广西大石围天坑中多环芳烃的大气传输与分异

Transport and Differentiation of Polycyclic Aromatic Hydrocarbons in Air from Dashiwei Karst Sinkholes in Guangxi,China

选择典型的岩溶地区广西乐业大石围天坑群为研究对象,利用聚氨酯泡沫被动采样器(PUF-PAS)采集大石围天坑口部至地下河剖面空气样品,并进行了气象参数的观测.利用气相色谱-质谱仪(GC-MS)测定16种多环芳烃(PAHs)优先控制污染物.结果表明,大石围天坑至地下河空气中ΣPAHs浓度范围为33.76～150.86 ng·d-1,平均值80.36 ng·d-1,其中绝壁、底部和地下河浓度分别为67.17、85.36和101.67 ng·d-1;空气中PAHs以2～3环的菲、蒽、萘、芴4种为主,占87.97%.PHAs的源来自于大气传输的化石燃料的燃烧.大石围天坑空气中PAHs的富集与传输过程为:地表-绝壁-底部-地下河,且浓度随深度/长度的增加有明显的增加趋势,在西峰脚、天坑底部和地下河处,低分子量的PAHs菲、蒽、芴和荧蒽发生了分异作用.温度是影响天坑中PAHs大气传输、富集的主要因子,其次为风向、风速和相对湿度;相对湿度和温度都是PAHs分异作用的主要因子,风速和风向为次要因子.总体上,天坑明显地展现了持久性有机污染物(POPs)的"冷陷阱效应"。

The typical karst Dashiwei Sinkholes located in Leye County,Guangxi were chosen as the study object.The air samples from the opening of Dashiwei Sinkholes to the underground river profiles were collected by polyurethane foam passive samplers（PUF-PAS）,and the meteorological parameters were observed.The 16 PAHs were analyzed using GC-MS.The results showed that the total PAHs concentration in air in Dashiwei Sinkholes ranged from 33.76 ng·d-1 to 150.86 ng·d-1,with an average of 80.36 ng·d-1.The mean concentrations in the cliff,the bottom and the underground river profiles were 67.17,85.36 and 101.67 ng·d-1,respectively.The 2-3 rings PAHs（including phenanthrene,anthracene,napnthalene and fluorene） accounted for 87.97% of the total of PAHs.The transport and accumulation processes of PAHs in air in Dashiwei Sinkholes were： the ground to the cliff section to the bottom section and then to the underground river,and the total PAHs concentrations showed an obvious increasing tendency with the decrease in altitude or increase in the length of the underground river.Low molecular weight PAHs compounds（including phenanthrene,anthracene,flourene and fluoranthene） in air went through differentiation at the bottom of the west peak,the bottom of the sinkhole and the underground river.The primary sources of PAHs were pyrogenic sources with atmosphere transport.Ambient temperature was the predominating factor influencing the transport and accumulation of gas phase PAHs in Dashiwei Sinkholes,following by wind speed,wind direction and relative humidity.Relative humidity and the temperature were the predominating factors influencing the differentiation,following by wind speed and wind direction.As a whole,a ＂cold trapping effect＂ of POPs was showed obviously in Dashiwei Sinkholes.