Objective The present study aims to investigate the spatial distribution characteristics of As in the soil of industrial sites, and to reveal its migration rules via relevant in-situ and indoor experiments based on field sampling. The research seeks to provide data and a theoretical basis for the prevention and control of As pollution in industrial site soil.

Method An industrial site in Huludao was selected as the research area. Firstly, the spatial distribution characteristics of soil As content in the site were described. Two experimental methods (including isothermal and dynamic adsorption experiments) were compared for the determination of As(Ⅲ) adsorption parameters in soil. Finally, the HYDRUS-1D model was employed to calculate the migration parameters of As (Ⅲ).

Result The results of in-situ soil experiments revealed significant differences in the horizontal distribution of As in the site, with the element being primarily enriched at a depth of 40 cm in the vertical direction, and decreasing with increasing depth. Based on the results of isothermal adsorption experiments, the equilibrium solid phase concentration of As (Ⅲ) in soil samples displayed a nonlinear growth trend with increasing liquid phase concentration. The Langmuir model (R² = 0.988) exhibited better fitting performance than the Henry and Freundlich models. The dynamic adsorption experiments demonstrated that the relative concentration of As (Ⅲ) completely penetrated the soil column, and the volume of liquid required to achieve full penetration decreased with increasing initial concentration. Among the three types of adsorption models, the Langmuir model (R² = 0.990) was deemed more suitable for simulating the dynamic adsorption process of As (Ⅲ) in soil samples. When simulating the migration behavior of As(Ⅲ), the dynamic adsorption experiment more closely approximated the actual migration process.

Conclusion The research results indicate that the As pollution in this site stemmed from industrial activities, and was primarily concentrated in shallow soil. The migration behavior of As (Ⅲ) exhibited a nonlinear process, with higher initial concentrations accelerating vertical migration. The dynamic adsorption experimental method should be preferentially employed in the study of soil As migration and parameter acquisition.