Reference : UMR5254-SOPPUY-055
Workplace : PAU
Date of publication : Wednesday, September 14, 2022
Scientific Responsible name : Aubin Thibault de Chanvalon and Thierry Pigot
Type of Contract : PhD Student contract / Thesis offer
Contract Period : 36 months
Start date of the thesis : 15 November 2022
Proportion of work : Full time
Remuneration : 2 135,00 € gross monthly
Description of the thesis topic
Reactive oxygen species (ROS) degrade many environmental contaminants when used in wastewater treatment plants. ROS have recently been identified in coastal environments rich in iron oxides and sulfur compounds and could then serve as a self-purifying agent. However, highlighting the services provided by ROS-producing ecosystems requires a detailed description and modeling of the mechanisms of ROS production, particularly in heterogeneous environments and/or subject to redox oscillations. In this respect, the identification of the intermediate reaction species at the interface of the O2/Fe/H2S cycles is essential. In addition to ROS concentrations (O2•-, H2O2, OH•, 1O2), iron speciation (Fe(II), Fe(III), Fe(III)=L, FeOOH, Fe2O3), sulfur species (Sn2-, S0, S2O32-, SO32-, H2S, SO42-) and iron sulphides (FeSnano, FeS, FeS2) will be monitored during redox oscillations produced in the laboratory on synthetic substrates. The observed reactions will then be modeled. An in situ demonstration of the importance of these reactions will be provided by field sampling from three study sites constituting an iron and sulfur concentration gradient. Finally, substrates sampled on each sites will be subjected to redox oscillations in order to verify, in complex media with organic matter and carbonates, the occurrence of ROS production reactions.
The thesis work will mainly be carried out in the IPREM laboratory (UMR CNRS 5254), at the forefront of analytical chemistry for the study and characterization of environmental matrices. Among the different analysis techniques available: new generation ICP-MS (multiquad in single particle mode), absorbance spectrophotometry, spectrofluorimetry and electrochemical sensors. Several sampling campaigns (1 week) are to be expected. A secondment of a few months at the University of South Carolina to get trained with other methods of in situ analysis of ROS could be considered.
This thesis is part of the ESCIS project funded by the National Research Agency (ANR JCJC 2022-2027) which aims to characterize the ecosystem services provided by ROS-producing environments. Close collaboration with all the scientists involved, in particular a second doctoral student studying the degradation of certain contaminants during redox oscillations is expected.
- Master 2 in analytical or environmental chemistry, engineering degree.
- Strong taste for experimentation (rigor, organization, etc.).
- Knowledge of the analytical techniques mentioned (ICP-MS, Spectroscopies, electrochemistry)
- Communication and scientific openness.
Aubin Thibault de Chanvalon firstname.lastname@example.org
Thierry Pigot email@example.com
Constraints and risks
Several sampling campaigns (1 week) are to be expected. A secondment of a few months at the University of South Carolina to get trained with other methods of in situ analysis of ROS could be considered.
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