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Radical-initiated formation of organosulfates and surfactants in atmospheric aerosols
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).
Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology (INK).
2010 (English)In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 37, no L05806Article in journal (Refereed) Published
Abstract [en]

Many atmospheric aerosols contain both organic compounds and inorganic material, such as sulfate salts. In this work, we show that these sulfates could trigger some chemical transformations of the organic compounds by producing sulfate radicals, SO4, when exposed to UV light (280–320 nm). In particular, we show by mass spectrometry (LC/ESI-MSMS) that isoprene, methyl vinyl ketone, methacrolein, and α-pinene in irradiated sulfate solutions (ammonium and sodium sulfate) produce the same organosulfates as previously identified in aerosols, and even some that had remained unidentified until now. With a typical time constant of 9 h instead of 4600 days for esterifications, these radical reactions would be a plausible origin for the atmospheric organosulfates. These reactions also produced efficient surfactants, possibly resembling the long-chain organosulfates found in the experiments. Thus, photochemistry in mixed sulfate/organic aerosols could increase cloud condensation nuclei (CCN) numbers, which would be supported by previous atmospheric observations

Place, publisher, year, edition, pages
2010. Vol. 37, no L05806
Keyword [en]
atmospheric aerosol, sulfate material
National Category
Natural Sciences
Identifiers
URN: urn:nbn:se:su:diva-44825DOI: 10.1029/2009GL041683OAI: oai:DiVA.org:su-44825DiVA: diva2:362601
Available from: 2010-11-09 Created: 2010-11-09 Last updated: 2017-12-12Bibliographically 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.
Keyword
biogenic, aerosol, CCN, water-soluble, microorganisms, surfactant, organosulfate
National Category
Natural Sciences
Research subject
Applied Environmental Science
Identifiers
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)
Opponent
Supervisors
Note
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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Noziere, BarbaraEkström, SannaAlsberg, TomasHolmström, Sara
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