Comparison of secondary organic aerosol (SOA) formation during o-, m-, and p-xylene photooxidation. (February 2019)

• Record Type: Journal Article
• Authors: Zhang, Peng; Huang, Jingyun; Shu, Jinian; Yang, Bo
• Is Part Of: Environmental pollution. Volume 245(2019)
• Page Start: 20
• Page End: 28
• Publication Date: 2019-02
• Subjects: Xylene -- Secondary organic aerosol -- Photooxidation -- Chemical composition -- Methyl substitute; Pollution -- Periodicals; Pollution -- Environmental aspects -- Periodicals; Environmental Pollution -- Periodicals; Pollution -- Périodiques; Pollution -- Aspect de l'environnement -- Périodiques; Pollution -- Effets physiologiques -- Périodiques; Pollution; Pollution -- Environmental aspects; Periodicals; Electronic journals; 363.73
• DOI: 10.1016/j.envpol.2018.10.118
• Languages: English
• ISSNs: 0269-7491

Abstract

Abstract: Despite extensive effort to characterize xylene-isomer-derived secondary organic aerosols (SOAs) over the past decade, differences in SOA composition among xylene isomers, and their relative contributions to SOA formation remain poorly understood. Herein, we reinvestigated the photooxidation of o -, m -, and p -xylene under two limiting NO conditions. Dicarbonyls, TBM (the acronym of C3 -trione, 2, 3-butanedione, and 3-methyl-2-oxiranecarbaldehyde with the same [M+H] + m/z value of 87), and highly oxidized species (HOS), based on the m/z 61 fragment, were determined to be the predominant SOA components arising from xylene photooxidation; however, their relative contributions to SOA formation appear to depend on the xylene substitution pattern. In the initial stages of the reaction, dicarbonyls present in the SOA from m - and p -xylene, and TBM in the SOA from o -xylene, were the main contributors to new particle formation (NPF). Based on their significant levels of formation, HOS and TBM were characterized to be critical components that enhance SOA growth. High NO levels were noted to inhibit the formation of C3 -trione and 2, 3-butanedione in the SOA from m - and o -xylene, whereas the formation of 3-methyl-2-oxiranecarbaldehyde during p -xylene photooxidation was significantly promoted. These results reveal that the substitution pattern of the xylene isomer is a significant factor that determines these differences. In addition, decreases in the levels of dicarbonyls and TBM during NPF and the formation of HOS in the presence of high levels of NO may be important factors that lead to lower SOA yields compared to those obtained under low-NO conditions. This work contributes to a better understanding of the formation mechanism of xylene-derived SOAs. Graphical abstract: Highlights: The composition of xylene-derived secondary organic aerosols (SOAs) was reevaluated. SOA in the high-NO and free-NO photooxidation were compared. The alkyl substitute position in xylene significantly affects SOA formation. The effects of NO to products during SOA growth were different for three xylene isomers. Our results improved the understanding of the formation mechanism of xylene SOAs.