利用3nm～20μm颗粒物粒径分布测量仪对南宁市大气颗粒物粒径分布特征进行研究

Study on atmospheric particle size distribution by particle size distribution system in the range of 3 nm～20 μm in Nanning

利用颗粒物粒径分布测量仪(particle size distribution system,PSD)对南宁市2016年11月15日—12月4日大气颗粒物进行实时监测,分析颗粒物数浓度、粒径分布特征及其与颗粒物质量浓度的关系.结果表明,南宁市3 nm^20μm颗粒物平均数浓度为3269个·cm-3,粒径呈双峰分布,主峰值出现在28 nm左右,次峰值出现在100 nm左右.颗粒物数浓度随时间变化呈现一定规律,即早上8:00—10:00和晚上18:00—20:00左右出现浓度高值,这与早晚高峰有关.新粒子一般在16:00~18:00左右开始生成,18:00—20:00左右逐渐长大,并在夜间至凌晨保持较高的浓度.南宁市监测期间新粒子生成与机动车尾气排放有关.颗粒物质量浓度越大对应的数浓度也相应较高,较大粒径颗粒物对质量浓度贡献较大.降雨和风速加大过程对颗粒物数浓度下降有影响;温度和湿度对颗粒物数浓度影响不明显.

Continuous online measurements for atmospheric particulates were performed in Nanning from November 15 to December 4,2016 using the Particle Size Distribution system（ PSD）. Characteristics of particle number concentration, size distribution and the relationships with the mass concentration of particulate matter were analyzed. The results showed that number concentration of particle in the range of 3 nm ~ 20 μm were averaged at3269 per cubic centimeter during the observation. The particle size distribution in the range of 3 nm ~ 20 μm was bimodal. The main peak particle size appeared in about 28 nm,second peak at about 100 nm. Particle number concentration peaked at 08： 00—10： 00 and 18： 00—20： 00,which is related to the traffic rush hours in morning and evening,respectively. New particles generally started generating around 16： 00—18： 00,gradually grew up at about18： 00—20： 00,and kept at relatively high concentration all the night. New particle formation were found to be related to vehicle exhaust emissions directlyat this monitoring site in Nanning. The higher particle mass concentration,the greater particle number concentration. And the larger diameter particles contributed more to the particle mass concentration. The decreases of particle number concentration were favor of rain and wind speed increasing process,however,less impacted by the temperature and humidity.