Hydrolysis and photolysis of flumioxazin in aqueous buffer solutions

Abstract

To determine the degradation rates and degradation products of the herbicide flumioxazin in aqueous buffer solutions (pH 5, 7 and 9), its hydrolysis and photolysis were investigated at 30 degrees C in the dark, and in a growth chamber fitted with fluorescent lamps simulating the UV output of sunlight. The rate of hydrolysis of flumioxazin was accelerated by increasing pH. The t(1/2) values at pH 5, 7 and 9 were 16.4, 9.1 and 0.25 h, respectively. Two degradation products were detected and their structural assignments were made on the basis of LC-MS data. Degradation product I was detected in all buffer solutions while degradation product II was detected in acidic buffer only. Both degradation products appeared to be stable to further hydrolysis. After correcting for the effects of hydrolysis, the photolytic degradation rate also increased as a function of pH and was approximately 10 times higher at pH 7 than that at pH 5, showing t(1/2) values of 4.9 and 41.5 h, respectively. Degradation products formed by photolysis were the same as those formed by hydrolysis. Flumioxazin was degraded more extensively at high pH and should degrade in surface water.

Dissipation and movement of flumioxazin in soil at four field sites in Chile

“…Therefore, an increase in rain events and a reduction in the time between herbicide application and first heavy rain event should result in an increase of flumioxazin in solution in soil water, reducing the DT 50 values. There was an inverse relationship between pH and flumioxazin DT 50 ( r = − 0.69; P < 0.0001), possibly owing to rapid hydrolysis which increases from pH 5 to pH 7 6. If it rains during the first 30 DAA and soil pH is greater than 6, flumioxazin can rapidly dissipate in the soil because of microbiological and chemical degradation.…”

“…Flumioxazin [ N ‐(7‐fluoro‐3,4‐dihydro‐3‐oxo‐4‐prop‐2‐ynyl‐2 H ‐1,4‐benzoxazin‐6‐yl)cyclohex‐1‐ene‐1,2‐dicarboxamide] is a soil‐applied herbicide recommended for broadleaf weed control in soybeans and peanuts and recently introduced for vineyard weed management 1–2. Although this herbicide was introduced in 1989 in the USA, few references exist related to its environmental behaviour 3–8…”

The potential algaecide flumioxazin has little effect on growth, survival and feed conversion of the bluegill sunfish Lepomis macrochirus

“…Flumioxazin degradation is subject to pH-dependent hydrolysis with half-lives of~24 h noted at pH 7 and 22 min noted at pH 9 (Kwon et al, 2004). Findings by Mudge and Haller (2010) indicate that a single application may not provide adequate control of the invasive aquatic plant Hydrilla verticillata when applied to waters with high pH values.…”

Degradation of furan tebufenozide in laboratory and field trials

“…Environmental elements such as pH values, temperatures, microbes and lights were often the main factors deciding the degradation performance of the herbicides in the field [14,15]. We investigated the factors under controlled conditions in the laboratory to simulate field degradation and the more complex degradation behaviors were studied under open field conditions.…”