α-pinene photooxidation under controlled chemical conditions – Part 2: SOA yield and composition in low- and high-NO<sub>x</sub> environments
The gas-phase oxidation of α-pinene produces a large amount of secondary organic aerosol (SOA) in the atmosphere. A number of carboxylic acids, organosulfates and nitrooxy organosulfates associated with α-pinene have been found in field samples and some are used as tracers of α-pinene oxidation. α-p...
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2012-08-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | http://www.atmos-chem-phys.net/12/7413/2012/acp-12-7413-2012.pdf |
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| author | P. O. Wennberg J. H. Seinfeld P. S. Chhabra M. Chan K. A. Schilling L. D. Yee N. C. Eddingsaas C. L. Loza |
| author_facet | P. O. Wennberg J. H. Seinfeld P. S. Chhabra M. Chan K. A. Schilling L. D. Yee N. C. Eddingsaas C. L. Loza |
| author_sort | P. O. Wennberg |
| collection | DOAJ |
| description | The gas-phase oxidation of α-pinene produces a large amount of secondary organic aerosol (SOA) in the atmosphere. A number of carboxylic acids, organosulfates and nitrooxy organosulfates associated with α-pinene have been found in field samples and some are used as tracers of α-pinene oxidation. α-pinene reacts readily with OH and O<sub>3</sub> in the atmosphere followed by reactions with both HO<sub>2</sub> and NO. Due to the large number of potential reaction pathways, it can be difficult to determine what conditions lead to SOA. To better understand the SOA yield and chemical composition from low- and high-NO<sub>x</sub> OH oxidation of α-pinene, studies were conducted in the Caltech atmospheric chamber under controlled chemical conditions. Experiments used low O<sub>3</sub> concentrations to ensure that OH was the main oxidant and low α-pinene concentrations such that the peroxy radical (RO<sub>2</sub>) reacted primarily with either HO<sub>2</sub> under low-NO<sub>x</sub> conditions or NO under high-NO<sub>x</sub> conditions. SOA yield was suppressed under conditions of high-NO<sub>x</sub>. SOA yield under high-NO<sub>x</sub> conditions was greater when ammonium sulfate/sulfuric acid seed particles (highly acidic) were present prior to the onset of growth than when ammonium sulfate seed particles (mildly acidic) were present; this dependence was not observed under low-NO<sub>x</sub> conditions. When aerosol seed particles were introduced after OH oxidation, allowing for later generation species to be exposed to fresh inorganic seed particles, a number of low-NO<sub>x</sub> products partitioned to the highly acidic aerosol. This indicates that the effect of seed acidity and SOA yield might be under-estimated in traditional experiments where aerosol seed particles are introduced prior to oxidation. We also identify the presence of a number of carboxylic acids that are used as tracer compounds of α-pinene oxidation in the field as well as the formation of organosulfates and nitrooxy organosulfates. A number of the carboxylic acids were observed under all conditions, however, pinic and pinonic acid were only observed under low-NO<sub>x</sub> conditions. Evidence is provided for particle-phase sulfate esterification of multi-functional alcohols. |
| first_indexed | 2024-04-13T17:18:31Z |
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| issn | 1680-7316 1680-7324 |
| language | English |
| last_indexed | 2024-04-13T17:18:31Z |
| publishDate | 2012-08-01 |
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| spelling | doaj.art-6ab5cd1883754288bcd8f415939795672022-12-22T02:38:04ZengCopernicus PublicationsAtmospheric Chemistry and Physics1680-73161680-73242012-08-0112167413742710.5194/acp-12-7413-2012α-pinene photooxidation under controlled chemical conditions – Part 2: SOA yield and composition in low- and high-NO<sub>x</sub> environmentsP. O. WennbergJ. H. SeinfeldP. S. ChhabraM. ChanK. A. SchillingL. D. YeeN. C. EddingsaasC. L. LozaThe gas-phase oxidation of α-pinene produces a large amount of secondary organic aerosol (SOA) in the atmosphere. A number of carboxylic acids, organosulfates and nitrooxy organosulfates associated with α-pinene have been found in field samples and some are used as tracers of α-pinene oxidation. α-pinene reacts readily with OH and O<sub>3</sub> in the atmosphere followed by reactions with both HO<sub>2</sub> and NO. Due to the large number of potential reaction pathways, it can be difficult to determine what conditions lead to SOA. To better understand the SOA yield and chemical composition from low- and high-NO<sub>x</sub> OH oxidation of α-pinene, studies were conducted in the Caltech atmospheric chamber under controlled chemical conditions. Experiments used low O<sub>3</sub> concentrations to ensure that OH was the main oxidant and low α-pinene concentrations such that the peroxy radical (RO<sub>2</sub>) reacted primarily with either HO<sub>2</sub> under low-NO<sub>x</sub> conditions or NO under high-NO<sub>x</sub> conditions. SOA yield was suppressed under conditions of high-NO<sub>x</sub>. SOA yield under high-NO<sub>x</sub> conditions was greater when ammonium sulfate/sulfuric acid seed particles (highly acidic) were present prior to the onset of growth than when ammonium sulfate seed particles (mildly acidic) were present; this dependence was not observed under low-NO<sub>x</sub> conditions. When aerosol seed particles were introduced after OH oxidation, allowing for later generation species to be exposed to fresh inorganic seed particles, a number of low-NO<sub>x</sub> products partitioned to the highly acidic aerosol. This indicates that the effect of seed acidity and SOA yield might be under-estimated in traditional experiments where aerosol seed particles are introduced prior to oxidation. We also identify the presence of a number of carboxylic acids that are used as tracer compounds of α-pinene oxidation in the field as well as the formation of organosulfates and nitrooxy organosulfates. A number of the carboxylic acids were observed under all conditions, however, pinic and pinonic acid were only observed under low-NO<sub>x</sub> conditions. Evidence is provided for particle-phase sulfate esterification of multi-functional alcohols.http://www.atmos-chem-phys.net/12/7413/2012/acp-12-7413-2012.pdf |
| spellingShingle | P. O. Wennberg J. H. Seinfeld P. S. Chhabra M. Chan K. A. Schilling L. D. Yee N. C. Eddingsaas C. L. Loza α-pinene photooxidation under controlled chemical conditions – Part 2: SOA yield and composition in low- and high-NO<sub>x</sub> environments Atmospheric Chemistry and Physics |
| title | α-pinene photooxidation under controlled chemical conditions – Part 2: SOA yield and composition in low- and high-NO<sub>x</sub> environments |
| title_full | α-pinene photooxidation under controlled chemical conditions – Part 2: SOA yield and composition in low- and high-NO<sub>x</sub> environments |
| title_fullStr | α-pinene photooxidation under controlled chemical conditions – Part 2: SOA yield and composition in low- and high-NO<sub>x</sub> environments |
| title_full_unstemmed | α-pinene photooxidation under controlled chemical conditions – Part 2: SOA yield and composition in low- and high-NO<sub>x</sub> environments |
| title_short | α-pinene photooxidation under controlled chemical conditions – Part 2: SOA yield and composition in low- and high-NO<sub>x</sub> environments |
| title_sort | α pinene photooxidation under controlled chemical conditions ndash part 2 soa yield and composition in low and high no sub x sub environments |
| url | http://www.atmos-chem-phys.net/12/7413/2012/acp-12-7413-2012.pdf |
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