|Lerch, Robert - Bob|
Submitted to: ASA-CSSA-SSSA Annual Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 7/3/2003
Publication Date: 11/3/2003
Citation: LIN, C., LERCH, R.N., GARRETT, H.E., GEORGE, M.F. 2003. DEGRADATION OF ISOXAFLUTOLE (BALANCE) HERBICIDE BY HYPOCHLORITE IN TAP WATER [abstract] [CD-ROM]. ASA-CSSA-SSSA ANNUAL MEETING ABSTRACTS. Interpretive Summary:
Technical Abstract: Chlorine has been widely employed for the disinfection of drinking water. Additionally, it has the capacity to oxidize organic compounds, including pesticides, in water. Isoxaflutole (Balance; IXF) belongs to a new class of isoxazole herbicides. Isoxaflutole has a very short soil half-life and rapidly degrades to a stable and phytotoxic metabolite, diketonitrile (DKN). Further degradation of DKN produces a nonbiologically active benzoic acid (BA) metabolite. In experiments using high performance liquid chromatography-UV spectroscopy (HPLC-UV) and HPLC tandem mass spectrometry (HPLC-MS/MS), DKN was found to rapidly react with hypochlorite in tap water, yielding the benzoic acid metabolite as the major end product. One mg/L of hypochlorite (OCl**-) in tap water was able to completely oxidize up to 1600 ug/L (4.45 umole/L) of DKN. In tap water, the disappearance of IXF was much more rapid than in DI water. As soon as the IXF was hydrolyzed to DKN, the DKN quickly reacted with OCl**- to form BA. As a result, herbicide solutions prepared with tap water at 500 ug/L did not possess any herbicidal activity after 48 hours. However, in agronomic settings, highly concentrated tank solutions (600-800 mg/L) may be prepared with tap water since the conversion of IXF to BA would represent <5% of the herbicide at these concentrations, and therefore, any impact on the herbicide efficacy would be negligible. Results of this study show that chlorine disinfection completely eliminates the phytotoxic DKN metabolite from drinking water supplies, yet farmers can use chlorinated tap water without significant loss of efficacy.