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An Assessment of the Use of Seeding, Mowing, and Burning in the Restoration of an Oldfield to Tallgrass Prairie in Lewisville, Texas

Description: An examination of the effectiveness of seeding, burning, and mowing in the reestablishment of tallgrass prairie species on overgrazed and abandoned pastureland. The study site is a 20 acre tract on U.S. Corps of Engineers land below Lake Lewisville in Denton County, Texas. The site was partitioned into thirty-nine 40 by 40 meter plots with seeding (carried out in 1996) and management treatment (burning, mowing, and no maintenance carried out in 1998) randomly applied following a two level design. For each plot, nine stratified-random 0.1 m2 subplots were examined and shoot counts for each species recorded. The effects of the treatments on individual species and species richness were analyzed with a two-way ANOVA followed by a SNK multiple range test, both on ranked data. Community level analysis was conducted with both a MANOVA on ranked data and a Canonical Correspondence Analysis on raw data. Results indicate that seeding positively affected species richness, particularly when combined with either burning or mowing in the early spring. Mowing also significantly increased species richness in areas that were not seeded, while burning negatively affected species richness on unseeded plots. Treatments significantly affected community composition with treatments having the most clear effect on spring and summer forbs.
Date: August 1999
Creator: Windhager, Steven

Bioaccumulation of Triclocarban, Triclosan, and Methyl-triclosan in a North Texas Wastewater Treatment Plant Receiving Stream and Effects of Triclosan on Algal Lipid Synthesis.

Description: Triclosan (TCS) and triclocarban (TCC), widely used antimicrobial agents found in numerous consumer products, are incompletely removed by wastewater treatment plant (WWTP) processing. Methyl-triclosan (M-TCS) is a more lipophilic metabolite of its parent compound, TCS. The focus of this study was to quantify bioaccumulation factors (BAFs) for TCS, M-TCS, and TCC in Pecan creek, the receiving stream for the City of Denton, Texas WWTP by using field samples mostly composed of the alga Cladophora sp. and the caged snail Helisoma trivolvis as test species. Additionally, TCS effects on E. coli and Arabidopsis have been shown to reduce fatty acid biosynthesis and total lipid content by inhibiting the trans-2 enoyl- ACP reductase. The lipid synthesis pathway effects of TCS on field samples of Cladophora spp. were also investigated in this study by using [2-14C]acetate radiolabeling procedures. Preliminary results indicate high TCS concentrations are toxic to lipid biosynthesis and reduce [2-14C]acetate incorporation into total lipids. These results have led to the concern that chronic exposure of algae in receiving streams to environmentally relevant TCS concentrations might affect their nutrient value. If consumer growth is limited, trophic cascade strength may be affected and serve to limit population growth and reproduction of herbivores in these riparian systems.
Date: August 2007
Creator: Coogan, Melinda Ann

Bioavailability and toxicity of 2,4,6-trinitrotoluene in sediment.

Description: TNT (2,4,6-trinitrotoluene) is a persistent contaminant at many military installations and poses a threat to aquatic ecosystems. Data from environmental fate and toxicity studies with TNT revealed that sediment toxicity test procedures required modification to accurately assess sediment TNT toxicity. Key modifications included aging TNT-spiked sediments 8-14 d, basing lethal dose on measured sediment concentrations of the molar sum of TNT and its main nitroaromatic (NA) transformation products (SNA), basing sublethal dose on average sediment SNA concentrations obtained from integration of sediment SNA transformation models, avoiding overlying water exchanges, and minimizing toxicity test durations. Solid phase microextraction fibers (SPMEs) were investigated as a biomimetic chemical measure of toxicity and bioavailability. Both organism and SPME concentrations provided measures of lethal dose independent of exposure scenario (TNT-spiked sediment or TNT-spiked water) for Tubifex tubifex. Among all benthic organisms tested (Chironomus tentans, Ceriodaphnia dubia, T. tubifex) and matrixes, median lethal dose (LC50) estimates based on SPME and organism concentrations ranged from 12.6 to 55.3 mmol SNA/ml polyacrylate and 83.4 to 172.3 nmol SNA/g tissue, ww, respectively. For Tubifex, LC50s (95% CI) based on SNA concentrations in sediment and SPMEs were 223 (209-238) nmol SNA/g, dw and 27.8 (26.0-29.8) mmol SNA/ml, respectively. Reproductive effects occurred at slightly lower exposures. Median effective dose (EC50) estimates (95% CI) for Tubifex cocoon production, based on sediment and SPME concentrations, were 118 (114-122) nmol SNA/g, dw and 21.8 (21.2-22.4) mmol SNA/ml, respectively. Bioconcentration experiments with Tubifex revealed that compound hydrophobicity predicted the toxicokinetics and bioconcentration of these compounds from water, however, there was a large discrepancy between the toxicokinetics of absorbed versus metabolically-generated aminodinitrotoluenes. A large portion of bioconcentrated, radiolabeled TNT transformation products could not be identified. In addition to their ability to provide matrix-independent measures of dose, SPME concentrations were more accurate indicators of bioavailable NAs than ...
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Date: May 2004
Creator: Conder, Jason M.

Characterization of Triclocarban, Methyl- Triclosan, and Triclosan in Water, Sediment, and Corbicula Fluminea (Müller, 1774) Using Laboratory, in Situ, and Field Assessments

Description: In the last decade emerging contaminants research has intensified in a bid to answer questions about fate, transport, and effects as these chemicals as they get released into the environment. The chemicals of interest were the antimicrobials; triclocarban (TCC) and triclosan (TCS), and a metabolite of triclosan, methyl triclosan (MTCS). This research was designed to answer the question: what is the fate of these chemicals once they are released from the waste water treatment plant into receiving streams. Three different assessment methods; field monitoring, in-situ experiments, and laboratory studies were used to answer the overall question. TCS, TCC, and MTCS levels were measured in surface water, sediment and the Asiatic clam Corbicula fluminea. Field studies were conducted using four sites at Pecan Creek, Denton TX. Levels of all three chemicals in clams were up to fives orders of magnitude the water concentrations but an order of magnitude lower than in sediment. Highest sediment levels of chemicals were measured in samples from the mouth of Pecan Creek (highest organic matter). TCC was the most and TCS was the least accumulated chemicals. In-situ and lab studies both indicated that uptake of these chemicals into the clams was very rapid and measurable within 24hours of exposure. The after clams were transferred into clean water most of the compounds were depurated within 14 days.
Date: May 2011
Creator: Edziyie, Regina E.

Comparison of Bare Root vs. Potted Plants, Species Selection, and Caging Types for Restoration of a Prairie Wetland, and Quantitative Analysis and Descriptive Survey of Plant Communities and Associations at Lewisville Lake Environmental Learning Area (LLELA), Lewisville, TX

Description: Lewisville Lake Environmental Learning Area (LLELA) is an 809-hectare property in Denton County, TX. A study of the vegetation community identified 466 species in 104 families, with 25% of the species from only two families, Asteraceae and Poaceae. The property demonstrates the characteristics of an early successional community, dominated by weedy species. Prairie communities are dominated by Johnson grass and ragweed, with climax tall grass prairie communities only in areas that have been planted with native grass seed. Forest communities are similarly in an early successional stage, dominated by the hackberry-elm-ash alliance, with small remnants of native Cross Timbers found in isolated patches. Species richness and diversity were highest in the forests and lowest in the wetlands; evenness, though not different across ecosystems, demonstrated a strong seasonal component. The species list was compared with previously reported lists for Denton County, and 256 species identified had not been previously reported for the county. A wetland restoration study was conducted to determine if there was a difference in survival and growth between potted transplants with intact root systems and bare-root transplants. Two different mesh sizes were used for protection, and the success of the different caging was evaluated. Of eight species, only four survived through the second growing season. There was no significant difference in the success of the propagule types for Sagittaria latifolia. The treatments planted with intact root systems showed significantly higher growth and reproduction than the bare-root treatments for Eleocharis quadrangulata, Heteranthera dubia, and Vallisneria americana. There was no survival recorded in the coarse mesh cages, likely due to the presence of crayfish that are able to get through the coarser mesh and feed on the transplants.
Date: May 2007
Creator: Buckallew, Robin R.

A Comparison of Mercury Localization, Speciation, and Histology in Multiple Fish Species From Caddo Lake, a Fresh Water Wetland

Description: This work explores the metabolism of mercury in liver and spleen tissue of fish from a methylmercury contaminated wetland. Wild-caught bass, catfish, bowfin and gar were collected. Macrophage centers, which are both reactive and primary germinal centers in various fish tissues, were hypothesized to be the cause of demethylation of methylmercury in fish tissue. Macrophage centers are differentially expressed in fish tissue based on phylogenetic lineage, and are found primarily in the livers of preteleostean fish and in the spleen of teleostean fish. Histology of liver and spleen was examined in both control and wild-caught fish for pathology, size and number of macrophage centers, and for localization of mercury. Total mercury was estimated in the muscle tissue of all fish by direct mercury analysis. Selenium and mercury concentrations were examined in the livers of wild-caught fish by liquid introduction inductively coupled plasma mass spectrometry (ICP-MS). Total mercury was localized in histologic sections by laser ablation ICP-MS (LA-ICP-MS). Mercury speciation was determined for inorganic and methylmercury in liver and spleen of fish by bas chromatography-cold vapor atomic fluorescence spectroscopy (GC-CVAFS). Macrophage center tissue distribution was found to be consistent with the literature, with a predominance of centers in preteleostean liver and in spleens of teleostean fish. Little evidence histopathology was found in the livers or spleens of fish examined, but differences in morphology of macrophage centers and liver tissue across species are noted. the sole sign of liver pathology noted was increased hepatic hemosiderosis in fish with high proportions of liver inorganic mercury. Inorganic mercury was found to predominate in the livers of all fish but bass. Organic mercury was found to predominate in the spleens of all fish. Mercury was found to accumulate in macrophage centers, but concentrations of mercury in this compartment were found to vary less in relation ...
Date: May 2012
Creator: Smith, James Durward

Comparison of Risk Assessment-Predicted Ecologically Safe Concentrations of Azinphos-Methyl and Fenvalerate to Observed Effects on Estuarine Organisms in a South Carolina Tidal Stream Receiving Agricultural Runoff

Description: A prospective ecological risk assessment method was developed evaluating the cumulative probabilistic impact of chemical stressors to aquatic organisms. This method was developed in response to the need to evaluate the magnitude, duration and episodic nature of chemical stressors on aquatic communities under environmental exposure scenarios. The method generates a probabilistic expression of the percent of an ecosystem's species at risk from a designated chemical exposure scenario.
Date: August 1997
Creator: Morton, Michael Gerard, 1957-

A Data Fusion Framework for Floodplain Analysis using GIS and Remotely Sensed Data

Description: Throughout history floods have been part of the human experience. They are recurring phenomena that form a necessary and enduring feature of all river basin and lowland coastal systems. In an average year, they benefit millions of people who depend on them. In the more developed countries, major floods can be the largest cause of economic losses from natural disasters, and are also a major cause of disaster-related deaths in the less developed countries. Flood disaster mitigation research was conducted to determine how remotely sensed data can effectively be used to produce accurate flood plain maps (FPMs), and to identify/quantify the sources of error associated with such data. Differences were analyzed between flood maps produced by an automated remote sensing analysis tailored to the available satellite remote sensing datasets (rFPM), the 100-year flooded areas "predicted" by the Flood Insurance Rate Maps, and FPMs based on DEM and hydrological data (aFPM). Landuse/landcover was also examined to determine its influence on rFPM errors. These errors were identified and the results were integrated in a GIS to minimize landuse / landcover effects. Two substantial flood events were analyzed. These events were selected because of their similar characteristics (i.e., the existence of FIRM or Q3 data; flood data which included flood peaks, rating curves, and flood profiles; and DEM and remote sensing imagery.) Automatic feature extraction was determined to be an important component for successful flood analysis. A process network, in conjunction with domain specific information, was used to map raw remotely sensed data onto a representation that is more compatible with a GIS data model. From a practical point of view, rFPM provides a way to automatically match existing data models to the type of remote sensing data available for each event under investigation. Overall, results showed how remote sensing could contribute to ...
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Date: August 2000
Creator: Necsoiu, Dorel Marius

Developing a Forest Gap Model to Be Applied to a Watershed-scaled Landscape in the Cross Timbers Ecoregion Using a Topographic Wetness Index

Description: A method was developed for extending a fine-scaled forest gap model to a watershed-scaled landscape, using the Eastern Cross Timbers ecoregion as a case study for the method. A topographic wetness index calculated from digital elevation data was used as a measure of hydrologic across the modeled landscape, and the gap model modified to have with a topographically-based hydrologic input parameter. The model was parameterized by terrain type units that were defined using combinations of USDA soil series and classes of the topographic wetness index. A number of issues regarding the sources, grid resolutions, and processing methods of the digital elevation data are addressed in this application of the topographic wetness index. Three different grid sizes, 5, 10, and 29 meter, from both LiDAR-derived and contour-derived elevation grids were used, and the grids were processed using both single-directional flow algorithm and bi-directional flow algorithm. The result of these different grids were compared and analyzed in context of their application in defining terrain types for the forest gap model. Refinements were made in the timescale of gap model’s weather model, converting it into a daily weather generator, in order to incorporate the effects of the new topographic/hydrologic input parameter. The precipitation model was converted to use a Markov model to initiate a sequence of wet and dry days for each month, and then daily precipitation amounts were determined using a gamma distribution. The output of the new precipitation model was analyzed and compared with a 100-year history of daily weather records at daily, monthly, and annual timescales. Model assumptions and requirements for biological parameters were thoroughly investigated and questioned. Often these biological parameters are based on little more than assumptions and intuition. An effort to base as many of the model’s biological parameters on measured data was made, including a new ...
Date: August 2014
Creator: Goetz, Heinrich

Development of a Procedure to Evaluate Groundwater Quality and Potential Sources of Contamination in the East Texas Basin

Description: This study contributes a procedure, based on data analysis and geostatistical methods, to evaluate the distribution of chemical ratios and differentiate natural and anthropogenic contaminant sources of groundwater quality in the East Texas Basin. Four aquifers were studied, Sparta, Queen City, Carrizo and Wilcox. In this study, Carrizo- Wilcox is considered as one aquifer, and Sparta-Queen City as another. These aquifers were divided into depth categories, 0-150 feet for Sparta-Queen City and 300-600 feet and 600-900 feet for Carrizo-Wilcox in order to identify individual sources of contamination. Natural sources include aquifer mineral make up, salt domes and lignite beds. Major anthropogenic sources include lignite and salt dome mining and oil-gas production. Chemical ratios selected were Na/Cl, Ca/Cl, Mg/Cl, SO4/Cl, (Na+Cl)/TDS, SO4/Ca and (Ca+Mg)/(Na+K). Ratio distributions and their relationships were examined to evaluate physical-chemical processes occurring in the study area. Potential contaminant sources were used to divide the Basin into three areas: Area 1 to the east, Area 2 in the west and Area 3 in the center. Bivariate analysis was used to uncover differences between the areas. The waters in Area 1 are potentially impacted primarily from oil field waters. Sources present in Area 2 include lignite beds and oil field operations. Area 3 is the cap rock of salt domes that can contain gypsum and anhydrite. Based on the exploratory data analysis (Na+Cl)/TDS, (Ca+Mg)/(Na+K), and SO4/Ca ratios were chosen for geostatistical analysis. Chemical ratios that provided indications of cation exchange, salt domes and oil fields were (Na+Cl)/TDS, (Ca+Mg)/(Na+K) and SO4/Ca. In the Sparta-Queen City 150 zone the procedure did not provide a good method for differentiating between contaminant sources. However, the procedure was effective to indicate impacted ground water in the Carrizo-Wilcox 600 and 900 foot zones.
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Date: May 2001
Creator: Alderman, John H.

Development, Validation, and Evaluation of a Continuous, Real-time, Bivalve Biomonitoring System

Description: A biological monitoring tool to assess water quality using bivalve gape behavior was developed and demonstrated. The purpose of this work was to develop methodologies for screening water quality appropriate to the goals of the watershed paradigm. A model of bivalve gape behavior based on prediction of behavior using autoregressive techniques was the foundation of the bivalve biomonitoring system. Current technology was used in developing the system to provide bivalve gape state data in a continuous real-time manner. A laboratory version of the system, including data collection and analysis hardware and software, was developed for use as a toxicological assay for determination of effective concentrations of toxicant(s) or other types of stress on bivalve gape behavior. Corbicula fluminea was monitored and challenged with copper, zinc, and chlorpyrifos using the system. Effective concentrations of 176±23µg/L copper, 768±412µg/L zinc, and 68µg/L chlorpyrifos were observed using a natural water with high dissolved organic carbon concentrations. A rugged field version of the bivalve biomonitoring system was developed and deployed in two locations. The field systems were fitted with a photovoltaic array, a single board computer, and a CDPD telemetry modem for robust remote operation. Data were telemetered at a time relevant rate of once every ten minutes. One unit was deployed in Lake Lewisville, Denton County, TX in February 2000. Data were telemetered and archived at a 92% success rate. Bivalve gape data demonstrated significant behavioral deviations on average 5 times per month. A second unit was deployed in Pecan Creek, Denton, TX in June 2001. Data from this site were telemetered and archived at a 96% success rate. Over the months of June-August 2001, 16 significant behavioral deviations were observed, 63% of which were correlated with changes in physical/chemical parameters. This work demonstrated the relative sensitivity of bivalve gape as a toxicological endpoint ...
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Date: December 2002
Creator: Allen, H. Joel

Dynamics of Stream Fish Metacommunities in Response to Drought and Re-connectivity

Description: This dissertation investigates the spatio-temporal dynamics of intermittent stream fish metacommunities in response drought-induced fragmentation and re-connectivity using both field and experimental approaches. A detailed field study was conducted in two streams and included pre-drought, drought, and post-drought hydrological periods. Fish assemblages and metacommunity structure responded strongly to changes in hydrological conditions with dramatic declines in species richness and abundance during prolonged drought. Return of stream flows resulted in a trend toward recovery but ultimately assemblages failed to fully recover. Differential mortality, dispersal, recruitment among species indicates species specific responses to hydrologic fragmentation, connectivity, and habitat refugia. Two manipulative experiments tested the effects of drought conditions on realistic fish assemblages. Fishes responded strongly to drought conditions in which deeper pools acted as refugia, harboring greater numbers of fish. Variability in assemblage structure and movement patterns among stream pools indicated species specific habitat preferences in response predation, resource competition, and desiccation. Connecting stream flows mediated the impacts of drought conditions and metacommunity dynamics in both experiments. Results from field and experimental studies indicate that stream fish metacommunities are influenced by changes in hydrological conditions and that the timing, duration, and magnitude of drought-induced fragmentation and reconnecting stream flows have important consequences metacommunity dynamics.
Date: August 2015
Creator: Driver, Lucas J.

Effect of Rancher’s Management Philosophy, Grazing Practices, and Personal Characteristics on Sustainability Indices for North Central Texas Rangeland

Description: To assess sustainability of privately owned rangeland, a questionnaire was used to gathered data from ranches in Cooke, Montague, Clay, Wise, Parker, and Jack counties in North Central Texas. Information evaluated included: management philosophy, economics, grazing practices, environmental condition, quality of life, and demographics. Sustainability indices were created based on economic and land health indicator variables meeting a minimum Cronbach‘s alpha coefficient (α = 0.7). Hierarchical regression analysis was used to create models explaining variance in respondents’ indices scores. Five predictors explained 36% of the variance in rangeland economic sustainability index when respondents: 1) recognized management inaction has opportunity costs affecting economic viability; 2) considered forbs a valuable source of forage for wildlife or livestock; 3) believed governmental assistance with brush control was beneficial; 4) were not absentee landowners and did not live in an urban area in Texas, and; 5) valued profit, productivity, tax issues, family issues, neighbor issues or weather issues above that of land health. Additionally, a model identified 5 predictors which explained 30% of the variance for respondents with index scores aligning with greater land health sustainability. Predictors indicated: 1) fencing cost was not an obstacle for increasing livestock distribution; 2) land rest was a component of grazing plans; 3) the Natural Resource Conservation Service was used for management information; 4) fewer acres were covered by dense brush or woodlands, and; 5) management decisions were not influenced by friends. Finally, attempts to create an index and regression analysis explaining social sustainability was abandoned, due to the likely-hood of type one errors. These findings provide a new line of evidence in assessing rangeland sustainability, supporting scientific literature concerning rangeland sustainability based on ranch level indicators. Compared to measuring parameters on small plots, the use of indices allows for studying replicated whole- ranch units using rancher insight. Use ...
Date: December 2011
Creator: Becker, Wayne

Effects on Survival, Reproduction and Growth of Ceriodaphnia dubia following Single Episodic Exposure to Copper or Cadmium

Description: Effects of episodic exposures have gained attention as the regulatory focus of the Clean Water Act has shifted away from continuous-flow effluents. Standardized laboratory toxicity tests require that exposure be held constant. However, this approach may not accurately predict organism responses in the field following episodic exposures such as those associated with rain-driven runoff events or accidental pollutant discharge. Using a modified version of the 7-day short-term chronic test recommended by the US Environmental Protection Agency, Ceriodaphnia dubia were exposed to copper or cadmium for durations ranging from 1 minute to 24 hours. In addition, adult reproductive recovery and effects on second generation individuals was assessed following select copper exposures. Finally, cadmium exposures were compared in reconstituted hard water (RHW) and municipal treated wastewater effluent (TWE). Following exposure, organisms were transferred to clean RHW or TWE and maintained for the remainder of the test. No- and lowest observed effect concentrations (NO- and LOECs) increased logarithmically with respect to logarithmic decreases in duration regardless of metal, endpoint or water type. Effective concentrations of cadmium however, were usually higher than those of copper, especially in TWE. LOECs for C. dubia survival following 24-hour and 5-minute exposures to copper were 116 and 417 µg/L, respectively. LOECs for fecundity were 58 and 374 µg/L, respectively. Neonate production of first generation adult C. dubia appeared to recover from pulsed copper exposure upon examination of individual broods. Cumulative mean neonate production however, showed almost no signs of recovery at exposure durations ≥3 hours. Pulse exposure to copper also resulted in diminished fecundity of unexposed second generation individuals. Such effects were pronounced following parental exposure for 24 hours but lacking after parental exposures ≤3 hours. LOECs for C. dubia survival following 24-hour and 5-minute exposures to cadmium in RHW were 44 and 9000 µg/L, respectively. LOECs for ...
Date: August 2005
Creator: Turner, Philip K.

Evaluation of the Developmental Effects and Bioaccumulation Potential of Triclosan and Triclocarban Using the South African Clawed Frog, Xenopus Laevis

Description: Triclosan (TCS) and triclocarban (TCC) are antimicrobials found in U.S. surface waters. This dissertation assessed the effects of TCS and TCC on early development and investigated their potential to bioaccumulate using Xenopus laevis as a model. The effects of TCS on metamorphosis were also investigated. For 0-week tadpoles, LC50 values for TCS and TCC were 0.87 mg/L and 4.22 mg/L, respectively, and both compounds caused a significant stunting of growth. For 4-week tadpoles, the LC50 values for TCS and TCC were 0.22 mg/L and 0.066 mg/L; and for 8-week tadpoles, the LC50 values were 0.46 mg/L and 0.13 mg/L. Both compounds accumulated in Xenopus. For TCS, wet weight bioaccumulation factors (BAFs) for 0-, 4- and 8-week old tadpoles were 23.6x, 1350x and 143x, respectively. Lipid weight BAFs were 83.5x, 19792x and 8548x. For TCC, wet weight BAFs for 0-, 4- and 8-week old tadpoles were 23.4x, 1156x and 1310x. Lipid weight BAFs were 101x, 8639x and 20942x. For the time-to-metamorphosis study, TCS showed an increase in weight and snout-vent length in all treatments. Exposed tadpoles metamorphosed approximately 10 days sooner than control tadpoles. For the hind limb study, although there was no difference in weight, snout-vent length, or hind limb length, the highest treatment was more developed compared to the control. There were no differences in tail resorption rates between the treatments and controls. At relevant concentrations, neither TCS nor TCC were lethal to Xenopus prior to metamorphosis. Exposure to relatively high doses of both compounds resulted in stunted growth, which would most likely not be evident at lower concentrations. TCS and TCC accumulated in Xenopus, indicating that the compound has the potential to bioaccumulate through trophic levels. Although TCS may increase the rate of metamorphosis in terms of developmental stage, it did not disrupt thyroid function and metamorphosis in ...
Date: December 2010
Creator: King, Marie Kumsher

Evaluation of the Economic, Social, and Biological Feasibility of Bioconverting Food Wastes with the Black Soldier Fly (Hermetia illucens)

Description: Food waste in the waste stream is becoming an important aspect of integrated waste management systems. Current efforts are composting and animal feeding. However, these food waste disposal practices rely on slow thermodynamic processes of composting or finding farmers with domestic animals capable of consuming the food wastes. Bioconversion, a potential alternative, is a waste management practice that converts food waste to insect larval biomass and organic residue. This project uses a native and common non-pest insect in Texas, the black soldier fly, which processes large quantities of food wastes, as well as animal wastes and sewage in its larval stage. The goal of this research is to facilitate the identification and development of the practical parameters of bioconversion methods at a large cafeteria. Three major factors were selected to evaluate the practicality of a bioconversion system: (1) the biological constraints on the species; (2) the economic costs and benefits for the local community; (3) the perception of and interaction between the public and management agencies with respect to the bioconversion process. Results indicate that bioconversion is feasible on all levels. Larvae tolerate and consume food waste as well as used cooking grease, reducing the overall waste volume by 30-70% in a series of experiments, with an average reduction of 50%. The economical benefits are reduced collection costs and profit from the sale of pupae as a feedstuff, which could amount to as much as $1,200 per month under optimal conditions. Social acceptance is possible, but requires education of the public, specifically targeting school children. Potential impediments to social acceptance include historical attitudes and ignorance, which could be overcome through effective educational efforts.
Date: August 2004
Creator: Barry, Tami

Habitat Fragmentation by Land-Use Change: One-Horned Rhinoceros in Nepal and Red-Cockaded Woodpecker in Texas

Description: This research focuses on the spatial analysis of the habitat of two vulnerable species, the one-horn rhinoceros in the grasslands of southern Nepal, and the red-cockaded woodpecker in the Piney woods of southeast Texas, in the USA. A study sites relevant for biodiversity conservation was selected in each country: Chitwan National Park in Nepal, and areas near the Big Thicket National Preserve in Texas. Land-use differs in the two study areas: the first is still undergoing agrarian development while the second is in a technological phase and undergoing urbanization processes. Satellite remote sensing images were used to derive land-cover maps by supervised classification. These maps were then processed by Geographic Information Systems methods to apply habitat models based on basic resources (food and cover) and obtain habitat suitability maps. Several landscape metrics were computed to quantify the habitat characteristics especially the composition and configuration of suitable habitat patches. Sensitivity analyses were performed as the nominal values of some of the model parameters were arbitrary. Development potential probability models were used to hypothesize changes in land-use of the second study site. Various scenarios were employed to examine the impact of development on the habitat of red-cockaded woodpecker. The method derived in this study would prove beneficial to guide management and conservation of wildlife habitats.
Date: December 2010
Creator: Thapa, Vivek

The Influence of Disease Mapping Methods on Spatial Patterns and Neighborhood Characteristics for Health Risk

Description: This thesis addresses three interrelated challenges of disease mapping and contributes a new approach for improving visualization of disease burdens to enhance disease surveillance systems. First, it determines an appropriate threshold choice (smoothing parameter) for the adaptive kernel density estimation (KDE) in disease mapping. The results show that the appropriate threshold value depends on the characteristics of data, and bandwidth selector algorithms can be used to guide such decisions about mapping parameters. Similar approaches are recommended for map-makers who are faced with decisions about choosing threshold values for their own data. This can facilitate threshold selection. Second, the study evaluates the relative performance of the adaptive KDE and spatial empirical Bayes for disease mapping. The results reveal that while the estimated rates at the state level computed from both methods are identical, those at the zip code level are slightly different. These findings indicate that using either the adaptive KDE or spatial empirical Bayes method to map disease in urban areas may provide identical rate estimates, but caution is necessary when mapping diseases in non-urban (sparsely populated) areas. This study contributes insights on the relative performance in terms of accuracy of visual representation and associated limitations. Lastly, the study contributes a new approach for delimiting spatial units of disease risk using straightforward statistical and spatial methods and social determinants of health. The results show that the neighborhood risk map not only helps in geographically targeting where but also in tailoring interventions in those areas to those high risk populations. Moreover, when health data is limited, the neighborhood risk map alone is adequate for identifying where and which populations are at risk. These findings will benefit public health tasks of planning and targeting appropriate intervention even in areas with limited and poor-quality health data. This study not only fills the identified ...
Date: December 2017
Creator: Ruckthongsook, Warangkana

Influence of Sediment Exposure and Water Depth on Torpedograss Invasion of Lake Okeechobee, Florida

Description: Torpedograss (Panicum repens) was first observed in Lake Okeechobee in the 1970s and appears to have displaced an estimated 6,400 ha of native plants, such as spikerush (Eleocharis cellulosa), where inundation depths are often less than 50 cm. Two series of studies evaluated substrate exposure and water depth influences on torpedograss establishment and competitiveness. Results revealed that fragments remain buoyant for extended periods and so facilitate dispersal. Once anchored to exposed substrate fragments can readily root and establish. Subsequently, torpedograss thrives when subjected to inundations to 75 cm and survives prolonged exposure to depths greater than 1 m. These findings suggest that fluctuating water levels contribute to torpedograss dispersal and colonization patterns and that low water levels increase marsh area susceptible to invasion. The competition study found that spikerush grown in monoculture produces significantly more biomass when continually inundated to shallow depths (10 to 20 cm) than when subjected to drier conditions (-25 cm) or greater inundations (80 cm). In contrast, torpedograss establishes more readily on exposed substrate (-25 to 0 cm) compared to inundate substrates. During the first growing season biomass production increases as substrate exposure interval increases. However, during the second year, established torpedograss produces more biomass when grown on intermittently wet (0 cm) compared to permanently dry (-25 cm) or intermittently inundated (10 cm) substrates. No difference in production was observed between substrates permanently inundated (10 cm) and any other regime tested. During the first two years of torpedograss invasion, regardless of treatment, spikerush suppresses invasion and torpedograss had little effect on established spikerush, indicating that spikerush-dominated areas are capable of resisting torpedograss invasion. Even so, disturbances that might cause mortality of long hydroperiod species, such as spikerush, may create open gaps in the native vegetation and thus facilitate torpedograss establishment and expansion.
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Date: December 2006
Creator: Smith, Dian H.

The Influence of Urban Green Spaces on Declining Bumble Bees (Hymenoptera: Apidae)

Description: Bumble bees (Bombus spp.) are adept pollinators of countless cultivated and wild flowering plants, but many species have experienced declines in recent decades. Though urban sprawl has been implicated as a driving force of such losses, urban green spaces hold the potential to serve as habitat islands for bumble bees. As human populations continue to grow and metropolitan areas become larger, the survival of many bumble bee species will hinge on the identification and implementation of appropriate conservation measures at regional and finer scales. North Texas is home to some the fastest-growing urban areas in the country, including Denton County, as well as at least two declining bumble bee species (B. pensylvanicus and B. fraternus). Using a combination of field , molevular DNA and GIS methods I evaluated the persistence of historic bumble bee species in Denton County, and investigated the genetic structure and connectivity of the populations in these spaces. Field sampling resulted in the discovery of both B. pensylvanicus and B. fraternus in Denton County's urban green spaces. While the relative abundance of B. fraternus in these spaces was significantly lower than historic levels gleaned from museum recors, that of B. pensylvanicus was significantly higher. Statistical analyses found that both bare ground and tree cover surrounding sample sites were negatively associated with numbers of bumble bee individuals and hives detected in these green spaces. Additionally, limited genetic structuring of bumble bee populations was detected, leading to the conclusion that extensive gene flow is occurring across populations in Denton County.
Date: May 2016
Creator: Beckham, Jessica Lorene

Informing Conservation Management Using Genetic Approaches: Greater Sage-grouse and Galápagos Short-eared Owls as Case Studies

Description: Small isolated populations are of particular conservation interest due to their increased extinction risk. This dissertation investigates two small wild bird populations using genetic approaches to inform their conservation. Specifically, one case study investigated a Greater Sage-grouse (Centrocercus urophasianus) population located in northwest Wyoming near Jackson Hole and Grand Teton National Park. Microsatellite data showed that the Jackson sage-grouse population possessed significantly reduced levels of neutral genetic diversity and was isolated from other Wyoming populations. Analysis with single nucleotide polymorphisms (SNPs) and microsatellite data provided further evidence that the population's timing of isolation was relatively recent and most likely due to recent anthropogenic habitat changes. Conservation recommendations include maintaining or increasing the population's current size and reestablishing gene flow with the nearest large population. The second case study investigated the genetic distinctiveness of the Floreana island population of the Galápagos Short-eared Owl (Asio flammeus galapagoensis). Mitochondrial DNA sequence data did not detect differences across nine island populations, yet microsatellite and morphometric data indicated that limited gene flow existed with the population and surrounding island populations, which appeared asymmetric in direction from Floreana to Santa Cruz with no indication of gene flow into Floreana. These results have important conservation implications and recommend that the Floreana Short-eared Owl population be held in captivity during the rodenticide application planned for an ecosystem restoration project in 2018. The population is less likely to receive immigrants from surrounding island populations if negatively effected by feeding on poisoned rodents.
Date: May 2016
Creator: Schulwitz, Sarah E

Investigation of Lead Hydrolytic Polymerization and Interactions with Organic Ligands in the Soil/Sediment-Water Environment

Description: The objective of this research was to investigate lead speciation in the soil/sediment-water environment and to better understand how the species affect lead mobility under different environmental conditions. The research involved both field soil and sediment samples as well as standard lead solutions. Field samples were fully characterized and extracted by aqueous and organic solvents. The results were compared and evaluated with the metal speciation model, MINTEQA2. Hydrolytic polymerization and organic complexation studies were conducted with standard lead solutions under controlled experimental conditions. Results of the field samples showed that pH, dissolved cations, ionic strength, dissolved organic matter, and nature of the soil/sediment matrix play major roles in the distribution and mobility of lead (Pb) from contaminated sites. In the aqueous equilibration experiment, the magnitude of Pb2+ solubilization was in the order of pH4>pH7>pH9. The results were in good agreement with MINTEQA2 predictions. An important finding of the research is the detection of Pb polymerization species under controlled experimental conditions. At pH 5.22, Pb polymeric species were formed at rate of 0.03 per day. The role of Pb complexation with organic matter was evaluated in both field and standard samples. Different methodologies showed three types of organically bound Pb. A very small fraction of Pb, in the ppb range, was extractable from the contaminated soil by polar organic solvents. Sequential extractions show that 16.6±1.4 % of the Pb is organically complexed. Complexation of Pb with fulvic acid provided new information on the extent of Pb association with soluble organic matter. The overall results of this research have provided new and useful information regarding Pb speciation in environmental samples. The results, in several instances, have provided verification of MINTEQA2 model's prediction. They also revealed areas of disagreement between the models prediction and the experimental results. A positive note regarding the experimental ...
Date: December 2002
Creator: Sanmanee, Natdhera

Measuring Atmospheric Ozone and Nitrogen Dioxide Concentration by Differential Optical Absorption Spectroscopy

Description: The main objective was to develop a procedure based on differential optical absorption spectroscopy (DOAS) to measure atmospheric total column of ozone, using the automated instrument developed at the University of North Texas (UNT) by Nebgen in 2006. This project also explored the ability of this instrument to provide measurements of atmospheric total column nitrogen dioxide. The instrument is located on top of UNT’s Environmental Education, Science and Technology Building. It employs a low cost spectrometer coupled with fiber optics, which are aimed at the sun to collect solar radiation. Measurements taken throughout the day with this instrument exhibited a large variability. The DOAS procedure derives total column ozone from the analysis of daily DOAS Langley plots. This plot relates the measured differential column to the airmass factor. The use of such plots is conditioned by the time the concentration of ozone remains constant. Observations of ozone are typically conducted throughout the day. Observations of total column ozone were conducted for 5 months. Values were derived from both DOAS and Nebgen’s procedure and compared to satellite data. Although differences observed from both procedures to satellite data were similar, the variability found in measurements was reduced from 70 Dobson units, with Nebgen’s procedure, to 4 Dobson units, with the DOAS procedure.A methodology to measure atmospheric nitrogen dioxide using DOAS was also investigated. Although a similar approach to ozone measurements could be applied, it was found that such measurements were limited by the amount of solar radiation collected by the instrument. Observations of nitrogen dioxide are typically conducted near sunrise or sunset, when solar radiation experiences most of the atmospheric absorption.
Date: December 2011
Creator: Jerez, Carlos J.

Modeling of Land Use Change Effects on Storm Water Quantity and Quality in the City of Carrollton and the North Texas Area

Description: Development and population are rapidly increasing in urbanizing areas of North Texas and so is the need to understand changes in storm water runoff flow and its contamination by nutrients, sediment, pesticides and other toxicants. This study contributes to this understanding and has two primary components: first, development of a graphical user interface for a geographic information system and storm water management database, and second, performing a two-scale hydrological modeling approach (the US Corp of Engineers HEC-HMS model and the US Environmental Protection Agency SWMM model). Both primary components are used together as a toolkit to support the storm water management program of the City of Carrollton, located in North Texas. By focusing limited city resources, the toolkit helps storm water managers in the process of compliance with federal regulations, especially the National Pollution Discharge Elimination System permit, and provides guidance for reporting, planning and investigation. A planning example was conducted by modeling potential changes in storm water quality due to projections of land use based on the City of Carrollton's Comprehensive Plan. An additional component of this study is the evaluation of future changes in surface water quantity and quality in the North Central Texas area, specifically in a rural but rapidly urbanizing subbasin area of the greater Lake Lewisville watershed. This was accomplished using the US Corp of Engineers HEC-HMS hydrological model. Precipitation scenarios were derived from years of historically high, medium, and low annual precipitation. Development scenarios were derived from current land use in the Lake Lewisville sub basin, current land use in the city of Carrollton, and from Markov projections based on recent land use change calculated from satellite images of 1988 and 1999. This information is useful for future land use planning and management of water resources in North Texas.
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Date: December 2003
Creator: Duncan, Phillip Brent