Morphological effects on the hygroscopic properties of sodium chloride-sodium sulfate aerosols

作者：Darr Joshua P^*; Davis Shannon Q; Kohno Yohei; McKenna Kevin; Morales Paul

来源：Journal of Aerosol Science, 2014, 77: 158-167.

DOI：10.1016/j.jaerosci.2014.08.002

• Morphology
• Hygroscopicity
• Sodium chloride aerosol
• Sodium sulfate aerosol
• Infrared spectroscopy
• Metastable phase

The hygroscopic properties of sodium sulfate, Na2SO4; sodium chloride, NaCl; and their mixed aerosols are monitored using a flow-cell apparatus and Fourier-transform infrared spectroscopy. While Na2SO4 exhibits the typical water uptake for an inorganic salt, spectra of NaCl and mixed NaCl-Na2SO4 aerosols reveal water content below the deliquescence relative humidity. This is explained on the basis of two different morphologies for NaCl and Na2SO4. While Na2SO4 can be described by a simple crystalline solid, NaCl contains pockets that trap water. The NaCl-Na2SO4 mixtures contain a combination of these two structural motifs, weighted by the relative amounts of the NaCl and Na2SO4 components. This makes NaCl-Na2SO4 mixtures an interesting candidate for exploring the effects of morphology on atmospherically relevant properties in a systematic fashion. Additionally, the formation of metastable Na2SO4 (III) is confirmed using Raman spectroscopy, though its effects on the hygroscopicity of NaCl-Na2SO4 mixtures are believed to be minimal.

• 出版日期2014-11