Abstract: The daily API (PM₁₀ is the primary pollutant) in the different seasons from March 2006 to February 2010 was analyzed for studying the regional pollution characteristics in Xining. The backward trajectory of air mass in the typical PM₁₀ pollution days that API was more than 200 was simulated based on the trajectory model (HYSPLIT 4.9) in order to discuss the possible PM₁₀ transportation path and the regional pollution source. The result showed that the serious PM₁₀ pollution appears in spring, especially in March and April, which is related to the long-distance transportation of air mass to particulate matter. Sand dust contributes largely to the serious pollution weather in Xining, and its source is located in the desert of the northern and northwestern Xining. The early or deferred API peak value in adjacent cities reflects the transportation process of regional pollution.

Key words: Xining, PM₁₀, backward trajectory, transport path, PM₁₀, Backward trajectory, Transport path, Xining