Molecular composition of organic aerosols in urban and marine atmosphere: A comparison study using FIGAERO-I-CIMS, ESI-FT-ICR MS, and GC × GC-EI-ToF-MS

We conducted a comparative study on chemical composition of organic aerosols (OA) collected in urban and marine atmosphere, respectively, using three mass spectrometers, Filter Inlet for Gases and Aerosol-Iodide-Chemical Ionization Mass Spectrometry (FIGAERO-I-CIMS), Electrospray Ionization-Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (ESI-FT-ICR MS), and Two-dimensional Gas Chromatograph-Electron Ionization-Mass Spectrometry (GC × GC-EI-ToF-MS). The FIGAERO-I-CIMS, ESI(–)-FT-ICR MS, and ESI(+)-FT-ICR MS showed preferred sensitivity to CHO, CHOS/CHONS, and CHON compounds, respectively. The compounds detected by the FIGAERO-I-CIMS were more oxidized and saturated than those detected by the ESI-FT-ICR MS. The GC × GC-EI-ToF-MS offered the advantage of detecting organonitrates, carbonyls, alkanes, oxy-PAHs, and amides in OA. Despite different MS technologies, some distinct features of organic compound distribution were observed between urban and marine OA. CHON compounds were more abundant in urban aerosols than marine aerosols. Organonitrates dominated over reduced-nitrogen organic compounds in all samples, and the relative importance of aromatic and aliphatic nitrates depended on MS technologies and sample type. The contribution of CHOS/CHONS compounds was high (25.1%–66.2%) in urban aerosols or marine aerosols being heavily influenced by continental sources. The most important CHOS/CHONS type in these samples were organosulfates of biogenic origin (49.4%–62.9%). Aromatics-like organosulfates contributed the least (9.1%–21.2%) to total intensity of CHOS/CHONS compounds. Considering high proportion (34.4%–62.8%) of aromatics-like compounds in OA, our result indicated that aromatic compounds were less prone to form organosulfates than aliphatic compounds. More Chlorine-containing compounds were found in clean urban atmosphere than polluted urban atmosphere. Most of Chlorine-containing compounds in urban aerosols were aliphatic, while those in marine aerosols were mostly aromatic. This study demonstrated the necessity of employing multiple MS technologies for a better characterization of chemical composition of complex organic aerosols.