2017年厦门金砖会晤期间PM2.5的化学特征及来源

为了探讨厦门金砖会晤期间的排放控制措施以及天气形势对大气颗粒物污染特征的影响,于2017年8月10日至9月10日对厦门气态污染物、细颗粒物(PM2.5)中的水溶性离子以及有机碳(OC)、元素碳(EC)等主要化学成分开展了高时间分辨率的在线监测。根据空气质量管控措施和天气形势将研究期分为6个阶段。管控前、管控期Ⅰ(非台风)和管控期Ⅱ(非台风) PM2.5质量浓度分别为(33. 12±9. 48)、(30. 30±17. 00)、(16. 01±4. 71)μg/m^3。管控期Ⅰ(台风)和管控期Ⅱ(台风) PM2.5质量浓度分别为(12. 40±3. 73)、(12. 45±3. 28)μg/m^3。结果表明:管控期Ⅰ(非台风)阶段受静稳天气的影响,管控效果削弱,PM2.5质量浓度下降幅度小;台风对颗粒物质量浓度下降的影响比管控更显著。管控初期,PM2.5中二次无机离子的质量浓度下降明显;台风对碳质组分质量浓度的影响不如无机组分显著。PMF源解析结果表明,二次无机源是PM2.5主要来源,随着管控措施的实行,扬尘源的贡献从21%降低到6%,而机动车源的贡献降幅不明显。台风期间SO4^2-、NO3^-、SO2、NO2以及硫酸盐氧化比值(SOR)均明显低于非台风期间,氮氧化比值(NOR)反而升高。台风和非台风期间NOR的日变化特征一致,NOR与阳离子的相关性分析结果表明,台风或高风速海风期间NOR与Na^+呈现很强的正相关性,说明海盐粒子可促进NO2非均相反应生成NO3-。

Chemical Characteristics and Sources of PM2.5 During the 2017 BRICS Summit in Xiamen

To explore the impact of control measures and the synoptic situations on the characteristics of atmospheric particles during the BRICS summit in Xiamen,the gaseous pollutants,the water-soluble ions and organic carbon/elemental carbon (OC/EC) of fine particles (PM2.5) were monitored online at high time resolution from Aug.10 to Sep.10,2017. The whole study period was divided into six stages based on air quality control measures and weather situations. PM2.5 concentration of S1,S2-non-typhoon and S3-non-typhoon were (33. 12±9. 48), (30. 30±17. 00), (16. 01±4. 71) μg/m^3,respectively,while PM2.5 concentration of S2-typhoon and S3-typhoon were (12. 40 ± 3. 73), (12. 45 ± 3. 28) μg/m3. Because of stagnant meteorology,the impact of control measures on PM2.5 concentration in S2-non-typhoon was weak,while the impact of typhoon on the decline of particles concentration was more significant than control. At the beginning of emission control stage,the concentration of secondary inorganic ions decreased significantly. The effect of typhoon on the concentration of carbonaceous components was not significant.PMF results show that the secondary inorganic source was the most important source of PM2.5. With the implementation of the control measures,the contribution of dust source was reduced from 21% to 6%,while the contribution of vehicle source was not reduced significantly. SO4^2-,NO3^-,SO2,NO2,and Sulfate oxidation ratio (SOR) during the typhoon period were lower than those during the non-typhoon period,while Nitrogen oxide ratio (NOR) showed opposite result. The daily variation of NOR during typhoon and non-typhoon was similar,and NOR and Na+showed a strong positive correlation during typhoon or high wind speed sea breeze period,which indicated that sea salt can promote heterogeneous reaction of NO2 to NO3^-.