采集燃煤电厂上风向和下风向PM2.5样品,使用带能谱的透射电镜观察单颗粒的特征。根据颗粒的微观形貌、化学组分及电子束作用下的稳定性,将颗粒物分成9种类型:富Si、富Ca、富S、富K、富Fe、飞灰、有机、烟尘和其他颗粒.研究表明,燃煤电厂排放的球形富Fe颗粒和飞灰颗粒使下风向气溶胶中球形颗粒的数量增加;下风向气溶胶中富S颗粒和富Ca颗粒的相对丰度高于上风向,这可能与电厂控制SO2排放使用石灰石作脱硫剂有关;电厂下风向具有核壳结构颗粒的数量明显多于上风向,其原因是来自燃煤电厂或上风向的颗粒在合适的条件下(如温度高、相对湿度大、SO2与NOx浓度高等),易与其他物质发生化学反应形成具有核壳结构的复杂颗粒。
PM2.5 samples near a coal-fired power plant were collected. Physicochemical characteristics of indi-vidual particles were determined by a Transmission Electron Microscope equipped with an Energy Dispersive X-ray Spectrometer (TEM-EDX). Based on the chemical composition, morphology and stability under electron beam, the particles were classified into the following nine types Sirich, Ca-rich, S-rich, K-rich, Fe-rich, fly ash, organic, soot, and other particles. The result shows spherical Fe-rich and fly ash particles from a coal-fired power plant led to increase relative abundance of spherical particles in downwind aerosol. Relative abundance of S-rich and Carich particles in downwind aerosol was higher than it in upwind aerosol, which was likely related to the use of desulfu-rization agent to decrease SO2 emission. Relative abundance of particles with core-shell structure in downwind aerosol was higher than it in upwind aerosol because particles from a coal-fired power plant or upwind easily reacted with other materials to form complex particles with core-shell structure under suitable conditions, such as high tem-perature and relative humidity, high concentrations of SO2 and NOx.