南京北郊雾天PM10中多环芳烃粒径分布特征

为研究雾天PM10中多环芳烃粒径分布特征,2007-11-15~2007-12-30在南京北郊进行了PM10分8级粒径多环芳烃(PAHs)成分连续样品采集,由同步气象观测资料选出雾天与晴天样本作为对比,用GC-MS分析其中16种PAHs含量.雾天夜间PM2.1和PM9.0平均质量浓度为120.34μg.m-3和215.92μg.m-3,接近白天PM2.1(126.76μg.m-3)和PM9.0(213.41μg.m-3),昼、夜基本没有变化;晴天夜间PM2.1和PM9.0平均质量浓度为71.45μg.m-3和114.33μg.m-3,高于白天PM2.1(41.02μg.m-3)和PM9.0(74.38μg.m-3),昼、夜变化很明显;雾天PM2.1∑16PAHs为49.97 ng.m-3,是晴天(33.30 ng.m-3)1.50倍,PM9.0∑16PAHs为59.45 ng.m-3,是晴天(40.80 ng.m-3)1.46倍;PM2.1和PM9.0中PAHs单体平均浓度均为荧蒽最高,且雾天(PM2.1为7.98 ng.m-3,PM9.0为9.99 ng.m-3)高于晴天(PM2.1为5.23 ng.m-3,PM9.0为6.77 ng.m-3);雾天PM2.1和PM9.0中苯并a]芘的浓度为1.77ng.m-3和1.99 ng.m-3,高于晴天(PM2.1为1.46 ng.m-3,PM9.0为1.84 ng.m-3).结果表明,雾过程加重了近地面大气PM2.5和PM10的污染;雾天与晴天PM10∑16PAHs粒径分布的昼夜特征与PM10在2种天气系统下粒径分布的昼夜特征基本一致,均为双峰型分布,分别位于积聚模态和粗模态粒子.白天雾过程对PM10及PM10∑16PAHs的粒径分布影响比较大,夜间雾过程则对其没有太大影响.

Size Distribution Characteristics of Polycyclic Aromatic Hydrocarbons of PM10 in Foggy Days in the North Suburb of Nanjing

Based on meteorological data and aerosol samples from Nov. 15 to Dec.30,2007 in the north suburb of Nanjing, size distribution characteristics of polycyclic aromatic hydrocarbons (PAHs) in PM_(10) in foggy and sunny days were studied, and the concentrations of 16 PAHs were analyzed by gas chromatography with mass selective detection (GC-MS).The average concentrations of aerosols in the night (PM_(2.1) : 120.34 μg·m~(-3) ; PM_(9.0) :215.92 μg·m~(-3)) are close to those in the daytime (PM_(2.1) :126.76 μg·m~(-3) ; PM_(9.0) :213.41 μg·m~(-3) ) in foggy days. The average concentrations of aerosols are higher in the night (PM_(2.1) :71.45 μg·m~(-3); PM_(9.0) :114.33 μg·m~(-3)) than those in the daytime (PM_(2.1) :41.02 μg·m~(-3); PM_(9.0) :74.38 μg·m~(-3) ) in fine days. And we also find that the total concentrations of 16 PAHs in PM_(2.1) (49.97 ng·m~(-3)) and PM_(9.0)(59.45 ng·m~(-3)) in foggy days are 1.50 and 1.46 times of those (PM_(2.1) :33.30 ng·m~(-3); PM_(9.0) :40.80 ng·m~(-3)) in fine days separately. The average maximum concentrations of individual PAHs are fluoranthene, which are higher (PM_(2.1) :7.98 ng·m~(-3); PM_(9.0) : 9.99 ng·m~(-3)) in foggy days than those (PM_(2.1) :5.23 ng·m~(-3);PM_(9.0):6.77 ng·m~(-3))in fine days, and the average concentrations of benzo-a-pyrene are higher in fog days (PM_(2.1):1.77 ng·m~(-3); PM_(9.0) : 1.99 ng·m~(-3)) than those in fine days (PM_(2.1):1.46 μg·m~(-3);PM_(9.0):1.84 ng·m~(-3)) .Those results indicate that the fog processing could aggravate the pollution of PM_(2.5) and PM_(10) near the ground layer. Diurnal size distribution of total PAHs in PM_(10) is consistent with that of PM_(10) in foggy and sunny days, and size distribution investigated was bi-modal with a peak in accumulation particle mode and another peak in coarse particle mode aerosol. Size distributions of PM_(10) and total PAHs in PM_(10) are affected greatly by the day fog in daytime, while those are affected little by the night fog in night.