The Morte-Femme peatland (Vosges Mountains, Northeastern France) is a protected area receiving treated wastewater from several textile industries. In spite of the treatment, these effluents still contain non-biodegradable micropollutants related to the textile process. Composed of highly substituted aromatic structures, optical brighteners (OBs) are water-soluble substances with a high affinity for cellulose fibers. OBs are used by the textile industry to mask the yellowing of cotton fabrics, as the blue light (400 – 440 nm range) they emit after UV excitation makes the fabrics appear whiter to the human eye. OBs can be quantified by HPLC-based techniques but this requires an expensive equipment. Furthermore, the exact nature of the OBs is generally unknown. Fluorescence-based methods are preferred for routine monitoring (Cao et al., 2009). For this purpose, yhe presence of OBs in the different watercourses running across the peatland has been assessed by differential synchronous fluorescence (i.e. before and after irradiation by UV (365 nm), with synchronous fluorescence spectra collected with a gap of 50 nm between excitation and emission) (Assaad et al., 2015). In order to discriminate OBs from the humic substances naturally present in the water samples, different irradiation durations have been tested. If a 15min irradiation is sufficient to detect OBs in solution in pure water, the presence of other elements (salts, dissolved organic matter, etc.) seems to hinder the irradiation effect. Therefore the effect of the irradiation duration has been tested on synthetic solutions of several OBs in presence of salts, organic matter and other potential textile additives. The final procedure has then been applied in the framework of the monitoring of the quality of the peatland surface water over two years. The results are discussed with respect to the streams natural discharge rate, which is highly dependent upon the season, and the textile industry activity.