Fig. 2: Chemical composition and temporal variability of the six secondary organic aerosol categories.
From: Substantial contribution of transported emissions to organic aerosol in Beijing
Kendrick mass defect spectra show the characteristics of different sources, with near-molecular composition and relative intensity indicated by symbol colour and size, as shown in the legend (mass relative to m(CH2) = 14; only compounds with an intensity of at least 10% of maximum compound intensity). The seasonal variation is shown as daily mean concentrations and the diurnal variation as median diel cycles. Solid-fuel as well as daytime aromatic-dominated and biogenic sources are principally CxHyOz oxidized organics. Wintertime solid-fuel SOA has prominent lignin and cellulose-like constituents, C6H10O5 and C7H10O5. Daytime aromatic-dominated SOA has products consistent with trimethylbenzene laboratory SOA (grey lines)23. Daytime biogenic SOA has constituents consistent with α-pinene laboratory SOA (grey lines)14. Nocturnal categories feature prominent nitrogen-containing species (CxHyOzNr), consistent with NO3 radical oxidation. Aqueous SOA is clearly enhanced in the presence of high aerosol liquid water content (LWC), linking its formation to aqueous-phase processes. Night-time biogenic SOA has products consistent with d-limonene + NO3 laboratory SOA (grey lines)20.
