有机质对p,p'-DDE在土壤中的吸附影响

Effects of Organic Matter on the Adsorption of p,p'-DDE in Soil

为研究有机质对p,p'-DDE在土壤中的吸附影响因素,采用批量试验方法,分析p,p'-DDE在包气带土壤及含水层土壤上吸附量的变化及有机质对p,p'-DDE在土壤中的吸附影响.结果表明,p,p'-DDE在土壤中的吸附均符合先快后慢、最后达到吸附平衡的规律;其吸附动力学曲线用一级和二级反应动力学方程均能较好拟合,说明p,p'-DDE在这两种物质中的吸附以简单吸附为主,同时包含表面吸附、颗粒内部扩散等过程.包气带土壤和含水层土壤等温吸附线的拟合相关系数(R2)均大于0.95,符合Freundlich模型和线性模型,而含水层样品与Freundlich模型拟合得更好,表明p,p'-DDE在包气带土壤中的吸附以单分子层吸附为主,而在含水层土壤中的吸附还伴随着多分子层吸附的复杂过程;去除内源DOM(溶解性有机质)后,样品对p,p'-DDE的吸附量呈增加趋势,按吸附增加量由小到大的排序为1-1(0~10 cm)<1-2(120~150 cm)<2-4(100~120 cm),说明内源DOM的存在总体上抑制了p,p'-DDE的吸附,并且w(DOM)越高,其抑制作用越强;外源DOM的加入抑制了土壤对p,p'-DDE的吸附;去除有机质后样品对p,p'-DDE的吸附量与w(黏土矿物)具有正相关性.研究显示,有机质对土壤中有机污染物的吸附迁移研究对土壤修复有重要意义,需要对有机质影响土壤的吸附机制进行更深层次的研究.

Batch equilibrium experiments were used to investigate the effects of organic matter on the adsorption of p, p; -DDE in soil. The results showed that the adsorption rate of p,p;-DDE in soil and shallow aquifer soil was fast initially and then slowed down before reaching the adsorption equilibrium. The adsorption kinetics curves of the soil and shallow aquifer soil could be fitted by the first-order and second- order reaction kinetic equations, which means that the adsorption of p,p;-DDE in soil and aquifer samples was mainly simple adsorption, but still included surface adsorption and particle internal diffusion. Moreover, the sorption isotherm correlation coefficients （ R2 ） of p,p;-DDE on the soil and shallow aquifer soil were greater than 0. 95, fitting both Freundlich and linear equations, but the Freundlich equation was better for the aquifer samples. The adsorption of p , p ’-DDE in soil was mainly monolayer adsorption, while it was more complex in sediments with multi-molecular layer adsorption. After removing endogenous dissolved organic matter （DOM） , the adsorption of p , p’-DDE in samples increased,and the order of samples from low to high was 1-1 （0-10 cm） 〈 1-2 （ 120-150 cm） 〈 2-4 （100-120 cm） . This showed that the adsorption of p, p f - DDE in soil and sediment might be prohibited by the endogenous DOM, and the inhibiting effect was stronger with the higher content of DOM. The exogenous DOM had an inhibiting effect on the adsorption of p,p;-DDE in soil samples. The adsorption capacity of p , p＇-DDE in samples had a positive correlation with the clay mineral content after removing organic matter.