Three-dimensional 4-day backward trajectories arriving in Lanzhou at 500m high were calculated every 6 h by using HYSPLIT-4 trajectory model in spring of 2001 to 2008.The 8 years were divided into two categories:high dust year (2001,2002,2004 and 2006) and low dust year (2003,2005,2007 and 2008).Cluster analysis,potential source contribution function (PSCF) model,and concentration-weighted trajectory (CWT) method were used to evaluate the transportation pathways and potential source regions of Lanzhou PM₁₀ pollution in spring.Results indicate that the western and northwestern pathways,respectively accounting for 33% and 19.4% of all trajectories,were major pathways leading to high springtime PM₁₀ loadings in Lanzhou in 2001,2002,2004 and 2006.However,the major pathways were the western and the northern pathways in 2003,2005,2007 and 2008,accounting for 23.6% and 18%,respectively.There were six potential source regions that had effect on PM₁₀concentration in Lanzhou,including Tarim Basin and Turpan Basin in Xinjiang,Qaidam Basin in Qinghai,Hexi Corridor in Gansu Province,the desert and gobi area in central and western Inner Mongolia.