The evolution of an aerosol event observed from aircraft in Beijing: An insight into regional pollution transport
The evolution of an aerosol event observed from aircraft in Beijing: An insight into regional pollution transport
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DOI：
10.1016/j.atmosenv.2019.02.005
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发表时间：
2019-06
影响因子：
5
通讯作者：
P. Tian;Dantong Liu;Mengyu Huang;QUAN LIU;Delong Zhao;L. Ran;Z. Deng;Yunfei Wu;S. Fu;
中科院分区：
文献类型：
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作者：
P. Tian;Dantong Liu;Mengyu Huang;QUAN LIU;Delong Zhao;L. Ran;Z. Deng;Yunfei Wu;S. Fu;
为研究北京地区污染物的输送和形成机制，利用飞机观测技术，对2016年12月10 - 12日北京地区发生的一次区域性输送（RT）污染过程中的气溶胶垂直分布特征进行了研究。气溶胶的化学成分和粒度分布进行了表征。不同的垂直结构表现在三个时期（定义为RT前，RT期间，RT后）为这次污染事件。RT前，当清洁偏北气团占主导地位时，混合层PM2. 5和黑碳质量负荷处于较低水平。RT期间，在北京上空ML上部（400-900 m）出现了一个气溶胶层，其中BC和PM2.5的质量浓度约为地面的1.5倍。这一上升的气溶胶层是由盛行的西南气团输送的污染物从北京上空的污染严重的西南地区平流。这些气溶胶通过RT的特点与明显的二次成分和大涂层的BC颗粒。RT后，污染物被显著稀释的盛行西北气团，而气溶胶浓度几乎维持在近地面，导致显着的垂直梯度。地面污染持续可能是由于次日风速较低和二次气溶胶形成所致。研究表明，仅从地面观测资料不能完全解释此次污染事件，而应考虑气溶胶性质垂直结构的变化，以阐明北京污染的形成机制。
To investigate the transport and formation mechanism of pollution in Beijing, this study explored the vertical profiles of aerosol properties using aircraft measurement during a regional transport (RT) pollution event from 10th to 12th December 2016. The aerosol chemical composition and size distribution were characterized. Different vertical structures exhibited during three periods (defined as before RT, during RT, and after RT) for this pollution event. Before RT, PM2.5and black carbon (BC) mass loading were at low level in the mixing layer (ML) when the clean northerly air mass dominated. During RT, an elevated aerosol layer, in which BC and PM2.5mass concentrations were about 1.5 times higher than that at the ground level, was found in the upper ML (at 400–900 m) over Beijing. This elevated aerosol layer was advected by the prevailing southwesterly air mass which transported the pollutants from the intensively polluted southwestern region over Beijing. These aerosols through RT featured with pronounced secondary compositions and large coatings on BC particles. After RT, the pollutants were significantly diluted by the prevailing NW air mass, whereas the aerosol concentration almost maintained in the near surface, leading to notable vertical gradient. The continued surface pollution may result from the low wind speed and secondary aerosol formation in the next day. This study suggests that only the ground observation could not fully explain the pollution event, but the variation of vertical structure of aerosol properties should be considered to elucidate the formation mechanism of pollution over Beijing.