Atmos. Chem. Phys. Discuss., 11, 4313-4354, 2011
© Author(s) 2011. This work is distributed
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This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
Secondary organic aerosol formation from the photooxidation of isoprene, 1,3-butadiene, and 2,3-dimethyl-1,3-butadiene under high NOx conditions
K. Sato1,2, S. Nakao1,3, C. H. Clark1,3, L. Qi1,3, and D. R. Cocker III1,3
1Bourns College of Engineering – Center for Environmental Research & Technology, University of California, Riverside, 1084 Columbia Ave., Riverside, CA 92507, USA
2Asian Environment Research Group, National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, Ibaraki 305-8506, Japan
3Department of Chemical and Environmental Engineering, University of California, Riverside, CA 92521, USA

Abstract. Secondary organic aerosol (SOA) formation from atmospheric oxidation of isoprene has been the subject of multiple studies in recent years; however, reactions of other conjugated dienes emitted from anthropogenic sources remain poorly understood. SOA formation from the photooxidation of isoprene, isoprene-1-13C, 1,3-butadiene, and 2,3-dimethyl-1,3-butadiene is investigated for high NOx conditions. The SOA yield measured in the 1,3-butadiene/NOx/H2O2 irradiation system (0.089–0.178) was close to or slightly higher than that measured with isoprene under similar NOx conditions (0.077–0.103), suggesting that the photooxidation of 1,3-butadiene is a possible source of SOA in urban air. In contrast, a very small amount of SOA particles was produced in experiments with 2,3-dimethyl-1,3-butadiene. Off-line liquid chromatography – mass spectrometry analysis revealed oligoesters as the major SOA products observed from all dienes investigated. The oligoesters originate from the unsaturated aldehyde gas-phase diene reaction products, which undergo oligoester formation through heterogeneous oxidation under high NOx conditions. Oligoesters produced by the dehydration reaction between nitrooxypolyol and 2-methylglyceric acid monomer or its oligomer were also discovered in these experiments with isoprene as the starting diene. These oligomers are possible sources of the 2-methyltetrols found in ambient aerosol samples collected under high NOx conditions. Furthermore, in low-temperature experiments also conducted in this study, the SOA yield measured with isoprene at 278 K was 2–3 times as high as that measured at 300 K under similar concentration conditions. Although oligomerization plays an important role in SOA formation from isoprene photooxidation, the observed temperature dependence of SOA yield is largely explained by gas/particle partitioning of semi-volatile compounds.

Citation: Sato, K., Nakao, S., Clark, C. H., Qi, L., and Cocker III, D. R.: Secondary organic aerosol formation from the photooxidation of isoprene, 1,3-butadiene, and 2,3-dimethyl-1,3-butadiene under high NOx conditions, Atmos. Chem. Phys. Discuss., 11, 4313-4354, doi:10.5194/acpd-11-4313-2011, 2011.
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