三种丙烯菊酯系列产品的光解和水解稳定性

Stability of three allethrin-series products in photolysis and hydrolysis

研究了富右旋反式丙烯菊酯、Es-生物丙烯菊酯、右旋丙烯菊酯 3种丙烯菊酯系列农药在水体中的光解以及不同温度、pH条件水体中的水解作用。结果表明 ,在 5 0 0W氙灯下 ,3种菊酯类农药在水溶液中的光解均呈一级动力学反应 ,3种农药的光解半衰期分别为 1.84 ,1.37和 1.5 1h ;在 2 5℃的酸性水溶液中 ,3种农药的水解速率很慢 ,半衰期均大于 16 2d ;水温的升高与碱性的增强均能加速水解过程。在 5 0℃的碱性水溶液中 ,3种农药的光解半衰期分别为 0 .2 1,0 .2 2和 0 .18d。虽然 3种丙烯菊酯异构体含量不同 ,但其光解、水解特性没有显著差别。本文对有关水解机理也作了初步分析。

The photolysis of rich d -trans- allethrin , Es-biothrin , d -allethrin and hydrolysis of the three pyrethroids in water varying in temperature and pH were studied in the laboratory. Results of the test show that the photolysis of all the three pyrethroids in aqueous solutions under a 500 W xenon lamp fitted to the first order reaction dynamic equation, and the photolytic half-life values of rich d -trans- allethrin , Es-biothrin , d -allethrin in water were 1.84,1.37 and 1.51 h, respectively. The results also show that the hydrolytic rates of the three pyrethroids in the buffer solutions with pH being 5 and temperature at 25 ℃ were very low, with half-life longer than 162 d. With the temperature and the pH value rising, the hydrolytic rate was accelerated. The hydrolytic half-life values of rich d -trans- allethrin, Es-biothrin and d -allethrin in the buffer solutions with pH being 9 and temperature at 50 ℃ were 0.21,0.22 and 0.18 d, respectively. The experiment also shows that the three pyrethroids differed slightly in photolytic and hydrolytic rates in spite of their difference in isomer content.The mechanism of the hydrolysis was also discussed.