EGU23-8905
https://doi.org/10.5194/egusphere-egu23-8905
EGU General Assembly 2023
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

Particle hygroscopicity in an urban background environment during the ACROSS campaign

Shravan Deshmukh1, Laurent Poulain1, Birgit Wehner1, Jean-Eudes Petit2, Pauline Fombelle2, Oliver Favez3, Hartmut Herrmann1, and Mira Pöhlker1
Shravan Deshmukh et al.
  • 1Leibniz-Institut für Troposphärenforschung e.V. (TROPOS), Permoserstraße 15, 04318 Leipzig, Germany (deshmukh@tropos.de)
  • 2Laboratoire des Sciences du Climat et de l’Environnement, CEA-CNRS-UVSQ, IPSL, Université Paris-Saclay, 91191 Gif-sur-Yvette, France
  • 3Institut national de l’environnement industriel et des risques (INERIS), Parc Techno. Alata, BP2, 60550 Verneuil-en-Halatte, France

Hygroscopicity strongly influences aerosol particle properties and multiphase chemistry, which also plays an essential role in several atmospheric processes. Although CCN (cloud condensation nuclei) properties are commonly measured, sub-saturation hygroscopicity measurements remain rare. Within the ACROSS campaign, which took place in the Paris region, France, during the summer of 2022, the particle’s hygroscopic growth at 90 % relative humidity (RH) and chemical composition were concurrently measured using a Hygroscopicity Tandem Differential Mobility Analyser (HTDMA, scanning at 100, 150, 200, and 250 nm) and Aerodyne High-Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS) respectively, at the ACTRIS (the European Aerosol, Clouds and Trace gases Research Infrastructure) SIRTA near facility, a peri-urban site representative of the Greater Paris background conditions. Growth factor probability density distributions (GF-PDF) show two distinct modes: hydrophobic and hygroscopic, indicating that the particles are internally and externally mixed. The hygroscopic mode is always more prominent in the GF-PDF, indicating a change in the particles' mixing state. The dominance of the hygroscopic mode becomes more pronounced with increasing particle size. The mean hygroscopicity parameter values, κ of 100, 150, 200, and 250 nm particles derived from hygroscopicity measurements are respectively 0.23, 0.29, 0.36, and 0.38 during the sampling period. The size dependence is reflected in the averaged values of κ and the GF distributions. A diurnal pattern was observed with an average daytime κ higher than during night-time, which could be linked to aging processes and secondary aerosol formation during the day. The Zdanovskii-Stokes-Robinson (ZSR) mixing rule was applied on the particle chemical to make accurate quantitative predictions of the mean GF of mixed atmospheric aerosol particles.

Keywords: Hygroscopicity, Growth factor, hygroscopicity parameter κ.

How to cite: Deshmukh, S., Poulain, L., Wehner, B., Petit, J.-E., Fombelle, P., Favez, O., Herrmann, H., and Pöhlker, M.: Particle hygroscopicity in an urban background environment during the ACROSS campaign, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-8905, https://doi.org/10.5194/egusphere-egu23-8905, 2023.