Simulation of Groundwater Pollutant Transport Characteristics in Mining Areas Driven by Subsurface Flow Velocity Fields

Groundwater pollution in chemical industrial parks is typically concealed, delayed in onset, and difficult to remediate. Moreover, the long-term migration of typical pollutants in aquifers may threaten the safety of surrounding water sources and river water environments. In this study, a numerical subsurface flow model was constructed for a chemical industrial park in a mining area of Inner Mongolia by generalizing the Quaternary loose-rock pore aquifer system, based on hydrogeological surveys and groundwater monitoring data, using MODFLOW. A solute transport model was then established through coupling with MT3DMS to predict the spatiotemporal evolution of ammonia nitrogen and 1,2-dichloroethane in the absence of new pollution sources, and the influence of subsurface flow velocity on pollutant diffusion was further analyzed. The results show that the contaminant plume area gradually increases over the simulation period: the ammonia nitrogen plume expands from 1.84 km2 to 3.98 km2, and the 1,2-dichloroethane plume expands from 1.47 km2 to 3.05 km2. Contaminant concentrations in individual wells generally exhibit a downward trend; nonetheless, long-term exceedance risks persist at specific sites. These findings provide a scientific basis for groundwater pollution risk management, water source protection, and subsequent remediation decisions for chemical industrial parks in arid and semi-arid regions.