Sorption is a process by which chemicals or organisms become attached to soils and/or the geologic rock material (aquifer solids) and removed from the water. Often the sorption process is reversible and solutes desorb and hence dissolved-solute plumes are retarded, rather than solutes being permanently retained by the solids. Cation exchange is the interchange between cations in solution and cations on the surfaces of clay particles or organic colloids. Filtration is a process that affects particulate contaminants (. organig/ inorganic colloids or microbes) rather than dissolved solutes. Particles larger than pore throats diameters or fracture apertures are prevented from moving.
