盐度对PCE在饱水单裂隙中运移分布及质量溶出的影响

The influence of salinity on the migration distribution and mass dissolution in saturated single fissure

为研究盐度对重非水相液体(dense non⁃aqueous liquid,DNAPL)污染物在饱水单裂隙中运移分布以及溶出行为的影响,选取四氯乙烯(perchlorethylene,PCE)作为代表性DNAPL,通过改变流经裂隙介质中盐溶液浓度,测定不同盐度条件下PCE/水/裂隙介质三相体系中界面张力和接触角,并用光透法实时监测PCE在二维裂隙介质中运移分布的动态变化过程,同时用气相⁃顶空色谱分析法测定PCE溶出浓度,进一步对比分析不同情形下相应污染源区结构及PCE溶出浓度变化.结果表明:随着盐度增加,PCE/水/裂隙介质三相体系中界面张力增大,而接触角减小.盐度通过改变PCE/水/裂隙介质三相体系中界面张力和接触角,从而影响PCE在裂隙介质中的运移及分布,具体表现为在高盐度水流中PCE运移速率加快,分布面积增大.此外,盐度通过影响PCE污染源区面积从而影响PCE溶出浓度,且污染源区面积与溶出浓度表现出明显的正相关性,均先迅速增大而后趋于平稳;高流速水流条件会增大盐度的影响程度.

This study investigated the influence of salinity on the migration,distribution and dissolution of dense non⁃aqueous liquid(DNAPL)in saturated single fracture.Tetrachloroethylene(PCE)was selected as the representative,and measurement of interfacial tensions(IFTs)and contact angles for the PCE/water/fractured media system were conducted under different salinity.The migration and distribution process of PCE in simulated fractured media were dynamically monitored by light transmission method,while the PCE dissolution was determined with headspace gas chromatograph.This experiments were carried out at different water salinities and velocities,and the corresponding changes in source zone architecture and dissolution concentration were then analyzed.Results showed that with the increase of water salinity,the IFTs increased and the contact angles of PCE decreased,and thereby affected the migration and distribution of PCE in the fractured media.The migration rate of PCE and the PCE source zone area were observed to increase with salinity increasing.Moreover,the variation in PCE distribution induced by different salinities further changed the dissolution of PCE.The changes of the PCE source area and the dissolved concentration showed obvious consistency,both of which first increased rapidly and then stabilized,and the influence of salinity increased with flow velocity.