Preprints
https://doi.org/10.5194/acp-2021-251
https://doi.org/10.5194/acp-2021-251

  06 Apr 2021

06 Apr 2021

Review status: this preprint is currently under review for the journal ACP.

Modelling the gas–particle partitioning and water uptake of isoprene-derived secondary organic aerosol at high and low relative humidity

Dalrin Ampritta Amaladhasan1, Claudia Heyn2, Christopher R. Hoyle2,3, Imad El Haddad2,3, Miriam Elser2,5, Simone M. Pieber2,6, Jay G. Slowik2, Antonio Amorim7, Jonathan Duplissy8,9, Sebastian Ehrhart4,10, Vladimir Makhmutov11, Ugo Molteni2, Matti Rissanen12, Yuri Stozhkov11, Robert Wagner8, Armin Hansel13, Jasper Kirkby4,14, Neil M. Donahue15, Rainer Volkamer16, Urs Baltensperger2, Martin Gysel-Beer2, and Andreas Zuend1 Dalrin Ampritta Amaladhasan et al.
  • 1Department of Atmospheric and Oceanic Sciences, McGill University, Montreal, Quebec, H3A 0B9, Canada
  • 2Laboratory of Atmospheric Chemistry, Paul Scherrer Institute, 5232 Villigen PSI, Switzerland
  • 3Institute for Atmospheric and Climate Science, ETH Zurich, 8092 Zurich, Switzerland
  • 4CERN, 1211 Geneva, Switzerland
  • 5Swiss Federal Laboratories for Materials Science and Technology, Automotive Powertrain Technologies, Dübendorf, Switzerland
  • 6Empa, Laboratory for Air Pollution / Environmental Technology, Ueberlandstrasse 129, CH-8600 Dübendorf, Switzerland
  • 7CENTRA and Faculdade de Ciencias, University of Lisbon, 1749-016 Lisbon, Portugal
  • 8Institute for Atmospheric and Earth System Research (INAR)/Physics, University of Helsinki, 00014 Helsinki, Finland
  • 9Helsinki Institute of Physics, University of Helsinki, 00014 Helsinki, Finland
  • 10Finnish Environment Institute (SYKE), Marine Research Centre, 00790, Helsinki, Finland
  • 11P.N. Lebedev Physical Institute of the Russian Academy of Sciences, 119991 Moscow, Russian Federation
  • 12Aerosol Physics Laboratory, Physics Unit, Tampere University, Tampere, Finland
  • 13Department of Ion Physics and Applied Physics, University of Innsbruck, 6020 Innsbruck, Austria
  • 14Institute for Atmospheric and Environmental Sciences, Goethe University Frankfurt, 60438 Frankfurt am Main, Germany
  • 15Center for Atmospheric Particle Studies, Carnegie Mellon University, Pittsburgh, PA 15213, USA
  • 16Department of Chemistry & CIRES, University of Colorado at Boulder, Boulder, CO 80305 USA

Abstract. This study presents a characterization of the hygroscopic growth behaviour and effects of different inorganic seed particles on the formation of secondary organic aerosols (SOA) from the dark ozone-initiated oxidation of isoprene at low NOx conditions. We performed simulations of isoprene oxidation using a gas-phase chemical reaction mechanism based on the Master Chemical Mechanism (MCM) in combination with an equilibrium gas–particle partitioning model to predict the SOA concentration. The equilibrium model accounts for non-ideal mixing in liquid phases, including liquid–liquid phase separation (LLPS), and is based on the AIOMFAC model for mixture non-ideality and the EVAPORATION model for pure compound vapour pressures. Measurements from the Cosmics Leaving Outdoor Droplets (CLOUD) chamber experiments conducted at the European Organization for Nuclear Research (CERN) for isoprene ozonolysis cases, were used to aid in parameterizing the SOA yields at different atmospherically relevant temperatures, relative humidity (RH) and reacted isoprene concentrations. To represent the isoprene ozonolysis-derived SOA, a selection of organic surrogate species is introduced in the coupled modelling system. The model predicts a single, homogeneously mixed particle phase at all relative humidity levels for SOA formation in the absence of any inorganic seed particles. In the presence of aqueous sulfuric acid or ammonium bisulfate seed particles, the model predicts LLPS to occur below ~80 % RH, where the particles consist of an inorganic-rich liquid phase and an organic-rich liquid phase; however, with significant amounts of bisulfate and water partitioned to the organic-rich phase. The measurements show an enhancement in the SOA amounts at 85 % RH compared to 35 % RH for both the seed-free and seeded cases. The model predictions of RH-dependent SOA yield enhancements at 85 % RH vs. 35 % RH are 1.80 for a seed-free case, 1.52 for the case with ammonium bisulfate seed and 1.06 for the case with sulfuric acid seed. Predicted SOA yields are enhanced in the presence of an aqueous inorganic seed, regardless of the seed type (ammonium sulfate, ammonium bisulfate or sulfuric acid) in comparison with seed-free conditions at the same RH level. We discuss the comparison of model-predicted SOA yields with a selection of other laboratory studies on isoprene SOA formation conducted at different temperatures and for a variety of reacted isoprene concentrations.

Dalrin Ampritta Amaladhasan et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2021-251', Anonymous Referee #1, 11 May 2021
  • RC2: 'Comment on acp-2021-251', Anonymous Referee #2, 18 May 2021

Dalrin Ampritta Amaladhasan et al.

Dalrin Ampritta Amaladhasan et al.

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Short summary
We employ a combination of models for gas-phase chemical reactions and equilibrium gas-particle partitioning of isoprene-derived secondary organic aerosols (SOA) informed by dark ozonolysis experiments conducted in the CLOUD chamber. Our predictions cover high to low relative humidities (RH) and quantify how SOA mass yields are enhanced at high RH as well as the impact of inorganic seeds of distinct hygroscopicities and acidities on the coupled partitioning of water and semivolatile organics.
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