Dynamics of Ions in Soils Irrigated with Saline Reject

The objective of this work was to evaluate the variation in the electrical conductivity and the mobilization of ions present in reject brine from desalination plant of brackish well water in three types of soil. The mobilization of the contaminant ions in the reject brine was studied in glass percolation columns, which were filled with soil of contrasting textures (eutrophic CAMBISOL, typic dystrophic Red OXISOL, ENTISOL Quartzipsamment). Experiments ware repeated three times each, and the initial and final concentrations of the ion contaminants were analyzed. The pollution potential of this residue was determined by the retardation factor and dispersion-diffusion coefficient of Ca and Mg, besides the variation of electrical conductivity along the profile of each soil studied. In the Red Oxisol, Ca and Mg ions move with greater ease resulting in possibility largest of potential of ground water contamination. In Entisol Quartzipsamment presented higher Mg (R) ion advancement speed, that is, higher subsurface contamination power for these ions. The eutrophic Cambisol presented low diffusion-dispersion coefficient in all the evaluated ions and, therefore, lower mobility of the ions in the soil profile, and consequently, a greater possibility of contamination when irrigated with reject brine.


Introduction
The rational use of water in irrigated agriculture has been a recurrent discussion along the last decades, especially with respect to water quality (Ayers & Westcot, 1999;Silva et al., 2007;Anami et al., 2008).The use of water with high contents of salts results in the salinization of agricultural soils, causing disorders of physical and chemical nature in these soils, besides limiting crop development (Miranda et al., 2011;Mesquita et al., 2015;Sá et al., 2015).Since the water in some wells has high content of salts, desalinators have become necessary to make its use viable, and reverse osmosis desalination is one of the most employed techniques in arid and semi-arid regions (Santos et al., 2010a;Cosme et al., 2011;Oliveira et al., 2016).Brackish water desalination through reverse osmosis allows the use of water for human consumption and agriculture.However, besides purified water, this process generates saline waste with high potential of soil salinization, which requires adequate disposal (Santos et al., 2011).In general, the final disposal of the saline waste in the soil results in its salinization, thus compromising its chemical and physical quality.In this context, this waste poorly managed in agriculture may pose risks to the environment, promoting soil salinization and reduction of agricultural production (Garcia et al., 2008;Dias et al., 2010;Santos et al., 2011).
The percolation column is a tool used to simulate the behavior of solute movement through the soil.It is based on the principle of accommodation of previously treated soil with well-known physical characteristics, followed by the application of the solution to be studied in the soil, with subsequent infiltration, and the collection of the predetermined pore volumes.Importantly, the dimensions of the column are measured in order to calculate the pore volume to be collected (Silva et al., 2012;Matos et al., 2013;Pinho et al., 2014;Silva et al., 2016).
Given the extreme im addition, th Therefore, calcium (C three types
The reject brine sampling was taken in the Boa Fé rural community in Mossoró, Rio Grande do Norte State, Brazil.This community has a desalination plant by reverse osmosis that provides treated water to the population and, as a result of the desalination process, also generates reject brine.
According to the EC w data, the water is highly brackish (EC w = 10.15 dS m -1 ), and it appears, according to the guidelines proposed by Ayers and Westcot (1999), that the reject brine have a severe use restrictions due to salinity risks (EC w > 3.00 dS m -1 ).Additionally, according to the same authors, the chloride ion has a severe degree of restriction (Cl -> 10 mmol c L -1 ). jas.ccsenet.s.),A

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Figure 4. E

Table 3 .
Characterization of soil chemical properties

Table 4 .
Reject brine chemical analysis