Modeling urban films using a dynamic multimedia fugacity model |
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Authors: | Csiszar Susan A Diamond Miriam L Thibodeaux Louis J |
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Institution: | a Department of Chemical Engineering and Applied Chemistry, University of Toronto, Toronto, ON, Canada b Department of Geography and Program in Planning, University of Toronto, Toronto, ON, Canada c Cain Department of Chemical Engineering, Louisiana State University, Baton Rouge, LA, United States |
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Abstract: | A thin film coats impervious urban surfaces that can act as a source or sink of organic pollutants to the greater environment. We review recent developments in the understanding of film and film-associated pollutant behavior and incorporate them into an unsteady-state version of the fugacity based Multimedia Urban Model (MUM), focusing on detailed considerations of surface film dynamics. The model is used to explore the conditions under which these atmospherically-derived films act as a temporary source of chemicals to the air and/or storm water. Assuming film growth of 2.1 nm d−1 (Wu et al., 2008a), PCB congeners 28 and 180 reach air-film equilibrium within hours and days, respectively. The model results suggest that the film acts as a temporary sink of chemicals from air during dry and cool weather, as a source to air in warmer weather, and as a source to storm water and soil during rain events. Using the downtown area of the City of Toronto Canada, as a case study, the model estimates that nearly 1 g d−1 of ∑5PCBs are transferred from air to film to storm water. |
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Keywords: | Surface films Multimedia modeling Unsteady-state systems Polychlorinated biphenyls Semi-volatile organic compounds Urban environment |
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