三氯乙烯污染土壤的复电阻率特征和频谱参数研究

Complex resistivity properties and spectral parameters of TCE contaminated soils.

复电阻率法(complex resistivity,CR)由于其对孔隙水化学性质、固液界面和流体含量的敏感性已成为具有良好前景的污染物识别工具。本研究选取三氯乙烯(trichloroethylene,TCE)作为典型有机污染物,利用频谱激电仪对TCE污染土壤进行了复电阻率测量,讨论孔隙水盐度、水饱和度和土壤类型对污染土壤的复电阻率特征和频谱参数影响。试验结果表明:污染土样的复电阻率均随水饱和度的降低和孔隙水盐度的减小而增大;土壤黏土含量影响孔隙水连续性,当孔隙水出现不连续状态时,实部和虚部出现大幅度变化。总充电率M随着孔隙水盐度的增加而增加,随水饱和度的降低先减后增。黏土颗粒重排导致的比表面积减小使得总充电率M减小,双电层极化加强使总充电率M升高;平均弛豫时间常数随孔隙水盐度的升高而降低,二者呈对数相关,随水饱和度变化的主要原因为可极化孔隙尺寸的变化。本研究探讨了地球物理参数与水文地质参数间的关系,为SIP方法在实际有机污染场地调查与评估提供了理论依据。

The complex resistivity has become a promising contaminant monitoring tool due to its sensitivity to pore water chemical properties,solid-liquid interface and fluid content.In this study,we chose trichloroethylene(TCE)as a typical organic contaminant and measured the complex resistivity of TCE contaminated soils by SIP method.We studied the effects of pore water salinity,water saturation and soil types on the complex resistivity characteristics and spectral parameters of TCE-contaminated soils.Results show that the complex resistivity of contaminated soil samples increases with decreasing water saturation and pore water salinity.The clay content affects the continuity of pore water.When the pore water is discontinuous,the real and imaginary parts change greatly.The total chargeability(M)increases with decreasing pore water salinity and decreases at first and then increases with decreasing water saturation.M is also reduced by decreasing specific surface area caused by the rearrangement of clay particles and increased by double layer polarization.The mean relaxation time decreases with increasing pore water salinity as shown by a logarithmic correlation.The main reason for the variation of M with water saturation is the change of polarizable pore size.This study establishes a relationship between geophysical and hydrogeological parameters,thus providing a theoretical basis for SIP field measurements.