Impact of Urban Vegetation on Air Quality

Urban vegetation affects air quality through five main processes. First, leaves absorb and adsorb gaseous pollutants. Second, vegetation modifies wind flows and traps particles, especially using porous barriers. Third, plants emit volatile organic compounds. Fourth, they release allergenic pollen. Fifth, photosynthesis consumes CO₂. The net positive or negative impact varies with pollutant species, geographical location, seasons, urban morphology, and vegetation structures. Some green infrastructures also influence air quality via indirect effects such as shading. However, averaged across cities, the overall influence of urban vegetation on pollutant levels remains minor and often negligible.