An overview on source, mechanism and investigation approaches in groundwater salinization studies

Groundwater quality, as major source of freshwater, is an important factor in sustainable development and water resources management. Due to increase in water demand in developing countries and overexploitation, groundwater quality has decreased in many aquifers in the world. One of the most important factors which decrease the groundwater quality is salinization. The aim of this study is to comprehensively review the sources and mechanisms of salinization. Based on our review, the major sources of groundwater salinization consist of marine sources (e.g., connate saline groundwater, marine transgressions, incidental flooding by seawater, lateral seawater intrusion and seawater sprays), natural continental sources (e.g., evaporation, soluble minerals, membrane effects and geothermal origin), anthropogenic activities and multiplicity sources. Research approaches in groundwater salinization include hydrogeochemical and isotopic tracers, hydrogeochemical models and groundwater dating isotopes (radioisotopes). The simple and clear guideline presented in this paper can be applied to investigate the groundwater salinization by researchers in the world.