## 3 Comparative Analysis of Numerical Forward Simulation and Soil Trench Modeling Experiments
### Determination of the Location of the Heavily Contaminated Area  
In summary, it can be seen that: the integrated apparent amplitude frequency and apparent resistivity curve of the pollution field can be more effective in determining the specific location of the heavily polluted area of the pollution field. In a symmetrical quadrupole sounding device, the use of the edge of the pollution field to arrange the measurement point can be a better way to make a judgment on the top and bottom of the pollution field depth. This section takes the migration model of the pollution field on the 100 th day as an example; synthesizing the monitoring curves of the apparent amplitude frequency and apparent resistivity of the pollution field and makes a comprehensive profile and sounding map (see Figure 15). (Sounding maps for both terrains were monitored using measurement point 2). On the 100 th day of pollutant migration, the exact position of the contaminated area in the ground projection is at 50-100 m, and the depth under flat terrain is at 0.1-4.7 m. With the depth of the top of the more contaminated area at 1.5 m, at which time the depth of the heavily contaminated area ranges from 1.5-4.7 m. The depth of the contaminated area under undulating terrain is at 2.1-6.7 m (with the height of the peak at 2 m). The depth of the top of the heavily polluted area is 3.5 m, at which time the depth of the heavily polluted area ranges from 3.5 to 6.7 m. From Figure 15, under the flat terrain, the horizontal projection orientation of the Cr heavy pollution area is located at 54.2-91.8 m, and the error is 4.2-8.2 m compared with the model, and the coincidence with the exact orientation is 75.2%. The sounding orientation is located at 1.9-4.3 m, and the error is 0.4 m, and the coincidence with the exact orientation is 75.0%. In the undulating terrain, the horizontal projection bearing is located at 50.2-95.8 m, with an error of 0.2-4.2 m compared with the model, and the degree of coincidence with the exact bearing reaches 91.2%. The sounding bearing is located at 3.15-8.4 m, with an error of 0.35-1.7 m, and the monitoring values at the top and bottom have exceeded the precise values. Figure 14: Apparent resistivity map of pollution field sounding in different days (point 2). (a) Apparent resistivity curves for different days in flat terrain. (b) Apparent resistivity curves for different days in undulating terrain. +++ ==ERROR: No output for this page==
To summarize, the methods to improve the monitoring effect of the heavily polluted area are as follows:  
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has pointed out the superiority of using software to numerically simulate the migration of contaminated fields in the Section 5. In the study of this paper, the author simulated the migration of chromium contamination field with time using COMSOL software. Based on the model of the contamination field obtained after the migration, electrical monitoring with an intermediate gradient detection device and the symmetrical quadrupole sounding device was carried out. On this basis, different topographic structures were introduced to analyze the effects of the migration of the pollution field on the apparent resistivity and apparent amplitude frequency curves. First of all, the author used numerical forward simulation to simulate the migration of the contamination field because it is very difficult to implement experiments for validation. Difficulties include: The impossibility in practice of controlling the penetration of chromium solutions into the soil. The often irregular nature of chromium-contaminated areas. The fact that the spread of chromium-contaminated areas is subject to many uncertainties, and so on. Fortunately, although it is not possible to simulate the dynamic migration of chromium contamination field, the author has managed to implement electro-methodic monitoring of static chromium-contaminated areas, which has a positive significance in demonstrating the numerical simulation accuracy of our electro-methodic monitoring.