Fate of chlorsulfuron in the environment. 1. Laboratory evaluations

✍ Scribed by Strek, Harry J.

• Publisher: John Wiley and Sons
• Year: 1998
• Tongue: English
• Weight: 420 KB
• Volume: 53
• Category: Article
• ISSN: 1526-498X
• DOI: 10.1002/(sici)1096-9063(199805)53:1<29::aid-ps749>3.0.co;2-a

✦ Synopsis

The behaviour and fate of chlorsulfuron in aqueous and soil systems were examined in laboratory studies. Aqueous hydrolysis was pH-dependent and followed pseudo-Ðrst-order degradation kinetics at 25¡C, with faster hydrolysis occurring at pH 5 (half-life 24 days) than at either pH 7 or 9 (half-lives [365 days). Degradation occurred primarily by cleavage of the sulfonylurea bridge to form the major metabolites chlorobenzenesulfonamide (2-chlorobenzenesulfonamide) and triazine amine (4-methoxy-6-methyl-1,3,5-triazin-2-amine). This route is a major degradation pathway in water and soil systems. Aqueous photolysis (corrected for hydrolysis) proceeded much more slowly (half-life 198 days) than aqueous hydrolysis and is not expected to contribute signiÐcantly to overall degradation. Hydrolysis in soil thin-layer plates exposed to light (half-life 80 days), however, progressed at a much faster rate than in dark controls (half life 130 days), which suggests that a mechanism other than direct photolysis may have been operative. An aerobic soil metabolism study (25¡C) in a Keyport silt loam soil (pH 6É4, 2É8% OM) showed that degradation was rapid (half-life 20 days). Dissipation in an anaerobic sediment/water system (initial pH of water phase 6É7, Ðnal pH 7É4) progressed much more slowly (half-life [365 days) than in aerobic soil systems. Major degradation products in aerobic soil included the chlorobenzenesulfonamide and triazine amine as in the aqueous hydrolysis study. Neither of these degradation products