Thesis (Ph. D.)--University of Texas at El Paso, 2008. / Title from title screen. Vita. CD-ROM. Includes bibliographical references. Also available online.

Thesis (Ph. D.)--University of Texas at Austin, 1999. / Vita. Includes bibliographical references (leaves 362-371). Available also in a digital version from Dissertation Abstracts.

This project implemented novel approaches to assess the source, age, concentration and mobility of fecal indicator microorganisms within a karst groundwater system. Research was conducted in the well-characterized Blue Hole Spring karst groundwater basin in Versailles, Woodford County, Kentucky. At this site the AC/TC ratio and fecal coliform (FC) bacteria counts were used to delineate sources of fecal inputs and determine relative age of the fecal matter. An aging experiment using indicator bacteria (total coliform (TC) and atypical colonies (AC)), which approximated subsurface conditions, indicated that changes in the AC/TC ratio are likely to be retarded during bacterial transport through karst conduits. Decreases in the AC/TC ratio during the monitoring period appear to be the result of sewage releases. Multiple logistic regression (MLR) modeling was performed to examine correlations between physiochemical parameters and FC concentrations. MLR models using physiochemical parameters correctly predicted “safe for contact” (< 200 cfu/100 mL FC) conditions 65.6% of the time and “unsafe for contact” (> 200 cfu/100 mL FC) conditions 69.2% of the time at Blue Hole Spring. Modeling using other indicators (TC and AC) predicted “safe for contact” conditions 87.5% of the time and “unsafe for contact” conditions 61.5% of the time. A series of tracer tests were performed to compare transport of solute and abiotic particle tracers (rhodamine WT fluorescent dye, bromide and fluorescent bacteria-sized microspheres) and bacteria (15N-enriched wild-type E. coli) within the karst system. The surrogate tracers did not suitably mimic microbial mobility within the basin. Solutes and 15N-enriched E. coli arrived concurrently during storm flow to Blue Hole Spring, whereas microsphere breakthrough corresponded with maximum solute concentrations. The 15Nenriched E. coli exhibited slightly more tailing during storm-flow recession than solute tracers, none of which exhibited remobilization. Microspheres demonstrated remobilization within the conduits that correlated with later increases in discharge related to secondary storm events.

The purpose of this study was to determine if the chloride to bromide ratio (Cl/Br) of water imported via interbasin transfer can be used to trace the mixing of imported water with native ground water. Laboratory experiments and a chemical literature review indicate that chloride's and bromide's properties should make the Cl/Br a useful environmental ground-water tracer. This study has shown that the Cl/Br can be accurately quantified at environmental levels, is not attenuated by aquifer or soil media, is chemically stable, and is present in different levels in waters from different sources. Infiltration and mixing of irrigation water from the Colorado River (Cl/Br = 1300) with native ground water (Cl/Br = 630) was investigated at the Wellton-Mohawk Irrigation and Drainage District near Yuma, Arizona. The downgradient increase in the Cl/Br is correlated with distance from the upgradient limit of irrigation (r =.83), reflecting the chemical influence of infiltrating irrigation water.

Radon-222 gas has unique properties allowing it to be used as an indicator for the presence of organic phase liquids in the saturated zone. It naturally occurs in soils. It is radioactive, making quantitative detection straight forward. A noble gas, it is chemically inert and does not react with aquifer media. Finally, radon has an affinity to concentrate in nonaqueous phase liquids. A proposed linear equilibrium partitioning model was tested by batch equilibration with the pore fluid to establish the deficit in aqueous radon concentrations that results from its partitioning into the residual saturation of the organic phase (Soltrol-220). Five sets of experiments were run on columns with 0.0, 1.0, 2.5, 5.0, and 8.0 percent residual soltrol fractions. The model was found to accurately represent the partitioning process. A one-dimensional physical model was run to see if the data from the partitioning experiments could be successfully applied to predict the aqueous radon concentrations in a more complex situation. The results indicate that radon-222 has great potential to be used as a means of detecting and quantifying the presence of residual organic phase liquids in the saturated zone. / Graduation date: 1995

The assumption of perfect stratification in an aquifer has been widely used in solute-transport modeling studies. This assumption is especially useful for applied studies where limited site characterization data are available, but geologic well logs indicate significant layering. Chapter 3 investigates the issue of vertical sampling density via a sensitivity analysis of the number of aquifer layers used in a model of tracer transport through a heterogeneous synthetic aquifer. Tracer breakthrough in the synthetic aquifer is predicted by layered models. Given a variance of ln K of 2 and an exponential covariance function, sampling the synthetic aquifer at more than 12 elevations did not produce any significant improvement in the predictions. Even six sampling points, however, produced more accurate predictions of transport compared to a full-aquifer, homogeneous approach employing a local-scale dispersivity. Chapter 4 presents and interprets data from a dual-well, forced-gradient tracer experiment conducted in a confined aquifer underlying a contaminant source zone of a Superfund site. Tracer breakthrough was monitored at an extraction well and at four levels of a centerline monitoring well. A perfectly stratified numerical transport model based on multi-level data successfully predicted tracer breakthrough at the extraction well. Given the added vertical resolution associated with the layered model, it was possible to use dispersivity values more than an order of magnitude lower than the value used in a vertically integrated model. It is expected that the multi-layer model would allow for more robust analyses of solute transport at the site. In Chapter 5, TCE elution during the same dual-well experiment is predicted with a stratified numerical model incorporating rate-limited desorption, rate-limited diffusion, and rate-limited dissolution of nonaqueous phase liquid (NAPL). Based on model results, initial mass calculations, and other indirect lines of evidence, it is concluded that NAPL is the primary cause of rate limitations for TCE transport at the site. NAPL presence is the primary reason a large pump-and-treat system at the site has failed to reduce contaminant concentrations to federal drinking water standards. Alternative remediation technologies are thus necessary for restoring the aquifer, especially in the contaminant source zone.

The boron isotopic ratios of three contaminated ground water samples and of leachate from four fly ash samples are shown to be significantly different than the isotopic ratio of naturally occurring boron in a selected ground water. Analysis is performed using thermal ionization mass spectrometry with a precision of less than 1 per mil. Inductively coupled plasma mass spectrometry is shown to be ineffective for this application. Boron is isolated from solution and concentrated using Amberlite IRA-743 resin with no isotopic fractionation observed. Boron desorption from fly ash is shown to be rapid. Boron isotopic analysis is shown to be a superior method to boron concentration analysis for identifying leachate in a ground water, (1) at the outer limits of a leachate plume, and, (2) when the difference between the boron concentration of the leachate and background water is small. The degree of contamination can be determined if both end members are known.

A novel tracer method has used 15N to label Escherichia coli and track the transport of bacteria, a common contaminant, through karst aquifers. Use of this method could provide valuable insight into the movement of bacteria in aquifers, which would help improve remediation methods and strategies. A wild strain of E. coli was isolated from the Cane Run/Royal Spring basin in the Inner Bluegrass region of Kentucky. The strain was serotyped O-:H- and virulence testing showed the strain did not have virulence factors of E. coli commonly pathogenic to humans. Five karst microcosms were filled with sterilized water collected from Royal Spring in Georgetown, Kentucky. Each microcosm was inoculated with wild-type E. coli, enriched in 15N, and incubated at 14° C for 130 days. The microcosms were periodically sampled for the concentration and nitrogen isotope composition of E. coli over 130 days. The E. coli survived at concentrations within one log of the average initial value of 5.62×1010 for the duration of the study. Statistical modeling showed no significant difference in δ15N values from day 1 and day 130. This strain is therefore recommended for traces in the Cane Run/Royal Spring basin.

Thesis (Ph.D.) -- Flinders University, School of Chemistry, Physics and Earth Sciences. / Typescript (bound). Includes bibliographical references (leaves 265-281). Also available online.

Thesis (Ph.D.) -- University of Western Sydney, 2004. / Includes bibliography.