Sulfate Saline Research Articles

Progressive failure of frozen sodium sulfate saline sandy soil under uniaxial compression

The progressive failure characteristics of geomaterial are a remarkable and challenging topic in geotechnical engineering. To study the effect of salt content and temperature on the progressive failure characteristics of frozen sodium sulfate saline sandy soil, a series of uniaxial compression tests were performed by integrating digital image correlation (DIC) technology into the testing apparatus. The evolution law of the uniaxial compression strength (UCS), the failure strain, and the formation of the shear band of the frozen sodium sulfate saline sandy soil were analyzed. The test results show that within the scope of this study, with the increase of salt content, both the UCS and the shear band angle initially decrease with increasing salt content before showing an increase. In contrast, the failure strain and the width of the shear band exhibit an initial increase followed by a decrease in the samples. In addition, to investigate the brittle failure characteristics of frozen sodium sulfate saline sandy soil, two classic brittleness evaluation methods were employed to quantitatively assess the brittleness level for the soil samples. The findings suggest that the failure characteristics under all test conditions in this study belong to the transition stage between brittle and ductile, indicating that frozen sodium sulfate saline sandy soil exhibits certain brittle behavior under uniaxial compression conditions, and the brittleness index basically decreases and then increases with the rise in salt content.

Study of Heat–Mass Transfer and Salt–Frost Expansion Mechanism of Sulfate Saline Soil during the Unidirectional Freezing Process

Study of Heat–Mass Transfer and Salt–Frost Expansion Mechanism of Sulfate Saline Soil during the Unidirectional Freezing Process

Insight into simultaneous urea hydrolysis and total nitrogen removal in textile printing wastewater: Focus on the impact of sodium sulfate salinity

The textile printing industry discharges large volumes of effluent containing high concentrations of urea and nitrogenous compounds. Anoxic-oxic (AO) treatment is a promising method for treating printing wastewater. However, the effect of sodium sulfate (Na2SO4) salinity on the urea hydrolysis and nitrogen removal simultaneously in the AO process has received little attention. In this study, five batch reactors were used to treat synthetic printing wastewater with high urea and nitrogen concentrations. A strategy was applied to increase the Na2SO4 concentration from 0 to 19 g/L in the anoxic stage of each reactor. The effect of Na2SO4 on urea hydrolysis, total nitrogen removal and COD removal, sludge characteristics, and bacterial community structure were investigated. The findings showed that urea hydrolysis increased with increasing Na2SO4 concentration. The main mechanism of urea removal was intracellular hydrolysis, with a urea removal efficiency (URE%) of approximately 98% in all batch reactors. In addition, under the stress of Na2SO4, the total nitrogen and COD removal performances were partially inhibited. The most significant removal performances after AO treatment were observed at 0 g/L Na2SO4, with nitrogen and COD removal efficiencies of 88% and 95%, respectively. When Na2SO4 concentration reached 19 g/L, the sludge settling performance and compactness were enhanced. The extracellular polymeric substance (EPS) components in the sludge were dependent on their ability of removing organics. Bacterial community diversity analysis revealed that the enrichment of the Proteobacteria, Firmicutes, and Gemmatimonadota phyla in the anoxic stages of batch reactors was related to intracellular urea hydrolysis. Bacteriodota and Chloroflexi were responsible for total nitrogen removal in all anoxic and oxic stages. This research will develop the understanding of Na2SO4 salinity impact on simultaneous urea hydrolysis and nitrogen removal during AO treatment process.

Study on Strength Characteristics of Sodium Sulfate Saline Sand Based on Homogenization Theory

Study on Strength Characteristics of Sodium Sulfate Saline Sand Based on Homogenization Theory

Research on Solidification Methods and Stabilization Mechanisms of Sulfate Saline Soils

In cold regions, saline soils can cause dissolution, settlement, and salt expansion of the roadbed under the influence of freeze–thaw cycles, so they need to be stabilized during road construction. In this study, lime, fly ash (FA), and polyacrylamide (PAM) were used to stabilize sulfate saline soils, and the stabilized saline soils were subjected to the unconfined compressive strength test (UCS), splitting test, and freeze–thaw cycle tests (FTs). The stabilization mechanism of the three materials on saline soils was also studied via scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TG), and X-ray photoelectron spectroscopy (XPS). The test results showed that the addition of lime, FA, and PAM to saline soils can improve the mechanical properties and frost resistance of saline soils. After 28 d of curing, the UCS of FA-, PAM-, and lime-stabilized saline soils increased by at least 55%, 23%, and 1068%, respectively, and the splitting strength increased by at least 161%, 75%, and 2720%, respectively. After five freeze–thaw cycles, the residual strength ratios (BDRs) of the UCS of L2 (lime 8%), F2 (FA 11%), and P2 (PAM 1%) stabilized soils and saline soils were 71.78%, 56.42%, 39.05%, and 17.95%, respectively, and the decreasing trend tended to be stable. The saline soils stabilized by lime and FA were chemically stabilized, and their mechanical properties and frost resistance were better than the physical stabilization of PAM.

Study on the hydro-thermal-salt-mechanical coupling characteristics of sulfate saline soil under freeze-thaw cycles

The theoretical and experimental studies have been carried out on the water and salt migration and deformation characteristics of sulfate saline soil during freeze-thaw cycles. Based on the theory of unsaturated soil mechanics and the thermoelastic continuum and considering the influence of phase change within the pore on thermodynamic and hydrodynamic parameters, the multi-physical fields coupled model of hydro-thermal-salt-mechanical in unsaturated sulfate saline soil has been established. The variation processes of the temperature field, water field, salt field, and stress field of the soil during freeze-thaw cycles were analyzed, and the validity of the theoretical model was verified by indoor experiments. The results show that there are significant attenuation and hysteresis effects when heat is transferred in the soil during freeze-thaw cycles. The water content of migration in the soil increases with the height of the soil column, while the increment of migration water content decreases with the number of freeze-thaw cycles. The formation and dissolution of salt crystals from top to bottom and the sudden increase in the salt crystallization rate are mainly caused by variations in the solubility of the salt solutions due to temperature changes. The formation and dissolution of ice and salt crystals in the soil induce expansion and contraction, and the freeze-thaw cycle conditions have a significant effect on the expansion and residual deformation of the soil.

Water–salt migration and deformation characteristics in gravelly sulfate saline soil under the effect of localized fine sand accumulation

The water-salt migration law and deformation characteristics of coarse-grained saline soils have been extensively studied and illustrated. However, owing to the influence of the chemical composition and physical properties of the soils, coarse-grained soils are prone to localized soil absorption during mixing and compaction. This type of working condition of the existing localized fine sand accumulation layers is seldom discussed in the literature. In this study, water-salt migration and deformation of natural gradation specimens and specimens with localized fine sand accumulation layers in natural gradation were monitored and detected for the field fill conditions in an airport embankment project using self-designed test equipment based on nine freeze–thaw cycle physical simulation tests at environmental temperatures ranging from −30 °C to 25 °C. Under the freeze–thaw cycle, compared with the natural gradation, the specimens with localized fine sand accumulation layers had a higher influence on water and salt migration, which indicates that the depth range of drastic changes in water and salt increased by 80% and 84%, respectively. The cumulative deformation curves under the effects of natural gradation and localized fine sand accumulation exhibited similar trends. The difference between the deformation of the natural samples and samples with localized fine sand accumulation layers was 16% when the salt content of the upper part of the roadbed was 0.3%. In addition, the cumulative vertical settlement deformation of the specimens decreased with an increase in the salt content of the upper part of the roadbed and gradually transformed into vertical uplift deformation. The results of this study provide a basis for the selection of materials for airport roadbed backfill and their application in construction in seasonally frozen areas.

Solidification of sodium sulfate saline loess by biomineralization of reactive magnesium oxide binder

This study aims to solidify sodium sulfate saline loess by biomineralization of reactive magnesium oxide (MgO) binder. The impact of Na2SO4 concentration on the viability and urease activity of S. pasteurii, the mechanism and products of biomineralization of MgO, and the effectiveness of the biomineralization-MgO binder in solidifying saline loess with varying salt content (1%, 3%, and 5%) were investigated. Results showed that low and moderate concentrations of Na2SO4 favored bacterial proliferation. However, the presence of Na2SO4 inhibited bacterial urease activity, and the inhibition was more significant at higher Na2SO4 concentrations. In addition, low and moderate concentrations of Na2SO4 decreased the specific urease activity, whereas high concentrations of Na2SO4 significantly increased specific urease activity. S. pasteurii was able to use carbonate ions formed by urea hydrolysis for the mineralization of MgO and to form magnesium carbonate minerals dominated by rosette-like dypingite and hydromagnesite crystals. The primary mechanism involves microbial cells and extracellular polymeric substances leading to partial dehydration of Mg2+ ions from the Mg2+-H2O complex and allowing for further association with carbonate anions to from Mg-bearing carbonates. Unconfined compressive strength tests conducted on the saline loess samples after 7 days of curing revealed a significant influence of urea concentration on the strength of the solidified soil. The optimal urea concentration to obtain a better 7-day UCS ranged from 4 mol/L to 5 mol/L. Furthermore, solidified soil with 5% salinity yielded the highest 7-day UCS and soil with 3% salinity exhibited the lowest 7-day UCS at the same urea concentration. XRD and SEM analysis of the solidified soil samples indicated that the formation of magnesium carbonate minerals in the soil matrix by the biomineralization-MgO binder was responsible for the UCS enhancement. The remarkable 7-day UCS of saline loess solidified with biomineralization-MgO binder demonstrates the effectiveness of this material in curing saline loess.

Effect of Polyethylene Microplastics on the Microbial Community of Saline Soils

Mulching to conserve moisture has become an important agronomic practice in saline soil cultivation, and the effects of the dual stress of salinity and microplastics on soil microbes are receiving increasing attention. In order to investigate the effect of polyethylene microplastics on the microbial community of salinized soils, this study investigated the effects of different types (chloride and sulphate) and concentrations (weak, medium, and strong) of polyethylene (PE) microplastics (1% and 4% of the dry weight mass of the soil sample) on the soil microbial community by simulating microplastic contamination in salinized soil environments indoors. The results showed that:PE microplastics reduced the diversity and abundance of microbial communities in salinized soils and were more strongly affected by sulphate saline soil treatments. The relative abundance of each group of bacteria was more strongly changed in the sulphate saline soil treatment than in the chloride saline soil treatment. At the phylum level, the relative abundance of Proteobacteria was positively correlated with the abundance of fugitive PE microplastics, whereas the relative abundances of Bacteroidota, Actinobacteriota, and Acidobacteria were negatively correlated with the abundance of fugitive PE microplastics. At the family level, the relative abundances of Flavobacteriaceae, Alcanivoracaceae, Halomonadaceae, and Sphingomonasceae increased with increasing abundance of PE microplastics. The KEGG metabolic pathway prediction showed that the relative abundance of microbial metabolism and genetic information functions were reduced by the presence of PE microplastics, and the inhibition of metabolic functions was stronger in sulphate saline soils than in chloride saline soils, whereas the inhibition of genetic information functions was weaker than that in chloride saline soils. The secondary metabolic pathways of amino acid metabolism, carbohydrate metabolism, and energy metabolism were inhibited. It was hypothesized that the reduction in metabolic functions may have been caused by the reduced relative abundance of the above-mentioned secondary metabolic pathways. This study may provide a theoretical basis for the study of the effects of microplastics and salinization on the soil environment under the dual pollution conditions.

Mechanical properties of sulfate saline soil stabilized by coal gangue-slag composite geopolymers

Geopolymers, which are composed of solid waste, are eco-friendly binders characterized by rapid hardening and high strength. Using geopolymers to stabilize saline soils presents a sustainable solution for soil improvement. This study investigated two geopolymers, HG and SG, composed of a coal gangue-slag composite, to improve saline soils. The stabilized soils were prepared by blending geopolymers with saline soils in varying proportions of 10, 20, 30, and 40% by weight. The strength of the stabilized soils was evaluated based on the geopolymer dosage. Moreover, we examined the strength of the stabilized soils with curing time and elucidated the underlying mechanisms using microscopic analyses including XRD, FTIR, and SEM. This study revealed that: 1) the SG geopolymer outperformed the HG geopolymer in soil strength enhancement; 2) cohesion of the stabilized soil increased as the dosage and curing time increased, while the internal friction angle showed no clear trend; 3) the geopolymer stabilized soil mainly contained quartz, C-A-S-H, N-A-S-H, and C-N-A-S-H gels, and these gels were distributed on the soil particle surface and within the interstitial voids, improving the soil strength, and 4) in saline soil engineering, HG or SG geopolymer dosages should be above 30% and 20%, respectively.

Characterization and mechanism study of sulfate saline soil solidification in seasonal frozen regions using ternary solid waste-cement synergy

Infrastructures built on sulfate saline soil foundations in seasonal frozen regions are highly susceptible to salt-frost heave damage and salt corrosion. To address this issue, a method has been proposed utilizing a ternary blend of industrial solid waste materials - fly ash (FA), silica fume (SF), and brick powder (BP) - in conjunction with Portland cement (PC) for the solidification of sulfate saline soil. The feasibility of this solidification technique has been validated through a series of tests, including unconfined compressive strength tests, freeze-thaw cycle tests, salt leaching tests, and microstructural analysis. The results showed that: The unconfined compressive strength of the solidified saline soil at 56 days increased by up to 61.27 times compared to untreated saline soil. During the freeze-thaw cycles, the volume of salt-frost heave in the solidified saline soil was only 10.75% of that in untreated soil, with a reduction in salt-frost heave force by up to 90.94%. Furthermore, during the salt leaching process, the rate of salt migration in the solidified saline soil could be slowed by up to 4.15 times, while the total amount of salt leached was only 31.34% of that in untreated saline soil. Additionally, through the combined use of X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), and Energy Dispersive X-ray Spectroscopy (EDS), it was discovered that the interactive synergistic effect of the solidifying agents in a SO42- rich environment facilitated the dissolution of Si-O and Al-O micro-lattices on the surface of the solidifying agent particles. This led to the extensive formation of C-(A)-S-H gels and AFt products, resulting in the transformation of the soil structure from dispersed to flocculated. The comprehensive test results indicate that the mechanical properties, frost resistance, and salt corrosion resistance of the solidified saline soil have significantly improved, with an optimal solidifying agent mixture ratio of 3% PC, 5% FA, 5% SF, and 6% BP. These findings can provide a reference for the solidification treatment of sulfate saline soil foundations in seasonal frozen regions.

Study on the coupling mechanism of water-heat-vapor-salt-mechanics in unsaturated freezing sulfate saline soil

Understanding the internal regularity of unsaturated freezing sulfate saline soil is of utmost importance concerning the durability and stability of cold region engineering in sulfate saline soil areas. One-sided freezing experiments were performed on unsaturated sulfate saline soils with varying salt and moisture contents and temperature gradients to investigate the interplay of water-vapor-salt migration, heat transfer, ice-water and water-vapor phase transformations, salt crystallization, and salt-frost heave. This study presented a novel water-heat-vapor-salt-mechanics coupling model that considers water-vapor-salt migration and its feedback on soil deformation. The results signify that the water accumulation at the top surface of unsaturated freezing sulfate saline soil is primarily due to water vapor migration. Water-vapor-salt migration, ice-water phase transition, and salt crystallization form more ice and salt crystals, filling the air-filled pores and causing significant salt-frost heave. Water vapor transfer and accumulation further exacerbate the soil deformation for unsaturated freezing sulfate saline soil. The calculating results agree with the test data and demonstrate the efficacy of the proposed five-field coupling model. These findings hold significant implications for developing practical solutions for mitigating the negative impacts of salt-frost heave induced by water-vapor-salt transfer in unsaturated freezing sulfate saline soil on construction projects.

Investigation of the liquid water content in composite saline soil containing chloride and sulfate ions

Different salt types have different effects on the liquid water content of saline soil, resulting in differences in the physico-mechanical properties and water/salt migration process of saline soil. In order to investigate the phase transition process and the change of the liquid water content in composite saline soil, saline soils with the same total salt content and different ratios of sodium chloride and sodium sulfate were taken as the objects. The results indicated that two phase transitions occur in the saline soil with single salt type, while three phase transitions can be found in the composite saline soil with two salt types. Mirabilite crystallization contributes to the 1st phase transition, mirabilite and ice precipitate together in the 2nd phase transition process, and mirabilite, ice, and hydrohalite precipitate simultaneously in the 3rd phase transition process. The liquid water is reduced in the phase transition process during cooling, and the pore characteristic has been changed significantly. The change of the liquid water content reflects the processes of salt crystallization and ice formation in saline soil, then the amounts of ice and hydrated salt were calculated at different temperatures, and the mechanism of inhibiting the deformation of sulfate saline soil was examined by adding sodium chloride. The results have reference value for those seeking understanding of the deformation in natural composite saline soil, and these findings can provide theoretical basis for the phase transition mechanism of saline soil in cold regions.

Geodetic imaging and dynamic modeling of saline mudflat using time-series InSAR in Howz-e-Soltan Salt Lake, Qom, Iran

Due to the physicochemical properties of salt swelling and collapsibility, the potential geological hazards threaten the large-scale infrastructure and residential areas in the saline-soil region. Geodetic imaging and dynamic monitoring of the spatiotemporal evolution process of saline soil are vital to detect the potential geological hazards in a vast area. Therefore, this paper presents a coupled deformation model synthesizing environmental factors and trigonometric function model for estimating the time-series InSAR deformation and interpreting the dynamic evolutionary mechanism of the saline mudflat. To demonstrate the advantages of the proposed model, the sulphate saline mudflat is selected as the study area, which is traversed by the Tehran-Isfahan high-speed railway in Howz-e-Soltan Salt Lake, Qom, Iran. Moreover, 259 interconnecting interferograms were selected for the time-series InSAR estimation, composed of 87 Sentinel-1A images obtained from October 2014 through December 2018. Then, the time-series deformations, including the annual deformation velocity and the accumulated deformation, are extracted by the original estimation, polynomial, trigonometric and environmental models. The comparison results show that the environmental model's RMSEs (root-mean-square errors) are smaller than others. It should be noted that the linear deformation, periodic oscillation, and deformation derived from the environmental factors (i.e., precipitation and temperature) are extracted by the environmental model. Furthermore, the dynamic evolutionary mechanism of the saline mudflat is interpreted according to the physicochemical properties of sulphate/carbonate saline soil. The results derived from the environmental model suggested that the saline-soil deformation is directly related with the environmental changes: rapid collapsibility occurs when the precipitation increases from September to the next May, while uplift due to the salt swelling in the dry and rainless season from May to September every year. Our findings provide an opportunity to detect, prevent and control the potential geological hazards in saline mudflats.

Responses of growth, yield and chemical composition of tomato to phosphorus nutrition under different saline environments

Growing crops on marginal and salt-affected soils with saline water will be more important for agricultural production in the future. The most prevalent anions in saline soils, chloride (Cl-) and sulfate (SO4 2-) have distinct effects on plant growth, metabolism, nutrient composition, productivity, and nutrient requirements. In order to ascertain the role of phosphorus in mitigating salinity stress in tomato plants, a pot experiment was conducted in a screen house under two types of saline environments chloride-dominated (Cl-: SO4 2- = 7:3) and sulfate-dominated (Cl-: SO4 2- = 3:7), with two comparable ECe levels (non-saline and 6 dS m−1) and four graded phosphorus levels (0, 12.5, 25, 50 mg kg−1soil). The significant increase in yield up to 50 ppm added P indicated that plants require more P under chloride salinity than sulfate salinity. In non-saline, chloride, and sulfate-dominated conditions, increased P from 0 to 50 ppm increased chlorophyll 'a‘ and 'b‘ values by 21.4, 19.8 and 23.8% and 10, 20 and 14%, respectively. The reduced photochemical efficiency due to salinity, was increased 32%, 30% and 13% as P level increased from 0 to 50 ppm in non-saline, Cl--6 and SO4 2—6 conditions, respectively. The TSS, ascorbic acid content and titrable acidity of tomato fruits was improved with mild salinity stress but reduced with added P. The plant N, P and K content increased significantly with each added P level irrespective of types of salinity. The plant composition indicated an antagonism between phosphorus and chloride ions and synergism between phosphorus and sulfate ions.

Experimental and Numerical Modeling of the Freeze–thaw Response of U-Shaped Channel Lining on Sulfate Saline Soil Foundation

Under the influence of seasonal freeze-thaw cycles, the concrete lining of channels situated on saline soil foundations is highly vulnerable to an array of deleterious phenomena, such as frost heave, salt expansion, and corrosion. To investigate the synergistic interplay among saline soil substrates, U-shaped channel lining structures, and ambient temperatures during freeze-thaw cycles, a novel Hydraulic-Thermal-Salt-Mechanical (HTSM) model is established in this study. The HTSM model elucidates the migration of moisture and salt solute, ice-water phase transitions, and sodium sulfate crystallization within unsaturated saline soils throughout the freeze-thaw cycles. It considers the variations in volume and pore solution volume before and after the phase transition of sodium sulfate. Temperature and salt frost heaving force measurements obtained from outdoor freeze-thaw cycles are compared with numerical simulation results to validate the efficacy of the HTSM model and investigate the distribution patterns of salt frost heaving force (frost swelling force) along the channel. The results showed that the frost swelling force and depth exhibit a great linear relationship and the maximum stress of the U-shaped channel appears at the bottom of the channel, highlighting the good arching force characteristics of the U-shaped structure which prove that bottom of the channel is also the most prone to fracture. Significantly, the initial water content significantly impacts the frost swelling force—it increases by 4% while the frost swelling force increases by 76%. Comparing the numerical simulation results of temperature variations, moisture changes, and salt-frost heaving forces with the outdoor experimental data, it is evident that the proposed HTSM model effectively simulates the salt-frost heaving patterns observed in U-shaped channel linings.

Влияние фосфогипса и электролита травления стали на химические свойства почв рисовых чеков в условиях Ростовской области

Purpose: to study the effect of various ameliorants and their combinations, as well as leaching on paddy soil characteristics in laboratory conditions for determining the possibility of their further application. Materials and methods. In the course of the research, a soil reclamation survey of paddy fields in Rostov region was carried out. Soil samples analyzes were carried out in an environmental analytical laboratory using generally accepted methods. Soils with different chemistry, degrees of salinity and salinization, and different gypsum content were taken for the laboratory experiment. Based on the results of soil samples study, phosphogypsum, steel pickling electrolyte, and their combinations were used as ameliorants. Results. Leaching without ameliorants contributed to a total salt content decrease. On slightly saline soils of chloride-sulfate chemistry, their number decreased by 54 %, and on moderately saline soils of sulfate salinity by only 5 %. Ameliorants, especially phosphogypsum, increased their amount in non-saline soils by 5 times, and in slightly saline soils – by 2.7 times due to the accumulation of calcium sulfates. Their accumulation was not observed in moderately saline gypsum-containing soils. The steel pickling electrolyte reduced their quantity by 18 %, compared to the control. The soil absorption complex of non-saline and slightly saline soils was optimized, but in gypsum-containing soils it remained virtually unchanged. Conclusions. Laboratory experiments have shown that soils of chloride-sulfate salinity, having magnesium salinity and undersaturation with exchangeable calcium in the soil absorption complex, can be improved by using phosphogypsum and steel pickling electrolyte as an ameliorant, as they are the most accessible to land users. They promote the formation of gypsum, which accelerates the process of replacing exchangeable magnesium and sodium with calcium. Reclamation of highly gypsum-rich soils with a gypsum content of more than 20 % and easily soluble salts of more than 1.0 % using traditional methods is not very successful.

Study on Strength Characteristics and Constitutive Model of Frozen Sulfate Saline Silty Clay under High Confining Pressure

Study on Strength Characteristics and Constitutive Model of Frozen Sulfate Saline Silty Clay under High Confining Pressure

The overlooked ion: Unraveling the effects of magnesium-specific toxicity on willows under sulphate salinity

Among all the current stressors on global agricultural systems, soil salinity is one of the most significant and continues to escalate. Traditionally, sodium chloride is the salt employed for studying salt stress in plants, but for many regions, sulphates are the predominant salts that cause soil degradation and curtail agricultural production. Willow trees (Salix spp.) have been identified as potential candidates for multipurpose establishment on salinity-affected marginal agriculture fields. To compare the impacts of sodium and magnesium sulphate salts, 12 native and hybrid willow genotypes were subjected to four sodium and magnesium sulphate salt treatments for 12 weeks. Magnesium sulphate treated willows showed more significant growth impacts, and displayed treatment-specific inhibition of photosynthesis, increased disruption of mineral nutrient balance, and greater inhibition of sulphur assimilation, compared to the trees treated with same level of sodium and same treatment osmolality. In addition, it was apparent that sulphate treatments encouraged sulphur uptake and translocation to the leaves, where it was partitioned to organic sulphur, but did not pool in small organic sulphur-containing compounds. The advantages and disadvantages of two different salt tolerance strategies were compared through a case study with two native willows, a sodium excluder and a sodium accumulator.

Study on Mechanical Properties of Sulfate Saline Soil Improved by CLI-Type Polymer Active Agent

Large amounts of soluble salts in a soil enhance the soil sensitivity to changes in its properties induced by changes in environmental conditions, such as easy dissolution in water and easy occurrences of salt heaving in low-temperature environments, which make the soil volume swell rapidly, leading to a series of engineering disasters. Moreover, the growth and development of surface vegetation will be inhibited due to excessive salinity, resulting in a gradual decline in the ecological functionality of the area. A polymer active agent (CLI) was selected for the ecological improvement of sulfuric acid saline soils. Triaxial compression tests and a test on the soluble salt content of the treated soil were carried out to investigate the effects of polymer active agent content and maintenance time on the mechanical properties and soluble salt content of sulfate saline soils. The results showed that the addition of CLI can improve the soil strength by increasing the cohesion of the specimen, and the improvement increases significantly with the content of CLI and the curing age. Meanwhile, the calcium ions in CLI can react with sulfate ions in sulfate-salted soils to produce calcium sulfate precipitation to alleviate soil salinization. The scanning electron microscopy (SEM) images indicated that an appropriate content of CLI (about 8%) can strengthen the soil structure through an excellent chelating ability, enhancing the strength of the soil.