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Theses

Modélisation de la qualité de l'air dans les rues de Paris

Abstract : In order to model the pollutant concentrations related to air quality in the streets of Paris, the street network model MUNICH (Model of Urban Network of Intersecting Canyons and Highways) is improved. A non-stationary approach is developed to represent the formation of secondary compounds, such as NO2. To model the dynamics of aerosols, MUNICH is coupled to the SSH-aerosol chemical module. The gas and particle concentrations in the streets of Paris are simulated with MUNICH, coupled to the chemical-transport model Polair3D to integrate background concentrations in the streets.For gaseous compounds, the coupling between MUNICH and Polair3D can be unidirectional (background concentrations influence those of the streets) or bidirectional (there is feedback between the street and the background concentrations). The concentrations of NO2 and NOx compare well with observations, regardless of the approach used for the coupling. The bidirectional coupling influences more the streets with an intermediate ratio between height and width, and with high traffic emissions, reaching 60% for the NO2 concentrations depending on the street. For particles, the concentrations of PM2.5, PM10 and the simulated chemical compositions are close to observations. Secondary particles have a significant impact on PM2.5 concentrations, reaching 27% depending on the street and the time of day. Gaseous chemistry has a strong influence on reactive gaseous species, increasing the average concentration of NO2 by 37%. The influence on condensables is lower, but reaches 20% depending on the street. The thermodynamic equilibrium assumption in the condensation/evaporation calculation overestimates organic concentrations by around 5% on average, up to 31% at noon depending on the street. NH3 traffic emissions increase inorganic concentrations by 3% on average, reaching 26% depending on the street.To explain the model's underestimation of the high black carbon (BC) concentrations observed in the streets, the influence of non-exhaust emissions and the bidirectional coupling is investigated. A new approach to calculate particle resuspension is developed, modeling the deposited mass and respecting the mass balance on the surface of the streets. Simulations show that particle resuspension has a low impact on BC concentrations. The concentrations of BC in the streets influence the background urban concentrations: the influence of bidirectional coupling reaches 50% depending on the street. Tyre wear emissions contribute to BC emissions in a comparable way to exhaust emissions. New emission factors are proposed, consistent with studies in the literature and the model/measurement comparison carried out here.MUNICH is finally used in Paris to estimate the impact of the vehicle fleet renewal over ten years and urban mobility on the population's exposure to multiple compounds. The vehicle fleet renewal strongly decreases the population's exposure to NO2, BC, PM10, PM2.5 and organic particles. This decrease is greater than that estimated using a regional CTM. The population's exposure to PM2.5 decreases similarly if recent diesel, gasoline or electric vehicles are favored. But favoring electric vehicles induces the greatest reduction in population exposure to NO2. Home-office practice is less efficient than renewing vehicles, but it can be used to intensify the decrease in population exposure to particulate matter concentrations. However, more ambitious emission reductions are needed to meet the air quality guidelines in Paris
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Submitted on : Monday, December 6, 2021 - 3:21:09 PM
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Lya Lugon Cornejo von Marttens. Modélisation de la qualité de l'air dans les rues de Paris. Sciences de la Terre. École des Ponts ParisTech, 2021. Français. ⟨NNT : 2021ENPC0011⟩. ⟨tel-03467496⟩

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