Articles | Volume 19, issue 10
https://doi.org/10.5194/gmd-19-4601-2026
© Author(s) 2026. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/gmd-19-4601-2026
© Author(s) 2026. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Model description paper
| 
28 May 2026
Model description paper |
| 28 May 2026
| 28 May 2026
S2AS v1.0 and 2D polarity–volatility lumping framework v1.0: automated compound classification and scalable lumping for organic aerosol modelling
Dalrin Ampritta Amaladhasan
Department of Atmospheric and Oceanic Sciences, McGill University, Montreal, Quebec, H3A 0B9, Canada
Dan Hassan-Barthaux
Department of Atmospheric and Oceanic Sciences, McGill University, Montreal, Quebec, H3A 0B9, Canada
Department of Atmospheric and Oceanic Sciences, McGill University, Montreal, Quebec, H3A 0B9, Canada
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Camilo Serrano Damha, Kyle Gorkowski, and Andreas Zuend
Atmos. Chem. Phys., 25, 5773–5792, https://doi.org/10.5194/acp-25-5773-2025, https://doi.org/10.5194/acp-25-5773-2025, 2025
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We implemented the BAT-VBS (Binary Activity Thermodynamics volatility basis set) aerosol thermodynamics model in the GEOS-Chem chemical transport model to efficiently account for organic aerosol water uptake, nonideal mixing, and impacts on the gas–particle partitioning of semi-volatile organics. Compared to GEOS-Chem's complex (dry) scheme, we show that the BAT-VBS model can predict substantial enhancements in organic aerosol mass concentration at moderate-to-high relative humidity.
Ryan Schmedding and Andreas Zuend
Atmos. Chem. Phys., 25, 327–346, https://doi.org/10.5194/acp-25-327-2025, https://doi.org/10.5194/acp-25-327-2025, 2025
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Four different approaches for computing the interfacial tension between liquid phases in aerosol particles were tested for particles with diameters from 10 nm to more than 5 μm. Antonov's rule led to the strongest reductions in the onset relative humidity of liquid–liquid phase separation and reproduced measured interfacial tensions for highly immiscible systems. A modified form of the Butler equation was able to best reproduce measured interfacial tensions in more miscible systems.
Liviana K. Klein, Allan K. Bertram, Andreas Zuend, Florence Gregson, and Ulrich K. Krieger
Atmos. Chem. Phys., 24, 13341–13359, https://doi.org/10.5194/acp-24-13341-2024, https://doi.org/10.5194/acp-24-13341-2024, 2024
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The viscosity of ammonium nitrate–sucrose–H2O was quantified with three methods ranging from liquid to solid state depending on the relative humidity. Moreover, the corresponding estimated internal aerosol mixing times remained below 1 h for most tropospheric conditions, making equilibrium partitioning a reasonable assumption.
Ryan Schmedding and Andreas Zuend
Atmos. Chem. Phys., 23, 7741–7765, https://doi.org/10.5194/acp-23-7741-2023, https://doi.org/10.5194/acp-23-7741-2023, 2023
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Aerosol particles below 100 nm in diameter have high surface-area-to-volume ratios. The enrichment of compounds in the surface of an aerosol particle may lead to depletion of that species in the interior bulk of the particle. We present a framework for modeling the equilibrium bulk–surface partitioning of mixed organic–inorganic particles, including cases of co-condensation of semivolatile organic compounds and species with extremely limited solubility in the bulk or surface of a particle.
Rani Jeong, Joseph Lilek, Andreas Zuend, Rongshuang Xu, Man Nin Chan, Dohyun Kim, Hi Gyu Moon, and Mijung Song
Atmos. Chem. Phys., 22, 8805–8817, https://doi.org/10.5194/acp-22-8805-2022, https://doi.org/10.5194/acp-22-8805-2022, 2022
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In this study, the viscosities of particles of sucrose–H2O, AS–H2O, and sucrose–AS–H2O for OIRs of 4:1, 1:1, and 1:4 for decreasing RH, were quantified by poke-and-flow and bead-mobility techniques at 293 ± 1 K. Based on the viscosity results, the particles of binary and ternary systems ranged from liquid to semisolid, and even the solid state depending on the RH. Moreover, we compared the measured viscosities of ternary systems to the predicted viscosities with excellent agreement.
Joseph Lilek and Andreas Zuend
Atmos. Chem. Phys., 22, 3203–3233, https://doi.org/10.5194/acp-22-3203-2022, https://doi.org/10.5194/acp-22-3203-2022, 2022
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Depending on temperature and chemical makeup, certain aerosols can be highly viscous or glassy, with atmospheric implications. We have therefore implemented two major upgrades to the predictive viscosity model AIOMFAC-VISC. First, we created a new viscosity model for aqueous electrolyte solutions containing an arbitrary number of ion species. Second, we integrated the electrolyte model within the existing AIOMFAC-VISC framework to enable viscosity predictions for organic–inorganic mixtures.
Hang Yin, Jing Dou, Liviana Klein, Ulrich K. Krieger, Alison Bain, Brandon J. Wallace, Thomas C. Preston, and Andreas Zuend
Atmos. Chem. Phys., 22, 973–1013, https://doi.org/10.5194/acp-22-973-2022, https://doi.org/10.5194/acp-22-973-2022, 2022
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Iodine and carbonate species are important components in marine and dust aerosols, respectively. We introduce an extended version of the AIOMFAC thermodynamic mixing model, which includes the ions I−, IO3−, HCO3−, CO32−, OH−, and CO2(aq) as new species, and we discuss two methods for solving the carbonate dissociation equilibria numerically. We also present new experimental water activity data for aqueous iodide and iodate systems.
Dalrin Ampritta Amaladhasan, Claudia Heyn, Christopher R. Hoyle, Imad El Haddad, Miriam Elser, Simone M. Pieber, Jay G. Slowik, Antonio Amorim, Jonathan Duplissy, Sebastian Ehrhart, Vladimir Makhmutov, Ugo Molteni, Matti Rissanen, Yuri Stozhkov, Robert Wagner, Armin Hansel, Jasper Kirkby, Neil M. Donahue, Rainer Volkamer, Urs Baltensperger, Martin Gysel-Beer, and Andreas Zuend
Atmos. Chem. Phys., 22, 215–244, https://doi.org/10.5194/acp-22-215-2022, https://doi.org/10.5194/acp-22-215-2022, 2022
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We use a combination of models for gas-phase chemical reactions and equilibrium gas–particle partitioning of isoprene-derived secondary organic aerosols (SOAs) informed by dark ozonolysis experiments conducted in the CLOUD chamber. Our predictions cover high to low relative humidities (RHs) 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 semi-volatile organics.
Young-Chul Song, Joseph Lilek, Jae Bong Lee, Man Nin Chan, Zhijun Wu, Andreas Zuend, and Mijung Song
Atmos. Chem. Phys., 21, 10215–10228, https://doi.org/10.5194/acp-21-10215-2021, https://doi.org/10.5194/acp-21-10215-2021, 2021
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We report viscosity of binary mixtures of organic material / H2O and inorganic salts / H2O, as well as ternary mixtures of organic material / inorganic salts/ H2O, over the atmospheric relative humidity (RH) range. The viscosity measurements indicate that the studied mixed organic–inorganic particles range in phase state from liquid to semi-solid or even solid across the atmospheric RH range at a temperature of 293 K.
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Short summary
A 2-dimensional polarity–volatility framework is introduced. It enables the automated characterization of thousands of organics and their systematic lumping into adjustable sets of surrogate components. A new polarity metric based on an activity coefficient ratio is presented for use in this framework. A related molecule substructure parsing tool for input file generation is introduced. This framework enables reduced-complexity representations of near-explicit organic aerosol systems.
A 2-dimensional polarity–volatility framework is introduced. It enables the automated...
