铬污染土壤超低频复电阻率频散特性

在超低频段(2-5~26Hz)内,研究了铬污染土壤复电阻率在不同含水率、铬含量和孔隙率下的幅值及相位频散特性. 结果显示,铬污染土壤复电阻率的幅值随频率的增大呈单调递减趋势,但相位随频率的变化曲线呈平放的S形. 含水率、铬含量和孔隙率的变化均会引起土壤复电阻率的幅值和相位大小的改变,而相位峰值的位置只对含水率及孔隙率的变化较为敏感,与铬含量变化的关系不大. 含水率从0.08增至0.24时可导致相位峰值的位置产生约8Hz的右移；而当w(Cr6+)从0.5g/kg增至4.0g/kg时,相位峰值的位置基本不发生变化. 表明铬含量和含水率的增大均会引起电阻率减小的异常现象,若单纯地使用电阻率很难区分引起这2种异常现象的原因,但结合土壤复电阻率频散特性特别是相位峰值的位置可以进行有效判别,进而可判定铬污染场地的铬含量分布. 

The Complex Resistivity Dispersion Properties of Chromium-Contaminated Soil in the Ultra-Low Frequency Power Supply

The dispersion characteristics of soil complex resistivity amplitude and the phase angle were explored in ultra-low frequency range (2-5-26Hz), under different concentrations of chromium, moisture contents and porosities. The complex resistivity amplitude of chromium-contaminated soil monotonically decreased with the increase of frequency, while the phase angle changes was not monotonous, and the curve of phase versus frequency appeared to be a lay-flat S-shaped. Both complex resistivity amplitude and phase angle were influenced by changes of the moisture, concentrations of chromium salt and porosity. However, the peak position of the phase angle was only sensitive to changes of moisture content and porosity, and slightly sensitive to concentrations of chromium salt. The experimental data showed that the moisture contents varied from 0.08to 0.24and has a right shift at the frequency of 8Hz, however, the frequency position not changed while chromium salt concentration changed from 0.5to 4.0g/kg. The study results showed that the increase of both chromium-pollution concentration and moisture can cause the decrease of the resistivity, and it was difficult to distinguish by resistivity solely, however, it can be effectively distinguished by the combination of resistivity with complex resistivity dispersion characteristics, especially with the phase angle peak position, and then the distribution of chromium concentrations in chromium-pollution field can be determined.