Browsing by Subject "Water chemistry"
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Item Effect of the chemical composition of compaction water on the performance of soil subgrades and embankments(Texas Tech University, 2004-12) Ayenu-Prah, Albert YawsonThe Texas Department of Transportation (TxDOT) wants to employ the use of other water sources (alternative water) besides potable drinking water for those construction projects that use large amounts of water. This is due to increasing cost of drinking water treatment and, therefore, a consequent scarcity of potable water for construction purposes. The sometimes prohibitive cost of hauling water from remote areas to certain construction sites, and more importantly, issues related to performance are also part of the reason for this research effort. The research deals mainly with the investigation of the potential effects of the chemical composition of compaction water on the performance of soil subgrades and embankments, with an emphasis on the effects of sodium. Shaikh et al. (1988) indicate that the primary factor that influences the erodibility of unsaturated compacted clays is the soil pore-water chemistry. A comprehensive laboratory test program was carried out to ascertain the possible effects that the chemical composition of compaction water could have on engineered soils. Test results from the project would help in developing predictive models to serve as a framework for a preliminary feasibility evaluation, and selection of a particular alternative water source for use among candidate sources. Similarly, appropriate blending ratios could be determined for those water sources to meet design specifications. Varied results have been obtained that would lead to various conclusions. It was observed that even the worst sources of alternative water would have no significant effect on engineered soils.Item Experimental and theoretical studies on water(Texas Tech University, 1997-05) Cho, Chul HeeThe properties of water near surfaces or in confined volumes are not well understood. Here, the biologically relevant system chosen for studying the behavior of water near a surface is composed of small water pools encapsulated within sodium bis (2-ethylhexyl)sulfosuccinate (AOT) reverse micelles (RM's), whose surfaces are highly hydrophihc. The time-correlated single-photon counting technique together with an ultrafast laser system was employed to measure the fluorescence lifetimes of the probe molecule ANS within various RM sizes. The resulting decay data were interpreted by using the analytical method and the non-linear least squares fitting technique in order to seek a relationship between diffiision of the probe and a fast nonradiative event. By discovering these trends, information about water properties within different regions of the aqueous core of the RM can be obtained as a function of distance from a surface. The ability of the probe to undergo the fast nonradiative process depends on a reorientational relaxation tune of the water solvent, which may become orders of magnitude slower for water near a surface. Perturbations on the translational velocity autocorrelation function of the probe, as measured by the diffusion fluxes, are very large, extending nearly to the center of the largest RM studied (radius -55 A). On the other hand, perturbations on the orientation relaxation of the solvent, as measured by the probe Hfetimes, were found to extend no more than -10-15 A from the surface of any of the RM's studied. An explanation of the density maximum in water near 4 °C can be described in terms of a dense second-neighbor structure obtained from the bending of hydrogen bonds. The analytical and computational models of water, which provide an explanation of this anomaly, are proposed. In these models, the water-water potential is altered to include more realistic interactions in the second-neighbor shell. Support for this idea is provided here by considering the exactly soluble one-dimensional Takahashi fluid model and then by an NVE molecular dynamics simulation for a realistic water model.Item Investigation of relationship between select mortality rates and ground-water chemistry.(Texas Tech University, 1975-08) Mullican, Jerry WNot availableItem Investigations of diffuse intermolecular electronic systems(Texas Tech University, 1992-05) Muguet, Francis F.Diffuse intermolecular electronic systems, such as the hydrated electron or the immonia and water dimers, present both a theoretical and a practical computational challenge. The hydrated electron was discovered more than 25 years ago, yet there is still no consensus on an explanation of this phenomenon. A novel model is presented here whereby the hydrated electron consists in an itinerant dihydronium radical structure. Although electrostatically neutral, the itinerant radical is shown to behave as a negative charge carrier under the influence of an electric field. Within this perspective, the hydrated electron may be considered a quasiparticle. Contrary of the absence of agreement between many experiments and the old but still popular cavity model description, the energetics in the new model, are shown to be consistent with photophysical experimental data. In order to understand negatively charged water clusters, it is also proposed that a metastable bifurcated water dimer structure is able to bind an extra electron. Prior to our studies, no ab initio computations had been able to reproduce the experimental geometry of the ammonia dimer nor to predict a water dimer anion with Franck-Conden factors agreeing with those recently found in molecular beam experiments. In both cases the potential energy surface is determined by attractors corresponding to nonlinear and linear hydrogen bonded geometries, respectively. One attracter receives an unfair advantage in the computational procedure mainly because of the basis set superposition error (ESSE). There is still no agreement on a scheme for correcting the ESSE. A widely employed error estimation method is the counterpoise correction. A completely different new method is proposed using reerthonermalizatien of purified localized molecular orbitals. In terms of a ESSE corrected potential energy surface of the water dimer, a multi-attractor model of water is very briefly discussed. For further water molecular dynamics studies, we offer a new algorithm which we have developed specifically for a massively parallel computer.Item Lithium, boron, and barium in formation waters and sediments, Northwestern Gulf of Mexico Sedimentary Basin(1989) Macpherson, Gwendolyn Lee, 1953-; Land, Lynton StuartLithium, boron and barium, found in varying abundances in formation waters of the Gulf of Mexico Sedimentary Basin (Gulf Basin), have contrasting origins and are useful in assessing the open or closed nature of hydrocarbon-producing aquifers in Texas and Louisiana. Dissolved barium concentrations are controlled primarily by barite. Barium contents of sandstones show that either the barium content of dissolved or albitized detrital feldspars was considerably higher than in detrital feldspars which remain unaltered or that the original feldspar content of the sandstones was higher than that of the least altered sandstone analyzed. Boron and lithium contents are more difficult to attribute to local diagenesis. Most formation waters contain low concentrations of lithium (less than 10 mg/L) ascribable to feldspar diagenesis, except that whole-rock sandstones increase in lithium content with increasing diagenetic alteration. Formation waters from deep reservoirs contain very high concentrations of lithium for which there is no apparent local source. These waters do not resemble waters residual from either marine or non-marine evaporite deposition. Boron in most formation waters cannot originate exclusively from organic matter unless organic matter contents are much higher than have been measured, nor does it come from volcanic sediments because these are abundant only in the South Texas region while high boron contents are not geographically restricted. Formation waters from deep reservoirs contain very high concentrations of boron which probably come from deeper in the Basin because clay minerals, the major reservoir of boron, show no systematic decrease in boron content with depth. The 𝛿¹¹B of these waters is light (to +11%₀) and shows that the boron is not seawater boron (+40%₀) or boron from Jurassic evaporites (+31%₀). The 𝛿¹¹B of other formation waters lies between the value for sea water and the light boron. The Gulf Basin is nearly open with respect to lithium and boron but closed with respect to barium. The high concentrations of lithium and boron probably originate deeper than the sampled part of the Gulf Basin and may be products of metamorphic processes. The source of the barium in formation waters is detrital feldspars.Item The anomalous properties of liquid water explained by a mixture model(Texas Tech University, 1996-05) Vedamuthu, Mary S.A semiempirical theory, which is a modernization of the 'mixture model,' attempting quantitatively to correlate thermodynamic and dynamic effects of bulk and interfacial liquid water with various properties of ice polymorphs is proposed here. The basic concept rests on the disappearance, on the average, with increasing temperature or pressure, of open intermolecular tetrahedral bonding (Type-I) having a density similar to that of ordinary ice, in favor of compacdy bonded regions (Type-II) with a density near that of the dense ice polymorphs particularly, ice II, III, and V. The mixture model is employed to explain quantitatively the origins of the 'anomalous' properties of liquid water - density maximum, isotope effects, thermal minimum in the isothermal compressibility curve. Strong support for this model can be found from an analysis of the accurate experimental density data of liquid H2O and D2O from the supercooled regime to about +70 °C. Published density data can be fit to this model with six- to seven-decimal-point accuracy, in the case of liquid H2O and to the reported fivedecimal-point precision, in the case of liquid DjO. The output parameters from the fits indicate the presence of capacious intermolecular bonding with a density extremely close to that of ordinary ice-Ih, intermixed with compactly bonded regions having a density near that of the common dense forms of ice. A quantitative assessment of the temperature dependence of the isothermal compressibility of liquid water at atmospheric pressure was carried out. The 'anomalous' minimum in this quantity near 50 °C is shown to emerge naturally. Independent support for this model has been provided by the differential x-ray scattering experiments of Bosio et al. Their resuhs clearly indicate that a dynamic, temperature dependent mixture of ice-I-, -II-, -III-, and -V-type bonding is present in the liquid in the manner expected for the model described in this work. Based on eariier x-ray scattering studies, Kamb reached a similar conclusion about these mixed bonding forms in liquid water. Recently, computational studies conducted by Cho, Singh and Robinson in our laboratory have indicated that the density anomaly of liquid water can be explained by utilizing this mixture model concept. Ultrafast laser methods were used to analyze the properties of liquid water confined in small volumes. This study shows that interfacial water appears to be more structured and orientationally stiffer than bulk water.