中文摘要：

为了确定典型喀斯特区广西大石围天坑群地下河多环芳烃的组成、来源及污染特征,沿途采集了8个断面的表层水样品,利用GC-MS仪测试了16种优控多环芳烃（PAHs）.结果表明,地下河水中ΣPAHs（总量PAHs）浓度为54.7～192.0ng/L,平均值为102.3 ng/L,PAHs组成以2～3环为主,占65.1%.地下河沿程水中的PAHs浓度变化表明,上游高于下游,是因为城镇污水的排放,同时地下河对4～6环PAHs具有吸附作用;大石围天坑断面的ΣPAHs浓度显著增高93.8%,是由于地下河系统中环境介质的释放和大气传输;大石围支流汇合处的ΣPAHs浓度被稀释降低了47.3%;百朗出口断面的ΣPAHs浓度分别高于进口和大石围断面128.3%和17.8%.PAHs来源分析表明,城镇和大石围天坑区域显示以石油类及其燃烧源为主.然而,城镇的石油类源主要是人为输入,大石围天坑的则主要是天然输入;其余乡村地区显示以草木、煤燃烧源为主.与其他地区比较,大石围天坑群地下河水中PAHs污染处于较低的水平,但苯并[a]芘浓度6个断面超过国家地表水环境质量标准.

英文摘要：

In order to understand the composition,sources and contamination characteristics of PAHs in water from underground river of Dashiwei Tiankeng group in typical karst area located in Leye County,Guangxi.The water samples were collected from different sections to analyze 16 priority polycyclic aromatic hydrocarbons using GC-MS.The results showed that concentration of Σ PAHs（the total PAHs）in water ranges from 54.7 ng/L to 192.0 ng/L,with an average concentration of 102.3 ng/L.The predominant PAHs in water are 2-3 ring PAHs,accounting for 65.1% of Σ PAHs.The distribution of PAHs in water sampled along the underground river indicates that the mean concentration of Σ PAHs in upstream area is higher than that of downstream because of wastewater discharge.Meanwhile,the underground river has some adsorption effect to 4-6 ring PAHs.The concentration of Σ PAHs at Dashiwei Tiankeng section increases 93.8% attribute to the release of PAHs coming from karst environmental medium and /or atmospheric transmission in underground river system.However,the concentration of Σ PAHs at the confluence section of the tributary of Dashiwei Tiankeng is 47.3% less than that of the first upstream section duo to dilution.The concentration of Σ PAHs at Bailang outlet section is 128.3% and 17.8% higher than that of flow-in section and Dashiwei Tiankeng section respectively.The ratios of specific PAHs indicate that the PAH sources in Leye County and Dashiwei Tiankeng areas mainly come from both petroleum and its combustion.However,the petroleum origin comes from anthropogenic inputs in town and the natural inputs in Dashiwei Tiankeng.The PAH sources in rural areas are mainly originating from the combustion of grass,wood and coal.Comparison to other areas in the world,the Σ PAHs residual levels in underground river water in Dashiwei Tiankeng group is at the low level.In six sections,concentrations of benzo[a]pyrene（BaP） in surface water exceed the state quality standards.