实验室发生纳米气溶胶吸湿性表征

气溶胶吸湿特性对于灰霾的形成、气溶胶对气候变化的影响及人体健康效应具有重要意义.采用加湿迁移差分分析(HTDMA)法,对实验室发生的8种纳米级无机和有机气溶胶进行吸湿特性定量表征,从而判定影响气溶胶吸湿特性的主要因素.结果表明,NaCl和(NH4)2SO4气溶胶的潮解点为相对湿度(RH)75%±2%,与理论计算结果相接近,说明测试系统具有一定的可靠性.对以往研究较少的NaNO3,CaCl2,CaSO4,合成海盐,乙二酸和己二酸气溶胶的测试表明,NaNO3,CaCl2以及合成海盐气溶胶随RH的升高粒径逐渐增大;合成海盐气溶胶在RH为86%时吸湿性生长因子(Gf)达到1.80;CaSO4,乙二酸和己二酸气溶胶随着RH增大未见明显吸湿增长.通过扫描电镜分析了8种化合物气溶液在不同RH下的形态特征,为掌握各种化学组分对气溶胶吸湿特性的影响提供了微观形态分析的依据.

Characterization of Hygroscopic Properties of Laboratory-Generated Nanometer Aerosols

The hygroscopic properties of aerosols affect haze formation,the direct and indirect effects of aerosols on climate,and health effects in the human respiratory tract.Using the HTDMA(Hygroscopic Tandem Differential Mobility Analyzer) system,the hygroscopic properties of eight kinds of laboratory-generated nanometer-scale inorganic and organic aerosols were characterized quantitatively for determining the main factors affecting the hygroscopicity of ambient aerosols.It was found that the deliquescence points of inorganic compounds NaCl and(NH4)2SO4 were about 75% ± 2% RH,similar to the theoretical results,which showed that the HTDMA system was reliable to a certain extent.The hygroscopicity of NaNO3,CaCl2,CaSO4,synthetic sea salt,oxalic acid and adipic acid,which have seldom been studied,were also measured.The results showed that the particle sizes of NaNO3,CaCl2 and synthetic sea salt shifted to larger sizes when the RH(relative humidity) gradually increased,with a growth factor of 1.8 for synthetic sea salt at 86% RH.In contrast,obvious increases in the sizes of CaSO4,oxalic acid and adipic acid were not observed with the increase of RH.Additionally,the morphological characteristics of the eight compounds under different RHs were also investigated by Scanning Electron Microscope(SEM) analysis,which provided micro morphological analysis bases for determining the influence of chemical components on the hygroscopicity of ambient aerosols.