Resistivity And Complex Resistivity Method Study Of Chromium-contaminated Soil

In recent years, the development of Chinese industry becomes faster and faster.But there are many environmental pollution problems in the process of rapidindustrial development, especially heavy metal contamination of soil. Geophysicalmethods due to its unique advantages: fast, efficient, economic. So it has been usedfor the detection of soil heavy metal contaminated soil. As the soil has propertiessimilar to rock, but not exactly the same as the rock. The texture of soil is loose. Whenthe moisture content of soil increased, the degree of the gap between soil particles willalso change. So soil has its own specific complexity.In this thesis，large number of domestic and foreign studies of environmentalgeophysical methods and characteristics of heavy metal contaminated soil have beenanalyzed. After that we developed a reliable experimental device which can be usedmeasure complex resistivity measurements and resistivity of soil indoor: Everyinstrument research and development formulation aspects have been verified byexperiment and empiric summarized in order to ensure accuracy, stability andrepeatability of the measured data.The device is divided into the time domain and frequency domain measurementpart. Time domain：Powered supply electrodes named AB of “Miller soil box”;Measuring electrode named MN; Time of voltage charge and discharge; Dischargecurve of voltage; Above of all have been studied by systematic experimental.Frequency domain: the establishment of the device of complex resistivitymeasurements. Waveform and frequency of the voltage, measurement acquisitionmode are unified based on Labview. Thence device of complex resistivitymeasurements of soil indoor have been developed to complete.Then the device was used to do physical simulation experiment: Get10soilsamples which were configured according to the configuration standards of soil into10soil samples of different concentration of pollutants. Each soil sample was dividedinto three kinds of different porosity and four different moisture contents. Thephysical parameters that can be measured: Resistivity, polarization rate, amplitude,phase. These regularity of physical parameters such as soil moisture content, porosity,concentration of pollutants were be analyzed.Outdoor chromium pollution simulation site was established. The steel electrodes and non-polarized electrodes were placed on the position of the measuring line bypre-designed. Then these electrodes were connected to the device of time domain andfrequency domain measuring. After that, resistivity and complex resistivity can canbegin to be measured.The emphasis of complex resistivity method was to find the characteristics of theamplitude and phase dispersion of soil with different moisture content and chromiumcontaminated and porosity focused on the ultra-low frequency band.（2-5～26Hz）Experimental results show that complex resistivity amplitude of chromiumcontaminated soil increases with the increase in frequency. Phase changes vary withfrequency; Phase-frequency curve was a horizontally placed S-shaped curve. Thephysical parameters such as moisture content, the concentration of chromiumcontamination and porosity of soil will impact the amplitude and phase of the soilcomplex resistivity. However, the maximum and the minimum value of the phasechange sensitive when moisture content and porosity of soil change and no law to theconcentration of chromium pollution.The electrodes without moving were connected with AGI high-density electricalinstrument to be used to measure again. Using2D inversion software，2D Inversionimage of resistivity was compared with surfer image whose data was collected bydevice of complex resistivity. The results show that the detection effect of the devicewas similar to2D Inversion image of resistivity. And the results were effective. Phaseand amplitude spectrograms were also similar to the indoor complex resistivityexperiments which show that the data collected by the device is reliable.