北京PM_(2.5)中多环芳烃的污染特征及来源研究

Concentration and sources of atmospheric polycyclic aromatic hydrocarbons(PAHs) in PM_(2.5) in Beijing

采用GC/MS定量分析了2003年9月至2004年7月期间北京市PM2.5中16种优控PAHs的含量.研究表明,PAHs总浓度年均值139.59ng.m-3,变化范围1.02～776.4ng.m-3.冬季浓度最高271.05ng.m-3,夏季最低26.10ng.m-3,反映了主要源排放(燃煤)变化与气象条件的共同影响.全年平均不同环数PAHs所占总浓度的比例由大到小:4环>5环>6环>3环>2环;冬季4环PAHs所占比例最大(48.7%),其次为5环(32.5%)和6环PAHs(14.9%);夏季5环、6环PAHs所占比例最高(36.5%),其次为4环PAHs(24.1%).源排放特征化合物比值法和主成分分析法结果都表明,燃煤、机动车和油类挥发是多环芳烃的3类主要污染源,能够解释主成分分析法总方差的88%.

Sixteen polycyclic aromatic hydrocarbons （PAHs） were determined by GC/MS in PM2.5 samples taken from September 2003 to July 2004 in Beijing. The annual average concentration of the total PAHs was 139.59 ng·m^-3, ranging from 1.02 ng·m^-3 to 776.4 ng·m^-3 and showed strong seasonal variation, that is, the highest value in winter （271.05 ng·m^-3 ） and the lowest in summer （26. 10 ng·m^-3 ）. These results indicate the influence of both main source emission and meteorological conditions. Over the whole year, the average amounts of the different ring PAHs appeared in the following order： 4-ring 〉 5-ring 〉 6-ring 〉 3-ring 〉 2-ring. In winter, the percentage of 4-ring PAHs was the highest （48.7%） , followed by 5-ring PAHs （32.5%） and 6-ring PAHs （14.9%） ; in summer, the percentage of 5-ring and 6-ring PAHs （36.5% , together） were higher than 4-ring PAHs （24.1%）. Results from both the characteristic ratios of sources and principal component analysis （PCA） indicated that coal burning, gasoline and diesel vehicle emissions were the three main sources of PAHs in PM2.5 in Beijing. These three sources can explain 88% of the total variance.