学校食堂、烤肉店PM2.5的微观形貌及粒度分布

使用带能谱的高分辨率场发射扫描电镜(FESEM)和图像分析技术对食堂和烤肉店PM_2.5(细颗粒物)进行微观形貌观察,研究其数量-粒度分布、体积-粒度分布特征. 结果表明:从微观形貌看,PM_2.5主要有矿物颗粒、烟尘集合体、球形颗粒、其他颗粒(生物质、食盐、纤维)4种,其中矿物颗粒有不规则和规则2种形态. 烤肉店的PM_2.5可观察到形成链状的烟尘集合体,而食堂的可观察到更细颗粒组成的链状烟尘集合体.食堂矿物颗粒分别占颗粒物总数和总体积的69.23%、80.13%；数量-粒度分布呈双峰,主要分布在0.2~0.4μm范围内,小于0.5μm的矿物颗粒占颗粒物总数的58.90%；体积-粒度分布呈单峰,集中在在1~2.5μm.烤肉店矿物颗粒和其他颗粒分别占颗粒物总数的45.67%、44.86%；数量-粒度分布主要集中在0.2~0.4μm,小于0.5μm的矿物颗粒占颗粒物总数的39.41%；从体积-粒度分布上看,1~2.5μm内的矿物颗粒体积占颗粒物总体积的比例(32.36%)最大. 

Morphological Characteristics and Size Distribution of PM2.5 in Cafeteria and Barbecue Restaurant

There is increasing concern regarding the potential health risks associated with inhalation of ultrafine particles. The particle samples of 0.08-2μm were classified as accumulation range. These particles originated from the coagulation of smaller primary particles emitted from combustion sources, condensation of volatile species, gas-to-particle conversion, and finely ground dust particles. The nuclei and accumulation ranges included most of PM_2.5 size fraction (particulate matter with a nominal aerodynamic diameter less than or equal to 2.5μm). Microscopy and size-distribution of mineral particles, soot aggregates, spherical particles and other particles (biomass, salt, fibers) in cafeteria and barbecue restaurant was studied by high resolution field emission scanning electron microscopy (FESEM) and image analysis technologies (IA). The FEEM analysis showed that minerals had regular and irregular shapes. In cafeteria, the mineral particles were dominated by number and volume, accounted for 69.23% and 80.13%, respectively. Minerals particles showed a bimodal number-size distribution, with a greater peak in 0.2-0.3μm range and lesser peak in 0.3-0.4μm range. The particle sizes less than 0.5μm accounted for 58.90% by number. In contrast, volume-size distribution exhibited a single peak in the range of 1-2.5μm, and that in the range of over than 0.5μm accounted for 70.48%. In barbecue restaurants, mineral and other particles were dominated by number for 45.67% and 44.86%, respectively. Mineral particles concentrated in 0.2-0.4μm range by number mainly. And in the range of less then 0.5μm accounted for 39.41%, the mineral particles in 1-2.5μm range had a considerable contribution, and in the range of large then 0.5μm accounted for 52.33% by volume-size distribution.