This project aims to characterize the photochemical fate of marine organic micropollutants in a specific and ubiquitous media, the Sea Surface MicroLayer (SSML). The SSML, that includes the air-water interface as well as the few hundreds of micrometers below, is a very particular photoreactor due to both significant enrichment in organic material, mainly biogenic one, and constant interactions with the atmosphere. The SSML is also known to accumulate numerous organic contaminants but is for now surprisingly almost ignored when talking about reactive fate of contaminants in marine surface waters. The first aspect of this project will be to study the effects of the organic material accumulation in the SSML on the photo-induced degradation of organic pollutants. We will develop an original experimental approach in order to kinetically and mechanistically evaluate the impacts of each main class of SSML components. The objective is to test the following hypotheses: the SSML is a sufficiently different media than the underlying water to modify reaction kinetics and thus lifetime of pollutants therein; the concentration of organic material can lead to SSML specific chemical routes and to the formation of degradation products unexpected in the underlying water. The investigation of multiphase and heterogeneous physico-chemical processes constitutes the second aspect of this project. The first objective will be to characterize the parameters leading to the enrichment of organic micropollutants in the SSML, in order to provide the classes of organic pollutants that can be significantly impacted by SSML specific processes. This SSML enrichment in pollutants will be tentatively linked with pollutant volatilization, via the relative quantification of this transfer as a function of SSML composition. In addition, the heterogeneous reactions of organic pollutants with some major atmospheric photooxidants will be investigated. We will provide kinetic and mechanistic data, with a focus on specific degradation products. The objective is to answer the question of the significance (quantitative and qualitative) of these heterogeneous reactions as a loss process of organic pollutants in marine surface waters. The third part of this project will aim to confirm laboratory-based conclusions through the case-study of the SSML in the marine coastal area of Marseille (Mediterranean Sea, France). In particular, SSML enrichment factors will be determined and SSML-specific transformation products will be extensively searched for.