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Analytical Developments for Measuring Atmospheric Peroxy Radicals

Abstract : Peroxy radicals (HO2 and RO2) are key species in atmospheric chemistry, which together with the hydroxyl radical (OH), are involved in oxidation processes leading to the formation of secondary pollutants such as ozone and organic aerosols. Monitoring these short-lived species during intensive field campaigns and comparing the measured concentrations to box model simulations allow assessing the reliability of chemical mechanisms implemented in atmospheric models. However, ambient measurements of peroxy radicals are still considered challenging and only a few techniques have been used for field measurements.The main objective of this work was to improve our knowledge on two measurement techniques: CA (Chemical Amplification) and ROxLIF (Rox Laser Induced Fluorescence). CA is a chemical technique for measuring the sum of peroxy radicals (HO2+RO2) whose simplicity and low cost makes it attactive for field measurements. ROxLIF is a laser-based technique allowing to speciate HO2 and the sum of RO2. In the first part of this thesis, a two-channel chemical amplifier was built at IMT Lille Douai (France) and characterized using 2 different amplification chemistries (PERCA, PEroxy Radical Chemical Amplifer, and ECHAMP, Ethane CHemical AMPlifier). In a second part, the ROxLIF technique was implemented on an existing FAGE (Fluorescent Assay by Gas Expansion) instrument at Indiana University (United States). Both the CA and ROxLIF were tested for ambient measurements. In a last part, the CA using the PERCA approach, ROxLIF and an additional technique based on chemical ionization mass spectrometry were intercompared at the HELIOS atmospeheric chamber in Orleans (France). Several experiments were conducted to investigate the reliability of peroxy radical measurments.
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Ahmad Lahib. Analytical Developments for Measuring Atmospheric Peroxy Radicals. Theoretical and/or physical chemistry. Ecole nationale supérieure Mines-Télécom Lille Douai, 2019. English. ⟨NNT : 2019MTLD0022⟩. ⟨tel-02610413⟩

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