Nature, origin and reactivity of fossil organic matter in soils and sediments: Developments and applications of the Photoionization - High Resolution Mass Spectrometry (APPI-QTOF) and Coupling with Size Exclusion Chromatography (SEC) ; Nature, origine et réactivité de la matière organique fossile dans les sols et sédiments : développements et applications de la photoionisation - spectrométrie de masse haute résolution (APPI-QTOF) et couplage avec la chromatograhie d'exclusion stérique (SEC)

The development of analytical tools for organic geochemistry analysis has increased these past years. This development has allowed answering many questions about organic matter composition. However, many issues remain to be clarified including the characterization of high molecular weight fractions and monitoring the reactivity of organic matter. This thesis has focused on both (i) existing method improvements for fossil organic geochemistry analysis but also on (ii) developing a new type of coupling between the size exclusion chromatography (SEC) and the APPI-QTOF mass spectrometry for high molecular weight weakly polar fractions. Adjustments on APPI-QTOF mass spectrometry have allowed a better understanding of polyaromatic organic contaminant reactivity in presence of mineral matrices. The success of this coupling has allowed a better understanding of the structure of asphaltenes. However despite the "simplification" obtained by the SEC, the large amount of information remains difficult to interpret and time-consuming. A mathematical model has been developed based on numerical and statistical analysis of mass spectra, allowing direct comparison of mass spectra and being able to identify several types of information such as origins of samples, monitoring of physico-chemical processes and also the efficiency of soil recovery treatments as well as the identification of analytical protocols. ; Le développement des outils analytiques pour l'analyse de la matière organique complexe en géochimie organique a connu de nombreuses avancées ces dernières années. Ce développement a permis de répondre à un grand nombre de questions quant à la composition de la matière organique. Cependant, beaucoup des points restent encore à élucider comme notamment la caractérisation des fractions de hauts poids moléculaires ainsi que le suivi de la réactivité de la matière organique. Ce travail de thèse a eu pour objectif (i) d'adapter les techniques de spectrométrie de masse déjà existantes pour l'analyse de la matière organique fossile ...