Trifluralin Degradation under Microbiologically Induced Nitrate and Fe(III) Reducing Conditions

• Published in: Environmental science & technology 2000-08, Vol.34 (15), p.3148-3152
• Main Authors: Tor, Jason M, Xu, Caifen, Stucki, Joseph M, Wander, Michelle M, Sims, Gerald K
• Format: Article
• Language: English
• Subjects: Agronomy. Soil science and plant productions; Applied sciences; Biodegradation of pollutants; Biological and medical sciences; Biological and physicochemical properties of pollutants. Interaction in the soil; Biotechnology; Earth sciences; Earth, ocean, space; Engineering and environment geology. Geothermics; Environment and pollution; Exact sciences and technology; Fermentation; Fundamental and applied biological sciences. Psychology; Herbicides; Industrial applications and implications. Economical aspects; Iron; Nitrates; Pollutants; Pollution; Pollution, environment geology; Soil and sediments pollution; Soil and water pollution; Soil science; Soils; USA, Midwest
• ISSN: 0013-936X; 1520-5851
• DOI: 10.1021/es9912473

Trifluralin [2,6-dinitro-N,N-dipropyl-4-(trifluoromethyl)benzenamine] ranks among the most commonly used herbicides in the United States. The compound persists under most environmental conditions, yet it is rapidly transformed under certain anaerobic conditions. In this study, the fate of trifluralin in anoxic environments and the contribution of Fe(II) to its anaerobic degradation have been investigated. Trifluralin was rapidly degraded under anaerobic conditions in a range of soils representing typical agricultural usage in the Midwest. The presence of nitrate or oxygen suppressed trifluralin degradation. Degradation rate increased under iron-reducing conditions, and the addition of trifluralin appeared to promote reoxidation of extractable Fe2+. Transformation of trifluralin under iron-reducing conditions apparently involved the soil solid phase and was not limited by bioavailability. In a soil-free aqueous system, no reaction of trifluralin with dissolved Fe2+ was detected in the presence or absence of kaolinite clay under anoxic conditions. Reduced but not oxidized or reoxidized forms of purified ferruginous smectite (sample Swa-1) catalyzed rapid transformation (72% of applied in 30 h) of trifluralin to polar products with a concomitant reoxidation of structural Fe in the clay. Results indicate that, as for other nitroaromatics, trifluralin is subject to reaction with Fe(II) associated with the minerals in anoxic environments.