水动力因素对砷在河砂中迁移影响的柱试验与模拟

河岸带作为一种典型的地下水-地表水相互作用带，不同水动力学条件下砷在该作用带中的行为较少有研究报道。基于此，采集河岸带河砂开展室内柱试验，分析不同水动力因素（包括流速和粒径）对砷在河砂中迁移的影响并建立相关模型。结果表明:(1) 0.5 mL/min流速下，河砂对As(V)的吸附速度和达到平衡所需的时间均比As(III)快，且粒径越小，该现象越明显；1.0 mL/min流速下，不同粒径的河砂对As(V)的吸附速度随粒径的增大而增大，对As(III)的吸附则没有明显差异；(2) 相同粒径的填充柱中，河砂对As(III)和As(V)的吸附能力均随流速的增加而降低；(3)不同流速和粒径条件下，As(III)和As(V)在砂柱中的迁移过程均更符合Thomas模型，拟合R2高于相同条件下Yoon-Nelson和Adams-Bohart模型。其中，低流速下，Thomas模型对0.15～0.25 mm粒径中As(III)和As(V)迁移过程拟合的R2（≥0.94）显著优于1.00～2.00 mm的较大粒径；高流速下，该模型对不同粒径中砷迁移过程的拟合R2差异不大。研究有助于加深对地下水-地表水相互作用下水动力因素对砷迁移转化规律影响的认识，并丰富和完善高砷地下水形成的机制理论。

Influence of hydrodynamic factors on the migration of arsenic in river sand: Column experiment and models

The riparian zone is a typical groundwater-surface water interaction zone, and there are few research reports on the behavior of arsenic in this interaction zone under different hydrodynamic conditions. In this study, the river sand samples from the riparian zone are collected to carry out indoor column experiments, the influence of different hydrodynamic factors (including flow velocity and particle size) on the migration of arsenic in the river sand are analyzed, and related models are established. The results show that (1) at a flow rate of 0.5 mL/min, the adsorption rate of the river sand on As(V) and the time required to reach an equilibrium state are both faster than those on As(III), and the smaller the particle size, the more obvious the phenomenon; at a flow rate of 1.0 mL/min, the adsorption rate of the river sand with different particle sizes on As(V) increases with the increasinng particle size, but there is no significant difference in the adsorption of As(III). (2) In a packed column filled with sand of the same particle size, the adsorption capacity of the river sand for As(III) and As(V) decreases with the increasing flow velocity. (3) Under the conditions of different flow rates and particle sizes, the migration processes of As(III) and As(V) in the sand column are more in line with the Thomas model, and the fitting R2 are higher than those of the Yoon-Nelson and Adams-Bohart models under the same conditions. Among them, at low flow rates, the Thomas model fitting R2 (≥0.94) to the migration processes of As(III) and As(V) in the particle size of 0.15?0.25 mm are significantly better than that of the larger particle size of 1.00?2.00 mm. At high flow rates, the model has little difference in fitting R2 to the migration process of arsenic in different particle sizes.