中文摘要：

采用GC/MS测定了奥运空气质量保障措施实施期间（2008年8月）及非奥运时段（2008年6月、2009年8月）北京市北四环道路边PM2.5中12种优控PAHs含量,并应用特征化合物比值法对PAHs来源进行了识别.研究表明,奥运空气质量保障措施实施期间PAHs总浓度平均为4.77 n.gm-3,较非奥运时段下降了59%,已接近国外大城市道路交通环境污染水平.两个时段PAHs环数分配均为5~6环〉4环〉3环,但奥运空气质量保障措施实施期间由于柴油车尾气、燃煤烟尘和道路扬尘的严格控制,4环PAHs浓度显著下降.昼夜变化分析表明,非奥运时段表征汽油车尾气特征的PAHs浓度白天高于夜间,表征柴油车尾气特征的PAHs浓度则为夜间高于白天;而奥运空气质量保障措施实施期间这两类PAHs浓度的昼夜差异均不如非奥运时段明显.源识别结果显示,非奥运时段PM2.5中PAHs主要来源为机动车尾气排放,兼有燃煤和生物质燃烧;而奥运控制时段机动车尾气排放的贡献被削弱,呈现出石油和燃煤源混合的特征.

英文摘要：

Twelve polycyclic aromatic hydrocarbons（PAHs） were identified by GC/MS in the PM2.5 samples collected when the temporary emission control measures were implemented during the Olympic period in August 2008.These 12 PAHs were also measured during the non-Olympic periods of June 2008 and August 2009.The Molecular Diagnostic Ratio（MDR） technique was used to distinguish the sources of the PAHs in PM2.5 at the roadside.The PM2.5-bound PAHs concentrations measured during the Olympic period decreased by 59% compared with the non-Olympic periods.The average concentration of 4.77 ng·m-3 was similar to the PAH levels in foreign cities.In both the Olympic and non-Olympic periods,the distribution profiles of the PAHs were similar with regard to the number of rings in the compounds： 5~6-ring 4-ring 3-ring.However,during the Olympic period,a significant decrease in the concentrations of 4-ring PAHs resulted from the stringent controls placed on heavy-duty diesel trucks,coal-fired boilers and road dust.The concentrations of gasoline-related PAHs were higher in the daytime than in the nighttime in the non-Olympic periods.By contrast,the concentrations of diesel-related PAHs were higher in the nighttime.The diurnal variations in gasoline and diesel-related PAHs changed during the Olympic period due to the temporary traffic control measures.The leading source of PM2.5-bound PAHs at the roadside in the non-Olympic period was vehicle exhaust emissions,while coal and biomass burning also contributed major fractions to the total PAH concentration.During the Olympic period,the contribution of vehicle exhaust emission to the total PAH concentration decreased significantly;instead,emissions from oil and coal combustion contributed more to the PM2.5-bound PAHs at the roadside.