Effect of mixing structure on the water uptake of mixtures of ammonium sulfate and phthalic acid particles

Abstract

Abstract. Aerosol mixing state regulates the interactions between water molecules and particles and thus controls aerosol activation and hygroscopic growth, which thereby influences visibility degradation, cloud formation, and its radiative forcing. There are, however, few current studies on the mixing structure effects on aerosol hygroscopicity. Here, we investigated the hygroscopicity of ammonium sulfate / phthalic acid (AS / PA) aerosol particles with different mass fractions of PA in different mixing states in terms of initial particle generation. Firstly, the effect of PA coatings on the hygroscopic behavior of the core-shell-generated mixtures of AS with PA was studied using a coating hygroscopicity tandem differential mobility analyzer (coating HTDMA). The slow increase in the hygroscopic growth factor of core-shell-generated particles is observed with increasing thickness of the coating PA prior to the deliquescence relative humidity (DRH) of AS. At relative humidity (RH) above 80 %, a decrease in the hygroscopic growth factor of particles occurs as the thickness of the PA shell increases, which indicates that the increase of PA mass fractions leads to a reduction of the overall core-shell-generated particle hygroscopicity. In addition, the use of the Zdanovskii–Stokes–Robinson (ZSR) relation leads to the underestimation of the measured growth factors of core-shell-generated particles without consideration of the morphological effect of core-shell-generated particles, especially at higher RH. Secondly, in the case of the AS / PA initially well-mixed particles, a shift of the DRH of AS (∼80 %, Tang and Munkelwitz, 1994) to lower RH is observed due to the presence of PA in the initially well-mixed particles. The predicted hygroscopic growth factor using the ZSR relation is consistent with the measured hygroscopic growth factor of the initially well-mixed particles. Moreover, we compared and discussed the influence of mixing states on the water uptake of AS / PA aerosol particles. It is found that the hygroscopic growth factor of the core-shell-generated particles is slightly higher than that of the initially well-mixed particles with the same mass fractions of PA at RH above 80 %. The observation of AS / PA particles may contribute to a growing field of knowledge regarding the influence of coating properties and mixing structure on water uptake.

Modeling Volatility-Based Aerosol Phase State Predictions in the Amazon Rainforest

“…−0.8); however, OA concentrations are much smaller in the middle troposphere. It should be noted that hygroscopicity and water uptake by OA constituents could be impacted by uncertainty in the miscibility among various constituents of OA and the mixing state of aerosol . Recent work indicated that this uncertainty in miscibility and mixing state of OA constituents could modestly impact model-predicted OA .…”

“…It should be noted that hygroscopicity and water uptake by OA constituents could be impacted by uncertainty in the miscibility among various constituents of OA and the mixing state of aerosol. 98 Recent work indicated that this uncertainty in miscibility and mixing state of OA constituents could modestly impact model-predicted OA. 99 Hence, future work should try to account for these uncertainties especially in global-scale modeling that may deal with varied OA composition profiles and ambient conditions.…”

Single-particle Raman spectroscopy for studying physical and chemical processes of atmospheric particles

“…There are numerous hygroscopicity applications on various specific systems, including model inorganics, organ-Z. Liang et al: Single-particle Raman spectroscopy ics, and their mixtures (Chu et al, 2015;Laskina et al, 2015;W. Wang et al, 2021;Tobon et al, 2021;Ashraf et al, 2021), as well as mineral dust (Liu et al, 2008), secondary organic aerosols (Wu et al, 2020), and atmospherically relevant biological macromolecules (Mael et al, 2021), using single-particle Raman spectroscopy.…”

Important Oxidants and Their Impact on the Environmental Effects of Aerosols

“…Ammonium sulfate (AS) and ammonium nitrate (AN) are the two most abundant inorganic species in ambient aerosols, and their hygroscopicity has been well explored with various experimental techniques. For example, Ge’s group − has investigated the deliquescence and efflorescence properties of these inorganic salts using a hygroscopicity tandem differential mobility analyzer (HTDMA). They found that the deliquescence and efflorescence RH as well as the hygroscopic growth factors as a function of RH were highly consistent with previous studies and could be well predicted by thermodynamic equilibrium models.…”

“…In consideration of the complexity of organic compounds in ambient aerosols, a set of model organic surrogates have been identified and used in laboratory studies to be representative in reproducing the hygroscopic behavior of water-soluble organic compounds (WSOC) as well as investigate the influence of these organic compounds on the water uptake of inorganic–organic mixtures. Several categories of organic species have been used in previous studies, including (1) secondary products from photo-oxidation processes of precursors from anthropogenic sources, such as phthalic acid, benzoic acid, salicylic acids, and other aromatic acids; ,, (2) surrogates of biomass burning aerosols, including mono- and carboxylic acids, levoglucosan, 4-hydroxybenzoic acid, and humic acid; , (3) nitrogen-containing compounds, e.g., amino acids. − Additionally, other representative water-soluble compounds, such as oligomers (one of the major components detected in secondary organic aerosols), have been reported in a recent paper …”