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Atmos Chem Phys

Title:		Mechanistic study of the formation of ring-retaining and ring-opening products from the oxidation of aromatic compounds under urban atmospheric conditions
Author(s):		Zaytsev A; Koss AR; Breitenlechner M; Krechmer JE; Nihill KJ; Lim CY; Rowe JC; Cox JL; Moss J; Roscioli JR; Canagaratna MR; Worsnop DR; Kroll JH; Keutsch FN;
Address:		"John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA02138, USA. Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, MA02139, USA. now at: TOFWERK USA, Boulder, CO80301, USA. Aerodyne Research Inc., Billerica, MA01821, USA. Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA02138, USA. Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA02138, USA"
Journal Title:		Atmos Chem Phys
Year:		2019
Volume:		20191213
Issue:		23
Page Number:		15117 - 15129
DOI:		10.5194/acp-19-15117-2019
ISSN/ISBN:		1680-7316 (Print) 1680-7324 (Electronic) 1680-7316 (Linking)
Abstract:		"Aromatic hydrocarbons make up a large fraction of anthropogenic volatile organic compounds and contribute significantly to the production of tropospheric ozone and secondary organic aerosol (SOA). Four toluene and four 1,2,4-trimethylbenzene (1,2,4-TMB) photooxidation experiments were performed in an environmental chamber under relevant polluted conditions (NO (x) ~ 10ppb). An extensive suite of instrumentation including two proton-transfer-reaction mass spectrometers (PTR-MS) and two chemical ionisation mass spectrometers ( NH4+ CIMS and I(-) CIMS) allowed for quantification of reactive carbon in multiple generations of hydroxyl radical (OH)-initiated oxidation. Oxidation of both species produces ring-retaining products such as cresols, benzaldehydes, and bicyclic intermediate compounds, as well as ring-scission products such as epoxides and dicarbonyls. We show that the oxidation of bicyclic intermediate products leads to the formation of compounds with high oxygen content (an O : C ratio of up to 1.1). These compounds, previously identified as highly oxygenated molecules (HOMs), are produced by more than one pathway with differing numbers of reaction steps with OH, including both auto-oxidation and phenolic pathways. We report the elemental composition of these compounds formed under relevant urban high-NO conditions. We show that ring-retaining products for these two precursors are more diverse and abundant than predicted by current mechanisms. We present the speciated elemental composition of SOA for both precursors and confirm that highly oxygenated products make up a significant fraction of SOA. Ring-scission products are also detected in both the gas and particle phases, and their yields and speciation generally agree with the kinetic model prediction"
Keywords:
Notes:		"PubMed-not-MEDLINEZaytsev, Alexander Koss, Abigail R Breitenlechner, Martin Krechmer, Jordan E Nihill, Kevin J Lim, Christopher Y Rowe, James C Cox, Joshua L Moss, Joshua Roscioli, Joseph R Canagaratna, Manjula R Worsnop, Douglas R Kroll, Jesse H Keutsch, Frank N eng P42 ES027707/ES/NIEHS NIH HHS/ T32 ES007020/ES/NIEHS NIH HHS/ Germany 2019/01/01 Atmos Chem Phys. 2019; 19(23):15117-15129. doi: 10.5194/acp-19-15117-2019. Epub 2019 Dec 13"