不同粒径大气颗粒物中多环芳烃的含量及分布特征

Concentration and Distribution Characterization of Polycyclic Aromatic Hydrocarbons in Airborne Particles with Different Sizes

采集了北京城乡结合部与郊区 2 0 0 3年 4个季节的不同粒径大气颗粒物样品 ,运用GC/MS分析了其多环芳烃组成 .结果表明 ,17种PAHs总量为 0. 84～ 15.2 2 3ng/m3 ,城乡结合部含量是郊区的 1.0 7～ 6. 6 0倍 .PAHs总量的季节性变化表现为冬季 >秋季 >春季 >夏季 ,且随颗粒物粒径减小 ,含量逐渐增大 ,大约有 6 8 . %～ 84 .7%的PAHs吸附在≤ 2 . 0 μm颗粒上 .2～3环PAHs呈双峰型分布 ,4～ 6环PAHs呈单峰型分布 ,PAHs分子量越大 ,MMD值越小 ,燃煤取暖与低温是导致冬季PAHs污染增高的主要因素 .

Airborne particles with different sizes were collected in 2003 at two sampling sites(urban border and suburban area)of Beijing. Compositions of polycyclic aromatic hydrocarbons were detected by GC/ MS. The results show that total concentrations of 17 PAHs ranged between 0.84 and 152.23 ng/m3, in urban border area were 1.07～6.60 times higher than those measured in suburban area. The total concentration of PAHs increased with decreasing ambient temperature(winter>autumn>spring>summer). About 68.4%～84.7% of PAHs were absorbed on particles having aerodynamic diameter ≤2.0μm. The distribution of PAHs varies with the size of the molecules. Nearly bimodal distribution was found for two- and three-rings PAHs, four- to six-rings PAHs, however, followed unimodal distribution. The overall mass median diameter(MMD) for PAHs decreases with increasing molecular weight. Higher pollution level of PAHs in wintertime is probably ascribed to domestic heating and lower ambient temperature.