Observation of viscosity transition in α-pinene secondary organic aerosol

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 occ
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.
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Author:Emma Järvinen, Karoliina Ignatius, Leonid Nichman, Thomas Bjerring Kristensen, Claudia Fuchs, Christopher Robert Hoyle, Niko Florian Höppel, Joel C. Corbin, Jill Craven, Jonathan Duplissy, Sebastian Ehrhart, Imad El Haddad, Carla Frege, Hamish Gordon, Tuija Jokinen, Peter Kallinger, Jasper Kirkby, Alexei Kiselev, Karl-Heinz Naumann, Tuukka Petäjä, Tamara Pinterich, André Stephan Henry Prévôt, Harald Saathoff, Thea Schiebel, Kamalika Sengupta, Mario Simon, Jay G. Slowik, Jasmin Tröstl, Annele Virtanen, Paul Vochezer, Steffen Vogt, Andrea Christine Wagner, Robert Wagner, Christina Williamson, Paul M. Winkler, Chao Yan, Urs Baltensperger, Neil McPherson Donahue, Rick C. Flagan, Martin William Gallagher, Armin Hansel, Markku Kulmala, Frank Stratmann, Douglas R. Worsnop, Ottmar Möhler, Thomas Leisner, Martin Schnaiter
URN:urn:nbn:de:hebis:30:3-418910
URL:http://www.atmos-chem-phys.net/16/4423/2016
DOI:http://dx.doi.org/10.5194/acp-16-4423-2016
ISSN:1680-7324
ISSN:1680-7316
Parent Title (English):Atmospheric chemistry and physics
Publisher:European Geosciences Union
Place of publication:Katlenburg-Lindau
Contributor(s):Thomas Koop
Document Type:Article
Language:English
Date of Publication (online):2016/11/17
Date of first Publication:2016/04/11
Publishing Institution:Universitätsbibliothek Johann Christian Senckenberg
Release Date:2016/11/17
Volume:16
Issue:7
Pagenumber:16
First Page:4423
Last Page:4438
Note:
© Author(s) 2016. CC Attribution 3.0 License.
HeBIS PPN:424004135
Institutes:Geowissenschaften
Dewey Decimal Classification:550 Geowissenschaften
Sammlungen:Universitätspublikationen
Licence (German):License LogoCreative Commons - Namensnennung 3.0

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