Chemical characteristics and sources of PM2.5 in urban and rural sitesinthe North China Plain during summer

为研究华北平原细颗粒物(PM2.5)的组成特征及来源,基于CAREBEIJING-NCP 2014大型观测项目,于2014年夏季在北京城区和河北郊区望都进行了同步观测,分析了两地PM2.5中水溶性离子、元素、有机碳(OC)和元素碳(EC).结果表明,采样期间望都站点PM2.5平均质量浓度为(71.47±38.04)μg/m3,高于北京城区(51.44±30.94)μg/m3,PM2.5中各化学组分浓度也均表现为望都高于北京,二次无机离子(硫酸盐、硝酸盐及铵盐)在两地PM2.5中占比最高,约为60%.PM2.5中多种元素浓度也表现为望都均高于北京,但富集因子分析表明,北京市PM2.5中元素富集因子更高.来源分析表明,两地PM2.5中元素均受到工业源和尘源的影响;此外,观测期间两地均受到生物质燃烧影响.后向轨迹分析表明,当到达两地的气团来向相同时,北京与望都PM2.5浓度水平和化学组成呈现相似性,但当气团来向不同时,两地污染特征差异较大.To study the chemical characteristics and sources of PM2.5 in the North China Plain (NCP), simultaneous fine particulate matter (PM2.5) was sampled simultaneously in Beijing and Wangdu (Hebei) as part of the summer campaign of CAREBEIJING-NCP 2014. The samples were analyzed for water-soluble ions, elements, organic carbon (OC), and elemental carbon (EC). The average mass concentration of PM2.5 was higher in Wangdu (71 ± 38μg/m3) than in Beijing (51 ± 31μg/m3), as were all the components of PM2.5. Secondary inorganic ions (SO42?, NO3?, NH4+, or SNA) dominated the PM2.5, and accounted for 60% of its mass. The highest percentages of SNA appeared in air masses from the south and southeast, and reached 60%~70% of PM2.5. Aerosol-crust enrichment factors of trace metals in Beijing were higher than in Wangdu. Industrial activities and dust were major sources of the elements. Biomass burning created up to 20%~40% of the PM2.5 during days when its influence was obvious. Back-trajectories showed that PM2.5 concentrations and major components at two sites were similar when the air masses came from the same direction, but different when the directions were different.国家自然科学基金资助项目; 国家科技支撑计划课题; 环保部大气颗粒物化学成分在线监测设备研制与应用示范项目93227-32363