Friday, 14 July 2006 - 1:45 PM

Pore Space Analysis of Soil Aggregates Investigated by Microtomography Using Synchrotron Radiation.

Stephan Peth1, Rainer Horn1, A.J.M Smucker2, Felix Beckmann3, Tilman Donath3, and J. Fischer4. (1) Institute of Plant Nutrition and Soil Science, CAU Kiel, Hermann-Rodewald-Str. 2, Kiel, 24118, Germany, (2) Department of Crop and Soil Sciences , Michigan State University, PSSB, East Lansing, MI 48824, (3) GKSS-Research Centre, Max-Planck-Str. 1, Geesthacht, 21502, Germany, (4) Hannover Medical School, Anna-von-Borries-Str. 1-7, Hannover, 30625, Germany

Soil structure and particularly the formation of (micro)aggregates are important for long term sequestration of Soil Organic Carbon (SOC). However, research during the last 50 years produced only a few quantitative studies that consider the interactive effects between soil biota and soil physical processes which are especially relevant on the micro-scale. These interactions in turn are primarily dependent on the spatial arrangement of solids and voids since the geometry and continuity of the pore-network within soil aggregates determine the flux of air, water and nutrients and hence control the environment for micro organisms. Advances in synchrotron X-ray tomography and the development of algorithms to quantitatively describe porous media from reconstructed 3D images will greatly facilitate soil structure analysis on the micro-scale. This in turn contributes to understanding the mechanism involved in carbon sequestration within soil intra-aggregate pore space. To provide a statistical analysis of pore geometrical properties pore throat size, channel length and connectivity as well as pore size distributions within aggregates may be useful. Lindquist and Venkatarangan (2000) have developed a suite of algorithms assembled into a software package referred to as 3DMA to extract such geometric property distributions from 3D data sets. The authors investigated the accuracy of their algorithms using a simulated image of packed hexagonal spheres. Relative errors between theoretical and numerically computed values were in general smaller than 5%. Also the analysis of microtomographic images of Fontainebleau sandstone produced good results (Lindquist and Venkatarangan 2000). To test the applicability of above mentioned algorithms for soil aggregates we have analysed a set of soil aggregates approximately 5 mm across at the synchrotron radiation source in Hamburg/Germany (DESY). From the reconstructed 3D images we extracted brick shaped subvolumes which we analysed for pore statistical properties. Potential applications and drawbacks of the applied algorithms will be discussed.

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