THE CHARACTERIZATION OF SOIL MACROPOROSITY WITH CT SCANNING

Abstract

The soil macropore system was analyzed with the help of image analysis, comparing images from computed-tomography (CT) scanning with images obtained from thin sections. The images obtained with the two methods were analyzed with an image analyzer (IBAS 2000) for various pore characteristics. Macroporosity measurements obtained with CT scanning were comparable with those obtained with thin section. Computed-tomography scanning of soil cores which had been impregnated with styrene resin revealed a decreased level of soil macroporosity, in particular of planar macroporosity, as compared to nonimpregnated soil cores. CT scanning provided a useful method in characterizing a compacted soil layer. Through three-dimensional analysis of the CT scans, boundaries of compacted soil layers could be identified to the nearest 1 mm. The advantages of this method are that it is nondestructive, and fast, images can be made at 1-mm intervals, and it has the capability for three-dimensional images. However, resolution is limited to pores larger than 750 μm. Key words: Soil porosity, image analysis, thin sections, CT scanning