Evidence in rocks, soil, and water of hydrolysis processes causing sodicity and regressive mortality in arid environments

This work aims to identify the origin of water and soil salinization in an arid area. Sodicity is a type of salinity found in arid or desert soils, influencing soil nutrient loss.

Petrography, mineralogy, X-ray diffraction, and hydrogeochemistry techniques were applied to address water and soil salinity in the arid area of Tierra Nueva. A textural analysis classified the soil types derived from the alteration of the dominant rocks in the region. Hierarchical cluster analysis, principal component analysis, and hydrogeochemistry identified the types of water and the main routes of the water evolutionary processes (dissolution, precipitation, and ion exchange).

The results indicate that salinization can be geogenic and anthropogenic, in the first case, the aquifer composed of igneous rocks of andesitic and rhyolitic composition, release sodium during weathering. Anthropic activities in the region also increase salinization. Three dominant processes were identified: i) where water-rock interaction predominates; (ii) mixing with hydrological influences of irrigation return; (iii) which is affected by ion exchange in the clayey soil and the capillary effect with high evaporation, which subsequently intensifies the salinity of the water and soil in the Tierra Nueva region.

The sodicity levels in water and soil suggest that regressive mortality affects resilient species such as mesquites (Prosopis spp) and huisache (Acacia farnesiana). Due to osmotic stress, these species form nodules and cracks in their stems, leading to regressive mortality.