2,4-D的水解、光解及在土壤中的降解特性研究

Photolysis,Hydrolysis of 2,4-dicholrophenoxyacetic Acid and Its Degradation Characteristics in Soils

[目的]研究2,4-D在环境中的降解特性。[方法]采用室内模拟试验方法,测定2,4-D在水体中光解、水解及其在3种土壤中的降解特性,并对其降解特性进行评价。[结果]在常温(25℃)下,2,4-D在pH 5和9时的水解半衰期分别为117.5和79.7 d,较易水解;在pH 7时的水解半衰期为138.6 d,具有中等程度的水解特性。在人工光源氙灯条件下,其光解半衰期仅为4.63 h,较易光解。常温(25℃)下,2,4-D在江西红壤和东北黑土中的降解半衰期分别为86.6和53.3 d,易于土壤降解;而在太湖水稻土中的降解半衰期为20.2 d,易于土壤快速降解。[结论]2,4-D在环境中具有一定的稳定性,对水体和土壤环境存在一定的风险,应严格掌握其使用量和使用时期,加强对2,4-D在环境中的跟踪监测。

[Objective]The research aimed to study the degradation characteristics of 2,4-dicholrophenoxyacetic acid in the environment.[Method] The hydrolysis,aqueous photolysis and soil degradation characteristics were investigation under laboratory conditions.[Result]The hydrolysis half-lives of 2,4-dicholrophenoxyacetic acid were 117.5 and 79.7 d at pH 5 and 9 respectively,while its hydrolysis half-life at pH 7 was 138.6 d.This indicated that,it was easily hydrolyzed at pH 5 and 9,but hydrolysis at pH 7.0 was relatively slower.The half-life time of 4.63 hour was found with the radiation by Xe lamp at room temperature.Slow soil degradations in Jiangxi red soil,northeast black soil and Taihu paddy soil at 25 ℃ with the half-life time of 86.6,53.3,and 20.2 days were observed respectively.It was more easily degradated in Taihu paddy soil than the others.[Conclusion]2,4-dicholrophenoxyacetic acid was relatively stable in environment Therefore certain risks were existed in water and soil environment.The dosage as well as the time of application and monitoring of the residues should be well controlled in the agroenvironment.