Soluble Salts Research Articles

Experimental investigation of the erodibility of soda saline-alkali soil under freeze-thaw cycle from a microscopic view

Soda saline-alkali soil, dominated by NaHCO3, has complex engineering properties that change with external water, heat, and salt, making it prone to water erosion. By destroying soil microstructure, freeze-thaw (F-T) action can potentially enhance soil erodibility and provide water erosion material. Therefore, this work examined the freeze-thaw erosive properties and microstructural evolution mechanisms of soda saline-alkali soil. Disintegration tests and a series of microscopic tests examined the impacts of freeze-thaw cycles (N = 0, 1, 5, 10, 30, 60) and soluble salt content (η = 0.4 %, 0.8 %, 1.2 %, 1.6 %, 2.0 %) on the soil erodibility index (disintegration rate). The results demonstrated that F-T action continued to weaken the disintegration resistance of the saline soil. Moreover, this trend relatively stabilized after 10 F-T cycles.Soluble salt content had a two-phase impact on the saline soil disintegration. Increased salt content below 0.8 % improved erosion resistance, but salt content above 0.8 % accelerated the soil erosion. According to the Gouy-Chapman diffuse double layer (DDL) theory, the variation in the thickness of DDL induced by higher sodium ion contents and lower sodium ionic valence were deemed as the main causes. When the salt content increased from 0.8 % to 2.0 %, the disintegration rate increased by 49.40–71.43 %. Microscopic results showed that sequential F-T cycles decreased intra-aggregate pores (<4 μm) and increased inter-aggregate pores (>4 μm). This mechanism was attributed to the unfrozen water migration and ice segregation due to the cryo-suction process during the freezing process. Correlation analysis indicated that soil microstructure with a bimodal characteristic dominated the erodibility index. The effect of F-T action on soil erodibility was more significant than the soluble salt content, with both impacted saline soil erodibility by affecting pore distribution characteristics and soil aggregate formation, respectively. These findings may assist soda saline-alkali soil salinity prevention and control of saline soil erosion in seasonally frozen regions globally.

Effects of Broccoli Rotation on Soil Microbial Community Structure and Physicochemical Properties in Continuous Melon Cropping

The limitations and weaknesses of continuous melon cropping have worsened in recent years. A melon–broccoli rotation can possibly alleviate the problems associated with melon monoculture; however, the underlying mechanisms and their impact on the rhizosphere’s soil microbial community remain unclear. Thus, high-throughput sequencing was used to evaluate the rhizosphere soil’s microbial community’s relative abundance and diversity under melon–broccoli rotation and continuous melon monoculture cropping systems. We found that relative fungal and bacterial diversity and richness increased while fungi relative abundances, such as Fusarium spp. were significantly decreased under broccoli rotation. During continuous cropping, enriched Acidobacteria and Streptomyces spp., Sphingomonas spp., and Pseudomonas spp. were identified, which play important roles in alleviating melon continuous cropping obstacles. The soil under continuous cropping was rendered acidic, underwent secondary salinization, rapidly accumulated soil organic carbon and nitrogen, and lost abundant phosphorus and potassium. In contrast, broccoli rotation partially mitigated these negative physicochemical responses. Redundancy analysis revealed that the soil pH, soil soluble salt content, and soil organic carbon were linked to structures of the soil bacterial and fungal community. Melon–broccoli rotation could effectively equilibrate the soil microenvironment and overcome the challenges and deficiencies associated with continuous melon cropping.

Molecular conformation and dilute solution properties of barley β-glucan: unveiling β-glucan as a highly flexible biopolymer under different processing conditions

BackgroundThe functional properties of food fluids containing hydrocolloids are influenced by temperature, soluble salts, pH and the presence of sugars. In this research, the properties of a dilute barley β-glucan (BBG) solution were evaluated in the presence of various factors. Different models were explored to determine the intrinsic viscosity of BBG.ResultsThe results indicated that the models of Higiro and Tanglertpaibul–Rao were more efficient in determining the intrinsic viscosity of BBG at different temperatures, different pH, the presence of sodium chloride, calcium chloride, and sucrose. Every 10 °C increase in temperature from 25 to 65 °C caused a decrease in intrinsic viscosity by 7.8, 10, 5.7 and 7.2%, respectively. In relation to the non-ionic structure of BBG, the presence of monovalent and bivalent salts had a negligible effect on reducing the intrinsic viscosity. The increase in pH from 3 to 7 caused a rise in intrinsic viscosity. But a further increase in pH, up to 9, caused a decrease in intrinsic viscosity. However, these changes were not significant and indicated that the non-ionic structure of BBG was independent of the pH. Since the constant b values of BBG were close to 1 at all temperatures, salt concentrations, different pH values and different sucrose concentrations, it can be assumed that the structure of BBG in the dilute range was close to the random coil conformation.ConclusionsThe values of flexibility index and activation energy for BBG were calculated as 789.52 and {0.65times 10}^{7} J/kmole, respectively, which indicated that this hydrocolloid was highly flexible in different environmental conditions and it was independent of the processing temperature. Therefore, BBG can be recommended as a natural thickener in food-related fluids.Graphical

Effect of POLY4 Application on the Growth and Yield of Groundnut (Arachis hypogaea L.)

Aim: To evaluate the effect of POLY4 Application on the Growth and Yield of Groundnut.&#x0D; Study Design: Randomized Block Design.&#x0D; Place and Duration of Study: Gungal Research Farm, ICAR-Central Research Institute for Dry land Agriculture, Hyderabad, India between June 2022 and October 2022.&#x0D; Methodology: A field experiment was conducted at Gungal Research Farm, ICAR-Central Research Institute for Dry land Agriculture, Hyderabad, and Telangana during the Kharif season of 2022 to the evaluate the Impact of POLY4 Application on the Growth and Yield of Groundnut. The experiment was assigned in ten treatments, laid out in Randomized Block design with three replications. The treatments were T1-Recommended NPK (20:40:50 kg ha-1) + gypsum @ 500 kg ha-1, T2-Recommended NP only, T3-Recommended NPK, T4-Recommended NP + 50% K through MOP, T5-Recommended NP + 100% of rec. K through Poly4, T6-Recommended NP + 100% of rec. K through Poly4 + gypsum @ 310 kg ha-1, T7-Recommended NP + 50% of rec. K through Poly4, T8-Recommended NP + 50% of rec. K through Poly4 + gypsum @ 310 kg ha-1, T9-Recommended NP + gypsum @ 500 kg ha-1 and T10-Control.&#x0D; Results: The application of Recommended NP(20:40 kg ha-1) + 100% of rec. K(50 kg ha-1) through POLY4 (T5) treatment resulted in a significant increase in both plant height and leaf area at vegetative (18.1 cm and 320.4 cm2 plant-1), at flowering (31.9 cm and 554.7 cm2 plant-1),at pegging (39.5 cm and 785.3 cm2 plant-1), at pod formation (48.5 cm and 1088.5 cm2 plant-1), and at the harvest (54.4 cm and 359.5 cm2 plant-1) respectively compared to the control. Significantly higher pod yield (1556 kg ha-1) was recorded under Recommended NP (20:40 kg ha-1) + 100% K (50 kg ha-1) through POLY4 (T5). The lower yield (844 kg ha-1) was recorded in control (T10).&#x0D; Conclusion: Polyhalite, also known as POLY4, is a highly effective fertilizer that provides potassium (K), sulfur (S), magnesium (Mg), and calcium (Ca) in a more efficient manner compared to equivalent soluble salts. Based on the findings of the current study, it can be concluded that application of 100% K through polyhalite (POLY4) along with recommended doses of nitrogen and phosphorus (20:40 kg ha-1) in sandy loam soil was the best performing treatment.

Molecular dynamics study of ion clustering in concentrated electrolyte solutions for the estimation of salt solubilities

Molecular dynamics study of ion clustering in concentrated electrolyte solutions for the estimation of salt solubilities

Propagation Methods and Mulching Modulate the Quantum Yield, Ionic Relations, and Production Components of Sour Passion Fruit under Salt Stress

In semiarid regions of Brazil, water and/or soil salinity is one of the limiting factors for sour passion fruit production. Low rainfall rates combined with edaphic conditions (high concentrations of soluble salts) intensify deleterious effects on plants. Thus, strategies that minimize the effects of salt stress, e.g., grafting with tolerant species and soil mulching, are extremely important to ensure the expansion of irrigated fruit farming in this region. From this perspective, this study aimed to evaluate the effect of grafting and mulching on the quantum yield, ionic relations, and fruit production of sour passion fruit irrigated with moderately saline water. The experiment was conducted under field conditions in split plots, in a 2 × (2 × 2) factorial arrangement to evaluate the combination of low and moderate salinity water (main plot) with the propagation method (seeds and grafting on P. cincinnata) and without and with plastic mulching (subplots), with four replications and three plants per plot. The ionic relations in passion fruit leaves were increased with the use of rootstocks and plastic mulching under irrigation with moderately saline water. The use of mulching increased the yield of photosystem II in sour passion fruit. The passion fruit plants propagated by seeds had 187.52% more fruits than those grafted onto P. cincinnata. The use of rootstocks with P. cincinnata in sour passion fruit restricted the uptake of Na and Cl but reduced fruit production.

Monitoring of Surface Water Quality in King Talal Dam Using GIS: A Case Study

King Talal Dam is the largest surface water reservoir in Jordan. Zarqa River and some springs are the major flow contributors to this dam. The other inflow comes in the form of effluents from Al-Samra, Baqa'a, and Jerash wastewater treatment plants, and industries located in Amman and Zarqa. These effluents dramatically deteriorate the water quality of the dam. This study applied Geographical Information System to monitor the temporal and spatial changes in the water quality of King Talal Dam. The parameters included toxicity and infiltration risks, clogging in irrigation systems (drip), soil degradation through soluble salt accumulation, and excessive nitrogen-associated issues. The study expanded from winter 2014 to summer 2016. The final integrated maps revealed two suitable and unsuitable classes for irrigation purposes. The study also provided essential information about the main water quality parameters and pollution sources such as EC, and E. coli. They were recorded throughout the study period in unsuitable zones whereas TSS and bicarbonate (HCO3-) were found in the spring of 2015 and spring of 2016, respectively. Autumn 2014 was found to be the worst season among all the study years. During that season, the unsuitable area expanded up to 93% of the total reservoir area. Then, the unsuitable zone reached up to 68.4% of the total area during the winter of 2016. The mapping results indicated that site 100 remained polluted during all the study seasons. This was expected as site 100 is in Zarqa River where Al-Samra and Jerash wastewater treatment plants are discharged.

Desalination by batch reverse osmosis (RO) of brackish groundwater containing sparingly soluble salts

Batch RO desalination is a new approach to high-recovery, energy-efficient desalination. So far, however, batch RO has been tested mostly with pure sodium chloride solutions. An important application of batch RO is desalination of brackish groundwater which, besides sodium chloride, contains sparingly soluble salts. In this experimental study of a batch RO system, we used simulated groundwater (with total dissolved solids ranging from 1180 to 3637 mg/L) following compositions of samples taken from a location in Egypt and a location in India. The groundwater contained high levels of salts which could be expected to cause scaling on the RO membrane surface. For example, the Langelier Saturation Index (LSI) for calcite reached 2.6 in the brine. Nonetheless, the system resisted scaling throughout >100 h of operation. Membrane permeability remained almost unchanged, as demonstrated by tests conducted before and after the experiments. Induction time calculations showed that salinity cycling did not fully explain the scaling inhibition. Other anti-scaling mechanisms – such as periodic flushing, osmotic backwash, and feed flow reversal – were also likely contributors. At recovery of 0.8, hydraulic specific energy consumption (SEC) was <0.5 kWh/m3 and close to that obtained with sodium chloride solution at equivalent osmotic pressure.

Status of Sulphur, Zinc and Boron in Onion Growing Soils of Dharwad Taluk, Karnataka, India

Survey was undertaken during rabi 2021-22, to study the sulphur, zinc and boron status in onion growing fields in selected villages of Dharwad taluk, Karnataka. One hundred surface soil samples were collected from selected ten villages of Dharwad taluk using GPS. The results revealed that soils were neutral to alkaline in reaction, low in total soluble salts, low to high organic carbon content, low in available nitrogen, medium in available phosphorus, potassium and sulphur and 49.00 and 77.00 per cent of the soils were deficient in DTPA extractable zinc and hot water soluble boron, respectively.

Mechanistic insights to the reversibility of membrane wetting in membrane distillation

Membrane wetting is an inevitable challenge in membrane distillation (MD). To overcome this challenge, a few dewetting techniques have been developed, but the reversibility of membrane wetting induced by various contaminants has not been well understood. Herein, we evaluate the reversibility of membrane wetting induced by different types of contaminants and elucidate the underlying mechanisms. From direct contact MD experiments and membrane wettability characterizations, membrane wetting induced by amphiphilic molecules, low-surface-tension liquids, and highly soluble salts can be easily reversed by 20-min DI water rinsing and oven drying, while to reverse membrane wetting induced by sparingly soluble salts, 3-h DI water rinsing and oven drying are required. Based on microscopic imaging and elemental mapping, the membrane wetting processes did not induce severe damage to membrane structure, and thus the hydrophobicity of the membrane can be restored after the contaminants were removed from the membrane. Furthermore, the mechanisms of the removal of different contaminants are elucidated. Specifically, after membrane rinsing and drying, the amphiphilic molecules automatically desorb from the dried membrane due to the disappearance of the underwater hydrophobic-hydrophobic interaction, while the low-surface-tension liquids leave the membrane pores because of evaporation. Additionally, during the membrane rinsing process, the highly soluble salts inside the membrane pores are dissolved, while the sparingly soluble salts detach from the membrane due to the hydrodynamic disturbance. The insights from this study shed lights on the development of effective dewetting techniques for hydrophobic membranes, which benefits not only MD but also membrane contactor applications.

Study on Shear Behavior and Mechanism Based on Shear Functional Unit of Loess Microstructure

The structural specificity and hydrological sensitivity of loess have a strong impact on its long-term stability and safety. This topic is being actively researched and focuses on the macromechanical behavior of the shear strength of loess disturbed and its micromechanisms from the perspective of the dry–wet cycle (especially involving soluble salt erosion). In this paper, the correlation between micro-structural shear functional units and macroscopic degradation behavior was established by combining the changes in physicochemical properties of mass loss, surface cracking, strength deterioration, and structural disturbance of the loess with scanning electron microscopy (SEM) microscopic images in different dry–wet cycles and different salt contents. Results revealed that with the increase in dry–wet cycles and salt content, the mass loss of soil deteriorated and the surface crack rate increased. The cohesion of soil showed an overall decreasing trend, which decreased more obviously in the early stage of the dry–wet cycle, followed by a slow decrease, and tended to be constant after nine dry–wet cycles. However, the internal friction angle increased and then decreased during the whole cycle, and its value generally changed little. According to the deterioration and decay of shear strength, it can be concluded that the structural disturbance of loess increased with the increase in dry–wet cycles and salt content. At the same time, further linear quantization fitting of the structural disturbance parameters showed that the structural parameters had a positive correlation with salt content and a power function with dry–wet cycles, where dry–wet cycles seemed to play a dominant role in the loess structural deterioration rather than salt content. The microscopic study demonstrates that the dry–wet cycles and salt content do not directly affect the cohesion and internal friction angle of soil but change the basic shear structural unit of aggregate and then cause an essential impact on c and φ, which in turn have an essential impact on soil strength attenuation. This paper not only helps to elucidate the essence of water–soil–salt structural interactions but also provides theoretical references for sustainable development research in environmental engineering, geological engineering, and other related fields.

Solubility of MoS2 and Graphite in Molten Salt: Flowers, Faceted Crystals, or Exfoliation?

2D materials are of interest in various applications such as energy conversion, storage, and sensing. These materials are prepared by bottom‐up or top‐down methods that are difficult to control and suffer from low yield. Synthesis in molten salt is suggested as an alternative in which the balance between exfoliation and solubility is explored. It is demonstrated that when a pellet of 2D material is insoluble in molten salt (graphite in any salt), it is exfoliated. For low solubility (MoS2 in NaCl/KCl), the 2D material nucleates and grows into a small flowerlike structure composed of thin MoS2 sheets through Ostwald ripening. For high solubility in the molten salt (MoS2 in CsCl), it forms larger flowers. Herein, the molten salt treatment of high and low surface area MoS2 (micron‐size particles and a single large pellet, respectively) is compared. The particles yielded facet MoS2 crystals through dissolution–nucleation–recrystallization process and the pellet yielded flowers. Herein, methods for synthesizing 2D materials with controllable size and shape are promoted by simple molten salt treatment that opens an avenue to the development of soluble (MoS2) and non‐soluble (graphite) materials with different morphologies in a simple and affordable way.

Scots Pine (Pinus sylvestris L.) Ecotypes Response to Accumulation of Heavy Metals during Reforestation on Chalk Outcrops

As objects for reforestation, the least studied are carbonate substrates, which have a number of specific features in terms of mineral composition, the exchange of nutrients, and biological activity. The use of biological preparations of a consortium of bacteria of the genus Bacillus and mycorrhizal fungi of the genus Glomus in growing seedlings of Scots pine (Pinus sylvestris L.) on carbonate substrates provides the metabolic products; soluble and microelement salts function as catalysts for chemical reactions of exudates and soil products; and a greater amount of plant heavy metals (HM) Cu, Zn, Cd, and Pb accumulate in the soil. Among HMs, the random factors most strongly determined an accumulation of Cd (the influence rate of random factors h2x = 34.6%) and Pb (the influence rate of random factors h2x = 21.7%) in the plants. A trend of all studied HMs higher uptake by the Cretaceous pine (Pinus sylvestris var. cretacea (Kalen.) Kom.) in comparison with the P. sylvestris ecotype is revealed. Against the biological preparation background of Biogor KM and MycoCrop®, a greater value of the HM’s biological absorption in comparison with the option without biological preparations is noted. This process occurs against a background of a significant increase in the nitrification capacity in the chalk fine-grained substrate (soil aggregates &lt; 1 mm in size), which is an indirect indicator of an increased intensity of microbiological processes. Spearman’s correlation was noted between the coefficient of accumulation of Cu, Zn, Cd, and Pb in the dry matter of Scots pine (P. sylvestris) seedlings and the nitrification capacity of substrate (rs = 0.610–0.744, p &lt; 0.05), as well as the relationship between the nitrification capacity index of substrate and the coefficient of biological absorption of copper, zinc, and cadmium (rs = 0.543–0.765, p &lt; 0.05). No relationship was found between the coefficient of biological absorption of lead and other soil chemical property indicators. HM absorption by plants was random. No correlations have been established between an accumulation of HMs and a content of total nitrogen, an absolute value of nitrate nitrogen, a humus content, or a pH. The significance of the work is the possibility of providing reliable reforestation with Scots pine (P. sylvestris) and Cretaceous pine (P. sylvestris var. cretacea) on the chalk outcrops using the biological preparations Biogor KM, MycoCrop®, and BGT* methodology and ensuring soil phytoremediation from HMs.

Self-Consistent Implementation of a Solvation Free Energy Framework to Predict the Salt Solubilities of Six Alkali Halides.

To assess the salt solubilities of six alkali halides in aqueous systems, we proposed a thermodynamic cycle and an efficient molecular modeling methodology. The Gibbs free energy changes for vaporization, dissociation, and dissolution were calculated using the experimental data of ionic thermodynamic properties obtained from the NBS tables. Additionally, the Marcus' and Tissandier's solvation free energy data for Li+, Na+, K+, Cl-, and Br- ions were compared with the conventional solvation free energies by substituting into our self-consistent thermodynamic cycle. Furthermore, Tissandier's absolute solvation free energy data were used as the training set to refit the Lennard-Jones parameters of OPLS-AA force field for ions. To predict salt solubilities, an assumption of a pseudo-solvent was proposed to characterize the coupling work of a solute with its environment from infinitely diluted to saturated solutions, indicating that the Gibbs energy change of solvation process is a function of ionic strength. Following the self-consistency of the cycle, the newly derived formulas were used to determine the salt solubilities by interpolating the intersection of Gibbs free energy of dissolution and the zero free energy line. The refined ion parameters can also predict the structure and thermodynamic properties of aqueous electrolyte solutions, such as densities, pair correlation functions, hydration numbers, mean activity coefficients, vapor pressures, and the radial dependences of the net charge at 298.15 K and 1 bar. Our method can be used to characterize the solid-liquid equilibria of ions or charged particles in aqueous systems. Furthermore, for highly concentrated strong electrolyte systems, it is essential to introduce accurate water models and polarizable force fields.

Comparative assessment of Ni–Co coatings obtained from a deep eutectic solvent, choline chloride-ethylene glycol, and water by electroplating

Alloy electroplating using deep eutectic solvents (DES), compared to aqueous electrolytes, has essential benefits in a wide potential range, the high solubility of metal salts (including chlorides and oxides), and an environmentally friendly alternative. This research aimed to compare the coatings obtained by electrolysis of the Ni–Co alloy conventionally from an aqueous solution against the electroplating obtained in 2:1 ethylene glycol-choline chloride. The electrochemical behavior was studied through potentiodynamic polarization kinetic analysis carried out complying with Abner’s rules for alloy deposits; hydrodynamic conditions were modified, keeping the temperature at 60 °C and the salt concentration in both baths constant. As a result, nickel electrolysis has been carried out successfully by taking advantage of the benefits of using DES in energy consumption with 80% efficiency compared to water as a solvent under the same conditions. The composition and morphology of Ni–Co alloy coatings were characterized by scanning electron microscopy (SEM/EDS), and corrosion resistance was investigated by potentiodynamic polarization and electrochemical impedance (EIS). Coatings were obtained for both electrolytic baths with a chemical composition within the range of the alloy but with a higher cobalt content in the deposits obtained in water; in contrast, the distribution of the Ni–Co alloy was more homogeneous with changes in morphology and crystallization in the deposits obtained from the DES bath. The coatings’ anti-corrosion performance showed that the Co content difference increases the corrosion resistance of the Ni–Co alloy obtained from aqueous electrolytes compared to deposits obtained from DES.

Study on the mechanism of preparing metallic iron from soluble anode

The optimization of the ironmaking process for the preparation of high-purity metallic iron has become an important part of the production of the iron and steel industry due to the increasing demand for steel in the modern industry. This article adopted the soluble anode molten salt electrolysis process to prepare a soluble anode with excellent conductivity by mixing Fe2O3 and C in a molar ratio of 1:3, sintering at 1073 K for 6 h. The metal iron was electrolytically deposited on the cathode by applying a constant current of 0.1 A for 6 h in the NaCl-CaCl2 molten salt system. The anode dissolution and cathode deposition mechanisms were analyzed based on the electrolysis U-t curve. The experimental results showed that the presence of C after sintering reduces the impedance value by reducing Fe2O3 to Fe3O4. During the electrolysis process, Fe2+ in Fe3O4 oxidized to Fe3+ and entered the molten salt, migrated to the vicinity of the cathode, and underwent the reduction process of Fe3+-Fe2+-Fe during the cathodic reduction process. The deposited Fe on the cathode exhibited a dendritic crystal structure with a purity of 99.51%.

Solubility of NaCl under anisotropic stress state.

Salt solubility is generally determined under isotropic stress conditions. Yet, in the context of salt weathering of porous media, mechanical constraints on the in-pore growth of salt crystals are likely to be orientation-dependent, resulting in an anisotropic stress state on the crystal. In this paper, we determine by molecular simulation the solubility of NaCl in water when the crystal is subjected to anisotropic stress. Such anisotropy causes the chemical potential of the crystal to be orientation-dependent, and proper thermodynamic formulation requires describing the chemical potential as a tensor. The solute and crystal chemical potentials are computed from free energy calculations using Hamiltonian thermodynamic integration, and the usual condition of solubility is reformulated to account for the tensorial nature of the crystal chemical potential. We investigate in detail how the uniaxial compression of the crystal affects its solubility. The molecular simulation results led to revisiting the Correns law under anisotropic stress. Regarding the solute, the non-ideal behavior of the liquid phase is captured using Pitzer's ion interaction approach up to high concentrations of interest for in-pore crystallization and beyond the concentrations addressed in the existing literature. Regarding NaCl crystals, the validity of the generalized Gibbs-Duhem equation for a tensorial chemical potential is carefully verified, and it is found that crystallization progresses almost orthogonally to the crystal surface even under high shear stresses. Comparing uniaxial and isotropic compression highlights the major differences in solubility caused by stress anisotropy, and the revisited Correns law offers an appropriate framework to capture this phenomenon.

Climatic effect from oyster reef restoration in Spartina alterniflora invaded intertidal mudflat: From the perspective of CH4 and N2O production

Spartina alterniflora is a dominant invasive species along the coast of China. A surprising phenomenon that the oyster reef formation is substituting the S. alterniflora invasion, was recently observed in the west coast of Bohai Bay, North China. As the intertidal mudflat ecosystem is critical for coastal blue carbon, this paper aims to evaluate the climatic effect of the alternation from the perspective of potential CH4 and N2O production. The sediment geochemical properties and potential CH4 and N2O productions were therefore measured in sediments dominated by Spartina alterniflora (SA), oyster reef (OR), mixture of S. alterniflora and oyster reef (SA-OR) and bare mudflat (BM) at an intertidal mudflat. Meanwhile, sediment microbial community structure and function genes were also determined utilizing metagenome high-throughput sequencing technology. Our results indicated that the formation of oyster reef in S. alterniflora invaded intertidal mudflat might slightly reduce the sediment potential CH4 production and enhance the sediment potential N2O production. The oyster reef formation could alter the community composition of methanogens and the abundance of functional genes in methanogenesis, and transform the main pathway from methylotrophic to hydrogenotrophic methanogenesis in surface sediments. Metagenome sequencing revealed that the oyster reef formation may promote nitrification, inhibit dissimilatory nitrate reduction (DNRA) and nitrate assimilation functions, and reduce the abundance of nosZ genes. Mantel analysis showed that pH, soluble salt and dissolved carbon (DC) were the most important factors influencing the composition of microbial community. In general, our results imply that the growth of oyster reef in the S. alterniflora invaded area has opposing effects from the prospective of the potential CH4 and N2O production.

Assessing a multi-method approach for dryland soil salinization with respect to climate change and global warming – The example of the Bajestan region (NE Iran)

Dryland soil salinization strongly affects soil properties, with severe consequences for regional ecology, agriculture and the aeolian dust dynamics. Given its climate-sensitivity it forms a serious environmental hazard, and to cope with this challenge during current global warming it needs to be better understood. The Bajestan Playa in the strongly salinization-affected Iranian drylands hosts several protected areas and forms an important regional dust source. Hence, soil salinization in this region affects local and regional ecosystems and societies, but was not systematically studied yet. Using an unprecedented comprehensive approach we systematically monitored regional soil salinity 1992–2021 using remote sensing as well as on-site field and laboratory measurements, and linked these with regional and global climatic data to understand (i) the spatio-temporal soil salinity dynamics, (ii) the impact of regional and global climate changes, and (iii) the potential of our approach for further soil salinity studies.Our annual time resolution over three decades provided significantly deeper and unprecedented insights into soil salinization: Both regional annual precipitation and temperature control soil salinity, but the latter responds to precipitation with time lags of up to two years and to higher temperatures without any time lag. This probably reflects the transport time of leached soluble salts from their sources following humid years. No systematic soil salinity changes were observed within the playa basin, but outside the basin soil salinity systematically increased. Whereas regional precipitation did not show a systematic trend during the last decades, regional temperature increased and was mostly correlated with the increasing GLOTI, POL and TSA climatic indices. Hence, given ongoing global warming a further increase of regional soil salinization should be expected, with serious consequences for saline dust emissions, the regional protected areas and climate-related migrations. Altogether, our multi-disciplinary pioneer study demonstrates a high future application potential also for other salinity-affected drylands, forming a base to deal with the consequences of ongoing global climate change.

Application of Desulphurized Gypsum with Straw to Improve Physicochemical Properties of Saline-alkali Land in Yellow River Delta

In order to explore the effect of combining straw and desulphurized gypsum on improving coastal saline-alkali soil, taking the alkaline saline soil in the Yellow River Delta as the research object, six treatments including the control (CK), desulphurized gypsum (DG), medium straw amount (MS), desulphurized gypsum+low straw amount (DGLS), desulphurized gypsum+medium straw amount (DGMS), and desulphurized gypsum+high straw amount (DGHS) were set up through a field location experiment. Combined with the aggregate classification method, the changes in bulk density, total porosity, pH, soluble salt content, microbial biomass carbon, dissolved organic carbon, new carbon, and aggregate organic carbon of coastal saline alkali soil under different treatments were compared. The results showed that the MS and DGHS treatments significantly reduced soil bulk density and increased soil total porosity, water content, and average weight diameter. The pH and exchange sodium percentage decreased significantly under all treatments, and there was no significant difference. DG treatment significantly reduced the soil sodium adsorption ratio. Compared with that in the MS treatment, the soil sodium adsorption ratio of DGLS, DGMS, and DGHS showed a further decreasing trend, with a decrease range of 57%-66%. Compared with MS, soil soluble Na+ decreased by 27.92%, 32.23%, and 20.15% under the DGLS, DGMS, and DGHS treatments, whereas the soil soluble Ca2+ and SO42- contents increased significantly. Compared with that in CK, all treatments could significantly reduce Cl- content, and there was no significant difference among all treatments. Compared with that in MS, microbial biomass carbon and dissolved organic carbon were significantly increased by 113% and 147% by DGMS and 22.81% and 28.24% by DGHS, respectively. The new carbon formation of DGLS, DGMS, and DGHS was 67%, 114%, and 175% higher than that of MS, respectively. The average size proportion of fine aggregates treated by DGLS, DGMS, and DGHS was 29.12% higher than that treated by MS. Straw returning and application of desulfurized gypsum increased the organic carbon content of coarse aggregates and fine aggregates in salinized soil. The average value of new carbon formation in coarse aggregates and fine aggregates treated by DGMS and DGHS was 233% and 142% higher than that treated by MS, respectively. Desulphurized gypsum applied to soil did not lead to soil heavy metal pollution, and the soil heavy metal content of different treatments was lower than the secondary standard of the soil environmental quality standard. These results can provide scientific basis for the improvement and utilization of coastal saline-alkali soil and the comprehensive utilization of industrial and agricultural wastes in the Yellow River Delta.