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Browsing by Subject "SOA markers"

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  • Tiusanen, Aleksi (2023)
    Oxidized compounds in the atmosphere can occur as emitted primary compounds or as the products of secondary formation when volatile emitted precursors react with various oxidants. Due to the polar functional groups, their vapor pressures decrease and they condense onto growing small particles or forming new particles by the cloud condensation nuclei reaction. Small particles affect climate change by the formation of clouds and scattering solar radiation. The particles and oxidized compounds themselves could cause serious health problems when inhaled. Thereby, the study of oxidized compounds in the atmosphere is very important. Based on the literature review, the focus of the research is to discover new oxidized species, and to evaluate their sources and factors affecting their formation. Monitoring of biogenic and anthropogenic primary oxidized compounds or secondarily oxidized products in chamber experiments or field campaigns is common. New discoveries have been reported including various new oxidized compounds and a new group of compounds called highly oxidized organic molecules (HOMs). Analytics is mainly focused on chromatographic methods identifying and quantifying compounds in low concentrations. The analytics of HOMs are currently based on high-resolution mass spectrometry employing chemical ionization. Oxidized compounds could also be monitored by spectrophotometric methods in which the determinations of total amounts are based on functional groups. In the experimental part of this thesis, a liquid chromatography-tandem mass spectrometric method applying hydrophilic interaction chromatography was developed to analyze 18 organic acids. The developed method was sensitive to C4-C10 dicarboxylic acids and aromatic acids. In contrast, for smaller and multifunctional acids, the sensitivity decreased due to broader chromatographic peaks. Acids were determined from aerosol samples which were collected with conventional filter sampling and miniaturized filter sampling on a drone. The aim of the work was to compare samples collected with two different sampling techniques to assess if they provided comparable results. Concentration differences between daytime and night-time was assessed from samples taken with conventional filter sampling. C4-C9 dicarboxylic acids, cis-pinonic acid, benzoic acid, phthalic acid, and glycolic acid were detected in both sample types. Possible elimination of adsorption from gas phase to particle phase was demonstrated for cis-pinonic acid and succinic acid due to the lower sample volume in drone sampling. Other detected acids’ concentrations were comparable between two different sampling strategies, considering different sampling sites and extraction methods. Daytime and night-time comparison suggest that acids’ concentrations are higher in daytime when photo-oxidation reactions occur.