Multiscaling analysis in a structured clay soil using 2D images

The spatial variability of preferential pathways for water and chemical transport in a field soil, as visualized through dye infiltration experiments, was studied by applying configuration entropy and multifractal analysis. After dye infiltration into a 4 m plot located on a Vertisol soil near College Station, TX, horizontal planes in the subsoil were exposed at 5-cm intervals, and dye stain patterns were photographed. Each of the digitized high-resolution dye images obtained were analysed calculating the maximum configuration entropy (H(L)), the characteristic length (L), and the generalized dimensions (Dq). The results indicate that H(L) and L are two useful descriptors that give an optimal scale of discrimination in the spatial arrangement of the dye tracer at each horizontal section. In addition, L can be used to choose the scale range at which the multifractal analysis should be applied. It has been showed that Dq, being q>0, depend much more on the percentage of black pixels than on the image structure when a box-counting method is used. Finally, a multifractal analysis was applied to maximum dye infiltration depth and amount of dye pixels bellow the area studied, obtained by merging images from the 16 exposed planes. The results show a multiscaling structure and a consistent Dq for both measures. This could be useful for statistically describing preferential flow path geometry and flow processes under field conditions.