Evolutionary Mechanisms and Controlling Factors of Acid Mine Water Using Reactive Transport Modeling

The pollution of acidic mine water (AMW) has become a global common mining environmental problem. To clarify the formation mechanisms and key controlling factors of acid mine water (AMW), this study conducted leaching experiments and reactive transport simulations using PHREEQC, based on the hydrogeochemical conditions of the Tianmashan mining area in Tongling, China. The mechanism, spatiotemporal evolution characteristics, and main controlling factors of pyrite oxidation dissolution in groundwater acidification process are systematically analyzed. The results show: (1) the numerical simulation agrees well with experimental data (R2 = 0.973), indicating that the model can effectively capture the transport processes of AMW; (2) high dissolved oxygen (DO) concentration shortens the acidification lag phase and accelerates reaction front advancement; Under the O2(g)-controlled continuous oxygen-supply conditions, Fe3+ sustains the reaction rate and stabilizes Fe(OH)3 precipitation, while Fe2+ has a delayed regulatory effect; Groundwater flow velocity mainly influences local reaction rates and solute transport but has little impact on overall control; (3) the transport process of AMW sequentially advances from the acidification zone, accompanied by Fe2+ release, Fe3+ accumulation, and Fe(OH)3 precipitation, showing a stepwise evolution. These findings reveal key geochemical mechanisms in AMW formation and provide a scientific basis for identifying environmental risk and prevention and control of AMW.