二维砂箱模型中DNAPL运移过程的电阻率成像法研究

Investigation of DNAPL migration process in two dimensional sand trough model using electrical resistivity tomography

本研究通过设有黏性土透镜体的二维砂槽中开展重非水相液体(DNAPL)入渗运移试验,采用电阻率成像法(ERT)探讨DNAPL在非均质多孔介质中的运移分布规律.试验过程中利用电阻率成像系统进行动态监测,采集电压电流数据后得到相应的电阻值并将其转换为视电阻率值,运用Surfer软件处理数据进而获取DNAPL运移过程的相对电阻率变化分布图像.结果表明,相对电阻率值随着污染物浓度的增加而不断增大,不同时刻相对电阻率变化分布图像与DNAPL的运移过程相对应,可以清晰圈定出DNAPL的运移路径及分布范围;DNAPL在入渗过程中受到重力作用与毛细力的控制,以垂向运移为主,在遇到黏土透镜体时出现明显横向运移,绕过透镜体继续向下入渗最后聚积在砂槽底部.本研究为进一步丰富对DNAPL污染物在实际环境条件下运移机理和分布特征的认识,制定可行的DNAPL污染物治理方案等方面具有重要的科学价值.

In this research,Electrical Resistivity Tomography(ERT)was used to investigate the migration and distribution of Dense Non-Aqueous Phase Liquid(DNAPL)in heterogeneous porous media by carring out migration test in a two-dimensional sand trough with a clay soil lens.During the test,the resistivity imaging system is used for dynamic monitoring.After collecting the voltage and current data,the corresponding resistance value is obtained and converted into the apparent resistivity value.The data is processed by Surfer software to obtain the relative resistivity variation distribution image of the DNAPL migration process.The results show that the relative resistivity value increases with the increase of pollutant concentration.The relative resistivity variation distribution image at different times corresponds to the migration process of DNAPL,which can clearly define the migration path and distribution range of DNAPL.During the process of infiltration,DNAPL is controlled by gravity and capillary force,mainly in vertical migration.When moving to the clay lens body,it shows obvious lateral migration.It bypasses the lens body and continues to infiltrate and finally accumulates at the bottom of the sand trough.This study has important scientific value in further enriching the understanding of the transport mechanism and distribution characteristics of DNAPL contaminants under actual environmental conditions and developing feasible DNAPL pollutant treatment programs.