Excess Water Content Research Articles

Heat capacity and thermodynamics of a synthetic two-line ferrihydrite, FeOOH·0.027H2O

Ferrihydrite is a fine-grained and variable, in terms of structure and water content, iron oxyhydroxide found in many geologic environments, in living organisms, and in environmental pollution. The thermodynamic study of ferrihydrite is important for understanding geochemical transformations involving iron as well as in the study of iron in chemical synthesis and biological systems. In this study, the heat capacity of a synthetic two-line ferrihydrite, which showed typically broad X-ray diffraction peaks due to small particle size and/or disorder but had a rather low excess water content, FeOOH·0.027H2O, was measured over the temperature range of (2 to 300)K. Using these data, the standard molar entropy, Smo, of this two-line ferrihydrite was calculated to be (71.7±0.2)J·K−1·mol−1, while that of the stoichiometric (no excess water) material, FeOOH was estimated to be (69.8±0.2)J·K−1·mol−1. These measured entropies are in moderate agreement with, though slightly higher, than those estimated much more indirectly by Majzlan et al. (2004) [15] The heat capacity data below T=12K were fit to theoretical models to study the underlying contributions to the heat capacity. The fit required an anisotropic ferrimagnetic spin wave component, which agrees with studies that characterize two-line ferrihydrite as a ferrimagnet. The fit also required a linear term, which most likely stems from defects in the ferrihydrite particles. Using enthalpy of formation from the elements −(542.3±0.8kJ·mol−1 for FeOOH·0.027H2O or −(534.6±1.0)kJ·mol−1 for FeOOH obtained from acid solution calorimetry of the same sample, the standard Gibbs energy of formation from the elements for this ferrihydrite sample was calculated to be −(473.0±1.0)kJ·mol−1 for FeOOH·0.027H2O and −(465.3±1.0)kJ·mol−1 for FeOOH.

The importance of water in the polyol synthesis of carbon supported platinum–tin oxide catalysts for ethanol electrooxidation

Sn-modified platinum catalysts are presently one of the most active catalysts for the room temperature electrooxidation of ethanol at low potentials. In this study, Pt–SnOx/C catalysts are prepared by the polyol method in different ethylene glycol–water mixtures using a Pt:Sn atomic ratio of 3 in the preparation solution. When the water content in the synthesis is very low (2vol.%), only a limited amount of Sn can be incorporated into the catalyst (Pt:Sn atomic ratio of 91:9). Increasing the water content in the synthesis increases the Sn content and the intrinsic activity for ethanol electrooxidation by the “bifunctional catalysis” mechanism; however, water content in excess of 50vol.% is counterproductive since there is a corresponding growth in the catalyst particle size which results in a reduction of the electrochemically active surface area (ECSA). Experimentally a 50:50 (vol./vol.) mixture of ethylene glycol and water is the most effective since all the precursor metals in the preparation solution can be completely transferred to the target catalyst. The advantages are not only limited to composition control (concordance of catalyst composition and solution composition in preparation), but also a small particle size (∼2.2nm) and the highest mass activity.

Compressing fresh concrete technique and the effect of excess water content on physical–mechanical properties of compressed concrete

This paper offers an innovative practical technique for applications in which high workability concrete is needed. In this technique, concrete is produced by compressing the fresh concrete through a fabricated pressure apparatus without incorporating additives and no need for external vibration and workability control. Applying this technique, excess water is completely expelled out from the fresh concrete and porosity is remarkably decreased. In this study, several mixes having different excess water contents with the same cement and aggregates were prepared to attain different workability levels. To evaluate the effect of excess water content on properties of hardened concrete, the physical and mechanical properties of both compressed and uncompressed concrete were determined, including compressive strength, modulus of elasticity, strain at peak stress, stress–strain curve, failure mode, water absorption, density and ultrasonic pulse velocity. The results obtained from this study showed that the excess water content added to the fresh concrete does not influence the physical–mechanical properties of the compressed concrete while those of the uncompressed concrete are significantly degraded. Moreover, compressing the fresh concrete dramatically improves the properties of the compressed concrete, as compared to the corresponding uncompressed concrete.

Porosity of dental phosphate-bonded investments after setting and heating processes

Porosities of set and burnout compacts of phosphate-bonded investments were determined. A gas pycnometer was used to measure the volumes, and hence the densities, of fine powders and porous compacts. Porosities of set and burnout compacts were then obtained from these data for as-received powders and dry set compacts by a numerical simulation method, subsequently leading on to the estimated compositions of conventional and rapid-heating investments used in this study. Excess water content in the hardening investment compact was evaluated as a function of setting time elapsed from the start of mixing. Porosities were about 24-32% for set compacts and 43% for burnout compacts, which well agreed with the numerically computed results. It was concluded that the functional composition of investment powder needed to achieve the optimal porosity as well as process parameters such as water-powder (W/P) ratio and keeping time of mixed investment casting slurry before heat treatment could be determined using the numerical simulation method developed in this study.

Porosity of dental gypsum-bonded investments in setting and heating process

The porosity of gypsum-bonded investments for set and heated compacts was measured and theoretically computed quantitatively, because porosity is an effective factor for determining the strength, setting/heating expansion, and permeability of compacts at casting. A helium gas pycnometer was used to measure the solid volume of fine powders, powder-water mixtures, and porous compacts. The compositions of the conventional cristobalite investment and rapid-heating type investment were estimated from the measured solid densities of the as-received powders and the set investments. The porosity and water content of the set investments were determined from the experimental data. Excess water content in the set investment was calculated in relation to the elapsed time from the start of mixing with water. The experimental porosities of the set and heated investments were about 40% for dry set >compacts and about 50% for fired compacts, which well agreed with the numerically computed estimations, respectively.

Managing irrigation of fruit trees using plant water status

Optimum growth and production of fruit crops is strongly linked to managing irrigation water. Various method of estimating tree water requirements have been utilized such as direct and indirect soil, water, and climatic measurements. Due to differences in fruit tree anatomical and morphological structures and their adaptation to excess and deficit soil water content, such estimates of irrigation water requirements may be more suitable for herbaceous plants but not as accurate for trees. Studies on temperate and tropical fruit trees, using apple (Malus domestica) and star-fruit (Averrhoa carambola), respectively, showed that tree water potential is highly correlated to soil water status. Irrigation based on climate data (ET) and monitoring of soil water resulted in no significant differences in soil or tree water status of orchard-grown fruit trees under temperate and subtropical climatic conditions. The results indicated the need for better understanding and utilization of tree physiological parameters for management of irrigation water of fruit crops. This will ultimately lead to achieving optimum yield and fruit quality while conserving water resources.

Effect of Water Table Management and Irrigation on Potato Yield

In Canada, the Province of Manitoba is the second largest potato producer after Prince Edward Island. Potato is a moisture-sensitive crop, and excess or inadequate soil water content can adversely affect the yield and quality. Potato in Manitoba experiences periods of excess as well as insufficient water content within the soil profile during the growing season. The objective of this study was to compare the effect of four different water management treatments on potato yield in a fine sandy loam soil in southern Manitoba: controlled drainage with subirrigation (CDSI), free drainage with overhead irrigation (FDIR), no drainage with overhead irrigation (NDIR), and no drainage with no irrigation (NDNI). In November 2009, tile drains were installed at a depth of 0.9 m. CDSI was done through drainage control structures with a target water table depth of 0.6 m. Overhead irrigation was done using a traveling gun. Groundwater level, drainage discharge, and potato yield data were collected during the 2010 and 2011 growing seasons. In 2010, potato yield was not found to be significantly different between the treatments due to the large variability between the replicates. However, in 2011, potato yield from the FDIR treatment was significantly higher compared to NDNI and CDSI (p <0.05). The NDNI treatment yield was significantly lower (p < 0.05) than the other three treatments. When compared with NDNI, the other treatments showed a yield increase of 15% to 32%. Maintaining adequate soil moisture by overhead irrigation was most effective for increasing potato yield when rainfall is inadequate.

Tree species distribution on mafic and felsic fells in Finnish Lapland

Physical–chemical properties of glacial tills, derived from felsic or mafic lithologies, were studied in the forest, treeline, and on tundra in western Finnish Lapland. Scots pine [Pinus sylvestris L.] dominated on felsic fells, but excess soil water content was found edaphically constraining for pine. Low soil electrical conductivity (ECa) and low Ca to Al ratios was found to constrain Norway spruce [Picea abies (L.) Karst.]. The soil ECa positively correlated with soil Mg, Na, and Ca, but negatively with Al signifying the distribution of spruce to be associated with mafic lithologies. The limit of mountain birch [Betula pubescens ssp. Czerepanovi Hämet-Ahti] was below the conifer krummholz-zone. In winter, the treeline soil was unfrozen beneath the snowpack, whereas subzero temperatures applied to forest and tundra. In spring, soil water became available weeks before final melting of snowpack, while soil temperature (ST) increased notably above 0oC three weeks after the disappearance of snow. Early season ST was not attributed to elevation or aspect. Mid-season ST was highest on tundra. We contend that, instead of ST, water or N availability, winter winds, and spatial distribution of snow are crucial with regard to spreading of tree species on the studied fells.

Hydraulic Conductivity of Geosynthetic Clay Liners Exhumed from Landfill Final Covers with Composite Barriers

Geosynthetic clay liners GCLs were exhumed from composite barriers, i.e., geomembrane over GCL in final covers at four sites after 4.7 to 6.7 years to evaluate the in-service condition. Monovalent bound cations were replaced by divalent cations in all GCLs, with near complete exchange at two-thirds of the sampling locations. Hydraulic conductivity was measured using two dilute solutions commonly used as permeant water: standard water SW, 0.01M CaCl2 solution and type II deionized water DW. Hydraulic conduc- tivities to SW varied over four orders of magnitude, whereas identical specimens i.e., from same sample had hydraulic conductivities to DW consistently 310 10 m /s. Higher hydraulic conductivities and sensitivity to permeant water did not correspond directly to the amount of cation exchange. Exhumed GCLs with higher gravimetric higher water contents 50% exhibited a gel structure indicative of osmotic hydration and had lower hydraulic conductivities to both SW and DW, regardless of the amount of sodium Na replaced by divalent cations. These GCLs with higher water contents were placed on subgrade having water content in excess of optimum water content standard Proctor. Conditions that promote rapid hydration and osmotic swell in a GCL are recommended to ensure that a GCL in a composite barrier maintains low hydraulic conductivity 510 11 m /s, even if the native Na is ultimately replaced by divalent cations. Subgrade with water contentoptimum water content is recommended. DOI: 10.1061/ASCEGT.1943-5606.0000407 CE Database subject headings: Geosynthetics; Clay liners; Landfills; Hydraulic conductivity; Barriers; Composite materials; Water content. Author keywords: Geosynthetic clay liner; Landfill; Final cover; Hydraulic conductivity; Cation exchange; Hydration; Osmotic swell; Crystalline swell; Preferential flow.

WO3 thin film coating from H2O-controlled peroxotungstic acid and its electrochromic properties

We prepared PTA coating solution by hot plate evaporation, N2 bubbling evaporation, and rotary evaporation. N2 bubbling and rotary evaporation are very efficient way to synthesize PTA which reduces the synthesis process time to 1/5, compared to hot plate evaporation method. Another strong point is that N2 bubbling and rotary evaporation make it possible to control excess hydrogen peroxide and water contents in PTA. The PTA formula were WO3·0.13H2O2·10.0H2O for hot plate method, WO3·0.16H2O2·7.1H2O for N2 bubbling method, and WO3·0.15H2O2·3.00H2O for rotary evaporation method. Thermal analysis and mass spectroscopy analysis show that water is evaporated at around 100 °C and hydrogen peroxide is dissociated at the range of 150 and 250 °C. Amorphous phase of WO3 thin film prepared from rotary evaporated PTA solution has the best electrochromic property, light transmission difference from 91% at its bleached state and 5.5% colored state, and charge density of 22 mC/cm2. It is thought that the control of excess hydrogen peroxide and water contents in PTA is very important to enhance the electrochromic properties of WO3 thin film.

Effects of temperature gradient reduction in three different carbon dioxide absorbents

Temperature gradients in CO2 absorbents may locally increase the water content by condensation. We hypothesized that temperature gradient reduction (TGR) would prevent increased water content, thus preserving the reactivity of the CO2 absorbent and thereby increasing its time to exhaustion (longevity). The purpose of this study was to compare the effects of TGR on the longevity of CO2 absorbent with three different types of CO2 absorbents. We constructed a novel TGR canister. Experiments were conducted using three different types of CO2 absorbents: Drägersorb 800 Plus (D800), Drägersorb Free and Amsorb Plus. One kilogram of fresh CO2 absorbent of each type was placed into two types of canister: the conventional control canister (n = 6) and the TGR canister (n = 6). In the case of Drägersorb Free, the TGR canister most effectively and specifically prevented local increase in water content of the CO2 absorbent and markedly increased the longevity (30% increase) compared with the control canister. In the case of Amsorb Plus, the TGR canister also prevented local excessive water content, but the increase in longevity was smaller (17% increase). In the case of D800, the TGR canister markedly increased the longevity (27% increase), but its prevention of local excessive water content was smaller. TGR is a useful method to prevent local increase in water content and improve the longevity of CO2 absorbent. The effectiveness of TGR on longevity and water content changes varied in the different types of CO2 absorbent.

In situ observation of the water distribution across a PEFC using high resolution neutron radiography

The water distribution across the membrane electrolyte assembly (MEA) of a working polymer electrolyte fuel cell (PEFC) was observed in situ using neutron radiography. In order to resolve the distribution between the different layers of the MEA, in plane imaging (cell membrane parallel to the beam) was used. Unprecedented spatial resolution for neutron radiography was obtained using a new detector system available at PSI combined with specific anisotropic resolution enhancement methods. A detrimental effect on performance of excessive water content in the cathode GDL was observed. Depending on the operating condition, a strong separation of the water content between ribs and channel was observed, particularly in the cathode GDL.

Effects of packing density, excess water and solid surface area on flowability of cement paste

Although it has been postulated for many years that it is excess water rather than whole water that lubricates the cementitious materials and governs flowability of paste (excess water is water in excess of that needed to fill up voids), there has been no detailed investigations to study the actual effects of excess water. This was due to the lack of a suitable method for measuring the packing density and voids content of cementitious materials. To resolve the problem, the authors have recently developed a new wet packing method that was applied herein to measure the packing densities and voids contents of cementitious materials containing different amounts of cement, pulverised fuel ash and condensed silica fume. The flowability properties of the paste formed of the cementitious materials with different water contents were also measured and correlated to the excess water contents, each determined as water content minus voids content. The results revealed that whereas an improvement in packing density would increase excess water content, flowability is governed mainly by excess water to solid volume and excess water to solid surface area ratios.

The PDM rainfall-runoff model

Abstract. The Probability Distributed Model, or PDM, has evolved as a toolkit of model functions that together constitute a lumped rainfall-runoff model capable of representing a variety of catchment-scale hydrological behaviours. Runoff production is represented as a saturation excess runoff process controlled by the absorption capacity (of the canopy, surface and soil) whose variability within the catchment is characterised by a probability density function of chosen form. Soil drainage to groundwater is controlled by the water content in excess of a tension threshold, optionally inhibited by the water content of the receiving groundwater store. Alternatively, a proportional split of runoff to fast (surface storage) and slow (groundwater) pathways can be invoked with no explicit soil drainage function. Recursive solutions to the Horton-Izzard equation are provided for routing flows through these pathways, conveniently considered to yield the surface runoff and baseflow components of the total flow. An alternative routing function employs a transfer function that is discretely-coincident to a cascade of two linear reservoirs in series. For real-time flow forecasting applications, the PDM is complemented by updating methods based on error prediction and state-correction approaches. The PDM has been widely applied throughout the world, both for operational and design purposes. This experience has allowed the PDM to evolve to its current form as a practical toolkit for rainfall-runoff modelling and forecasting.

Effect of water content on transparency, swelling, lidocaine diffusion in p-HEMA gels

The dependencies of transparency, swelling and lidocaine diffusion on the water content in the polymerizing mixture are investigated for p-HEMA gels. The water fraction in the polymerizing mixture (WCIPM) is varied from 20 to 60%. The results show that p-HEMA gels with WCIPM less than 50% stay transparent, while those with larger WCIPM lose transparency to an extent that is proportional to the water content in excess of 50%. Also the gels with WCIPM > 50% are transparent above a wavelength of about 1000 nm, which suggests that these gels contain roughly pores that are a few microns in size. The gels with excess water also show a porous morphology in SEM studies. The gels with WCIPM less than 50% show almost identical microstructure and similar swelling and drying behavior. The partition coefficient of lidocaine partition coefficient in p-HEMA gels depends strongly on the aqueous drug concentration, which suggests binding of the lidocaine molecules on the gel. The binding of the drug to the p-HEMA matrix can be described by Langmuir isotherm and a diffusion model that includes binding of the drug to the polymer accurately models the drug uptake dynamics. The results of the model show that the diffusivity of the drug in the gels is independent of the water content for WCIPM < 50% and becomes larger on crossing the critical WCIPM value of 50%.

A Direct Tensile Strength Testing Method for Unsaturated Geomaterials

Abstract The current paper presents a new method for testing direct tensile strength of unsaturated geomaterials, guided by a method developed for concrete testing (Hannant et al. 1999). The developed equipment is used for measurement of direct tensile strength of unsaturated reactive basaltic clay soils and crushed rocks stabilized with cementitious additives. The tensile characteristics of soils were tested at water contents in excess of liquid limit and those close to optimum water content. Stabilized crushed rocks were tested at early and cured states after mixing. Full stress-strain characteristics were measured with the aid of precision transducers and electronic data acquisition. The equipment is capable of measuring tensile strengths of soil slurries (about 1 kPa), as well as cement stabilized crushed rocks (up to about 1 MPa).

Laser-ablation ICP-MS analysis of silicate and sulfide melt inclusions in an andesitic complex II: evidence for magma mixing and magma chamber evolution

Laser-ablation microanalysis of a large suite of silicate and sulfide melt inclusions from the deeply eroded, Cu-Au-mineralizing Farallón Negro Volcanic Complex (NW Argentina) shows that most phenocrysts in a given rock sample were not formed in equilibrium with each other. Phenocrysts in the andesitic volcano were brought together in dominantly andesitic—dacitic extrusive and intrusive rocks by intense magma mixing. This hybridization process is not apparent from macroscopic mingling textures, but is clearly recorded by systematically contrasting melt inclusions in different minerals from a given sample. Amphibole (and rare pyroxene) phenocrysts consistently contain inclusions of a mafic melt from which they crystallized before and during magma mixing. Most plagioclase and quartz phenocrysts contain melt inclusions of more felsic composition than the host rock. The endmember components of this mixing process are a rhyodacite magma with a likely crustal component, and a very mafic mantle-derived magma similar in composition to lamprophyre dykes emplaced early in the evolution of the complex. The resulting magmas are dominantly andesitic, in sharp contrast to the prominently bimodal distribution of mafic and felsic melts recorded by the inclusions. These results severely limit the use of mineral assemblages to derive information on the conditions of magma formation. Observed mineral associations are primarily the result of the mixing of partially crystallized magmas. The most mafic melt is trapped only in amphibole, suggesting pressures exceeding 350 MPa, temperatures of around 1,000 °C and water contents in excess on 6 wt%. Upon mixing, amphibole crystallized with plagioclase from andesitic magma in the source region of porphyry intrusions at 250 MPa, 950 °C and water contents of 5.5 wt%. During ascent of the extrusive magmas, pyroxene and plagioclase crystallized together, as a result of magma degassing at low pressures (150 MPa). Protracted extrusive activity built a large stratovolcano over the total lifetime of the magmatic complex (>3 m.y.). The mixing process probably triggered eruptions as a result of volatile exsolution.

Phonon, Spin-Wave, and Defect Contributions to the Low-Temperature Specific Heat of α-FeOOH

The specific heat of α-FeOOH was measured in the temperature range 0.6 to 30 K by a combination of semi-adiabatic and isothermal techniques. A broad specific-heat anomaly was detected at approximately 1 K. The data above this anomaly were fitted to the equation C=B asw T 3 e −Δ/T +∑ B n T n, where ∑ B n T n represents the harmonic-lattice model for the lattice specific heat, and B asw T 3 e −Δ/T represents the magnetic specific heat. The e −Δ/T term that modifies the usual T 3 term for an antiferromagnetic spin-wave contribution accounts for a spin-wave gap in the spin-wave spectrum, where Δ is the width of the spin-wave gap in Kelvin. As expected, the root-mean-square deviation (RMS) of the fit decreased progressively with inclusion of additional lattice terms, but the Debye temperature, Θ D , and the spin-wave gap, Δ, remained essentially unchanged. The addition of a linear term, γT, decreased the RMS of the fit and eliminated the need for an excessive number of lattice terms. The γT contribution to the specific heat, rather than being electronic in nature, is associated either with a small number of Fe3+ vacancies, or with loosely bound particles vibrating in defect sites in the crystallite interfaces. The possibility of the existence of vacancies is implied by the excess water content in the sample (0.083 moles of H2O per mole of FeOOH) and the presence of the interfaces is indicated by the particle size (determined by BET surface area measurement) being larger than the individual crystallite size (determined by X-ray diffraction).

Dynamics of a complex mass movement triggered by heavy rainfall: a case study from NW Turkey

Following a period of heavy precipitation, a large and complex mass movement, namely the Dagkoy landslide, occurred in the West Black Sea Region of Turkey on May 21, 1998. This paper describes the conditioning factors of the landslide and interprets the mass transport processes in terms of a movement scenario. Geology, geomorphology and vegetation cover were considered as the conditioning factors of the failure. Observations showed that the gently sloping (about 10°) area is mostly covered by dense forest trees at the crown where the motion initiated. Significant intersection of the collapsed slope with dip of the local marls seems to have contributed to the formation and geometry of the landslide. The distance from the crown down to the toe of the landslide measured more than 600 m, with about 0.6 km 3 total earth material displaced. The landslide has both a block sliding characteristics in the upper portions and a debris flow/soil flow component around the margins of the sliding blocks in the middle parts and at the toe. The proposed scenario for the landslide reveals that the movement was initiated near crown as a result of the excess water content in the marls at the end of 3 days of heavy rainfall. The early perturbations (transverse cracks, ridges, etc.) lasted for 6–7 h, after which the central part of the zone started to move as a soil flow in which very large intact blocks were transported. Even though the movement was very rapid (1.2 m/min), there was no loss of life. However, the movement destroyed 38 houses, one mosque and a considerable amount of farmland.

Gelatinisation of sago starch in the presence of sucrose and sodium chloride as assessed by differential scanning calorimetry

The inhibitory effect of sucrose and sodium chloride on sago starch gelatinisation was investigated by differential scanning calorimetry (DSC). The temperature of gelatinisation of starch in the presence of low levels of water and high levels of sucrose was found to increase in the presence of sucrose, whereas the gelatinisation enthalpy was unaffected. The gelatinisation temperature range was not as broad in the presence of sucrose as without sucrose. Furthermore, the shape of the gelatinisation endotherm was changed by the addition of sucrose. The double endotherm obtained in limited water:starch systems was changed into a single endotherm, similar to the endotherm obtained in excess water:starch systems at a higher temperature. DSC was also used to examine the effects of water and sodium chloride content on the phase transitions of sago starch. Samples were adjusted to starch:water ratios of 2:3 and 3:2 in sodium chloride concentrations of 0.0, 1.0, 2.0, 3.0, 4.0, 5.0 M. The gelatinisation temperatures of sago starch increased and then decreased as the sodium chloride concentration increased. Sodium chloride created similar effects on the endotherms in excess water content and on the first endotherm with limited water content. In the presence of sucrose and sodium chloride, gelatinisation shifted to higher temperatures, and enthalpy associated with the endothermic process decreased. The extent of temperature shift and enthalpy change was dependent on the water to starch to solutes ratios.