| ZJ0273, propyl 4-(2-(4,6-dimethoxypyrimidin-2-yloxy)benzylamino)benzoate, is a new broad-spectrum herbicide. It is marketed under the trade names of Youli (EC) and Youliâ…¡(SC) in China, and both products were temporary registered for use in oilseed rape in 2003. Applications of the herbicide at the dosage of 40-60 g ai/ha are commonly used to achieve effective control of 80-90% in rape fields against pre-emergence weeds. In order to achieve cosmically commercial application, the degradation products and pathway of ZJ0273 needed to be further studied.The dissipation and degradation pathway of ZJ0273 in aerobic soils was investigated under laboratory condition by isotope tracer techniques and modern instrument analysis. The purpose of this study is to elucidate the degradation pathway of ZJ0273 in aerobic soils. All the results will help for application of industrialization of ZJ0273, and structure optimization of its lead compound, environment-friendly developing invention of novel varieties.The main results were as follows:(1) Under aerobic condition, rapid degradation of ZJ0273 in 3 different soils were in accord with first order kinetics equation C=C0exp(-kt) with half-life ranging from 17.37d to 52.10d. The half-life of ZJ0273 was inversely correlated with the soil pH and CEC. There is no significant difference between degradation of [B ring-4,6-14C] ZJ0273 parent and [C ring-U-14C] ZJ0273. The degradation rate in 3 soils followed the order of alkaline soil (S3) > neutral soil (S2)> acidic soil (S1).(2)The identification of degradation products from ZJ0273 in aerobic soils was performed by LSC and HPLC-MS/MS. Compared with the results of HPLC and mass spectrum of standard compound (â…¡,â…¢,â…£) and degradation product (â…¡,â…¢,â…£), three major degradation products of ZJ0273 in aerobic soils were verified as 2-(4,6-dimethoxypyrimidin-2-yloxy) benzoic acid (degradation productâ…¡), 4-(2-(4,6-dimethoxypyrimidin-2-yloxy) benzylamino) benzoic acid (degradation productâ…¢), 4-(2-(4,6-dimethoxypyrimidin-2-yloxy) benzamido) benzoic acid (â…£). The proposed degradation pathway of ZJ0273 in aerobic soil was as follows: (3) The dissipation of ZJ0273 and dynamics of degradation products in aerobic soils were also investigated by LSC techniques and HPLC analysis, and four degradation products were found based on radioactive detection:â‘ Degradation productâ… was only related to B ring, and it dissipated more rapidly in soil with high pH value;â‘¡Degradation productâ…¡was the main product of ZJ0273 in aerobic soils. The dynamic of degradation productâ…¡was different in three soils: in S1, the percent of applied amount was increasing with time in the whole incubation; in S2 and S3, the maximum percent of applied amount appeared in 45d, but in 100d, no significant difference in productâ…¡was found between the three soils;â‘¢Degradation productâ…¢was increasing with time in S1, and degradation productâ…¢reached maximum at 20d in S2 and S3. The productâ…¢reached the maximum earlier than productâ…¡.â‘£Productâ…£was keeping the low level in S1, and no apparent difference was observed during the whole incubation time. In S2 and S3, during the initial 20d, compoundâ…£was the main product, which decreased quickly with increasing of productâ…¡, suggesting that compoundâ…¡might be one of the secondary products of productâ…¢and productâ…£.
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