除草剂绿草定-2-丁氧基乙酯的降解特性及降解机制研究

Degradation characteristics and mechanism of triclopyr-2-butoxyethyl ester in the environment

按照《化学农药环境安全评价试验准则》的规定并参考美国EPA导则,采用室内模拟试验方法,研究了绿草定-2-丁氧基乙酯在环境中的降解特性.结果表明,25℃时绿草定-2-丁氧基乙酯在pH=4、7、9缓冲溶液中的水解半衰期分别为533d、21.8d、<1d;高温、碱性条件下绿草定-2-丁氧基乙酯极易水解,其水解反应速率随反应介质pH值的增大、反应温度的升高而增大;初步确定绿草定-2-丁氧基乙酯分子在水溶液中生成的水解产物主要是绿草定.绿草定-2-丁氧基乙酯在土壤中迅速降解,酸性土壤中其降解趋势遵循一级动力学模型,中性和碱性土壤中其降解动态不能用一级动力学模型进行简单的拟合;绿草定-2-丁氧基乙酯在土壤中的降解形式主要为化学水解作用,降解生成绿草定和丁氧基乙醇;土壤pH和有机质含量是影响其土壤降解速率的主要因素,pH和有机质含量越高,其土壤降解速率越快.在人工光源氙灯条件下,绿草定-2-丁氧基乙酯在水溶液和土壤表面的光化学降解均符合一级动力学反应,不同介质对绿草定-2-丁氧基乙酯光解的影响差异显著.

Degradation characteristics of triclopyr-2-butoxyethyl ester in the environment were studied according to ＂ Experimental Guideline for Environmental Safety Evaluation of Chemical Pesticides＂ and regulations of the United States Environmental Protection Agency （EPA） through laboratory simulation. It was indicated that the half-lives of triclopyr-2-butoxyethyl ester in buffer solution of pH = 4, pH = 7, and pH = 9 at 25 ℃ were 533 d, 21.8 d and 〈 1 d, respectively. Trielopyr-2-butoxyethyl ester hydrolyzed very quickly on the condition of high temperature and in alkaline buffer solution, and its hydrolysis rate increased with increased temperature and pH. Meanwhile, it was found that the main hydrolytic product of trielopyr-2-butoxyethyl ester was triclopyr by HPLC identification. It was also indicated that triclopyr-2-butoxyethyl ester was degraded quickly in soils. First-order kinetics could describe its degradation behaviors in acid soils very well, but could not describe in neutral and alkaline soils. The principal degradation mechanism of triclopyr-2-butoxyethyl ester in soils was through hydrolysis, and triclopyr and 2-butoxyethanol were degradation products, pH and organic matter content of soil were the main factors controlling the degradation rates of triclopyr-2-butoxyethyl ester. Greater degradation rate was observed with higher pH value and higher organic matter content. The photolysis of triclopyr-2-butoxyethyl ester followed the first order kinetic both in water and on the surface of soil under Xe lamp ray, and it was indicated that medium had a significant effect on the photolytic rate of triclopyr-2-butoxyethyl ester.