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- Title
Investigation of water adsorption and hygroscopicity of atmospheric particles using a commercial vapor sorption analyzer.
- Authors
Wenjun Gu; Yongjie Li; Jianxi Zhu; Xiaohong Jia; Qinhao Lin; Guohua Zhang; Xiang Ding; Wei Song; Xinhui Bi; Xinming Wang; Mingjin Tang
- Abstract
Water adsorption and hygroscopicity are among the most important physicochemical properties of aerosol particles, largely determining their impacts on atmospheric chemistry, radiative forcing, and climate. Measurements of water adsorption and hygroscopicity of nonspherical particles under subsaturation conditions are non-trivial because many widely used techniques require the assumption of particle sphericity. In this work we describe a method to directly quantify water adsorption and mass hygroscopic growth of atmospheric particles for temperature in the range of 5-30?°C, using a commercial vapor sorption analyzer. A detailed description of instrumental configuration and experimental procedures, including relative humidity (RH) calibration, are provided first. It is then demonstrated that for (NH4)2SO4 and NaCl, deliquescence relative humidities (DRHs) and mass hygroscopic growth factors measured using this method show good agreements with experimental and/or theoretical data from literature. To illustrate its ability to measure water uptake by particles with low hygroscopicity, we used this instrument to investigate water adsorption by CaSO4?∙?2H2O as a function of RH at 25?°C. The mass hygroscopic growth factor of CaSO4?∙?2H2O at 95?% RH, relative to that under dry conditions (RH?<?1?%), was determined to be (0.450?±?0.004)?% (1?σ). In addition, it is shown that this instrument can reliably measure a relative mass change of 0.025?%. Overall, we have demonstrated that this commercial instrument provides a simple, sensitive, and robust method to investigate water adsorption and hygroscopicity of atmospheric particles.
- Subjects
ADSORPTION capacity; RADIATIVE forcing
- Publication
Atmospheric Measurement Techniques Discussions, 2017, p1
- ISSN
1867-8610
- Publication type
Article
- DOI
10.5194/amt-2017-56