| Summary: | Our planet is a highly complicated system and the atmosphere – the layer of gases surrounding the globe – enables organisms to breathe and live. Within this layer, aerosol particles can impact human’s health, when inhaled, but they can also interact with the Earth’s climate in many ways and on many different scales. Aerosols can origin from very different sources, natural or man-made, emitted as is or transformed from gases, through chemical reactions, to particles. These secondary aerosols formed through new particle formation (NPF) have drawn a lot of attention as they can contribute significantly and/or predominantly to the cloud condensation nuclei budget and further impact the climate. For this reason, it is crucial to understand what are the chemicals and physical processes that trigger the formation of new particles. Atmospheric oxidation is an important process that is responsible for a variety of gases and condensable vapors that can initiate atmospheric nucleation and/or contribute to particle growth. Among these vapors, highly oxygenated organic molecules (HOM) are formed by the oxidation of volatile organic compounds via a complex chain reaction yet not fully characterized. This thesis tackles several aspects linked to aerosol formation and the formation of their gas-phase precursors in cold environment. This work combines experimental work and field observations, with (1) the simulation of an oxidation reaction, alpha-pinene ozonolysis - known to form HOM, at different temperatures, (2) the analysis of the oxidizing agent, ozone, over 20 years at a boreal forest site, and finally (3) the exploration on precursor vapors forming aerosol in the Antarctic peninsula. This work involved the operation of multiple instruments, especially including the state-of-the-art chemical ionization atmospheric pressure interface time of flight mass spectrometer (CI-APi-TOF) to detect HOM and other condensable vapors, or alternatively naturally charged ions (i.e., without chemical ionization). Using atmospheric chamber ...
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