Study on Migration Monitoring Technology of Chromium-Contaminated Site Based on Dual-Frequency Induced Polarization Method

Abstract

In order to reveal the migration process of chromium-contaminated sites, COMSOL5.6 software was used to build the initial model of the chromium pollution source and analyze the migration change characteristics over time based on the rule of groundwater movement and Convection–Dispersion equation. COMSOL provides fully coupled multiphysics modeling for most engineering fields. The results show that: the permeable layer with a high permeability coefficient during the migration of chromium pollutants has a strong adsorption effect on the heavily polluted part, and it will enhance the lateral diffusion of the polluted area within a short period. Based on the migration model, the intermediate gradient and the symmetrical quadrupole sounding model are built. The variation law of apparent amplitude frequency and apparent resistivity under flat and undulating terrain is analyzed based on the dual frequency IP (Induced Polarization) method. The results show that: The intermediate gradient detection is better than the symmetrical quadrupole sounding in the correspondence between the peak value of apparent amplitude frequency and the valley value of apparent resistivity. The arrangement of the bathymetric measurement point in the center of the projected edge of the pollution field can be a better way to monitor the pollution. Monitoring with the intermediate gradient detection device and the symmetrical quadrupole sounding device creates “multiple peaks” in the curve as it passes through the valley. Arranging the power supply electrodes on the mountain frontiers on both sides of the raised peaks and synthesizes the apparent amplitude frequency and apparent resistivity curves of the pollution field, which can effectively determine the specific orientation of the heavily polluted area of the pollution field. This research makes theoretical additions to the migration characteristics of the Cr pollution field. It provides technical guidance for the real-time monitoring of the pollution field, which is of positive significance for promoting ecological and environmental protection.