The Degradation And Residue Of Pyrazosul Furon In Paddy Field And Its Hydrolysis

Pyrazosulfuron as a highly active and low toxicity herbicide has been widely accepted, and thus it has been practically applied on agricultural production. We researched on its residual dynamics in the paddy field environment after using the20%of pyrazosulfuron water dispersible granule in rice crop, and the degradation of pyrazosulfuron affected by different environmental factors. These studies can be applied on precisely evaluating the safety of ecological environment after adding ethyl pyridine on rice, as well as providing some important basic evidence for its application. The main conclusions are as follows:(1) A liquid chromatography method to analyze the residue of pyrazosulfuron in rice sample was established. By using this analysis method, the minimum detectable amount of pyrazosulfuron was4.0×10-9g; the minimum detectable concentration in plants and chaff, soil and unpolished rice, and water were0.01mg/kg,0.05mg/kg,0.01mg/kg, respectively. When the concentration was within the range from0.01to l.OOmg/kg, the average recovery rate of pyrazosulfuron ranged from83.68%to l0l.9%with the relative standard deviation ranged from0.6%to6.2%, which met the pesticide residue analysis requirements.(2) The experiments were conducted in Hunan, Guizhou and Beijing, the digestion half-life of pyrazosulfuron in soil, water and plants were3.60d,2.63d,2.72d, respectively. Obeyed the first-order chemical reaction dynamics equation(e=Co-kt), the results indicated that pyrazosulfuron is easy degradation herbicide in rice.(3) Based on experiments on Hunan, Guizhou, and Beijing, uring the period of rice crop planting Pyrazosulfuron spraying the recommendation dose of Pyrazosulfuron on rice, rice straw, brown rice and rice husk, the results showed Pyrazosulfuron cannot be detected. In soil the residue of Pyrazosulfuron was LOD～0.017mg/kg, which not exceeds the MRL value (0.lmg/kg). Therefore, the results showed that20%of pyrazosulfuron water dispersible granules is safe to be used in rice.(4) The experiment of the hydrolysis of pyrazosulfuron affected by different pH values, different temperature, five kinds of inorganic salt and three fertilizers have been investigated. The results indicated that the hydrolysis of pyrazosulfuron was promoted in acid. Its hydrolysis was restrained in alkaline. With the rise of temperature, the hydrolysis rate of pyrazosulfuron was increased. By the condition of five kinds of inorganic salts, the hydrolysis rate of pyrazosulfuron:strong acid and weak base salt (MgCl2、CaCl2)>Strong acid and weak base salt(NaCl)> strong base and weak acid salt,(NaHCCO3、NaH2PO4) the corresponding changed with the increase of concentration. The hydrolysis rate was affected by three kinds of fertilizers:calcium superphosphate>potassium chloride>urea.