近地面大气颗粒物粒度与粒形特征

选择大气颗粒物污染代表性城市石家庄市,利用挂片法采集采暖期与非采暖期大气颗粒物样品,在CIS-50粒度粒形仪上进行视频通道测试,并利用扫描电镜对颗粒表面形态进行观察,得出颗粒物粒度分布、粒形参数及形貌特征.结果显示,大气颗粒物粒度分布为连续多峰曲线形态,粒径范围为0.8～120 μm,集中于10 μm以下,粒度均值变化为4.086 0～7.622 7 μm,标准差随粒度均值增大而增大;粒形参数中形状因子均值变化为0.718 3～0.899 3,分维度均值变化为1.041 1～1.072 0.上述数据均呈现在非采暖期间小于采暖期间的特征.扫描电镜观察表明大气颗粒物多为表面粗糙的块状形貌,粒度较大;团聚状次之,并呈粗、细2种团聚形态;球体颗粒粒度最小.分析认为,石家庄市近地面大气颗粒物粒度粒形变化受地面排放影响强烈,采暖期新增颗粒物粒度为5～8 μm,粒形为近圆形及圆形,呈聚合体形态;PM₅数量比与近方形及正方形颗粒数量比呈较好正相关,r 为0.945 8,与近圆形及圆形颗粒数量比呈负相关,r 为-0.972 6,PM₅在大气颗粒物粒度粒形变化中可能有重要影响.

Size Distribution and Shape Characteristics of Subaerial Airborne Particles

This research sampled airborne particles in the typical air polluted city of Shijiazhuang to measure the particle size and shape by the instrument of the CIS-50 and the scan electronic microscope in the non-heating period and heating period. The results show that the subaerial airborne particle size distribution mode is coarse with the size range of 0.8-120 microm, mostly under 10 microm, and the semi-square & square like particle shape is dominant, the sphere like lesser, the acute-angle and lathy like sparse. There exist particle size and shape difference in the non-heating period and heating period influenced greatly by the ground emission. When in the heating period, the particle size average value increases by 53.2% principally in the size range of 5-8 microm, and 10-30 microm secondly. Meanwhile, the number of particles with semi-sphere & sphere like shape increases obviously. These semi-sphere particles are agglomerate of finer spheres derived from combustion in the SEM images. The relationship between particle size and shape is demonstrated by that the percentage of PM5 and the one of the semi-square & square like particles are positively correlative with the r of 0.9458; the one of the semi-sphere & sphere like particles negatively correlative with the r of -0.972 6 respectively.