Salt Migration Research Articles

Developing Mathematical Models to Study Changes in Groundwater Levels and Salt Concentration

Understanding how groundwater and salt concentrations change when freshwater supplies are monitored is crucial. In this work, groundwater fluxes and salt migration were considered when studying groundwater level changes and mineralisation processes. To study salt and water level changes, a more realistic mathematical model was developed to reflect the object’s basic features. To monitor geofiltration and geomigration using mathematical and numerical modelling to provide recommendations, nonlinear differential equations were applied. Scientific research on mathematical and numerical modelling and computer experimentation of the issue is briefly reviewed. Also developed were a mathematical model with two integer-valued boundary conditions and an efficient finite difference numerical approach. Changing groundwater and pressure water levels, filtration permeability, water loss coefficient, and filtration rate connected to water level all affect the environment when building a mathematical model for salt migration filtration. The article predicts groundwater, pore water, and salt concentrations in high- and low- permeability layers. Scientific research on mathematical and numerical modelling and computer experimentation of the issue is briefly reviewed. Also developed were a mathematical model with two integer-valued boundary conditions and an efficient finite difference numerical approach. Changing groundwater and pressure water levels, filtration permeability, water loss coefficient, and filtration rate connected to water level all affect the environment when building a mathematical model for salt migration filtration. This study considered soil density, active porosity, and third-order boundary conditions Open, unlike earlier studies. Since the problem is represented by nonlinear differential equations with free variables, analytical solutions are unattainable. An effective numerical method and a stable implicit system with high-accuracy approximation, finite difference approach, and forward and backward sweep approaches were given to overcome these challenges.

Water–Salt Migration Patterns among Cropland–Wasteland–Fishponds in the River-Loop Irrigation Area

In order to investigate the influence of freshwater fish ponds on water and salt transport in cultivated wasteland in salinized areas, a typical study area was selected in the middle and lower reaches of the Hetao Irrigation District in China in the Yichang Irrigation Domain, and the temporal and spatial changes in the salinity of soil and salinity of groundwater and fish pond water in the cultivated–wasteland–fish pond system were characterized through the monitoring of the environmental information of soil and groundwater at the boundaries of the cultivated land, wasteland, and fish ponds. Salinity changes and groundwater migration in different periods were determined, and the response of soil salinity to the depth of groundwater burial was analyzed, as well as the effect of fish ponds on soil salinization. The results showed that the amount of groundwater migrating from cropland to wasteland during the simulation period in 2022 was 2700 m3, the amount of groundwater migrating from wasteland to fish ponds was 630 m3, and the amount of groundwater migrating from fish ponds to wasteland during the fall watering period was 440 m3. From an overall perspective, the average soil salinity of wasteland was 1.56 times higher than that of the boundary of fish ponds. Not only do fish ponds play a positive role in the ecosystem, but they also have a desalinization effect that reduces soil salinity significantly. Groundwater depth and soil salinity have an exponential relationship; when the depth of groundwater is greater than 1.75 m, the soil salinity varies little with the depth of groundwater and the soil salinity is less than 0.66 ds/m, which can be determined as the critical depth, and the average depth of groundwater in cultivated land in the study area is 1.5 m. Therefore, it is necessary to reasonably control the water level of fish ponds, so as to make the groundwater depth of cultivated land control between 1.75 m and 2.0 m, and to prevent soil salinization.

Characteristics and Influence Factors of Soil Water and Salt Movement in the Yellow River Irrigation District

Climate change and human activities lead to freshwater shortage, soil salinization, and food security crises in arable land. To explore the natural and irrigation factors on soil water and salt movement, this study quantitatively analyzed the dynamic characteristics of soil water and salt movement under precipitation, groundwater irrigation, and brackish water irrigation conditions for the next 30 years using Hydrus-1D model-based parameters obtained from the winter wheat–summer maize rotation experiments in the Yellow River Irrigation District. The results showed that precipitation was the key factor of climate change affecting soil water and salt migration, especially in the 0–20 cm soil layer. Under both SSP585 and SSP245 climate scenarios, rainfall in normal and wet years promoted salt leaching up to 1 m below the surface soil. But in dry years, salt washing treatment was required for the tillage layer to prevent salt accumulation. The higher the groundwater level was, the higher the soil water and salt content was in the 0–100 cm soil layer. In this soil layer, a 2 m groundwater level contributed 30% to wheat water needs, while a 3 m groundwater level contributed 18%, and no significant contribution was observed for a 4 m groundwater level. The salinity of the soil profile showed an overall increasing trend with irrigation using 1–3 g/L brackish water for 30 years. However, the salinity in the 0–100 cm soil layer was below the salt tolerance threshold of winter wheat and summer maize with salts accumulated in the 1–2 m soil layer. Considering the salinization of the root zone and crop water needs, it is recommended that the safe groundwater level for brackish water irrigation should be 3 m in the study region. This study provides scientific reference for groundwater–farmland ecosystems to utilize brackish water and treat saline–alkali lands.

(Invited) Exploiting Organic Materials for Next Generation Batteries

Energy storage plays, undoubtedly, a fundamental role in the process of total decarbonization of the global economy that is expected to take place in the coming decades. The energy transition to a renewable and sustainable generation will be the solution to reduce greenhouse gas emissions and thus achieve the European Commission´s goal of becoming the world´s first decarbonized economy. Our mission is therefore aligned with this goal by improving the industry competitiveness and sustainable development, from a benchmark position in energy research, generating disruptive knowledge in materials and high-tech solutions. Within the electrochemical storage area, and in particular organic hybrid materials group, we work from the synthesis and design of organic molecules and polymeric materials to the understanding of their properties and interfaces with the ultimate goal of developing next generation battery systems.In this talk, a general overview of our core research will be given with a special focus on the design of polymer electrolytes. In recent years we have explored various strategies to meet the requirements of electrolytes: high lithium cation conductivity and stability against high voltage and towards lithium metal (LiM). In this scenario we have synthesized new polymers and lithium salts. Inspired by poly(ethylene oxide), polymers containing ethylene oxide units will be presented, with decreased crystallinity to improve ionic conductivity.1 This improvement generally compromises the mechanical properties. In this respect, different strategies will be shown.2,3 However, it is difficult to design a polymer that meets all properties. In this scope, a bi-layer concept will be described and how salt migration can be addressed using a single-ion conducting polymer electrolyte (SLIC).4,5 Motivated by the bi-layer strategy, within SAFELiMOVE EU project a new solid-state-based technology have been proposed.6 The most relevant work carried out in the framework of the project will be presented.References I. Aldalur et al., J Power Sources, 347, 37–46 (2017).I. Aldalur et al., J Power Sources, 448, 227424 (2020)I. Aldalur, M. Martinez-Ibañez, M. Piszcz, H. Zhang, and M. Armand, Batter Supercaps, 1, 149–159 (2018)M. Arrese-Igor et al., ACS Energy Lett, 7, 1473–1480 (2022)M. Arrese-Igor et al., Energy Storage Mater, 45, 578–585 (2022)https://safelimove.eu/

Simulating Water and Salt Migration through Soils with a Clay Layer and Subsurface Pipe Drainage System at Different Depths Using the DRAINMOD-S Model

Soil salinization affects more than 25% of land globally. Subsurface pipe drainage is known for its effectiveness in improving saline–alkali land. The red clay layer (RCL) hinders soil improvement in the Hetao Irrigation District of Inner Mongolia, China. The soil water and salt migration rules at different buried depths and RCL were studied based on the field subsurface pipe drainage test and simulation using the DRAINMOD-S model (Version 6.1). The following implications can be drawn from the results: (1) Although the RCL affected the accuracy of the model, the calibrated statistical results met the application requirements, and the DRAINMOD-S model can be used to analyze subsurface pipe drainage under different distribution conditions of the RCL. (2) The RCL can reduce the drainage efficiency of the subsurface pipe, specifically when the distribution is shallow. (3) The soil desalting rate increased with an increase in the buried depth of the subsurface pipe. The desalination effect of shallow soil was better than that of deep soil. The RCL reduced the drainage and salt removal efficiency of the subsurface pipe. Burying the subsurface pipe as far above the RCL as possible should be considered. Thus, it is feasible to apply the DRAINMOD-S model to relevant studies.

Carbon capture from low CO2 concentration stream through ternary alkali metal nitrates promotion of MgO sorbents at intermediate temperature and low space velocity

Many MgO sorbents exhibit high CO2 uptake in the presence of high concentration CO2 and aided by high space velocity, which unfortunately leads to low CO2 capture efficiency from the gas stream. This study investigates the effect of Li/Na/K ratio on sorption performance in dilute CO2 streams (15% CO2) using alkali metal nitrates-promoted MgO sorbents at a low space velocity of 20 ml/g·min in fixed bed reactor. Study shows that the ratio of Li/Na/K in ternary alkali nitrate salt mixture significantly affects the induction periods for the second phase CO2 sorption, which is a key contributor to high CO2 uptake. High LiNO3 content in ternary mixture leads to long induction period, and therefore lower CO2 capacity during the 4 h period. Conversely, high ratios of NaNO3 and KNO3 leads to shorter induction periods. Among the samples, MgO with 9 mol% (Li0.18Na0.52K0.3) exhibits the highest CO2 sorption capacity of 5.56 mmol/g at 240°C in 4 h (20.6% CO2 capture efficiency) and 3.18 mmol/g after 5 cycles (10.8% CO2 capture efficiency). Comparative studies show that optimal temperatures for CO2 sorption are higher when using pure CO2 (280 to 320°C) than when using 15% CO2 (240°C) due to the thermodynamic equilibrium. CO2-TPD results indicate that CO2 desorption proceeds in two phases similar to CO2 sorption, and the presence of alkali salt in MgO also promotes the decomposition of bulk carbonate to CO2. It is shown that molten salt migration and agglomeration of MgO particles are likely the factors that lead to decline in CO2 uptake over the sorption-desorption cycles.

Experimental investigation, numerical simulation and RSM modelling of the freezing and thawing of Mozzarella cheese

Freezing can be used to preserve functionality of Mozzarella cheese allowing export to distant markets but limited tools are available for prediction of freezing and thawing times as a function of composition and processing variables. Freezing and thawing processes were experimentally and numerically assessed for six Mozzarella samples, differing significantly in block size and composition. Numerical simulations using an enthalpy method were developed to build a validated and robust model for solving heat and mass transfer equations. A decrease in salt (NaCl) content from 1.34 % w/w to 0.07 % significantly altered the temperature of phase change from ∼–4.5 °C to –3 °C. Simulations showed minimal impact of salt migration on the salt in free moisture content deeper than ∼1–2 centimeters from the surface during freezing, with a slight increase of 8–10 % salt in free moisture at the block center. A response surface methodology (RSM) model was fit to the simulated data providing a useful tool for predicting freezing and thawing times for block sizes and a wider range of operating conditions enabling future process optimization. The RSM model indicated that increased salt content increased freezing time but decreased thawing time.

Rapid freezing process of static salt-containing droplets under salt exclusion

In marine salt spray environment, the freezing process of Saline droplets is of great importance. Because the salt is almost insoluble in ice and its solubility is in the micromolar range, the brine freezes in the form of pure ice, and the salt ions are excluded to the unfrozen part of the system. When the salt is frozen rapidly, the difference of thermal and mass diffusion leads to the retention of brine and the ice entraps interstitial brine. A simulation method suitable for the fast freezing process of small droplets with low salinity on a cold substrate is proposed. The freezing process and salt migration characteristics of NaCl salt solution are studied. The results show that this method can reflect the solidification and the entrapment of brine. In addition, freezing becomes slower with the increase of salt concentration in the solution. Interestingly, under the background of low salinity, there is a certain linear relationship between freezing time and salinity, and the local temperature will greatly affect the salt concentration of the intercepted brine compared with the initial droplet salinity.

Structural analysis of the central Tunisian Atlas: Implications for salt-related structures and conjugate strike-slip faults

This scientific study aims to investigate the geological characteristics and tectonic processes of the central Tunisian Atlas region, focusing on the influence of tectonic events related to the Jurassic-Early Cretaceous Tethyan rifting and the subsequent Cenozoic tectonic inversion and uplift. In particular, this research emphasizes the strong control of tectono-sedimentary events on the geology of the central Tunisian Atlas, with specific attention given to the understudied isolated salt-related structures. To gain insights into the relationship between deep-seated faults, salt tectonism, and the conjugate strikes-slip faults, this study is based on subsurface data, including 2D seismic reflection and gravity data. The analysis investigates, the location of salt extrusions in relation to fault intersections. Results derived from subsurface data indicate that diapiric intrusions primarily occur at the junctions of major fault systems likely inherited from the Triassic-Jurassic Tethyan period. Notably, salt migration was remarkably active during the early Cretaceous, as evidenced by halotectonic sequences and salt-related mini-basins. Furthermore, fault blocks display sedimentary infill above tilted blocks, where salt structures appear to occur at their peripheries. During the subsequent tertiary compressions, the structural configurations of the basin (i.e., Z-shape basin) promote the strike-slip movement along pre-existing faults. This new structural interpretation suggests a closely relationship between fault zones inherited from the Jurassic-Early Cretaceous Tethyan Opening and isolated salt-related structures. The subsequent Cenozoic shortening events, including the Atlassic and Alpine events, have led to uplift of the deep-seated faults, facilitating the ascension and deformation of Triassic evaporitic sediments within subcircular isolated structures. Field observations and seismic sections indicate the presence of sedimentary gaps resulting from these processes. The findings of this study contribute to a comprehensive understanding of the deep tectonic framework and shallow salt-related structures in the central Tunisian Atlas.

Applying magnetic techniques to determine the evolution of reactive diapirs: A case study of the Lusitanian basin

The western Iberian margin underwent complex evolution during the Mesozoic and Cenozoic. It was subjected to successive extensional and compressional phases, where salt tectonics played a significant role in both. The role of onshore structures during basin formation and inversion is not fully understood, and different chronological relationships between structures have been proposed. To better understand the history of salt body emplacement, we present paleomagnetic and magnetic fabric data from Jurassic carbonates, comprising cover rocks of the diapiric system. Magnetic fabrics show two types of behavior. Type 1 fabrics show magnetic foliation parallel to bedding—the magnetic lineation, after bedding correction, is horizontal and parallel to the diapiric contacts. This fabric is a consequence of overpressure during salt migration, whose effect is limited to the area near the diapirs. Type 2 fabric is characterized by a magnetic lineation parallel to the strike of bedding and—the intermediate and minimum magnetic axes are dispersed on a vertical girdle parallel to the shortening direction. This is interpreted as a compressional fabric that developed during basin inversion. Paleomagnetic results reveal a stable paleomagnetic component carry by magnetite with characteristic unblocking temperatures (175–450 °C) and coercivities (30–100 mT). Twelve of the 14 calculated mean directions show homogeneous behavior in their magnetic properties and directions, with positive inclinations, northward directions, with synfolding to postfolding behavior. We calculated the remagnetization direction (Dec: 347.5°, Inc.: 51.3°) and compare it to the APWP. It was likely acquired during the Cretaceous Normal Superchron, following the extensional deformation phase and prior to basin inversion. The paleodips (i.e., the bedding at remagnetization times) indicate that tilting occurred mainly during the extensional stage, meaning that the diapirs had already been developed. This indicates a strong Mesozoic salt tectonic component in the present-day structuring of this sector of the Lusitanian basin.

Improvements in saline soil and the law of water-salt transport based on salt inhibition using MICP technology

Soil desertification and salinization are the main environmental disasters in arid and semi-arid areas. It is of great significance to study the water - salt migration law of saline soil and propose corresponding water- salt regulation and control measures. Microbial-induced calcite precipitation (MICP) technology was proposed to improve saline soil based on salt inhibition, and the water–salt–heat coupling migration law and salt-frost heave deformation law of saline soil before and after improvement were studied using soil column model tests. XR1#, XR2#（Saline-alkali-tolerant mineralization bacteria isolated from saline soil) and Sporosarcina pasteurii were used in the MICP improvement and the effect of XR1# was the best. Under high-temperature evaporation, the water migration change rate, water loss rate, accumulated evaporation amount, and accumulated salt content of the improved soil columns within a depth range of 0–40 cm were reduced by an average of 53.6 %, 47.3 %, 69.5 %, and 40 %, respectively, compared with the untreated soil column. During low-temperature cooling, the characteristics of water-salt migration changed significantly, and the deformation of salt-frost heave decreased significantly. The water-salt content at the freezing point (−4.5 °C) changed from a cliff-like steep drop (untreated saline soil) to a slow decrease at environmental temperature (MICP-treated saline soil), and the amount of water crystallization decreased from 81 % to 56.7 % at −5 °C. At the end of the cooling process, the amount of salt-frost heaving on the surface of the soil columns decreased by an average of 62.7 %. Based on the measured data, a numerical simulation was conducted using the HYDRUS-1D model, which had good reliability and accurately simulated and predicted the law of water-salt migration in saline soil under the conditions of microbial solidification and improvement. MICP technology significantly reduced the change rate of water-salt migration and water evaporation in saline soil, hindered salt accumulation, and reduced salt-frost heave deformation, which effectively improved saline soil. The research results provide an important innovation and theoretical basis for the improvement of saline soil.

Cycling Stability of Calcium-Impregnated Vermiculite in Open Reactor Used as a Thermochemical Storage Material

Recent research into thermochemical storage (TCS) materials has highlighted their promising potential for seasonal building heating, through energy capture and release during dehydration and hydration cycling. A common TCS material used throughout this investigation was calcium chloride (CaCl2)-impregnated vermiculite-based salt in matrix (SIM). This material was assessed for its robustness during charging and discharging cycles to assess its behavior and in terms of energy stability and chemical stability; the results of which showed consistent volumetric energy density and maximum temperature changes over seven cycles. The calcium SIM did, however, show a decline in leachable Ca content, which was presumed to be a result of stabilization within the vermiculite, and chloride concentration showed little change over the course of the study. Real-time visualization using a high-resolution microscope of calcium SIM particles showed a salt phase change and migration of liquid salt into the valleys of the lamella. A novel cobalt chloride (CoCl2) SIM was used to visualize the hydration path across the particle, through distinct color changes depending on hydration state. The results indicated that the topography of the vermiculite played a significant role in the passive hydration modeling.

Mechanical properties and anti-efflorescence of cement-based coating containing silicon-aluminum based powder and modified-polyacrylate emulsion

The objective of this paper was to prepare a novel type of anti-efflorescence cement-based coating with excellent mechanical properties using the modified polyacrylate emulsion (MP) and silicon-aluminum based powder (SA), and provided an optimum proportion. Silica sol (SS) and polydimethylsiloxane (PDMS) were selected as modified components to incorporate into polyacrylate emulsion (PA). The synergistic effect of MP and SA on the tensile strength, water absorption, hydration process, microstructure and anti-efflorescence property of cement-based coatings were investigated. The research results demonstrated that the tensile strength and waterproof in coating containing MP and 0.3 wt% SA were increased by about 73.4% and 52.1%, respectively, compared with the reference sample. The reason could be attributed to the densification of the internal structure due to the formation of “Si-O-Si” structure and pozzolanic effect of SA. In addition, the hydrophobic PDMS can hinder the migration of water and salt, thereby limiting the diffusion of alkali ions outward. Hence, the efflorescence area of the modified-coating was decreased to 1.58%.

Compounding effects of human activities and climatic changes on coexistence of oasis-desert ecosystems: Prioritizing resilient decision-making for a riskier world

Water-salt balance is critical for the stable coexistence of salt-affected and groundwater-fed oasis-desert ecosystems. Yet, a comprehensive investigation of how soil salinization and groundwater degradation threaten the coexistence of oasis-desert ecosystems is still scarce, especially under the compounding effects of human activities and climatic changes. Here, we assessed the impacts of irrigated agriculture on hydrological regimes in oasis-desert systems, investigated the spatio-temporal variations of soil salinization in irrigated cropland, and evaluated the implications of the interplays of soil salinization and groundwater degradation on the coexistence of oasis-desert ecosystems in northwestern China, based on meaningful modelling approaches and comprehensive measurements over 1995–2020. The results showed that the irrigation return flow coefficient decreased sharply from 0.21 ± 0.09 in the traditional irrigation period to 0.09 ± 0.01 in the water-saving irrigation period. The continuous drop in groundwater tables and significant degradation of groundwater quality are occurring throughout this watershed. The eco-environmental flows are reaching to their limit with watershed closures (i.e., the drainage from the oasis region into the desert region is being weakened or even eliminated), although these progressions were largely hidden by regional precipitation and streamflow variability. The process of salt migration and accumulation across different landscapes in oasis-desert system is being reshaped, and soil salinization in water-saving agricultural irrigated lands is accelerating with a regional average annual growth rate of 18%. The vegetation in this watershed is degrading, and anthropogenic disturbance accelerates this trend. Our results highlight that environmental stress adaptation strategies must account for resilience maintenance to avoid accelerating catastrophic transitions in oasis-desert ecosystems. Determining the optimal oasis scales and formulating the best irrigation management plans are effective and resilient decision-making ways to maintain the coexistence relationship of oasis-desert ecosystem in drylands.

Experimental study on salt weathering of sandstone with different weathering degrees

ABSTRACT Due to lithological and environmental differences, the weathering degree of stone heritage varies even within the same area. Various factors dominate the weathering process at different stages. Implementing preventive measures has reduced the impact of controllable factors such as human activities. However, salt weathering caused by atmospheric pollutants, water, and salt migration in rock formations has emerged as a major contributor to the deterioration of stone heritage. Understanding the re-weathering characteristics of stone cultural heritage at different weathering degrees is crucial for preventive protection. This study investigated the weathering status of Nanshiku Temple and designed an experimental scheme based on field monitoring data. By controlling the number of freeze-thaw cycles, stones with different weathering degrees were prepared, and sulfate weathering simulations were conducted. The results revealed severe damage to sandstone due to Na2SO4 crystallization. Higher initial weathering degrees resulted in more pronounced deterioration and faster weathering rates. Surface hardness analysis approximated the decay process using a logarithmic function within a certain range but could not fully capture the overall weathering of the stone. Uniaxial compressive strength showed a strong correlation with weathering indices like p-wave velocity. These findings provide a theoretical basis for preventive protection efforts in stone cultural heritage.

Physicochemical Properties and Microstructure of Plaster Layer of Ancient Wall Paintings in Northwest China

ABSTRACT Several grottoes were excavated in Northwest China between the 5th and 13th centuries, and the most famous relics of these grottoes are wall paintings. The plaster layer is the most significant layer in grotto wall paintings, and its characteristics are related to deterioration, treatment measures, and restoration materials during the conservation process. However, studies investigating and analyzing ancient plasters in grotto wall paintings are scarce. In this study, a series of laboratory experiments was conducted on ancient plasters of four grottoes in Northwest China to reflect their physicochemical properties and microstructural characteristics. The results reveal that the plaster is composed of sedimentary soil from the riverbed or floodplain near the grottoes mixed with vegetal fibers. The sedimentary soils were mainly composed of fine-grained soil mixed with a certain concentration of sand (0‒41%). In the plaster production process, lime was not artificially added, and the internal structure of the plaster was formed by the agglomeration of sand-clay fibers. Capillary pores in the plaster are the main channels for salt migration and accumulation, and the accumulation of salt destroys the cementation between the soil particles, rendering the plaster loose and porous. Therefore, attention should be paid during daily maintenance to prevent further damage to wall paintings due to the migration and accumulation of salts caused by rainwater and water vapor. Sedimentary soils from nearby riverbeds or floodplains can be used in restoration work to obtain better compatibility with the original plaster.

Durability of advanced low temperature lithium compound electrode ceramic fuel cell for transportation

In recent years, a ceramic fuel cell with lithium compound such as Ni0·8Co0·15Al0·05LiO2 (NCAL) as its electrode is reduced in H2 to produce lithium compounds containing molten salt and diffused into oxide electrolyte to form an “oxide-lithium compounds molten salt” composite electrolyte with ultra-high ionic conductivity, which made the cell have remarkable low-temperature power generation performance. It is found that the dynamic migration of lithium compounds produced by NCAL anode in the cell with Ce0.9Gd0.1O2-δ (GDC) as electrolyte during the constant current durability test is the main reason for the cell performance degradation. In this paper, we found that adding different mass ratios of NaFeO2 to the GDC electrolyte to construct GDC/NaFeO2 composite electrolyte can significantly affect the durability of the cell. Under the constant current density test conditions of 550 °C, 0.2 A cm−2, the performance of the cell with GDC/NaFeO2 composite with a mass ratios of 8/2 as electrolyte maintained relatively good durability in the constant current test of 50 h. The characterization results show that the NaFeO2 reacts with lithium compounds such as LiOH to generate LiFeO2 and NaOH, and NaFeO2 is reduced to Fe and NaOH by H2. A proper amount of NaFeO2 in the GDC/NaFeO2 composite electrolyte can produce sodium compound molten salt during the performance test to replace the role of lithium compound molten salt in improving the electrolyte ionic conductivity and the cell sealing, while slowing down the dynamic migration of the molten salt in the cell, thus improving the durability of the cell. The findings in this paper provide evidence and relevant theories for the performance degradation and durability improvement mechanism of this new type of lithium compound electrode ceramic fuel cell (LCCFCs), and propose new strategies for obtaining LCCFCs with better durability.

Study on Water and Salt Transport under Different Subsurface Pipe Arrangement Conditions in Severe Saline–Alkali Land in Hetao Irrigation District with DRAINMOD Model

As an effective method to improve saline–alkali land, the drainage from subsurface pipes has been extensively studied in typical arid and semi-arid agricultural areas (Hetao Irrigation District). However, there are few studies on the improvement of subsurface pipe layout and the long-term soil salinization control in the process of leaching and soil amendment with subsurface pipes in this area. This study investigated the water and salt migration in the process of amending the heavy saline soil. Field experiments growing sunflowers and numerical model calculation were combined in this research. It was found in the field experiment that the salt concentration in the surface pipe drainage was positively correlated with the salt content in the soil and the depth of the pipe, while it was negatively correlated with the amount of irrigation water and the spacing of crops. Thus, the soil desalting rate (N) and salt control rate (SCR) were positively correlated with the depth of the pipe, and they were negatively correlated with the spacing. The leaching effect of irrigation would decrease when the soil salt content decreased. On the basis of field experiments, the DRAINMOD model and drainmod equation were used to calculate the water and salt migration in 38 different field plots during 2019 and 2020. When N was the same, the soil salinity in several plots with large burial depth could be controlled below the salt tolerance threshold of sunflowers during the growth period in the second year. The quantitative relationship between N and SCR, soil salt content before leaching, water amount of leaching, pipe spacing and buried depth was already established. These results can help develop strategies for desalination and salt control in the soil in the arid and semi-arid areas with the optimal layout of subsurface pipes.

Transient melt formation and its effect on conversion phenomena during nuclear waste vitrification – HT‐ESEM analysis

AbstractAlthough the vitrification of nuclear waste has a decades‐long history, numerous opportunities still exist to improve its efficiency and to increase the waste loading in glass. This is especially true for the vitrification of low‐activity waste (LAW), which has been historically treated by other immobilization technologies and is less mature than high‐level waste (HLW) vitrification. In this work, we address one of the least understood phenomena during the conversion of nuclear waste feeds to glass—the formation of molten salt and transient glass‐forming melt. Using high‐temperature environmental scanning electron microscopy (HT‐ESEM) in combination with X‐ray diffraction, thermogravimetry, and evolved gas analysis, we have analyzed the complex chemical reactions and phase transitions as they occur during melting of representative HLW and LAW melter feeds. We evaluated the compositions of amorphous phases and the fractions of salt components, and estimated the fractions of molten salt phases present in the feeds as a function of temperature. We show that the maximum fraction of molten salts is ∼4 % and ∼28 % during HLW and LAW feed melting, respectively, and discuss the possibility of molten salt migration in LAW feeds. We also argue that the presence of significant fractions of molten salt phase can hinder the retention of rhenium (and, hence, radioactive technetium), and discuss how the properties of molten salt phase and transient glass‐forming melt are related to primary foam formation and behavior. Finally, we summarize key unanswered questions requiring further research to increase the understanding of the conversion process and enhance the nuclear waste vitrification efficiency.

Understanding unsaturated sulfate saline soil in cold regions: A comprehensive hydraulic–thermal–air–salt–mechanical model with experimental research

The destruction of infrastructure built on saline soil in cold regions is closely related to water and salt migration, and soil deformation in foundations. Consequently, it is imperative to understand the mechanisms of heat and mass transfer, along with deformation in saline soil. Based on the unsaturated soil mechanics and porous media theory, a hydraulic–thermal–air–salt–mechanical (HTASM) coupled mathematical model for frozen unsaturated sulfate saline soil is proposed. The model incorporates the impact of ice-water phase change, sodium sulfate crystallization, and vapor flow on heat and mass transfer during the freezing process. Two parameters—salt crystallization pressure, and ice pressure—are introduced into the mechanical control equation to capture the effects of phase change on deformation. In addition, the relationship between the density of soil particles, water, ice and gas, and temperature and pressure is considered to reflect the dynamic change of density during freezing. Finally, the numerical simulation using the HTASM model is conducted and its efficacy is validated by comparing the numerical results with those obtained from indoor unidirectional freezing tests. The coupling effect of the HTASM model is revealed by analyzing the dynamic changes of temperature, water content, salt content, vapor flux and crystallization pressure in the soil column during freezing. The results show that the proposed HTASM model can well simulate the heat and mass transfer behavior in freezing unsaturated sulfate saline soil.