This study presents comprehensive observations combining dual-wavelength lidars (355 nm and 532 nm), ground-based aerosol composition measurements, and gaseous pollutant monitoring during a prolonged dust event from March 15 to 18, 2021, over northern China. Our lidar observations revealed that dust particles became increasingly spherical during transport (particle depolarization ratio decreased from 0.24 to 0.12), indicating progressive coating by anthropogenic aerosols. Concurrently, anthropogenic aerosol mass in PM₂.₅ decreased by 78%, primarily through coating onto coarse dust particles and subsequent enhanced deposition. To evaluate SO₂ conversion, we introduced the SO₂/CO ratio, which increased from 4.33 to 5.46 ppb ppm⁻¹ during dust periods across 977 stations, indicating weakened SO₂ conversion. This was attributed to sharply decreased relative humidity (72.07% to 39.58%), which suppressed heterogeneous SO₂ reactions on dust surfaces. Results demonstrate competing processes: physical scavenging removes existing aerosols while low RH suppresses new aerosol formation, with RH as the critical modulating factor.

Lidar,Dust-Anthropogenic Pollutant Interactions,Relative Humidity,Aerosol Scavenging,SO₂ Heterogeneous Conversion