Representative Elementary Volume for Pore System Geometry Parameters Determined from 3D X-Ray Images.

Microtomography is a non-destructive technique resulting in a high-resolution description of pore space geometry and fluid distribution including pore size distribution, shape, connectivity, tortuosity and orientation. 3D microtomography images request an acquisition time for obtaining the image, processing and analysis. In order to optimize file size and reduce computational requirements, the determination of the Representative Elementary Volume (REV) of 3D microtomography images is important. We determined the REV related to four parameters (which parameters) in four tropical soils from Brazil using 3D X-ray microtomography images with spatial resolution of 40 μm. Large undisturbed soil samples (height 7.5 cm Diameter 7.5 cm) were collected in PVC rings. The 3D X-ray microtomography images were obtained with a Nikon XT H 225 CT system and software CT Pro 3D (Nikon) was used to reconstruct the image. Image processing was performed using the FIJI/Image J software in subsamples of different sizes (from 7,912.70 mm³ to 14.83 mm³). For each size, the standard deviation of the obtained values was obtained. The REV was determined as the smallest size corresponding to a low standard deviation.