为了解潜流带中地下水流速和介质颗粒对As（Ⅲ）迁移的影响，选用天然河砂为介质，配制地下水含As（Ⅲ）模拟液，开展室内批实验和动态柱实验并进行表征分析，探讨流速和介质粒径对As（Ⅲ）迁移的影响及机制.结果发现：（1）粒径越小的河砂与As（Ⅲ）相互作用平衡时间越长，As（Ⅲ）的单位吸附量（Q _e）随着河砂粒径的增大而减小（0.15~0.18 mm的粒径河砂除外），单层最大吸附量（Q _m）随着粒径的增大呈减小趋势；（2）As（Ⅲ）在河砂上的迁移行为表现出明显的粒径和流速效应；一方面，河砂粒径越小，比表面积越大，增加了水-砂相互作用时间和限制了地下水冲洗速度，不利于As（Ⅲ）在河砂中的迁移；另一方面，流速越大导致空隙通道内的水力剪切力增强，紊流强度的提高减小了滞留边界层厚度，利于As（Ⅲ）在河砂中的迁移.

To understand the influence of groundwater velocity and medium particles on As(Ⅲ) migration in the riparian zone, natural river sand is selected as the medium, and groundwater solutions containing As(Ⅲ) as commonly seen in some riparian zones are prepared to carry out batch experiments and dynamic column experiments. Combing with the characterization analysis, the influence and mechanism of velocity and medium particle size on As(Ⅲ) migration are discussed. The results show follows: (1) The adsorption equilibrium time of As(Ⅲ) is longer for the smaller particle size of river sand. The equilibrium adsorption capacity (Q _e) of As (Ⅲ) on the river sand decreases with the increase of its particle sizes (except for river sand with a particle size of 0.15-0.18 mm), and the maximum amount (Q _m) of monolayer adsorption shows a decreasing trend with the increase of particle size. (2) As(Ⅲ) migration in the column filled with river sand is significantly affected by the particle size and velocity. On one hand, the river sand of the smaller particle size has a larger specific surface area, which usually leads to longer interaction time between aqueous solutions and solid medium, thus limiting the groundwater flushing rate. This is not conducive to the migration of As(Ⅲ) in river sand. On the other hand, the higher flowing velocity leads to a stronger hydraulic shear force in the void channel. Meanwhile, the increase of turbulence intensity reduces the thickness of the retained boundary layer, which is conducive to the migration of As(Ⅲ) in river sand.