Investigation of water adsorption and hygroscopicity of atmospherically relevant particles using a commercial vapor sorption analyzer
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 subsatu...
| Main Authors: | , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2017-10-01
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| Series: | Atmospheric Measurement Techniques |
| Online Access: | https://www.atmos-meas-tech.net/10/3821/2017/amt-10-3821-2017.pdf |
| Summary: | 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 subsaturated conditions are nontrivial 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, is provided first. It is then
demonstrated that for (NH<sub>4</sub>)<sub>2</sub>SO<sub>4</sub> and NaCl, deliquescence relative humidities 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
CaSO<sub>4</sub> ⋅ 2H<sub>2</sub>O as a function of RH at 25 °C. The mass hygroscopic growth factor of
CaSO<sub>4</sub> ⋅ 2H<sub>2</sub>O at 95 % RH, relative to that under dry conditions (RH < 1 %), was determined to be
(0.450±0.004) % (1<i>σ</i>). 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. |
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| ISSN: | 1867-1381 1867-8548 |