IHSS&IWA26 / BRNO / CZECHIA / 23–28 August 2026 BOOK OF ABSTRACTS 44 Analysis and Characterization Monday, 24 August 2026 / Hall B+C SL16 High‑Frequency Monitoring of Dissolved Organic Matter in the Seine River (France) Using the Fluocopée® In Situ Fluorescence Probe Antoine Raoult1, Angélique Goffin1, Jérémy Mougin2, Rania Krimou2, Vivien Raymond4, Sabrina Guerin-Rechdaoui2, Vincent Rocher2, Sylvie Thibert3, Gilles Varrault1 1 LEESU, Univ Paris Est Creteil, ENPC, Institut Polytechnique de Paris, Créteil, France, +33682422804, antoine.raoult@u-pec.fr 2 Greater Paris Sanitation Authority (SIAAP), Innovation Department, 82 Av. Kléber, 92700 Colombes, France 3 Syndicat des Eaux d’Île de France (SEDIF), 14 rue Saint-Benoît, 75006 Paris, France 4 Veolia Franciliane, 28 Boulevard de Pesaro, 92000 Nanterre, France Over the past two decades, there has been a notable advancement in the development of high-frequency measurement equipment for the monitoring of biophysical and chemical parameters in surface water. Optical probes, especially fluorescence probes, are of particular importance in the integration of high-frequency measurements into environmental monitoring (1,2). The Fluocopée® probe, developed through a collaboration between LEESU and SIAAP (patented), is one example of such new in situ measurement instruments. It offers a relatively fine characterization of Dissolved Organic Matter (DOM) by monitoring 29 / pairs. It is sensitive enough to be used in continuous river monitoring (3). Since October 2023, up to five Fluocopée® probes have been deployed on the Seine River and its main tributaries (Marne and Oise) to form the MeSeineMatOS in situ observatory. This observatory enables the assessment of spatial variability of DOM in the Seine River across the Paris conurbation at high temporal frequency and elucidates biogeochemical dynamics under urban pressures. This conference will present key conclusions from fluorescence time series acquired to date within the MeSeine-MatOS observatory. In 2024, the Seine River basin experienced unusual hydrological conditions. It saw a succession of relatively intense flood episodes throughout the winter period, followed by unusually high flows during the summer. Under these conditions, high-frequency fluorescence data revealed chemically diverse DOM fractions in the Seine River, likely originating from distinct sources. Some of the / pairs monitored by the Fluocopée® probe have thus revealed the dynamics of natural DOM inputs transported by the Seine during flood events. By applying a predictive model providing high-frequency estimates of
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