华北南部冬季大气亚微米颗粒物数浓度变化

2018年1月华北平原经历了一段持续时间久、影响范围广和颗粒物浓度高的重污染时期.本研究通过SMPS+E扫描电迁移率粒径谱仪，选取华北平原南部某郊区点位，对此次重污染期间颗粒物数浓度粒径分布演化进行连续观测研究.结果表明，观测期间环境空气质量尤其是PM_2.5平均浓度为141.32 μg/m³.大气亚微米颗粒物数浓度主要集中在核模态和爱根核模态的超细粒径段（78.9%），呈递减型单峰分布，颗粒物平均数浓度为83174cm^-3.重污染天时，核模态颗粒物数浓度明显增高，对应低风速（1.5±0.4）m/s、高相对湿度（90.8±4.5）%和低O₃浓度（15.8±8.3）μg/m³.48h后向轨迹显示，观测点位气溶胶主要受湖北省、陕西省和山西省临近省份的传输影响.潜在源贡献因子法和浓度权重轨迹表明，气溶胶潜在源区主要为本地源和观测点位以北的区域.

Number concentration of submicron particles during winter at a suburban site of the south edge of North China

There was a period of heavy pollution at North China Plain in January 2018 characterized by long duration, wide range of influence and high particle number concentration. To obtain its submicron particle number size distribution during this period, a Scanning Mobility Particle Sizer (SMPS) was deployed for a continuously monitoring at a typical suburban site in the south edge of this area. The results indicated that average mass concentration of PM_2.5 was 141.32μg/m³. Particle size distribution was mainly concentrated on the ultrafine size range (78.9%) of the Nucleation mode and Atiken mode, showing a decreasing unimodal distribution, and average particle number concentration was 83174cm^-3. During the heavy pollution period, particle number concentration of Nucleation mode was obviously increased, accompanied by high relative humidity (90.8±4.5)%, low wind speed (1.5±0.4) m/s and low concentration of O₃ (15.8±8.3) μg/m³ conversely. The clustered 48h backward trajectories showed that air masses of observation site were mainly affected by the transportation of Hubei Province, Shaanxi Province and Shanxi Province. While the potential source regions were located at the local site and the north of the observation site based on potential source contribution function and concentration-weighted trajectory analysis.