| As an emerging discipline,environmental geophysics is an extension of existing geophysical exploration techniques.It has been applied in the monitoring of environmental pollutants by using different methods.Compared with the traditional environmental drilling,it has advantages such as high efficiency,convenience,low cost,big and continuous data,which attracted much interest of both academia and industry.A large number of polluted sites in China lack effective and efficient fine characterization technology,and emerging environmental geophysical methods provide solutions to this dilemma.In this study,chromium pollution site was used as an example to construct correlation relationships through indoor studies on resistivity,pollutant concentration and media.And actual site exploration was carried out.With high-density electrical method（ERT）as the main detection technology,supplemented by ground-penetrating radar（GPR）,combined with laboratory research,the main research results are as follows:1.The experimental test was carried out using the dipole device,the Sloeberg device and the Wenner device.The results showed that the impact of the grounding method,the burial of the stainless steel needle and the flow direction of the solution on the resistivity was negligible.But the increasing in the flow rate would lead to an increase in resistivity.It has been experimentally proved that the addition of silt and clay to the fine sand respectively leads to a significant decrease in the resistivity of the soil medium.The resistivity of the medium at different temperatures is measured,and the existing formulas are used and was verified by experimental results,which will be conducive to the application of environmental geophysical exploration technology in different scenarios.2.Based on archie’s formula,three different devices were used to test different soil particles,saturation and solution concentrations.The relationships between the concentration of Cr（VI.）solution and the resistivity,soil particles and resistivity,saturation and resistivity were obtained,respectively.Through the combination of the three-part formula,the relationship between soil medium and resistivity under different device conditions was obtained.:（?）3.The one-dimensional sand column and two-dimensional sand groove test were carried out indoors.The flow process was monitored by three devices and the sampling test results were used as a control to determine the applicability of the fitted formula.Based on the results of the one-dimensional sand column,the proposed formula must be used in a long-term stable environment.The test results of the two-dimensional sand groove prove that the Wenner device has better stability.And some problems of the formula in practical applications need to be solved.4.The actual exploration of the site was carried out,and the Cr（VI.）distribution of the site was preliminarily mapped according to the analysis results.12 ERT profiles were completed within the site to identify the migration advantage flow channel of Cr（Ⅵ.）.The resistivity data is calculated by formula,and a three-dimensional concentration distribution is established by interpolation,which is compared and analyzed with the measured values of water samples.Through the GPR detection of groundwater wells in the site,the detection results supply to the ERT result.And the complementarity and rationality of the joint application of various environmental geophysical exploration technologies are also proved. |
