有机质胶体对卡马西平在多孔介质中迁移影响模拟实验

有机质胶体与有机污染物的相互作用会影响污染物在多孔介质中迁移转化等环境行为.为研究有机质胶体对药物和个人护理品(PPCPs)在土壤环境中迁移的影响,本实验以卡马西平(CBZ)为目标污染物,用商用腐殖酸制备有机质胶体,分别选择石英砂、标准土和野外所取土样为研究介质,通过室内土柱模拟实验探究有机质胶体存在时污染物在多孔介质中的迁移行为.结果表明,描述一维溶质运移的两点化学非平衡模型能够较好模拟CBZ在各介质土中的运移过程,说明污染物运移过程中与介质间发生了化学非平衡吸附作用;石英砂柱中加入胶体后,对CBZ的吸附过程无明显影响,但在解吸时阻滞因子及滞留量变小,可见胶体与石英砂间作用微弱,解吸过程中胶体与污染物结合形成复合体后对污染物有增溶作用;胶体存在时,标准土和自然土对CBZ的吸附量和迁移阻滞强度均明显大于石英砂,其中有机质及黏土矿物的作用最为明显,有机质中的低能/高能吸附位点以及黏土矿物极性表面均能够固定污染物;由于有机质含量较高,自然土对CBZ在吸附-解吸过程中的阻滞截留强度大于标准土.针对本实验中CBZ的迁移情况,提出了疏水性有机污染物在含有机质胶体土壤中的迁移过程中各种作用的概念模型.

Simulation Experiment: Effect of Organic Colloid on Carbamazepine Transport in Porous Media

The behavior of organic contaminants in subsoil can be affected by their interactions with organic colloids. In order to explore the impact of organic colloids on the mobility of emerging contaminants in porous media, especially pharmaceutical and personal care products (PPCPs), column experiment was conducted to investigate the migration behavior of target compound carbamazepine (CBZ). In the experiments, quartz sand, standard soil and natural field-collected soil were selected as three types of porous media respectively, and organic colloids were prepared with commercial humic acid. The results showed that, the two-site chemical nonequilibrium model in CXTFIT could better describe the migration behavior of CBZ in all soil columns. This results demonstrated that chemical nonequilibrium adsorption happened in CBZ''s migration process. After colloid was added to the sand column, results of CBZ''s adsorption process had no significant changes, however, desorption hysteresis was weaker. The reason for that can be explained as the formation of colloid-CBZ complexes by the combination of colloid with CBZ. These complexes could not significantly influence CBZ''s adsorption process, however, they could accelerate CBZ''s desorption process by solubilization. When organic colloids existed, the migration of CBZ in natural soil and standard soil columns was more hysteretic than sand column, indicating that the sorption capacity of soil column was higher than sand column. The soil organic matter and clay should play a crucial role in the transportation: low/high energy adsorption sites in organic matter and clay surface all could bond with CBZ. Compared with standard soil, the magnitude of sorption and desorption hysteresis of CBZ in natural soil was higher. It was mainly because of the higher organic content in natural soil. Based on the migration behavior of the contaminant in this study, a concept model for various interactions during the transport of hydrophobic organic contaminants in porous media in the presence of organic colloids was then proposed.