Abstract: To investigate regional distribution,sources and atmospheric transport of persistent organic pollutants (POPs),a passive air sampling campaign was carried out from July 2006 to June 2008 synchronously in Changdao and Tianjin.Based on GC/HRMS analytical data,it was revealed that the relative compositions of organochlorine pollutants (OCPs) including HCB,HCHs,DDTs,PCB28 and PCB52 had substantial seasonal variations.Passive air samples were classified by Cluster Analysis according to season rather than site functionalities,implying strong regional properties of organochlorine pollution.Sites in Tianjin and Changdao,which are 400 kilometers apart,had very similar chemical composition,which can only be attributed to effective diffusion and long-distance transport.DDTs emissions from sources including industrial sites in Tianjin and the usage of DDTs-containing antifouling paints in harbors and dockyards in Changdao could be identified by scrutinizing the composition data and Cluster Analysis.Indeed,the chemical composition of organochlorine pollutants can be used as a fingerprint or a probe to investigate air pollution transport and spatial distribution.