毒草胺在环境中的降解特性研究

Photolysis, hydrolysis of propachlor and its degradation in soils

毒草胺是一种被广泛应用的农药,其在环境中的降解特性备受关注。文章采用室内模拟试验方法,研究了毒草胺的光解、水解及土壤降解特性。研究结果表明,毒草胺在光强为2 370l x、紫外强度为13.5μW.cm-2的人工光源氙灯条件下,光解半衰期为2.5 h,较易光解。25℃时在pH值为5.0、7.0和9.0的缓冲水溶液中,降解半衰期分别为147.5、173.3和239.0 d;50℃时半衰期分别为15.2、27.0和42.3 d,结果显示温度对其降解速率影响较大,温度增加,水解速率明显加快,水解半衰期降低约6~10倍。该药在江西红壤中降解半衰期为46.5 d,在太湖水稻土、东北黑土中降解半衰期分别为6.4和7.9 d,比较容易降解,主要为微生物降解。结果表明毒草胺在水体中具有一定的稳定性,尤其在避光条件下难以降解。但在土壤中,比较容易被微生物降解。

Propachlor is a widely used herbicide and its environmental behavior of Propachlor has called increased concern.Hydrolysis,photolysis,and biodegradation are 3 important transformation pathways of herbicide in environment.In this study,the photolysis,hydrolysis,and biodegradation of Propachlor are systematically investigated.Laboratory batch experiment demonstrated that Propachlor could be rapidly degraded under UV radiation.The half-life time was 2.5 h at the energy density of 13.5 μW.cm-2 using Xe lamp.In contrast,the hydrolysis of Propachlor was rather slow.Half-life time was 147.5,173.3,239.0 d at pH 5.0,7.0,and 9.0,respectively,at 25 ℃.Temperature was the key factor affecting the kinetics of hydrolysis.The half-life time increased to 15.2 d、 27.0,and 42.3 d at 50 ℃.The major approach of the degradation of Propachlor in soils was biodegradation,and the half-times of Propachlor degradation were 46.5,11.0 and 6.0 d in Jiangxi Red soil,Northeast black soil and Taihu Paddy soil,which was affected by the content of soil organic matters.