Effect of land use changes on air quality: impacts of urbanization, urban vegetation, and agriculture

Urbanization converts natural landscapes into impervious surfaces, altering local climate and air quality. Greening strategies are adopted to mitigate these effects, yet their effectiveness depends on land use, urban form, geography, and climate interactions. Using an air quality model with an urban canopy scheme, we evaluate how land use changes-urban expansion, agriculture, and parks-affect urban climate and chemical processes, influencing air pollutants like NO₂, O₃, VOCs, and PMs. Applied to future land-use scenarios in the Metropolitan Area of Barcelona, our results show that a 45-55% increase in urbanization raises surface temperatures and consequently evening O₃ levels by up to 8%. Replacing 6-10% of urban land and 30-40% of natural vegetation areas into agriculture reduces O₃ by up to 10%, but increases NH₃ (up to 90%) and aerosols (up to 12%). Doubling urban green spaces reduce NO₂ (up to 3%) and increases O₃ (up to 5%) and SOA (up to 14%). Our study emphasizes the trade-offs of urban greening and the need for integrated planning to improve air quality.