酰胺类农药在白洋淀典型农田土壤上的吸附行为

Adsorption of acetanilide pesticides on soils of Baiyang Lake

采用振荡平衡法研究了5种常见的酰胺类农药(除草剂甲草胺、乙草胺、异丙甲草胺、丁草胺和杀菌剂甲霜灵)在白洋淀地区4种典型农田土壤中的吸附特性.酰胺类农药的吸附遵循Freundlich吸附等温式,吸附程度按丁草胺>甲草胺>乙草胺>异丙甲草胺>甲霜灵的次序减小.有机质含量最高的淀区泥李庄农田土壤对农药的吸附能力最强.酰胺类农药的有机碳吸附常数(logKoc)与辛醇-水分配系数(logKow)显著相关,表明分配作用在农药的吸附中起着重要的作用.吸附自由能的变化为-8.24^-20.40kJ·mol-1,表明这5种酰胺类农药在白洋淀农田土上的吸附机理主要是物理吸附.

Batch equilibrium experiments were used to investigate the adsorption of five acetanilide pesticides, alachlor, acetochlor, metolachlor, butachlor and metalaxyl, in typical soils collected from the farmland of Baiyang Lake Wetland. Adsorption of these pesticides followed Freundlich equation with r2 more than 0.966, and decreased in an order of butachlor 〉 alachlor 〉 acetochlor 〉 metochlor 〉 metalaxyl. Among 4 soils, the soil from Nili Village had the highest absorption capacity because of the highest organic matter content. There was a good linear correlation between logKoe and logKow of acetanilide pesticides, which revealed that their adsorption was driven predominately by partition. Moreover, the adsorption free energy of the five acetanilide pesticides ranged from -8.24 to -20.40 kJ ·mol-l, indicating that their adsorption could be largely attributed to physical adsorption, 1fig., 5tabs.. 12refs.