Migration mechanism of pollutants in karst groundwater system of tailings impoundment and management control effect analysis: Gold mine tailing impoundment case

Tailing impoundments are sources of high-risk pollution due to the accumulation of mining tailings and wastewater. As a result of thin karst overburden as well as actions of precipitation leaching and scouring, pollutants in the tailing impoundment can easily enter the karst aquifer through sinkholes, corrosion fissures and other channels, causing pollution to groundwater and is not conducive to the utilization of groundwater resources. Through the analysis of hydrogeological conditions, the boundary condition, aquifer structure, source-sink term, and hydraulic characteristics of groundwater are generalized, the groundwater flow model and solute migration model were established, and the migration mechanism of the characteristic pollutant (arsenic ions) was analyzed. The research results show that with the passage of time, the area of high-concentration polluted areas showed a decreasing trend, and the area of low-concentration polluted areas showed a decreasing trend; Under the influence of groundwater flow and the pollutant concentration difference, the pollution plume presents an elliptical shape with the long axis along the direction of water flow; The migration law of pollutants is controlled by the direction of groundwater flow, the concentration difference of pollutants and the permeability of the aqueous medium; The direction of groundwater flow determines the migration direction of pollutants, the concentration difference of pollutants determines the diffusion range of pollutants, and the permeability of aqueous media determines the migration speed of pollutants; Through the prediction of the pollutant control effect, it can be found that a reasonable number of pumping wells that do not interfere with each other are arranged around the groundwater flow channel, which can effectively control the migration of pollutants to the target area. The above research reveals the migration mechanism of pollutants in karst groundwater and main control factors, and also provides a scientific basis for the protection of groundwater resources in karst areas.