A morphological approach to understanding preferential flow using image analysis with dye tracers and X-ray Computed Tomography

Abstract A key problem facing soil physics and hydropedology at present is some of the standard theories of water flow in soils do not fully reflect the processes at the pore scale, and thus, cannot be adequately used for prediction. As such, examination of soil structure is vital for hydropedologists. Realisation that solutes move preferentially through soil into groundwaters has meant research in this area has increased in importance. This paper describes a multi-scale approach to analyse transport mechanisms using visualisation techniques. Chloride and Brilliant Blue tracers were applied to undisturbed soil cores to examine the physical and morphological properties associated with preferential flow in a range of soil types. Following collection of serial digital images, it was possible to examine and quantify the nature of active water flow mechanisms in terms of both dye-stained pathways and spatial distribution of dye concentration, using image analysis. Preferential flow linked to water potential and soil structural discontinuity was observed in all but the coarsest textured soil which conformed to uniform flow theory. A high level of variability in flow patterns was noted between the soil types. Such information as to how a soil dynamically re-wets is key for hydropedologists involved in applications such as pollution modelling. This is especially significant when considering a wetting mechanism, such as preferential flow, that cannot be adequately described by conventional soil physics.

[1]  H. Flühler,et al.  Image Analysis for Determination of Dye Tracer Concentrations in Sand Columns , 1997 .

[2]  Coen J. Ritsema,et al.  How water moves in a water repellent sandy soil: 1. Potential and actual water repellency , 1994 .

[3]  Hans-Jörg Vogel,et al.  A new approach for determining effective soil hydraulic functions , 1998 .

[4]  Hans-Jörg Vogel,et al.  The dominant role of structure for solute transport in soil: Experimental evidence and modelling of structure and transport in a field experiment , 2005 .

[5]  N. Jarvis.  Simulation of soil water dynamics and herbicide persistence in a silt loam soil using the MACRO model , 1995 .

[6]  I M Young,et al.  Interactions and Self-Organization in the Soil-Microbe Complex , 2004, Science.

[7]  Hannes Flühler,et al.  Quantifying dye tracers in soil profiles by image processing , 2000 .

[8]  Hannes Flühler,et al.  SUSCEPTIBILITY OF SOILS TO PREFERENTIAL FLOW OF WATER : A FIELD STUDY , 1994 .

[9]  I. Forrer.  Solute transport in an unsaturated field soil , 1997 .

[10]  R. E. Phillips,et al.  Spatial Distribution of Water and Chloride Macropore Flow in a Well-Structured Soil , 1994 .

[11]  John W. Crawford,et al.  Determination of soil hydraulic conductivity with the lattice Boltzmann method and soil thin-section technique , 2005 .

[12]  J. Feyen,et al.  Modelling Water Flow and Solute Transport in Heterogeneous Soils: A Review of Recent Approaches☆ , 1998 .

[13]  Henry Lin,et al.  Advancing the frontiers of soil science towards a geoscience , 2006 .

[14]  Hannes Flühler,et al.  Inferring flow types from dye patterns in macroporous soils , 2004 .

[15]  K. Beven,et al.  Macropores and water flow in soils , 1982 .

[16]  Johan Bouma,et al.  Hydropedology as a powerful tool for environmental policy research , 2006 .

[17]  J. Bouma,et al.  The Function of Different Types of Macropores During Saturated Flow through Four Swelling Soil Horizons1 , 1977 .

[18]  R. Wagenet,et al.  A Multiregion Model Describing Water Flow and Solute Transport in Heterogeneous Soils , 1995 .

[19]  Catherine S. Morris,et al.  VISUALIZATION AND QUANTIFICATION OF THE EFFECTS OF CEREAL ROOT LODGING ON THREE-DIMENSIONAL SOIL MACROSTRUCTURE USING X-RAY COMPUTED TOMOGRAPHY , 2006 .

[20]  S. O. Prasher,et al.  Three‐Dimensional Quantification of Macropore Networks in Undisturbed Soil Cores , 1999 .

[21]  Catherine S. Morris,et al.  A high-resolution system for the quantification of preferential flow in undisturbed soil using observations of tracers , 2004 .

[22]  S. Meyer-Windel,et al.  Adsorption of brilliant blue FCF by soils , 1999 .

[23]  J. Bouma,et al.  Parameters for describing soil macroporosity derived from staining patterns , 1998 .

[24]  Yakov A. Pachepsky,et al.  Revitalizing pedology through hydrology and connecting hydrology to pedology , 2006 .

[25]  J. Bouma,et al.  Estimation of the moisture supply capacity of some swelling clay soils in The Netherlands , 1981 .