Coupling aerosol surface and bulk chemistry with a kinetic double layer model (K2-SUB): oxidation of oleic acid by ozone

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 model formulations. <br><br> 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<sup>−11</sup> cm<sup>2</sup> s<sup>−1</sup> 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

Kinetic multi-layer model of aerosol surface and bulk chemistry (KM-SUB): the influence of interfacial transport and bulk diffusion on the oxidation of oleic acid by ozone

“…We demonstrate the applicability of KM-SUB for a common model system of organic aerosol chemistry, the ozonolysis of oleic acid droplets (e.g., Moise and Rudich, 2002;Katrib et al, 2004Katrib et al, , 2005King et al, 2004King et al, , 2009Knopf et al, 2005;Ziemann, 2005;Hearn and Smith, 2007;Pfrang et al, 2009;Sage et al, 2009;Vesna et al, 2009), and we compare the results of our numerical simulations with the results of earlier experimental and theoretical studies of this system.…”

“…Chemical reactions can occur both at the surface and in the bulk of liquid and (semi-)solid particles. It is often difficult to discriminate surface and bulk reactions, and the relative importance of surface and bulk processes is not well understood (e.g., Moise and Rudich, 2000;Hearn et al, 2005;Pfrang et al, 2009). Resistor model formulations are widely used to describe and investigate heterogeneous reactions and multiphase processes in laboratory, field and model studies of atmospheric chemistry (Hanson, 1997;Finlayson-Pitts and Pitts, 2000;Worsnop et al, 2002;Anttila et al, 2006;King et al, 2008King et al, , 2009and references therein).…”

“…Shiraiwa et al (2009) presented a kinetic double-layer surface model (K2-SURF) and master mechanism for the degradation of a wide range of polycyclic aromatic hydrocarbons (PAHs) by multiple photo-oxidants (O 3 , NO 2 , OH and NO 3 ) through different types of parallel and sequential surface reactions. Pfrang et al (2009) developed a kinetic double-layer model coupling aerosol surface and bulk chemistry (K2-SUB), in which mass transport and chemical reactions in the particle are not explicitly resolved but represented by a reacto-diffusive flux (Danckwerts, 1951;Hanson, 1997).…”

Amorphous and crystalline aerosol particles interacting with water vapor: conceptual framework and experimental evidence for restructuring, phase transitions and kinetic limitations

“…With regard to unraveling the molecular mechanisms and kinetics of water uptake/evaporation and deliquescence/efflorescence of both amorphous and crystalline particles, we suggest that a clear distinction between surface and bulk processes is important and that relevant information can be obtained by highprecision H-TDMA measurements (including h&d experiments). Besides water uptake, low molecular diffusivity in (semi-)solid amorphous phases may also retard the uptake of gaseous photo-oxidants and the chemical transformation of aerosol particles and components (Smith et al, 2003;Katrib et al, 2005;Pöschl, 2005;Ammann and Pöschl, 2007;Pöschl et al, 2007;McNeill et al, 2008;Griffiths et al, 2009;Hallquist et al, 2009;Pfrang et al, 2009;Shiraiwa et al, 2009). …”

Kinetic double-layer model of aerosol surface chemistry and gas-particle interactions (K2-SURF): Degradation of polycyclic aromatic hydrocarbons exposed to O<sub>3</sub>, NO<sub>2</sub>, H<sub>2</sub>O, OH and NO<sub>3</sub>

“…(4) Surface-bulk exchange as well as mass transport and chemical reactions might also play a role for liquid substrates. Further investigations will be needed to resolve these issues, and we are planning to pursue such investigations using K2-SURF as well as kinetic double-and multi-layer models that resolves also diffusion and reaction in the bulk of the particle or substrate, respectively (K2-SUB, Pfrang et al, 2009;KM-SUB, Shiraiwa et al, 2009). …”