Pollutant Mobilization Induced by Saltwater Intrusion: Biogeochemistry and Dynamics at the Water–Sediment Interface under Climate Change Conditions – PhD Position (M/F)

Job Description

Thesis Subject

Saltwater intrusion, intensified by climate change, sea-level rise, and anthropogenic pressures, is emerging as a significant driver of geochemical instability in coastal and industrialized environments. By altering redox gradients, ionic composition, and biogeochemical equilibria, saltwater intrusion promotes the mobilization of metals, metalloids, and nutrients that were previously trapped within sediments. These disturbances can also modify benthic microbial communities, with important consequences for water quality, ecosystem functioning, and the management of contaminated sediments.

The MOBIDICC project aims to understand and model the mechanisms governing contaminant remobilization under different saltwater intrusion scenarios in industrialized coastal sediments of the Dunkirk region. The research will combine controlled laboratory experiments, advanced geochemical analyses, molecular microbiology, and high-resolution geophysical investigations.

The PhD candidate will develop experimental column and mesocosm systems to simulate various saltwater intrusion scenarios, including progressive, pulsed, vertical, and lateral intrusions. High-frequency geochemical monitoring (O₂, Eh, pH, conductivity, dissolved sulfides, Fe/Mn speciation, trace metals, anions, etc.) will be conducted to characterize the processes of desorption, reductive dissolution, and sulfide formation that control contaminant mobility. Particular attention will be paid to the interactions between organic matter degradation, microbial activity, and redox transitions.

High-resolution two-dimensional imaging techniques (notably optodes and DGTs) will be employed to map biogeochemical gradients at the sediment–water interface. Microbial communities will be investigated through DNA sequencing and quantitative PCR analyses, in collaboration with the University of Mons (Belgium). Field campaigns in the industrial canals of Dunkirk will provide validation of the experimental results and enable the linkage of laboratory observations with real-world saltwater intrusion dynamics.

The project will also integrate geophysical methods, including electrical resistivity tomography and ground-penetrating radar, to characterize salinized groundwater plumes. The ultimate objective is to improve our understanding of the biogeochemical response of coastal sediments to different saltwater intrusion scenarios and to provide operational recommendations for the management of coastal environments that are vulnerable to climate change, particularly in the context of dredged sediment management.

Your Work Environment

This PhD project will be carried out within the LASIRE laboratory at the University of Lille, in collaboration with the LOG laboratory (University of Lille) and the Proteomics and Microbiology Service of the University of Mons (Belgium).

The PhD candidate will be supervised by:
- Ludovic Lesven and Baghdad Ouddane (LASIRE, University of Lille), specialists in trace metal geochemistry and biogeochemical processes at the water–sediment interface;
- Annette Hofmann (LOG, University of Lille), specialist in geochemical and geophysical modelling;
- David Gillan (University of Mons, Belgium), specialist in environmental microbial communities.

Compensation and benefits

Compensation

2300 € gross monthly

Annual leave and RTT

44 jours

Remote Working practice and compensation

Pratique et indemnisation du TT

Transport

Prise en charge à 75% du coût et forfait mobilité durable jusqu’à 300€

About the offer

About the CNRS

The CNRS is a major player in fundamental research on a global scale. The CNRS is the only French organization active in all scientific fields. Its unique position as a multi-specialist allows it to bring together different disciplines to address the most important challenges of the contemporary world, in connection with the actors of change.

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