Minamata Convention on Mercury, in force since 2017, aims to protect public health and the environment from the toxic effects of mercury. To achieve the objectives of the convention, a general understanding of the global mercury cycle is required. This work presents mercury speciation data from a transect during a GEOTRACES oceanographic mission covering most of the southern Indian Ocean. Measurements of mercury in seawater, particles, sediments, aerosols and rain were combined to calculate fluxes between the atmospheric, oceanic and seafloor compartments. High escape rates are only observed in areas under the influence of the Agulhas Current. The results reveal a significant imbalance between dry and wet deposition, escape and vertical export fluxes at the southernmost stations, indicating that the Indian sector of the Southern Ocean may act as a mercury sink. They also indicate relatively constant mercury concentrations in hydrothermal fluids across mid-ocean ridges, in contrast to those found in arc volcanoes. Using a dilution model, it was established that mercury of hydrothermal origin behaves in a quasi-conservative manner once it is released. Traces of hydrothermal mercury can be detected hundreds of kilometres away and in distant sediments. Scaling up his results, his work suggests a flow of mercury from hydrothermal vents in both arc volcanoes and mid-ocean ridges, which together account for the majority of submarine hydrothermal vents.
