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Kinetic Multilayer Modeling of Indoor Surface Chemistry: Organic Film Formation, Bleach Cleaning Chemistry and Surface Interactions
MANABU SHIRAIWA, Pascale Lakey, University of California, Irvine
Abstract Number: 246
Working Group: Indoor Aerosols
Abstract
As part of the Modeling Consortium for Chemistry of Indoor Environments (MOCCIE), we apply kinetic multilayer models to gain fundamental and quantitative understanding of various surface processes indoors. We developed a new model to simulate the initial film formation by treating gas-phase diffusion and turbulence through a surface boundary layer and multi-layer reversible adsorption on rough surfaces, as well as subsequent film growth by resolving bulk diffusion and chemical reactions in a film. The model shows that the films should initially be patchy with the formation of pyramid-like structures on the surface. Sensitivity tests showed that highly turbulent conditions can lead to the film growing by more than a factor of two compared to low turbulence conditions. If surface films adopt an ultra-viscous state, a significant decrease in film growth is expected. The presence of chemical reactions in the film has the potential to increase the rate of film growth by nearly a factor of two. In addition, we simulated the formation and loss of species in the gas phase upon floor-bleaching as measured during the HOMEChem campaign. The model includes a boundary layer next to the bleach and reactions occurred in the aqueous bleach, in the gas phase and on aerosol particles and room surfaces. The model was able to reproduce the loss of ammonia and the formation of chloramines. We also discuss spatial and temporal scales of indoor constituents, as modulated by rates of chemical reactions, surface interactions and building ventilation.