title: Modelling city-scale facade leaching of biocide by rainfall.
abstract: A methodology is presented for estimating, at the city scale, the amount of biocide released from facades during rain events. The methodology consists of two elements. First, leaching of a single facade is simulated using a two-region model, one region for the biocide in the facade and the other for that in the flow over the facade surface. In the latter region, water advection moves the biocide to the base of the facade, and so into the environment. Rates of detachment and deposition define the exchange process between the two regions. The two-region model was calibrated on laboratory data, and afterward applied at city scale to Lausanne, Switzerland (200,000 inhabitants). The city-scale application uses the second element of the methodology, which consists of an estimate of the exposure of the city's facades to rainfall, and relating that rainfall to the over-facade flow in the calibrated single-facade model. This results in a straightforward translation of over-facade flow volume to facade paint age, a necessary connection since facade leaching is dependent on paint age. For Lausanne, it was estimated that approximately 30% of the mass of biocides applied annually is released into the environment.
authors.affiliation: Laboratoire de Technologie Ecologique, Institut d'Ingénierie de l'Environnement, Faculté de l'Environnement Naturel, Architectural et Construit-ENAC, Station 2, Ecole Polytechnique Fédérale de Lausanne-EPFL, 1015 Lausanne, Switzerland. sylvain.coutu@epfl.ch
authors.forename: Sylvain
authors.initials: S
authors.lastname: Coutu
authors.forename: Chiara
authors.initials: C
authors.lastname: Rota
authors.forename: Luca
authors.initials: L
authors.lastname: Rossi
authors.forename: D A
authors.initials: DA
authors.lastname: Barry
mesh_terms: D002947:Cities; D003198:Computer Simulation; D003252:Construction Materials; D004202:Disinfectants; D008962:Models, Theoretical; D011891:Rain; D013557:Switzerland; D014874:Water Pollutants, Chemical
chemical_list: D004202:Disinfectants; D014874:Water Pollutants, Chemical