Impact of molecular structure on secondary organic aerosol formation from aromatic hydrocarbon photooxidation under low-NO<sub><i>x</i></sub> conditions
The molecular structure of volatile organic compounds determines their oxidation pathway, directly impacting secondary organic aerosol (SOA) formation. This study comprehensively investigates the impact of molecular structure on SOA formation from the photooxidation of 12 different eight- to nin...
| Main Authors: | , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2016-08-01
|
| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://www.atmos-chem-phys.net/16/10793/2016/acp-16-10793-2016.pdf |
| Summary: | The molecular structure of volatile organic compounds determines their
oxidation pathway, directly impacting secondary organic aerosol (SOA)
formation. This study comprehensively investigates the impact of molecular
structure on SOA formation from the photooxidation of 12 different eight-
to nine-carbon aromatic hydrocarbons under low-NO<sub><i>x</i></sub> conditions. The
effects of the alkyl substitute number, location, carbon chain length and
branching structure on the photooxidation of aromatic hydrocarbons are
demonstrated by analyzing SOA yield, chemical composition and physical
properties. Aromatic hydrocarbons, categorized into five groups, show a yield
order of ortho (<i>o</i>-xylene and <i>o</i>-ethyltoluene) > one substitute
(ethylbenzene, propylbenzene and isopropylbenzene) > meta
(<i>m</i>-xylene and <i>m</i>-ethyltoluene) > three substitute
(trimethylbenzenes) > para (<i>p</i>-xylene and <i>p</i>-ethyltoluene). SOA
yields of aromatic hydrocarbon photooxidation do not monotonically decrease
when increasing alkyl substitute number. The ortho position promotes SOA
formation while the para position suppresses aromatic oxidation and SOA
formation. Observed SOA chemical composition and volatility confirm that
higher yield is associated with further oxidation. SOA chemical composition
also suggests that aromatic oxidation increases with increasing alkyl
substitute chain length and branching structure. Further, carbon dilution
conjecture developed by Li et al. (2016) is extended in this study to serve
as a standard method to determine the extent of oxidation of an alkyl-substituted aromatic hydrocarbon. |
|---|---|
| ISSN: | 1680-7316 1680-7324 |