Effect of mixing structure on the hygroscopic behavior of ultrafine ammonium sulfate particles mixed with succinic acid and levoglucosan--颗粒学报PARTICUOLOGY

Maskey, S., Chong, K. Y., Kim, G., Kim, J.-S., Ali, A., & Park, K. (2014). Effect of mixing structure on the hygroscopic behavior of ultrafine ammonium sulfate particles mixed with succinic acid and levoglucosan. Particuology, 13, 27–34. https://doi.org/10.1016/j.partic.2013.08.004

Shila Maskey, Ka Yan Chong, Gibaek Kim, Jae-Seok Kim, Arshad Ali, Kihong Park^*

National Leading Research Laboratory, School of Environmental Science and Engineering, Gwangju Institute of Science and Technology (GIST), Gwangju, South Korea

10.1016/j.partic.2013.08.004

Volume 13, April 2014, Pages 27-34

Received 21 June 2013, Revised 27 August 2013, Accepted 29 August 2013, Available online 10 November 2013.

E-mail: kpark@gist.ac.kr

Highlights

• Hygroscopic properties of core-shell and well-mixed particles were measured.

• The shell hindered complete dissolution of the core-shell particles during hydration.

• Growth of core-shell particles was smaller than well-mixed particles under high RH.

• Mixing structure of particles affects their hygroscopic behavior.

Abstract

Understanding the interactions between water and atmospheric aerosols is critical for estimating their impact on the radiation budget and cloud formation. The hygroscopic behavior of ultrafine (<100 nm) ammonium sulfate particles internally mixed with either succinic acid (slightly soluble) or levoglucosan (soluble) in different mixing structures (core-shell vs. well-mixed) were measured using a hygroscopicity tandem differential mobility analyzer (HTDMA). During the hydration process (6–92% relative humidity (RH)), the size of core-shell particles (ammonium sulfate and succinic acid) remained unchanged until a slow increase in particle size occurred at 79% RH; however, an abrupt increase in size (i.e., a clear deliquescence) was observed at ∼72% RH for well-mixed particles with a similar volume fraction to the core-shell particles (80:20 by volume). This increase might occur because the shell hindered the complete dissolution of the core-shell particles below 92% RH. The onset RH value was lower for the ammonium sulfate/levoglucosan core-shell particles than the ammonium sulfate/succinic acid core-shell particles due to levoglucosan's higher solubility relative to succinic acid. The growth factor (GF) of the core-shell particles was lower than that of the well-mixed particles, while the GF of the ammonium sulfate/levoglucosan particles was higher than that of ammonium sulfate/succinic acid particles with the same volume fractions. As the volume fraction of the organic species increased, the GF decreased. The data suggest that the mixing structure is also important when determining hygroscopic behavior of the mixed particles.

Graphical abstract

Keywords

Ultrafine particles; Hygroscopicity; Mixing structure; Core-shell

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