中文摘要：

对北京2015年11月26日~12月2日出现的 PM 2.5严重污染过程进行研究,分析了此次事件的污染特征和气象条件,结合 HYSPLIT模型,用聚类方法对研究期间抵达北京的地面（500m）和高空（3000m）逐时72h 气流后向轨迹聚类,并分析了地面和高空方向上气流轨迹对北京 PM 2.5浓度的影响.运用潜在源贡献因子分析法和浓度权重轨迹分析法分别模拟了此次 PM 2.5的主要潜在源区.结果表明,研究期间,北京PM 2.5小时均浓度数值变化较大.低温,高湿度和微风为北京 PM 2.5严重污染过程的出现创造了适宜条件.不同方向气流轨迹对北京 PM 2.5的影响在空间上存在显著差异.西北方向气流是影响北京 PM 2.5浓度的主要气流轨迹,而地面来自南部的气流对北京 PM 2.5浓度的影响也不能忽视.对北京 PM 2.5的 WPSCF 和 WCWT 分析表明,蒙古国中西部、新疆东部、内蒙古中西部、山西北部、河北和山东北部对北京 PM 2.5质量浓度贡献分别在0.7,200μg/m3以上,表明这些地区是影响此次北京 PM 2.5的重要潜在源区.

英文摘要：

Pollution characteristics processes and potential sources of PM2.5 were studied in a severe haze episodes in Beijing from 26 November to 2December, 2015. Pollution characteristics and meteorological parameters were analyzed. Hourly 72-hour backward trajectories in ground （500m） and high altitude （3000m） were classified and the effect of clusters in ground and high altitude on PM2.5 were analyzed using HYSPLIT model and cluster method. Major potential sources of PM2.5 were simulated using Potential Source Contribution Function （PSCF） and Concentration-weighted Trajectory （CWT） methods. The results showed that hourly PM2.5 concentration in Beijing varied widely and low temperature, high humidity and low wind speed provided a suitable condition for the heavily pollution process of PM2.5. Airflow trajectories from different directions had an significant impact on the spatial distribution of PM2.5 in Beijing. Air trajectories from northwestern were the dominant trajectories which had a big influence on PM2.5 concentration in Beijing. Moreover, air trajectories in ground from southern should not be ignored because air trajectories that passed through southern areas carried anthropogenic pollutants to Beijing. WPSCF （weighted potential source contribution function） and WCWT （weighted concentration-weighted trajectory） values were more than 0.7 and 200μg/m3 outside of Beijing, respectively, which revealed that mid-western Mongolia, eastern Xinjiang, mid-western Inner Mongolia, northern Shanxi, Hebei and regions in northern Shandong were the major potential sources of PM2.5 in Beijing.