Effects of CT number derived matrix density on preferential flow and transport in a macroporous agricultural soil

Preferential flow and transport in structured soils can be intimately linked to numerous environmental problems. Surface-applied chemicals are susceptible to rapid transport to deeper depths in structural soil pores, thereby potentially contaminating valuable environmental resources and posing risks...

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Published inVadose zone journal Vol. 14; no. 7; pp. 1 - 13
Main Authors Katuwal, Sheela, Moldrup, Per, Lamande, Mathieu, Tuller, Markus, de Jonge, Lis Wollesen
Format Journal Article
LanguageEnglish
Published Soil Science Society of America 01.07.2015
The Soil Science Society of America, Inc
Subjects
agriculture
Argiudolls
computed tomography data
cores
Denmark
density
Europe
Faardrup Denmark
fluid flow
Hapludolls
image analysis
Mollisols
permeability
porosity
preferential flow
Scandinavia
segmentation
size
Sjaelland
soils
solute transport
transport
unsaturated zone
Vermudolls
Western Europe
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Summary:Preferential flow and transport in structured soils can be intimately linked to numerous environmental problems. Surface-applied chemicals are susceptible to rapid transport to deeper depths in structural soil pores, thereby potentially contaminating valuable environmental resources and posing risks to public health. This study focused on establishing links between the structural pore space and preferential transport using a combination of standard physical measurement methods for air and water permeabilities, breakthrough experiments, and X-ray computed tomography (CT) on large soil columns. Substantial structural heterogeneity that resulted in significant variations in flow and tracer transport was observed, despite the textural similarity of the investigated samples. Quantification of macropore characteristics with X-ray CT was useful but not sufficient to explain the variability in air permeability, saturated hydraulic conductivity, and solute transport. This was due to the limited CT scan resolution and large structural variability below this resolution. However, CTmatrix, a new parameter derived from the CT number of the matrix excluding stones and large mostly air-filled macropores, was found to be useful for determining the magnitude of preferential flow under boundary conditions of constant, near-saturated flow.
Bibliography:All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher.
A new parameter for representing the matrix bulk density, computed tomography (CT) number derived matrix density, was used in studying preferential flow and transport in an agricultural soil. Results illustrate that CT number derived matrix density provides useful information regarding the initiation of macropore flow and the magnitude of preferential flow.
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ISSN:1539-1663
1539-1663
DOI:10.2136/vzj2015.01.0002