藏东南色季拉山土壤中有机氯农药和多环芳烃的浓度分布及来源解析

Distribution and Source Analysis of Polycyclic Aromatic Hydrocarbons(PAHs)and Organochlorine Pesticides(OCPs) in Soils from Shergyla Mountain,Southeast Tibetan Plateau

2012年8月采集了藏东南色季拉山阴坡和阳坡的土壤样品,测定了其中多环芳烃和有机氯农药(包括六六六和滴滴涕)的污染含量.土壤中Σ_(16)PAHs的含量范围为99.3~1 984 ng·g^(-1),平均值为1 017 ng·g^(-1);HCHs和DDTs的含量分别为0.37~2.07 ng·g^(-1)(平均值为1.15 ng·g^(-1))和0.70~43.9 ng·g^(-1)(平均值为9.87 ng·g^(-1)),均远高于青藏高原中部及西部土壤中相应污染物的含量,PAHs甚至可高达两个数量级.阳坡α-HCH和DDTs的浓度随着海拔升高,而阴坡HCHs和DDTs的浓度随着海拔降低或无显著变化.阴坡土壤PAHs随海拔无升高或降低的变化趋势,而阳坡土壤PAHs的浓度在低海处呈现较高浓度,可能是存在局部污染源的排放.PAHs的组成以较轻组分(2和3环)为主,平均占总含量的85%以上,说明研究区域的PAHs主要来自大气远距离传输源.PAHs的特征单体比值表明生物质和化石燃料的低温燃烧是色季拉山PAHs的主要来源,同时阴坡也可能受到石油泄漏的影响.较低的α/γ-HCH比值表明,研究区域的HCHs主要是历史工业品HCHs和林丹共同输入的结果.p,p'-DDE/p,p'-DDT和o,p'-DDT/p,p'-DDT的比值显示,研究区域DDTs主要是由历史工业品DDTs和三氯杀螨醇共同贡献所致.根据研究区域污染物的浓度特征和藏东南的气象条件可知,研究区域的污染主要受印度季风的影响.

Soils were collected from Shergyla Mountain shade slope and south-facing slope in southeast Tibetan Plateau（ TP） in August2012 and they were measured for polycyclic aromatic hydrocarbons（ PAHs） and organochlorine pesticides（ OCPs）（ including HCHs and DDTs）. The concentrations of Σ16PAHs ranged from 99. 3 to 1 984 ng·g^（-1）dw,with a mean value of 1 017 ng·g^（-1）dw. HCHs and DDTs in soils samples were in the range of 0. 37-2. 07 ng·g^（-1）dw（ mean 1. 15 ng·g^（-1）dw） and 0. 70-43. 9 ng·g^（-1）dw（ mean9. 87 ng·g^（-1）dw）,respectively. The concentrations of all measured compounds were much higher than those in central or western TP,and the PAHs concentration was even up to two orders of magnitude. The concentrations of α-HCH and DDTs in south-facing slope increased with altitude,but HCHs and DDTs in shade slope had no significant correlation with altitude. There was no consistent increasing or decreasing trend of PAHs in shade slope with altitude,and the concentrations of PAHs in south-facing slope showed a higher value in lower altitude,indicating the existence of local pollution emissions. The PAHs profile was dominated by lighter constituents（ 2 3-ring accounted for higher than 85%）,inferring that the PAHs in the study area were largely influenced by long range atmospheric transport（ LRAT） of pollutants. The special diagnostic ratios of PAHs suggested that PAHs were mainly produced by low temperature combustion of biomass and fossil fuels,except that two sampling sites of shade slope had been possibly influenced by oil residue. The relatively low ratios of α / γ-HCH inferred HCHs in the research area was the result of the combined contribution of the historical technical HCHs and Lindan. The ratios of p,p＇-DDE / p,p＇-DDT and o,p＇-DDT / p,p＇-DDT indicated DDTs were from the combined contribution of the historical technical DDTs and dicofol. According to the profile of PAHs,HCHs and DDTs and the meteorological conditions of Shergyla Mountain,the transport of PAHs and OCPs in the study area was mainly influenced by the Indian Monsoon.