Multi-Method Comprehensive Investigation and Evaluation on the Effect of in-situ Engineering Disposal of Contaminated Mine Water

Mine water pollution caused by improper discharge of industrial wastewater, waste liquid and waste residue into mined-out areas is a new form of pollution occurred in China in recent years. This kind of pollution is buried deeply, and it is difficult to control, dispose and repair. Deep contaminated mine water from abandoned mining areas may even enter the ocean, posing a great threat to marine ecosystems. In this study, using a water pollution incident occurred in a coal field at a depth of 80 m in Shandong Province, China, in 2015, as an example, the methods of engineering block disposal and groundwater remediation are reported, and the remediation effects are tested and evaluated by in-situ chemical detection and geophysical surveys. The test results showed that engineering blocking measures such as cut-off walls can obviously block the DNAPL diffusion process in mine water, but the blocking effect on organic pollutants dissolved in water was limited. It can slow down the diffusion process of organic gas. The presence of mining tunnels and mined-out areas in the contaminated zone enhances the diffusion speed of various pollutants, especially during the remediation process when pollutants rapidly spread throughout the entire contaminated area. Groundwater circulation extraction and oxidation methods have a significant degradation effect on pollutants like dichloromethane, but they may generate a large amount of secondary gaseous pollutants. These gaseous pollutants may migrate to the shallow subsurface through structures such as faults, leading to secondary subsurface contamination. When designing remediation plans, it is crucial to strike a balance between blocking and guiding in the context of both blocking and restoration projects for achieving effective remediation.