Simulation of the natural attenuation of groundwater contaminated by acid in situ leaching at a uranium mine

This study focuses on the simulation of the natural attenuation of groundwater contaminated by acid-leached uranium at a decommissioned uranium mining site. Although natural attenuation by mixing and dilution, pH buffering, adsorption, and reduction has been well described, little research on the simulation of the natural attenuation of groundwater U⁶⁺ and sulfuric acid in sandstone aquifers after mining has been performed. Using PHREEQC Version 3 software and the minteq.v4.dat database, in this paper, the thermodynamic adsorption equilibrium constants and adsorption site parameters were modified based on the experimental results of the mineral composition, chemical reactions, U⁶⁺ adsorption, and SO₄²⁻ reduction reactions. This study provides a basis for establishing detailed environmental background data files, conducting laboratory experiments, and predicting the natural attenuation capability of sandstone aquifers at uranium mining sites and their surrounding areas.