Simulation of the Migration Law of Cr(VI) in Groundwater Using a Fully Coupled Numerical Model

Coupled numerical models are widely used to investigate heavy metal migration in groundwater. This study selected a chromium slag stacking site and its surrounding area in Henan Province, China, as the research area to investigate the effective prevention of soil and groundwater pollution caused by hexavalent chromium (Cr(VI)), a by-product of chromium salt production. To this end, a three-dimensional numerical model of water flow and solute transport, fully coupled with convective dispersion, was constructed. The model was employed to examine the migration patterns of Cr(VI) in soil and groundwater while considering the influence of phreatic surface fluctuations caused by rainfall infiltration and soil matrix adsorption. The simulation results demonstrated that rainfall enhanced groundwater convection and dispersion and promoted the migration of Cr(VI). In the vadose zone, the Cr(VI) concentration at the plume center decreased from 568 to 307 mg kg⁻¹ under rainfall conditions, compared with a decrease to 224 mg kg⁻¹ without rainfall over five years. The investigation of soil adsorption revealed that adsorption by the soil matrix expanded the range of variation in Cr(VI) concentration while reducing the overall migration quantity compared with conditions without rainfall.