Sixteen tree bark samples were collected from Yunnan Province in August 2012 and analyzed for polycyclic aromatic hydrocarbons (PAHs) and organochlorine pesticides (OCPs) including HCHs and DDTs. The concentrations of Sigma_(16)PAH ranged from 317 to 1194 ng·g~(-1),with a mean value of 639 ng·g~(-1). Sigma_4HCH and Sigma_6DDT in bark samples were in the range of 0.10 3.86 ng·g~(-1) dw (mean 1.10 ng·g~(-1) dw) and 0.787.29 ng·g~(-1) dw (mean 3.32 ng·g~(-1) dw), respectively. The concentrations of PAHs were 23 times higher than those from Nyingchi,but the concentrations of HCHs and DDTs were lower than those from Nyingchi in southeast TP. The distribution of POPs in the study area was influenced by the lipid content in bark,but not significantly. Meanwhile HCHs,DDTs,2 ring and 3 ring PAHs increased with altitude,showing a typical mountain cold-trapping effect; 4 ring,5 ring,and 6 ring PAHs decreased with altitude, which may be caused by the local pollution sources in the study area. Lower molecular weight PAHs (23 rings) were the dominant PAHs which accounted for 77% of the total PAHs on average, indicating the significant influence of long-range atmospheric transport (LRAT) in the study area. The special diagnostic ratios of PAHs suggested that the PAHs in the study area were mainly produced by low temperature combustion of biomass (grass or /and wood) and coal fuels,and the relatively low ratios of alpha/gamma-HCH and high ratios of o,p'-DDT /p,p'-DDT implied that widely applications of lindane and dicofol contributed to the OCPs contamination in this area. According to the backward airmass trajectory models and distribution of PAHs and OCPs,it was deduced that the OCPs were mainly influenced by the westerly wind and Indian Monsoon,and the PAHs were the results of the interaction between the long-range atmospheric transport and the local pollution sources in Yunnan Province.
