Hygroscopic behavior of atmospherically relevant water-soluble carboxylic salts and their influence on the water uptake of ammonium sulfate

Abstract

Abstract. The hygroscopic behavior of atmospherically relevant water-soluble carboxylic salts and their effects on ammonium sulfate were investigated using a hygroscopicity tandem differential mobility analyzer (H-TDMA). No hygroscopic growth is observed for disodium oxalate, while ammonium oxalate shows slight growth (growth factor = 1.05 at 90 %). The growth factors at 90 % RH for sodium acetate, disodium malonate, disodium succinate, disodium tartrate, diammonium tartrate, sodium pyruvate, disodium maleate, and humic acid sodium salt are 1.79, 1.78, 1.69, 1.54, 1.29, 1.70, 1.78, and 1.19, respectively. The hygroscopic growth of mixtures of organic salts with ammonium sulfate, which are prepared as surrogates of atmospheric aerosols, was determined. A clear shift in deliquescence relative humidity to lower RH with increasing organic mass fraction was observed for these mixtures. Above 80 % RH, the contribution to water uptake by the organic salts was close to that of ammonium sulfate for the majority of investigated compounds. The observed hygroscopic growth of the mixed particles at RH above the deliquescence relative humidity of ammonium sulfate agreed well with that predicted using the ZdanovskiiStokes-Robinson (ZSR) mixing rule. Mixtures of ammonium sulfate with organic salts are more hygroscopic than mixtures with organic acids, indicating that neutralization by gas-phase ammonia and/or association with cations of dicarbonxylic acids may enhance the hygroscopicity of the atmospheric particles.

Hygroscopicity of organic compounds from biomass burning and their influence on the water uptake of mixed organic ammonium sulfate aerosols

“…However, mix-bio-dry particles begin to take up water at 65 % RH and show steep growth between 75 % and 80 % RH where the partial deliquescence of AS contributes increasingly to the water uptake and, hence, the overall growth factor. Similar water uptake behavior prior to full AS deliquescence has been reported by Zardini et al (2008) and Wu et al (2011) for different organic + ammonium sulfate mixed aerosol systems. The E-AIM model prediction for mixtures consisting of ammonium sulfate + levoglucosan with a comparable dry mass percentage ratio of 68 wt % : 26 wt % is in relatively good agreement with the measured growth factors above 75 % RH, this reveals that levoglucosan, as part of the mixture of organic biomass burning organic surrogate compounds, largely contributes to the water uptake of mixtures containing organic surrogate compounds and ammonium sulfate before the deliquescence of AS.…”

“…This result is expected given the lower mass fraction of hygroscopic organics (e.g., only 9.2 wt % levoglucosan) in the mix-bio-wet particles. The observed hygroscopic behavior of mixed organic-inorganic aerosols of other HTDMA studies on biomass burning aerosols published in the literature, e.g, Wu et al (2011), cannot be compared directly to our measurements, because the samples and organic : inorganic rations are different. However, the work by Wu et al (2011) shows that other mixtures containing AS and organic acids found in biomass burning aerosol from Brazil, show significant water uptake at relative humidities below 80 %, similar to our mix-bio-dry case.…”

“…The observed hygroscopic behavior of mixed organic-inorganic aerosols of other HTDMA studies on biomass burning aerosols published in the literature, e.g, Wu et al (2011), cannot be compared directly to our measurements, because the samples and organic : inorganic rations are different. However, the work by Wu et al (2011) shows that other mixtures containing AS and organic acids found in biomass burning aerosol from Brazil, show significant water uptake at relative humidities below 80 %, similar to our mix-bio-dry case. In addition, the E-AIM model prediction for mixtures consisting of AS and levoglucosan by mass percentage ratio of 87 wt % : 9.2 wt % is in good agreement with the measured growth curve, which indicates that levoglucosan mainly contributes to the hygroscopic behavior of the organic aerosol fraction of the mixtures consisting of biomass burning model organics and AS.…”

“…Recently several groups have reported that a significant portion of particles in biomass burning (from 11 % to as high as 99 % by mass) consist of water-soluble organic carbon (WSOC) (Ruellan et al, 1999;Novakov and Corrigan, 1996;Narukawa et al, 1999;Hoffer et al, 2006;Iinuma et al, 2007;Fu et al, 2009;Claeys et al, 2010;Dusek et al, 2011;Psichoadaki and Pandis, 2013). One way to handle the large number of organic compounds comprised within the water-soluble atmospheric aerosol fraction is to identify a set of model substances that may be representative in reproducing the hygroscopic behavior of the water-soluble organic fraction of the real aerosol particles (May-Bracero et al, 2002;Rissler et al, 2010;Wu et al, 2011;Zamora and Jacobson, 2013). For example, based on the identification of model compounds with the help of chromatographic chemical separation, HNMR (proton nuclear magnetic resonance) analysis and TOC (total organic carbon) measurements, Andreae et al (2002) studied the chemical composition of the WSOC fraction of particles generated by biomass burning and divided these detected WSOC into three different classes: (1) neutrals (N), (2) monocarboxylic and dicarboxylic acids (MDA), and (3) polycarboxylic acids (PA).…”

Particle hygroscopicity and its link to chemical composition in the urban atmosphere of Beijing, China, during summertime

“…The H-TDMA used in this study has been described in detail in previous publications (Wu et al, 2011;Massling et al, 2003), and complied to the instrumental standards and Atmos. Chem.…”