Changes In Solute Concentration Research Articles

Power feasibility of single-staged full-scale PRO systems with hypersaline draw solutions

Pressure retarded osmosis (PRO) is a process that allow to generate energy from osmotic gradient. This process uses selective membranes in order to produce electrical energy through a hydraulic turbine. PRO can be used as a renewable energy technology where water resources are inexhaustible. PRO has the advantage of knowing when and how much energy will be produced. Unfortunately at the moment there are certain limiting factors concerning membrane and module characteristics that have prevented PRO to be fully exploited at full-scale. This study aims to assess the impact of hypersaline draw solutions (60–180 g L−1), membrane characteristics such as structural parameter, module membrane surface and permeability coefficients on the net energy generated by single-staged full-scale PRO system with up to 8 spiral wound membrane modules (SWMMs) in series in a pressure vessel. To carry out this study, characteristics of existing PRO membranes at lab-scale were scaled up to 8 inches SWMM. The results showed the change in the optimal operating parameters with the change of membrane characteristics and draw solution concentration. This study concluded that single-staged full-scale PRO process would be viable from an energy point of view if membranes were manufactured on an industrial scale and with the characteristics of existing membranes on a laboratory scale.

In situ monitoring of loading and elution processes of cryoprotectants at the single-cell level with Raman spectroscopy

BackgroundThe analysis of cell membrane permeability plays a crucial role in improving the procedures of cell cryopreservation, which will affect the specific parameter settings in loading, removal and cooling processes. However, existing studies have mostly focused on deriving permeability parameters through osmotic theoretical models and cell volume response analysis, and there is still a lack of the direct experimental evidence and analysis at the single-cell level regarding the migration of cryoprotectants. ResultsIn this work, a side perfusion microfluidics chips combined with Raman spectroscopy system was built to monitor in situ the Raman spectroscopy of extracellular and intracellular solution during loading and elution process with different cryoprotectant solution systems (single and dual component). And it was found that loading a high concentration cryoprotectant solution system through a single elution cycle may result in significant residual protective agent, which can be mitigated by employing a multi-component formula but multiple elution operations are still necessary. Furthermore, the collected spectral signals were marked and analyzed to was perform preliminary relative quantitative analysis. The results showed that the intracellular concentration changes can be accurately quantified by the Raman spectrum and are closely related to the extracellular solution concentration changes. Significance and noveltyBy using the method of small flow perfusion (≤20 μL/min) in the side microfluidic chip after the gravity sedimentation of cells, the continuous loading and elution process of different cryoprotectants on chip and the spectral acquisition can be realized. The intracellular and extracellular concentrations can be quantified in situ based on the ratio of spectral peak intensities. These results indicate that spectroscopic analysis can be used to effectively monitor intracellular cryoprotectant residues.

Survival and rapid resuscitation permit limited productivity in desert microbial communities

Microbial activity in drylands tends to be confined to rare and short periods of rain. Rapid growth should be key to the maintenance of ecosystem processes in such narrow activity windows, if desiccation and rehydration cause widespread cell death due to osmotic stress. Here, simulating rain with 2H2O followed by single-cell NanoSIMS, we show that biocrust microbial communities in the Negev Desert are characterized by limited productivity, with median replication times of 6 to 19 days and restricted number of days allowing growth. Genome-resolved metatranscriptomics reveals that nearly all microbial populations resuscitate within minutes after simulated rain, independent of taxonomy, and invest their activity into repair and energy generation. Together, our data reveal a community that makes optimal use of short activity phases by fast and universal resuscitation enabling the maintenance of key ecosystem functions. We conclude that desert biocrust communities are highly adapted to surviving rapid changes in soil moisture and solute concentrations, resulting in high persistence that balances limited productivity.

Numerical modeling of metal-dielectric metasurface as an element of microwave sensors for biomedical applications

This paper reports the results of numerical modeling of wave reflection coefficient behavior of the metal-dielectric metasurface at microwaves that can be used for biomedical applications. The study includes optimization of the working parameters of the metasurface-based structure as a sensitive element of a microwave sensoring systems for determination of proteins concentration in different solutions. In the current research a unit with the geometry, which is similar to the geometry of one well of the standard 96-multiwell laboratory microplate, is used as a resonant metasurface unit cell and liquid-holding structure. Human serum albumin (HSA) is used as a protein specimen in our model study. The present numerical modeling is based on the results of our previous experimental measurements of complex permittivity values of HSA water solutions and its biochemical reaction mixtures using microwave dielectrometry method and the developed setup. The unit cell approach calculations are performed by COMSOL Multiphysics software. The optimization of working parameters of the metal-dielectric metasurface structure with tested solutions allow us to observe the resonance effects of the wave reflection coefficient in the microwave range. We can determine the HSA concentration changes in water solutions and enzymatic reaction mixtures by the resonance frequency shift of the wave reflection coefficient of the metal-dielectric metasurface. Developed metal-dielectric metasurface-based structure demonstrates prospects to be used as a sensitive element of microwave sensors for proteins concentration determination with biomedical purposes.

An Electrochemical Description of 1-Alkyl-3-Methyimidazolium Chloride Ionic Liquids

Three common Ionic Liquids (ILs) were selected 1-Methylimidazolium chloride ([Hmim]Cl), 1-Butyl-3-methylimidazolium chloride ([Bmim]Cl) and 1-Octyl-3-methylimidazolium chloride ([Omim]Cl) for investigation to explore the effects of alkyl chain length and cation protonation on corrosion rate. The aqueous IL solutions have demonstrated a range of identifiably distinct behaviours as a function of changing solution concentration in the range of 70-99.5 mol% water. These behaviours are evidenced by large changes in conductivity, density, and viscosity; these are measurable properties indicating an evolution of hydrogen bonding networks in these systems. These bulk solution properties are critical to the interaction with a metal surface; this was explored using electrochemical testing with Cu and Zn working electrodes. Herein, the focus will be on the use of cyclic voltammetry (at 75 mol%, 85 mol%, 97 mol% and 99.5 mol% water in IL) to describe metal dissolution, deposition, and hydrogen evolution in ILs. The system of equations implemented, to interpret the electrochemical data obtained, have wide-reaching implications in understanding the fundamental behaviours causing observed corrosion behaviours; additionally, the prediction of IL solution conductivity, a vital property for applications of ILs, is of significant value.A kinetic analysis of these solution systems are benefited by the simplicity of the system with no bulk electrolyte, i.e. only the two components: water and IL. Ohmic migration in the bulk and discharge on electrode surface are the two contributions which need to be considered in the Butler-Volmer equation. (n.b. A limitation in the treatment is that thus far no account is taken for the process of solid deposition via a nucleation stage.) In this approximation the following equations can be derived. Each discharging particle must pass two consecutive processes: (1) migration in the field, with characteristic time τohm, and (2) discharge, with the time τBV. The total time will be τtot = τohm + τBV, where τohm -1 = kohm and τBV -1 = kBV. Expressions for Icathodicscan and Ianodicscan results, where φ =E-Ec , for which Ec is the potential at zero current. Two examples are included (Figure 1) to highlight the performance of the models with experimental data. The first case illustrates a particularly good agreement with a cyclic voltammogram experimentally measured for a Cu working electrode in an aqueous-IL solution, the second case is included to demonstrate that the characterstic reversal (near I=0) can be produced. Some deviation, particularly at high current, is likely due to capacitive current. The fitting also gives conductivity, which can be compared and shows good agreement with independent experimental measurements. As such, this successful prediction of the electrochemical behaviours provides an important step in the utilisation of cyclic voltammetry as a method for delivering insight into these two-component IL-containing solutions systems through fundamentally derived expressions. Figure 1

Effect of Various Acid Solutions on the CO2 Dissolution Rate, Morphology, and Particle Size of Precipitated Calcium Carbonate Synthesized Using Seashells.

In this study, the influence of acid solutions on the production of precipitated calcium carbonate (PCC) using seashells was investigated. In terms of the Ca dissolution efficiency and atmosphere for dissolving CO32-, the results indicate that HCl, HNO3, CH3COOH, and HCOOH at 1.0 M were the most ideal among the acid solutions. The use of weak acids resulted in the low degree of dissolution of Al and Fe. These impurities could be mostly removed through the pH adjustment process, leading to PCC with a purity of 99% or more. Further, CH3COOH and HCOOH exhibited low CaCO3 carbonation efficiency owing to the hydrogen bonding of the carboxyl group and its hindering effect on the growth of CaCO3 particles. In addition, in the presence of the carboxyl group, the morphology tended to be oval, and the particle size was small. Particularly, when CH3COOH was used, the combined effect of the low initial Ca ion concentration and slow CO2 dissolution rate resulted in minimal changes during the carbonation time and the smallest particle size. However, variations in the degree of Ca concentration with a change in the acid solution concentration influenced the dominance of nucleation and particle growth, leading to variations in the particle size. The results of this study revealed that when manufacturing PCC using seashells, the appropriate acid solution must be selected to obtain the required PCC properties.

Utilizing a defective MgO layer for engineering multifunctional Co-MOF hybrid materials with tailored leaf-like and polyhedral structures for optimal electrochemical and photocatalytic activities

The hybridization of metal-organic framework (MOF) with inorganic layers would lead to the discovery of novel hybrid materials that can provide a compelling strategy for enhancing its photocatalytic and electrochemical response. In the present study, a highly efficient multifunctional hybrid material was developed by exploiting the defective layer formed on AZ31 Mg alloy through plasma electrolytic oxidation (PEO) as a nucleation and growth site for Co-MOF. The concentrations of the organic linker 2-Methylimidazole (2,MIm) and cobalt nitrate as a source of Co2+ ions were varied to control the growth of the obtained Co-MOF. Lower concentrations of the 2, MIm ligand favored the formation of leaf-like MOF structures through an anisotropic, two-dimensional growth, while higher concentrations led to rapid, isotropic nucleation and the creation of polyhedral Co-MOF structures. The sample characterized by polyhedral Co-MOF structures exhibited superior electrochemical stability, with the lowest corrosion current density (3.11 ​× ​10−9 A/cm2) and the highest top layer resistance (2.34 ​× ​106 ​Ω ​cm2), and demonstrated outstanding photocatalytic efficiency, achieving a remarkable 99.98 ​% degradation of methylene blue, an organic pollutant, in model wastewater. To assess the active adsorption sites of the Co-MOF, density functional theory (DFT) was utilized. This study explores the changes in morphologies of the coatings of Co-MOF with the change of solution concentration to form coatings with enhanced properties on the metallic substrate, which could establish the groundwork for the development of next-generation multifunctional frameworks with diverse applications.

On the formation of gradient-distributed dendrites in a single crystal nickel-based superalloy directionally solidified under transverse static magnetic field

Directional solidification (DS) of alloys under static magnetic field has attracted extensive attention due to the development of thermoelectric magnetohydrodynamics (TEMHD). Assessing the influence of static magnetic field on solidification microstructures in single crystal (SX) superalloys is of great significance for both the development of SX superalloys and the understanding of external field-assisted solidification. In this contribution, under different transverse static magnetic fields, the evolution of dendritic structure in a SX nickel-based superalloy directionally solidified over a range of solidification velocities is systematically investigated. The results show that applying a transverse static magnetic field (TSMF) during DS does not disrupt the crystal orientation of SX superalloys. The distribution of dendrites or local primary dendrite arm spacings within the cross section of SX superalloys shows a gradient variation in the direction perpendicular to the TSMF. Additionally, the formation of gradient-distributed dendritic structure is closely related to the applied TSMF intensity and solidification velocity. It is easier to form a gradient-distributed dendritic microstructure at low solidification velocities and high magnetic fields. Based on the experiments and simulations, the formation of gradient-distributed dendritic microstructure is supposed to attribute to the variation of interdendritic constitutional undercooling created by the change of solute concentration in interdendritic region, which is induced by the TEMHD. The SX superalloy with a gradient distribution of dendrites may have potential applications due to its gradient properties. Meanwhile, these findings also provide a new method for preparing alloys with gradient microstructures.

Effect of acetate ions and pH on the morphology of cerium oxide nanoparticles

Cerium oxide nanoparticles (CeNPs) are recognized as functional materials with suitability in diverse applications. Conventional synthesis of CeNPs involves direct addition of alkaline solutions and/or precipitating agents to cerium solutions. Rapid changes in solution concentrations and ligand introduction result in less control over particle size and dispersity. Here, we report a simple hydrothermal synthesis of cubic shaped CeNPs through homogenous precipitation, achieved by introduction of acetate molecules. A distinct trend in CeNPs transitioning from octahedral to cubic morphologies was observed through a series of experiments. Results from experimental and computational studies have demonstrated that acetate plays an important role in directing the morphological transition of CeNPs and providing a pH-buffered environment. The formation of Ce(IV)-acetate complexes not only stabilizes aqueous Ce(IV) but also inhibits its hydrolysis in conditions of lower pH. The stabilization of Ce(IV) ions is also favorably weakened during the hydrothermal treatment, leading to successful homogeneous precipitation and the formation of mono-dispersed cubic-shaped CeNPs.

Energy assessment and thermodynamic evolution of a novel semi-clathrate hydrate cold storage system with internally circulating gas bubble disturbance

Low energy storage density, intermittent phase changes, and heat transfer barriers have posed significant challenges in the implementation of hydrate energy storage systems. Based on the heterogeneous nucleation mechanism for tetrabutylammonium bromide (TBAB) hydrate phase change energy storage, a novel cold storage system with internally circulating gas disturbance was constructed for energy evaluation and thermodynamic evolution. The hydrate cold storage efficiency, response time, dynamic driving force, unique force pattern of the coils and guest molecule diffusion were analyzed for the first time. The bubbles generated by gas internal circulation provided numerous nucleation sites for hydrate formation, efficiently promoting the energy storage process. The disturbances caused by the bubbles also rapidly transmitted the energy generated by the phase change. A hydrate storage density of 57.4 kWh/m3 for this system was the maximum among known hydrate storage systems. Notably, a change in solution concentration (from 10 wt% to 40 wt%) resulted in a 2–3-fold increase in the cold charge capacity. Rapid dilution of local solutions and rapid release of cold were the ways to promote the cold discharge. Less damage to the stress structure of the coil was due to the loose accumulation of hydrate particles under gas disturbance. The microbubbles generated by the gas disturbance enabled heterogeneous nucleation and heat-mass transfer in the hydrate cold storage. The gas disturbance-based hydrate energy storage process holds significant guiding value for various applications such as refrigerated transport, building cooling systems, and grid peak shaving.

Hyperspectral imaging sediment core scanning tracks high-resolution Holocene variations in (an)oxygenic phototrophic communities at Lake Cadagno, Swiss Alps

Abstract. Pigments produced by anoxygenic phototrophic bacteria are valuable proxies of past anoxia in lacustrine and marine environments. Pigment measurement typically requires time-consuming and costly chemical extractions and chromatographic analyses, which limits the temporal resolution of paleoenvironmental reconstructions based on sedimentary pigments. Here, we evaluate the potential of in situ hyperspectral imaging (HSI) core scanning as a rapid, non-destructive method to document high-resolution changes in oxygenic and anoxygenic phototrophic communities at meromictic Lake Cadagno, Switzerland. Three distinct groups of pigments can be detected with the HSI method in the sediments of Lake Cadagno; each pigment group represents a different phototrophic community. Oxygenic phototrophs are indicated by total chloropigments (TChl; chlorophyll a, b, and derivatives). Two types of anoxygenic phototrophs were distinguished – purple sulfur bacteria (PSB), represented by bacteriochlorophyll a, and green sulfur bacteria (GSB), represented by bacteriochlorophyll c, d, and e. HSI pigment indices were validated by pigment measurements performed on extracted samples using spectrophotometer and high-performance liquid chromatography (HPLC). Bacteriochlorophylls were present throughout the past 10 kyr, confirming geochemical evidence of nearly continuous stratification and sulfidic conditions at Lake Cadagno. Major shifts in the anoxygenic phototropic communities are recorded at decadal to millennial scales. GSB and PSB communities coexisted from 10.2–8.8 kyr BP. Dominance of PSB over GSB from 8.8–3.4 kyr BP indicates strongly stratified conditions in the lake and strong light radiation at the chemocline. From 3.4–1.3 kyr BP, PSB were mostly absent, and GSB became dominant, implying lower light intensity at the chemocline due to a combination of factors including deforestation in the lake surroundings, increased flood frequency, cooler climatic conditions, and changes in groundwater solute concentrations. The high-resolution HSI data show that frequent flood events and mass movements disturbed the chemocline and the anoxygenic bacterial communities and that the PSB were particularly sensitive and slow to recover following these disturbance events. This study demonstrates for the first time that HSI can detect GSB-related pigments, making the method uniquely valuable as a rapid tool to study samples containing pigments of both oxygenic and anoxygenic phototrophs.

Simultaneous measurement and ODE-modeling of ion- and water permeability through ion exchange membranes

The determination of diffusion coefficients in solid materials as a measure of particle mobility is of great scientific interest. This applies both to desired diffusion, such as in fuel cell- and dialysis membranes, and to undesired diffusion in insulating materials. In any case, diffusion is a measure of performance. Especially for solvated ions, the permeability of the solvent must also be considered.In this work, a measurement method for the simultaneous determination of coupled ion diffusion and water permeability in polymer membranes is presented. For this purpose, measurement methods for the determination of concentration-, volume- and membrane-potential changes are integrated into a single, miniaturized concentration cell.A system of ordinary differential equations is developed for the general description of the coupled transport processes. This makes it possible to model the interdependent solute concentration and solvent volume changes. The coefficients of interest are defined by fitting the model parameters to the measured data.To evaluate the new combined measurement setup, a freestanding ion exchange membrane with largely known properties is used. The membrane of choice is a Nafion® NR211 membrane, since Nafion® is one of the most investigated PEM in literature and allows a comparison of computational and experimental results with existing data.

Influence of temperature and organic acid on self-assembly behavior of pluronic F127

Temperature dependent micellization of 5 wt% F127 has been studied below and above its critical micellization temperature (CMT) using isothermal titration calorimetry. Monomer and micelle dissolution enthalpies are used to calculate solute–solute and solute–solvent interactions. Significant differences are observed at different temperatures indicating a difference in solvent re-structuring around the monomers and micelles. Variation in partial molar enthalpy of the solvent with change in solute concentration is found to be small, in passing from monomer dissolution regime at 288 K to micelle dissolution regime. Enthalpy measurement for the de-micellization process of aqueous F127 has indicated subsequent oligomer (or monomolecular micelle) formation in presence and absence of solubilized salicylic acid (SA). Significant reductions in critical micelle concentration (cmc) and enthalpy of micellization have been observed for F127 with solubilization of SA. Solution behavior of SA solubilized F127 system has been treated using regular solution theory and a decrease in the interaction parameter is observed with increased concentration of solubilized SA indicating its existence in the core region rather than corona.

Manipulative pore-formation of polyimide film for tuning the dielectric property via breath figure method

Polyimide (PI) films have been extensively used in the field of microelectronic as insulating materials. With the rapid development of microelectronic devices towards miniaturization and large power, the development of low dielectric properties of PI materials has attracted more and more attention. In this study, the breath figure (BF) process was used to prepare single-layered and multi-layered microporous PI films, for obtaining the low dielectric properties. The BF porous structure of PI film was successfully constructed by two implementing strategies, i.e., solution casting for direct preparation of PI film and solvent treatment upon pre-shaped PI film for in-situ pore-formation. By changing solution concentration, environmental humidity and temperature, efficient manipulation of the pore morphology of the film both on the surface and in the bulk layer was achieved. Such multi-layered porous BF structure has been proved to significantly lower the dielectric constant of PI film, from 3.7 of non-porous film to 1.7 of porous film. In order to further expand the application range of BF microporous PI film, both ways of alkali treatment and thermal oxidation were taken for the cross-linking of the porous PI films, greatly improving the solvent resistance of the film. The original porous morphology was completely retained, ensuring that the low dielectric properties were not affected. This is the first report on the preparation of multi-layered microporous low dielectric PI films by BF process.

Large-area silicon photonic crystal supporting bound states in the continuum and optical sensing formed by nanoimprint lithography.

Optical bound states in the continuum (BIC) are found in various dielectric, plasmonic and hybrid photonic systems. The localized BIC modes and quasi-BIC resonances can result in a large near-field enhancement and a high-quality factor with low optical loss. They represent a very promising class of ultrasensitive nanophotonic sensors. Usually, such quasi-BIC resonances can be carefully designed and realized in the photonic crystal that is precisely sculptured by electron beam lithography or interference lithography. Here, we report quasi-BIC resonances in large-area silicon photonic crystal slabs formed by soft nanoimprinting lithography and reactive ion etching. Such quasi-BIC resonances are extremely tolerant to fabrication imperfections while the optical characterization can be performed over macroscopic area by simple transmission measurements. By introducing lateral and vertical dimension changes during the etching process, the quasi-BIC resonance can be tuned over a wide range with the highest experimental quality factor of 136. We observe an ultra-high sensitivity of 1703 nm per RIU and a figure-of-merit of 65.5 for refractive index sensing. A good spectral shift is observed for detecting glucose solution concentration changes and adsorption of monolayer silane molecules. Our approach involves low-cost fabrication and easy characterization process for large-area quasi-BIC devices, which might enable future realistic optical sensing applications.

Direct evidence of the non-uniform electrodeposition of zinc at the early stage

Aqueous zinc-ion batteries (ZIBs) are regarded as one of the most promising electrical energy-storage systems for their eco-friendliness, low cost and high-safety. Although there have been a lot of studies recently on the Zn metal anode, little attention has been paid to its initial nucleation and growth behavior, which is critical to the understanding of fundamental mechanisms of the Zn plating. Herein, the digital holographic surface imaging (DHSI) method, combined synchronously with electrochemical tests, is employed to in-situ observe the non-uniform concentration changes on the surface of the copper substrate caused by the Zn nucleation and growth at the early stage. It is the first time to observe the early uneven depositions from a perspective of solution concentration changes in a symmetrical battery system. Results show that the later dendritic growth of Zn is closely related to the nucleation and earlier deposition process. Based on the phase maps obtained with in-situ DHSI technique, the nucleation and growth during the Zn electrodeposition can be closely investigated and vividly demonstrated, offering a promising avenue towards the understanding of the interfacial electrochemistry in all aqueous metal-ion batteries.

Adsorption and photocatalytic synergistic removal of ciprofloxacin on mesoporous ErFeO3/g-C3N4 heterojunction

The technology integrating adsorption and photocatalysis is regarded as the most promising strategy for the elimination of low concentration antibiotic contaminant. In this study, we firstly prepared the mesoporous g-C 3 N 4 nanosheets (CN) with the thickness of 4–5 nm by the thermal etching and ultrasonic techniques. Then perovskite ErFeO 3 nanoparticles (EF) were incorporated into CN to construct the 3 /g-C 3 N 4 (EFC) heterojunction. The heterojunction with EF content of 2 wt% (2-EFC) had the optimal adsorption and photocatalytic performance. 87.8% of ciprofloxacin (CIP) was eliminated via the adsorption–photocatalysis synergistic process over 2-EFC. The CIP adsorption capability of 2-EFC was 11.7 times that of CN, and the zero-order degradation reaction rate constant ( k 0 ) was 25.2 times of CN. The ultrathin and porous structure of CN increased the specific surface area and reaction active sites, shorten the diffusion distance of photoinduced charge carriers. And the construction of EFC heterojunction further accelerated the separation of charge carriers and inhibited its recombination. These two strategies ameliorated the adsorption and photocatalytic activity of EFC in removal of CIP. The CIP adsorption on the samples followed pseudo second order kinetics model, and the adsorption isotherm data complied with Langmuir isotherm model. The photocatalytic degradation process of CIP on 2-EFC could be divided into two phases. Due to the CIP concentration change in the degradation solution, the kinetics curve followed the zero order rate equation at 0 to 40 min. After that, it deferred to the first order rate equation. The h + , ⋅ OH and ⋅ O 2 – were involved in the photocatalytic degradation process. The structures of degradation intermediates and possible degradation pathways of CIP were proposed according to the HPLC-MS results. This research provided an alternative with high efficient synergetic effect of adsorption and photocatalytic degradation for the treatment of antibiotic wastewater. • A novel 0D/2D mesoporous ErFeO 3 /g-C 3 N 4 (EFC) heterojunction was constructed. • 87.8% of ciprofloxacin (CIP) was eliminated via the adsorption–photocatalysis process. • CIP adsorption complied with pseudo second order kinetics and Langmuir isotherm model. • The intermediates and possible degradation pathways of CIP were proposed.

Effect of NaCl Solution and Simulated Concrete Pore Solution Environment on the Efficiency of Steel Bar Energized Corrosion.

As the main problem of the durability deterioration of concrete structures, the corrosion of steel bars is usually made by the method of electrified corrosion with a short cycle and low cost. However, there is a big difference between the actual corrosion depth and the theoretical corrosion depth after the reinforcement is electrified. In this paper, through the accelerated corrosion test of steel bars, the change law and influence factors of corrosion efficiency of steel bars in concrete simulated pore solution and NaCl solution are studied. The test results show that the corrosion efficiency of reinforcement in the NaCl solution is higher than that in the concrete simulated pore solution, and the corrosion efficiency in the NaCl solution changes in two stages with the corrosion degree of reinforcement. The corrosion efficiency of concrete in the simulated pore solution decreases with the increase of corrosion degree of reinforcement, which is more significant than that in the NaCl solution. Under the same conditions, the corrosion efficiency is higher in the chloride ion solution with high concentration, and the influence of chloride ion concentration change in the simulated pore solution of concrete on the corrosion efficiency is more significant. The corrosion efficiency of reinforcement under low current density is higher than that under high current density.

Decadal trends in solute concentrations, mass flux, and discharge reveal variable hydrologic and geochemical response to climate change in two alpine watersheds

High-alpine environments are particularly sensitive to changes driven by climate change and experience more dramatic shifts in vegetation, snowmelt timing, and the relative ratio of rain to snow compared to other lower-elevation environments. These shifts drive changes in stream discharge and solute concentrations, long-term records of which may be archived in publicly available databases. Here, we use three decades of discharge and water quality data from two alpine watersheds along the Continental Divide in the Rocky Mountains of Colorado, USA, to quantify temporal trends in solute concentration and solute mass flux, which serve as integrators of watershed processes and are used to identify controls on how these watersheds respond to climate change over decadal timescales. By analyzing both solute concentrations and mass flux we are able to remove the effects of seasonal changes in discharge and separate hydrologic and geochemical drivers of changes in solute export from these two watersheds. While we find that concentrations of calcium, bicarbonate, and sulfate increase through time in both watersheds, increasing solute mass flux is found in one watershed but not the other, despite similar watershed characteristics such as elevation, precipitation, average temperature, and bedrock geology. We identify different dominant weathering mechanisms as the cause for the differences in watershed response to climate change. In one watershed, sulfide oxidation was the dominant weathering mechanism at the beginning of the record and stayed dominant through the three-decade period of data. This consistency in weathering mechanism likely controls why the solute flux did not change significantly. In contrast, in the other watershed, solute flux increased and water chemistry shows that the dominant weathering mechanism shifted from dominantly CO2-driven to more influence from sulfide-oxidation driven weathering. This shift in weathering mechanism is accompanied by significantly increasing solute fluxes. This study demonstrates the importance of quantifying geological weathering in watershed response to climate change where two similar watersheds exhibit different responses--one hydrological and one combined hydrological and geochemical--that could not have been predicted from a simple analysis of the watershed characteristics. Such analyses are needed on a large scale to quantify the type and magnitude of watershed changes in water quality and quantity to climate change, and suggest that weathering mechanisms, in particular weathering driven by oxidation of trace sulfide minerals, plays an important role in the geochemical response of watersheds to climate change.

Semi-empirical modelling of hydraulic conductivity of clayey soils exposed to deionized and saline environments

Clay liners are widely used as porous membrane barriers to control solute transport and to prevent the leakage of leachate both in horizontal and vertical flow scenarios, such as the isolated base and ramps of sanitary landfills. Despite the primary importance of saturated hydraulic conductivity in a reliable simulation of fluid flow through clay barriers, there is no model to predict hydraulic conductivity of clayey soils permeated with saline aqueous solutions because most of the current models were developed for pure water. Therefore, the main motivation behind this study is to derive semi-empirical models for simulating the hydraulic conductivity of clayey soils in the presence of arbitrary solute concentrations in addition to deionized water. In order to achieve this goal, a relatively comprehensive dataset of 842 measured hydraulic conductivities was retrieved from the experimental literature, where almost 44% of them are related to certain solute concentrations. Afterwards, two modelling approaches were introduced; the first one is a modified form of Mbonimpa et al.'s (2002) model, in which the constants are adjusted to take into consideration the variations in liquid limit due to a change in solute concentration. A modification term was added to the model for the sake of accuracy. In the second approach, a new form of solute concentration-dependent hydraulic conductivity function was proposed, where special attention was given to void ratio and adaptive liquid limit as effective parameters. The results revealed that hydraulic conductivity predictions could be erroneous if the influence of solute concentrations in permeating fluid is ignored. An error analysis was conducted to examine the models' applicability and deviations. A blind independent set of data, including 132 data points, was also used to verify models. On the other hand, both newly proposed models could predict the hydraulic conductivity for a variety of soils, salt species, and concentrations well. Therefore, the proposed modelling approaches are somehow unique by considering the salinity of the pore fluid in addition to deionized water. More importantly, both models are comprised of easy-to-measure parameters with clear physics-based implications.