针对大气颗粒物的粒径分布特征，在2006年5月于济南市城区进行大约两周的观测。小于200nm的细颗粒物浓度达到10500个/cm3，超细颗粒物在PM2.5个数浓度中所占比例较大，达到95%。凝结核模态与埃根核模态颗粒物在大气环境相对清洁、高温度和低湿度环境下浓度较高，可能主要是由气态前体物在光化学作用下的均相成核作用及异相凝结浓缩作用推动的。颗粒物个数及相关污染物的浓度日夜变化研究表明：超细颗粒物的前体物主要是二氧化硫，而粒径大于200nm的颗粒物可能来源是交通扬尘污染。

The observation of particle number concentration and size distribution has been conducted for two weeks in May of 2006 in the downtown Ji’nan. It has been found that the number concentration of particles smaller than 200nm got the half hour average concentration of 10500cm-3. The percentage of the number concentration of ultrafine particles (Dp<100nm) was found to be 95%, which is much higher than what have been observed in other continental sites. The relative clean air condition with high temperature and low relative humidity provided the favorable condition for the formation and growth of ultrafine particles. And the nucleation processes were thought to be promoted mainly by homogeneous nucleation and heterogeneous condensation of precursor gas or vapors on pre-existing particles. The diurnal variations of particle number concentration and relative pollutants were also studied. High consistency of profile of SO2 and particles smaller than 200nm proved that SO2 played a key role in new particle formation. The particles whose diameter is larger than 200nm were thought to be caused by road dust.