后奥运时期京津冀区域大气本底夏季污染变化

为探索后奥运时期京津冀区域大气本底污染状况及变化趋势,在中国科学院华北兴隆大气本底观测站,对夏季大气主要污染物(NOx、SO2、O3和PM2.5)进行了连续3年的在线观测,结合气流轨迹模式对大气污染物的传输路径及贡献率进行了分析.结果表明:兴隆站大气本底夏季ρ(NOx)、ρ(SO2)、ρ(O3)和ρ(PM2.5)的平均值分别为(11.5±5.9)、(8.3±7.0)、(137.6±38.4)和(50.9±33.0)μg/m3;首要污染物为O3和PM2.5,ρ(O3)和ρ(PM2.5)日均值超过GB 3095─2012《环境空气质量标准》二级标准〔ρ(O3)为200μg/m3,ρ(PM2.5)为75μg/m3〕的天数分别为102和60 d,占观测期间有效天数的39%和23%,表现为大气氧化性增强、二次污染逐年上升;受偏南气流影响,太行山沿线区域和山东半岛—渤海湾地区是兴隆夏季大气本底污染的主要贡献区域,特别是京津冀城市区域夏季高浓度O3和PM2.5,对华北区域大气本底污染物浓度的整体上升具有重要影响.

Changes in Atmospheric Background Pollution during Summer in the Beijing-Tianjin-Hebei Region after the 2008 Olympic Games in China

To investigate the status of background pollution and changes in air quality in the Beijing-Tianjin-Hebei region in the post-Olympic period,automatic environmental monitoring instruments were used to observe concentrations of the main atmospheric pollutants(NOx,SO2,O3 and PM2.5) at Xinglong regional background observation station during summer for three consecutive years.Transport and sources of air pollutants were analyzed by backward trajectories calculated by the HYSPLIT model.The results showed that the average concentrations of NOx,SO2,O3 and PM2.5 in this region during the summer were(11.5±5.9),(8.3±7.0),(137.6±38.4) and(50.9±33.0) μg/m3,respectively.The main pollutants at Xinglong station were O3 and PM2.5;the number of days in which the daily concentrations of these two pollutants exceeded the secondary standard of China’s ambient air quality standard(GB 3095-2012)(200 μg/m3 for O3 and 75 μg/m3 for PM2.5) were 102 days and 60 days,respectively,which accounted for 39% and 23% of the total observation days.These results indicated that atmospheric oxidation and secondary pollution increased yearly.Influenced by the southerly airstream during the summer,air pollutants emitted along the Taihang Mountains and the Shandong Peninsula-Bohai Bay region were transported to Xinglong station,causing major contribution of high O3 and PM2.5 pollution in the Beijing-Tianjin-Hebei urban areas and the entire North China area.