To develop sustainable cities, urban mitigation policies reduced pollutant emissions and increased the number of vegetated areas to reduce urban heat islands, counteract carbon emissions, and improve air quality. But the impact of green infrastructures on secondary pollutants (formed in the air) remains poorly understood. Urban vegetated areas are a source of Biogenic Volatile Organic Compounds (BVOCs) that can react with the atmospheric oxidants, leading to the formation of Secondary Organic Aerosols (SOAs), one of the dominant fractions of atmospheric aerosols (particles suspended in air), that induce adverse health effects on human health. Currently, the impact of green infrastructures on SOAs is highly uncertain, because of the lack of knowledge regarding BVOC emissions from urban vegetated areas and the processes at the origin of SOA formation (in particular when mixed with anthropogenic emissions), pointing to urgent need for new studies on this topic. The general aim of VesPA (impact of Vegetated areas on Secondary Pollutants levels in urban Air) is to assess the contribution of vegetated urban areas to SOA levels in cities. This project will thus focus on SOA generated by BVOC emissions in urban areas through two main research tasks. The first one will characterize BVOC emissions from plant scale up to the district scale. The second task will investigate the reactivity and the potential SOA formation of these BVOC emissions, especially when they are mixed with anthropogenic VOCs. This original approach combines field and laboratory experiments, and will be developed in Marseilles, which gathers many advantages for the project. VeSPA will ultimately provide new knowledge to help developing future sustainable cities, in terms of urban air quality in the context of climate change.