Capturing the vertical distribution of near-highway nitrogen dioxide using UAV-based measurements

This pilot study evaluates the use of Uncrewed Aerial Vehicles (UAVs) to capture variations in the transport and dispersion of nitrogen dioxide (NO 2 ) under different atmospheric dispersion conditions. The vertical distribution of NO 2 concentration was observed using an unmodified handheld electrochemical gas sensor mounted onboard a UAV, beside a major Canadian highway. Observations were taken in both poor and good dispersion conditions, as determined by the Atmospheric Dispersion Index and Ventilation Index. Results reveal atmospheric stability has a significant impact on the vertical profiles of NO 2 . The low wind speeds and limited vertical mixing experienced during poor dispersion conditions resulted in concentrations increasing with altitude, contrasting with the stable NO 2 concentrations observed during good dispersion conditions. Statistical analysis reveals significant differences between ground-level measurements and simultaneous UAV-based readings at higher altitudes during poor dispersion, suggesting the influence of regional emissions accumulating due to poor mixing. These preliminary results demonstrate the potential for UAV-based measurements in air quality management. The ability to capture nuanced dynamics such as the accumulation of regional emissions is critical when studying pollutions events such as wildfires. • Vertical profiles of NO 2 were captured near a major Canadian highway under varying atmospheric dispersion conditions. • During poor dispersion conditions, NO 2 concentrations increased with altitude, while they remained relatively stable during good dispersion. • Significant differences were observed between ground-level measurements and UAV-based observations at higher altitudes during poor dispersion, suggesting the accumulation of regional emissions.