Three-dimensional diffusion patterns of traffic-related air pollutants on the roadside based on unmanned aerial vehicles monitoring

There are many studies on the horizontal diffusion of traffic emissions on the roadside, but not enough on the three-dimensional diffusion patterns mainly because of the lack of three-dimensional monitoring data. However, understanding three-dimensional diffusion patterns is critical because it is closely related to the health exposure of residents in roadside multi-story dwellings. Based on the unmanned aerial vehicle platform, this study carried out vertical and horizontal monitoring experiments on traffic-related air pollutants at urban intersections and suburban highways of Cangzhou city, and found that the vertical and horizontal impact ranges of black carbon and coarse particulate matter under free diffusion conditions were respectively in the vicinity of 100 m and 50 m. Compared with particles, the vertical and horizontal impact influence ranges of gaseous pollutant CO₂ are higher than black carbon and coarse particulate matters and reached 400 m and 300 m. Meanwhile, the vertical and horizontal impact influence ranges of O₃ and fine particulate matters which represented secondary air pollutants were approximately 300 m. The effect of wind can also significantly influence the impact range of various pollutants, and may lead to the transport of pollutants from the suburbs to the urban area. Furthermore, this study found that traffic participants or roadside residents in urban areas are more exposed to black carbon inhalation than those in suburban areas based on the respiratory deposition dose investigation.