Chloé Jariel (MIO) will defend his doctoral thesis on Monday 11 May 2026 à 14h00, in the Conference Room, Centre de Méditerranée, Brégaillon Port Area, CS20 330, 83507 La Seyne-sur-Mer Cedex, on the following topic: Dynamics of Critical Technological Elements (CTE) within coastal ecosystems: the case of the French Mediterranean coast.
Watching the defence via videoconference: Zoom link
Abstract
Technology Critical Elements (TCEs) are chemical elements increasingly used in many sectors relying on advanced technologies, such as transportation, telecommunications, and the medical field. This group includes rare earth elements (REEs), elements belonging to the platinum group (PGEs), as well as other non-traditional metals and metalloids referred to as Less Studied Technology Critical Elements (LSTCEs). The growing production and use of these elements raise concerns regarding their dispersion in the marine environment, particularly in coastal areas subject to strong anthropogenic pressures.
The objective of this thesis was to assess the presence, spatial distribution, and temporal evolution of REE and platinum (Pt) concentrations along the French Mediterranean coastline. To address this objective, an integrated approach was implemented, combining the analysis of archived samples from environmental monitoring programs with samples collected specifically for this study.
Three compartments of the coastal environment were investigated: surface sediments, mussel tissues (Mytilus galloprovincialis), used as biomonitors, and the dissolved phase of seawater. Rare earth elements were quantified by ICP-QQQ-MS following sample digestion. Platinum concentrations were determined using adsorptive cathodic stripping voltammetry (AdSV), a method suitable for the low concentrations encountered in marine matrices and whose protocol was optimized for sediment and biological tissues.
The results show that REE concentrations in sediments are mainly controlled by the lithogenic origin of terrigenous inputs, as indicated by the strong correlation observed with aluminum. Normalized REE distribution patterns appear stable over time and reflect the geochemical signature of the surrounding drainage basins. In mussels, REE patterns display a characteristic inverted “V-shaped” distribution, consistent with the filter-feeding behavior of these organisms. The diachronic analysis of environmental archives (1980–2020) indicates an overall stability of REE concentrations in sediments and a decrease in biological tissues, suggesting a limited influence of recent anthropogenic inputs. In contrast, platinum shows localized enrichments and a progressive increase in concentrations in mussel tissues over the last decades. This trend is consistent with the increasing demand for Pt, particularly associated with the use of automotive catalytic converters. Although no generalized contamination is observed along the French Mediterranean coastline, these results highlight the emergence of an anthropogenic signal for platinum in the biological compartment.
This study emphasizes the importance of long-term monitoring of TCEs in coastal environments and proposes a natural baseline threshold for platinum in Mediterranean sediments. It thus contributes to a better understanding of the environmental fate of these strategic metals.
Key words
Emerging contaminants, Technology Critical Elements, Biogeochemical cycle, Speciation/bioavailability, Marine ecosystems.
Composition of the jury
- Joint supervisor – Stéphanie Jacquet, Research Fellow – CNRS MIO
- Joint supervisor – Jean-Louis Gonzalez, Senior Researcher – IFREMER LER
- Examiner – Pascale Prudent, Senior Lecturer – Aix-Marseille University
- Rapporteur and Chair of the jury – Chrystelle Montigny, University Professor – University of Montpellier
- Examiner – Jörg Schafer, University Professor – University of Bordeaux
- Rapporteur – Sylvain Rigaud, Senior Lecturer – University of Nîmes UPR7352 CHROME
- Examiner – Gabriel Billon, University Professor – University of Lille
- Guest speaker, co-supervisor – Stéphane Mounier, Senior Lecturer – University of Toulon MIO
- Guest, co-supervisor – Christophe Brach-Papa, Head of the LER – IFREMER