Coupling aerosol surface and bulk chemistry with a kinetic double layer model (K2-SUB): oxidation of oleic acid by ozone 1University of Reading, Department of Chemistry, P. O. BOX 224, Whiteknights, Reading RG6 6AD, UK
2Max Planck Institute for Chemistry, Biogeochemistry Department, 55128 Mainz, Germany
Received: 28 October 2009 – Published in Atmos. Chem. Phys. Discuss.: 15 December 2009 Abstract. We present a kinetic double layer model coupling aerosol surface and bulk
chemistry (K2-SUB) based on the PRA framework of gas-particle interactions
(Pöschl-Rudich-Ammann, 2007). K2-SUB is applied to a popular model system
of atmospheric heterogeneous chemistry: the interaction of ozone with oleic
acid. We show that our modelling approach allows de-convoluting surface and
bulk processes, which has been a controversial topic and remains an important
challenge for the understanding and description of atmospheric aerosol
transformation. In particular, we demonstrate how a detailed treatment of
adsorption and reaction at the surface can be coupled to a description of
bulk reaction and transport that is consistent with traditional resistor
Revised: 12 April 2010 – Accepted: 25 April 2010 – Published: 18 May 2010
From literature data we have derived a consistent set of kinetic parameters
that characterise mass transport and chemical reaction of ozone at the
surface and in the bulk of oleic acid droplets. Due to the wide range of rate
coefficients reported from different experimental studies, the exact
proportions between surface and bulk reaction rates remain uncertain.
Nevertheless, the model results suggest an important role of chemical
reaction in the bulk and an approximate upper limit of
~10−11 cm2 s−1 for the surface reaction rate coefficient.
Sensitivity studies show that the surface accommodation coefficient of the
gas-phase reactant has a strong non-linear influence on both surface and bulk
chemical reactions. We suggest that K2-SUB may be used to design, interpret
and analyse future experiments for better discrimination between surface and
bulk processes in the oleic acid-ozone system as well as in other
heterogeneous reaction systems of atmospheric relevance.
Citation: Pfrang, C., Shiraiwa, M., and Pöschl, U.: Coupling aerosol surface and bulk chemistry with a kinetic double layer model (K2-SUB): oxidation of oleic acid by ozone, Atmos. Chem. Phys., 10, 4537-4557, doi:10.5194/acp-10-4537-2010, 2010.