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United States Department of Agriculture

Agricultural Research Service


item Pachepsky, Yakov

Submitted to: International Workshop on Fractal Mathematics Describing Soil and Heterogeneous Systems
Publication Type: Abstract Only
Publication Acceptance Date: June 17, 2002
Publication Date: June 28, 2002
Citation: Pachepsky, Y.A. 2002. Mass fractal dimension of shrinking soil aggregates. International Workshop on Fractal Mathematics Describing Soil and Heterogeneous Systems. p.24.

Technical Abstract: Fractal scaling for mass of dry soil aggregates has been documented in literature. This scaling results in power-law dependencies of aggregate porosity or bulk density on aggregate size. Such dependencies if measured are used to estimate mass fractal dimensions. Changes in water content are known to cause shrinking or swelling in aggregates. Therefore, porosity and bulk density change along with the aggregate size as water content changes. The objective of this work was to see (a) whether the fractal scaling will hold for aggregates at various water contents and (b) how mass fractal dimension depends on water content if the fractal scaling holds. Soil samples were taken from several depths in the plow horizon of soddy-podzolic soil. The specific porosity of aggregates was measured with the kerosene method in air-dry aggregates, at saturation, and at two intermediate water contents. The power-law scaling mass=A*(diameter)D was applicable to aggregates from all depths in the range of water contents studies. At saturation, specific porosity did not depend on aggregate size, and D was equal to three for all aggregate size studies. Both the parameter A and the mass fractal dimension D could be approximated well with linear functions of the gravimetric water content. Coefficients of those linear functions depended on aggregate size. The observed scaling can be used to estimate aggregate shrinkage due to drying.

Last Modified: 6/3/2015