Environmental Scanning Electron Microscopy Application for Brackish Water Irrigation Impact on Soil

Abstract

Core Ideas Long‐term irrigation with brackish water can extend the practice into water‐scarce regions. ESEM in both dynamic and static modes is a promising technique to analyze soil impacts. Changes linked to the hydrophilic behavior of soils can be detected. We investigated soil response to irrigation with slightly brackish water (1200 mg L−1 total dissolved solids on average) in a semiarid environment at the microscopic scale using environmental scanning electron microscopy (ESEM) applied in static and dynamic modes, which allowed comparison between nonirrigated and 3‐yr‐irrigated soil samples to determine the impact of applied brackish water. Results indicate that (i) there was a change in soil hydrophilic behavior by the continuous accumulation of water‐borne salt in the soil matrix, (ii) compared with nonirrigated samples, the wetting process occurred more gradually for the 3‐yr‐irrigated sample, (iii) the wetting process started at a lower vapor pressure for the 3‐yr‐irrigated sample, (iv) water vapor pressure in the chamber at full saturation was lower for the 3‐yr‐irrigated sample, and (v) the presence of heavy metals in the soil was more frequent in irrigated samples. Our results show that ESEM is a useful technique to determine the impacts on soil of irrigation with slightly brackish water.