Articles | Volume 19, issue 1
https://doi.org/10.5194/amt-19-323-2026
© 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/amt-19-323-2026
© Author(s) 2026. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Research article
| 
16 Jan 2026
Research article |
| 16 Jan 2026
| 16 Jan 2026
A universal aerosol composition analysis method for optical tweezers measurement and its application to determine hygroscopic growth factor of single-particle aerosol
Chengyi Fan
Department of Atmospheric and Oceanic Sciences, School of Physics, Peking University, Beijing 100871, China
Chunsheng Zhao
CORRESPONDING AUTHOR
Department of Atmospheric and Oceanic Sciences, School of Physics, Peking University, Beijing 100871, China
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Cited articles
Ashkin, A., Dziedzic, J. M., Bjorkholm, J. E., and Chu, S.: Observation of a single-beam gradient force optical trap for dielectric particles, Opt. Lett., 11, 288–290, https://doi.org/10.1364/OL.11.000288, 1986.
Benner, R. E., Barber, P. W., Owen, J. F., and Chang, R. K.: Observation of Structure Resonances in the Fluorescence Spectra from Microspheres, Phys. Rev. Lett., 44, 475–478, https://doi.org/10.1103/PhysRevLett.44.475, 1980.
Boucher, O., Randall, D., Artaxo, P., Bretherton, C., Feingold, G., Forster, P., Kerminen, V.-M., Kondo, Y., Liao, H., Lohmann, U., Rasch, P., Satheesh, S. K., Sherwood, S., Stevens, B., and Zhang, X. Y.: Clouds and Aerosols, in: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change, edited by: Stocker, T. F., Qin, D., Plattner, G.-K., Tignor, M., Allen, S. K., Boschung, J., Nauels, A., Xia, Y., Bex, V., and Midgley, P. M., Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, https://doi.org/10.1017/CBO9781107415324.016, 2013.
Cai, C., Miles, R. E. H., Cotterell, M. I., Marsh, A., Rovelli, G., Rickards, A. M. J., Zhang, Y., and Reid, J. P.: Comparison of Methods for Predicting the Compositional Dependence of the Density and Refractive Index of Organic–Aqueous Aerosols, J. Phys. Chem. A, 120, 6604–6617, https://doi.org/10.1021/acs.jpca.6b05986, 2016.
Che, Y.-Y., Shen, J., Zhou, J.-C., and He, C.-H.: Thermal Conductivity and Density of (NH4)2SO4+ H2O, NH4NO3+ H2O, and (NH4)2SO4+ NH4NO3+ H2O Solutions at T = (278.15 to 333.15) K, J. Chem. Eng. Data, 57, 1486–1491, https://doi.org/10.1021/je201390r, 2012.
Clegg, S. L. and Wexler, A. S.: Densities and Apparent Molar Volumes of Atmospherically Important Electrolyte Solutions. 1. The Solutes H2SO4, HNO3, HCl, Na2SO4, NaNO3, NaCl, (NH4)2SO4, NH4NO3, and NH4Cl from 0 to 50 °C, Including Extrapolations to Very Low Temperature and to the Pure Liquid State, and NaHSO4, NaOH, and NH3 at 25 °C, J. Phys. Chem. A, 115, 3393–3460, https://doi.org/10.1021/jp108992a, 2011.
Estillore, A. D., Morris, H. S., Or, V. W., Lee, H. D., Alves, M. R., Marciano, M. A., Laskina, O., Qin Z., Tivanski, A. V., and Grassian, V. H.: Linking hygroscopicity and surface microstructure of model inorganic salts, simple and complex carbohydrates, and authentic sea spray aerosol particles, Phys. Chem. Chem. Phys., 19, 21101–21111, https://doi.org/10.1039/C7CP04051B, 2017.
Fan, C., He, B., Guo, S., Qiu, J., and Zhao, C.: Insights into the real part of natural sea spray aerosol refractive index in the Pacific Ocean, Atmos. Chem. Phys., 25, 5761–5771, https://doi.org/10.5194/acp-25-5761-2025, 2025.
Hargreaves, G., Kwamena, N.-O. A., Zhang, Y. H., Butler, J. R., Rushworth, S., Clegg, S. L., and Reid, J. P.: Measurements of the Equilibrium Size of Supersaturated Aqueous Sodium Chloride Droplets at Low Relative Humidity Using Aerosol Optical Tweezers and an Electrodynamic Balance, J. Phys. Chem. A, 114, 1806–1815, https://doi.org/10.1021/jp9095985, 2010.
Hervello, M. F. and Sánchez, A.: Densities of Univalent Cation Sulfates in Ethanol + Water Solutions, J. Chem. Eng. Data, 52, 752–756, https://doi.org/10.1021/je060335h, 2007.
Kreidenweis, S. M. and Asa-Awuku, A.: Aerosol Hygroscopicity: Particle Water Content and Its Role in Atmospheric Processes, in: Treatise on Geochemistry, Elsevier, 331–361, https://doi.org/10.1016/B978-0-08-095975-7.00418-6, 2014.
Lee, J. W. L., Carrascón, V., Gallimore, P. J., Fuller, S. J., Björkegren, A., Spring, D. R., Pope, F. D., and Kalberer, M.: The effect of humidity on the ozonolysis of unsaturated compounds in aerosol particles, Phys. Chem. Chem. Phys., 14, 8023, https://doi.org/10.1039/c2cp24094g, 2012.
Li, L., Li, M., Fan, X., Chen, Y., Lin, Z., Hou, A., Zhang, S., Zheng, R., and Chen, J.: Measurement report: The variation properties of aerosol hygroscopic growth related to chemical composition during new particle formation days in a coastal city of Southeast China, Atmos. Chem. Phys., 25, 3669–3685, https://doi.org/10.5194/acp-25-3669-2025, 2025.
Liu, Y. and Daum, P. H.: Relationship of refractive index to mass density and self-consistency of mixing rules for multicomponent mixtures like ambient aerosols, J. Aerosol Sci., 39, 974–986, https://doi.org/10.1016/j.jaerosci.2008.06.006, 2008.
Pariyothon, J., Bualert, S., Choomanee, P., Rungratanaubon, T., Thongyen, T., Fakkaew, N., Phuetfoo, C., Phupijit, J., and Szymanski, W. W.: Hygroscopic Growth Factors of Sub-micrometer Atmospheric Aerosols at Four Selected Sites in Thailand, Aerosol Air Qual. Res., 23, 220374, https://doi.org/10.4209/aaqr.220374, 2023.
Petters, M. D. and Kreidenweis, S. M.: A single parameter representation of hygroscopic growth and cloud condensation nucleus activity, Atmos. Chem. Phys., 7, 1961–1971, https://doi.org/10.5194/acp-7-1961-2007, 2007.
Pöhlker, M. L., Pöhlker, C., Quaas, J., Mülmenstädt, J., Pozzer, A., Andreae, M. O., Artaxo, P., Block, K., Coe, H., Ervens, B., Gallimore, P., Gaston, C. J., Gunthe, S. S., Henning, S., Herrmann, H., Krüger, O. O., McFiggans, G., Poulain, L., Raj, S. S., Reyes-Villegas, E., Royer, H. M., Walter, D., Wang, Y., and Pöschl, U.: Global organic and inorganic aerosol hygroscopicity and its effect on radiative forcing, Nat. Commun., 14, 6139, https://doi.org/10.1038/s41467-023-41695-8, 2023.
Preston, T. C. and Reid, J. P.: Accurate and efficient determination of the radius, refractive index, and dispersion of weakly absorbing spherical particle using whispering gallery modes, J. Opt. Soc. Am. B, 30, 2113–2122, https://doi.org/10.1364/JOSAB.30.002113, 2013.
Qiu, J., He, B., Zhang, L., Cheng, M., Guo, S., Fan, C., and Zhao, C.: Hygroscopic behavior of sea spray aerosols in offshore waters and open sea areas investigated with aerosol optical tweezers, Atmos. Environ., 321, 120360, https://doi.org/10.1016/j.atmosenv.2024.120360, 2024.
Shingler, T., Sorooshian, A., Ortega, A., Crosbie, E., Wonaschütz, A., Perring, A. E., Beyersdorf, A., Ziemba, L., Jimenez, J. L., Campuzano-Jost, P., Mikoviny, T., Wisthaler, A., and Russell, L. M.: Ambient observations of hygroscopic growth factor and f (RH) below 1: Case studies from surface and airborne measurements, JGR Atmospheres, 121, 13661–13677, https://doi.org/10.1002/2016JD025471, 2016.
Tan, C.-Y. and Huang, Y.-X.: Dependence of Refractive Index on Concentration and Temperature in Electrolyte Solution, Polar Solution, Nonpolar Solution, and Protein Solution, J. Chem. Eng. Data, 60, 2827–2833, https://doi.org/10.1021/acs.jced.5b00018, 2015.
Tang, I. N. and Munkelwitz, H. R.: Water activities, densities, and refractive indices of aqueous sulfates and sodium nitrate droplets of atmospheric importance, J. Geophys. Res., 99, 18801–18808, https://doi.org/10.1029/94JD01345, 1994.
Tang, M., Chan, C. K., Li, Y. J., Su, H., Ma, Q., Wu, Z., Zhang, G., Wang, Z., Ge, M., Hu, M., He, H., and Wang, X.: A review of experimental techniques for aerosol hygroscopicity studies, Atmos. Chem. Phys., 19, 12631–12686, https://doi.org/10.5194/acp-19-12631-2019, 2019.
Urréjola, S., Sánchez, A., and Hervello, M. F.: Refractive Indices of Sodium, Potassium, and Ammonium Sulfates in Ethanol–Water Solutions, J. Chem. Eng. Data, 55, 2924–2929, https://doi.org/10.1021/je9010129, 2010.
U.S. Department of Agriculture: Agricultural Marketing Service, Specialty Crops Inspection Division.: Appendix XV – Sucrose Conversion Table, Technical Procedures Manual, https://www.ams.usda.gov/sites/default/files/media/SucroseConversionTableXV.pdf (last access: 11 September 2025), 2025.
Vennes, B. and Preston, T. C.: Calculating and fitting morphology-dependent resonances of a spherical particle with a concentric spherical shell, J. Opt. Soc. Am. A, 36, 2089, https://doi.org/10.1364/JOSAA.36.002089, 2019.
Vu, T. V., Delgado-Saborit, J. M., and Harrison, R. M.: A review of hygroscopic growth factors of submicron aerosols from different sources and its implication for calculation of lung deposition efficiency of ambient aerosols, Air Qual Atmos Health, 8, 429–440, https://doi.org/10.1007/s11869-015-0365-0, 2015.
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, e2210481119, https://doi.org/10.1073/pnas.2210481119, 2022.
Wexler, A. S. and Clegg, S. L.: Atmospheric aerosol models for systems including the ions H+, NH
Yao, Y., Curtis, J. H., Ching, J., Zheng, Z., and Riemer, N.: Quantifying the effects of mixing state on aerosol optical properties, Atmos. Chem. Phys., 22, 9265–9282, https://doi.org/10.5194/acp-22-9265-2022, 2022.
Young, T. F. and Smith, M. B.: Thermodynamic properties of mixtures of electrolytes in aqueous solutions, J. of Phys., 58, 716–724, https://doi.org/10.1021/j150519a009, 1954.
Zardini, A. A., Sjogren, S., Marcolli, C., Krieger, U. K., Gysel, M., Weingartner, E., Baltensperger, U., and Peter, T.: A combined particle trap/HTDMA hygroscopicity study of mixed inorganic/organic aerosol particles, Atmos. Chem. Phys., 8, 5589–5601, https://doi.org/10.5194/acp-8-5589-2008, 2008.
Zhao, W., Cai, C., Zhao, G., and Zhao, C.: Design of Bessel Beam Optical Tweezers for Single Particle Study, Acta Scientiarum Naturalium Universitatis Pekinensis, 56, 1031–1037, https://doi.org/10.13209/j.0479-8023.2020.090, 2020.
Short summary
Aerosols change their size and optical properties with humidity, influencing clouds and climate. Traditional instruments only capture the average behavior of many particles, missing how individual ones grow. We developed a precise optical method that traps and measures single particles as humidity varies, accurately determining their dry size and water uptake. This versatile approach applies to diverse particle types and enhances understanding of their roles in air quality and climate systems.
Aerosols change their size and optical properties with humidity, influencing clouds and climate....
