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The Cloud Condensation Nuclei (CCN) properties of 2-methyltetrols and C3-C6 polyols from osmolality and surface tension measurements
Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
2009 (English)In: Atmospheric Chemistry And Physics, ISSN 1680-7316, Vol. 9, no 3, 973-980 p.Article in journal (Refereed) Published
Abstract [en]

A significant fraction of the organic material in aerosols is made of highly soluble compounds such as sugars (mono-and polysaccharides) and polyols such as the 2-methyltetrols, methylerythritol and methyltreitol. Because of their high solubility these compounds are considered as potentially efficient CCN material. 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 Kohler curves for C3-C6 polyols and the 2-methyltetrols have been determined experimentally from osmolality and surface tension measurements. Contrary to what was expected, none of these compounds displayed a higher CCN efficiency than 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 saccharides and polyols would not contribute more to cloud formation than other organic compounds studied so far. In particular, the presence of 2-methyltetrols in aerosols would not particularly enhance cloud formation in the atmosphere, in contrary to recently suggested

Place, publisher, year, edition, pages
2009. Vol. 9, no 3, 973-980 p.
Keyword [en]
National Category
Natural Sciences
URN: urn:nbn:se:su:diva-34964DOI: 10.5194/acp-9-973-2009ISI: 000263325900016ISBN: 1680-7316OAI: diva2:285998
Available from: 2010-01-13 Created: 2010-01-13 Last updated: 2012-03-27Bibliographically approved
In thesis
1. The influence of biogenic organic compounds on cloud formation
Open this publication in new window or tab >>The influence of biogenic organic compounds on cloud formation
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Aerosols and clouds provide the largest uncertainty in the atmospheric radiation budget. The main focus of this thesis was to investigate the ability of organic compounds in aerosol particles to form clouds, and more specifically those emitted by living organisms.

The cloud forming properties of the highly water-soluble methyltetrols and polyols, which are compounds produced by plants and fungi that are common in aerosol, were studied. All compounds and their salt mixtures have a moderate potential to serve as cloud condensation nuclei (CCN). They are thus not likely to have a significant global impact on cloudiness.

The potential presence of surfactants released by microorganisms was investigated for aerosols sampled at different locations. Very low surface tension values were measured for these aerosol extracts (30 mN/m), which implies that these aerosols have good CCN properties and indicate the presence of biosurfactants. Their occurrence in aerosols still needs to be confirmed directly by chemical identification.

Reactions of organic compounds in sulfate salt solutions exposed to UV-light were studied and found to produce surface active compounds. Thus, mixed sulfate/organic aerosol could have more favourable CCN properties after exposure to light than when kept in the dark. The surface active compounds were proposed to be long-chained organosulfates with hydrophilic and hydrophobic parts, similar to other amphiphilic surfactants.

Mixtures of salt and strong surfactants formed by bacteria were studied using two different techniques for determining their CCN properties. There were inconsistencies between the two methods which could be accounted for by surface partitioning. The studied mixtures were determined to be good potential CCN material in both techniques.

All these aspects require further investigation, but if the impact of strong biogenic surfactants on cloud formation is confirmed, a new link between living organisms and climate would be identified.

Place, publisher, year, edition, pages
Stockholm: Department of Applied Environmental Science (ITM), Stockholm University, 2010. 43 p.
biogenic, aerosol, CCN, water-soluble, microorganisms, surfactant, organosulfate
National Category
Natural Sciences
Research subject
Applied Environmental Science
urn:nbn:se:su:diva-45714 (URN)978-91-7447-175-5 (ISBN)
Public defence
2010-12-17, De Geersalen, Geovetenskapens hus, Svante Arrhenius väg 14, Stockholm, 10:00 (English)
At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 4: Manuscript. Available from: 2010-11-25 Created: 2010-11-10 Last updated: 2010-11-30Bibliographically approved

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Ekström, SannaNozière, BarbaraHansson, Hans-Christen
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