燃煤电厂周边气溶胶单颗粒的微观形貌和化学组分

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。

Microscopy morphology and chemical composition of individual aerosol particles near a coal-fired power plant

PM2.5 samples near a coal-fired power plant were collected. Physicochemical characteristics of individual particles were determined by Transmission Electron Microscope equipped with 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: Si-rich, 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 S-rich and Ca-rich particles in downwind aerosol was higher than it in upwind aerosol, which was likely related to the use of desulfurization 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 a suitable condition, such as high temperature and relative humidity, high concentrations of SO2 and NOX.