Deliquescence of malonic, succinic, glutaric, and adipic acid particles

Abstract

[1] In order to understand and predict the role of organic particles in the atmosphere their deliquescence behavior must be understood. Using an optical microscope coupled to a flow cell, we investigated the deliquescence of malonic, succinic, glutaric, and adipic acid particles with sizes ranging from 2 to 40 mm. Deliquescence relative humidities were determined for temperatures ranging from 293 to 243 K. Over this temperature range both succinic acid and adipic acid deliquesced at approximately 100% relative humidity, whereas malonic acid and glutaric acid deliquesced at significantly lower relative humidities. These results are generally in good agreement with previous studies and are within 3% of calculations based on the UNIQUAC (universal quasi-chemical) Functional Group Activity Coefficients (UNIFAC) model and recently published interaction parameters. Our studies also include measurements at temperatures below the eutectic temperatures. At these temperatures, ice did not nucleate; rather the particles underwent deliquescence to form metastable solution droplets. This indicates that solid dicarboxylic acids are not good ice nuclei above 243 K and hence will probably not play a role in ice cloud formation at these temperatures.

Liquid-liquid phase separation and morphology of internally mixed dicarboxylic acids/ammonium sulfate/water particles

“…This is in good agreement with previous work (Braban and Abbatt, 2004;Parsons et al, 2004;Sjogren et al, 2007;Ling and Chan 2008;Smith et al, 2011). Upon moistening, the C6/AS/H 2 O and C7/AS/H 2 O particles showed noticeably different behavior.…”

“…These ranges are at the high end or above ERH observed for other dicarboxylic acid/AS/H 2 O systems: e.g. Parsons et al (2004) and Zardini et al (2008) report ERH for malonic acid/AS, glutaric acid/AS, and citric acid/AS particles consistently below 40 %. A possible explanation for the high ERH values observed in this study might be an increase of the ion activity coefficients due to the energetically disadvantageous interactions between the ions of AS and the C6 and C7 dicarboxylic acids, enhancing the probability for the formation of stable AS crystal nuclei at higher RH as compared to mixtures with the more hydrophilic malonic (C3 dicarboxylic acid), glutaric (C5 dicarboxylic acid) and citric acids.…”

“…Ciobanu et al (2009) found that LLPS may occur by spinodal decomposition, nucleation-and-growth, and growth of a second phase at the surface of the particle depending on OIR within internally mixed PEG-400/AS/H 2 O particles. Nucleation-and-growth typically occurs in the metastable region of the phase diagram and is associated with overcoming an energy barrier to form stable nuclei of the second phase while spinodal decomposition occurs without a nucleation energy barrier at the border to the unstable region of the phase diagram (Shelby, 1995;Papon et al, 1999). To determine the different LLPS mechanisms from the microscopic images, we used the same methods as described by Ciobanu et al (2009), which rely on the analysis of droplet morphology at the onset of phase separation and the evaluation of the number of AS inclusions as a function of time.…”

The ice nucleation ability of one of the most abundant types of fungal spores found in the atmosphere

“…Experiments were carried out with a slightly modified apparatus to that used for ice nucleation experiments of organic materials (Parsons et al, 2004), mineral dust (Eastwood et al, 2008), and soot (Dymarska et al, 2006). The current method allows for observations of the freezing of spore-containing water droplets.…”

“…Fungal spores can also be transported over vast distances. By convection, they can reach high altitudes in the troposphere (Fulton, 1966;Fulton and Mitchell, 1966;Gregory, 1978;Heise and Heise, 1948;Hirst et al, 1967a, b;Pady and Kelly, 1953;Proctor, 1935 Fig. 1.…”