除草定在土壤中的降解和移动特性研究

除草定是一种新型嘧啶类除草剂,其在环境中的归趋备受关注。采用室内模拟试验方法,研究了除草定在不同土壤中的降解性、吸附性和移动特性。结果表明,除草定在江西红壤、太湖水稻土和东北黑土中的降解半衰期分别为693.1、173.3、138.6 d,该药在土壤中降解较慢,影响其在土壤中降解速率的主要因素为土壤有机质。除草定在江西红壤、太湖水稻土与东北黑土中的吸附较好地符合Freundlich方程,Kd值分别为0.34、1.86和2.94;3种土壤对除草定的吸附过程为自发的物理吸附。薄层层析试验显示,当溶剂展开至11.5 cm处,除草定在江西红壤、太湖水稻土和东北黑土中最远移至8~10 cm处。影响除草定在土壤中吸附性和移动性的主要因素为土壤有机质含量。除草定存在对地下水污染的潜在风险性,使用除草定应该引起足够重视。

Degradation and Mobility of Bromacil in Soils

Bromacil is a kind of pyrimidine compounds, and the environmental behavior of bromacil has brought increasing concern. The degradation, adsorption and migration behavior of bromacil in different soils were system atically investigated by simulation test in laboratory. The results showed that the degradation half-lives of bromacil were 693.1, 173.3 and 138.6 d in Jiangxi red soil, Taihu paddy soil and the Northeast black soil in China, respectively, indicating that the soil degradation rate was relatively slow, and the major influncing factors of the soil degradation of bromacil was soil organic matter content. The adsorption of bromacil in the soils could be well fitted by the empirical Freundich isotherm. The adsorption constants (K_d) were 0.34, 1.86 and 2.94 in Jiangxi red soil, Taihu paddy soil, the Northeast black soil, respectively. The bromacil adsorption by soils belonged to spontaneous physical adsorption. TLC results showed that the movement distances of bromacil were 8-10 cm in Jiangxi red soil, Taihu paddy soil and the Northeast black soil when the solvent expanded to 11.5 cm. The result of the mobility test showed that bromacil is ready to move in the test soils. The soil organic matter content was the dominant factor affecting the adsorption and movement of bromacil in soils. It was demonstrated that there is potential risk of contaminating groundwater by bromacil. Therefore, enough attention should be paid to its application.