Articles | Volume 26, issue 3
https://doi.org/10.5194/acp-26-2319-2026
© 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/acp-26-2319-2026
© Author(s) 2026. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Temperature–RH dependent viscosity of organic aerosols from 273 to 303 K: implications for global N2O5 uptake
Atta Ullah
Department of Earth and Environmental Sciences, and Earth Environmental System Research Center, Jeonbuk National University, Jeollabuk-do Jeonju-si 54896, Republic of Korea
Key Laboratory of Industrial Ecology and Environmental Engineering (Ministry of Education), School of Environmental Science and Technology, Dalian University of Technology, Dalian 116024, China
Mijung Song
CORRESPONDING AUTHOR
Department of Earth and Environmental Sciences, and Earth Environmental System Research Center, Jeonbuk National University, Jeollabuk-do Jeonju-si 54896, Republic of Korea
Department of Environment and Energy, Jeonbuk National University, Jeollabuk-do Jeonju-si 54896, Republic of Korea
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Cited articles
Ammann, M., Cox, R. A., Crowley, J. N., Jenkin, M. E., Mellouki, A., Rossi, M. J., Troe, J., and Wallington, T. J.: Evaluated kinetic and photochemical data for atmospheric chemistry: Volume VI – heterogeneous reactions with liquid substrates, Atmos. Chem. Phys., 13, 8045–8228, https://doi.org/10.5194/acp-13-8045-2013, 2013.
Angell, C. A.: Relaxation in liquids, polymers and plastic crystals – strong/fragile patterns and problems, J. Non-Cryst. Solids, 131–133, 13–31, https://doi.org/10.1016/0022-3093(91)90266-9, 1991.
Bateman, A. P., Bertram, A. K., and Martin, S. T.: Hygroscopic influence on the semisolid-to-liquid transition of secondary organic materials, J. Phys. Chem. A, 119, 4386–4395, https://doi.org/10.1021/jp508521c, 2015.
Bei, N., Xiao, B., Wang, R., Yang, Y., Liu, L., Han, Y., and Li, G.: Impacts of aerosol–radiation and aerosol–cloud interactions on a short-term heavy-rainfall event – a case study in the Guanzhong Basin, China, Atmos. Chem. Phys., 25, 10931–10948, https://doi.org/10.5194/acp-25-10931-2025, 2025.
Berkemeier, T., Shiraiwa, M., Pöschl, U., and Koop, T.: Competition between water uptake and ice nucleation by glassy organic aerosol particles, Atmos. Chem. Phys., 14, 12513–12531, https://doi.org/10.5194/acp-14-12513-2014, 2014.
Champion, W. M., Rothfuss, N. E., Petters, M. D., and Grieshop, A. P.: Volatility and viscosity are correlated in terpene secondary organic aerosol formed in a flow reactor, Environ. Sci. Technol. Lett., 6, 513–519, https://doi.org/10.1021/acs.estlett.9b00412, 2019.
Chenyakin, Y., Ullmann, D. A., Evoy, E., Renbaum-Wolff, L., Kamal, S., and Bertram, A. K.: Diffusion coefficients of organic molecules in sucrose–water solutions and comparison with Stokes–Einstein predictions, Atmos. Chem. Phys., 17, 2423–2435, https://doi.org/10.5194/acp-17-2423-2017, 2017.
Cosman, L. M., Knopf, D. A., and Bertram, A. K.: N2O5 reactive uptake on aqueous sulfuric acid solutions coated with branched and straight-chain insoluble organic surfactants, J. Phys. Chem. A, 112, 2386–2396, https://doi.org/10.1021/jp710685r, 2008.
DeRieux, W.-S. W., Li, Y., Lin, P., Laskin, J., Laskin, A., Bertram, A. K., Nizkorodov, S. A., and Shiraiwa, M.: Predicting the glass transition temperature and viscosity of secondary organic material using molecular composition, Atmos. Chem. Phys., 18, 6331–6351, https://doi.org/10.5194/acp-18-6331-2018, 2018.
El Haddad, I., Vienneau, D., Daellenbach, K. R., Modini, R., Slowik, J. G., Upadhyay, A., Vasilakos, P. N., Bell, D., de Hoogh, K., and Prevot, A. S. H.: Opinion: How will advances in aerosol science inform our understanding of the health impacts of outdoor particulate pollution?, Atmos. Chem. Phys., 24, 11981–12011, https://doi.org/10.5194/acp-24-11981-2024, 2024.
Galib, M. and Limmer, D. T.: Reactive uptake of N2O5 by atmospheric aerosol is dominated by interfacial processes, Science, 371, https://doi.org/10.1126/science.abd7716, 2021.
Gaston, C. J., Thornton, J. A., and Ng, N. L.: Reactive uptake of N2O5 to internally mixed inorganic and organic particles: the role of organic carbon oxidation state and inferred organic phase separations, Atmos. Chem. Phys., 14, 5693–5707, https://doi.org/10.5194/acp-14-5693-2014, 2014.
Gerrebos, N. G., Browning, L. P., Nikkho, S., Chartrand, E. R., Zaks, J., Wu, C., and Bertram, A. K.: Two-phase morphology and drastic viscosity changes in biomass burning organic aerosol after hydroxyl radical aging, Environ. Sci. Atmos., https://doi.org/10.1039/d5ea00084j, 2025.
Gerrebos, N. G. A., Zaks, J., Gregson, F. K. A., Walton-Raaby, M., Meeres, H., Zigg, I., Zandberg, W. F., and Bertram, A. K.: High viscosity and two phases observed over a range of relative humidities in biomass burning organic aerosol from canadian wildfires, Environ. Sci. Technol., 58, 21716–21728, https://doi.org/10.1021/acs.est.4c09148, 2024.
Grayson, J. W., Song, M., Sellier, M., and Bertram, A. K.: Validation of the poke-flow technique combined with simulations of fluid flow for determining viscosities in samples with small volumes and high viscosities, Atmos. Meas. Tech., 8, 2463–2472, https://doi.org/10.5194/amt-8-2463-2015, 2015.
Grayson, J. W., Zhang, Y., Mutzel, A., Renbaum-Wolff, L., Böge, O., Kamal, S., Herrmann, H., Martin, S. T., and Bertram, A. K.: Effect of varying experimental conditions on the viscosity of α-pinene derived secondary organic material, Atmos. Chem. Phys., 16, 6027–6040, https://doi.org/10.5194/acp-16-6027-2016, 2016.
Grayson, J. W., Evoy, E., Song, M., Chu, Y., Maclean, A., Nguyen, A., Upshur, M. A., Ebrahimi, M., Chan, C. K., Geiger, F. M., Thomson, R. J., and Bertram, A. K.: The effect of hydroxyl functional groups and molar mass on the viscosity of non-crystalline organic and organic–water particles, Atmos. Chem. Phys., 17, 8509–8524, https://doi.org/10.5194/acp-17-8509-2017, 2017.
Gregson, F. K. A., Gerrebos, N. G. A., Schervish, M., Nikkho, S., Schnitzler, E. G., Schwartz, C., Carlsten, C., Abbatt, J. P. D., Kamal, S., Shiraiwa, M., and Bertram, A. K.: Phase behavior and viscosity in biomass burning organic aerosol and climatic impacts, Environ. Sci. Technol., 57, 14548–14557, https://doi.org/10.1021/acs.est.3c03231, 2023.
Gržinić, G., Bartels-Rausch, T., Berkemeier, T., Türler, A., and Ammann, M.: Viscosity controls humidity dependence of N2O5 uptake to citric acid aerosol, Atmos. Chem. Phys., 15, 13615–13625, https://doi.org/10.5194/acp-15-13615-2015, 2015.
Hersbach, H., Bell, B., Berrisford, P., Biavati, G., Horányi, A., Muñoz Sabater, J., Nicolas, J., Peubey, C., Radu, R., and Rozum, I.: ERA5 monthly averaged data on pressure levels from 1940 to present, Copernicus Climate Change Service (C3S) [data set], https://doi.org/10.24381/cds.6860a573, 2023.
Jeong, R., Lilek, J., Zuend, A., Xu, R., Chan, M. N., Kim, D., Moon, H. G., and Song, M.: Viscosity and physical state of sucrose mixed with ammonium sulfate droplets, Atmos. Chem. Phys., 22, 8805–8817, https://doi.org/10.5194/acp-22-8805-2022, 2022.
Kasparoglu, S., Li, Y., Shiraiwa, M., and Petters, M. D.: Toward closure between predicted and observed particle viscosity over a wide range of temperatures and relative humidity, Atmos. Chem. Phys., 21, 1127–1141, https://doi.org/10.5194/acp-21-1127-2021, 2021.
Kiland, K. J., Maclean, A. M., Kamal, S., and Bertram, A. K.: Diffusion of organic molecules as a function of temperature in a sucrose matrix (a proxy for secondary organic aerosol), J. Phys. Chem. Lett., 10, 5902–5908, https://doi.org/10.1021/acs.jpclett.9b02182, 2019.
Kiland, K. J., Mahrt, F., Peng, L., Nikkho, S., Zaks, J., Crescenzo, G. V., and Bertram, A. K.: Viscosity, glass formation, and mixing times within secondary organic aerosol from biomass burning phenolics, ACS Earth and Space Chem., 7, 1388–1400, https://doi.org/10.1021/acsearthspacechem.3c00039, 2023.
Knopf, D. A., Alpert, P. A., and Wang, B.: The role of organic aerosol in atmospheric ice nucleation: a review, ACS Earth Space Chem., 2, 168–202, https://doi.org/10.1021/acsearthspacechem.7b00120, 2018.
Knopf, D. A., Ammann, M., Berkemeier, T., Pöschl, U., and Shiraiwa, M.: Desorption lifetimes and activation energies influencing gas–surface interactions and multiphase chemical kinetics, Atmos. Chem. Phys., 24, 3445–3528, https://doi.org/10.5194/acp-24-3445-2024, 2024.
Koop, T., Bookhold, J., Shiraiwa, M., and Pöschl, U.: Glass transition and phase state of organic compounds: dependency on molecular properties and implications for secondary organic aerosols in the atmosphere, Phys. Chem. Chem. Phys., 13, 19238–19255, https://doi.org/10.1039/c1cp22617g, 2011.
Kuwata, M. and Martin, S. T.: Phase of atmospheric secondary organic material affects its reactivity, Proc. Natl. Acad. Sci. U.S.A., 109, 17354–17359, https://doi.org/10.1073/pnas.1209071109, 2012.
Ladino, L. A., Zhou, S., Yakobi-Hancock, J. D., Aljawhary, D., and Abbatt, J.: Factors controlling the ice nucleating abilities of α-pinene SOA particles, J. Geophys. Res. Atmos., 119, 9041–9051, https://doi.org/10.1002/2014jd021578, 2014.
Li, J., Forrester, S. M., and Knopf, D. A.: Heterogeneous oxidation of amorphous organic aerosol surrogates by O3, NO3, and OH at typical tropospheric temperatures, Atmos. Chem. Phys., 20, 6055–6080, https://doi.org/10.5194/acp-20-6055-2020, 2020a.
Li, J. N. and Knopf, D. A.: Representation of multiphase OH oxidation of amorphous organic aerosol for tropospheric conditions, Environ. Sci. Technol., 55, 7266–7275, https://doi.org/10.1021/acs.est.0c07668, 2021.
Li, Y., Day, D. A., Stark, H., Jimenez, J. L., and Shiraiwa, M.: Predictions of the glass transition temperature and viscosity of organic aerosols from volatility distributions, Atmos. Chem. Phys., 20, 8103–8122, https://doi.org/10.5194/acp-20-8103-2020, 2020b.
Lienhard, D. M., Huisman, A. J., Krieger, U. K., Rudich, Y., Marcolli, C., Luo, B. P., Bones, D. L., Reid, J. P., Lambe, A. T., Canagaratna, M. R., Davidovits, P., Onasch, T. B., Worsnop, D. R., Steimer, S. S., Koop, T., and Peter, T.: Viscous organic aerosol particles in the upper troposphere: diffusivity-controlled water uptake and ice nucleation?, Atmos. Chem. Phys., 15, 13599–13613, https://doi.org/10.5194/acp-15-13599-2015, 2015.
Luu, R., Schervish, M., June, N. A., O'Donnell, S. E., Jathar, S. H., Pierce, J. R., and Shiraiwa, M.: Global simulations of phase state and equilibration time scales of secondary organic aerosols with GEOS-Chem, ACS Earth Space Chem., 9, 288–302, https://doi.org/10.1021/acsearthspacechem.4c00281, 2025.
Maclean, A. M., Butenhoff, C. L., Grayson, J. W., Barsanti, K., Jimenez, J. L., and Bertram, A. K.: Mixing times of organic molecules within secondary organic aerosol particles: a global planetary boundary layer perspective, Atmos. Chem. Phys., 17, 13037–13048, https://doi.org/10.5194/acp-17-13037-2017, 2017.
Maclean, A. M., Smith, N. R., Li, Y., Huang, Y., Hettiyadura, A. P. S., Crescenzo, G. V., Shiraiwa, M., Laskin, A., Nizkorodov, S. A., and Bertram, A. K.: Humidity-dependent viscosity of secondary organic aerosol from ozonolysis of β-caryophyllene: measurements, predictions, and implications, ACS Earth and Space Chem., 5, 305–318, https://doi.org/10.1021/acsearthspacechem.0c00296, 2021a.
Maclean, A. M., Li, Y., Crescenzo, G. V., Smith, N. R., Karydis, V. A., Tsimpidi, A. P., Butenhoff, C. L., Faiola, C. L., Lelieveld, J., Nizkorodov, S. A., Shiraiwa, M., and Bertram, A. K.: Global distribution of the phase state and mixing times within secondary organic aerosol particles in the troposphere based on room-temperature viscosity measurements, ACS Earth and Space Chem., 5, 3458–3473, https://doi.org/10.1021/acsearthspacechem.1c00296, 2021b.
Manavi, S. E. I., Aktypis, A., Siouti, E., Skyllakou, K., Myriokefalitakis, S., Kanakidou, M., and Pandis, S. N.: Atmospheric aerosol spatial variability: Impacts on air quality and climate change, One Earth, 8, https://doi.org/10.1016/j.oneear.2025.101237, 2025.
Marshall, F., Berkemeier, T., Shiraiwa, M., Nandy, L., Ohm, P., Dutcher, C. S., and Reid, J. P.: Influence of particle viscosity on mass transfer and heterogeneous ozonolysis kinetics in aqueous–sucrose–maleic acid aerosol, Phys. Chem. Chem. Phys., 20, 15560–15573, https://doi.org/10.1039/c8cp01666f, 2018.
Marshall, F. H., Miles, R. E. H., Song, Y.-C., Ohm, P. B., Power, R. M., Reid, J. P., and Dutcher, C. S.: Diffusion and reactivity in ultraviscous aerosol and the correlation with particle viscosity, Chem. Sci., 7, 1298–1308, https://doi.org/10.1039/C5SC03223G, 2016.
McNeill, V. F.: Atmospheric aerosols: clouds, chemistry, and climate, Annu. Rev. Chem. Biomol. Eng., 8, 427–444, https://doi.org/10.1146/annurev-chembioeng-060816-101538, 2017.
McNeill, V. F., Patterson, J., Wolfe, G. M., and Thornton, J. A.: The effect of varying levels of surfactant on the reactive uptake of N2O5 to aqueous aerosol, Atmos. Chem. Phys., 6, 1635–1644, https://doi.org/10.5194/acp-6-1635-2006, 2006.
Nault, B. A., Jo, D. S., McDonald, B. C., Campuzano-Jost, P., Day, D. A., Hu, W., Schroder, J. C., Allan, J., Blake, D. R., Canagaratna, M. R., Coe, H., Coggon, M. M., DeCarlo, P. F., Diskin, G. S., Dunmore, R., Flocke, F., Fried, A., Gilman, J. B., Gkatzelis, G., Hamilton, J. F., Hanisco, T. F., Hayes, P. L., Henze, D. K., Hodzic, A., Hopkins, J., Hu, M., Huey, L. G., Jobson, B. T., Kuster, W. C., Lewis, A., Li, M., Liao, J., Nawaz, M. O., Pollack, I. B., Peischl, J., Rappenglück, B., Reeves, C. E., Richter, D., Roberts, J. M., Ryerson, T. B., Shao, M., Sommers, J. M., Walega, J., Warneke, C., Weibring, P., Wolfe, G. M., Young, D. E., Yuan, B., Zhang, Q., de Gouw, J. A., and Jimenez, J. L.: Secondary organic aerosols from anthropogenic volatile organic compounds contribute substantially to air pollution mortality, Atmos. Chem. Phys., 21, 11201–11224, https://doi.org/10.5194/acp-21-11201-2021, 2021.
Nikkho, S., Bai, B., Mahrt, F., Zaks, J., Peng, L., Kiland, K. J., Liu, P. F., and Bertram, A. K.: Secondary organic aerosol from biomass burning phenolic compounds and nitrate radicals can be highly viscous over a wide relative humidity range, Environ. Sci. Technol., 58, 21702–21715, https://doi.org/10.1021/acs.est.4c06235, 2024.
Pandis, S. N., Harley, R. A., Cass, G. R., and Seinfeld, J. H.: Secondary organic aerosol formation and transport, Atmos. Environ. Part A. General Topics, 26, 2269–2282, https://doi.org/10.1016/0960-1686(92)90358-r, 1992.
Petters, S. S., Kreidenweis, S. M., Grieshop, A. P., Ziemann, P. J., and Petters, M. D.: Temperature- and humidity-dependent phase states of secondary organic aerosols, Geophys. Res. Lett., 46, 1005–1013, https://doi.org/10.1029/2018GL080563, 2019.
Pöschl, U.: Atmospheric aerosols: composition, transformation, climate and health effects, Angew. Chem.-Int. Ed., 44, 7520–7540, https://doi.org/10.1002/anie.200501122, 2005.
Power, R. M., Simpson, S. H., Reid, J. P., and Hudson, A. J.: The transition from liquid to solid-like behaviour in ultrahigh viscosity aerosol particles, Chem. Sci., 4, 2597–2604, https://doi.org/10.1039/c3sc50682g, 2013.
Reid, J. P., Bertram, A. K., Topping, D., Laskin, A., Martin, S. T., Petters, M. D., Pope, F. D., and Rovelli, G.: The viscosity of atmospherically relevant organic particles, Nat. Commun., 9, 956–956, https://doi.org/10.1038/s41467-018-03027-z, 2018.
Renbaum-Wolff, L., Grayson, J. W., and Bertram, A. K.: Technical Note: New methodology for measuring viscosities in small volumes characteristic of environmental chamber particle samples, Atmos. Chem. Phys., 13, 791–802, https://doi.org/10.5194/acp-13-791-2013, 2013a.
Renbaum-Wolff, L., Grayson, J. W., Bateman, A. P., Kuwata, M., Sellier, M., Murray, B. J., Shilling, J. E., Martin, S. T., and Bertram, A. K.: Viscosity of α-pinene secondary organic material and implications for particle growth and reactivity, Proc. Natl. Acad. Sci. U.S.A., 110, 8014–8019, https://doi.org/10.1073/pnas.1219548110, 2013b.
Rothfuss, N. E. and Petters, M. D.: Influence of functional groups on the viscosity of organic aerosol, Environ. Sci. Technol., 51, 271–279, https://doi.org/10.1021/acs.est.6b04478, 2017a.
Rothfuss, N. E. and Petters, M. D.: Characterization of the temperature and humidity-dependent phase diagram of amorphous nanoscale organic aerosols, Phys. Chem. Chem. Phys., 19, 6532–6545, https://doi.org/10.1039/c6cp08593h, 2017b.
Ryder, O. S., Campbell, N. R., Morris, H., Forestieri, S., Ruppel, M. J., Cappa, C., Tivanski, A., Prather, K., and Bertram, T. H.: Role of organic coatings in regulating N2O5 reactive uptake to sea spray aerosol, J. Phys. Chem. A, 119, 11683–11692, https://doi.org/10.1021/acs.jpca.5b08892, 2015.
Saukko, E., Lambe, A. T., Massoli, P., Koop, T., Wright, J. P., Croasdale, D. R., Pedernera, D. A., Onasch, T. B., Laaksonen, A., Davidovits, P., Worsnop, D. R., and Virtanen, A.: Humidity-dependent phase state of SOA particles from biogenic and anthropogenic precursors, Atmos. Chem. Phys., 12, 7517–7529, https://doi.org/10.5194/acp-12-7517-2012, 2012.
Sellier, M., Grayson, J. W., Renbaum-Wolff, L., Song, M., and Bertram, A. K.: Estimating the viscosity of a highly viscous liquid droplet through the relaxation time of a dry spot, J. Rheol., 59, 733–750, https://doi.org/10.1122/1.4917240, 2015.
Shiraiwa, M. and Seinfeld, J. H.: Equilibration timescale of atmospheric secondary organic aerosol partitioning, Geophys. Res. Lett., 39, https://doi.org/10.1029/2012gl054008, 2012.
Shiraiwa, M., Ammann, M., Koop, T., and Pöschl, U.: Gas uptake and chemical aging of semisolid organic aerosol particles, Proc. Natl. Acad. Sci. U.S.A., 108, 11003–11008, https://doi.org/10.1073/pnas.1103045108, 2011.
Shiraiwa, M., Yee, L. D., Schilling, K. A., Loza, C. L., Craven, J. S., Zuend, A., Ziemann, P. J., and Seinfeld, J. H.: Size distribution dynamics reveal particle-phase chemistry in organic aerosol formation, Proc. Natl. Acad. Sci. U.S.A., 110, 11746–11750, https://doi.org/10.1073/pnas.1307501110, 2013.
Shiraiwa, M., Li, Y., Tsimpidi, A. P., Karydis, V. A., Berkemeier, T., Pandis, S. N., Lelieveld, J., Koop, T., and Pöschl, U.: Global distribution of particle phase state in atmospheric secondary organic aerosols, Nat. Commun., 8, 15002–15002, https://doi.org/10.1038/ncomms15002, 2017.
Slade, J. H. and Knopf, D. A.: Multiphase OH oxidation kinetics of organic aerosol: The role of particle phase state and relative humidity, Geophys. Res. Lett., 41, 5297–5306, https://doi.org/10.1002/2014gl060582, 2014.
Song, M., Liu, P. F., Hanna, S. J., Li, Y. J., Martin, S. T., and Bertram, A. K.: Relative humidity-dependent viscosities of isoprene-derived secondary organic material and atmospheric implications for isoprene-dominant forests, Atmos. Chem. Phys., 15, 5145–5159, https://doi.org/10.5194/acp-15-5145-2015, 2015.
Song, M., Liu, P. F., Hanna, S. J., Zaveri, R. A., Potter, K., You, Y., Martin, S. T., and Bertram, A. K.: Relative humidity-dependent viscosity of secondary organic material from toluene photo-oxidation and possible implications for organic particulate matter over megacities, Atmos. Chem. Phys., 16, 8817–8830, https://doi.org/10.5194/acp-16-8817-2016, 2016.
Song, M., Li, Y., Seong, C., Yang, H., Jang, K.-S., Wu, Z., Lee, J. Y., Matsuki, A., and Ahn, J.: Direct observation of liquid–liquid phase separation and core–shell morphology of PM2.5 collected from three northeast Asian cities and implications for N2O5 hydrolysis, ACS ES&T Air, 2, 1079–1088, https://doi.org/10.1021/acsestair.5c00043, 2025.
Song, M., Maclean, A. M., Huang, Y., Smith, N. R., Blair, S. L., Laskin, J., Laskin, A., DeRieux, W.-S. W., Li, Y., Shiraiwa, M., Nizkorodov, S. A., and Bertram, A. K.: Liquid–liquid phase separation and viscosity within secondary organic aerosol generated from diesel fuel vapors, Atmos. Chem. Phys., 19, 12515–12529, https://doi.org/10.5194/acp-19-12515-2019, 2019.
Song, M., Jeong, R., Kim, D., Qiu, Y., Meng, X., Wu, Z., Zuend, A., Ha, Y., Kim, C., Kim, H., Gaikwad, S., Jang, K.-S., Lee, J. Y., and Ahn, J.: Comparison of phase states of PM2.5 over megacities, Seoul and Beijing, and their implications on particle size distribution, Environ. Sci. Technol., 56, 17581–17590, https://doi.org/10.1021/acs.est.2c06377, 2022.
Song, Y.-C., Lilek, J., Lee, J. B., Chan, M. N., Wu, Z., Zuend, A., and Song, M.: Viscosity and phase state of aerosol particles consisting of sucrose mixed with inorganic salts, Atmos. Chem. Phys., 21, 10215–10228, https://doi.org/10.5194/acp-21-10215-2021, 2021.
Su, H., Cheng, Y. F., and Pöschl, U.: New multiphase chemical processes influencing atmospheric aerosols, air quality, and climate in the Anthropocene, Acc. Chem. Res., 53, 2034–2043, https://doi.org/10.1021/acs.accounts.0c00246, 2020.
Sun, Y. L., Luo, H., Li, Y., Zhou, W., Xu, W. Q., Fu, P. Q., and Zhao, D. F.: Atmospheric organic aerosols: online molecular characterization and environmental impacts, npj Clim. Atmos. Sci., 8, https://doi.org/10.1038/s41612-025-01199-2, 2025.
Wagner, N. L., Riedel, T. P., Young, C. J., Bahreini, R., Brock, C. A., Dubé, W. P., Kim, S., Middlebrook, A. M., Öztürk, F., Roberts, J. M., Russo, R., Sive, B., Swarthout, R., Thornton, J. A., VandenBoer, T. C., Zhou, Y., and Brown, S. S.: N2O5 uptake coefficients and nocturnal NO2 removal rates determined from ambient wintertime measurements, J. Geophys. Res. Atmos., 118, 9331–9350, https://doi.org/10.1002/jgrd.50653, 2013.
Wall, C. J., Norris, J. R., Possner, A., Mccoy, D. T., Mccoy, I. L., and Lutsko, N. J.: Assessing effective radiative forcing from aerosol-cloud interactions over the global ocean, Proc. Natl. Acad. Sci. U.S.A., 119, https://doi.org/10.1073/pnas.2210481119, 2022.
You, Y., Renbaum-Wolff, L., Carreras-Sospedra, M., Hanna, S. J., Hiranuma, N., Kamal, S., Smith, M. L., Zhang, X., Weber, R. J., and Shilling, J. E.: Images reveal that atmospheric particles can undergo liquid–liquid phase separations, Proc. Natl. Acad. Sci. U.S.A., 109, 13188–13193, https://doi.org/10.1073/pnas.1206414109, 2012.
Zaveri, R. A., Shilling, J. E., Zelenyuk, A., Liu, J., Bell, D. M., D'Ambro, E. L., Gaston, C. J., Thornton, J. A., Laskin, A., Lin, P., Wilson, J. M., Easter, R. C., Wang, J., Bertram, A. K., Martin, S. T., Seinfeld, J. H., and Worsnop, D. R.: Growth kinetics and size distribution dynamics of viscous secondary organic aerosol, Environ. Sci. Technol., 52, 1191–1199, https://doi.org/10.1021/acs.est.7b04623, 2018.
Zhang, T., Zuo, P., Chen, Y., Liu, T., Zeng, L., Lin, W., and Ye, C.: Measurement report: Variations and environmental impacts of atmospheric N2O5 concentrations in urban Beijing during the 2022 Winter Olympics, EGUsphere, 2025, https://doi.org/10.5194/egusphere-2025-2210, 2025.
Zhang, Y., Liu, P., Han, Y., Li, Y., Chen, Q., Kuwata, M., and Martin, S. T.: Aerosols in Atmospheric Chemistry, ACS In Focus, American Chemical Society, https://doi.org/10.1021/acsinfocus.7e5020, 2021.
Zhou, S., Shiraiwa, M., McWhinney, R. D., Pöschl, U., and Abbatt, J. P. D.: Kinetic limitations in gas-particle reactions arising from slow diffusion in secondary organic aerosol, Faraday Discuss., 165, 391–406, https://doi.org/10.1039/c3fd00030c, 2013.
Zobrist, B., Soonsin, V., Luo, B. P., Krieger, U. K., Marcolli, C., Peter, T., and Koop, T.: Ultra-slow water diffusion in aqueous sucrose glasses, Phys. Chem. Chem. Phys., 13, 3514–3526, https://doi.org/10.1039/c0cp01273d, 2011.
Short summary
We investigated the temperature- and relative-humidity-dependent viscosity of organic aerosols using sucrose-water droplets as a model. The results show that particles remain liquid near the Earth’s surface but become semi-solid or glassy at higher altitudes. These viscosity changes influence chemical reactions such as nitrogen oxide uptake, improving understanding of air quality and climate processes.
We investigated the temperature- and relative-humidity-dependent viscosity of organic aerosols...
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