Preprints
https://doi.org/10.5194/egusphere-2024-3027
https://doi.org/10.5194/egusphere-2024-3027
09 Oct 2024
 | 09 Oct 2024

External particle mixing influences hygroscopicity in a sub-urban area

Shravan Deshmukh, Laurent Poulain, Birgit Wehner, Silvia Henning, Jean-Eudes Petit, Pauline Fombelle, Olivier Favez, Hartmut Herrmann, and Mira Pöhlker

Abstract. Hygroscopicity strongly influences aerosol properties and multiphase chemistry, which is essential in several atmospheric processes. Although CCN (cloud condensation nuclei) properties are commonly measured, sub-saturated hygroscopicity measurements remain rare. During the ACROSS campaign (Atmospheric ChemistRy Of the Suburban foreSt, in Paris, Summer 2022), the particle’s hygroscopic growth at 90 % relative humidity (RH) and chemical composition were measured at the sub-urban site using a Hygroscopicity Tandem Differential Mobility Analyser (HTDMA, scanning at 100, 150, 200, and 250 nm) and an Aerodyne High-Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS). Growth factor probability density functions (GF-PDFs) revealed two distinct modes—hydrophobic and hygroscopic—suggesting a combination of internal and external particle mixing with the split at GF 1.2. The prevalence of the hygroscopic mode increased with particle size, with mean hygroscopicity (κ) values of 0.23 and 0.38 for 100 and 200 nm particles, respectively. Using the Zdanovskii-Stokes-Robinson (ZSR) mixing rule, the agreement between measured and chemically derived hygroscopicity was approximately 51 % for 100 nm particles, which declined for 200 and 250 nm. These emphasise the large effect of external particle mixing and its influence on predicting hygroscopicity. The ZSR approach proves unreliable in predicting the wide growth distribution of externally mixed particles. In this measurement, 80–90 % of the particles were externally mixed and influenced by fresh emission, which affected the hygroscopicity prediction by a factor of 2. A cluster analysis based on backward trajectories and meteorological conditions gives valuable insights into the chemical composition and variations in the hygroscopicity of different air masses.

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Journal article(s) based on this preprint

21 Jan 2025
External particle mixing influences hygroscopicity in a sub-urban area
Shravan Deshmukh, Laurent Poulain, Birgit Wehner, Silvia Henning, Jean-Eudes Petit, Pauline Fombelle, Olivier Favez, Hartmut Herrmann, and Mira Pöhlker
Atmos. Chem. Phys., 25, 741–758, https://doi.org/10.5194/acp-25-741-2025,https://doi.org/10.5194/acp-25-741-2025, 2025
Short summary
Shravan Deshmukh, Laurent Poulain, Birgit Wehner, Silvia Henning, Jean-Eudes Petit, Pauline Fombelle, Olivier Favez, Hartmut Herrmann, and Mira Pöhlker

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2024-3027', Anonymous Referee #1, 07 Nov 2024
  • RC2: 'Comment on egusphere-2024-3027', Anonymous Referee #2, 11 Nov 2024
  • AC1: 'Comment on egusphere-2024-3027', Shravan Deshmukh, 22 Nov 2024

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2024-3027', Anonymous Referee #1, 07 Nov 2024
  • RC2: 'Comment on egusphere-2024-3027', Anonymous Referee #2, 11 Nov 2024
  • AC1: 'Comment on egusphere-2024-3027', Shravan Deshmukh, 22 Nov 2024

Peer review completion

AR: Author's response | RR: Referee report | ED: Editor decision | EF: Editorial file upload
AR by Shravan Deshmukh on behalf of the Authors (22 Nov 2024)  Author's response   Author's tracked changes   Manuscript 
ED: Publish as is (22 Nov 2024) by Ann Fridlind
AR by Shravan Deshmukh on behalf of the Authors (26 Nov 2024)  Manuscript 

Journal article(s) based on this preprint

21 Jan 2025
External particle mixing influences hygroscopicity in a sub-urban area
Shravan Deshmukh, Laurent Poulain, Birgit Wehner, Silvia Henning, Jean-Eudes Petit, Pauline Fombelle, Olivier Favez, Hartmut Herrmann, and Mira Pöhlker
Atmos. Chem. Phys., 25, 741–758, https://doi.org/10.5194/acp-25-741-2025,https://doi.org/10.5194/acp-25-741-2025, 2025
Short summary
Shravan Deshmukh, Laurent Poulain, Birgit Wehner, Silvia Henning, Jean-Eudes Petit, Pauline Fombelle, Olivier Favez, Hartmut Herrmann, and Mira Pöhlker
Shravan Deshmukh, Laurent Poulain, Birgit Wehner, Silvia Henning, Jean-Eudes Petit, Pauline Fombelle, Olivier Favez, Hartmut Herrmann, and Mira Pöhlker

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Short summary
Aerosol hygroscopicity has been investigated at the sub-urban site in Paris; analysis shows the sub-saturated regime's measured hygroscopicity and the chemically derived hygroscopic growth, shedding light on the large effect of external particle mixing and its influence on predicting hygroscopicity.
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