中文摘要：

对西安市2009年6月-2010年5月空气中的总悬浮颗粒（TSP）和气态样品进行了连续采样，利用GC—MS对16种PAHs进行分析。∑PAHs浓度（气相＋颗粒相）范围为39．93～1032．46ng／m^3，平均值为197．34ng／m^3；其中，冬季大气中∑PAHs浓度最大，相对浓度的范围为31．21％～72．98％，而夏季的浓度最小；检测出16种2～6环的PAHs，其中以3—4环为主。利用特征分子比值法和因子分析进行源解析，发现研究区PAHs的主要来源为燃煤和机动车尾气排放。通过苯并（a）芘（BaP）等效毒性（BEQ）和苯并（a）芘等效致癌浓度（BaPE）进行健康风险评价，结果显示，西安大气中PAHs的毒性具有明显的季节差异，特别是秋季和冬季大气中PAHs对人类的健康存在较大的潜在威胁。

英文摘要：

Total suspended particulates （TSP） samples and gas phase air samples were collected in Xi＇an from June 2009 to May 2010, and 16 kinds of polyeyelic aromatic hydrocarbons （PAHs） were analyzed via GC- MS. The concentrations （gas plus particle phases） of ∑PAHs ranged from 39.93 to 1 032.46 ng/m3, with an average concentration of 197. 34 ng/m3; while the highest in winter, relative concentrations ranged from 31.21% to 72.98% , and the lowest in summer. 16 PAHs were detected ranged from 2 to 6 rings, with 3 to 4 rings primarily. Using the diagnostic ratio method and factor analysis for source apportionment, it was found that in the study area, the main sources of PAHs were coal and motor vehicles exhaust emission. Health risk assess- ment through the benzo[ a ~ pyrene equivalent toxicity（BEQ） and benzo （a） pyrene equivalent carcinogenic con- centration （BaPE） indicated that the toxicity of PAHs in Xi＇ an presented significant seasonal variation, especial- ly in autumn and winter, atmospheric PAHs on human health had greater potential threat.