Hygroscopicity and Compositional Evolution of Atmospheric Aerosols Containing Water-Soluble Carboxylic Acid Salts and Ammonium Sulfate: Influence of Ammonium Depletion.

Author(s) Wang, N.; Jing, B.; Wang, P.; Wang, Z.; Li, J.; Pang, S.; Zhang, Y.; Ge, M.
Journal Environ Sci Technol
Date Published 2019 06 04

Water-soluble organic acid salts are important components of atmospheric aerosols. Despite their importance, it is still not clear how water-soluble organic acid salts influence interactions between aerosols and water vapor in the atmosphere. In this study, the hygroscopic behaviors and chemical compositions of aerosol particles containing water-soluble organic acid salt ((CH) (COONa), n = 0, 1, 2) and (NH)SO were measured using in situ attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR). The ammonium depletion due to release of gaseous NH was found in mixed aerosols composed of (CH) (COONa) ( n = 1, 2) and (NH)SO upon dehydration. The ammonium loss could modify the aerosol composition, resulting in the formation of corresponding organic acid and monosodium dicarboxylate in mixed particles with high and low (NH)SO content, respectively. Due to the weaker hydrolysis of oxalate anions, the ammonium depletion was not observed for the NaCO/(NH)SO mixtures. The changes in the particle composition led to the decreased water uptake upon hydration as compared to that upon dehydration. Our findings reveal that interactions between water-soluble organic acid salts and (NH)SO in aqueous aerosols may affect the repartition of NH between the condensed and gas phases, thus modifying composition and physicochemical properties of aerosols as well as relevant chemical processes.

DOI 10.1021/acs.est.8b07052
Keywords Aerosols; Ammonium Compounds; Ammonium Sulfate; Salts; Wettability
ISSN 1520-5851
Citation Environ Sci Technol. 2019;53(11):62256234.

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