Shining light on the air-sea interface: investigating the photochemical production of functionalized VOC
Résumé
This study presents the results of a set of laboratory experiments aiming at a better understanding of the role of the sea surface microlayer in the photochemical production of VOCs. Recently, we have shown that light driven reactions, in aqueous solutions containing a photosensitizer (P) in the presence of a surface organic microlayer, leads to the formation of various gaseous VOCs.. The main VOCs produced, analysed by PTR/SRI-ToF-MS, were oxidized species, such as aldehydes, ketones and alcohols, as expected by the photo-oxidation of the organics at the air/water interface. However also alkenes, dienes and unsaturated aldehydes were detected and a reaction pathway, initiated by an H-abstraction of the surfactant by the excited P*, has been proposed. This mechanism infers that the presence of the surface microlayer will enhance protonation and self-reactions, leading to the formation of dimers, as confirmed by UPLC-HR-ESI-MS analysis. As most of these compounds were thought to be solely produced by biological activities, the existence of such interfacial photochemistry opensnew directions that will discussed.