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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. Copyright © 2024 American Association for Aerosol Research [ABSTRACT FROM AUTHOR]

Aerosol particles in the atmosphere undergo heterogeneous transformations due to interactions with various gas-phase oxidants such as ozone. While it is known that these reactions are significantly affected by the phase state of the particle, a direct comparison between the reaction kinetics and product distributions for the same reactive process occurring in the different phases remains elusive. This study uses single particle levitation and flow-tube methods to measure and compare the ozonolysis of particles containing oleic acid and its trans isomer elaidic acid in liquid, supercooled liquid, and solid states. We measure their evolving size, optical properties, phase, and chemical composition during reaction. Both primary reactions and secondary chemistry were explored, along with the influence of particle phase state on reaction kinetics and product formation. Notably, we directly compare the reaction kinetics of supercooled liquid elaidic acid particles with liquid oleic acid particles, revealing similar uptake coefficients indicative of similar inherent reactivity of the C = C moiety. We go on to compare the kinetics of solid elaidic acid particles, formed due to solidification at room temperature and freezing at low temperature. We found a significant slowing in reaction kinetics that may be attributed to the phase of the particle and the influence of slowed molecular diffusion, supported by qualitative agreement with a multilayer kinetic model (KM-SUB). We further explore differences in the product distributions between particles exhibiting different phase states. These results provide important insights into how the chemical aging of ambient aerosol particles may be influenced by their physicochemical characteristics. [ABSTRACT FROM AUTHOR]