Initial Precipitation Research Articles

Investigating the Mechanisms Impacting Soil Ca, Mg, and Na in Wastewater Land Application Systems Using Machine Learning Models

ABSTRACTWastewater land application is a widely accepted solution for addressing global water crisis, particularly in arid and semiarid regions, but it may cause soil Ca, Mg, and Na accumulation and result in soil degradation. The objective of this study was to investigate the underlying mechanisms impacting soil Ca, Mg, and Na in wastewater land application systems using tree‐based machine learning models. Using data collected from previous field studies, decision tree (DT), random forest (RF), and extreme gradient boosting decision trees (XGBoost) models were developed to predict soil Ca, Mg, and Na in wastewater land application systems. XGBoost models showed the best performance, with R2 and RMSE values of 0.999 and 18.9 mg/kg, 0.999 and 3.2 mg/kg, and 0.912 and 104 mg/kg on the training data and 0.989 and 345 mg/kg, 0.925 and 56.1 mg/kg, and 0.908 and 112 mg/kg on the test data for soil Ca, Mg, and Na prediction, respectively. Permutation importance analysis reveals that initial soil Ca and electrical conductivity (EC) and total irrigation amount, initial soil Mg, total precipitation and initial soil EC, and initial soil Na, total irrigation amount and wastewater Na were the top three predictive variables for soil Ca, Mg, and Na, respectively. Partial dependence analysis demonstrates how soil Ca, Mg, and Na changed with the predictive variables, and indicates that wastewater irrigation caused soil Ca, Mg, and Na accumulation. This study highlights the need for sustainable wastewater land application management to control soil sodium adsorption ratio and mitigate the risks of land degradation.

A Kinetic Model for Oxide–Carbonitride Inclusion Heterogeneous Nucleation and Precipitation during Superalloy Solidification

Complex oxide–carbonitrides (MgO-Ti(CN), Al2O3-Ti(CN), and MgO·Al2O3-Ti(CN)) are the most common non-metallic inclusions presented in cast and wrought superalloys. In this work, a coupled kinetics model was proposed to predict the complex oxide–carbonitride inclusion’s precipitation behavior during the solidification of superalloys. This model takes into account thermodynamics, micro-segregation, heterogeneous nucleation in the inter-dendritic liquid, and growth controlled by the diffusion of solute elements and kinetics of interfacial reaction. The results demonstrated that both the cooling rate and nitrogen content take significant effects on the final size of complex oxide–carbonitride inclusions, as the former controls the total growth time and the latter determines the initial precipitation temperature. In comparison, the particle size of primary oxides shows a negligible impact on the final size of complex inclusions. The practice of an industrial vacuum arc remelting confirmed that the inclusion size variation predicted by the present model is reasonably consistent with the experimental results.

Development of a Hydrometallurgical Process for the Extraction of Cobalt, Manganese, and Nickel from Acid Mine Drainage Treatment By-Product

Critical minerals (CMs) are pivotal in modern industries, such as telecommunications, defense, medicine, and aerospace, contributing significantly to regional and global economic growth. However, the reliance on external sources for 26 out of 50 identified CMs raises concerns about supply chain vulnerabilities. To address this, the research focused on developing a hydrometallurgical process for extracting cobalt, manganese, and nickel from acid mine drainage (AMD) treatment by-products, emphasizing the need to diversify CM supply chains within the United States (US). A solution composed of an REE solvent extraction raffinate loaded with cobalt, manganese, nickel, and various impurity metals was utilized as a feedstock in this study. The developed hydrometallurgical process involved initial sodium hydroxide precipitation to remove impurities like aluminum and iron from an SX raffinate solution generated during the extraction of rare earth elements (REEs). Precipitation stages were performed in a pH region ranging from 2 to 12 to identify the optimum pH values, achieving a tradeoff between recovery and impurity removal. A subsequent precipitation process at pH 5–10 yielded a product rich in CMs, such as manganese, cobalt, and nickel. Further separation steps involved nitric acid washing, resulting in a Mn product with a purity of 47.9% by weight and a solution with extractable concentrations of cobalt and nickel. Stagewise precipitation with sodium sulfide subsequently produced three solid products: cobalt and nickel product at pH 1–5, manganese product at pH 5–10, and magnesium at pH 10–12. The study also explored other separation approaches, including solvent extraction, to enhance the separation of nickel from cobalt. Overall, the developed hydrometallurgical process generated the following products with varying degrees of purities: cobalt (9.92 wt.%), nickel (14 wt.%), manganese (47.9 wt.%), and magnesium (27.49 wt.%). This research aimed to contribute to the sustainable extraction of CMs from secondary sources, reducing the US’ reliance on imports and promoting a more resilient supply chain for these crucial elements.

Multilayer Ge8Sb92/Ge2Sb2Te5 thin films: unveiling distinct resistance states and enhanced performance for phase change random access memory

This study investigates the phase-change properties of [Ge8Sb92 (25 nm)-Ge2Sb2Te5 (25 nm)]1 multilayer thin films, elucidating three distinct resistance states originating from two structural transitions: initial Sb precipitation and Ge2Sb2Te5-FCC crystallization, followed by Ge2Sb2Te5-FCC to Ge2Sb2Te5-HEX transformation with additional Sb precipitation. The phase transitions induce two abrupt changes in resistance at temperatures of 169.8 °C and 197.7 °C, respectively, with corresponding data retention temperatures of 97 °C and 129 °C, indicating robust thermal stability. The [Ge8Sb92 (25 nm)-Ge2Sb2Te5 (25 nm)]1-based phase change random access memory (PCRAM) device demonstrates reversible switching characteristics and multi-level storage capabilities within 20 ns, showcasing enhanced phase-change speed and storage density. In summary, [Ge8Sb92(25 nm)-Ge2Sb2Te5(25 nm)]1 demonstrates enhanced thermal stability, swift phase transition, and increased storage density relative to conventional Ge2Sb2Te5, establishing it as a promising new phase-change material for PCRAM applications.

The influence of microstructure on the oxidation behavior of a TaTiCr refractory complex concentrated alloy

This work explores the effect of microstructure on the oxidation behavior of an equiatomic TaTiCr RCCA after 24 h of exposure at 800°C, 1000°C, 1200°C, and 1400°C. Two microstructural conditions, both containing a bcc matrix with C15 Laves precipitates, with one condition having coarser precipitates (∼10.9 µm diameter) and one condition having finer precipitates (∼2.9 µm diameter) were studied. At all oxidation temperatures except 800°C, the finer-scale (TaTiCr-F) condition experienced more rapid oxidation kinetics, higher mass gains, and thicker oxide scales and internal reaction zones. However, at 800°C, the microstructure containing coarser precipitates (TaTiCr-C) formed a thicker oxide scale. Continuous, protective Cr2O3 layers were only observed in the coarse precipitate condition and correlations between Cr2O3 layer thickness, subsequent formation of complex refractory oxides, and the initial Laves precipitate size are described. It is proposed that the formation of continuous Cr2O3 is highly dependent on the size and distribution of the Cr-rich Laves phase and only mildly dependent on phase fraction. Oxidation mechanisms for each condition are discussed relative to the initial microstructures, observed oxide species, and related alloy systems.

Effect of B2O3 on the viscosity, structure and crystalline phase of CaO–MgO–Al2O3–SiO2–MnO-based high alumina slags

The effects of B2O3 on viscosities, structures and phase transitions of CaO–MgO–Al2O3–SiO2–MnO-(0-8.0 wt%)B2O3 slags were investigated in this work. From the viscosity experimental results, the slag viscosities declined and the Eη decreased from 205.19 to 175.95 kJ/mol with the addition of B2O3 in slags from 0 to 8.0 wt%. From the structure analysis by using FTIR and XPS, B2O3 entered into the silicate network to increase the slag polymerization degree, while the formation of simple two-dimensional BO3 trihedral units could significantly decline the symmetry and stability of the structure. The effects of decreasing the network stability and forming low-melting eutectics were more dominated than the effects of increasing the structure polymerization degree, which could reduce the slag viscosity. Furthermore, adding B2O3 could decrease the slag initial precipitation temperature and change the primary crystal phase of the slag from melilite to spinel. The comprehensive effects of reducing the slag structure stability and decreasing the influence of solid phase on viscosity eventually resulted in the improvement of the slag fluidity.

Slip and stress in block-in-matrix shear zones: 1. microstructure and mineralogy of a serpentine-filled dilational jog

We document the structural setting, microstructure, and mineralogy of a crack-seal-type dilational jog that developed in the stepover between two faults cutting through a phacoid of massive serpentinite, itself embedded within a serpentinite shear zone at the base of the Dun Mountain Ophiolite, New Zealand. Our outcrop and microstructural measurements allow us to constrain the boundary conditions for a numerical model (part 2) that quantitatively explores the relationships between stress, fault slip, and incremental cracking in block-in-matrix shear zones. The dilational jog is c. 3 cm wide and contains hundreds of crack-seal bands, each c. 20–30 μm wide. Internally, the jog comprises two mineralogically distinct crack-seal domains: serpentine-only domains and serpentine-andradite garnet domains. Additionally, individual crack-seal bands have a double-layer structure: in serpentine-only domains each band comprises a thin (<2 μm) layer of chrysotile and a thicker layer (c. 25 μm) of polygonal serpentine/lizardite, whereas each band in serpentine + andradite domains comprises a thinner (c. 5 μm) layer of microcrystalline andradite and a thicker layer (c. 15 μm) of polygonal serpentine/lizardite. Micro-CT analysis shows that the serpentine + andradite domains have conic or ellipsoidal shapes with long axes subparallel to the inferred jog opening direction, and that andradite is smeared along micro-transform surfaces inside the jog. Our conceptual microstructural model invokes jog formation during progressive serpentinization of the host rock. Incremental crack opening along the jog-wall rock interface promotes relatively rapid initial precipitation of chrysotile or andradite at high fluid:rock ratios. As cracks fill and pressure re-equilibrates, relatively slow growth of polygonal serpentine/lizardite is favoured until the cracks are sealed and the cycle repeats. Our observations suggest that the precipitation of andradite (instead of chrysotile) was controlled both by structural boundaries within the jog (e.g., micro-transform surfaces) and by local element transport (e.g., Ca from serpentinizing clinopyroxene grains in the host rocks) to patches of the crack wall.

Freeze-thaw characteristics and deformation monitoring of topsoil in highland pastoral areas under the influence of snow accumulation

Soil freeze–thaw processes and snowmelt infiltration have a significant impact on the hydrological cycle and ecosystem productivity in alpine pastoral areas. To investigate the driving mechanism of snow on soil freeze-thaw processes, a meteorological station was established in the southern part of Namatso Lake, Tibet to collect environmental data. The study included analyzing the relationship between soil temperature and humity, as well as assessing soil freeze-thaw characteristics and the evolution of soil frost heave over time. The freeze-thaw frequency was significantly 43% lower at the surface soil, and the freeze-thaw intensity decreased when the ground was snow-covered. During the initial freezing period, precipitation and soil humidity remain relatively low, and soil moisture decreases linearly with decreasing soil temperature, which occurs in the phenomenon of soil freeze-shrink. During the initial thawing period, snowmelt infiltration impacts soil humidity, and soil frost heave increases logarithmically, reaching a maximum of 5.2 mm, driven by freeze-thaw. Soil moisture decreases under topsoil evaporation in the later stage and again follows a linear trend with the soil temperature. This study not only reveals the correlation between soil temperature and humidity during different freeze-thaw periods but also enhances the understanding of soil deformation patterns under the influence of snow accumulation.

PRECIPITATION OF ARSENIC FROM THERMAL WATER

The presented scientific research reveals the results of experiments on the precipitation of arsenic in the form of sulfide (As2S3) from the Daridag thermal water using sodium sulfide as a reagent. The main factors impacting the precipitation of the As2S3 compound were determined: the amount of precipitant (Na2S), the ratio of solid and liquid phases (S:L), pH of the initial solution, precipitation time and temperature, also optimal parameters were obtained. According to the results obtained, the yield during precipitation of arsenic tri-sulfide from from thermal water under certain temperature conditions (t=30-450С, pH=1-2; S:L - 1:1000; = 30-50 min.) were 99.6 %. The properties of the samples were studied by physicochemical research methods (X-Ray, SEM/EDS). X-ray phase analysis showed that the sediment sample obtained under these conditions is X-ray amorphous. The composition and morphology of the obtained sample was confirmed by scanning electron microscopy and spectroscopy (SEM/EDS)

Hydrometallurgical Method of Producing Lithium Perrhenate from Solutions Obtained during the Processing of Li-Ion Battery Scrap

The work presents the research results regarding the development of an innovative technology for the production of lithium perrhenate. The new technology is based entirely on hydrometallurgical processes. The source of lithium was solutions created during the processing of Li-ion battery masses, and the source of rhenium was perrhenic acid, produced from the scraps of Ni-based superalloys. The research showed that with the use of lithium carbonate, obtained from post-leaching solutions of Li-ion battery waste and properly purified (by washing with water, alcohol, and cyclic purification with CO2), and perrhenic acid, lithium perrhenate can be obtained. The following conditions: room temperature, time 1 h, 30% excess of lithium carbonate, and rhenium concentration in the acid from 20 g/dm3 to 300 g/dm3, allowed to produce a compound containing a total of 1000 ppm of metal impurities. The developed technology is characterized by the management of all aqueous waste solutions and solid waste and the lack of loss of valuable metals such as rhenium and lithium after the initial precipitation step of lithium carbonate.

Borax preparation from Na-B-Si-containing solution by carbonation and multi-step crystallization

The Na-B-Si-containing solution was derived from ludwigite ore through a two-step process involving soda-ash roasting and subsequent grind-leaching. This study employed a carbonation-crystallization approach to comprehensively utilize the valuable components in the solution, aiming to produce borax while simultaneously generating sodium carbonate and silica. The initial carbonation precipitation achieved a high desilication ratio of 95.54 % through nano-sized silica particle formation. Meanwhile, the boron conversion ratio reached 94 %, with negligible boron loss due to efficient metaborate-to-borate transformation. To guide the crystallization separation of Na2CO3 and Na2B4O7, phase diagrams of the ternary system (Na2CO3 + Na2B4O7 + H2O) were experimentally constructed at 308.15 k and 333.15 k. Crystallization was then conducted at 278.15 K for 2 h, yielding a Na2B4O7·10H2O product with 96.45 % purity. The remaining filtrate was evaporated and crystallized to obtain the Na2CO3 product, which can be reused in the previous roasting process.

Purification of Anti-Mycobacterium tuberculosis MPT64 Immunoglobulin-Y from Egg-Yolk Supernatant Using Thiophilic Adsorption Chromatography

The significance of immunoglobulin Y (IgY) as a particular antibody equal to mammalian IgG is well understood. However, due to a lack of reliable purification procedures, producing highly pure IgY remains problematic. In this study, we aimed to optimize the recovery of pure IgY anti-MPT64 using thiophilic adsorption chromatography. The purification of IgY anti-MPT64 was achieved by initial PEG lipid precipitation, then an optimized purification by varying the gradient concentration of elution buffer into five steps gradient (0-20, 20-40, 40-60, 60-80, and 80-100%v/v) for three injection column volume (CV) each and two steps gradient (0-50 and 50-100%v/v) in eight CV for each concentration. The obtained IgY was characterized by SDS-PAGE and dot-blot then determined its content levels using the Lowry method. The results showed that the five steps gradient purification was found to provide a better purity level of IgY than the two steps gradient. However, the IgY content obtained in the two steps gradient purification (2.2632± 0.011 mg/mL) was higher than the five steps gradient purification (1.35482 ± 0.023 mg/mL). Nevertheless, both purified IgY results can recognize MPT64 protein through a dot blot test. Therefore, it can be summarized that thiophilic adsorption chromatography with five steps gradient of purification was an efficient process to obtain a higher purity of IgY anti-MPT64, especially to be targeted as a diagnostic kit component for MPT64 detection.

Biotrapping Ureolytic Bacteria on Sand to Improve the Efficiency of Biocementation.

Microbially induced calcium carbonate precipitation (MICP) has emerged as a novel technology with the potential to produce building materials through lower-temperature processes. The formation of calcium carbonate bridges in MICP allows the biocementation of aggregate particles to produce biobricks. Current approaches require several pulses of microbes and mineralization media to increase the quantity of calcium carbonate minerals and improve the strength of the material, thus leading to a reduction in sustainability. One potential technique to improve the efficiency of strength development involves trapping the bacteria on the aggregate surfaces using silane coupling agents such as positively charged 3-aminopropyl-methyl-diethoxysilane (APMDES). This treatment traps bacteria on sand through electrostatic interactions that attract negatively charged walls of bacteria to positively charged amine groups. The APMDES treatment promoted an abundant and immediate association of bacteria with sand, increasing the spatial density of ureolytic microbes on sand and promoting efficient initial calcium carbonate precipitation. Though microbial viability was compromised by treatment, urea hydrolysis was minimally affected. Strength was gained much more rapidly for the APMDES-treated sand than for the untreated sand. Three injections of bacteria and biomineralization media using APMDES-treated sand led to the same strength gain as seven injections using untreated sand. The higher strength with APMDES treatment was not explained by increased calcium carbonate accrual in the structure and may be influenced by additional factors such as differences in the microstructure of calcium carbonate bridges between sand particles. Overall, incorporating pretreatment methods, such as amine silane coupling agents, opens a new avenue in biomineralization research by producing materials with an improved efficiency and sustainability.

Reducing rare earth loss by adding acetic acid in the aluminum removal process of rare earth leaching solution

The ionic-type rare earth ore, abundant in medium and heavy rare earth elements, is a strategic mineral resource. The removal of aluminum from ionic rare earth leaching solution results in over 8% loss of rare earths. Preliminary research has found that adding acetic acid (HAc) during aluminum removal process can effectively reduce the loss of rare earth elements. In this paper, through the calculation of the species distribution in the La2(SO4)3-Al2(SO4)3-HAc-H2O system, it is found that HAc forms an AlOH-Ac+ complex with aluminum ions, with a proportion of up to 70%, which will increase the initial precipitation pH of aluminum hydroxide. Furthermore, HAc and lanthanum form a LaAc2+ complex, and the proportion can reach more than 20%. Moreover, the zeta potential, FT-IR, and XPS tests of aluminum hydroxide, obtained by neutralization precipitation, revealed that the complexation of HAc and aluminum can reduce the precipitation rate of aluminum hydroxide, so that its particle size increases, the specific surface area decreases, and the van der Waals force adsorption sites are reduced. HAc can be chemically adsorbed on aluminum hydroxide, thereby increasing the zeta potential of aluminum hydroxide and ultimately reducing its electrostatic adsorption effect on rare earths. Additionally, the complexation of HAc and rare earth elements can reduce the local supersaturation of rare earth hydroxides and decline the coprecipitation of rare earth elements. Finally, under a precipitation endpoint pH of 5.2, HAc concentration of 0.006 mol/L, aluminum concentration of 0.2 g/L, rare earth concentration of 0.8 g/L, magnesium ion concentration of 0.5 g/L and magnesium oxide slurry concentration of 0.45 mol/L, the aluminum removal efficiency obtained with rare earth leaching solution reached 98.47%, and the rare earth loss efficiency was 2.62%. Compared with the control, the rare earth loss efficiency was reduced by 5.59%. This paper provides guidance for the efficient and green development of ionic-type rare earth ore.

Multivariate regression analysis of factors regulating the formation of synthetic aluminosilicate nanoparticles.

Interest is growing in nanoparticles made of earth abundant materials, like alumino(silicate) minerals. Their applications are expanding to include catalysis, carbon sequestration reactions, and medical applications. It remains unclear, however, what factors control their formation and abundance during laboratory synthesis or on a larger industrial scale. This work investigates the complex system of physicochemical conditions that influence the formation of nanosized alumino(silicate) minerals. Samples were synthesized and analyzed by powder X-ray diffraction, in situ and ex situ small angle X-ray scattering, and transmission electron microscopy. Regression analyses combined with linear combination fitting of powder diffraction patterns was used to model the influence of different synthesis conditions including concentration, hydrolysis ratio and rate, and Al : Si elemental ratio on the particle size of the initial precipitate and on the phase abundances of the final products. These models show that hydrolysis ratio has the strongest control on the overall phase composition, while the starting reagent concentration also plays a vital role. For imogolite nanotubes, we determine that increasing concentration, and relatively high or low hydrolysis limit nanotube production. A strong relationship is also observed between the distribution of nanostructured phases and the size of precursor particles. The confidences were >99% for all linear regression models and explained up to 85% of the data variance in the case of imogolite. Additionally, the models consistently predict resulting data from other experimental studies. These results demonstrate the use of an approach to understand complex chemical systems with competing influences and provide insight into the formation of several nanosized alumino(silicate) phases.

Stress sensitivity of permeability in high-permeability sandstone sealed with microbially-induced calcium carbonate precipitation

Microbially induced carbonate precipitation (MICP) catalyzed by S. pasteurii has attracted considerable attention as a bio-cement that can both strengthen and seal geomaterials. We investigate the stress sensitivity of permeability reduction for the initially high-permeability Berea sandstone (initial permeability ∼110 mD) under various durations of MICP-grouting treatment. The results indicate that after 2, 4, 6, 8 and 10 cycles of MICP-grouting, the permeabilities decrease incrementally by 87.9%, 60.9%, 38.8%, 17.3%, and then 5.4% compared to the pre-grouting condition. With increasing the duration of MICP-grouting, the sensitivity of permeability to changes in stress gradually decreases and becomes less hysteretic. This stress sensitivity of permeability is well represented by a power-law relationship with the coefficients representing three contrasting phases: an initial slow reduction, followed by a rapid drop, culminating in an asymptotic response. This variation behavior is closely related to the movement and dislocation of the quartz framework, which is controlled by the intergranular bio-cementation strength. Imaging by scanning electron microscopy (SEM) reveals the evolution of the stress sensitivity to permeability associated with the evolving microstructures after MICP-grouting. The initial precipitates of CaCO3 are dispersed on the surfaces of the quartz framework and occupy the pore space, which is initially limited in controlling and reducing the displacement between particles. As the precipitates continuously accumulate, the intergranular slot-shaped pore spaces are initially bonded by bio-CaCO3, with the bonding strength progressively enhanced with the expanding volume of bio-cementation. At this stage, the intergranular movement and dislocation caused by compaction are reduced, and the stress sensitivity of the permeability is significantly reduced. As these slot-shaped pore spaces are progressively filled by the bio-cement, the movement and dislocation caused by compaction become negligible and thus the stress sensitivity of permeability is minimized.

In Situ Liquid Cell Transmission Electron Microscopy Study of Studtite Particle Formation and Growth via Electron Beam Radiolysis.

This study presents in situ observations of studtite (UO2O2(H2O)2·2H2O) crystal growth utilizing liquid phase transmission electron microscopy (LP-TEM). Studtite was precipitated from a uranyl nitrate hexahydrate solution using hydrogen peroxide formed by the radiolysis of water in the TEM electron beam. The hydrogen peroxide (H2O2) concentration, directly controlled by the electron beam current, was varied to create local environments of low and high concentrations to compare the impact of the supersaturation ratio on the nucleation and growth mechanisms of studtite particles. The subsequent growth mechanisms were observed in real time by TEM and scanning TEM imaging. After the initial precipitation reaction, a post-mortem TEM analysis was performed on the samples to obtain high-resolution TEM images and selected area electron diffraction patterns to investigate crystallinity as well as energy-dispersive X-ray spectroscopy spectra to ensure that studtite was produced. The results reveal that studtite particles form through various mechanisms based on the concentration ratio of uranyl to H2O2 and that studtite is initially produced through an amorphous intermediary prior to formation of the crystalline material commonly reported in the literature.

Estimating multi-scale irrigation amounts using multi-resolution soil moisture data: A data-driven approach using PrISM

Irrigated agriculture is the primary driver of freshwater use and is continuously expanding. Precise knowledge of irrigation amounts is critical for optimizing water management, especially in semi-arid regions where water is a limited resource. This study proposed to adapt the PrISM (Precipitation inferred from Soil Moisture) methodology to detect and estimate irrigation events from soil moisture remotely sensed data. PrISM was originally conceived to correct precipitation products, assimilating Soil Moisture (SM) observations into an antecedent precipitation index (API) formula, using a particle filter scheme. This novel application of PrISM uses initial precipitation and SM observations to detect instances of water excess in the soil (not caused by precipitation) and estimates the amount of irrigation, along with its uncertainty. This newly proposed approach does not require extensive calibration and is adaptable to different spatial and temporal scales. The objective of this study was to analyze the performance of PrISM for irrigation amount estimation and compare it with current state-of-the-art approaches. To develop and test this methodology, a synthetic study was conducted using SM observations with various noise levels to simulate uncertainties and different spatial and temporal resolutions. The results indicated that a high temporal resolution (less than 3 days) is crucial to avoid underestimating irrigation amounts due to missing events. However, including a constraint on the frequency of irrigation events, deduced from the system of irrigation used at the field level, could overcome the limitation of low temporal resolution and significantly reduce underestimation of irrigation amounts. Subsequently, the developed methodology was applied to actual satellite SM products at different spatial scales (1 km and 100 m) over the same area. Validation was performed using in situ data at the district level of Algerri-Balaguer in Catalunya, Spain, where in situ irrigation amounts were available for various years. The validation resulted in a total Pearson’s correlation coefficient (r) of 0.80 and a total root mean square error (rmse) of 7.19 mm∕week for the years from 2017 to 2021. Additional validation was conducted at the field level in the Segarra-Garrigues irrigation district using in situ data from a field where SM profiles and irrigation amounts were continuously monitored. This validation yielded a total bi-weekly r of 0.81 and a total rmse of −9.34 mm∕14-days for the years from 2017 to 2021. Overall, the results suggested that PrISM can effectively estimate irrigation from SM remote sensing data, and the methodology has the potential to be applied on a large scale without requiring extensive calibration or site-specific knowledge.

Influence of Si and Mo on the Sigma-Phase Precipitation in S32750 Super Duplex Stainless Steel Slab

In this study, we investigated the effect of Si and Mo on the sigma-phase precipitation in S32750 super duplex stainless steel slab. The activity for Mo with increasing Si and Mo was calculated by the Wagner formula, and the equilibrium solidification phase diagrams of S32750 duplex stainless steels with different Si and Mo contents were calculated using the thermo-calc software. The sigma phase precipitated mainly at ferrite/austenite phase boundaries and grew up towards the interior of ferrite phase in S32750 SDSS slab. The area fraction and size of the sigma phases significantly increased with increasing Mo content and Si content. Also, the increment in Mo and Si content affected the Mo concentration in sigma phase. The sample（Mo:3.4%,Si：0.3%） had a lowest sigma-phase area fraction of 2.84% and had lowest Mo content in σ phase.The calculation results showed that the increase of Mo and Si content increased the initial precipitation temperature and maximum precipitation amount of σ phase in S32750 SDSS equilibrium phase diagram. The activity of Mo also increased with increasing Si content and Mo content. That is, Mo and Si elements promoted the precipitation of σ phase.

Unraveling mechanisms underlying effects of wetting–drying cycles on soil respiration in a dryland

Rewetting of dry soils usually stimulates soil carbon (C) emission, a phenomenon known as the Birch effect. Soil C cycling in drylands, which store approximately one third of terrestrial soil organic C (SOC), is strongly affected by wetting–drying cycles. However, the physical, chemical, and biological mechanisms that link rewetting cycles with dryland soil C cycling have not been comprehensively studied, nor do we understand how these mechanisms interact with each other. Here, we conducted a dryland soil incubation experiment manipulating four factors related to global change (soil moisture content, soil moisture variability, C availability, and prior warming) in a factorial design. The experiment was divided into two periods: a rewetting period consisting of six 14-d wetting–drying cycles; and a recovery period lasting 28 days during which soil moisture content was held stable, allowing for examination of the legacy effects of the wet-dry cycles. Rewetting cycles decreased soil aggregate stability under some conditions, but their effects on soil microbial biomass and fungal communities, soil enzyme activities, soil priming, and soil dissolved C were not significant. We found lower average soil respiration under the wetting–drying treatment than the stable soil moisture treatment, and Birch effects were observed, but only under some conditions. This was probably because moisture variability exacerbated soil microbial metabolic stress, which showed itself as oxygen limitation during the initial precipitation pulse and as water limitation during soil drying. Notably, respiration rates remained low even after moisture fluctuations ceased, suggesting a legacy effect of rewetting cycles on dryland microbial communities. Overall, rewetting inhibited aggregate formation (physical mechanism), and suppressed soil respiration by inducing soil microbial metabolic stress (biological mechanism), ultimately leading to lower soil C loss under rewetting. Our findings indicate that Birch effects are mediated by the magnitude of moisture variability, the availability of C, and the degree of physiological stress microbes experience.