Ponente
Descripción
Atmospheric pollution is an important issue in urban areas, posing a major threat to health and climate. Streets, where populations are exposed, often present high concentrations of nitrogen oxides and fine particles composed by black carbon, organic and inorganic compounds. These pollutants may have important effects on human health, including asthma and cancer. Here, multi-scale simulations are performed over Paris city to calculate pollutant concentrations in the urban background (with the regional-scale model Polair3D) and in the streets (with the local-scale model MUNICH). Gas-phase chemistry and the formation of secondary aerosols are taken into account at both scales. Different aspects are investigated: ($i$) the difference between particle concentrations, size distribution and chemical compositions in the urban background and in the streets, ($ii$) the formation of secondary particles in the streets, and their influence in the total fine particle concentrations, ($iii$) the influence of non-exhaust emissions on black carbon concentrations. Simulations indicate that the ratio between concentrations in the streets and in the urban background can be, in average, 2 regarding nitrogen dioxide, 3 regarding black carbon and 1.8 regarding organic particles. Particle concentrations may also have more dangerous health impacts in the streets than in the urban background due to their size distribution, and to their chemical composition. Secondary particles represent an important average parcel of particle concentrations in the streets, and can reach until 18% of fine particles in Paris, depending on the street. A large contribution is observed regarding organic fine particles (reaching 38% according to the street). Traffic-related emissions of ammoniac may contribute by up to 26% of fine inorganic particle concentrations in the streets of Paris. Traffic exhaust emissions are not strong enough to explain the high black carbon concentrations observed in the streets, and non-exhaust emissions from tyre wear may need to be revisited.
