Journal cover Journal topic
Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
Atmos. Chem. Phys., 16, 13035-13047, 2016
https://doi.org/10.5194/acp-16-13035-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
21 Oct 2016
The effect of viscosity and diffusion on the HO2 uptake by sucrose and secondary organic aerosol particles
Pascale S. J. Lakey1,2, Thomas Berkemeier2, Manuel Krapf3, Josef Dommen3, Sarah S. Steimer3, Lisa K. Whalley1,4, Trevor Ingham1,4, Maria T. Baeza-Romero5, Ulrich Pöschl2, Manabu Shiraiwa2,6, Markus Ammann3, and Dwayne E. Heard1,4 1School of Chemistry, University of Leeds, Woodhouse Lane, Leeds, LS2 9JT, UK
2Multiphase Chemistry Department, Max Planck Institute for Chemistry, Hahn-Meitner-Weg 1, 55128 Mainz, Germany
3Paul Scherrer Institute, Villigen, Switzerland
4National Centre for Atmospheric Chemistry, University of Leeds, Woodhouse Lane, Leeds, LS2 9JT, UK
5Escuela de Ingeniería Industrial de Toledo, Universidad de Castilla la Mancha, Avenida Carlos III s/n Real Fábrica de Armas, 45071 Toledo, Spain
6Department of Chemistry, University of California, Irvine, CA 92617, USA
Abstract. We report the first measurements of HO2 uptake coefficients, γ, for secondary organic aerosol (SOA) particles and for the well-studied model compound sucrose which we doped with copper(II). Above 65 % relative humidity (RH), γ for copper(II)-doped sucrose aerosol particles equalled the surface mass accommodation coefficient α  =  0.22 ± 0.06, but it 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 and the contribution of a surface reaction, as demonstrated using the kinetic multilayer model of aerosol surface and bulk chemistry (KM-SUB). At high RH the total uptake was driven by reaction in the near-surface bulk and limited by mass accommodation, whilst at low RH it was limited by surface reaction. SOA from two different precursors, α-pinene and 1,3,5-trimethylbenzene (TMB), was investigated, yielding low 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 an HO2 + RO2 reaction occurring within the aerosol particles.

Citation: Lakey, P. S. J., Berkemeier, T., Krapf, M., Dommen, J., Steimer, S. S., Whalley, L. K., Ingham, T., Baeza-Romero, M. T., Pöschl, U., Shiraiwa, M., Ammann, M., and Heard, D. E.: The effect of viscosity and diffusion on the HO2 uptake by sucrose and secondary organic aerosol particles, Atmos. Chem. Phys., 16, 13035-13047, https://doi.org/10.5194/acp-16-13035-2016, 2016.
Publications Copernicus
Download
Short summary
Chemical oxidation in the atmosphere removes pollutants and greenhouse gases but generates undesirable products such as secondary organic aerosol. Radicals are key intermediates in oxidation, but how they interact with aerosols is still not well understood. Here we use a laser to measure the loss of radicals onto oxidised aerosols generated in a smog chamber. The loss of radicals was controlled by the thickness or viscosity of the aerosols, confirmed by using sugar aerosols of known thickness.
Chemical oxidation in the atmosphere removes pollutants and greenhouse gases but generates...
Share