Browsing by Subject "Groundwater -- Pollution"
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Item A finite difference model for flow of a pollutant through unsaturated porus [i.e. porous] media(Texas Tech University, 1987-05) Acharya, Binayak PrasadThe purpose of this study was to develop a two dimensional finite difference model to estimate the solute concentration at different depths in various types of soils. The results obtained with the model will be used to determine the potential of possible groundwater contamination due to the flow of pollutants through unsaturated porous media. Three different soils were studied. Inputs into the model were soil physical properties, grid sizes of the domain, and a specified time increment. The soil physical properties include the relationships between moisture content, pressure, hydraulic conductivity, soil porosity, and soil field capacity. Solute concentrations were estimated at different depths within a domain of 10 feet by 10 feet using a grid size of one foot in both the horizontal (X) and vertical (Z) directions. During the testing of this model for Amarillo silt clay soil and Poudar river sand, the solute was shown to reach a depth of two feet from the soil surface within a time period of 45 days after a one day application period. The computation showed movement of moisture as well as solute through a depth of soil and in X direction for continuous application condition. For the fine sand soil the flow was much faster compared to the other two test soils. Solute moved to a depth of seven feet and horizontally for a distance of three feet along the X direction within a time period of 60 minutes. The estimates which were developed with the model showed that the flow of solute through unsaturated soil were dependent on the initial soil moisture content. A variation in solute concentrations at different depths of the soil with the initial moisture content was established. The computed results for the fine sand soil showed a little deviation from the type of results expected. Hence necessary modifications are suggested for better accuracy and flexibility of the model. It is also suggested to test the model for more different types of soil. Then the model can be used to estimate the potential threat to groundwater Zpollution for different areas.Item Chemical in-situ oxidation for rehabilitation of aquifers(Texas Tech University, 1988-12) Smith, Ronnie DaleNot availableItem Experimental and theoretical study of volatilization for hydrocarbon removal in unsaturated porous media(Texas Tech University, 1989-05) Zaman, Mohammad RoknuzNot availableItem Increasing in situ biodegradation of diesel fuel by cyclic water table movement: a laboratory investigation(Texas Tech University, 1990-05) Mayfield, Mary PauletteNot availableItem Nitrogen mass balance determination for simulated wastewater land-spreading operations(Texas Tech University, 1974-12) Chapman, StantonNot availableItem Using high performance computing and visualization to enhance risk assessment methodology: case study with perchlorate(Texas Tech University, 2004-05) Albers, Eric PeterSite-specific risk assessments commonly result in large amounts of information that needs to be processed for a wide, often non-scientific, audience consisting of risk managers, regulators, and other decision makers. For this work we combined a series of models into a large virtual representation of the study system. By using a location-based approach, we were able to arrive at a more accurate determination of risk compared to just a maximum-dose approach. Caddo Lake at Longhom Army Ammunition Plant was used to study the impacts of perchlorate (C104') on thyroid hormone secretion in the channel catfish (Ictalurus punctatus). Two hypothetical contaminant plumes were modeled accounting for groundwater upwelling into the lake and effluent discharge near the surface. Results were compared between environmental systems and the three dosing techniques; maximum dose, time-lapsed maximum dose, and location-based dose. Perchlorate tissue concentrations for liver, kidney, gill, skin, muscle, GI tract, and thyroid, as well as thyroid hormone levels and secretion rates were simulated. We have shown that a standard maximum dose approach vastly overestimates exposure for individuals and populations. By simulating large numbers of individuals we are able to achieve low probability extreme events, thereby limiting the need for uncertainty factors. Through the use of commercially available graphics software Maya®, we were able to generate 3- dimensional visualizations of our study site, PBTK model, thyroid hormone secretion, catfish movement, and contaminant plumes, further aiding in data comprehension. This is the first study to generate a 3-dimensional PBTK with commercially available software, as well as use grid computing and 3-d visualization for risk assessment.