Chemical and mineralogical characteristics of tropical soils on the transport of Na ⁺ , K ⁺ , Ca ²⁺ , and Mg ²⁺ from the application of treated wastewater

With the search for water security, the reuse of water in irrigation becomes interesting and inevitable. Given the complexity of soil-solute interactions, the use of simplified artificial solutions represents an innovative approach, as it facilitates understanding these interactions while posing no risk to human health or the environment. However, the more complex and inferior the quality of the water, the greater the environmental contamination risk. The objective of this study was to investigate ion retention in three tropical soils (Oxisol, Inceptisol, and Entisol Quartzipsamment) by applying treated domestic wastewater (TWW) and artificial wastewater, both with the same concentrations of Na⁺, K⁺, Ca²⁺, and Mg²⁺ as the TWW. Physical, chemical, and mineralogical properties of the soil were determined. Multivariate analysis was performed to elucidate the relationships between the solutes' transport parameters, the soils' mineralogy and texture, and the variation in their chemical characteristics resulting from wastewater application. Oxisol and Entisol Quartzipsamment contributed to principal component 1. The second principal component had a negative contribution from Inceptisol. Oxisol and Entisol Quartzipsamment showed the longest delays of ion transport relative to the wetting front. Inceptisol had the lowest retardation factors and the lowest affinity for ions. For the TWW on Oxisol, Na⁺ was the first ion to reach a relative concentration equal to 1, at an average pore volume of 4.3; however, the last pore volume collected for Ca²⁺ was 12.3, with a relative concentration of 0.6, showing that sodium in TWW is a point of attention, as observed by the low affinity with soils.