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Abstract
Abstract. Secondary organic aerosol (SOA) was generated by irradiating 1,3-butadiene (13BD) in the presence of H2O2 or NOx. Experiments were conducted in a smog chamber operated in either flow or batch mode. A filter/denuder sampling system was used for simultaneously collecting gas- and particle-phase products. The chemical composition of the gas phase and SOA was analyzed using derivative-based methods (BSTFA, BSTFA + PFBHA, or DNPH) followed by gas chromatography–mass spectrometry (GC–MS) or high-performance liquid chromatography (HPLC) analysis of the derivative compounds. The analysis showed the occurrence of more than 60 oxygenated organic compounds in the gas and particle phases, of which 31 organic monomers were tentatively identified. The major identified products include glyceric acid, d-threitol, erythritol, d-threonic acid, meso-threonic acid, erythrose, malic acid, tartaric acid, and carbonyls including glycolaldehyde, glyoxal, acrolein, malonaldehyde, glyceraldehyde, and peroxyacryloyl nitrate (APAN). Some of these were detected in ambient PM2.5 samples, and could potentially serve as organic markers of 13BD. Furthermore, a series of oligoesters were detected and found to be produced through chemical reactions occurring in the aerosol phase between compounds bearing alcoholic groups and compounds bearing acidic groups. SOA was analyzed for organic mass to organic carbon (OM /OC) ratio, effective enthalpy of vaporization (Δ Hvapeff), and aerosol yield. The average OM /OC ratio and SOA density were 2.7 ± 0.09 and 1.2 ± 0.05, respectively. The average Δ Hvapeff was −26.08 ± 1.46 kJ mol−1, a value lower than that of isoprene SOA. The average laboratory SOA yield measured in this study at aerosol mass concentrations between 22.5 and 140.2 μg m−3 was 0.025 ± 0.011, a value consistent with the literature (0.021–0.178). While the focus of this study has been examination of the particle-phase measurements, the gas-phase photooxidation products have also been examined. The contribution of SOA products from 13BD oxidation to ambient PM2.5 was investigated by analyzing a series of ambient PM2.5 samples collected in several locations around the United States. In addition to the occurrence of several organic compounds in field and laboratory samples, glyceric acid, d-threitol, erythritol, erythrose, and threonic acid were found to originate only from the oxidation of 13BD based on our previous experiments involving chamber oxidation of a series of hydrocarbons. Initial attempts have been made to quantify the concentrations of these compounds. The average concentrations of these compounds in ambient PM2.5 samples from the California Research at the Nexus of Air Quality and Climate Change (CalNex) study ranged from 0 to approximately 14.1 ng m−3. The occurrence of several other compounds in both laboratory and field samples suggests that SOA originating from 13BD oxidation could contribute to the ambient aerosol mainly in areas with high 13BD emission rates.
Highlights
Atmospheric organic carbon (OC) from anthropogenic sources forms a large portion of urban ambient organic aerosol
A comparison of mass spectra from the actions involving reactions of organic acid and alcohol un- laboratory sample with those measured at the field site is der atmospheric conditions are too slow to occur, and cannot shown in Fig. 8 for glyceric acid, d-threitol, erythrose, and account for all the oligoesters observed in chamber exper- threonic acid
The chemical composition of the gas phase and secondary organic aerosol (SOA) was analyzed using derivative-based methods followed by gas chromatography– mass spectrometry or high-performance liquid chromatography analysis of the derivative compounds
Summary
Atmospheric organic carbon (OC) from anthropogenic sources forms a large portion of urban ambient organic aerosol. A series of biogenic and anthropogenic conjugated dienes with five or fewer carbon atoms (e.g., isoprene, 1,3butadiene [13BD], 2-methyl-3-butene-2-ol) have been shown to contribute to SOA formation (Claeys et al, 2004; Edney et al, 2005; Kroll et al, 2006; Surratt et al, 2006, 2010; Sato et al, 2011; Jaoui et al, 2012; Zhang et al, 2012, 2014; Angove et al, 2006). Given the presence of threitol, erythritol, and glyceric acid in forest areas and the high emission of 13BD (a possible precursor to these compounds) in rural areas, it is crucial to assess the extent to which we understand SOA formation from the oxidation of 13BD. Based on the analysis of field and laboratory samples, the tracer method reported by Kleindienst et al (2007) was used to estimate the contribution of 13BD to organic aerosol in ambient air
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