Weingartner E, Gysel M, Baltensperger U
Laboratory of Atmospheric Chemistry, Paul Scherrer Institut, Villigen, Switzerland.
Environ Sci Technol. 2002 Jan 1;36(1):55-62. doi: 10.1021/es010054o.
A hygroscopicity tandem differential mobility analyzer (H-TDMA) is described that allows a fast and accurate determination of the water uptake by submicrometer aerosol particles at temperatures below 0 degrees C. To avoid volatilization of semivolatile particles, the humidification works without heating the gas stream, and the gas-phase composition is not changed during the analysis. The applied scanning mobility analysis allows a fast and accurate measurement of the humidogram, but care has to be taken with too high scanning velocities leading to artifacts in the particle size measurement. During a field campaign at a high-alpine site (Jungfraujoch, 3580 m above sea level), humidograms of free tropospheric particles were measured at T= -10 degrees C. The hygroscopic growth of these particles was characterized by monomodal growth distributions, which means that in the observed size range (dry particle diameters (Do) = 50-250 nm) the free tropospheric aerosol was to a large extent internally mixed. No distinct deliquescence was observed, indicating that the multicomponent aerosol particles are present in a liquid state even at a low relative humidity (RH) <10%. At RH 85%, average hygroscopic growth factors of 1.44, 1.49, and 1.53 were measured for Do = 50, 100, and 250 nm. The estimated soluble volume fraction of the particles in the observed size range was found to be 0.79, 0.86, and 0.91, respectively.
本文描述了一种吸湿串联差分迁移率分析仪（H-TDMA），它能够在0摄氏度以下的温度下快速准确地测定亚微米气溶胶颗粒的吸水量。为避免半挥发性颗粒挥发，加湿过程中不加热气流，且分析过程中气相成分不变。所应用的扫描迁移率分析能够快速准确地测量吸湿图，但需注意扫描速度过高会导致粒径测量出现伪像。在一次高海拔地区（少女峰，海拔3580米）的实地考察中，在T = -10摄氏度下测量了自由对流层颗粒的吸湿图。这些颗粒的吸湿增长以单峰增长分布为特征，这意味着在观测到的粒径范围内（干颗粒直径（Do）= 50 - 250纳米），自由对流层气溶胶在很大程度上是内部混合的。未观察到明显的潮解现象，这表明即使在低相对湿度（RH）<10%时，多组分气溶胶颗粒也以液态存在。在RH 85%时，对于Do = 50、100和250纳米，测得的平均吸湿增长因子分别为1.44、1.49和1.53。在所观测粒径范围内，颗粒的估计可溶体积分数分别为0.79、0.86和0.91。
