Study on migration characteristics of chromium contaminated site and Dual-Frequency IP method monitoring technology

In view of the fact that the migration process of chromium contaminated sites can be affected by a variety of uncertainties, its migration characteristics and monitoring process are difficult to study experimentally. Based on the basic law of groundwater flow and the migration mechanism of pollutants, COMSOL software was used to simulate and analyze the migration characteristics of chromium contaminants in static reserves and their changing rules. The reliability and accuracy of numerical forward simulations are verified by conducting physical modeling experiments of static earth tanks. The chromium pollution source migration model is used as the basic model for geoelectric monitoring. Based on the theory of dual-frequency induced polarization(IP) method, the intermediate gradient detection device and symmetrical quadrupole sounding device are used for pollution source migration monitoring to analyze the influence of terrain undulation and the orientation of the measurement point on the monitoring effect. The results show that during the migration of chromium pollutants, the permeable layer with a high permeability coefficient shows a strong adsorption effect on the heavily polluted area, and at the same time, it will intensify the lateral spreading of polluted areas in a short period of time. Correspondence of excitation anomalies between the peak apparent amplitude frequency and the trough of apparent resistivity is better for profiling than for bathymetric surveys. For symmetrical quadrupole sounding, a measuring point in the center of the projected edge of the contaminated field allows for more effective contamination monitoring. The presence of valleys may trigger "multiple peaks" in the excitation curve during profiling and bathymetric soundings. By setting up power supply electrodes on the mountain frontiers on both sides of the raised peaks and comprehensively mapping the apparent amplitude frequency and apparent resistivity curves of the chromium contamination field, whcih is effective in determining the exact location of the heavily contaminated area. The research results enrich the theory of monitoring heavy metal soil pollution field by dual-frequency IP method, whcih promote the ecological environmental protection.