溶解性有机质对铁铝土吸附2,4-D的影响

以动力学吸附和等温吸附实验研究了2，4-D在铁铝土中的吸附特征，并比较了不同亲/疏水性溶解性有机质（DOM）对此的影响.结果表明：2，4-D在铁铝土中的动力学吸附符合伪一级动力学方程，等温吸附符合Henry，Freundlich方程，是一个物理作用主导的，自发的，放热的非均质吸附过程.吸附系数K_d为0.61~2.02L/kg，是一种难吸附有机污染物，对地下水存在环境风险.吸附量受土壤pH值影响显著，与土壤中矿物含量，粘粒组成等也密切相关.DOM共存条件下，高疏水性DOM，中疏水性DOM抑制了2，4-D在铁铝土的吸附，使K_d值下降10.7%~58.8%.低疏水性DOM对铁铝土吸附2，4-D作用不明显.DOM对铁铝土吸附2，4-D的作用效应与土壤理化性质和DOM性质密切相关.土壤矿物组分越多，粘粒含量越高，堵孔效应越大.DOM疏水性越大，对2，4-D吸附作用的增溶作用，堵孔作用也越大，其中HOA，HON是关键组分.

Influence of dissolved organic matter on sorption of 2, 4-dichlorophenoxyacetic acid in ferralsol

In this study,the sorption kinetics and isotherms of 2,4-dichlorophenoxyacetic acid (2,4-D) in three ferralsols were investigated,and the effect of dissolved organic matters (DOMs) was compared.The results showed that the sorption kinetics of 2,4-D in ferralsols followed Pseudo first-order equation,and the isotherm data were fitted well by Henry and Freundlich model,indicated that 2,4-D sorption on the ferralsols was an spontaneous,exothermic and anisotropic process dominated by physical forces.The value of K_d for 2,4-D ranged from 0.61 to 2.02 L/kg,implying that 2,4-D was difficult to be sorbed by the soils,which could result environmental risk to the groundwater.The sorption of 2,4-D in the ferralsol was significantly affected by the soil pH values,and was also closely related to the content of mineral and clay.Moreover,in the presence of dissolved organic matter,DOM with high hydrophobicity (CC) and DOM with medium hydrophobicity (SPd) inhibited 2,4-D sorption on the three ferralsols,causing the K_d values decreased by 10.7%~58.8%.Conversely,there was no significant effect by DOM with low hydrophobicity (RS).The influence of DOM on the sorption of 2,4-D in ferralsols were closely associated with both characteristics of DOM and soil.The effect of soil pore blocking increased with the increase of the soil mineral components and the clay contents.Meanwhile,with the increase of the hydrophobicity of DOM,the effect of solubility enhancement and pore blocking increased,which decreased the 2,4-D sorption in the ferralsols.The hydrophobiv acid fraction (HOA) and hydrophobic neutral fraction (HON) were the key fractions for this process.