Vertical concentration of air pollutants based on unmanned aerial vehicle measurements during the winter period in South Korea

Air pollutant dynamics are influenced by various factors, leading to complex physical and chemical interactions in the atmosphere. Unmanned aerial vehicles (UAVs) enable high-resolution measurements of spatiotemporal variability in air quality across different altitudes and locations. However, comprehensive studies that integrate vertical measurements with detailed analyses of meteorological conditions and impacts of transboundary pollution are lacking. We investigated the relationship between air pollution concentrations measured by UAVs during winter and various meteorological factors. We evaluated the relationship between irradiance and surface wind based on the measured concentrations of gaseous pollutants such as CO, NO₂, O₃, and SO₂, as well as particulate pollutants such as PM_2.5. The influence of long-range transport was assessed by clustering the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) backward air trajectories. Photochemical reactions were most active in the afternoon, resulting in decreased concentrations of CO and NO₂, whereas O₃ concentrations increased. While CO and NO₂ concentrations were influenced by road traffic and the surrounding urban environment, those of O₃ and PM_2.5 were affected by long-range transport. High concentrations of CO, NO₂, SO₂, and PM_2.5 were observed during periods of atmospheric stagnation. This study provides a comprehensive analysis of the relationships among winter air pollutant concentrations, photochemical reactions, atmospheric stagnation, and long-range transport.