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

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Seyfried, M. S. Articles by Rao, P. S. C. Search for Related Content PubMed Articles by Seyfried, M. S. Articles by Rao, P. S. C. Agricola Articles by Seyfried, M. S. Articles by Rao, P. S. C.

Solute Transport in Undisturbed Columns of an Aggregated Tropical Soil: Preferential Flow Effects¹

ABSTRACT

Solute breakthrough curves (BTC) resulting from miscible displacement of ³H₂O in undisturbed soil columns under a range of soil-water tensions were evaluated in terms of the mobile-immobile (MIM) water model and the convective-dispersive (CD) model. The BTC performed under tensions >0.1 kPa were approximately symmetric in shape and accurately described by the CD model, whereas BTC performed under tensions of 0 or 0.1 kPa were quite asymmetric and better described by the MIM model. Application of tension resulted in about a 10- to 20-fold decrease in hydraulic conductivity [K()] with relatively little change in soil-water content (). Highly asymmetric BTC were attributed to bypassing or preferential flow along macropores. Thus, in terms of model selection, bypassing was significant only when soil-water contents were at or very near saturation. Rhodamine B dye patterns obtained under saturated conditions showed that soil-water flow (and thus convective transport) was confined to small regions within the columns. However, easily identifiable, discrete channels were not observed in these regions. It appears that flow was conducted via a series of relatively large pores, or continuous pore sequences. Application of tension appears to have disconnected the most rapidly conducting pore sequences, thus reducing the asymmetry in measured BTC and compressing the dye "solute front." Even so, dye patterns showed that flow was very heterogeneous, as was also evidenced by high dispersion coefficients in the ³H₂O experiments. Comparison of the frequency distributions of field-measured saturated hydraulic conductivity values and measured rainfall intensities indicated that saturated conditions, and hence significant bypassing, are not expected to occur in this soil under field conditions. Observation of water table response to rainfall events supports this conclusion. From these experiments, we conclude that field-scale models based on the CD model may adequately represent solute movement in soil at this field site.

¹ Approved for publication as Florida Agric. Exp. Stn. Journal Series no. 8104.

² Postdoctoral Research Associate and Professor, respectively, Soil Science Dep., Univ. of Florida, Gainesville, FL 32611. The senior author is now Postdoctoral Research Associate at Plant Science Dep., Univ. of Delaware, Newark, DE 19717.

Received for publication December 3, 1986.

This article has been cited by other articles:

				A. Mayer, T. Sandman, and M. Breidenbach Effect of Flow Regime on Physical Nonequilibrium Transport in Unsaturated Porous Media Vadose Zone J., August 13, 2008; 7(3): 981 - 991. [Abstract] [Full Text] [PDF]

				D. A. Robinson, C. S. Campbell, J. W. Hopmans, B. K. Hornbuckle, S. B. Jones, R. Knight, F. Ogden, J. Selker, and O. Wendroth Soil Moisture Measurement for Ecological and Hydrological Watershed-Scale Observatories: A Review Vadose Zone J., February 25, 2008; 7(1): 358 - 389. [Abstract] [Full Text] [PDF]

				P. M. Jardine, M. A. Mayes, P. J. Mulholland, P. J. Hanson, J. R. Tarver, R. J. Luxmoore, J. F. McCarthy, and G. V. Wilson Vadose Zone Flow and Transport of Dissolved Organic Carbon at Multiple Scales in Humid Regimes Vadose Zone J., March 8, 2006; 5(1): 140 - 152. [Abstract] [Full Text] [PDF]

				K.-J. S. Kung, M. Hanke, C. S. Helling, E. J. Kladivko, T. J. Gish, T. S. Steenhuis, and D. B. Jaynes Quantifying Pore-Size Spectrum of Macropore-Type Preferential Pathways Soil Sci. Soc. Am. J., June 28, 2005; 69(4): 1196 - 1208. [Abstract] [Full Text] [PDF]

				C. Kjaergaard, T. G. Poulsen, P. Moldrup, and L. W. de Jonge Colloid Mobilization and Transport in Undisturbed Soil Columns. I. Pore Structure Characterization and Tritium Transport Vadose Zone J., May 1, 2004; 3(2): 413 - 423. [Abstract] [Full Text] [PDF]

				J. M. Hutchison, J. M. Hutchison, J. C. Seaman, S. A. Aburime, and D. E. Radcliffe Chromate Transport and Retention in Variably Saturated Soil Columns Vadose Zone J., November 1, 2003; 2(4): 702 - 714. [Abstract] [Full Text] [PDF]

				G. N. Magesan, I. Vogeler, B. E. Clothier, S. R. Green, and R. Lee Solute Movement through an Allophanic Soil J. Environ. Qual., November 1, 2003; 32(6): 2325 - 2333. [Abstract] [Full Text] [PDF]

				S. Roulier and N. Jarvis Modeling Macropore Flow Effects on Pesticide Leaching: Inverse Parameter Estimation Using Microlysimeters J. Environ. Qual., November 1, 2003; 32(6): 2341 - 2353. [Abstract] [Full Text] [PDF]

				L. A. Gaston, D. J. Boquet, and M. A. Bosch Fluometuron Sorption and Degradation in Cores of Silt Loam Soil from Different Tillage and Cover Crop Systems Soil Sci. Soc. Am. J., May 1, 2003; 67(3): 747 - 755. [Abstract] [Full Text] [PDF]

				M. K. Shukla, F. J. Kastanek, and D. R. Nielsen Inspectional Analysis of Convective-Dispersion Equation and Application on Measured Breakthrough Curves Soil Sci. Soc. Am. J., July 1, 2002; 66(4): 1087 - 1094. [Abstract] [Full Text] [PDF]

				S. D. Logsdon, K. E. Keller, and T. B. Moorman Measured and Predicted Solute Leaching from Multiple Undisturbed Soil Columns Soil Sci. Soc. Am. J., May 1, 2002; 66(3): 686 - 695. [Abstract] [Full Text] [PDF]

				E. Perfect, M. C. Sukop, and G. R. Haszler Prediction of Dispersivity for Undisturbed Soil Columns from Water Retention Parameters Soil Sci. Soc. Am. J., May 1, 2002; 66(3): 696 - 701. [Abstract] [Full Text] [PDF]

				J. Vanderborght, P. Gahwiller, and H. Fluhler Identification of Transport Processes in Soil Cores Using Fluorescent Tracers Soil Sci. Soc. Am. J., May 1, 2002; 66(3): 774 - 787. [Abstract] [Full Text] [PDF]

				R. W. Vervoort, S. M. Dabney, and M. J. M. Romkens Tillage and Row Position Effects on Water and Solute Infiltration Characteristics Soil Sci. Soc. Am. J., July 1, 2001; 65(4): 1227 - 1234. [Abstract] [Full Text] [PDF]

				Y. Pachepsky, D. Benson, and W. Rawls Simulating Scale-Dependent Solute Transport in Soils with the Fractional Advective-Dispersive Equation Soil Sci. Soc. Am. J., July 1, 2000; 64(4): 1234 - 1243. [Abstract] [Full Text]

				L. Bejat, E. Perfect, V.L. Quisenberry, M.S. Coyne, and G.R. Haszler Solute Transport as Related to Soil Structure in Unsaturated Intact Soil Blocks Soil Sci. Soc. Am. J., May 1, 2000; 64(3): 818 - 826. [Abstract] [Full Text]

				H.W. Langner, H.M. Gaber, J.M. Wraith, B. Huwe, and W.P. Inskeep Preferential Flow through Intact Soil Cores: Effects of Matric Head Soil Sci. Soc. Am. J., November 1, 1999; 63(6): 1591 - 1598. [Abstract] [Full Text] [PDF]