Abstract
Authors developed some contrast media for researching the spatial continuity of void in the soils. The continuous void images were photographed by soft X-ray projection after the contrast medium infiltrated in the soils.
The developed contrast media were the following heavy liquids:
Diiodomethane (C medium), Tribromomethane (D medium) and 1, 1, 2, 2-Tetrabromoethane (Emedium).
C and E medium were preferable to D medium (Photo. 1).
In X-ray images, fine pores diameters up to 25μm size could be observed.
The way of photographing X-ray images after infiltration of the heavy liquid in objective was named the “Heavy Liquid Infiltration method”.
The sample soils were the volcanic ash soil from the foot of Mt. Iwate. Pores formed by plant roots were obvious in void images on grass land root zone soil photographed by H. L. I. method. In unplowed sub-soil layer too, the forms of root system remained in detail as micropores. Therefore, the pores formed by plant roots were not only macropores but also micropores (Photos 2-6).
The size of the root bodies found in the sample soils were about 100μm or more in diameter and their total volume was about 10% or less for the volume of noncapillary pores (φ>100μm) in the sample. Therefore, it was evident that the fine funicular images are almost empty capillary pores. So the authors called them the “root formed pores” and presumed that the most fine pores were formed by the root hairs having a size of about 10μm in diameter (Photos 7-9).
The considerations on the root formed pores were as follows;
(1) The capillary net shape of root formed pores is consisted of connectivity between some root systems.
(2) Root formed poresh ave tbe function of percolation and moistu reretention. The energy of retention will reach pF 2.5 (equivalellt diameter is about 10μm).
