Experimental determination of chemical diffusion within secondary organic aerosol particles

Abstract. Secondary Organic Aerosol (SOA) particles have been found to be efficient ice nucleating particles under the cold conditions of (tropical) upper tropospheric cirrus clouds. Whether they also are efficient at initiating freezing at slightly warmer conditions as found in mixed phase clouds remains undetermined. Here, we study the ice nucleating ability of photo-chemically produced SOA particles with the combination of the Manchester Aerosol and Ice Cloud Chambers. Three SOA systems were tested resembling biogenic/anthropogenic particles and particles of different phase state. After the aerosol particles were formed, they were transferred into the cloud chamber where subsequent quasi-adiabatic cloud evacuations were performed. Additionally, the ice forming abilities of ammonium sulfate and kaolinite were investigated as a reference to test the experimental setup. Clouds were formed in the temperature range of −20 °C to −28.6 °C. Only the reference experiment using dust particles showed evidence of ice nucleation. No ice particles were observed in any other experiment. Thus, we conclude that SOA particles produced under the conditions of the reported experiments are not efficient ice nucleating particles starting at liquid saturation under mixed-phase cloud conditions.

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An amorphous solid state of biogenic secondary organic aerosol particles

Nature ◽

10.1038/nature09455 ◽

2010 ◽

Vol 467 (7317) ◽

pp. 824-827 ◽

Cited By ~ 560

Author(s):

Annele Virtanen ◽

Jorma Joutsensaari ◽

Thomas Koop ◽

Jonna Kannosto ◽

Pasi Yli-Pirilä ◽

...

Keyword(s):

Solid State ◽

Secondary Organic Aerosol ◽

Aerosol Particles ◽

Amorphous Solid ◽

Organic Aerosol

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The effect of viscosity on the HO<sub>2</sub> uptake by sucrose and secondary organic aerosol particles

10.5194/acp-2016-284 ◽

2016 ◽

Cited By ~ 1

Author(s):

Pascale S. J. Lakey ◽

Thomas Berkemeier ◽

Manuel Krapf ◽

Josef Dommen ◽

Sarah S. Steimer ◽

...

Keyword(s):

Model Compound ◽

Secondary Organic Aerosol ◽

Aerosol Particles ◽

Organic Aerosol ◽

Liquid Water Content ◽

Accommodation Coefficient ◽

Surface Mass ◽

Mass Accommodation Coefficient ◽

Uptake Coefficients ◽

Bulk Chemistry

Abstract. We report the first measurements of HO2 uptake coefficients, γ, for secondary organic aerosol particles (SOA) and for the well-studied model compound sucrose which was doped with copper. Above 65 % relative humidity (RH), γ for copper doped sucrose aerosol particles equalled the surface mass accommodation coefficient α = 0.22 ± 0.06 but decreased to γ = 0.012 ± 0.007 upon decreasing the RH to 17 %. The trend of γ with RH can be explained by an increase in aerosol viscosity, as demonstrated using the kinetic multi-layer model of aerosol surface and bulk chemistry (KM-SUB). SOA from two different precursors, α-pinene and 1,3,5- trimethylbenzene (TMB), was investigated, yielding small uptake coefficients of γ < 0.001 and γ = 0.004 ± 0.002, respectively. It is postulated that the larger values measured for TMB derived SOA compared to α-pinene derived SOA are either due to differing viscosity, a different liquid water content of the aerosol particles or a HO2 + RO2 reaction occurring within the aerosol particles.

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