Amount Of Unfrozen Water Research Articles

Experimental study on unfrozen water content of loess polluted by heavy metals

Currently, there are very few investigations on the unfrozen water content of contaminated soil due to heavy metals. This will have an impact on the efficacy and use of freezing technology in the remediation of heavy metal-contaminated soil. Thus, the purpose of this research is to determine the unfrozen water content and contributing factors of heavy metal-contaminated loess. As a result, Lanzhou loess was employed as an experimental material to produce contaminated soil with varied initial water content and heavy metal concentrations. Additionally, Zn, Ni, Cu, Cr, Cd, and Pb were used as pollution elements. The findings indicate that: 1) Unfrozen water content of loess with heavy metal ions underwent three processes: severe phase transition, transition stage, and freezing stage; 2) Effects of different heavy metal ions on the amount of unfrozen water in loess are as follows: Cu > Cr > Pb > Cd > Ni > Zn when levels are low. Effects of different heavy metal ions on the amount of unfrozen water in loess are as follows: Cu > Zn > Cr > Ni > Pb > Cd when levels are high; 3) The prediction model of unfrozen water content in the loess polluted by heavy metals was established as follows: wu = aT–b. This will help the remediation and management of heavy metals in urban contaminated soil in the future by freezing technology.

Effect of counterions on the water sorption and glass transition properties of maltobionate salts

AbstractThe purpose of this study was to clarify the effect of counterions on the water sorption and glass transition properties of maltobionate salts. Sodium maltobionate (NaMb), potassium maltobionate (KMb), and magnesium maltobionate (MgMb2) were employed, and the values for calcium maltobionate (CaMb2) and maltose were taken from the literature. The water sorption isotherm of the samples was characterized using the Guggenheim-Anderson-de Boer model. The glass transition temperature (Tg) and freeze-concentrated glass transition temperature (Tg’) were evaluated by differential scanning calorimetry. The effect of water content on the Tg was analyzed using the Gordon-Taylor model. The order of the anhydrous Tg values of maltobionate salts was: KMb < NaMb < maltose < MgMb2 < CaMb2. The anhydrous Tg of the divalent cation forms (MgMb2 and CaMb2) was much higher than that of the monovalent cation forms (NaMb and KMb). The anhydrous Tg will be affected by the plasticizing effect and electrostatic effect of cations. The Tg depression induced by water plasticizing was greater for KMb than for the other maltobionate salts. The order of Tg’ values of freeze-concentrated maltobionate salts was: KMb < maltose < NaMb < MgMb2 < CaMb2. This trend was almost the same as that seen for anhydrous Tg, but the range of the Tg’ values (242.2–257.8 K) was much lower than that of the anhydrous Tg (346.9–421.3 K). The Tg’ appears to be affected by the strength of ionic interactions and amount of unfrozen water.

Experimental research on the effect of applied potential gradient on frozen loess

Due to the existence of an electric double layer in the soil, frozen soil always has a certain amount of unfrozen water. And it will migrate under the action of the electric field. Select a kind of frost heave-sensitive soil (Lanzhou loess) as the object of study, and several bench-scale experiments on frozen Lanzhou loess were performed using 4, 6, 8, 10, and 12 V/cm potential gradients. The water content was measured after tests to investigate the relationship between water migration and applied potential gradient. The current was monitored during the experiments to calculate the energy consumption, and to evaluate the usability of electroosmosis in the frozen soil. The amount of water migration increase with the increase of potential gradient and the varied water content with potential gradients can be divided into steady, fluctuation, and incremental stage. The variation of current can reflect the process of water migration to a certain extent and can be divided into two stages, and water migration mainly occurs at the stage of drastic change of current.

DEPENDENCE OF STRENGTH CHARACTERISTICS OF MUDSTONE-LIKE CLAYS FROM THE AMOUNT OF UNFROZEN WATER

The article presents a methodology for studying of the strength properties of frozen soils using a modernized automated testing complex (AIC "ASIS") produced by NPP "Geotek" LLC (Penza, Russia) and determining the dependence of the amount of unfrozen water in the soil on the temperature using an adiabatic calorimeter. On the samples of mudstone-like clay, it was found that the conditionally instantaneous strength of frozen soils depends non-linearly on the temperature and salt presence in pore solution. The dependences of the conditional instantaneous strength of mudstone – like clay samples on the amount of unfrozen water in these samples are studied. It is established that the strength properties of clay soils at negative temperatures are mainly determined by the total amount of unfrozen water. The genesis of unfrozen water (temperature or the combined effect of temperature and salt concentration in the pore solution) does not matter.

Variation behavior of pore-water pressure in warm frozen soil under load and its relation to deformation

Containing a considerable amount of unfrozen water, frozen soil may produce excess pore-water pressure under external load, especially at temperatures near the thawing point. The variation of the pressure has a capability in influencing the deformation of frozen soils. In order to investigate the variation behavior of pore-water pressure in frozen soils and its relation to deformation, a series of pore-water pressure tests were conducted at subzero temperatures. A total of 13 frozen specimens were tested at various temperatures, and the pore-water pressures as well as the displacement were recorded. Then, variation behaviors of pore-water pressures and their effect on deformation were discussed. Results indicated that when a frozen soil sample is subjected to load, it responds with a slow increase in pore-water pressure in the early test stage up to a peak value, followed by subsequent extremely slow dissipation. The characteristic of pore-water pressure variations recorded in this study are closely correlated with temperature, soil type, and moisture content. Generally, the variation in pore-water pressure in frozen soils is caused by the coupled action of two opposing processes: an increasing process induced by solid matrix compression and a decreasing process induced by unfrozen water drainage. Thus, consolidation can be shown to occur as a component of compression and plays a significant role in the total deformation of warm frozen soils, although this effect decreases as decreasing soil temperature. However, it is difficult to distinguish the consolidation deformation from the creep deformation when taking into account the continuous variation in pore-water pressure throughout the test period.

Influence of Dimethyl Sulfoxide on the Low-Temperature Behavior of Cholesterol-Loaded Palmitoyl-oleyl-phosphatidylcholine Membranes.

The properties of lipid membranes at low temperature are important for a number of biomedical and biotechnological applications, and the success of these applications depends on understanding the effects of temperature changes on intermolecular lipid-lipid and lipid-water interactions. Here, we use Fourier transform infrared spectroscopy to study lipid suspensions in water/dimethyl sulfoxide (DMSO) solutions in the -60 to 30 °C range. DMSO is a cryopreservative agent of cellular systems, and its action is largely related to its interaction with the lipid membrane, especially in the low-temperature regime. In the present work, we analyze the effects of solvent composition on the structural and thermotropic properties of cholesterol (chol)-loaded liposomes of palmitoyl-oleylphosphatidylcholine (POPC) because POPC/chol liposomes are suitable models of the plasmatic membrane. To this extent, we compare the properties of lipid vesicles suspended in water and water/DMSO solution at 0.10 DMSO mole fraction and we observe that the gel phase of the membrane has an increased thermal stability on DMSO addition. We estimate that the amount of unfrozen water at T = -60 °C is much reduced by the presence of DMSO, both in the gel- and the liquid-ordered phase of the membrane. Interestingly, we also evidence a reduced hydration of the lipid heads in the presence of DMSO when the vesicles are dispersed in a liquid solution, whereas the addition of DMSO does not alter the hydration state of phosphate and carbonyl groups in the frozen state of the membrane.

A DSC and NMR-relaxation study of the molecular mobility of water protons interacting with chemically modified starches

Changes in the mobility of water protons in the chemically modified starches (CMS)–water system are studied by differential scanning calorimetry and NMR relaxation. The amounts of unfrozen water at negative temperatures and additional (after gelation) unfrozen for CMS are lower than those for native starch. The proton spin–spin relaxation time T 2 for CMS samples, conventionally attributed to the water fraction in starch granules, decreases monotonically with increasing temperature, whereas for native starch, this dependence exhibits an extreme behavior. Studying the dispersion dependences for 7 wt % gels, which characterize the rate of chemical exchange of water protons with protons of hydroxyl groups of polysaccharides, showed the absence of this kind of dependence for the CMS studied when the instrument operated at a frequency of 20 MHz. This data indicate the significant destructive changes in the structure of the CMS.

Исследование молекулярной подвижности протонов воды при взаимодействии с химически модифицированными крахмалами методами ДСК и ЯМР-релаксации, "Химическая физика"

The change of water protons mobility in the system chemically modified starches – water were investigated by DSC and NMR-relaxation methods. The amount of unfrozen water at subzero temperature as well as additional unfrozen water which appears after gelatinization have lower values for chemically modified starches in comparison with the native starch. The proton spin-spin relaxation time Т2 for chemically modified starch samples, conventionally referred to the fraction of water inside the starch granules, are monotonically decreasing at heating, while for the native starch this dependence has extreme character. The study of dispersion of 7% gels, characterizing the rate of chemical exchange of water protons with the protons of hydroxyl groups of polysaccharides, demonstrated the absence of such dependence for chemically modified starches at the operating frequency of measuring device 20 МHz. Received data suggest considerable destructive changes in chemically modified starches structure.

Seasonal differences in seismic responses of embankment on a sloping ground in permafrost regions

Because of its direct influence on the amount of unfrozen water and on the strength of intergranular ice in a frozen soil, temperature has a significant effect on all aspects of the mechanical behavior of the active layer in which temperature fluctuates above and below 0°C. Hence seismic responses of engineering structures such as embankment on a sloping ground in permafrost regions exhibit obvious differences with seasonal alternation. To explore the distinctive seismic characteristics of a railway embankment on the sloping ground in permafrost regions, a coupled water-heat-dynamics model is built based on theories of heat transfer, soil moisture dynamics, frozen soil mechanics, soil dynamics, and so on. A well-monitored railway embankment on a sloping ground in Qinghai–Tibet Plateau is taken as an example to simulate seismic responses in four typical seasons in the 25th service year. The numerical results show that seismic acceleration, velocity and displacement responses are significantly different in four typical seasons, and the responses on October 15 are much higher among the four seasons. When the earthquake is over, there are still permanent differential deformations in the embankment and even severe damages on the left slope on October 15. Therefore, this position should be monitored closely and repaired timely to ensure safe operation. In addition, the numerical model and results may be a reference for maintenance, design and study on other embankments in permafrost regions.

Thermo-mechanical facies representative of fast and slow flowing ice sheets: the Weichselian ice sheet, a central west Poland case study

Abstract This study deals with an issue of thermo-mechanical facies, reflecting specific thermal and mechanical properties of the subglacial environment. The main objective of this study was to develop a model of glacitectionic deformation and its sedimentary record beneath fast and slow flowing ice sheets, based on investigations conducted in Wielkopolska (west central Poland). Sedimentary structures, mainly at the contact between subglacial tills and glacifluvial sediments, were recognized to delineate typical facies associations in a Weichselian glacigenic succession. Each association was interpreted as a record of the different depositional environments related to different subglacial conditions. Those investigations suggest the substratum was composed of frozen and dry, and wet and mobile spots, and four thermo-mechanical facies were distinguished: A – is representative of slower ice flow, dry and cold subglacial conditions, where driving stresses and normal effective pressure were high; B – is also related to slow ice flow and occurrence of cold subglacial permafrost, but with little amount of unfrozen water (however, higher than in facies A), with similar physical characteristics of the ice sheet as facies A; thermo-mechanical facies C and D represent wet and warm ice sole, with low normal effective pressure and driving stresses, thus lowering sediments’ shear strength and enabling high ice-flow velocities. We suggest that these facies have specific and non-random location, thereby revealing the relationship between subglacial thermo-mechanical conditions and ice sheet dynamics. Slow moving, cold-based ice occurred along ice sheet margins and inter-stream areas, whereas fast-moving, warm-based, well-lubricated ice, was typical of the axial parts of ice streams.

Characterisation and functionality of fructo-oligosaccharides affecting water status of strawberry fruit (Fragraria vesca cv. Mara de Bois) during postharvest storage

Water status and analyses of free sugars, sugar-alcohols and fructo-oligosaccharides (FOS) were carried out in Fragaria x vesca treated with different high CO(2) concentrations applied to minimise damage caused by storage at 0°C. The thermodynamic parameters such as the amount of unfrozen water (U(w)), T(g), T(g)('), and peak position of the O-H stretching vibration were determined in various saccharides including FOS (1-kestose, nystose and kestopentaose) by infrared spectroscopy studies and differential scanning calorimetry. Beneficial high CO(2) treatment (20%) avoided the reduction of unfreezable water fraction and increased endogenous FOS levels, in contrast to that observed in air-stored and in those exposed to higher CO(2) levels (40%). The direct FOS-water interaction, possibly within the hydrogen-bond network of cellular structures, could explain the maintenance of water status, cell integrity and the low water leakage levels in 20% CO(2)-treated fruit at values similar to those found in freshly harvested fruit.

Effects of soil organic matter composition on unfrozen water content and heterotrophic CO 2 production of frozen soils

Several recent studies have highlighted the importance of soil organic matter (SOM) mineralization at high latitudes during winter for ecosystem carbon (C) balances, and the ability of the soil to retain unfrozen water at sub-zero temperatures has been shown to be a major determinant of C mineralization rates. Further, SOM is believed to strongly influence the liquid water contents in frozen surface layers of boreal forest soils and tundra, but the mechanisms and specific factors involved are currently unknown. Here we evaluate the effects of the chemical composition of SOM on the amount of unfrozen water, the pore size equivalents in which unfrozen water can exist, and the microbial heterotrophic activity at sub-zero temperatures in boreal forest soils. To do this, we have characterized the chemical composition of SOM in forest soil samples (surface O-horizons) using solid state CP-MAS (cross polarization magic angle spinning) NMR spectroscopy. The acquired information was then used to elucidate the extent to which different fractions of SOM can explain the observed variations in unfrozen water content, pore size equivalents, and biogenic CO 2 production rates in the examined soil samples under frozen conditions (−4 °C). The data evaluation was done by the use of principal component analysis (PCA) and projections to latent structures by means of partial least square (PLS). We conclude that aromatic, O-aromatic, methoxy/ N-alkyl and alkyl C are the major SOM components affecting frozen boreal forest soil’s ability to retain unfrozen water and sustain heterotrophic activity (95% confidence level). Our results reveal that solid carbohydrates have a significant negative impact (95% confidence level) on CO 2 production in frozen boreal spruce forest soils, in contrast to the positive effects of carbohydrate polymers during unfrozen conditions. We conclude that the hierarchy of environmental factors controlling SOM mineralization changes as soils freeze. The effect of SOM composition on pore size distribution and unfrozen water content has a superior influence on SOM mineralization and hence on heterotrophic CO 2 production of frozen soils.

Estimating the stability of unprotected embankment in warm and ice-rich permafrost region

Abstract The purpose of this study is to estimate the stability of unprotected embankment in the warm and ice-rich permafrost (WIRP) region along the Qinghai–Tibet Railway. The estimation was based on field observations of the varying thermal regime under the unprotected embankments and of the ongoing settlement of this type of embankment. The observed data shows that on the one hand, the unprotected embankment could mitigate the frost heave of the subgrade by homogenizing the geothermal gradient and by decreasing the temperature fluctuation of the WIRP layers. On the other hand, leaving the embankment unprotected has led to the warming of the underlying WIRP layer. This layer releases a considerable amount of unfrozen water. However, the released water undergoes untimely drainage, leading to the ongoing settlement of the embankment. To stabilize the settlement, two recommendations are provided. For those existing unprotected embankments, using shading boards to cool down the underlying permafrost is recommended. For the future embankments constructed in WIRP regions, the inset trenches which are drilled perpendicularly to traffic are recommended to aid the drainage of the released water.

Water availability controls microbial temperature responses in frozen soil CO2 production

AbstractSoil processes in high‐latitude regions during winter are important contributors to global carbon circulation, but our understanding of the mechanisms controlling these processes is poor and observed temperature response coefficients of CO2 production in frozen soils deviate markedly from thermodynamically predicted responses (sometimes by several orders of magnitude). We investigated the temperature response of CO2 production in 23 unfrozen and frozen surface soil samples from various types of boreal forests and peatland ecosystems and also measured changes in water content in them after freezing. We demonstrate that deviations in temperature responses at subzero temperatures primarily emanates from water deficiency caused by freezing of the soil water, and that the amount of unfrozen water is mainly determined by the quality of the soil organic matter, which is linked to the vegetation cover. Factoring out the contribution of water limitation to the CO2 temperature responses yields response coefficients that agree well with expectations based on thermodynamic theory concerning biochemical temperature responses. This partitioning between a pure temperature response and the effect of water availability on the response of soil CO2 production at low temperatures is crucial for a thorough understanding of low‐temperature soil processes and for accurate predictions of C‐balances in northern terrestrial ecosystems.

Measurement of unfrozen water content and relative permittivity of frozen unsaturated soil using NMR and TDR

The soil-freezing characteristic, the relationship between unfrozen water content and temperature, is relevant for any mass transfer processes in frozen porous media. To determine the soil-freezing characteristic, we simultaneously measured liquid water content and relative permittivity of various unsaturated soils at above-zero and subzero temperatures by using pulsed nuclear magnetic resonance (NMR) and time-domain reflectometry (TDR). The dielectric permittivity of frozen soil decreased with a decrease in temperature, which was accompanied by a decrease in liquid (unfrozen) water content. Frozen soils with different total water content had the same amount of unfrozen water at below − 1 °C; however, the permittivity of frozen soil depended on the total water content. A dielectric mixing model without considering reduced dielectric permittivity due to surface forces and ice formation could only describe the data for sandy soils. We expanded the mixing model by including reduced dielectric permittivity due to surface forces and ice formation. The estimations of liquid water content using the expanded mixing model were in agreement with the values measured by NMR at any soil type, total water content, ice content, and temperature.

Contributions of matric and osmotic potentials to the unfrozen water content of frozen soils

Recent reports show that biogeochemical processes continue when the soil is frozen, but are limited by water availability. However, there is little knowledge about the interactive effects of soil and environmental variables on amounts of unfrozen water in frozen soils. The aims of this study were to determine the contributions of matric and osmotic potentials to the unfrozen water content of frozen soil. We determined the effects of matric and osmotic potential on unfrozen water contents of frozen mineral soil fractions (ranging from coarse sand to fine silt) at − 7 °C, and estimated the contributions of these potentials to liquid water contents in samples from organic surface layers of boreal soils frozen at − 4 °C. In the mineral soil fractions the unfrozen water contents appeared to be governed solely by the osmotic potential, but in the humus layers of the sampled boreal soils both the osmotic and matric potentials control unfrozen water content, with osmotic potential contributing 20 to 69% of the total water potential. We also determined pore size equivalents, where unfrozen water resides at − 4 °C, and found a strong correlation between these equivalents and microbial CO 2 production. The larger the pores in which the unfrozen water is found the larger the microbial activity that can be sustained. The osmotic potential may therefore be a key determinant of unfrozen water and carbon dynamics in frozen soil.

Unfrozen water in amylosic molecules is dependent on the molecular structures—A differential scanning calorimetric study

The amount of unfrozen water (UFW) associated with linear and cyclic (1→4)- α- d-glucans and oligomers thereof, including maltopentaose, two enzymatically synthesized amyloses; A-55 ( M w=54,500) and A-820 ( M w=820,000), three cyclodextrins; α-CD, β-CD and γ-CD and two cycloamyloses; CA-5 ( M w=4700) and CA-13 ( M w=13,100) were determined by differential scanning calorimetry (DSC). UFW, estimated from a plot of the melting enthalpy of ice against the weight fraction of water, showed that the glucans examined contain surprisingly different amounts of UFW. The molar ratio of UFW per glucose residue was increased in the order of α-CD (1.24), β-CD (1.78), γ-CD (1.96), A-55 (2.77), A-820 (2.98), CA-5 (2.93) and CA-13 (3.52). These values can be interpreted in terms of their hydrated conformational structures.

The effect of sucrose on unfrozen water and syneresis of acidified sodium caseinate–xanthan gels

The influence of the ingredients of acidified Na caseinate–xanthan–sucrose gels on thermophysical properties and syneresis of the gels was studied. Sucrose concentration affected all of the gel equilibrium properties and the rate of syneresis. The positive effect of sucrose on syneresis and unfrozen water (UFW) values was attributed to different effects. The amount of UFW was governed mainly by the colligative properties of sucrose whereas the equilibrium syneresis behaviour was associated with the changes in network dynamics caused by the kosmotropic properties of sucrose. The latter could enhance xanthan–sucrose association or favour xanthan–protein interactions.

Interactions between glaciers and permafrost: an introduction

Abstract A consideration of the interactions between glaciers and permafrost is essential to many environmental studies of cold regions. This paper reviews how concepts, field data and experimental studies from glaciology and geocryology can provide a basis for improved understanding of some of the key glacier-permafrost interactions at scales ranging from continental ice sheets to small proglacial streams. Glacitectonic processes are strongly influenced by water pressures beneath subglacial and proglacial permafrost, and by the amount of unfrozen water within the permafrost. Burial of glacier ice and growth of intrasedimental ice also occur within sub- and proglacial permafrost, and together they produce a complex assemblage of ground ice in glaciated frozen lowlands. In mountain regions, rock glaciers are associated with the presence of ground ice, and represent a landform that stradles the semantic fence separating glacial features from permafrost features. In proglacial and ice-marginal environments, geomorphological activity reflects the combined effects of glacially- and periglacially-conditioned processes operating synchronously in adjacent areas, or in succession; such activity includes the transport of sediment in glacierized catchments and the calving of glacial ice in ice-marginal lakes. Interaction between permafrost and glacial phenomena depends largely on their proximity: where permafrost occurs close to glaciers, the thermal regime of the active layer is influenced in part by the surface covering of adjacent glacial ice through its effect on albedo and ground heat flux. Glacier-permafrost interactions are particularly important in recently deglaciated terrain, where permafrost may be aggrading. This ‘paraglacial’ zone often shows rapid geomorphological change. Thus, glacier-permafrost interactions are complex and occur over a wide range of temporal and spatial scales.

The cryoprotectant effect of shrimp chitin and shrimp chitin hydrolysate on denaturation and unfrozen water of lizardfish surimi during frozen storage

Shrimp chitin and shrimp chitin hydrolysate prepared from black tiger ( Penaeus monodon), endeavour ( Metapenaeus endeavouri) and giant freshwater ( Macrobrachium rosenbergii) prawns were added to lizardfish surimi, and it was frozen and stored at −25 °C for 6 months to evaluate freeze-induced protein denaturation. Changes in total Ca-ATPase activity and the amount of unfrozen water in samples were periodically determined during frozen storage. The surimi containing shrimp chitin showed the same freeze-denaturaion rate ( K D) as the surimi without cryoprotectants (control), and the amount of unfrozen water was lower than that of control. However, surimi containing shrimp chitin hydrolysates showed K D values equal to surimi containing sucrose or glucose but lower than the control, and the amount of unfrozen water was increased compared to control. The results revealed that shrimp chitin hydrolysates retarded the effects on freeze-induced denaturation by stabilizing the hydrated water molecules that surround the protein.