Massoudieh Arash, Ginn Timothy R
Department Civil and Environmental Engineering, University of California, Davis, Davis, CA 95616, USA.
J Contam Hydrol. 2007 Jul 17;92(3-4):162-83. doi: 10.1016/j.jconhyd.2007.01.005. Epub 2007 Jan 13.
Colloid-facilitated transport has been recognized as a potentially important and overlooked contaminant transport process. In particular, it has been observed that conventional two phase sorption models are often unable to explain transport of highly sorbing compounds in the subsurface appropriately in the presence of colloids. In this study a one-dimensional model for colloid-facilitated transport of chemicals in unsaturated porous media is developed. The model has parts for simulating coupled flow, and colloid transport and dissolved and colloidal contaminant transport. Richards' equation is solved to model unsaturated flow, and the effect of colloid entrapment and release on porosity and hydraulic conductivity of the porous media is incorporated into the model. Both random sequential adsorption and Langmuir approaches have been implemented in the model in order to incorporate the effect of surface jamming. The concept of entrapment of colloids into the air-water interface is used for taking into account the effect of retardation caused due to existence of the air phase. A non-equilibrium sorption approach with options of linear and Langmuir sorption assumptions are implemented that can represent the competition and site saturation effects on sorption of multiple compounds both to the solid matrix and to the colloidal particles. Several demonstration calculations are performed and the conditions in which the non-equilibrium model can be approximated by an equilibrium model are also studied.
胶体促进迁移已被认为是一种潜在重要但被忽视的污染物迁移过程。特别是，人们观察到，在存在胶体的情况下，传统的两相吸附模型往往无法恰当地解释高吸附性化合物在地下的迁移。在本研究中，开发了一个用于模拟非饱和多孔介质中胶体促进化学物质迁移的一维模型。该模型有用于模拟耦合流、胶体迁移以及溶解态和胶体态污染物迁移的部分。求解理查兹方程以模拟非饱和流，并将胶体截留和释放对多孔介质孔隙率和水力传导率的影响纳入模型。为了纳入表面堵塞的影响，模型中同时实现了随机顺序吸附和朗缪尔方法。利用胶体截留在气 - 水界面的概念来考虑气相存在导致的阻滞效应。实施了具有线性和朗缪尔吸附假设选项的非平衡吸附方法，该方法可以表示多种化合物在固体基质和胶体颗粒上吸附的竞争和位点饱和效应。进行了几个示例计算，并研究了非平衡模型可以由平衡模型近似的条件。
