Thermohygroscopic properties of biogenic particles from the sea-surface microlayer

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This project is dedicated to field and laboratory investigations of the characteristics of biogenic aerosol particles derived from the sea-surface microlayer (SML). After two Arctic Ocean expeditions and additional recent findings from other parts of the world's oceans these SML-derived particles have come into the focus of marine aerosol research because of their likely widespread occurrence and because of the lack of understanding concerning their generation and physicochemical properties. Part of this lack of understanding is due to the unstable nature und the highly complex composition of SML-derived material. The upcoming Arctic Summer Cloud Study (ASCOS; http://www.misu.su.se/~michaelt- / ASCOS/ASCOS. htm) to be launched in the summer of 2008 provides a unique opportunity to use highly sensitive in situ aerosol instrumentation developed at IfT to characterize the thermohygroscopic particle properties as proxies for their physicochemical characteristics. At the same time new SML-samples will be collected during ASCOS, which, together with samples from AOE-2001 (the Arctic Ocean Experiment in summer of 2001) the North Atlantic, and the Baltic Sea, will be utilized in subsequent laboratory experiments at IfT. In these laboratory experiments aerosol particles will be generated from the SML-samples for detailed thermohygroscopic characterization up to 300°C and 101% relative humidity. Complementary chemical analyses will characterize the different SML-samples as far as state-of-the-art bulk methods allow. By exposing SML-derived particles to UV/VIS light in an aerosol chamber and by evaporating fog drops generated on SML-derived particles the stability of airborne SML-derived material will be explored. Finally a size-dependent particle model will be developed to describe the thermohygroscopic properties and stability of SML-derived particles that is consistent with both field data from AOE-2008 and with the subsequent laboratory results. The work will be realized within the scope of a Ph.D. thesis at Leipzig University.