Modeling colloid-facilitated transport of multi-species contaminants in unsaturated porous media.

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.

[1]  Tushar Kanti Sen,et al.  Review on subsurface colloids and colloid-associated contaminant transport in saturated porous media. , 2006, Advances in colloid and interface science.

[2]  J. Wan,et al.  Measuring Partition Coefficients of Colloids at Air-Water Interfaces , 1998 .

[3]  Menachem Elimelech,et al.  Dynamics of Colloid Deposition in Porous Media: Blocking Based on Random Sequential Adsorption , 1995 .

[4]  Larry D. McKay,et al.  Colloid Transport in the Subsurface: Past, Present, and Future Challenges , 2004 .

[5]  Fred K. Fong,et al.  Literature review and model (COMET) for colloid/metals transport in porous media , 1991 .

[6]  Kartic C. Khilar,et al.  Migrations of Fines in Porous Media , 1998 .

[7]  A. Lemley,et al.  TRANSPORT OF DISSOLVED ORGANIC MACROMOLECULES AND THEIR EFFECT ON THE TRANSPORT OF PHENANTHRENE IN POROUS MEDIA , 1991 .

[8]  Kartic C. Khilar,et al.  Colloid‐associated contaminant transport in porous media: 2. Mathematical modeling , 2002 .

[9]  William R. Penrose,et al.  Mobility of plutonium and americium through a shallow aquifer in a semiarid region , 1990 .

[10]  Constantinos V. Chrysikopoulos,et al.  Analysis of a model for contaminant transport in fractured media in the presence of colloids , 1995 .

[11]  M. Corapcioglu,et al.  Colloid‐facilitated groundwater contaminant transport , 1993 .

[12]  Bruce D. Honeyman,et al.  Geochemistry: Colloidal culprits in contamination , 1999, Nature.

[13]  Scott C. James,et al.  Transport of polydisperse colloid suspensions in a single fracture , 1999 .

[14]  J. Cary.  Estimating the surface area of fluid phase interfaces in porous media , 1994 .

[15]  Jiamin Wan,et al.  Partitioning of clay colloids at air-water interfaces. , 2002, Journal of colloid and interface science.

[16]  C. Guttman,et al.  Separation by Flow , 1970 .

[17]  C. Chrysikopoulos,et al.  Transport of polydisperse colloids in a saturated fracture with spatially variable aperture , 2000 .

[18]  C. Chrysikopoulos,et al.  Analytical solutions for monodisperse and polydisperse colloid transport in uniform fractures , 2003 .

[19]  M. Zembala,et al.  Reversible and irreversible adsorption of particles on homogeneous surfaces , 1992 .

[20]  Jiamin Wan,et al.  Colloid transport in unsaturated porous media , 1994 .

[21]  H. Frisch,et al.  Particle adhesion in model systems. Part 13.—Theory of multilayer deposition , 1991 .

[22]  C. Enfield,et al.  Macromolecular Transport of Hydrophobic Contaminants in Aqueous Environments. , 1988 .

[23]  J. McCarthy,et al.  Subsurface transport of contaminants , 1989 .

[24]  Jack C. Parker,et al.  Boundary Conditions for Displacement Experiments through Short Laboratory Soil Columns , 1984 .

[25]  The reactor accident at chernobyl: A possibility to test colloid-controlled transport of radionuclides in a shallow aquifer , 1988 .

[26]  Van Genuchten,et al.  A closed-form equation for predicting the hydraulic conductivity of unsaturated soils , 1980 .

[27]  J. Ryan,et al.  Colloid Movement in Unsaturated Porous Media: Recent Advances and Future Directions , 2004 .

[28]  K. Arulanandan.  Fundamental Aspects of Erosion of Cohesive Soils , 1975 .

[29]  T. Ginn,et al.  Colloid filtration theory and the Happel sphere-in-cell model revisited with direct numerical simulation of colloids. , 2005, Langmuir : the ACS journal of surfaces and colloids.

[30]  Julian Talbot,et al.  Surface exclusion effects in adsorption processes , 1989 .

[31]  Cass T. Miller,et al.  Dissolution of Trapped Nonaqueous Phase Liquids: Mass Transfer Characteristics , 1990 .

[32]  Randel Haverkamp,et al.  A Comparison of Numerical Simulation Models For One-Dimensional Infiltration1 , 1977 .

[33]  J. Saiers,et al.  Transport of silica colloids through unsaturated porous media: experimental results and model comparisons. , 2002, Environmental science & technology.

[34]  M. Corapcioglu,et al.  Effect of colloids on volatile contaminant transport and air‐water partitioning in unsaturated porous media , 1997 .

[35]  Reinder A. Feddes,et al.  Simulation model of the water balance of a cropped soil: SWATRE , 1983 .

[36]  Tetsu K. Tokunaga,et al.  Film Straining of Colloids in Unsaturated Porous Media: Conceptual Model and Experimental Testing , 1997 .

[37]  E. A. Sudicky,et al.  Colloid‐facilitated contaminant transport in discretely fractured porous media: 1. Numerical formulation and sensitivity analysis , 1995 .

[38]  G. Hornberger,et al.  The Role of Colloidal Kaolinite in the Transport of Cesium through Laboratory Sand Columns , 1996 .

[39]  K. Khilar,et al.  Subsurface colloids in groundwater contamination: a mathematical model , 2004 .

[40]  J. McCarthy,et al.  Colloid Transport in the SubsurfacePast, Present, and Future Challenges , 2004 .

[41]  D. K. Smith,et al.  Migration of plutonium in ground water at the Nevada Test Site , 1999, Nature.

[42]  Sujoy B. Roy,et al.  Sorption nonequilibrium effects on colloid-enhanced transport of hydrophobic organic compounds in porous media , 1998 .

[43]  J. Saiers.  Laboratory observations and mathematical modeling of colloid‐facilitated contaminant transport in chemically heterogeneous systems , 2002 .

[44]  J. McCarthy,et al.  ES&T Features: Subsurface transport of contaminants , 1989 .

[45]  Sujoy B. Roy,et al.  Chemical factors influencing colloid-facilitated transport of contaminants in porous media , 1997 .

[46]  John T. Crist,et al.  Pore-Scale Visualization of Colloid Transport and Retention in Partly Saturated Porous Media , 2004 .

[47]  M. Corapcioglu,et al.  Modeling Colloid Transport in Unsaturated Porous Media and Validation with Laboratory Column Data , 1996 .