Impacts of wind fields on the distribution patterns of traffic emitted particles in urban residential areas

Traffic emissions are a major contributor to urban atmospheric pollution. The wind fields also play an important role in the dispersion of air pollutants from the traffic emissions. However, the effects of different regional wind fields on the diffusion patterns of traffic-emitted fine particulate matter (PM2.5) in urban areas are still unclear and lack quantified measurements. To provide guidance to urban planning and design, as well as urban governance and management, it is especially important to identify the extent to which wind fields affect the diffusion of traffic emitted particles. To understand the effect, field measurements and numerical simulations were conducted in this study. The field measurements mainly focused on collecting three-dimensional (3D) distributions of concentrations of traffic-emitted particles in a student dormitory zone at a university using instrumented unmanned aerial vehicles (UAVs). The collected PM2.5 measurements were used to verify and calibrate numerical models. Then, computational fluid dynamics (CFD) simulations were used to track the progress of pollutant dispersion and evaluate its relationship to urban forms. The effects of different wind directions (northwest and southeast) on the distribution and deposition of the traffic-emitted particles in the residential area were studied under different wind velocity conditions (1 m s(-1), 5 m s(-1) and 20 m s(-1)). As efficient observation platforms, the UAVs employed in the study allowed the capture of the 3D variations in the distributions of atmospheric pollutants in urban areas. The result provides a better understanding of the dispersion of atmospheric pollutants in a specific urban built environment under different wind fields, which can support urban governance and planning and design practice leading to effective mitigation of traffic-induced air pollution in urban areas.