Nitric oxide reactivity accounts for N-nitroso-ciprofloxacin formation under nitrate-reducing conditions Brienza, M. Manasfi, R. Sauvetre, A. /Chiron, Serge N-nitrosamine N-nitroso-ciprofloxacin Nitric oxide Activated sludge Biodegradation The formation of N-nitroso-ciprofloxacin (CIP) was investigated both in wastewater treatment plants including nitrification/denitrification stages and in sludge slurry experiments under denitrifying conditions. The analysis of biological wastewater treatment plant effluents by Kendrick mass defect analysis and liquid chromatography - high resolution - mass spectrometry (LC-HRMS) revealed the occurrence of N-nitroso-CIP and N-nitroso-hydrochlorothiazide at concentration levels of 34 +/- 3 ng/L and 71 +/- 6 ng/L, respectively. In laboratory experiments and dark conditions, produced N-nitroso-CIP concentrations reached a plateau during the course of biodegradation experiments. A mass balance was achieved after identification and quantification of several transformation products by LC-HRMS. N-nitroso-CIP accounted for 14.3% of the initial CIP concentration (20 mu g/L) and accumulated against time. The use of 4,5-diaminofluorescein diacetate and superoxide dismutase as scavengers for in situ production of nitric oxide and superoxide radical anion respectively, revealed that the mechanisms of formation of N-nitroso-CIP likely involved a nitrosation pathway through the formation of peroxynitrite and another one through codenitrification processes, even though the former one appeared to be prevalent. This work extended the possible sources of N-nitrosamines by including a formation pathway relying on nitric oxide reactivity with secondary amines under activated sludge treatment. 2020 text https://www.documentation.ird.fr/hor/fdi:010080399 fdi:010080399 Brienza M., Manasfi R., Sauvetre A., Chiron Serge. Nitric oxide reactivity accounts for N-nitroso-ciprofloxacin formation under nitrate-reducing conditions. 2020, 185, 116293 [8 ] EN FRANCE