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Environmental fate & pathways

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Biodegradation in water: screening tests

There are several higher tier biodegradation studies available assessing the biodegradation of the test substance in water and sediment, and in soil showing a moderately fast degradation/dissipation. However, in the light of the principle of precaution and the worst case the substance is thus regarded to be not readily biodegradable.

Biodegradation in water and sediment: simulation tests

The anaerobic aquatic metabolism of 14C-labelled test substance (diflufenzopyr) was studied in sediment and pond water. During the study the primary metabolite (difluoroaniline metabolite) reached a maximum concentration of 22% TAR (total applied radioactivity) by day 61 and decreased to 1% TAR by 187 DAT. The DT50 of the metabolite difluoroaniline was 27.4 days. The intermediate metabolite BH 654-5 ranged from 0.6% to 8% TAR and at 187 DAT accounted for less than 1% TAR. The present study showed that the test substance is rapidly degraded under anarobic conditions. The DT50 of the test substance was reported to be about 7.5 days. The half-lives in water and sediment were determined to be 5.75 d at 25 °C and 7.87 d at 25 °C, respectively.

Biodegradation in soil

The test substance (diflufenzopyr) degraded with a moderate rate under aerobic conditions with a half-life of about 18 days. The test substance degraded to a number of products. Metabolites M1 (8-Methyl-5-hydroxy-pyrido(2,3 d)-pyridazinone), M9 (8-Methylpyrido(2,3-d)pyridazine-2,5(1H,6H)-dione) and CO2 were the only degradation products found in excess of 10% TAR (total applied radiation) during the course of the study.