- Pollution characteristics of a haze episode in nanjing in the winter of 2018 and the possible meteorological driving force
- 南京大学大气科学学院, 南京 210023
- 生态环保部南京环境科学研究所, 南京 210023
- 摘要：2018年11月底—12月初南京及周边地区发生一次大范围持续性霾污染，利用南京市空气质量监测资料、颗粒物成分逐时观测资料、南京站探空资料等，结合天气学诊断分析、后向轨迹模拟和聚类分析等方法，分析此次重霾事件的污染特征和气象因素.结果表明，此次重霾事件具有峰值浓度高、持续时间长、波动较明显等特点.污染时段PM2.5浓度变化分为3个阶段，平均浓度为114.7 μg·m-3，整体达到中度污染.重霾期间南京市大气环境处于富氨条件，颗粒物整体偏酸性，移动源排放比重高于固定源，PM2.5主要成分的存在形式为硫酸铵、硝酸铵和其他硝酸盐.本次重霾事件中气象条件对污染物的输送和累积影响显著，在PM2.5浓度极端事件发生期间，均有各气象要素与PM2.5浓度同步变化.高PM2.5浓度与对流层低层增暖增湿、弱的西南风相对应.重霾事件的主要天气成因是冬季东部地区出现大面积稳定且持久的均压场，南京及周边地区近地面中高层污染物主要由西北和华北地区输送而来，低层污染物主要来自于本地源排放累积.动力条件和热力条件的相互配合，近地面受高压影响形成暖平流逆温层，且易形成下沉气流，使重霾天气持续发展.
- Abstract：From the end of November to the beginning of December, 2018, a large-scale persistent haze pollution episode occurred in Nanjing and its surrounding areas. Based on the hourly air quality monitoring data, the observated data of particulate matter compositions, and the meteorological sounding data, etc., combined with synoptic diagnostic analysis, backward trajectory simulation and cluster analysis, the pollution characteristics and meteorological factors of this heavy haze event were analyzed. The results showed that the heavy haze event had the characteristics of high peak concentration, long duration and obvious fluctuation. The variation of PM2.5 concentration in the pollution period could be divided into three stages, with an average concentration of 114.7 μg·m-3, which reached moderate pollution overall. During the period of heavy haze, the atmospheric environment in Nanjing was rich in ammonia, the particulate matter was generally acidic, the emission proportion of mobile sources was higher than that of fixed sources, and the main components of PM2.5 were ammonium sulfate, ammonium nitrate and other nitrates. Meteorological conditions had a significant impact on the transportation and accumulation of pollutants in this heavy haze event. During the extreme event of PM2.5 concentration, all meteorological elements and PM2.5 concentrations changed synchronously. The high PM2.5 concentration corresponded to the warming and humidification in the lower troposphere, caused by the weak southwest wind. The main synoptic reason for the heavy haze event was a large area of stable and lasting pressure equalization field in the eastern region in winter. The medium and high-level pollutants near the ground in Nanjing and its surrounding areas were mainly transported from the northwest and north China regions, while the low-level pollutants mainly came from the accumulation of local source emissions. A warm advection inversion layer was formed near the ground under the influence of high pressure. Also, the downdraft was easy to form. Thus, the heavy haze weather developed and maintained synthetically caused by the dynamic and thermal effects.