Nitrogen-containing products from atmospheric oxidation of volatile organic compounds
2022
unknown
Zugriff:
Atmospheric oxidation of volatile organic compounds (VOC) produces a wide range of oxygenatedorganic products that lead to formation of secondary organic aerosol (SOA). SOA represents asignificant fraction of the tropospheric aerosol that influence climate and human health. However,the level of understanding of SOA processes is low compared to other aerosol processes and onereason is the complexity of VOC oxidation under various conditions. VOC oxidation under highNOx conditions or by nitrate radicals (NO3) leads to formation of various nitrogen-containingcompounds. The N-containing products, apart from contributing to SOA formation, can act asNOx reservoir and/or as permanent sink affecting ozone formation. Also, organic nitrogen canplay a role on the atmospheric nitrogen cycle, with ecological impacts.In this work the focus is on the nitrogen-containing oxidation products in the gas phase andtheir contribution to the particle phase. Laboratory studies on OH-initiated oxidation of 1,3,5-trimethylbenzene (TMB) (an anthropogenic VOC) under different NOx levels and NO3-initiatedoxidation of isoprene (the most abundant non-methane biogenic VOC) were conducted utilizingthe Go:PAM flow reactor and the atmospheric simulation chamber SAPHIR. The oxidationproducts from these reactions were detected using chemical ionization mass spectrometry. Thismethod was also applied in the field to measure selected organonitrates related to the laboratorystudies.The TMB oxidation under elevated NOx conditions favored the formation of organonitrates(ONs) reducing the amount of highly oxygenated organic molecules (HOM) monomers andespecially the dimers, leading to suppression of new particle formation. Ambient observations ofnitro-aromatic compounds originating from anthropogenic sources demonstrated that nitrophenoland its analogue can be used as direct tracers of primary emissions from biomass burning.NO3 oxidation of isoprene produced monomers and dimers with 1 to 3 nitrate groups. Thespecifics of the various time evolutions indicating formation pathways from multi-generationsecondary chemistry. Selected products from this secondary chemistry had high propensity toparticipate to the particle phase. Observations from six locations around the globe showedthat the isoprene-derived ONs with chemical formula C4H7NO5 observed in the laboratory diddominate the ambient gas phase product distribution both during nighttime and daytime.To summarize, the objectives of this thesis are to advance our understanding on the nitrogen-containingproducts from atmospheric oxidation of different VOC, identify their reactionmechanisms and product distributions, and provide insights on their role to SOA formation.
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Nitrogen-containing products from atmospheric oxidation of volatile organic compounds
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Autor/in / Beteiligte Person: | Tsiligiannis, Epameinondas |
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Veröffentlichung: | 2022 |
Medientyp: | unknown |
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