## 4 Discussion and Conclusions  
The study area is located in the Luliang mountainous area in Shanxi Province. Although the complex topography and geomorphology bring certain difficulties to the exploration of the goal, the results of this study show that the application of combining CSAMT and the activated-carbon method for radon measurement for the detection of the goal was successful. CSAMT integrates the merits of great detection depth, high resolution, and capability to identify the water accumulation status in the goal. However, it is easily affected by the static effect and near-field effect. The conductors near the transmitting terminal may interfere with the emission source, which can very easily affect the measurement accuracy in regions with complicated topography, landform, and working environments. However, the activated-carbon method for radon measurement is not influenced by the terrain, earth electricity, or EMF. Nevertheless, this method fails to interpret the goal depth. Accordingly, the two methods can exploit each other for reference to compensate for their disadvantages. In this field survey work, the CSAMT and activated-carbon method for radon measurement were combined into a comprehensive geophysical prospecting method to study the underground goal situation in a mining area. First, CSAMT was used to probe the depth sounding in the goal. One low-resistivity anomaly zone and one high-resistivity anomaly zone were discovered, where the latter was inferred as the goat anomaly zone and the former formed through the water accumulation in the goat or the water enrichment at rock strata, thereby being inferred as the water accumulation anomaly zone in the goat. The activated-carbon method for radon measurement was then used to infer the position and range of the underground goal. With the CSAMT prospecting results combined, the goat was inferred to be the radon-value anomaly zone. The prospecting results obtained by the two methods were combined to complete the geophysical prospecting of the underground goal in this mining area. In the end, the known data, field geological investigation, CSAMT, and activated-carbon method for radon measurement were integrated for a comprehensive interpretation, thereby completing the goat interpretation in the exploration area, which was then verified through drill holes, as shown in Figure 15. The results show that the boundaries of the goat range detected by the two exploration methods do not coincide exactly. This means that if one exploration method is used for exploration, the results do not mean that the goat area has been fully discovered. This also confirms that each geophysical exploration method has its own advantages and disadvantages. Synthesizing the advantages of each method to avoid its disadvantages will make its detection results more referenced. Figure 14: Contour Line Plane of Radon Values Measured by Activated Carbon and Goaf Anomaly Interpretation (Red Wireframe) Map. Since the goat area detected by the two methods does not completely coincide, it cannot be proved that the goat area range is 100% identified. In theory, the more detection methods used, the more accurate the results obtained are. However, it is necessary to take into account the burden of time, economy, labor, and other expenses as well as the fact that the comprehensive detection scheme of multiple methods is difficult to implement, and the detection accuracy of these two methods is enough to meet the needs of most engineering projects. The actual results manifested that the comprehensive geophysical prospecting method integrating CSAMT and the activated-carbon method for radon measurement can indeed complete the prospecting work economically, rapidly, and accurately. This comprehensive prospecting method also experienced a minor influence from various factors such as topography, landform, and geological conditions. Therefore, it has great reference significance in practical engineering explorations.