南京北郊秋季气溶胶理化特征及潜在源区分布

摘要

Single particle aerosol mass spectrometry (SPAMS) was deployed to continuously observe the ambient aerosols over the suburb of Nanjing during the autumn of 2015. 4groups of particles were selected: EC-rich particles (EC), OC-rich particles (OC), K-rich particles (K-rich) and Metal-rich particles (Metal), accounting for 29.39%, 9.53%, 26.55% and 8.54% of total number, respectively. The particle number and size distribution of 4groups were analyzed under different weather conditions. Backward trajectory model and concentration weighted trajectory method were employed to obtain the potential source region of particles. The results showed that, the average number of total particles were about 2900, 1300, 6450 and 5950h-1 , for clean, rainy clean, polluted, and rainy polluted days. The number of all groups of particles increased significantly and their size distribution shifted to larger size, except for OC. Heavy precipitation have obvious scavenging effects on all groups of particles, especially for the large size. However, the effects varied with particle size and were not notable in the rainy polluted days. Particles carried by the air mass from different source regions have different number and categories of fine particles. Oceanic air mass was mainly cleaner than continental air mass. Air mass was significantly influenced by the local emissions when it passed through the land. The potential source region of the fine particles were mainly located locally in Nanjing and southwest areas, around Ma'anshan of Anhui Province. The potential source region of 4groups of particles had distinct spatial distribution.%利用单颗粒气溶胶质谱仪(SPAMS)于2015年秋季对南京北郊大气颗粒物进行了连续观测,选取了4类主要颗粒:富元素碳颗粒(EC)、富有机碳颗粒(OC)、富钾颗粒(K-rich)和富金属颗粒(Metal),占总颗粒数的比例分别为29.39%,9.53%,26.55%,8.54%.分析了不同天气下4类颗粒的粒子数和粒径分布的变化,采用后向轨迹模型和浓度权重轨迹方法,得到了各类颗粒的潜在源区分布.结果表明,清洁、清洁降雨、污染、污染降雨,4类天气采集到的颗粒物平均数分别约为2900,1300,6450,5950h-1.污染天气下,EC和Metal颗粒对当地颗粒物污染的贡献增大,各类颗粒的粒子数均大幅上升,并且除了OC颗粒,其他类颗粒粒径普遍向大粒径段偏移.强降水对各类颗粒均有明显的清除作用,其中大粒径段颗粒数下降最显著,但在污染降雨天气下,降水清除作用不明显,且对各类颗粒的清除作用存在粒径差异.不同来源气团携带的细颗粒物数量与类别存在差异,总体上海洋气团比内陆气团更清洁,气团经过陆地时会显著受到当地排放源的影响.细颗粒物的高贡献源区主要在本地及西南侧的安徽马鞍山一带,各类颗粒物的强潜在源区分布也存在明显差异.