X-ray computed microtomography is a non-destructive technique which allows to study in 3D the texture of a solid material and of great interest for non-homogeneous ones. Coupled with image analyses software, the soil properties visually determined can be easily supported by statistics. This work proposes to study the root development of Arabidopsis halleri growing on different soils polluted with metallurgical slag and dredging sludge. The 3D images reveal that the wastes are not homogeneous and pollutants are concentrated in some small regions randomly spread. They often correspond to lead oxide phases in slags and to ore phases as blende in sludge. Their descriptions have also been supported by statistics issued from the image analysis software, Aphelion. Additional result deals with the capacity of X-ray computed microtomography for primary and secondary rhizosphere in situ analysis which can be measured precisely.