HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Figures Only Full Text Free Full Text (PDF) Free Supplemental Videos Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in ISI Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (23) Citing Articles via Google Scholar Google Scholar Articles by Crist, J. T. Articles by Steenhuis, T. S. Search for Related Content PubMed Articles by Crist, J. T. Articles by Steenhuis, T. S. GeoRef GeoRef Citation Agricola Articles by Crist, J. T. Articles by Steenhuis, T. S. Related Collections Vadose Zone Processes and Chemical Transport Colloids Pore-Scale Modeling

ORIGINAL RESEARCH

Transport and Retention Mechanisms of Colloids in Partially Saturated Porous Media

^a Department of Biological and Environmental Engineering, Riley-Robb Hall, Cornell University, Ithaca, NY 14853
^b Department of Earth and Planetary Sciences, University of Tennessee, Knoxville, TN 37996
^* Corresponding author (tss1{at}cornell.edu)

Received 29 January 2004.

The transport, retention, and release of hydrophobic and hydrophilic polystyrene latex microsphere colloids were examined in 0.5-cm-thick, 26-cm-long slab chambers filled with either regular (hydrophilic) or weakly water-repellent sand. The water-repellent sand consisted of a mixture of 0.4% strongly water-repellent grains with unmodified regular sand for the remainder. The concentration of colloids in the outflow water was measured at the same time as the pore-scale distribution of colloids was recorded in still and video images. Although the type of sand affected the flow pattern in the top of the chamber, it did not affect the breakthrough for the same type of colloids. More hydrophilic colloids were eluted in the drainage water than hydrophobic colloids. Images showed that there was a greater retention of the hydrophobic colloids due to strongly attractive hydrophobic interaction forces between colloids and subsequent filtering of colloidal aggregates in the narrow passages between grains. Once filtered, these aggregates then served as preferred sites for attachment of other hydrophobic colloids. The hydrophilic colloids were retained primarily in a thin film of water at the edge of the menisci, the air–water–solid (AWS) interface. Centrifugal motion within the pendular rings observed in the videos contributed to movement of the colloids toward the AWS interface, where colloids were retained due to both low laminar flow velocities near the grain surface and straining in the thin water film at the edge of the meniscus. Except near the solid interface, sorption at the air–water (AW) interface was not observed and appeared unimportant to the retention of colloids. The findings form an essential link between colloid retention and transport processes at the interfacial, pore, and Darcy scales.

Abbreviations: AW, air–water • AWS, air–water–solid • BTC, breakthrough curve • DLVO, Derjaguin–Landau–Verwey–Overbeek forces • PV, pore volume • SW, soil–water • 2D, distilled–deionized

This article has been cited by other articles:

				S. A. Bradford and S. Torkzaban Colloid Transport and Retention in Unsaturated Porous Media: A Review of Interface-, Collector-, and Pore-Scale Processes and Models Vadose Zone J., May 27, 2008; 7(2): 667 - 681. [Abstract] [Full Text] [PDF]

				M. Flury and H. Qiu Modeling Colloid-Facilitated Contaminant Transport in the Vadose Zone Vadose Zone J., May 27, 2008; 7(2): 682 - 697. [Abstract] [Full Text] [PDF]

				G. Gargiulo, S. A. Bradford, J. Simunek, P. Ustohal, H. Vereecken, and E. Klumpp Bacteria Transport and Deposition under Unsaturated Flow Conditions: The Role of Water Content and Bacteria Surface Hydrophobicity Vadose Zone J., May 1, 2008; 7(2): 406 - 419. [Abstract] [Full Text] [PDF]

				S. Torkzaban, S. M. Hassanizadeh, J. F. Schijven, H. A. M. de Bruin, and A. M. de Roda Husman Virus Transport in Saturated and Unsaturated Sand Columns Vadose Zone J., July 26, 2006; 5(3): 877 - 885. [Abstract] [Full Text] [PDF]

				J. Wan and T. K. Tokunaga Comments on "Pore-Scale Visualization of Colloid Transport and Retention in Partly Saturated Porous Media" Vadose Zone J., October 10, 2005; 4(4): 954 - 956. [Full Text] [PDF]

				T. S. Steenhuis, J. F. McCarthy, J. T. Crist, Y. Zevi, P. C. Baveye, J. A. Throop, R. L. Fehrman, A. Dathe, and B. K. Richards Reply to "Comments on 'Pore-Scale Visualization of Colloid Transport and Retention in Partly Saturated Porous Media'" Vadose Zone J., October 10, 2005; 4(4): 957 - 958. [Full Text] [PDF]