Description of the thesis topic

Description of thesis topic :impact of climate on radionuclide transfer to plants
Climate change, and in particular the warming observed in recent decades, has raised the central question of its impact on the transfer processes of pollutants that can accumulate in the critical zone in connection with human activities. The aim of this thesis is to study the transfer of radionuclides in plants under two highly contrasting climatic conditions: temperate/humid climate (e.g. Western Europe) vs. hot/dry climate (e.g. desert in the United Arab Emirates). The aim is to compare these two extreme situations (and even other intermediate climatic conditions) in order to anticipate the evolution of the situation of various territories according to the warming projections issued by the IPCC. The work undertaken as part of Alice Hazotte's thesis [1-3] on the role of bacterial metabolites on the bioavailability of caesium for phytoextraction, and that of the RADTRANS project (United Arab Emirates) focused on understanding the fate of radionuclides in the environment, in the case of radioactive waste management, will serve as a starting point for the proposed project. Expected results will include soil/plant transfer coefficients for radionuclides as a function of climatic parameters, and will contribute to understanding the mechanisms governing this transfer. This study will go beyond the assessment of the environmental impact of radioactivity and produce forward-looking data in terms of knowledge of the effect of climate change on radio-ecological processes.
[1] HAZOTTE, A.A., PÉRON, O., ABDELOUAS, A., MONTAVON, G., LEBEAU, T. Microbial mobilization of cesium from illite: The role of organic acids and siderophores. Chemical Geology 428, 8-14 (2016).
[2] HAZOTTE, A.A., PÉRON, O., GAUDIN, P., ABDELOUAS, A., LEBEAU, T. Effect of Pseudomonas fluorescens and pyoverdine on the phytoextraction of cesium by red clover in soil pots and hydroponics. Environmental Science and Pollution Research 25, 20680 – 20690 (2018).
[3] PÉRON, O., SUZUKI-MURESAN, T., ABDILLAHI, D., GAUDIN, P., ABDELOUAS, A., LEBEAU T. Effect of the bacterial pyoverdine siderophore on the phytoextraction of cesium from illite. Environmental Chemistry Letters, ISSN 1610-3653, 09/2018 1-6 (2018).

Work Context

The proposed project is of great scientific interest for the transfer of chemical and radiological toxins in the environment. Its aim is to propose a global approach to understanding radionuclide/plant interactions with climate change. Thus, the literature on the study of soil-plant transfers of radionuclides, each time in a given climatic context, but none in an approach of climatic evolution of a given territory [4-5]. Moreover, this research is limited to soil-plant transfer, without taking into account the role of soil microbial components, which are strongly involved in modulating these transfers.
The scientific objectives of the proposed project are to:
• Understand the mechanisms of soil/plant transfer of radionuclides under two contrasting climatic scenarios (temperate/humid climate (e.g. Europe) vs. hot/dry climate (e.g. desert of the United Arab Emirates).
• Understand the role of the rhizospheric bacterial community in terms of radionuclide phyto-availability under the two climate scenarios.

The methodology developed to achieve these objectives includes:
• A nucleated phytotron recently acquired and implemented by Subatech will be used to carry out soil-plant transfer studies including the role of rhizospheric bacteria. This phytotron will be used to set relative humidity, plant culture temperature and lighting (light intensity and day/night cycle). This equipment will enable us to recreate the climatic conditions required for our experiments. Given the limited volume of this phytotron, additional experiments in non-nuclearized phytotrons (with radionuclide analogues) could be carried out at the LPG, in order to increase the number of modalities tested (different plant species, different soils, climatic scenarios other than the two extreme scenarios).
• The first experiments will be carried out in hydroponics, a system in which the radioactive pollutant is mainly bioavailable, making it possible to simplify the experimental system (initially) by eliminating radionuclide speciation linked to the presence of mineral and organic carrier phases in the soil.
• The following experiments will be carried out in soil/sand pots to approximate a natural system and assess soil/plant transfer coefficients according to soil type (high vs. low radionuclide bioavailability).
[4] Dowdall, M., et al. "Will global warming affect soil-to-plant transfer of radionuclides?." Journal of Environmental Radioactivity 99.11 (2008): 1736-1745.
[5] Yadav, Poonam, and Bhupinder Singh. "Radioecology: dissecting complexities of radionuclide transfer under climate change." Global Climate Change. Elsevier, 2021. 297-320.

The candidate must hold a Master's degree in Earth and Environmental Sciences.
The skills, knowledge and experience required of the candidate will be :
- general knowledge of life and earth sciences
- implementation of plant cultures in phytotron
- tracing of pollutants
- valorization of research work

Skills, knowledge and experience desirable for the
candidate will be a plus in:
- Radiochemistry
- Microbiology

The candidate must demonstrate the ability to work in a research environment and be a team player.

The candidate must be fluent in written and spoken English.

Rigor, autonomy and organizational skills are required.

The following documents must be enclosed with the application:
- Detailed, up-to-date CV
- Covering letter

The laboratories involved in the project (Subatech and LPG) are very well equipped, in particular with phytotrons for plant cultivation under controlled conditions. They are also equipped with laboratories for microbial cultivation and for physico-chemical characterization of aqueous and solid matrices. The supervisory team comprises 2 professors (A. Abdelouas - IMT Atlantique; T. Lebeau - Nantes Université) and a lecturer (O. Péron - Nantes Université). Technical staff from the 2 laboratories will also be involved.

The position is located in a sector under the protection of scientific and technical potential (PPST), and therefore requires, in accordance with the regulations, that your arrival is authorized by the competent authority of the MESR.

Constraints and risks

The student recruited will be integrated into the Radiochemistry team in order to conduct laboratory experiments in a supervised area and to promote them by writing Rank A publications. Part of the experiments will also take place at the LPG, where the student recruited will carry out bacterial or even plant cultures on radionuclide analogues - as the volume of plant cultures under nuclearized conditions at Subatech is limited. The student will be in charge of the experimental part of the project, which involves studying the behavior of radionuclides from nuclear waste in soils up to their transfer to plants. The student recruited will therefore be required to grow plants, carry out radioactive labeling, study the chemical speciation of radionuclides, and assess soil-plant transfer and therefore the potential environmental risk.