ADCHAM results for The nature of temperature induced phase transitions in secondary organic aerosol particles

Model results for: The nature of temperature induced phase transitions in secondary organic aerosol particles Modelled bulk properties of secondary organic aerosols (SOA) formed from alpha-pinene ozonolysis presented in Jensen et al. (2025). The model results were generated with the aerosol dynamics, gas- and particle-phase chemistry kinetic multilayer model (ADCHAM, Roldin et al., 2014), using the detailed peroxy radical autoxidation mechanism (PRAM; Roldin et al., 2019) which represents the temperature dependent formation of low-volatility highly oxygenated organic molecules (HOM) during the ozone and OH oxidation of alpha-pinene. The file ADCHAM_Exp8_9_10_SOA_bulk_properties.xlsx contains model results from 3 simulated experiments in the AURA smog chamber, including time series with the modelled: Total particle volume concentrations (PV) and particle number concentration based geometric mean diameters (GMD) calculated based on either the modelled particles mobility diameters (dm) or the particle volume equivalent diameters (dv), Dry (no water) SOA glass transition temperatures (Tg,org) and the SOA glass transition temperatures at the actual RH in the chamber (Tg). SOA viscosity (η) SOA fragility parameters (D) The HOM mass fractions in the SOA (ωHOM) The SOA O:C (oxygen to carbon ratio) The mass fraction of water in the SOA particles (ωwater) The file ADCHAM_Figure4_data.xlsx contain all result presented in Figure 4 in Jensen et al. (2025). This includes the modelled SOA η , Tg and ωHOM at a wide range of atmospheric relevant temperatures (233-303 K) and RH conditions (30-90%). The results demostrates how the SOA composition (O:C and ωHOM) and resulting viscosity depends strongly on both the the temperature at which the SOA is formed (T0) and the alpha-pinene and ozone concentrations (i.e. [alpha-pinene] x [ozone]). At atmsopheric relevant relatively low alpha-pinene and ozone concentrations and relatively high T0 (typical for boreal forest boundary layer summertime conditions) the formed SOA has a high ωHOM which result in SOA particles with stays highly viscous, glassy, even at relatively high RH and temperature conditions. References: Jensen, L. N., Kristensen, K., Iversen, E. M., Canagaratna, M. R., Roldin, P., and Bilde, M., The nature of temperature induced phase transitions in secondary organic aerosol particles, Environmental Science & Technology 2025 XX (XX), XXXX-XXXX, DOI: XXXXX Roldin, P., Eriksson, A. C., Nordin, E. Z., Hermansson, E., Mogensen, D., Rusanen, A., Boy, M., Swietlicki, E., Svenningsson, B., Zelenyuk, A., and Pagels, J.: Modelling non-equilibrium secondary organic aerosol formation and evaporation with the aerosol dynamics, gas- and particle-phase chemistry kinetic multilayer model ADCHAM, Atmos. Chem. Phys., 2014, 14, 7953–7993, https://doi.org/10.5194/acp-14-7953-2014. Roldin, P., Ehn, M., Kurtén, T. et al. The role of highly oxygenated organic molecules in the Boreal aerosol-cloud-climate system. Nat Commun, 2019, 10, 4370, https://doi.org/10.1038/s41467-019-12338-8