The sea surface microlayer is the organic-enriched layer present at the air-sea interface which has different physical and chemical properties compared to subsurface waters. The chemical analysis of this microlayer is of great interest for many reasons including its major influence to reduce air–sea gas exchange by impeding molecular diffusion across the interface and by influencing the characteristics of water motion at the interface. Surface seawater contains a variety of substances which act as photosensitizers. They include components of the dissolved organic matter known also as humic acids. The sea surface microlayer is the primary recipient of the solar energy. Since the microlayer is enriched in chemicals and biota, a number of processes are likely to be more effective here than in the rest of the water column. These include changes in the chemical composition of the living cells of phytoplankton and the photodegradation of or ganic matter. The focus of this study is to determine if the organic film acts as a hydrophobic barrier for the air-sea gas exchange and to identify and characterize the gaseous emissions and aerosol formation from the surface due to the photochemical processing of the sea surface microlayer. Synthetic mixtures (aqueous solution containing NaCl, NaBr, NaI), photosensitizers (humic acids) containing an organic surfactant (hexanol, octanol, nonanoic acid) have been irradiated by a Xe lamp, the gaseous products being further identified and analyzed by a High Resolution Proton Transfer Reaction – Time of Flight Mass Spectrometer. It has been observed that the presence of a thick organic film on the salt solutions reduces the transfer from the aqueous solution to the gas phase. It has also been observed the formation of certain aldehydes (heptanal, octanal, nonanal, nonenal), alkenes and –dienes (butene, 5-methyl-1, 4-hexadiene) in the gas phase. All these compounds were confirmed by GC/MS analysis. A formation of methylglyoxal and acetylacetone has also been detected. An isoprene formation was observed under irradiation. The isoprene is formed only in the presence of the organic surfactant with the need for the photosensitizer. The dependence of the isoprene concentration with the photosensitizer is shown. Furthermore, the oxidation products of isoprene and of the organic surfactant are identified. These results must be confirmed by GC/MS analysis. Experiments were also performed with benzophenone, imidazole and 2-imidazolecarboxyaldehyde as photosensitizers and the results will be discussed. Furthermore, experimental studies in a 2m3 multiphase atmospheric simulation chamber will be conducted in order to better describe the chemical processes at the air-sea interface. In this set-up, natural or artificial sea water containing a surfactant and a photosensitizer will be irradiated by UV/VIS lamps. TheVOCs formed will be analyzed by PTR-ToF MS and GC/MS, The photochemical processing of the microlayer will lead to the emission of a series of functionalized VOC which will be measured using a PTR-ToF MS and a GC/MS. Gas phase oxidation of these VOC will lead to the formation of SOA. The physical and chemical properties of the formed particles will be monitored and characterized by a SMPS and an Orbitrap LC/MS. The obtained results will permit to discuss about the importance of the photochemistry at the air-sea interface on the VOC and SOA loading in the marine boundary layer.