Scavenging of atmospheric particulates by snow in Changji, China

Changji is an arid city in the north west of China which suffers from severe air pollution due to increasing vehicle use and heating with coal. Samples (TSP, PM10, PM5, PM2.5) were collected before and after several snow events, for revealing the snow scavenging effect and influencing mechanisms. The result indicated that the snow scavenging effect was obvious. The highest snow scavenging quantity and scavenging ratio is TSP, followed by PM10, PM5, PM2.5. Snow scavenging quantity was dependent on the particulate diameter. Snow intensity, drying time and amount of snow influenced scavenging ratio, and snow intensity is the key influencing factor. Scavenging ratio increases with the increase of snow intensity. Higher snow intensity can reduce the selective scavenging of particulate diameters, the scavenging ratio of different particulate diameter will get close to each other. The lower snow intensity was, the higher selectivity was. Light snow will scavenge large particles obviously, but little for small particle.