[Distribution and source of polycyclic aromatic hydrocarbons (PAHs) in soil of east Qingzang Plateau]. 
We investigated the distribution characteristic of polycyclic aromatic hydrocarbons (PAHs) of 10 samples in five positions of east Qingzang Plateau was investigated.  The result shows total PAHs ranged from 0.83 to 14.41 ng/g, which is much lower than other places in China, and Phenanthrene is the most abundant compound.  The analysis of six sample positions in Qushui shows that they all have the same pollution source of PAHs, which is the slow maturation of organic matter under the geochemical gradient conditions except one site which is downwind beside the road and affected by the traffic pollution.  Comparing the five sites of Lhasa, Qushui, Baqing, Changdu and Ge Ermu, it shows that most of the west of Qunlun mountain (Lhasa, Qushui, Baqing and Changdu) have the same pollution source of PAHs, which is also the slow maturation of organic matter under the geochemical gradient conditions, and because of the character of soil, the obstruct of Qunlun mountain and other reasons, the PAHs in the desert of Ge Ermu is affected by pyrolytic origin.