Initial Water Content Research Articles

Timing of Volatile Degassing From Hydrous Upper‐Crustal Magma Reservoirs With Implications for Porphyry Copper Deposits

AbstractThe timing and duration of volatile generation from crystallizing magma reservoirs and fluid release across the magmatic‐hydrothermal interface depend on complex coupled interactions controlled by non‐linear, dynamic properties of magmas, rocks and fluids. Understanding these mechanisms is essential to explain the rare formation of economic porphyry copper deposits. For this study, we further developed a coupled numerical model that can simultaneously resolve magma and hydrothermal flow by introducing a description of fluid transport within the magma reservoir and volatile release to the host rock. Our simulations use realistic magma properties derived from published experimental and modeling studies and cover different magma compositions and water contents. We show that magma convection at melt‐dominated states leads to homogenization, which delays fluid release and promotes a rapid evolution toward a mush state. The onset of magmatic volatile release can be near‐explosive with a tube‐flow outburst event lasting <100 years for high initial water contents of >3.5 wt% H2O that could result in the formation of hydrothermal breccias and vein stockworks or trigger eruptions. This event can be followed by sustained fluid release at moderate rates by volatile flushing caused by magma convection. Subsequent fluid release from concentric tube rings by radial cooling of non‐convecting magma mush with a volume of ∼100 km3 at ∼5 km depth is limited to remaining water contents of ∼3.1 wt% H2O and lasts 50–100 kyr. Ore formation from hydrous magmas may thus involve distinct phases of volatile release.

A comparison of soil water infiltration models of moistube irrigation

As a water-saving method, moistube irrigation has been widely used. To ensure the effectiveness of moistube irrigation the development of an infiltration prediction model under moistube irrigation based on the interaction of multiple factors is required. In this paper, soil water infiltration tests with different bulk densities (1.2 g/cm³, 1.3 g/cm³, and 1.4 g/cm³) and textures (loamy sand, sandy loam, and clay loam) under different pressure heads (1 m, 1.5 m, and 2 m) were designed, and the test data were analyzed by gray correlation theory. The pressure head, bulk density, clay content, silt content, sand content, and initial water content were determined as input variables, and the model structure was composed with two parameters of Kostiakov's model as output variables. Then, the genetic algorithm was used to optimize the back propagation neural network and the particle swarm algorithm to optimize the support vector machine. The soil moisture prediction model under moistube irrigation was established, finally the model was compared and analyzed. The results showed that the consistency effect of the two models was good. However, compared with the BP neural network prediction model optimized by genetic algorithm, the particle swarm algorithm optimized the support vector machine based moistube irrigation prediction model had higher accuracy. The results of this experiment can provide theoretical support for the exploration and modelling prediction of soil water infiltration under moistube irrigation.

The Role of Latent Heat Buffering in the Generation of High-Silica Rhyolites

Abstract The physical process of crystal-melt separation is responsible for the accumulation of small to very large volumes (>100 km3) of eruptible rhyolitic melt in the shallow crust. Granitic intrusions, although providing a terminal, time-integrated image of melt segregation processes, host an unmatched record of the physical properties controlling mechanisms and rates of interstitial melt extraction from a crystal-rich source. We applied mass balance calculations and thermodynamic modeling simulations to an extensive bulk rock geochemistry dataset (>150 samples) collected in a Permian upper-crustal granitoid intrusion of the Italian Southern Alps. Textural and geochemical evidence indicate that this intrusion constituted a single, zoned magma body, with a crystal-rich base and a thick (~2 km), high-silica cap (75–77 wt% SiO₂). The large compositional variability of the crystal-rich materials suggests variable degrees of melt extraction efficiency and corresponding terminal porosities. Specifically, the loosely bimodal distribution of porosity values (φ) indicates that at least two distinct melt segregation mechanisms were operating in this system, which produced both high (0.65–0.45) and low terminal porosities (0.45–0.25) in the crystal-rich, cumulate materials. Modeling of latent heat budget shows that coexistence of cumulate products with differing terminal porosity signature can be explained by melt segregation processes taking place at different depths across a thick, interconnected magmatic reservoir with an initial homogenous water content (~4 wt% H2O). Deep in the mush column, low water activities (aH₂O < 0.5) promoted thermal buffering of cooling magma at high crystallinities, enabling residual melt extraction by percolation through a crystalline framework accompanied by compaction. Instead, at shallower depths, high water activities (aH₂O > 0.5) ensured prolonged magma residence at porosities that promoted crystal melt separation via hindered settling. Distinct melt extraction processes, acting synchronously but at different depths in vertically extensive silicic mush columns, can account for the large volumes of residual, haplogranitic melt mobilized during the relatively short lifespan of upper crustal magma reservoirs (~105 years).

Biocrusts enhance soil structural stability during freeze-thaw cycles and improve soil erosion resistance in cold-winter drylands

Seasonally frozen soils are extensively distributed in drylands at middle- and high-latitude regions across the earth and experience intensive freeze-thaw cycles during cold winters. Cyanobacterial and moss biocrusts are critical living skins that cover a large portion of cold-winter drylands and, thus, have potential to regulate soil structure and function within frozen periods. Yet, the biocrust effect on soil structural stability during freezing and thawing and its underlying influencing factors have remained unanswered. Here, we conducted freezing and thawing simulations to elucidate the responses of soil structural stability to cyanobacteria- and moss-biocrust cover under different cycles of freeze-thaw (0–40 cycles) and initial water contents (0.03–0.20 cm3 cm−3). Our findings unveiled that the structural stability of bare soil, cyanobacterial biocrusts, and moss biocrusts decreased by 38.4%, 28.9%, and 24.1%, respectively, as a result of increasing freeze-thaw cycles and initial water content. However, as compared with bare soil, biocrust cover significantly mitigated the adverse impacts of freezing and thawing on soil structural stability. Specifically, biocrusts reduced the relative variation of soil particle-size distribution, porosity, and organic carbon content by 68.9%, 41.1%, and 32.1%, respectively, during increasing freeze-thaw cycles. Meanwhile, the relative variation of these properties caused by increasing initial water content during freezing and thawing was reduced by 39.4% due to the biocrust cover. As the consequences of such changes, biocrusts ultimately reduced the relative degradation of structural distance, aggregate stability, and erodibility by 39.4% in increasing freeze-thaw cycles and by 43.6% in increasing initial water content. This clearly demonstrated the biocrust contributions to enhancing soil structural stability and improving soil erosion resistance during freezing and thawing. Our study highlights the fundamental role of biocrusts in intervening soil structural degradations, caused by freeze-thaw cycles, and in serving as an imperative consideration during frozen periods in cold-winter drylands.

Study on the effect of ground stratification on heat transfer of vertical ground heat exchangers in lateritic clay areas

The potential effect of ground stratification on the efficiency of ground heat exchangers (GHEs) in lateritic clay regions remains unclear. Model experiments were conducted to investigate the effects of soil dry density, water content, and ground stratification on the heat exchange between GHEs and the surrounding lateritic clay. A 3D numerical model accounting for ground stratification was proposed and validated using experimental data. The model further examined the influence of soil moisture on the dynamic heat exchange process. The findings of the model experiments indicate that the heat from buried pipes increase soil temperature by 12.8 % when the initial water content of lateritic clay (with dry density of 1.1 g/cm3) rises from 5 % to 28 %. Raising the dry density from 1.1 to 1.3 g/cm3 at 28 % water content results in a 7.5 % temperature increase. The initial soil moisture and density have negligible effects on the temperature gradient within 18 cm of the geothermal pipes. The temperature increased faster in the sand layer than in the lateritic clay layer owing to the difference in thermal properties. The impact of heat produced by GHEs on the temperature field in homogeneous soil layers differs considerably from that in stratified soil layers. The 3D numerical model provided a good fit for the measured soil temperature in the stratified soil layer, including the soil temperature variation at the layered interface. The simulation results showed that for dry and saturated strata, the temperature of the lateritic clay around the GHEs increased with increasing initial stratum moisture. For unsaturated lateritic clay strata, because of the possible impacts of moisture and heat coupling migration, the temperature of the stratum around the GHEs first increased and subsequently decreased as the initial stratum moisture was enhanced.

Estimating aboveground biomass dynamics of wheat at small spatial scale by integrating crop growth and radiative transfer models with satellite remote sensing data

Aboveground biomass (AGB) of plants is an agroecological indicator that can be used to monitor crop growth status and quantify biomass carbon stock in agricultural ecosystems. Although satellite remote sensing data and crop models are widely employed to estimate AGB dynamics, their application in small-scale research plots is often constrained by the unavailability of freely and timely high-resolution satellite imageries and the challenge of acquiring reliable model inputs like initial soil water and nitrogen content. This study integrated a crop growth model (APSIM-Wheat) and radiative transfer model (PROSAIL) to estimate AGB dynamics at a small plot scale (ca. 5 to 20 m2) within variety trials (ca. 1 to 2 ha) by assimilating trial-level remote sensing data into the hybrid APSIM-PROSAIL model. The APSIM-PROSAIL integration, developed by deriving PROSAIL input parameters from APSIM-Wheat output variables, was verified by evaluating its capacity to reproduce trial-level Sentinel-2 (S2) NDVI dynamics across 30 variety trials in 2020. The comparison of the simulated and observed trial-level S2 NDVI dynamics yielded an overall RRMSE of 18.2% (n = 646 observations), suggesting the potential of using observed S2 NDVI dynamics to constrain APSIM-PROSAIL and estimate environment variables in cropping systems. This constraint was subsequently assessed in 28 variety trials in 2021, where APSIM-PROSAIL inversely estimated unknown trial-specific variables including initial soil water and nitrogen content across the trials. Using the estimated initial soil status and the plot information including genotypes and management as sown, we demonstrated that this method could also facilitate accurate retrievals of plot-level AGB dynamics with an overall RRMSE of 20.9% (n = 976 measurements). The proposed APSIM-PROSAIL demonstrated the capability to accurately retrieve plot-level AGB dynamics and reproduce trial-level S2 NDVI dynamics across a broad and diverse range of variety trials in the Australian Wheatbelt, indicating its potential utility to facilitate biomass carbon stock assessment. It holds the potential as a tool to explore the relationships between canopy spectral information and crop traits in response to genotype-environment-management interactions in agricultural ecosystems. The method enables the examinations of within-field variabilities for crop traits through retrieving them at small spatial scales from coarse remote sensing data.

Intelligent prediction of unfrozen water content of artificially frozen clay along one-dimensional column based on LF-NMR

The unfrozen water content (UWC) plays a crucial role in frozen soil engineering, however, traditional unfrozen water measurement or calculation methods are time-consuming and costly, and it is difficult to express the non-linearity among the influencing factors. Currently, LF-NMR is widely recognized as an effective tool for measuring unfrozen water. In this study, a calibration curve that can describe the relationship between the NMR signal and water content was derived. Moreover, the effects of temperature, initial water content, and soil height on UWC are explored along one-dimensional large-diameter columns based on LF-NMR data. Combined with the ML algorithm and the UWC test data under different factors based on LF-NMR, an intelligent prediction method that can consider the nonlinear characteristics of multiple factors is proposed. The results showed that the NMR accuracy is 176.64 semaphore per 1% water content, the error between the water content calculated from the calibration curve and that obtained from the drying method is small (average error is 0.97%), and the linearity degree of the calibration curve is good (R2 = 0.999). Moreover, due to the strong correlation between unfrozen water and temperature, initial water content, and other factors, the results indicated that the GPR model can better describe this correlation and has the best prediction effect, which was evaluated with the quantitative indicators: R2 = 0.96, RMSE = 1.07, MAE = 1.00, and again verifies the superiority of this model in combination with other literature data. Overall, this paper offers a technical basis for controlling and preventing freezing and thawing disasters in cold regions and artificial freezing engineering projects.

Migration Rules and Mechanisms of Nano-Biochar in Soil Columns under Various Transport Conditions.

Compared to traditional biochar (BC), nano-biochar (NBC) boasts superior physicochemical properties, promising extensive applications in agriculture, ecological environments, and beyond. Due to its strong adsorption and migration properties, NBC may carry nutrients or pollutants to deeper soil layers or even groundwater, causing serious environmental risks. Nevertheless, the migration rules and mechanisms of NBC in soil are still unclear. Therefore, this study employed soil column migration experiments to systematically explore the migration rules and mechanisms of NBC under various flow rates, initial soil water contents, soil depths, and soil textures. The results showed that regulated by smaller particle size differences and greater surface charges, NBC exhibited a stronger migration ability compared with traditional BC. As the soil texture transitioned from fine to coarse, the migration capability of NBC significantly improved, driven by both pore structure and interaction forces as described by the DLVO theory. The migration ability of NBC was also greatly boosted as the soil transitioned from saturated to unsaturated conditions, primarily because of preferential flow. When the flow rate increased from 70% KS to 100% KS and 130% KS, the migration ability of NBC also increased accordingly, as changes in injection flow rates altered the velocity distribution of pore water. NBC in 25 cm soil columns was more prone to shallow retention compared with 10 cm soil columns, resulting in weaker overall migration ability. In addition, through fitting of the two-site kinetic model and related parameters, the penetration curves of NBC under various variable conditions were effectively characterized. These findings could offer valuable insights for NBC's future efficient, rational, and sustainable utilization, facilitating the evaluation and mitigation of its potential environmental risks.

Effect analysis of temperature and initial water content on the adsorption and separation of VOCs by ZIF‐8 based on molecular simulation

AbstractVolatile organic compounds (VOCs) have seriously polluted the atmospheric environment and caused harmful effects on human beings, so it is imperative to control oil vapor emissions. Metal organic framework materials, as one of the porous materials, have a good application prospect in the field of gas adsorption separation. In this paper, the effects of temperature and initial water content (IWC) on the adsorption properties of methane (CH4), ethane (C2H6), ethylene (C2H4), propane (C3H8), and propylene (C3H6) by ZIF‐8 were studied by combining the large gauge Monte Carlo (GCMC) and ideal adsorption solution theory. The results show that the higher the temperature is, the lower the adsorption capacity is, the higher the threshold pressure is, and the single molecule interaction energy changes little with temperature. But pore volume is still the main influencing factor. The IWC also reduces the saturated adsorption capacity. Preloaded water molecules can enhance the electrostatic interaction at low pressure, thus affecting the adsorption heat and interaction energy of single molecules. Overall, these findings provide valuable mechanistic insights into the effects of temperature and IWC on the adsorption properties of ZIF‐8 for VOCs.

Monitoring of early curing stage of cemented soil using polymer optical fiber sensors and microscopic observation

Deep cement mixing (DCM) piles are widely utilized for reinforcing soft clay foundations, particularly in coastal regions where soil stability is critical. Monitoring the quality and early-stage behavior of cemented soil is essential to ensure the effectiveness of DCM pile projects in meeting design requirements. Innovative methods for on-site monitoring are necessary to enhance the reliability and efficiency of these reinforcement techniques. In this study, a novel approach is proposed utilizing polymer optical fiber (POF) sensors based on physical optical sensing principles to monitor the initial hydration degree and overall quality of cemented soil during the early curing stage. The proposed method relies on the principle of physical optical sensing, where POF sensors are employed to measure changes in reflected light intensity (LI) and temperature in cemented soil. Two crucial variables, namely the initial water content and the amount of cement, are considered in analyzing their impact on the LI and temperature changes over time. Unconfined compressive strength (UCS) tests and scanning electron microscopy (SEM) analysis are conducted on cemented soil samples with varying water-cement ratios to investigate their mechanical properties and microstructure evolution. The results of the UCS tests indicate that higher initial water content prolongs the initial hydration reaction time required for cemented soil with different cement contents. Analysis of LI curves reveals a rapidly rising trend as the hydration reaction progresses, particularly evident in samples with higher initial water content. SEM analysis further demonstrates that a stable POF LI corresponds to the completion of the hydration process, with hydrated gel formation resulting in a more compact microstructure and smaller voids. The findings highlight the significant influence of cement quantity and initial water content on the mechanical strength and microstructure of cemented soil. By analyzing changes in reflected LI and temperature, the proposed monitoring method provides valuable insights into the early-stage behavior and quality of cemented soil during the curing process. This innovative use of POF sensors for on-site monitoring offers a novel approach to evaluating cemented soil in DCM pile projects.

Compressibility of lime-treated dredged slurry with high water content

Lime is widely used for soft ground treatment, rendering the compressibility of lime-treated soil a crucial factor in deformation analysis in engineering applications. This study investigated the compressibility of three remoulded lime-treated slurries with high water content in Southeast China. Sixty groups of oedometer tests were conducted on lime-treated soils with an initial water content of 1 to 3 times the liquid limit and lime contents between 1 and 3%. The oedometer test results were discussed to examine the remoulded yield stress σy′\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\upsigma }_{y}^{\\prime}$$\\end{document} of lime-treated slurry. Considering the relationships between σy′\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\upsigma }_{y}^{\\prime}$$\\end{document}, the void ratio, lime content, and initial water content were preliminarily discussed and quantitatively established. Research on the normalised compression curve of lime-treated soil revealed that for soil samples containing a lime content of 0–%, the normalised compression curve at σp′\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\upsigma }_{p}^{\\prime}$$\\end{document}>σy′\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\upsigma }_{y}^{\\prime}$$\\end{document} can be represented by a unique line. Furthermore, the log(1 + e) − log σv′\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\sigma }_{\ ext{v}}^{\\prime}$$\\end{document} compression curve of lime-treated slurry at pre-yield state is analysed, and a prediction method for the modified compression index is proposed.

Correlation between synthesis parameters and hyperelasticity of hydrogels: Experimental investigation and theoretical modeling

The mechanical properties of hydrogels are significantly influenced by synthesis parameters. Although the mapping from the space of synthesis parameters to the space of properties has been investigated experimentally, a quantitative theoretical framework is still lacking. In this work, the effect of synthesis parameters on the hyperelastic behaviors of hydrogels was experimentally studied. Subsequently, we conducted theoretical analysis by combining the constitutive model and polymer physics to quantify the correlation between synthesis parameters (the initial water content, current water content, and degree of cross-linking) and hyperelasticity (the elastic modulus, degree of entanglement, and stress-stretch ratio curve) of hydrogels. The internal relation between critical polymer content for entanglement and both the initial water content and degree of cross-linking arises from the scaling laws. By analyzing the critical polymer content for entanglement and comparing it with the current polymer content, hydrogels are categorized as either cross-linking-dominated or entanglement-dominated. The current study indicates that a low degree of cross-linking, i.e., a long-chain structure, is an important prerequisite for plenty of entanglements. Hydrogels with low cross-linking are highly entangled, whether they possess high initial water content/low current water content or low initial water content/high current water content. This work paves the way for the systematic design of synthesis parameters, thereby guiding the modulation and optimization of the overall mechanical properties and the application of hydrogels.

Predictive Pattern of Undrained Shear Strength in Stabilized Sulfur Rich Silty Soil Based on Binder and Initial Mixing Water Content

A laboratory investigation was conducted to identify principal variables-initial mixing water content, porosity, and binder content- impacting undrained shear strength (qu) of stabilized sulfur-rich silty soil. An equation for predicting qu of stabilized soil was established based on the experimental data. Initially, samples were prepared with soils sample with different initial water and binder contents. Multicem, a binder consisting of a mix of cement and cement kiln dust, was added to the samples. Three different percentages of Multicem were mixed at five different soil water contents to measure qu of stabilized mixtures to understand how water content and porosity levels in the samples affect the performance of the binder and their combined impact on the strength of the samples. The soil-binder mixtures were compacted and subsequently cured in laboratory-controlled environment. The prepared samples were tested in uniaxial compression test apparatus. The results evidenced that binder content and corresponding porosity affect the strength of specimens at an equal water content. The results showed that at equal initial mixing water content, the qu of a sample increased by increasing binder content. Furthermore, it was observed that increase of binder content has a reverse effect on porosity. It was appeared lowering the soil water content, initially increased the strength until an optimum water content. Further lowering water content increased the porosity and consequently decreased qu of samples. Moreover, a ratio of porosity/volumetric binder content was chosen to evaluate the impact of these two variables on strength of samples. This study showed that qu is an exponential function of porosity/binder volumetric content ratio which depends on initial mixing water content of mixtures. It was shown at water content lower than the optimum, results of stabilization are more effective than in soil at higher water contents. Therefore, reducing the water content and thereby porosity has more significant effect on improving qu than increasing the binder content.

Experimental Study on Cold Start Strategies of Fuel Cell Stack: Sensitivity Analysis, Optimization, and Boundaries

The adaptability of fuel cell vehicles in low-temperature environments remains challenging for their commercialization owing to the propensity of water within the fuel cell to freeze during a cold start, which impedes gas transmission and subsequent reactions. Consequently, the initial water content before cold start and the heat and water generated during this process are crucial for achieving a successful cold start. In this study, current- and voltage-controlled starting strategies are analyzed using a stack comprising 20 cells with an area of 285 cm2. Furthermore, key parameters related to shut down purging and cold start are optimized using starting time and reverse polarity cell count as optimization objectives. The optimal conditions for cold start include a current density of 0.5 A cm−2, voltage of 0.45 V, purging time of 180 s, and stack temperature (during purging) of 60 °C. Furthermore, the ambient temperature boundary is determined as −25 °C–−30 °C for a successful cold start without auxiliary heating in the stack.

The Implications of Thermal Hydrodynamic Atmospheric Escape on the TRAPPIST-1 Planets

JWST observations of the seven-planet TRAPPIST-1 system will provide an excellent opportunity to test outcomes of stellar-driven evolution of terrestrial planetary atmospheres, including atmospheric escape, ocean loss, and abiotic oxygen production. While most previous studies use a single luminosity evolution for the host star, we incorporate observational uncertainties in stellar mass, luminosity evolution, system age, and planetary parameters to statistically explore the plausible range of planetary atmospheric escape outcomes. We present probabilistic distributions of total water loss and oxygen production as a function of initial water content, for planets with initially pure water atmospheres and no interior–atmosphere exchange. We find that the interior planets are desiccated for initial water contents below 50 Earth oceans. For TRAPPIST-1e, f, g, and h, we report maximum water-loss ranges of 8.0−0.9+1.3 , 4.8−0.4+0.6 , 3.4−0.3+0.3 , and 0.8−0.1+0.2 Earth oceans, respectively, with corresponding maximum oxygen retention of 1290−75+75 , 800−40+40 , 560−25+30 , and 90−10+10 bars. We explore statistical constraints on initial water content imposed by current water content, which could inform evolutionary history and planet formation. If TRAPPIST-1b is airless while TRAPPIST-1c possesses a tenuous oxygen atmosphere, as initial JWST observations suggest, then our models predict an initial surface water content of 8.2 −1.0+1.5 Earth oceans for these worlds, leading to the outer planets retaining >1.5 Earth oceans after entering the habitable zone. Even if TRAPPIST-1c is airless, surface water on the outer planets would not be precluded.

Re-watering solution facilitates seed germination and seedling growth of Carex schmidtii: Implication for species re-introduction in degraded semi-arid wetlands

Water deficiency threatens the health and function of wetlands in semi-arid areas. Optimum re-watering is an effective method for close-to-natural restoration to mitigate wetland degradation. Although the ecological importance of optimal re-watering as a nature-based solution for promoting wetland plant growth has been widely recognized, the response mechanisms of seed germination and seedling growth to re-watering are still poorly understood despite their decisive impact on plant life history. To fill this gap, this study compared the characteristics of seed germination and seedling growth in Carex schmidtii under initial water content with three levels (30%, 50%, and 70%) and five re-watering treatments (maintained at constant water content and re-watering to 100% on 7th, 14th, 21st, and 28th day). Moreover, the degree of reserve mobilization during four germination stages (seed suckering, sprouting, 20% germination, and seedling growth) was investigated. The results showed that water deficiency and re-watering treatments significantly affected C. schmidtii seed germination, seedling growth, and reserve mobilization. Compared with the other treatments, 50% moisture content and re-watering to 100% on the 14th day (50%-RT3) treatment significantly improved germination traits (germination rate, daily germination rate, germination index, and vigor index) and seedling growth characteristics (shoot length, root length, shoot biomass, root biomass, and total biomass). Furthermore, the degree of mobilization of starch, soluble protein, fat, and soluble sugar accumulation in C. schmidtii seeds under 50%-RT3 was higher than that in the other treatments. The structural equation model showed that the characteristics of seed germination and seedling growth of C. schmidtii were directly related to water deficiency and re-watering treatments, whereas reserve mobilization indirectly affected seed germination and seedling growth. These findings demonstrated that water deficiency and re-watering treatments have a crucial regulatory effect on seed germination and seedling growth of wetland plant species through a dual mechanism. This study provides information for the formulation of an optimum re-watering strategy for wetland vegetation restoration in semi-arid areas of the world.

Exploring alkali-source, pore-filling and cementation damage effects in cemented clay with typical industrial waste binders

Various industrial waste binders (IWBs) are being recycled in soil stabilization to save cement consumption. However, the coupled effects brought out by combined IWBs on stabilized soils are still unclear. IWBs are categorized into two typical categories (IWB-A and IWB-B) referring to their chemical role in this study. The alkali-source effect, pore-filling effect and cementation damage effect by IWBs in soil stabilization are explored. A series of mechanical and microscopic tests is performed on stabilized clay with different proportions of IWB-A and IWB-B. Moreover, initial water contents and cement contents of cement-stabilized clay are varied to examine the evolution of coupled effect with void ratio and cementation level. The results indicate that the alkali-source effect strengthens the cementation bonds and increases the early strength by 0.5–1.3 times, whereas the pore-filling effect improves the microfabric especially for the specimen with a large void ratio. The alkali-source effect increases soil cohesion cu at the pre-yield stage, and the pore-filling effect increases frictional angle φu at the post-yield stage. The cementation damage effect is remarkable at a low void ratio, which may result in many extruded pores among soil aggregates. The strength evolution with IWB proportions can be well stimulated by considering the coupled alkali-source effect, pore-filling effect and cementation damage effect. The optimal proportion of IWBs corresponds to an optimal combination of coupled effect.

Investigation on solidified/stabilized behavior of marine soil slurry by lime-activated incinerated sewage sludge ash-ground granulated blast furnace slag under multifactor conditions

This study aims to evaluate the possibility of reusing treated marine clayey soils by stabilization/solidification (S/S) technology as geomaterial in reclamation projects from the aspects of engineering strength, chemical modification and environmental risk assessment. The lime-activated incinerated sewage sludge ash (ISSA) together with ground granulated blast furnace slag (GGBS) was employed as the binder. The multi-controlling factors including water content, curing time, salinity, and chemical compositions of mixing solution were taken account to identify the S/S treated Hong Kong marine deposit (HKMD) slurry based on the strength tests, pH measurement, thermo-gravimetric (TG) analysis, X-ray diffractometer (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy coupled with energy-dispersive spectrometry (SEM-EDS) and toxicity characteristic leaching procedure (TCLP) tests, etc. The results show that the S/S treatment using lime-activated ISSA-GGBS can effectively enhance the strength of marine soil at initial water content of 110% and 200%. The water content and curing time have a significant impact on the S/S treated HKMD. The pH of treated soils is higher than 11.1, which proves an alkaline environment for the reactions in the treated soil. A special case is the treated HKMD at 200% water content hydrated by MgCl2 solution, which has a low pH of 10.23 and maintains a slurry state. Based on the TCLP results, the leaching concentration of heavy metals from S/S treated HKMD is environmentally safe and meets Hong Kong standard for reusing treated soil with a low level of <0.2 mg/L. The content of main products such as calcium/magnesium silicate hydrate, ettringite or Friedel's salt depends on the chemical additions (e.g. distilled water, seawater, NaCl and Na2SO4). The products in the specimens mixed with MgCl2 solutions are mainly composed of Mg(OH)2, M-S-H and MgCO3, which is distinct with the neoformations in the other cases. Therefore, this study proves that the S/S treated soil slurry could be reused as geomaterials in reclamation projects, and the S/S process is greatly affected by water content, curing time and solution compositions, etc.

Light thinning effectively improves forest soil water replenishment in water-limited areas: Observational evidence from Robinia pseudoacacia plantations on the Loess Plateau, China

Soil water plays a key role in vegetation growth and recovery, mainly replenished by rainfall in the water-limited areas. Thinning is an important practice for forest reconstruction and soil water regulation. However, the effects of different thinning intensities on the dynamics of soil water and its replenishment by rainfall have been inadequately quantified, which could provide a guide for reasonable thinning intensity determination for in high-density forests from a hydrological perspective. In this study, one nonthinning plot and 5 plots with different thinning intensities, i.e., 35 % (light), 45 % (medium), 55 % (moderate), 65 % (heavy) and 80 % (extremely heavy) in Robinia pseudoacacia plantations, which are widely planted on the Loess Plateau, were set up. The volumetric soil water content (SWC) at 0–200 cm depths and rainfall were observed simultaneously and continuously for up to two years. The soil properties and vegetation structure in each plot were also measured regularly. The results showed that (1) the SWC in all the thinning plots was significantly greater than that in the nonthining plot (P < 0.05). (2) The replenishment increased with increasing thinning intensity, and then decreased after reaching a maximum at T35 % under most rainfall events except for light events. (3) The variations in the soil water response characteristics among the plots with different thinning intensities were mainly significantly correlated with the initial soil water content (ISWC), leaf area index (LAI) and understorey vegetation characteristics (P < 0.05). (4) Based on the relationship between soil water replenishment and retention with thinning intensity and stand density, quantitative equations were fitted to determine the reasonable thinning intensity (22–28 %) and retained stand density (1019–1091 trees/ha), respectively. Our study concluded that thinning could effectively improve soil water, especially light thinning, which could obviously enhance the replenishment of soil water by rainfall in Robinia pseudoacacia plantations. This study can provide a reference for determining forest thinning intensity or stand retention density, which is beneficial for water and reforestation management in water-limited regions.

Swelling pressure of phyllite residual soil during saturation

Phyllite residual soil is a typical regional soil formed from the weathering of phyllite rock formations, characterized by poor engineering properties. The swelling pressure could pose a threat to roadbed stability and other geological engineering disasters during the rainy season. Therefore, studying the swelling pressure of phyllite residual soil is critical for ensuring the sustainable development of both human society and the natural environment. In this study, a series of swelling pressure tests were conducted on the phyllite residual soil to determine its swelling pressure, and nuclear magnetic resonance (NMR) test was applied to assess the evolution of soil fabric in both the initial unsaturated state and saturated state. The results indicate that the swelling rate of phyllite residual soil is negatively correlated with the initial water content and positively correlates with the dry density. The denser or drier the phyllite residual soil is in its initial state, the higher the equilibrium swelling pressure will be. The analysis of T2 distribution curves reveals that during the wetting process in phyllite residual soil, water fills micropores prior to macropores until water fills up all pores.