Degradation Kinetics And Metabolism Of New Sulfonylurea Herbicide Methiopyrsulfuron In Aqueous Environment

Methiopyrsulfuron [methyl 2-(4-methoxyl-6-methylthio-2-pyrimidinyl) aminocarbonyl sulfonyl benzoate, MPS], test code: HNPC-C9908, was a novel sulfonylurea herbicide discoveried and developed by Hunan Resear Institute of Chemical Industry, and can control effectively broadleave weeds and some grassed in the wheat field at the application rate of 15~30g/hm~2 without phytotoxicity to crops. Because of its novelty, few information are available about residue analysis and behaviors of MPS in the aqueous environments.Therefore, it is very important to investigate the hydrolysis of MPS residue in aqueous system in order to assess the MPS environmental safety and work out ther reasonable application guidelines. Degradation of MPS in organic solvents and water systems has been studied in detail since 2006. Based upon the research contents, the thesis was divided into the following five parts.First of all, the current status and development on residue analysis and behaviors of the sulfonylurea herbicide in the environments were reviewed, and a brief background of MPS discovery and developemnt was introduced.Secondly, detection and analysis of MPS residues in aqueous environments was studied. The results indicate that the method is fast, sensitive, reproducible and practical for the residue detection and analysis of MPS in aquatic and soil systems.Thirdly, the degradation of MPS in the organic solvents was investgated. Results showed that degradation of MPS in five organic solvents such as methanol, ethanol, acetone, and acetonitrile and hexane, followed the first order kinetics equation. And the half-lives in methanol, ethanol, acetone, and acetonitrile and hexane were 9.85day, 11.09day, 36.87day, 79.67day and 693day, respectively. The alcoholysis degradation products of methiopyrsulfuron were confirmed by LC/MS, while the pathway of the degradation was explored. The main degradation products are 2-benzoic acid carbomethoxy sulfonyl carbamate, 4-methoxy-6-(methylthio) pyrimidin-2-amine and 4-methoxy-6-(methylsulfinyl) pyrimidin-2-amine. Meanwhile, factors which influence alcoholysis, such as temperature, concentration, pH value and water content of methanol solvent were studied.Fourthly, hydrolysis of MPS in buffer solutions was studied. Results showed that degradation of MPS in different pH value buffer solution followed the first order kinetics equation. And the half-lives in pH1-10 were 20.03 day, 25.48 day. 33.36 day, 36.10 day,55.45 day,64.78 day, 216.61 day,169.06 day, 4.26 day and1.17 day, respectively. The hydrolysis degradation products of methiopyrsulfuron were confirmed by LC/MS, while the pathway of the degradation was explored. The main degradation products are 2-benzoic acid carbomethoxy sulfonyl carbamate, 4-methoxy-6- (methylthio) pyrimidin -2-amine, 4-methoxy-6-(methylsulfinyl) pyrimidin-2-amine, methyl- 2-sulfamoyl benzoate and 2-sulfinic acid methyl. Meanwhile, factors which influence hydrolysis, such as pH value, temperature, micro-organisms, and surfactant were studied. Finnally, a summary was given. Meanwhile, some suggestions were put forward.