华北平原城乡夏季PM2.5组成特征及来源研究

Chemical characteristics and sources of PM_(2.5) in urban and rural sitesinthe North China Plain during summer

为研究华北平原细颗粒物(PM_(2.5))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PM_(2.5)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PM_(2.5)平均质量浓度为(71.47±38.04)μg/m^3,高于北京城区(51.44±30.94)μg/m^3,PM_(2.5)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PM_(2.5)中占比最高,约为60%.PM_(2.5)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PM_(2.5)中元素富集因子更高.来源分析表明,两地PM_(2.5)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PM_(2.5)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 PM2.5in the North China Plain(NCP),simultaneous fineparticulate matter(PM2.5)was sampled simultaneously in Beijing and Wangdu(Hebei)as part of the summer campaign ofCAREBEIJING-NCP2014.The samples were analyzed for water-soluble ions,elements,organic carbon(OC),andelemental carbon(EC).The average mass concentration of PM2.5was 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)dominatedthe PM2.5,and accounted for60%of its mass.The highest percentages of SNA appeared in air masses from the south andsoutheast,and reached60%~70%of PM2.5.Aerosol-crust enrichment factors of trace metals in Beijing were higher than inWangdu.Industrial activities and dust were major sources of the elements.Biomass burning created up to20%~40%ofthe PM2.5during days when its influence was obvious.Back-trajectories showed that PM2.5concentrations and majorcomponents at two sites were similar when the air masses came from the same direction,but different when the directionswere different.