TY - JOUR
T1 - Oxygenated products formed from OH-initiated reactions of trimethylbenzene
T2 - Autoxidation and accretion
AU - Wang, Yuwei
AU - Mehra, Archit
AU - Krechmer, Jordan E.
AU - Yang, Gan
AU - Hu, Xiaoyu
AU - Lu, Yiqun
AU - Lambe, Andrew
AU - Canagaratna, Manjula
AU - Chen, Jianmin
AU - Worsnop, Douglas
AU - Coe, Hugh
AU - Wang, Lin
N1 - Funding Information:
Acknowledgements. Lin Wang acknowledges the Newton Advanced Fellowship (grant no. NA140106).
Publisher Copyright:
© 2020 Author(s).
PY - 2020/8/14
Y1 - 2020/8/14
N2 - Gas-phase oxidation pathways and products of anthropogenic volatile organic compounds (VOCs), mainly aromatics, are the subject of intensive research, with attention paid to their contributions to secondary organic aerosol (SOA) formation and potentially new particle formation (NPF) in the urban atmosphere. In this study, a series of OHinitiated oxidation experiments of trimethylbenzene (TMB, C9H12) including 1,2,4-TMB, 1,3,5-TMB, 1,2,3-TMB, and 1,2,4-(methyl-D3)-TMBs (C9H9D3) were investigated in an oxidation flow reactor (OFR) in the absence and presence of NOx. Products were measured using a suite of state-ofthe-art instruments, i.e. a nitrate-based chemical ionization-atmospheric pressure interface time-of-flight mass spectrometer (nitrate CI-APi-TOF), an iodide-adduct chemical ionization time-of-flight mass spectrometer (iodide CI-TOF) equipped with a Filter Inlet for Gases and AEROsols (FIGAERO), and a Vocus proton-transfer-reaction mass spectrometer (Vocus PTR). A large number of C9 products with 1-11 oxygen atoms and C18 products presumably formed from dimerization of C9 peroxy radicals were observed, hinting at the extensive existence of autoxidation and accretion reaction pathways in the OH-initiated oxidation reactions of TMBs. Oxidation products of 1,2,4-(methyl-D3)-TMBs with deuterium atoms in different methyl substituents were then used as a molecular basis to propose potential autoxidation reaction pathways. Accretion of C9 peroxy radicals is the most significant for aromatics with meta-substituents and the least for aromatics with ortho-substituents if the number and size of substituted groups are identical. The presence of NOx would suppress the formation of highly oxygenated molecules (HOMs) of C18 and enhance the formation of organonitrates and even dinitrate organic compounds. Our results show that the oxidation products of TMB are much more diverse and could be more oxygenated than the current mechanisms predict.
AB - Gas-phase oxidation pathways and products of anthropogenic volatile organic compounds (VOCs), mainly aromatics, are the subject of intensive research, with attention paid to their contributions to secondary organic aerosol (SOA) formation and potentially new particle formation (NPF) in the urban atmosphere. In this study, a series of OHinitiated oxidation experiments of trimethylbenzene (TMB, C9H12) including 1,2,4-TMB, 1,3,5-TMB, 1,2,3-TMB, and 1,2,4-(methyl-D3)-TMBs (C9H9D3) were investigated in an oxidation flow reactor (OFR) in the absence and presence of NOx. Products were measured using a suite of state-ofthe-art instruments, i.e. a nitrate-based chemical ionization-atmospheric pressure interface time-of-flight mass spectrometer (nitrate CI-APi-TOF), an iodide-adduct chemical ionization time-of-flight mass spectrometer (iodide CI-TOF) equipped with a Filter Inlet for Gases and AEROsols (FIGAERO), and a Vocus proton-transfer-reaction mass spectrometer (Vocus PTR). A large number of C9 products with 1-11 oxygen atoms and C18 products presumably formed from dimerization of C9 peroxy radicals were observed, hinting at the extensive existence of autoxidation and accretion reaction pathways in the OH-initiated oxidation reactions of TMBs. Oxidation products of 1,2,4-(methyl-D3)-TMBs with deuterium atoms in different methyl substituents were then used as a molecular basis to propose potential autoxidation reaction pathways. Accretion of C9 peroxy radicals is the most significant for aromatics with meta-substituents and the least for aromatics with ortho-substituents if the number and size of substituted groups are identical. The presence of NOx would suppress the formation of highly oxygenated molecules (HOMs) of C18 and enhance the formation of organonitrates and even dinitrate organic compounds. Our results show that the oxidation products of TMB are much more diverse and could be more oxygenated than the current mechanisms predict.
UR - http://www.scopus.com/inward/record.url?scp=85090297939&partnerID=8YFLogxK
U2 - 10.5194/acp-20-9563-2020
DO - 10.5194/acp-20-9563-2020
M3 - Article
AN - SCOPUS:85090297939
SN - 1680-7316
VL - 20
SP - 9563
EP - 9579
JO - Atmospheric Chemistry and Physics
JF - Atmospheric Chemistry and Physics
IS - 15
ER -