Colloid-Facilitated Solute Transport (C-Ride) Module
Strongly sorbing chemicals (e.g., heavy metals, radionuclides, pharmaceuticals, pesticides, and explosives) in porous media are associated predominantly with the solid phase, which is commonly assumed to be stationary. However, recent field- and laboratory-scale observations have shown that in the presence of mobile colloidal particles (e.g., microbes, humic substances, clays and metal oxides), colloids can act as pollutant carriers and thus provide a rapid transport pathway for strongly sorbing contaminants. To address this problem, we have developed a two-dimensional numerical module C-Ride for the HYDRUS (2D/3D) software package that incorporates mechanisms associated with colloid and Colloid-Facilitated Solute Transport (CFSTr) in variably-saturated porous media. The model accounts for transient variably-saturated water flow, and for both colloid and solute movement due to advection, diffusion, and dispersion, as well as for solute movement facilitated by colloid transport. The colloid transport module additionally considers the processes of attachment/detachment to/from the solid phase and straining. Various blocking and depth dependent functions can be used to modify the attachment and straining coefficients. The solute transport module uses the concept of two-site sorption to describe nonequilibrium adsorption-desorption reactions to the solid phase. The module further assumes that contaminants can be sorbed onto surfaces of both deposited and mobile colloids, fully accounting for the dynamics of colloid movement between different phases. Applications of the model are demonstrated using several selected test examples.
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Download the manual of the Colloid-Facilitated Solute Transport (C-Ride) Module in HYDRUS (pdf).
Download examples demonstrating the use of the Colloid-Facilitated Solute Transport (C-Ride) Module in HYDRUS. (C-Ride Examples). Note that these projects were created with version 2, and users using higher Hydrus versions need to convert them to their particular version.
References:
Šimůnek, J., Changming He, J. L. Pang, and S. A. Bradford, Colloid-facilitated transport in variably-saturated porous media: Numerical model and experimental verification, Vadose Zone Journal, 5, 1035-1047, 2006.
Šimůnek, J., M. Th. van Genuchten, and M. Šejna, Modeling Subsurface Water Flow and Solute Transport with HYDRUS and Related Numerical Software Packages, In: Garcia-Navarro & Playán (eds.), Numerical Modelling of Hydrodynamics for Water Resources, An International Workshop, Centro Politecnico Superior, University of Zaragoza Spain, June 18-21 2007. Taylor & Francis Group, London, ISBN 978-0-415-44056-1, 95-114, 2007.
Šimůnek, J., M. Šejna, and M. Th. van Genuchten, The C-Ride Module for HYDRUS (2D/3D) Simulating Two-Dimensional Colloid-Facilitated Solute Transport in Variably-Saturated Porous Media, Version 1.0, PC Progress, Prague, Czech Republic, 45 pp., 2012.