The impact of soot particles on public health and climate strongly depends on the per-particle composition, which may be significantly affected by heterogeneous chemical reactions. Here, we consider soot particles coated with polycyclic aromatic hydrocarbons (PAHs) in a polluted urban scenario. We use the particle-resolved aerosol model PartMC-MOSAIC to simulate heterogeneous chemistry on individual particles, focusing on the interaction of the major atmospheric oxidants (O3 , NO2 , OH, and NO3) with PAHs, including competitive co-adsorption of water vapor. PAH half-lives are on the order of seconds during the night, when the PAHs are rapidly oxidized by the gas-surface reaction with NO3. During the day, PAH half-lives are on the order of minutes and determined mostly by the surface layer reaction of PAHs with adsorbed O3. Despite its high reactivity, OH appears to have a negligible effect on PAH degradation due to its very low concentration in the atmosphere.

Particle-resolved modeling of the heterogeneous oxidation of soot surfaces

248th National Meeting (2014)

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