元宵节期间北京PM_(2.5)单颗粒的物理化学特征

Physicochemical characteristics of individual particle in PM_(2.5) of Beijing during the Lantern Festival

采集2014年元宵节期间北京PM2.5样品,使用场发射扫锚电镜-能谱仪观察北京PM2.5单颗粒的显微形貌和元素组成,并利用图像分析系统对PM2.5的粒径进行分析.结果表明:PM2.5的单颗粒类型以烟尘集合体、矿物颗粒和飞灰为主;烟花爆竹燃放产生的PM2.5是造成元宵节期间北京PM2.5浓度升高的主要原因;PM2.5中总颗粒物个数呈现先升高后降低的趋势;元宵节期间北京PM2.5中大部分颗粒物的粒径小于0.7μm;然而,重污染天气PM2.5中粒径大于0.7μm颗粒物的数量明显高于轻污染天气.

PM2.5 samples in Beijing were collected during the Lantern Festival of 2014. Morphologies and elemental compositions of individual particles were determined by Field Emission Scanning Electron Microscopy coupled with Energy Dispersive X-ray Spectrometer（FESEM-EDX）. Size distribution of individual particles in FESEM images were further analyzed by an image analysis system. The result shows that soot aggregate, mineral and fly ash were dominant particles. Particles generated by the fireworks and firecrackers in Beijing can lead to PM2.5 concentrations increase during the Lantern Festival. The particle number firstly behaved one increase and then decrease. Particle size mostly displayed less than 0.7μm during the lantern festival. However, the particle number with the diameter 〉0.7μm in the heavy pollution period was significantly higher than them in the light pollution period.