Abstract
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 that the signals of oligoesters comprise a major fraction (0.10–0.33) of the signals of the SOA products observed from all dienes investigated. The oligoesters originate from the unsaturated aldehyde gas phase diene reaction products; namely, semi-volatile compounds produced by the oxidation of the unsaturated aldehyde undergo particle-phase oligoester formation. Oligoesters produced by the dehydration reaction between nitrooxypolyol and 2-methylglyceric acid monomer or its oligomer were also characterized 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.
Highlights
Isoprene is the most abundant nonmethane hydrocarbon emitted into the atmosphere, mainly originating from biogenic sources (Guenther et al, 2006)
We experimentally investigate the formation of Secondary organic aerosol (SOA) from the photooxidation of conjugated dienes in the presence of NOx to improve our understanding of SOA formation from these reactions in urban air
The signals of the oligomers identified comprise a major fraction of the signals of the SOA products observed from all dienes investigated
Summary
Isoprene is the most abundant nonmethane hydrocarbon emitted into the atmosphere, mainly originating from biogenic sources (Guenther et al, 2006). SOA formation during isoprene oxidation has been investigated via laboratory studies by many researchers The products formed from isoprene photooxidation (i.e. 2-methyltetrols, C5-alkenetriols, and 2methylglyceric acid) have been observed in ambient fine particles (Claeys et al, 2004a,b, 2010; Wang et al, 2005; Xia and Hopke, 2006; Clements and Seinfeld, 2007; Fu et al, 2009, 2010a,b). K. Sato et al.: SOA formation from the photooxidation of dienes currently estimated to be the single largest source of SOA in the atmosphere (Henze and Seinfeld, 2006; Henze et al, 2008; Hallquist et al, 2009; Carlton et al, 2009)
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