ABSTRACT
Considering subsurface water a complex solution, mass transfer in aquifers can be determined as a directed change of the matter composition and quantity of the constituents. Mass transfer in aquifers is termed migration of subsurface waters. In this regard it is expedient to use the concept of hydrogeochemical migration as a synonym for mass transfer in subsurface waters. A quantitative study of hydrogeochemical migration is based on the methods of physicochemical thermodynamics and mathematical applications developed in the theory of heat and mass transfer. The hydrodynamic series of problems of mass and heat transfer are solved in the same manner in which they are expressed, by identical mathematical equations even though they physically differ. In some publications heat transfer is included under migration of subsurface waters. The geological medium is a complex system in which the skeletal rocks form the immobile phase and the liquid, gaseous and biological, the mobile, shifting phases. In palaeohydrogeological problems all phases are considered mobile.
