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Observation of viscosity transition in α-pinene secondary organic aerosol

Järvinen, Emma; Ignatius, Karoliina; Nichman, Leonid; Kristensen, Thomas B. LU ; Fuchs, Claudia; Hoyle, Christopher R.; Höppel, Niko; Corbin, Joel C.; Craven, Jill and Duplissy, Jonathan, et al. (2016) In Atmospheric Chemistry and Physics 16(7). p.4423-4438
Abstract

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... (More)

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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@article{bafa98c6-fa74-4915-bc1b-4d17b17fd4b4,
  abstract     = {<p>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.</p>},
  author       = {Järvinen, Emma and Ignatius, Karoliina and Nichman, Leonid and Kristensen, Thomas B. and Fuchs, Claudia and Hoyle, Christopher R. and Höppel, Niko and Corbin, Joel C. and Craven, Jill and Duplissy, Jonathan and Ehrhart, Sebastian and El Haddad, Imad and Frege, Carla and Gordon, Hamish and Jokinen, Tuija and Kallinger, Peter and Kirkby, Jasper and Kiselev, Alexei and Naumann, Karl Heinz and Petäjä, Tuukka and Pinterich, Tamara and Prevot, Andre S.H. and Saathoff, Harald and Schiebel, Thea and Sengupta, Kamalika and Simon, Mario and Slowik, Jay G. and Tröstl, Jasmin and Virtanen, Annele and Vochezer, Paul and Vogt, Steffen and Wagner, Andrea C. and Wagner, Robert and Williamson, Christina and Winkler, Paul M. and Yan, Chao and Baltensperger, Urs and Donahue, Neil M. and Flagan, Rick C. and Gallagher, Martin and Hansel, Armin and Kulmala, Markku and Stratmann, Frank and Worsnop, Douglas R. and Möhler, Ottmar and Leisner, Thomas and Schnaiter, Martin},
  issn         = {1680-7316},
  language     = {eng},
  month        = {04},
  number       = {7},
  pages        = {4423--4438},
  publisher    = {Copernicus Gesellschaft mbH},
  series       = {Atmospheric Chemistry and Physics},
  title        = {Observation of viscosity transition in α-pinene secondary organic aerosol},
  url          = {http://dx.doi.org/10.5194/acp-16-4423-2016},
  volume       = {16},
  year         = {2016},
}