نبذة مختصرة : Karst regions are rich in mineral resources, and tailings ponds-essential facilities for maintaining normal production in mining enterprises-are often inevitably constructed on carbonate formations in these areas. However, the complex hydrogeological conditions in karst regions, including well-developed karst features such as sinkholes, swallow holes, and underground karst channels, make tailings ponds highly susceptible to leakage. This leakage can lead to surface and groundwater contamination, posing significant challenges to regional groundwater pollution control. Therefore, identifying underground karst channels beneath tailings ponds and characterizing their leakage patterns are critical for mitigating pollution in karst regions. To investigate leakage channels in karst tailings ponds, this study focuses on the Zhatang red mud tailings pond in Guizhou Province, which is located in a well-developed karst region and has experienced leachate leakage. A systematic approach integrating geophysical exploration techniques-including the high-density resistivity method and transient electromagnetic method-hydrogeological drilling, tracer tests, and 3D geological modeling was employed to identify karst leakage channels and construct a detailed visual model. Dense survey lines for the transient electromagnetic and high-density resistivity methods were arranged in a grid pattern within Ponds 2, 5, and 6. Using the inverse distance weighting (IDW) algorithm, 3D resistivity models of the strata were developed, effectively identifying low-resistivity anomalies in the pond area. The models revealed that the low-resistivity anomalies in Pond 5 and Pond 6 predominantly exhibited a north-south distribution, corresponding to the main leakage channels toward the Damawo, Lujiawan, and S703 seepage points. In Pond 2, a banded low-resistivity anomaly extending southeast was identified as the leakage channel for the S704 spring. Based on the 3D resistivity models, additional high-density resistivity and transient electromagnetic survey lines were deployed outside the pond area to further delineate the developmental patterns of karst leakage channels. The integrated interpretation of exploration results from both inside and outside the pond area clarified the spatial distribution characteristics of these leakage channels. Hydrogeological drilling, borehole television imaging, and tracer tests were conducted to validate the karst leakage channels identified by geophysical methods. Drilling results confirmed that the low-resistivity anomalies corresponded to fractured zones and areas filled with high-concentration leachate. For instance, boreholes Z11 and Z16 intercepted leachate-saturated zones, while Z17 and Z19 revealed intense shallow karst development. Boreholes Z15 and Z14 demonstrated the hydraulic connectivity of dissolution cavities along lithological boundaries. Tracer tests further verified the karst leakage channel toward the S704 spring.By combining geophysical exploration with 3D geological modeling and integrating multi-source data-including 119 actual boreholes, 104 virtual boreholes, geophysical interpretation results, and UAV topographic surveys-a refined 3D geological model and a leakage channel model of the study area were developed. The 3D geological model visually represents stratigraphic interfaces, lithology, terrain, fault distributions, and tailings pond boundaries, enabling cross-sectional visualization at any location. The leakage channel model accurately identifies karst leakage channels and lateral groundwater recharge channels, clearly delineating the spatial distribution pattern of pollution sources (low-resistivity zones within the pond), migration channels (karst channels controlled by structures or stratigraphic boundaries), and discharge endpoints (springs). This model elucidates the groundwater "recharge-flow-discharge" system in the study area. The leakage channel model demonstrates that groundwater movement is primarily controlled by structural and stratigraphic boundaries, with karst leakage zones predominantly developing along faults and lithological interfaces. For example, the Lujiawan and S703 spring channels are associated with faults F3 and F5, while the S704 spring channel follows the boundary between the Longtan and Maokou Formations. The karst channel model visualizes the spatial distribution of underground features and the leachate migration process, providing critical insights for assessing groundwater contamination risks and designing remediation strategies for the Zhatang red mud tailings pond. This study innovatively integrates geophysical exploration with 3D geological modeling, enabling comprehensive analysis of geological data and overcoming the limitations of traditional 2D interpretations. In scenarios with limited borehole data, this method significantly enhances the accuracy of detecting karst groundwater channels and improves model representation. It offers a novel approach for precisely locating leakage channels and visualizing pollution processes in karst tailings ponds. The research findings provide a scientific foundation for designing remediation measures such as grouting leakage channels and altering flow directions, thereby substantially reducing wastewater treatment costs and yielding significant environmental and economic benefits.
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