重金属镉在土壤中迁移模拟研究

目的]以氯化镉（CdCl2）为供试污染物,通过人工模拟试验研究重金属重大污染事故发生时CdCl2污染物在土体中沿横向及纵向的迁移过程和特征,为重大环境污染事件的快速处理提供理论依据。方法]采用柱淋滤装置,模拟2阶段降雨条件下CdCl2在土壤层中的横向与纵向迁移分布特征,试验周期16d,采用便携式手控负压泵抽取土壤溶液样品,溶液中Cd含量采用原子吸收分光光度法测定。结果]在整个试验期间,重金属Cd呈现明显的横向和纵向分布特征,CdCl2在投加后0.5h即覆盖表层横断面,146h覆盖整个纵剖面。Cd浓度的纵向相对变化速率分析表明,不同深度Cd污染物快速通过的时间不同,15、35和55cm深度处Cd污染物快速通过的时间分别约为48、117和266h。结论]该箱体模拟装置可以同时考察污染物在土壤中沿横向和纵向的分布及迁移特征;较大降雨条件下重金属Cd污染物在土壤表面先以横向径流扩散为主,纵向迁移相对滞后。

Modeling Heavy Metal Movement in Soil

Objective] The migration process and feature of CdCl2 in the vertical and horizontal profiles of soil were studied by the stimulating experiment to present the theory for the treatment of significant pollution accident.Method]The column leaching device was taken to simulate the vertical and horizontal migration of CdCl2 in the soil profile under two-phase rainfall during 16 days.The portable manual control negative pressure pump was taken to extract soil solution sample and the Cd concentration was determined by the atomic absorption spectrophotometer.Result]During the whole experiment,the obvious horizontal and vertical migration features of CdCl2 appeared.The CdCl2 covered the whole horizontal profile in 0.5 h and the whole vertical profile in 146 hours.The relative variation rate of Cd in the different depth of bulk showed that the rapid passing time differed in the different depths.In the depth of 15,35 and 55 cm,the rapid passing time were about 48,117 and 266 h,respectively.Conclusion]The simulating device used in this paper could well investigate the vertical and horizontal distribution and migration of contaminant.Under the condition of greater rainfall,the CdCl2 gave priority to the horizontal runoff in the surface soil,followed by the vertical migration.