Aerosol Chemistry Resolved by Mass Spectrometry: Linking Field Measurements of Cloud Condensation Nuclei Activity to Organic Aerosol Composition

Abstract

organics, nitrate, sulfate and ammonium. Inorganic sulfate measurements were achieved by 28 semi-online ion chromatography and were compared to the AMS total sulfate mass. We found 29 that up to 40% of the total sulfate mass fraction can be covalently bonded to organic molecules. 30 This finding is supported by both on-and off-line soft ionization techniques, which confirmed 31 the presence of several organosulfates and nitrooxy-organosulfates in the particle phase. The 32 chemical composition analysis was compared to hygroscopicity measurements derived from a 33 cloud condensation nuclei counter. We observed that the hygroscopicity parameter (κ) that is 34 derived from organic mass fractions determined by AMS measurements may overestimate the 35 observed κ up to 0.2, if high a fraction of sulfate is bonded to organic molecules and little 36 photochemical aging is exhibited.

Long-term cloud condensation nuclei number concentration, particle number size distribution and chemical composition measurements at regionally representative observatories

“…Note that especially for the European sites, it might be possible that a considerable fraction of nitrate is present in the form of organic nitrate (Kiendler-Scharr et al, 2016), which is likely to influence the hygroscopicity. Similarly, particulate sulfate can be present as organosulfate (Vogel et al, 2016) in which case particle hygroscopicity would be overestimated. At all other stations, organics can play a more important role in terms of mass contribution (up to 80 % at SMR, ATTO and JFJ, and up to 40 % at MHD and FIK) and determination of the κ value.…”

Chemical Characteristics of Organic Aerosols in Shanghai: A Study by Ultrahigh‐Performance Liquid Chromatography Coupled With Orbitrap Mass Spectrometry

“…Recently, ESI‐UHRMS has been combined with LC in a number of studies (Lin et al, ; Vogel et al, ; Vogel et al, ; Wang et al, ), which allows separation of isomers and, hence, offers an additional dimension of information in comparison with previous studies using solely direct injection ESI‐UHRMS. Another advantage of LC separation is to reduce ion suppression during ionization and to achieve semiquantification of organic compounds.…”

The sensitivity of PM<sub>2.5</sub> acidity to meteorological parameters and chemical composition changes: 10-year records from six Canadian monitoring sites

“…In Simcoe, Windsor and St Anicet, the sites with lower NHx:sulfate molar ratios, wintertime pH values all exhibited significant variations. Under these conditions, not only the uncertainty in the SNA concentration measurements, but also the potential contributions from organic matter such as organic ammonium salts (Schlag et al, 2017;Tao and Murphy, 2018) or organosulfates (Vogel et al, 2016;Glasius et al, 2018), which current thermodynamic 5 models do not fully consider, can contribute to uncertainty in aerosol pH calculation. These conceptual modelling results also provide insight into the challenges posed in the direct measurement of aerosol pH off-line as it is both strongly impacted by ambient environmental conditions and the NH3 concentration equilibrated with the particle phase.…”