Finalist of the international Francophone competition Ma thèse en 180 secondes, Lyon 2023 edition.

Abstract

Numerous organic molecules are synthetized industrially to meet human needs in term of food, health, comfort, etc. They reach aquatic environments through industrial and household wastewater discharges or through rural or urban surface runoff on areas submitted to chemical pressures linked to various human activities. Those molecules can react with each other, be degraded and create transformation products. They can be bioaccumulated in the food chain, with a potential and unpredictable toxicity. According to a chemical equilibrium between dissolved and particulate phases, which is function of their physical-chemical properties, they are partially transferred to sedimented and suspended particulate matters. Moreover, they can be remobilised in the water, and even in the dissolved phase, during floods or dam flushing events. Their presence in the environment has led to the fifth planet boundary being exceeded, which could be one of the main factors responsible for the decline in biodiversity. Historical micropollutants, such as polychlorinated byphenyls, organochlorine pesticides or polycyclic aromatic hydrocarbons, mostly banned and listed in the Stockholm convention, are usually analysed in sediment by mass spectrometry coupled to gaseous phase chromatography (GC-MS). Micropollutants of emerging concerns, such as pharmaceuticals, pesticides, plasticisers and perfluorinated compounds are usually analysed by mass spectrometry coupled to liquid phase chromatography (LC-MS). These methods for target analysis require to purchase analytical standards in order to identify and precisely quantify each micropollutant selected a priori, which limits the number of molecules detected per method. Thanks to the rise of high-resolution mass spectrometry (HRMS), new analytical strategies called suspect and non-target analyses allow identifying more molecules without a priori, with different levels of information and confidence. The objective of this thesis is the exploration of a wide range of emerging organic micropollutants in Rhône River sediments by suspect and non-target analysis. The challenge resides in the numerical and statistical treatment of the data generated by LC-HRMS and in the complexity of the river sediment matrix. A bibliographic study, compiling 163 scientific papers, was firstly achieved to assess the current state of knowledge on the diversity of organic micropollutants already identified in lake and river sediments worldwide and on the analytical methods and strategies. Then, a development of an analytical protocol was carried out, especially on the sediment solvent extraction step prior to non-target analysis by LC-HRMS; and on the chemometric data processing step. Several open-access software programs were combined in order to, i) name/identify some molecules thanks to their fragments, ii) highlight other molecules characterised by chlorinated or fluorinated groups thanks to the interpretation of their isotopic pattern, iii) get an overview of the overall molecular composition of the sample by the study of the high number of detected molecules characterised by their mass to charge and chromatographic retention time. Those methods were applied to sediments sampled upstream and downstream of the city of Lyon, in the Saône and Rhône rivers, between September 2021 and August 2022, as part of the “Rhône sediment observatory” program (OSR). Suspect and non-target analyses enabled to highlight the presence of pharmaceuticals, personal care products, hormones, pesticides, rubber and plastic additives, perfluorinated compounds, flame-retardants, industrial compounds, as well as natural molecules. It also enabled to study the spatial-temporal trends of this contamination around the Lyon area.

Funding

50% Rhône Sediment Observatory (OSR) 50% AQUA Department , INRAE

References

• Escher BI, Stapleton HM, Schymanski EL (2020) Tracking complex mixtures of chemicals in our changing environment. Science, vol 367 p 388-392, DOI: 10.1126/science.aay6636
• Hajeb P, Zhu L, Bossi R, Vorkamp K (2021) Sample preparation techniques for suspect and non-target screening of emerging contaminants. Chemosphere, DOI: 10.1016/j.chemosphere.2021.132306
• Mourier B. et al (2014) Historical records, sources, and spatial trends of PCBs along the Rhône River (France). Science of The Total Environment, vol 476-477 p568-576, DOI:10.1016/j.scitotenv.2014.01.026.
• Richardson S.D. et Kimura SY (2020) Water Analysis: Emerging Contaminants and Current Issues. Analytical chemistery, 92, 1, p 473-505, DOI: 10.1021/acs.analchem.9b05269
• Schulze B. et al (2020) An assessment of quality assurance/quality control efforts in high resolution mass spectrometry non-target workflows for analysis of environmental samples. Trends in Analytical Chemistry, vol 133, DOI:10.1016/j.trac.2020.116063

Cite the thesis

Tom Ducrocq. Exploration des micropolluants organiques dans les sédiments du Rhône par analyse non-ciblée. Chimie. Université claude Bernard Lyon 1, 2025. Français. ⟨NNT : ⟩. ⟨tel-05158839⟩

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