PM 2.5 removal efficiency by an urban green landscape: Effect of planting design and environmental factors

Air pollution from fine dust (PM2.5) poses severe risks to urban environments and human health in many cities, particularly in roadside areas. Urban green spaces can help reduce this pollution, but there is still limited research on the best way to design plant layouts for maximum dust removal. This study evaluated the performance of a specially designed urban garden in Bangkok, Thailand, for PM2.5 removal. A three-layer planting design, featuring species with high PM2.5 removal capacity from a screening of 73 plant species, was implemented beside a major traffic road. Measurements conducted during high-pollution periods showed an average removal efficiency of 14.89%, increasing up to 35% under high PM2.5 conditions. The garden improved microclimatic conditions, reducing air temperature by 1–2°C and increasing relative humidity by approximately 9.9%. Environmental parameters such as wind speed and direction significantly affected removal efficiency. Wind speeds between 1–3 m/s optimized dust capture, reaching efficiency levels of 15–18%, while speeds above 3.6 m/s resulted in a drop in efficiency. The annual PM2.5 dry deposition rate was calculated at 1.33 g/m2 ·y. These results demonstrate that strategic planting design and species selection can enhance nature-based solutions for urban air quality improvement.Implications: This study demonstrated that a newly designed urban green space can significantly reduce roadside PM2.5, especially during high-pollution periods. Using a multi-layer planting structure and species with high PM2.5 removal capacity, the garden achieved up to 35% reduction and accumulated substantial annual particulate matter. Seasonal wind patterns were also key determinants of removal efficiency. These results provide practical guidance for municipalities and urban planners seeking cost-effective, nature-based solutions for air quality improvement. Integrating targeted green infrastructure into urban design can enhance public health protection and strengthen long-term air pollution management.