气溶胶吸湿和挥发特性测量的VH-TDMA装置研究

摘要

A volatility hygroscopic tandem differential mobility analyzer (VH-TDMA) was developed and used to measure and research the actual aerosol hygroscopic and thermal properties.The heating unit equipped with four symmetric heating tubes worked at 25℃C,150℃C,250℃C and 350℃C,respectively.With rapid switching of the samples between different heating tubes,a higher temporal resolution could be achieved compared to regular V-TDMA.The humidification unit humidified the aerosol sample by using Nation tubes.The relative humidity (RH) of the sample was controlled within the range of 10％ to 90％ with an accuracy of l％.The particle loss and the accuracy of the developed system were evaluated with laboratory generated sodium chloride and ammonium sulfate samples.The measured results were in good agreement with those literature reported values,which confirmed that the developed VH-TDMA system was suitable for accuracy measurement of the hygroscopic and thermal properties of atmospheric aerosols.Field application of the system was carried out at the Shouxian National Climate Observatory in Anhui Province.The hygroscopic properties and volatilization characteristics of summer aerosol were studied.The results showed a positive correlation between the aerosol hygroscopic growth factor and particle size,and a pronounced diurnal cycle of the mixing state of the carbonaceous aerosol was observed.%设计搭建了一套挥发性吸湿性-串联差分电迁移率分析仪(VH-TDMA)装置,并将其用于实际大气气溶胶吸湿和挥发特性测量研究.挥发特性测量单元由4根加热管并列组成,加热温度分别设为25,1 50,250,350℃C,可实现不同加热温度之间的快速切换,与传统的VTDMA相比,可以获得更高的时间分辨;吸湿特性测量单元利用全氟磺酸管对气溶胶样品进行加湿处理,相对湿度在10％～90％范围可控,加湿精度为1％.利用实验室气溶胶发生系统产生的氯化钠和硫酸铵气溶胶,对该装置的粒子损耗、挥发及吸湿特性测量的准确性进行了评估,测量结果与文献报道值一致,验证了系统的可靠性和准确性.将该装置运用于外场综合观测实验中,在安徽省寿县国家气候观象台对夏季大气溶胶的吸湿和挥发特性开展了测量研究.结果表明,该地区气溶胶的吸湿生长因子与粒径正相关,含碳气溶胶的混合态呈现明显的日变化趋势.