The Cloud Condensation Nuclei (CCN) properties of 2-methyltetrols and C3–C6 polyols from osmolality and surface tension measurements

Atmospheric Chemistry and Physics (Impact Factor: 4.88). 01/2008; 8(5). DOI: 10.5194/acpd-8-17237-2008
Source: DOAJ


A significant fraction of the organic material in aerosols is made of highly soluble compounds such as sugars (mono- and polysaccharides) and polyols, including the 2-methyltetrols, methylerythritol and methyltreitol. The high solubility of these compounds has brought the question of their potentially high CCN efficiency. For the 2-methyltetrols, this would have important implications for cloud formation at global scale because they are thought to be produced by the atmospheric oxidation of isoprene. To investigate this question, the complete Köhler curves for C3–C6 polyols and the 2-methyltetrols have been determined experimentally from osmolality and surface tension measurements. Contrary to what expected, none of these compounds displayed a critical supersaturation lower than those of inorganic salts or organic acids. Their Raoult terms show that this limited CCN efficiency is due to their absence of dissociation in water, this in spite of slight surface-tension effects for the 2-methyltetrols. Thus, compounds such as sugars and polyols would not contribute more to cloud formation in the atmosphere than any other organic compounds studied so far. In particular, the presence of 2-methyltetrols in aerosols would not particularly enhance cloud formation in the atmosphere, contrary to what has been suggested.

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Available from: Barbara Noziere, Apr 25, 2015
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    • "Series of C 7 –C 15 monohydroxy fatty acids with OH group at C-5 to ω-1 positions have been reported as oxidation products of unsaturated fatty acids in the remote marine aerosols from the Pacific (Kawamura and Gagosian, 1988). Laboratory experiments (Ekström et al., 2009) have shown that 2-methyltetrols, tracers for isoprene SOA (Claeys et al., 2004), and related isoprene oxidation products can increase CCN levels in the pristine marine atmosphere that is limited in CCN. "
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    Marine Chemistry 10/2013; 148:22–32. DOI:10.1016/j.marchem.2012.11.002 · 2.74 Impact Factor
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    • "[4] Meskhidze and Nenes [2006] proposed that SOA formation from the oxidation of phytoplankton‐derived isoprene can affect the chemical composition of marine cloud condensation nuclei (CCN) and influence cloud droplet number. Laboratory experiments [Ekström et al., 2009] have shown that 2‐methyltetrols, tracers for isoprene SOA [Claeys et al., 2004a], and related isoprene oxidation products can increase CCN levels in the pristine marine atmosphere that is limited in CCN. However, recent modeling studies suggested that the oceanic isoprene source is not significant enough to control marine organic aerosols [Spracklen et al., 2008; Arnold et al., 2009; Gantt et al., 2009; Anttila et al., 2010; Luo and Yu, 2010]. "
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    • "To estimate the overall effect of these reactions on the formation of cloud droplets, the Köhler curves were determined for solutions 1/1 of methacrolein in ammonium sulfate, before irradiation and after 2 h of irradiation. The surface tension and osmolality of these two types of solutions and their subsequent dilutions were measured, and their Köhler curves were determined by a method described recently [Kiss and Hansson, 2004; Varga et al., 2007; Ekström et al., 2009] (see also Text S1). The results show that, for a particle of a dry diameter of 80 nm, for instance, the critical supersaturation, Sc, would decrease by about 13% after exposure to light. "
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