Järvinen, Emma and Craven, Jill and Flagan, Rick C. (2016) Observation of viscosity transition in α-pinene secondary organic aerosol. Atmospheric Chemistry and Physics, 16 (7). pp. 4423-4438. ISSN 1680-7324. http://resolver.caltech.edu/CaltechAUTHORS:20160412-104944600
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Under certain conditions, secondary organic aerosol (SOA) particles can exist in the atmosphere in an amorphous solid or semi-solid state. To determine their relevance to processes such as ice nucleation or chemistry occurring within particles requires knowledge of the temperature and relative humidity (RH) range for SOA to exist in these states. In the Cosmics Leaving Outdoor Droplets (CLOUD) experiment at The European Organisation for Nuclear Research (CERN), we deployed a new in situ optical method to detect the viscous state of α-pinene SOA particles and measured their transition from the amorphous highly viscous state to states of lower viscosity. The method is based on the depolarising properties of laboratory-produced non-spherical SOA particles and their transformation to non-depolarising spherical particles at relative humidities near the deliquescence point. We found that particles formed and grown in the chamber developed an asymmetric shape through coagulation. A transition to a spherical shape was observed as the RH was increased to between 35 % at −10 °C and 80 % at −38 °C, confirming previous calculations of the viscosity-transition conditions. Consequently, α-pinene SOA particles exist in a viscous state over a wide range of ambient conditions, including the cirrus region of the free troposphere. This has implications for the physical, chemical, and ice-nucleation properties of SOA and SOA-coated particles in the atmosphere.
|Additional Information:||© Author(s) 2016. This work is distributed under the Creative Commons Attribution 3.0 License. Received: 04 Sep 2015 – Published in Atmos. Chem. Phys. Discuss.: 22 Oct 2015. Revised: 08 Mar 2016 – Accepted: 29 Mar 2016 – Published: 11 Apr 2016. The CERN CLOUD experiment (ACP/AMT inter-journal SI) We would like to thank the two anonymous referees for their valuable comments. We thank CERN for supporting CLOUD with important technical and financial resources. We thank the CLOUD-TRAIN community and specially all the ITN students for their help and support. This research has received funding from the Seventh Framework Programme of the European Union (Marie Curie-Networks for Initial Training MC-ITN CLOUD-TRAIN no. 316 662), from Swiss National Science Foundation (SNSF) grant number 200021_140663, from US National Science Foundation grants AGS-1447056 and AGS-1439551, from Dreyfus Award EP-11-117, from German Federal Ministry of Education and Research BMBF (project no. 01LK1222A and B), from the Davidow Foundation, and from the funding of the German Federal Ministry of Education and Research (BMBF) through the CLOUD12 project. The article processing charges for this open-access publication were covered by a Research Centre of the Helmholtz Association. Edited by: T. Koop|
|Official Citation:||Järvinen, E., Ignatius, K., Nichman, L., Kristensen, T. B., Fuchs, C., Hoyle, C. R., Höppel, N., Corbin, J. C., Craven, J., Duplissy, J., Ehrhart, S., El Haddad, I., Frege, C., Gordon, H., Jokinen, T., Kallinger, P., Kirkby, J., Kiselev, A., Naumann, K.-H., Petäjä, T., Pinterich, T., Prevot, A. S. H., Saathoff, H., Schiebel, T., Sengupta, K., Simon, M., Slowik, J. G., Tröstl, J., Virtanen, A., Vochezer, P., Vogt, S., Wagner, A. C., Wagner, R., Williamson, C., Winkler, P. M., Yan, C., Baltensperger, U., Donahue, N. M., Flagan, R. C., Gallagher, M., Hansel, A., Kulmala, M., Stratmann, F., Worsnop, D. R., Möhler, O., Leisner, T., and Schnaiter, M.: Observation of viscosity transition in α-pinene secondary organic aerosol, Atmos. Chem. Phys., 16, 4423-4438, doi:10.5194/acp-16-4423-2016, 2016.|
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|Deposited By:||Irina Meininger|
|Deposited On:||12 Apr 2016 21:54|
|Last Modified:||12 Apr 2016 21:54|
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