C-Ride Module

The C-Ride Module for HYDRUS (2D/3D) Simulating Two-Dimensional Colloid-Facilitated Solute Transport in Variably-Saturated Porous Media.

Strongly sorbing contaminants (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 mobile colloidal particles (e.g., microbes, humic substances, suspended clay particles and metal oxides) 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 various processes associated with colloid and Colloid-Facilitated Solute Transport (CFSTr) in variably-saturated porous media.

The model accounts for:

• transient variably-saturated water flow
• colloid movement
• solute movement due to advection, diffusion, and dispersion
• 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, thus fully accounting for the dynamics of colloid transfer between different phases. Applications of the model are demonstrated using several test examples.

The Number of Solutes has to be set to 3 (to account for the transport of colloids, solute attached to colloids, and solute).

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.

C-Ride Manual:

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, 42 pp., 2012.

See the C-Ride Background and related information at https://www.pc-progress.com/en/Default.aspx?h3d2-C-Ride.