Interactions of organosulfates with water vapor under sub- and supersaturated conditions

Abstract

Abstract. Organosulfates (OSs) are important constituents of secondary organic aerosols, but their hygroscopic properties and cloud condensation nucleation (CCN) activities have not been well understood. In this work we employed three complementary techniques to characterize interactions of several OSs with water vapor under sub- and supersaturated conditions. A vapor sorption analyzer was used to measure mass changes in OS samples with relative humidity (RH, 0 %–90 %); among the 11 organosulfates examined, only sodium methyl sulfate (methyl-OS), sodium ethyl sulfate (ethyl-OS), sodium octyl sulfate (octyl-OS) and potassium hydroxyacetone sulfate were found to deliquesce as RH increased, and their mass growth factors at 90 % RH were determined to be 3.65 ± 0.06, 3.58 ± 0.02, 1.59 ± 0.01 and 2.20 ± 0.03. Hygroscopic growth of methyl-, ethyl- and octyl-OS aerosols was also studied using a humidity tandem differential mobility analyzer (H-TDMA); continuous hygroscopic growth was observed, and their growth factors at 90 % RH were determined to be 1.83 ± 0.03, 1.79 ± 0.02 and 1.21 ± 0.02. We further investigated CCN activities of methyl-, ethyl- and octyl-OS aerosols, and their single hygroscopicity parameters (κccn) were determined to be 0.459 ± 0.021, 0.397 ± 0.010 and 0.206 ± 0.008. For methyl- and ethyl-OS aerosols, κccn values agree reasonably well with those derived from H-TDMA measurements (κgf) with relative differences being < 25 %, whereas κccn was found to be ∼ 2.4 times larger than κgf for octyl-OS, likely due to both the solubility limit and surface tension reduction.

A Single Parameter Hygroscopicity Model for Functionalized and Insoluble Aerosol Surfaces

“…𝜅𝜅 𝑖𝑖𝑖𝑖𝑖𝑖 = 𝜅𝜅 𝑅𝑅𝑇𝑇 = 0.604 for ammonium sulfate (Rose et al, 2008). The intrinsic and experimentally derived 165 values also agree well for water-soluble compounds and partially soluble organics (Dawson et al, 2020;Peng et al, 2021Peng et al, , 2022.…”

Insights into the role of dicarboxylic acid on CCN activity: implications for surface tension and phase state effects

“…Surface tension reduction in water solution caused by atmospheric surfactants were observed frequently in previous studies (Facchini et al, 1999;Gerard et al, 2016). Results have showed that neglect of surface tension reduction may lead to higher CCN values than Chem or growth factor derived GF (Irwin et al, 2010;Wu et al, 2013;Zhao et al, 2016;Hu et al, 2020;Peng et al, 2021), as well as underpredictions of CCN number concentration (Good et al, 2010;Asa-Awuku et al, 2011;Ovadnevaite et al, 2017;Cai et al, 2020). Hu et al (2020) reported that Chem underpredicted CCN by 13% and 18% at supersaturation ratios of 0.1% and 0.3%, which may be attributed to the depression of droplet surface tension by potential surface-active organics.…”

Second-Order Kinetic Rate Coefficients for the Aqueous-Phase Sulfate Radical (SO4•–) Oxidation of Some Atmospherically Relevant Organic Compounds

“…SO 4 •– radicals have been recognized as a potentially important source of surface-active organosulfates (OSs) in the environment, 7 − 10 which can modify aerosol cloud interactions. 11 , 12 A large variety of OSs have been identified in both field and laboratory studies, several of which are proposed to only be formed from SO 4 •– radicals. 9 , 13 − 17 The SO 4 •– radical is thought to be formed primarily in the autoxidation of SO 2 ; however, it can also be formed from the activation of sulfate and bisulfate anions with OH, NO 3 , 4 and to a small extent ferric ion complexes.…”

“…•− radicals have been recognized as a potentially important source of surface-active organosulfates (OSs) in the environment, 7−10 which can modify aerosol cloud interactions. 11,12 A large variety of OSs have been identified in both field and laboratory studies, several of which are proposed to only be formed from SO 4…”