Diffusion of humic acid in compacted clay

Clay minerals and organic substances are common components of soils, sediments, and rocks. Little is known, however, on the migration behavior of humic substances in clay formations. Here, we studied the diffusion of humic acid (HA) in clay at different porosities to understand the migration of organic colloids in narrow pore systems.
The migration behavior of HA in compacted clay has to be understood as the diffusion of a size distributed matter, which is affected by filtration effects, size exclusion, the conformity of HA as a function of pH, and probably the distribution of functional groups in the different molecular fractions.