Shiraiwa, M., Pfrang, C., Koop, T. and Poschl, U.
Kinetic multi-layer model of gas-particle interactions in aerosols and clouds (KM-GAP): linking condensation, evaporation and chemical reactions of organics, oxidants and water.
Atmospheric Chemistry and Physics, 12 (5).
To link to this article DOI: 10.5194/acp-12-2777-2012
We present a novel kinetic multi-layer model
for gas-particle interactions in aerosols and clouds (KMGAP)
that treats explicitly all steps of mass transport and
chemical reaction of semi-volatile species partitioning between
gas phase, particle surface and particle bulk. KMGAP
is based on the PRA model framework (P¨oschl-Rudich-
Ammann, 2007), and it includes gas phase diffusion, reversible
adsorption, surface reactions, bulk diffusion and reaction,
as well as condensation, evaporation and heat transfer.
The size change of atmospheric particles and the temporal
evolution and spatial profile of the concentration of individual
chemical species can be modeled along with gas uptake
and accommodation coefficients. Depending on the complexity
of the investigated system and the computational constraints,
unlimited numbers of semi-volatile species, chemical
reactions, and physical processes can be treated, and the
model shall help to bridge gaps in the understanding and
quantification of multiphase chemistry and microphysics in
atmospheric aerosols and clouds.
In this study we demonstrate how KM-GAP can be used
to analyze, interpret and design experimental investigations
of changes in particle size and chemical composition in response
to condensation, evaporation, and chemical reaction.
For the condensational growth of water droplets, our kinetic
model results provide a direct link between laboratory observations
and molecular dynamic simulations, confirming
that the accommodation coefficient of water at 270K is
close to unity (Winkler et al., 2006). Literature data on the
evaporation of dioctyl phthalate as a function of particle size
and time can be reproduced, and the model results suggest
that changes in the experimental conditions like aerosol particle
concentration and chamber geometry may influence the
evaporation kinetics and can be optimized for efficient probing
of specific physical effects and parameters. With regard
to oxidative aging of organic aerosol particles, we illustrate
how the formation and evaporation of volatile reaction products
like nonanal can cause a decrease in the size of oleic acid
particles exposed to ozone.
|Date Deposited:||11 Apr 2012 14:50|
|Last Modified:||18 Oct 2013 09:50|
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