雾过程对大气气溶胶PM_(10)中多环芳烃粒径分布的影响

Effect of Fog Process on the Size Distribution of Polycyclic Aromatic Hydrocarbons in the Atmospheric Aerosol PM_(10)

在雾天气高发期采集大气气溶胶可吸入粒子(PM10)分级样品,测定了这些样品中的16种优控多环芳烃(PAHs).结果表明,雾区近地层大气中PM2.1(Dp<2.1μm)和PM9.0(Dp<9.0μm)的平均质量浓度明显增加,雾过程改变了PM2.1的昼、夜浓度变化特征;雾前、雾中与雾后大气气溶胶PM10中16种优控PAHs主要分布在比表面积较大的细粒子上,平均有83.04%PAHs分布在Dp<2.1μm的范围内,雾中1.1～2.1μm粒子的16种多环芳烃总浓度(∑16PAHs浓度)明显增加,Dp<0.65μm粒子的∑16PAHs浓度略有降低,说明雾过程对细粒子中∑16PAHs的浓度分布产生明显影响;雾前、雾中与雾后白天时间段,PM10分级粒子的∑16PAHs积聚模态分布出现较大差异,雾中积聚模态峰位置与雾前与雾后相比向较大粒径偏移;一次连续雾过程中,白天的∑16PAHs积聚模态峰位置随着雾的持续向大粒径方向偏移并停留在1.1～2.1μm;夜间的∑16PAHs积聚模态峰位置没有变化,均在1.1～2.1μm,说明PM10∑16PAHs的粒径分布受雾过程持续时间影响较大.

Fractionating samples of atmospheric aerosol PM10,collected during a fog high frequency period,were determined for 16 priority polycyclic aromatic hydrocarbons（PAHs）.Result shows that the average mass concentrations of PM2.1 and PM9.0 in the near surface layer of the fog area increase sufficiently,and the diurnal concentration variation of PM2.1 are changed due to fog process.Before,during and after fog event,the 16 priority PAHs in the PM10 mainly distribute in the fine particles with larger specific surface area,and averagely,83.04% of PAHs distribute on the aerosol with Dp2.1 μm.During the fog event,the concentrations of ∑16PAHs in the particles（Dp=1.1-2.1 μm） increase remarkably,whereas those in the particles（Dp0.65 μm） decrease slightly;therefore,fog process play a great role on the distributions of ∑16PAHs in the fine particles.In the daytime before,during and after fog event,the distributions of ∑16PAHs in the accumulation mode have large differences;the peak diameter of accumulation mode shifts to the larger size during the fog event,compared with those before and after fog.In a prolonged fog event,the peak diameter of daytime ∑16PAHs accumulation mode shifts to the larger size continuously and stays at 1.1-2.1 μm,while there is no significant variation of peak diameter in the night,all at 1.1-2.1 μm;subsiquently,the size distributions of ∑16PAHs in PM10 are greatly affected by the duration of the fog event.