Volume and composition of the body fluid compartments are kept within narrow limits. This is done by changes in intake and excretion of water and salt. I found that changes in food intake and salt excretion play an important role in body fluid regulation during water deprivation and investigated the mechanisms of these changes. Urine volume changed little in rats deprived of water for 10 hours. The main osmoregulatory response during water deprivation was a loss of solute from the body. Food intake fell by 43%, which reduced the load of solute to the tissues and allowed absorption of water already in the gut. Water deprived rats also excreted more sodium, potassium and chloride. Thus, although rats lost 8% of their body water during 10 hours of water deprivation, plasma tonicity rose by only 2%. On rehydration, when no food was present rats rapidly reduced excretion of sodium, potassium and chloride. Rats allowed water and food drank more and excreted more solute. These changes contribute to restoration of the body fluid compartments. Brain infusions caused changes in electrolyte excretion that were similar to those seen during water deprivation and rehydration. Electrolyte excretion increased during infusion (1 $\mu$L/min for 2 h) of cerebrospinal fluid (CSF) with 300 mM NaCl in the lateral ventricle. Infusion of low-sodium CSF reduced electrolyte excretion in water deprived rats, but had little effect in rats that were not water deprived. The time course of the changes after rehydration and brain infusions was the same, and the same solutes were involved. This suggests the mechanisms are similar. Low-sodium CSF made isotonic with mannitol had the same effect as hypotonic low-sodium CSF. The sensor probably monitors brain interstitial fluid, not CSF. Food intake fell within 1 hour of water deprivation. Meals were smaller, but meal frequency did not change. Dehydration anorexia is caused by a sensor located in the gut, portal circulation or liver, because infusion of water in the stomach, jejunum or cecum (10 mL/6 h) restored food intake in rats not allowed to drink, but intravenous infusions had no effect. Intravenous infusions did not alter urinary water loss and did not alter food intake in rats allowed to drink.

No description available.

Secondary structures (e.g., fractures, sand lenses, kimberlite intrusions) can compromise the ability of clay-rich bedrock aquitards to protect underlying aquifers from near-surface contamination. To date, the effects of secondary structures on water migration and solute transport in these deposits have been poorly characterized. This study characterized the water migration and solute transport mechanisms at both a geologically simple and a geologically complex late-Cretaceous shale aquitard, with the field sites located 5 km apart in central Saskatchewan, Canada. The geotechnical properties and hydrogeologic properties of the complex aquitard were altered by kimberlite volcanism and subsequent hydrothermal alteration during its deposition (99 to 112 Ma BP). High-resolution, 1-D vertical profiles of conservative δ2H and Cl were collected from both sites (203 and 353 m deep, respectively) to define the vertical solute transport mechanisms. The shape of the 1-D tracer profiles and associated solute transport modeling from the geologically simple site suggest diffusion is the dominant transport mechanism through the entire thickness of the Lower Colorado shale aquitard (330 to 246 m above sea level, asl). Similarly, profiles through the complex, fractured, Cretaceous shale and associated modeling suggest diffusion is the dominant transport mechanism through the entire profile despite the presence of fractures; however, hydrothermal alteration during cooling of the kimberlite volcaniclastic material reduce the effective porosity (ne) of the kimberlite material from 40% to 1-5%. Results also suggest that, despite kimberlite emplacement in the study area, water migration and solute transport in the overlying and underlying Cretaceous shale may be unaffected by kimberlite volcanism and associated fracturing and alteration.

Univ., Diss., 2009--Marburg.

An understanding of solute-solute interactions is essential for aquatic systems as this can affect the fate and behaviour of micropollutants in the environment and engineered systems. Despite the importance of solute-solute interactions there is a general lack of understanding which may be attributed to the fact that many engineering models overlook solute-solute interactions and that the quantification of such interactions is inherently difficult. When solute-solute interactions are considered, they are often studied at unrepresentative concentrations and do not consider the influence of organic matter type or solution chemistry. Steroidal hormones, such as estradiol and estrone, were selected as model micropollutants as they are ubiquitous in the aquatic environment due to constant introduction of wastewater effluent, and can have implications for growth and development of organisms including impaired fertility and behavioural abnormalities. The purpose of this study was to develop a methodology to quantify solute-solute interactions at environmental concentrations, and to determine the implications of such interactions in membrane filtration. A solid-phase microextraction (SPME) technique was developed to quantify solutesolute interactions at environmental (low) concentrations. Using SPME, organic matter-water partition coefficients (log KOM) were measured for a range of steroidal hormones including estradiol, estrone, progesterone and testosterone with different organic matter types such as humic acid. The dominant mechanism of hormoneorganic matter interactions was identified as hydrogen bonding. In the case of estrone and progesterone the log KOM values were significantly influenced by organic matter type and concentration, as well as solution chemistry. No difference was observed for estradiol and testosterone due to generally weaker sorption to organic matter. Previous studies have indicated that the presence of organic matter can alter micropollutant retention in membrane filtration. Much of the current literature focuses on solute-membrane interactions, as the influence of solute-solute interactions are typically difficult to determine in membrane filtration. Therefore, hormone-organic matter interactions were studied to determine if this interaction had an influence on hormone removal by ultrafiltration (UF) using a range of molecular weight cut-off (MWCO) membranes. The results indicated increased retention of estrone in the presence of humic acid, while organic matter concentration and solution chemistry influenced retention by affecting solute-solute interactions. The findings of this study indicate the importance of solute-solute interactions in membrane filtration and experimental log KOM results were used to quantify the findings and elucidate the influences of 1) membrane sorption, 2) solute-solute interactions and 3) solute-foulant interactions. Further, the removal of steroidal hormones using a magnetic ion exchange (MIEX®) resin with a range of MWCO UF membranes was studied as such sorbents can be used to improve micropollutant removal in wastewater treatment. Greater removal with IX-UF was observed compared to UF alone and the main hormone removal mechanisms were sorption to MIEX® and solute-fouling interactions. The findings of this study indicate that it is indeed possible to quantify solute-solute interactions at environmental concentrations using SPME, with hydrogen bonding being the main mechanism of interaction for steroidal hormones and organic matter. Further, micropollutant retention by membrane filtration can be influenced by solutesolute interactions.

No description available.

This dissertation is composed of five chapters and three major contributions are presented in Chapter II, III and IV. Chapter I provided a review of studies on solute transport in aquifer-aquitard system. If the aquitard is considered, two categories of methods address the diffusive flux between the aquifer and aquitard: the old method treats the diffusive flux as a volumetric source in the governing equation of the solute transport in the aquifer; the new method treats the aquifer-aquitard boundary as a strict physical boundary with the requirement of continuity of solute concentration and the vertical flux. The new method is adopted throughout this study. In Chapter II, a review of numerical techniques on Inverse Laplace Transform is provided. By careful comparison between several popular algorithms, the multiple precision Stehfest algorithm is chosen as the method to inverse out solutions on solute transport in Laplace domain throughout this dissertation. In Chapter III, solutions were obtained for two dimensional solute transport in an aquifer-aquitard system with a divergent radial flow field, which can treat different types of solute input function and advection, longitudinal and transverse dispersion in the aquifer, vertical diffusion in the aquitard, retardation and radioactive decay in the aquifer and aquitard are taken into account. Mass exchange via diffusion between the aquifer and aquitard are investigated. The effects of hydrologic properties of the aquitard on solute transport are analyzed. Comparisons were made between the results from this study and those from previous studies. The diffusion along the aquifer-aquitard boundary was treated as a volumetric source term, and proved these solutions yield more accurate solute concentration, while those from previous studies tend to overestimate solute concentration in the aquitard, and underestimate the concentration in the aquifer. In Chapter IV, solutions were derived for the transport of radioactive isotopes in an aquifer-aquitard system with regional flow field. This study focused on the effects of different solute transport processes on the results of groundwater age dating using radiometric techniques. Chapter V summarized the remaining problems in this study and directions for future researches.

This thesis is devoted to understanding solute-solvent interactions in folded and unfolded proteins. To this end, we have studied partial molar volume, Vo, and adiabatic compressibility, KoS, of 20 amino acid side chains using low weight molecular model compounds, N-acetyl amino acid amide and its derivatives, between 18 oC and 55 oC. We used our data to develop an additive scheme for calculating the partial specific volume and adiabatic compressibility of fully extended polypeptide chains as a function of pH and temperature. We compared our calculated volumetric characteristics of the fully extended conformations of apocytochrome c and apomyoglobin with the experimental values measured in neutral pH (for apocytochrome c) or acidic pH (for apomyoglobin). The comparison between the calculated and experimental volumetric characteristics suggested that neither apocytochrome c nor apomyoglobin are fully unfolded and retain solvent-inaccessible amino acid residues. To study cosolvent-solute interactions, we determined Vo and KoS of amino acid side chains and glycyl units as a function of urea concentration. We analyzed these data within the framework of a statistical thermodynamic formalism to determine the association constants, k, for the reaction in which urea binds to each of the amino acid side chains and the glycyl unit replacing two water molecules in solvation shell. Our determined k range from 0.04 to 0.39 M with the average of 0.16 ± 0.09 M. There was no apparent correlation between the values of k and the ratio of polar to nonpolar solvent accessible surface areas. This study supports a direct interaction model in which urea denatures a protein by concerted action via favorable interactions with a wide range of protein groups. In addition, we have presented buffer ionization effect on the volume of protein denaturation could be significant with the potential to affect not only its magnitude but also its sign using a pressure perturbation calorimetric technique. Our results identified buffer ionization as an important determinant of protein transition volume that needs to be carefully taken into account. Results described in this work provide fundamental understanding of solute-solvent interaction in both folded and unfolded proteins.

Due to the complexity of nitrogen dynamics in the soil, tracer techniques are employed to estimate the fate and transport of nitrate in agricultural fields. This study was conducted to examine effects of N fertilization and landscape position on two-dimensional redistribution of bromide in a hummocky landscape, and to identify the landscape position with the greatest potential for solute loss using a dual application of Br- and 15N. The field data on Br- transport was also simulated using the HYDRUS models. The study was carried out near Brandon, Manitoba in 2007 and 2008, using two separate plots denoted as Site-2007 and Site-2008, respectively. The field plot was delineated into three landscape positions as upper (UPP), middle (MID) and lower (LOW) slope. Each landscape position received labelled K15NO3 at the rates of 0, 90 and 135 kg N ha-1, and KBr at the rate of 200 kg Br- ha-1. Site-2007 was seeded to canola while Site-2008 had winter wheat. Soil samples were taken in the fall and the following spring and were analyzed for Br-, NO3-N, total N, and isotope N ratio. Nitrogen fertilization reduced the downward movement of Br- in the soil profile, resulting in a greater lateral movement of Br- compared to the unfertilized plots. The greatest vertical and lateral movement of Br- occurred at the LOW slope. In the dual-tracer experiment, the smallest amounts of Br-, 15N, and NO3-N were measured in the soil at the LOW slope, while the greatest amounts were at the MID slope; indicating that solute loss was: LOW > UPP > MID. In the absence of crop uptake, Br- transport was identical to that of 15N. The simulation study showed that HYDRUS-1D model was inadequate to describe solute transport in the landscape, as HYDRUS-2D/3D reproduced the field data better than HYDRUS-1D. However, the 2D model did not reflect effects of landscape position and N fertility on Br- transport. Overall, the study confirmed the “Campbell hypothesis” which states that proper N fertilization reduces nitrate leaching. The field experiment and model simulation both showed that downward movement is the main pathway of solute loss in the landscape.

This thesis is devoted to understanding solute-solvent interactions in folded and unfolded proteins. To this end, we have studied partial molar volume, Vo, and adiabatic compressibility, KoS, of 20 amino acid side chains using low weight molecular model compounds, N-acetyl amino acid amide and its derivatives, between 18 oC and 55 oC. We used our data to develop an additive scheme for calculating the partial specific volume and adiabatic compressibility of fully extended polypeptide chains as a function of pH and temperature. We compared our calculated volumetric characteristics of the fully extended conformations of apocytochrome c and apomyoglobin with the experimental values measured in neutral pH (for apocytochrome c) or acidic pH (for apomyoglobin). The comparison between the calculated and experimental volumetric characteristics suggested that neither apocytochrome c nor apomyoglobin are fully unfolded and retain solvent-inaccessible amino acid residues. To study cosolvent-solute interactions, we determined Vo and KoS of amino acid side chains and glycyl units as a function of urea concentration. We analyzed these data within the framework of a statistical thermodynamic formalism to determine the association constants, k, for the reaction in which urea binds to each of the amino acid side chains and the glycyl unit replacing two water molecules in solvation shell. Our determined k range from 0.04 to 0.39 M with the average of 0.16 ± 0.09 M. There was no apparent correlation between the values of k and the ratio of polar to nonpolar solvent accessible surface areas. This study supports a direct interaction model in which urea denatures a protein by concerted action via favorable interactions with a wide range of protein groups. In addition, we have presented buffer ionization effect on the volume of protein denaturation could be significant with the potential to affect not only its magnitude but also its sign using a pressure perturbation calorimetric technique. Our results identified buffer ionization as an important determinant of protein transition volume that needs to be carefully taken into account. Results described in this work provide fundamental understanding of solute-solvent interaction in both folded and unfolded proteins.