Origin of salinity in soil and water based on hydrogeochemistry and environmental isotopes in the Santa María Volcanic Field

Abstract Salinization of soils and groundwater can be of natural or anthropogenic origin throughout the world. This process is found in arid or desert soils and influences the loss of nutrients in the soil, resulting in the decline of vegetation. Salinization of soils and groundwater in the Tierra Nueva aquifer can be influenced by natural or anthropogenic activities. The aquifer is located in the Santa María Volcanic Field (SMVF). The SMVF is mainly made up of igneous rocks of andesitic and rhyolitic composition. In this work, an exhaustive study has been carried out to discover the origin of salinity through petrography, mineralogy, stable isotopes (δ2H and δ18O) and hydrogeochemistry. Applying hydrogeochemical techniques, the water families and the main routes of the evolutionary processes of water (dissolution and precipitation and ion exchange) were identified. With a textural analysis, the soil types derived from the alteration of dominant rocks in the region were classified. The isotopic results revealed the evaporation and mixing processes, as well as the possible elevations of the recharge and influence of the surface water body on the aquifer. The results indicate that salinization is of natural origin and is increased by anthropogenic activities in the region. Based on the results, three dominant groups were identified, such as (i) where the water-rock interaction process predominates, (ii) the mixing with urban water influences, and (iii) it is affected by the return of irrigation and evaporation, which subsequently intensifies the salinity of the water and soil in the Tierra Nueva region.