Adsorption and migration behaviors of heavy metals (As, Cd, and Cr) in single and binary systems in typical Chinese...

In this study, the competitive adsorption and migration behaviors of arsenic (As), cadmium (Cd), and chromium (Cr) in typical Chinese soils were investigated. It was observed that Hainan, Shanxi, and Zhejiang Mengjiadai soils exhibited the highest adsorption capacities for As (563 μg/g), Cd (653 μg/g), and Cr (383 μg/g), respectively. Heavy metals (HMs) adsorption capacities were predicted by Extreme gradient boosting (XGBoost) models, and the Shapley additive explanation (SHAP) was employed to elucidate the effect of soil physicochemical properties on target values. Due to redox and complexation reaction, the primary factor affecting adsorption has changed from free state manganese (Mn) in single As system to antimony (Sb) in As/Cd and As/Cr systems. Furthermore, the maximum adsorption capacity (Q_m) of As increased by 49.4 % with the addition of Cd into Heilongjiang soil. Finally, the migration process of HMs in Heilongjiang, Hebei, and Hainan soils was simulated by column experiments. With a relatively large dispersion coefficient (D = 29.630 cm²/h) and small retardation factor (R_h = 0.030), Cr penetrated fastest in Heilongjiang soil. This research demonstrates that both the types and coexistence of HMs may affect the HMs behaviors in soil.