北京城区PM_(2.5)输送途径与潜在源区贡献的四季差异分析

Analyze to the seasonal differences of transport pathways and potential source-zones of Beijing Urban PM_(2.5)

利用HYSPLIT后向轨迹模式和NCEP的GDAS气象数据(2014年5月1日~2015年4月30日),对抵达北京城区的逐小时3日气流后向轨迹按季节聚类,并结合PM2.5质量浓度地基观测数据,分析不同输送途径的空间特征及其对北京城区PM2.5聚集的贡献.利用潜在源贡献作用(PSCF)和浓度权重轨迹(CWT)分析方法,揭示研究期内北京城区不同季节PM2.5的潜在源区分布及其贡献特性.结果表明:北京城区PM2.5输送途径的季节特征明显,不同输送途径对北京城区PM2.5的贡献差异显著.春季贡献源区主要位于中国西部地区、华北及黄淮平原,夏季贡献源区主要位于山东、苏北及黄海地区,秋季主要位于冀南、鲁西、鲁中及苏鲁豫皖交界地区,冬季主要位于冀南、鲁西北、晋北、陕西、内蒙中部及蒙古国南部.来自山东与冀南的气流轨迹四季均对应PM2.5高值;冬春两季来自西北的气流轨迹也对应较高PM2.5值.

Both HYSPLIT backward trajectory mode and Global Data Assimilation System (GDAS) meteorological datafrom the National Centers for Environmental Prediction (NCEP) were used to analyze the three-day backward trajectoriesof hourly airflow in Beijing urban from May 1st, 2014 to April 30st, 2015. Clustering analysis was used to classify theairflow backward trajectories of Beijing urban in different seasons. The hourly ground PM2.5 observations were also usedto analyze the spatial characteristics of different transport pathways and its contribution to the PM2.5 concentration inBeijing urban. Potential source contribution function (PSCF) and concentration-weighted trajectory (CWT) were appliedto identify the potential source-zones (PSZs) and its contribution to Beijing urban PM2.5 in different seasons during thestudy period. This study revealed that the Beijing airflows were significantly characterized by monsoons, and the PTZs ofBeijing urban PM2.5 varied a lot in different seasons during the study period: a) in the spring, it mainly located innorthwest China, North China Plain and YellowRiver-HuaiRiver plain; b) in the summer, it mainly located in Shandong,north Jiangsu and Yellow Sea; c) in the fall, it mainly located in south Hebei, west Shandong, central Shandong and theadjoining areas of Jiangsu, Shandong, Henan and Anhui Provinces; d) in the winter, it mainly located in south Hebei,northwest Shandong, north Shanxi, Shaanxi, central Inner Mongolia and south Mongolia. The airflows from Shandongand south Hebei carried high concentrations of PM2.5 in all seasons, while the airflows from northwest China carriedmiddle concentrations of PM2.5 in winter and spring.