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(W/EH019) Environmental fate of Diuron in railway ballast: biochemical,ecotoxicological and community structure studies. Giacomazzi, Sophie1, Gravelat, Fabrice1, Thybaud, Eric2, Truffaut, Nicole1, Pauss, André1, Cochet, Nelly1, 1 2 ABSTRACT- Diuron (N-(dichloro-3,4 phenyl-)-N,N-dimethylurea) has been used for many years as an agricultural herbicide. Since 1996, its use has been limited to a pre-emergence herbicide for the railroad rights of way. Diuron is a highly persistent and fairly immobile herbicide. As this compound has not yet been proved to be toxic, its biodegradation and photolysis lead to toxic derivatives, especially 3,4-dichloroaniline. a bacterial strain isolated from a privated garden soil was demonstrated to degradate 40 mg/l of Diuron in 36 hours when cultivated in a minimum medium supplemented with Diuron and 0,75 mg/l of succinate. We are currently studying the involvement of a cytochrome P450 in the metabolic pathway of the degradation. On the other hand, we investigated railway ballast samples treated with various amounts of Diuron. Since the chemical analysis was carried out in order to determine the fate of Diuron and its derivatives in the upper 60 cm of treated ballast, tools like DGGE, confocal laser microscopy and respirometry permit the characterisation of the microbial community structure. Ecotoxicological analyses were performed to complete the study. Key words: Diuron, Ecotoxicology, Community structure, Biodegradation |
