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Photochemistry of organic aerosols

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Indirect photochemical processes require sensitizers (often chromophores) which once in the triplet state can react with oxygen to form singlet oxygen. This research project aims to characterise sensitizing molecules present in secondary organic aerosol and proposed to undergo photochemistry. Molecular candidates are being tested including lignin derived molecules. Probe molecules of interest include quinones as they are known to take part in electron transfer reactions. In particular, we investigate the kinetics of oxidation of juglone (C10H6O3) in the aqueous phase, a molecule likely to be an oxidative product in organic aerosols. We then search for molecules present in ambient organic aerosols with unique functional groups, capable of sensitizing singlet oxygen.

Project leader: Master thesis student Sebastian Zala

Our group recently demonstrated that a photomineralization mechanism can increase the cloud droplet formation and decrease the ice nucleating ability of dissolved organic matter (DOM). We were using DOM samples collected from rivers and swamps with known chromophoric abilities. Now we are extending our study of the photomineralization mechanism to field-collected organic aerosols.

Project leader: Master intern Silvan Müller

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