云南省树皮样品中多环芳烃和有机氯农药的浓度分布及来源解析

Distribution and source analysis of polycyclic aromatic hydrocarbons( PAHs) and organochlorine pesticides( OCPs)in the tree bark from Yunnan Province

2012年8月于云南省采集了16个树皮样品,分析了其中多环芳烃和有机氯农药(包括六六六和滴滴涕)的浓度水平和分布特征.树皮中∑_(16)PAH的浓度范围为317—1194 ng·g^(-1),平均值为639 ng·g~^(-1);研究区域树皮中∑_4HCH和∑_6DDT的浓度分别为为0.10—3.86 ng·g^(-1)干重(平均值为1.10 ng·g^(-1)干重)和0.78—7.29 ng·g^(-1)干重(平均值为3.32 ng·g^(-1)干重),PAHs浓度是藏东南林芝地区的2—3倍,而有机氯农药的浓度低于藏东南林芝地区.树皮中脂肪可影响研究区域持久性有机污染物(Persistent organic pollutants,POPs)的分布,但影响不显著.同时HCHs、DDTs和2环及3环PAHs的浓度随海拔的升高而增加,呈典型的高山冷捕获效应;4环、5环和6环PAHs的浓度随着海拔的升高而降低,这可能是云南本地污染源影响所致.较低质量的PAHs(2—3环)是研究区域PAHs的重要组成部分,平均占总浓度的77%以上,说明研究区域受到污染物大气远距离传输的重要影响.PAHs特征单体比值表明,草、木材等生物质和煤炭燃料等的低温燃烧是研究区域PAHs的主要来源,同时较低的α/γ-HCH和较高的o,p'-DDT/p,p'-DDT比率表明,林丹和三氯杀螨醇的使用对研究区域树皮中有机氯农药的污染有一定的贡献.根据反向气团轨迹模型及PAHs和OCPs的浓度分布,推断研究区域的OCPs主要受印度季风和西风环流的影响,而PAHs是大气远距离传输源和云南本地污染源共同作用的结果.

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 ∑ 16PAH ranged from 317 to 1194 ng.g-1, with a mean value of 639 ng.g-1. ∑4HCH and ∑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 0,78--7.29 ng.g-1 dw （mean 3.32 ng.g-1 dw） , respectively. The concentrations of PAHs were 2-3 times higher than those from Nvingchi. but theconcentrations 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 （2-3 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 α/γ-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.