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Browsing by Author "Quéléver, Lauriane Lucie Josette"

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  • Quéléver, Lauriane Lucie Josette (2016)
    Recent studies proved the existence of Extremely Low-Volatility Organic Compounds (ELVOCs) in the atmosphere as result from oxidation of biogenic vapors released by terrestrial vegetation. Such species are believed to significantly contribute to the formation of Secondary Organic Aerosols (SOA) which play a role in Cloud Condensation Nuclei (CCN) process and thus affect climate. Thus, it is of interest to better understand and characterize the behavior of these novel molecules. The literature part provides an overview of the background knowledge that found this work by presenting the influence of aerosols and emissions from biosphere on climate. Moreover, the chemical pathways involved in the formation of ELVOCs are presented as well as the factors that could possibly influence their production. In the experimental part is presented an investigation of the thermal stability of ELVOCs formed by oxidation of both α-pinene and benzene using flow tube reactor setup and mass spectrometry analysis. After development and characterization of the experimental installation, it was possible to analyze the thermal response of highly oxidized compounds with a nitrate-based Chemical Ionization (CI) Atmospheric Pressure interface (APi) Time Of Flight (TOF) mass spectrometer which provided a unique characterization of such species with high precision. In this study, the establishment of temperature ranges for the decomposition of ELVOCs was done by collecting the data for several identified highly oxidized species. Furthermore, some differences in the obtained 'temperature series' (evolution of the signal as a function of temperature) were observed from one experiment to another confirming the high variability in the behavior of such compounds. In a more comprehensive sense, this work allowed to develop a more complete view on the behavior of ELVOCs toward a change of temperature.