(1)*Centro Nacional de Termalismo "Víctor Santamarina". Ave. 243 No. 19815 Fontanar, La Habana, Cuba. firstname.lastname@example.org. Tel-FAX. 53-7-453599.
(2)Universidad de Huelva, España.
The hydrogeochemical processes which determine the chemical composition or water from different hydrogeological zones at the karstic aquifer of Güira-Quivicán (Havana Southern Basin) were identified by means of a systematic field and laboratory sampling program. Among them the main processes were: sulfide and organic matter oxidation at the unsaturated zone of the aquifer; sulfate anaerobic reduction, especially at the middle ad deep level of the walls located near of the swamp; dissolution and precipitation of calcite and dolomite, direct and inverse ion exchange, as well as other processes connected with the fresh – sea water mixture, where significant modification processes of the chemical composition occurs, which are demonstrated comparing the data with the conservative mixture results.