Molecular speciation of secondary organic aerosol from photooxidation of the higher alkenes: 1-octene and 1-decene

Abstract

Outdoor smog chamber photooxidations to determine the molecular composition of secondary organic aerosol (SOA) from 1-octene and 1-decene in sunlight-irradiated hydrocarbon-NO_x mixtures are reported. The observed products are consistent with the current understanding of alkene reactions with OH and O₃. Gas-phase mechanisms leading to the observed products are outlined. Heptanal, heptanoic acid, and dihydro-5-propyl-2(3H)-furanone were the dominant organics identified in 1-octene aerosol. The corresponding species in 1-decene aerosol were nonanal, nonanoic acid, and dihydro-5-pentyl-2(3H)-furanone. Measured aerosol yields from 1-octene and 1-decene experiments are also reported, and are found to correlate with organic mass concentration according to semi-volatile gas/particle partitioning theory. A new organic aerosol extraction procedure utilizing supercritical CO₂ extraction is outlined.

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