Thesis (Ph. D.)--University of Washington, 2006. / Vita. Includes bibliographical references (leaves 121-137).

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<p><font face="Times New Roman"> <p align="left">The objective of this study was to determine the hydrosalinity fluxes associated with overland and subsurface (vadose zone) flow for different soils and land uses. For this purpose, the following data were collected during 2005 and 2006 in a typical small scale catchment located near the town of Riebeeck-Wes: weather data, hydrological and water quality measurements, soil water contents and chemistry, and vegetation growth. The area is characterized by a Mediterranean climate receiving winter rainfall of approximately 300 mm a <font face="Times New Roman">catchment is conservative, with Na</font> <font face="Times New Roman" size="1"><font face="Times New Roman" size="1">+ </font></font><font face="Times New Roman">and Cl</font><font face="Times New Roman" size="1"><font face="Times New Roman" size="1">- </font></font><font face="Times New Roman">being the dominant ions.</font></p> </font></p>

Geostatistical methods were used to find efficient and accurate means for salinity assessment using regionalized random variables and limited sampling. The random variables selected, sodium absorption ratio (SAR), electrical conductivity (EC), and clay content were measured on samples taken over an area of fifteen square miles. Ordinary kriging and co-kriging were used as linear estimators. They were compared on the basis of average kriging variance and sum of squares for error between observed and estimated values. The results indicate a significant improvement in the average kriging variance and sum of squares by using co-kriging estimators. EC was used to estimate SAR because of the high correlation between them. This was not true for clay content. A saving of two-thirds of the cost and time was achieved by using electrical conductivity as an auxiliary variable to estimate sodium absorption ratio. The nonlinear estimator, disjunctive kriging, was an improvement over co-kriging in terms of the variances. More information at the estimation site is a more important consideration than when the estimator is linear. Disjunctive kriging was used to produce an estimate of the conditional probability that the value at an unsampled location is greater than an arbitrary cutoff level. This feature of disjunctive kriging aids salinity assessment and reclamation management. A solute transport model was used to show how saptially variable initial conditions influenced the amount of water required to reclaim a saline soil at each sampling point in a simulated leaching of the area. / Graduation date: 1992

Pothole wetlands are ubiquitous throughout the Prairie Pothole Region and since 1900, 40-70% of potholes in the region have been drained to increase agricultural production. This thesis describes factors influencing spatial and temporal variations in wetland water quality and characteristics of drainage water. Research was conducted at Smith Creek watershed, southeastern Saskatchewan, where there has been controversy over recent renewed efforts to drain wetlands. Following snowmelt in 2009, 67 wetlands were sampled to determine whether spatial variations in wetland water quality were attributable to land cover, permanence classes, and surface drainage characteristics. Wetlands with cropped uplands had greater TP and K than wetlands with wooded and grassed uplands; TP, TDN, and DOC were higher in seasonally than permanently ponded wetlands; and salts were lower in wetlands with wooded uplands compared to wetlands with cropped and grassed uplands. Measurements of water quality of one permanently ponded wetland over a 20 week period in 2008 showed that the wetland acted as a solute trap. Variations in salts and DOC were influenced by hydrological processes such as runoff, evaporation, and shallow groundwater seepage, whereas variations in nitrogen, phosphorus, and bacteria were influenced by biotic, sorption, and hydrological processes. The experimental drainage of this wetland in November 2009 demonstrated that its water quality was an important control of drainage water quality. Further, the wetland ditch acted as a simple conduit, i.e., little solutes loss or gain occurred along it. In spring 2009, water quality along seven ditches and five natural connections that form between wetlands (termed spills) was compared. Concentrations of most solutes were similar, except TDN, DOC, HCO₃^-, K⁺, and Ca²⁺ that were higher in ditches than spills. Minimal changes in water quality along ditches and spills occurred, likely due to the low temperatures occurring in spring that restrict biotic processing and sorption. Notably, because ditches connect wetlands to streams, as opposed to spills that connect adjacent wetlands, ditches have a greater potential to contribute to downstream solute loading. Wetland drainage efficiency and wetland water quality were deemed the factors critical to determining solute exports via ditches. Results of wetland water quality and drainage characteristics can be useful to future modeling exercises and could be used to inform wetland drainage practices and policies.

In this thesis, a novel electrochemical array is reported. The array consists of two planar halves, each having four carbon screen-printed band electrodes (SPEs), orthogonally facing each other and separated by a spacer to yield 16 two-electrode electrochemical cells with 1 mm² working electrode areas. The 16 counter electrodes were converted to Ag/AgCl by electrodeposition and anodization. These electrodes were stable for at least 30 days with potentials under the current densities used in our experiments. The 16 working electrodes were modified by Au electrodeposition, and were examined by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). <br /><br /> Immobilization strategies for biomolecules are of paramount importance for successful fabrication of biosensors. This thesis reports a new immobilization method that is based on patterned deposition of alkyl thiosulfates (Bunte salts). Monolayers were formed through electrochemical oxidation of Bunte salts at Au-modified electrodes. Single-component and mixed monolayers were investigated, where the mixed monolayers involved one component with a terminal carboxylic acid functional group to allow immobilization of biomolecules. <br /><br /> Applications of the newly developed immobilization method to an enzyme-based biosensor and an immunosensor were investigated. Glucose and biotin were chosen as model analytes, respectively. Glucose oxidase (GOx) and avidin were covalently immobilized onto the mixed-monolayer-modified electrodes through the carboxylic acid groups. Under the optimized conditions for the fabrication and operation of the biosensors, the new electrochemical array showed linearity up to 10 mM glucose with a sensitivity of 4. 7 nA mM^-1 and a detection limit of 0. 8 mM (S/N=3), and linearity up to 12. 8 µM biotin with a detection limit of 0. 08 µM (S/N=3).

In this thesis, a novel electrochemical array is reported. The array consists of two planar halves, each having four carbon screen-printed band electrodes (SPEs), orthogonally facing each other and separated by a spacer to yield 16 two-electrode electrochemical cells with 1 mm² working electrode areas. The 16 counter electrodes were converted to Ag/AgCl by electrodeposition and anodization. These electrodes were stable for at least 30 days with potentials under the current densities used in our experiments. The 16 working electrodes were modified by Au electrodeposition, and were examined by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). <br /><br /> Immobilization strategies for biomolecules are of paramount importance for successful fabrication of biosensors. This thesis reports a new immobilization method that is based on patterned deposition of alkyl thiosulfates (Bunte salts). Monolayers were formed through electrochemical oxidation of Bunte salts at Au-modified electrodes. Single-component and mixed monolayers were investigated, where the mixed monolayers involved one component with a terminal carboxylic acid functional group to allow immobilization of biomolecules. <br /><br /> Applications of the newly developed immobilization method to an enzyme-based biosensor and an immunosensor were investigated. Glucose and biotin were chosen as model analytes, respectively. Glucose oxidase (GOx) and avidin were covalently immobilized onto the mixed-monolayer-modified electrodes through the carboxylic acid groups. Under the optimized conditions for the fabrication and operation of the biosensors, the new electrochemical array showed linearity up to 10 mM glucose with a sensitivity of 4. 7 nA mM^-1 and a detection limit of 0. 8 mM (S/N=3), and linearity up to 12. 8 µM biotin with a detection limit of 0. 08 µM (S/N=3).

Pothole wetlands are ubiquitous throughout the Prairie Pothole Region and since 1900, 40-70% of potholes in the region have been drained to increase agricultural production. This thesis describes factors influencing spatial and temporal variations in wetland water quality and characteristics of drainage water. Research was conducted at Smith Creek watershed, southeastern Saskatchewan, where there has been controversy over recent renewed efforts to drain wetlands. Following snowmelt in 2009, 67 wetlands were sampled to determine whether spatial variations in wetland water quality were attributable to land cover, permanence classes, and surface drainage characteristics. Wetlands with cropped uplands had greater TP and K than wetlands with wooded and grassed uplands; TP, TDN, and DOC were higher in seasonally than permanently ponded wetlands; and salts were lower in wetlands with wooded uplands compared to wetlands with cropped and grassed uplands. Measurements of water quality of one permanently ponded wetland over a 20 week period in 2008 showed that the wetland acted as a solute trap. Variations in salts and DOC were influenced by hydrological processes such as runoff, evaporation, and shallow groundwater seepage, whereas variations in nitrogen, phosphorus, and bacteria were influenced by biotic, sorption, and hydrological processes. The experimental drainage of this wetland in November 2009 demonstrated that its water quality was an important control of drainage water quality. Further, the wetland ditch acted as a simple conduit, i.e., little solutes loss or gain occurred along it. In spring 2009, water quality along seven ditches and five natural connections that form between wetlands (termed spills) was compared. Concentrations of most solutes were similar, except TDN, DOC, HCO₃^-, K⁺, and Ca²⁺ that were higher in ditches than spills. Minimal changes in water quality along ditches and spills occurred, likely due to the low temperatures occurring in spring that restrict biotic processing and sorption. Notably, because ditches connect wetlands to streams, as opposed to spills that connect adjacent wetlands, ditches have a greater potential to contribute to downstream solute loading. Wetland drainage efficiency and wetland water quality were deemed the factors critical to determining solute exports via ditches. Results of wetland water quality and drainage characteristics can be useful to future modeling exercises and could be used to inform wetland drainage practices and policies.

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Thesis (Ph. D.)--Institute of Paper Chemistry, 1959. / Includes bibliographical references (p. 100-102).