This system will be undergoing maintenance Tuesday, December 6 from 9AM to 12PM CST.

  You limited your search to:

  Partner: UNT Libraries
 Degree Discipline: Environmental Science
 Degree Level: Doctoral
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

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

Date: August 1997
Creator: Morton, Michael Gerard, 1957-
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.
Contributing Partner: UNT Libraries
An Assessment of the Use of Seeding, Mowing, and Burning in the Restoration of an Oldfield to Tallgrass Prairie in Lewisville, Texas

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

Date: August 1999
Creator: Windhager, Steven
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 ...
Contributing Partner: UNT Libraries
Ecological Enhancement of Timber Growth: Applying Compost to Loblolly Pine Plantations

Ecological Enhancement of Timber Growth: Applying Compost to Loblolly Pine Plantations

Access: Use of this item is restricted to the UNT Community.
Date: December 1999
Creator: Stuckey, Harold Troy
Description: This study explored the application of compost onto a small loblolly pine tree forest in northeast Texas. Its purpose was to determine if the application of various amounts of compost would provide for accelerated rates of growth for the trees. Soil parameters were also monitored. A total of 270 trees were planted and studied in a northeast Texas forest ecosystem. Compost rates of 5, 25, and 50 tons per acre with either soil or compost backfill were utilized and compared to a control without compost. Nonparametric and parametric ANOVA and Chi-Square tests were utilized. The results indicated that greater application rates retained greater moisture and higher pH levels in the soil. Compost applications also yielded a greater survival rate as well as larger tree height and diameter when compared to the control. The 25 ton/acre application backfilled in native soil achieved the greatest average in height and diameter when compared to the averages for the control plot. Greater growth differences for the 25S application can be attributed to additional nutrients coupled with a stable pH consistent with native soil acidity.
Contributing Partner: UNT Libraries
A Data Fusion Framework for Floodplain Analysis using GIS and Remotely Sensed Data

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

Access: Use of this item is restricted to the UNT Community.
Date: August 2000
Creator: Necsoiu, Dorel Marius
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 ...
Contributing Partner: UNT Libraries
Assessment of the Efficacy of a Constructed Wetland to Reduce or Remove Wastewater Effluent Estrogenicity and Toxicity Using Biomarkers in Male Fathead Minnows (Pimephales Promelas Rafinesque, 1820)

Assessment of the Efficacy of a Constructed Wetland to Reduce or Remove Wastewater Effluent Estrogenicity and Toxicity Using Biomarkers in Male Fathead Minnows (Pimephales Promelas Rafinesque, 1820)

Date: December 2000
Creator: Hemming, Jon M.
Description: Vitellogenin in Pimephales promelas was used to assess estrogenicity of a local municipal effluent. Vitellogenin induction in male P. promelas increased in frequency and magnitude with increased exposure duration and was greater ("=0.05) than controls after 2 and 3 weeks of exposure. The level of vitellogenesis induced by effluent exposure was high compared to similar studies. A spring season evaluation followed. Biomarkers in P. promelas were used to assess the efficacy of a treatment wetland to remove toxicity and estrogenicity in final treated wastewater effluent. Comparisons were made with an effluent dominated stream and laboratory controls. Vitellogenin, GSIs (gonado-somatic indices), HSIs (hepato-somatic indices) and secondary sexual characteristics were biomarkers used in P. promelas models to assess aqueous estrogenicity. Biological indicators used to assess general fish health included hematocrit and condition factors. The estrogenic nature of the effluent was screened, concurrent with fish exposure, with GC/MS analysis for target estrogenic compounds including: 17-b estradiol, estrone, ethynylestradiol, Bisphenol A, nonylphenolic compounds, phthalates, and DDT. Plasma vitellogenin measured in P. promelas was significantly elevated (p < 0.0001) at the inflow site of the wetland and stream sites. GSIs for these exposures were less (a=0.001) at the wetland inflow site. At wetland sites closest ...
Contributing Partner: UNT Libraries
Thresholds in avian communities at multiple scales: Relationships between birds, forests, habitats, and landscapes in the Ray Roberts greenbelt, Denton

Thresholds in avian communities at multiple scales: Relationships between birds, forests, habitats, and landscapes in the Ray Roberts greenbelt, Denton

Date: December 2000
Creator: Barry, Dwight
Description: Environmental management agencies make efforts to reduce pollution loading in streams and rivers by promoting vegetated buffer zones between human activity and water. Most of these efforts do not mesh water quality-based buffer zone width requirements with conservation and wildlife values, specifically, the use of these riparian forest corridors for wildlife dispersal between habitats in highly fragmented landscapes. Forest interior birds are of the most concern to management in riparian forests due to their population declines across much of their breeding range. This dissertation investigates the role that landscape-level and habitat-level factors play on the presence of breeding birds in riparian forests, particularly the landscape and habitat factors that are influenced by human-caused fragmentation. This study describes research at the Ray Roberts Greenbelt, Denton, Texas, that explores the relationships between the landscape and forest habitats of the Greenbelt with its breeding bird community. The major findings of this study are that bird communities in the corridor forests are associated with a greater array of factors than are bird communities in patches, suggesting that the birds of patch forests are somewhat insulated from landscape-scale effects. Also, habitat values can be maintained in corridors, but there does not seem to be a ...
Contributing Partner: UNT Libraries
Development of a Procedure to Evaluate Groundwater Quality and Potential Sources of Contamination in the East Texas Basin

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

Access: Use of this item is restricted to the UNT Community.
Date: May 2001
Creator: Alderman, John H.
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 ...
Contributing Partner: UNT Libraries
Riparian Forest Width and the Avian Community in a Greenbelt Corridor Setting

Riparian Forest Width and the Avian Community in a Greenbelt Corridor Setting

Access: Use of this item is restricted to the UNT Community.
Date: May 2001
Creator: Hoffman, Karl W.
Description: The forest avian community of the Ray Roberts Greenbelt (Denton Co., Texas) was characterized for two years using point count station sampling, from fall 1998 to summer 2000. Richness data for both breeding seasons were correlated with two-spatial metrics: width of the riparian forest and distance to the nearest edge. There were significant correlations between forest interior species richness and both spatial metrics, for both breeding seasons. Based on these data, a minimum riparian forest width threshold of 400-meters is suggested to provide habitat for forest interior species, which have lost considerable habitat through forest fragmentation. Partners in Flight breeding bird priority concern scores were used to create a habitat priority index for the Trinity River bottomland hardwood forest system
Contributing Partner: UNT Libraries
Phosphorus Retention and Fractionation in Masonry Sand and Light Weight Expanded Shale Used as Substrate in a Subsurface Flow Wetland

Phosphorus Retention and Fractionation in Masonry Sand and Light Weight Expanded Shale Used as Substrate in a Subsurface Flow Wetland

Access: Use of this item is restricted to the UNT Community.
Date: August 2002
Creator: Forbes, Margaret G.
Description: Constructed wetlands are considered an inefficient technology for long-term phosphorus (P) removal. The P retention effectiveness of subsurface wetlands can be improved by using appropriate substrates. The objectives of this study were to: (i) use sorption isotherms to estimate the P sorption capacity of the two materials, masonry sand and light weight expanded shale; (ii) describe dissolved P removal in small (2.7 m3) subsurface flow wetlands; (iii) quantify the forms of P retained by the substrates in the pilot cells; and (iv) use resulting data to assess the technical and economic feasibility of the most promising system to remove P. The P sorption capacity of masonry sand and expanded shale, as determined with Langmuir isotherms, was 60 mg/kg and 971 mg/kg respectively. In the pilot cells receiving secondarily treated wastewater, cells containing expanded shale retained a greater proportion of the incoming P (50.8 percent) than cells containing masonry sand (14.5 percent). After a year of operation, samples were analyzed for total P (TP) and total inorganic P (TIP). Subsamples were fractionated into labile-P, Fe+Al-bound P, humic-P, Ca+Mg-bound P, and residual-P. Means and standard deviations of TP retained by the expanded shale and masonry sand were 349 + 169 and 11.9 ...
Contributing Partner: UNT Libraries
Use of geographic information systems for assessing ground water pollution potential by pesticides in central Thailand

Use of geographic information systems for assessing ground water pollution potential by pesticides in central Thailand

Date: August 2002
Creator: Thapinta, Anat
Description: This study employed geographic information systems (GIS) technology to evaluate the vulnerability of groundwater to pesticide pollution. The study area included three provinces (namely, Kanchana Buri, Ratcha Buri, and Suphan Buri) located in the western part of central Thailand. Factors used for this purpose were soil texture, percent slope, primary land use, well depth, and monthly variance of rainfall. These factors were reclassified to a common scale showing potential to cause groundwater contamination by pesticides. This scale ranged from 5 to 1 which means high to low pollution potential. Also, each factor was assigned a weight indicating its influence on the movement of pesticides to groundwater. Well depth, the most important factor in this study, had the highest weight of 0.60 while each of the remaining factors had an equal weight of 0.10. These factors were superimposed by a method called “arithmetic overlay” to yield a composite vulnerability map of the study area. Maps showing relative vulnerability of groundwater to contamination by pesticides were produced. Each of them represented the degree of susceptibility of groundwater to be polluted by the following pesticides: 2,4-D, atrazine, carbofuran, dicofol, endosulfan, dieldrin & aldrin, endrin, heptachlor & heptachlor epoxide, total BHC, and total DDT. ...
Contributing Partner: UNT Libraries
Water Quality Aspects of an Intermittent Stream and Backwaters in an Urban North Texas Watershed

Water Quality Aspects of an Intermittent Stream and Backwaters in an Urban North Texas Watershed

Date: August 2002
Creator: Taylor, Ritchie Don
Description: Pecan Creek flows southeast through the City of Denton, Texas. Characterized as an urban watershed, the basin covers approximately 63.5 km2. Pecan Creek is an intermittent stream that receives nonpoint runoff from urban landuses, and the City of Denton's wastewater treatment plant, Pecan Creek Water Reclamation Plant, discharges effluent to the stream. Downstream from the City of Denton and the wastewater treatment plant, Pecan Creek flows about 6,000 m through agricultural, pasture, and forested landscapes into Copas Cove of Lake Lewisville, creating backwater conditions. Pecan Creek water quality and chemistry were monitored from August 1997 to October 2001. Water quality was influenced by seasonal, spatial, climatic, and diurnal dynamics. Wastewater effluent discharged from the Pecan Creek Water Reclamation Plant had the greatest influence on water quality of the stream and backwaters. Water quality monitoring of Pecan Creek demonstrated that dissolved oxygen standards for the protection of aquatic life were being achieved. Water quality modeling of Pecan Creek was completed to assess future increases in effluent flow from the Pecan Creek Water Reclamation Plant. Water quality modeling indicated that dissolved oxygen standards would not be achieved at the future effluent flow of 21 MGD and at NPDES permitted loadings. Model results ...
Contributing Partner: UNT Libraries
Development, Validation, and Evaluation of a Continuous, Real-time, Bivalve Biomonitoring System

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

Access: Use of this item is restricted to the UNT Community.
Date: December 2002
Creator: Allen, H. Joel
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 ...
Contributing Partner: UNT Libraries
Ecotoxicological Investigations in Effluent-Dominated Stream Mesocosms

Ecotoxicological Investigations in Effluent-Dominated Stream Mesocosms

Date: December 2002
Creator: Brooks, Bryan W.
Description: The University of North Texas Stream Research Facility (UNTSRF) was designed to examine contaminant impacts on effluent-dominated stream ecosystems. Stream mesocosms, fed municipal effluent from the City of Denton, TX, Pecan Creek Water Reclamation Plant (PCWRP), were treated with 0, 15 or 140 µg/L cadmium for a 10-day study in August 2000. Laboratory toxicity test and stream macroinvertebrate responses indicated that cadmium bioavailability was reduced by constituents of effluent-dominated streams. The Biotic Ligand Model (BLM) for Cd was used to predict a 48 hour Cd EC50 for Ceriodaphnia dubia of 280 µg/L in these effluent-dominated streams. This value is higher that an EC50 of 38.3 µg/L Cd and a 7-day reproduction effect level of 3.3 µg/L Cd generated for C. dubia in reconstituted laboratory hard water. These results support use of a cadmium BLM for establishing site-specific acute water quality criteria in effluent-dominated streams. Although not affected by 15 µg/L treatments, organisms accumulated Cd in 15 µg/L treated streams. Hence, over longer exposure periods, Cd accumulation may increase and a no effect level may be lower than the observed 10-day no effect level of 15 µg/L. A toxicity identification evaluation procedure was utilized with in vitro and in vivo bioassays ...
Contributing Partner: UNT Libraries
Investigation of Lead Hydrolytic Polymerization and Interactions with Organic Ligands in the Soil/Sediment-Water Environment

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

Date: December 2002
Creator: Sanmanee, Natdhera
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 ...
Contributing Partner: UNT Libraries
Removal of selected water disinfection byproducts, and MTBE in batch and continuous flow systems using alternative sorbents.

Removal of selected water disinfection byproducts, and MTBE in batch and continuous flow systems using alternative sorbents.

Access: Use of this item is restricted to the UNT Community.
Date: December 2002
Creator: Kadry, Ahmed Y.
Description: A study was conducted to evaluate the sorption characteristics of six disinfection byproducts (DBPs) on four sorbents. To investigate sorption of volatile organic compounds (VOCs), specially designed experimental batch and continuous flow modules were developed. The investigated compounds included: chloroform, 1,2-dichloroethane (DCE), trichloroethylene (TCE), bromodichloromethane (BDCM), methyl tertiary butyl ether (MTBE), bromate and bromide ions. Sorbents used included light weight aggregate (LWA), an inorganic porous material with unique surface characteristics, Amberlite® XAD-16, a weakly basic anion exchange resin, Amberjet®, a strongly basic anion exchange resin, and granular activated carbon (GAC). Batch experiments were conducted on spiked Milli-Q® and lake water matrices. Results indicate considerable sorption of TCE (68.9%), slight sorption of bromate ions (19%) and no appreciable sorption for the other test compounds on LWA. The sorption of TCE increased to 75.3% in experiments utilizing smaller LWA particle size. LWA could be a viable medium for removal of TCE from contaminated surface or groundwater sites. Amberlite® was found unsuitable for use due to its physical characteristics, and its inability to efficiently remove any of the test compounds. Amberjet® showed an excellent ability to remove the inorganic anions (>99%), and BDCM (96.9%) from aqueous solutions but with considerable elevation of pH. ...
Contributing Partner: UNT Libraries
On-Road Remote Sensing of Motor Vehicle Emissions: Associations between Exhaust Pollutant Levels and Vehicle Parameters for Arizona, California, Colorado, Illinois, Texas, and Utah

On-Road Remote Sensing of Motor Vehicle Emissions: Associations between Exhaust Pollutant Levels and Vehicle Parameters for Arizona, California, Colorado, Illinois, Texas, and Utah

Access: Use of this item is restricted to the UNT Community.
Date: May 2003
Creator: Dohanich, Francis Albert
Description: On-road remote sensing has the ability to operate in real-time, and under real world conditions, making it an ideal candidate for detecting gross polluters on major freeways and thoroughfares. In this study, remote sensing was employed to detect carbon monoxide (CO), hydrocarbons (HC), and nitrogen oxide (NO). On-road remote sensing data taken from measurements performed in six states, (Arizona, California, Colorado, Illinois, Texas, and Utah) were cleaned and analyzed. Data mining and exploration were first undertaken in order to search for relationships among variables such as make, year, engine type, vehicle weight, and location. Descriptive statistics were obtained for the three pollutants of interest. The data were found to have non-normal distributions. Applied transformations were ineffective, and nonparametric tests were applied. Due to the extremely large sample size of the dataset (508,617 records), nonparametric tests resulted in "p" values that demonstrated "significance." The general linear model was selected due to its ability to handle data with non-normal distributions. The general linear model was run on each pollutant with output producing descriptive statistics, profile plots, between-subjects effects, and estimated marginal means. Due to insufficient data within certain cells, results were not obtained for gross vehicle weight and engine type. The "year" ...
Contributing Partner: UNT Libraries
Storm Water System Monitoring for the Small Municipality Under Phase II of the National Pollutant Discharge Elimination System

Storm Water System Monitoring for the Small Municipality Under Phase II of the National Pollutant Discharge Elimination System

Date: August 2003
Creator: Peacock, Steven
Description: Storm water quality can have a significant impact on receiving water bodies. The chief recipients of these impacts are aquatic life in the receiving water body and downstream water users. Over the last few decades, legislation, regulations, institutions and facilities have evolved to recognize the impact of urban storm water on receiving streams. This increased emphasis has caused contaminants in storm water to be identified as a major concern. This developing concern has generated an increased interest in the water quality of our streams and lakes and emphasized the need for more monitoring efforts. With the passage of the National Pollutant Discharge Elimination System (NPDES) Phase II requirements, small municipalities are responsible for storm water impacts on receiving waters within their jurisdiction. For the purposes of NPDES Phase II requirements, small municipalities are identified as these municipalities that are typically composed of 10,000 but less than 100,000 in population. The purpose of this dissertation is to develop a manual for use by the staff of small municipalities in meeting the requirements prescribed by changes initiated in the NPDES Phase II regulations. Attempts were made to comply with these requirements within a very limited manpower and budget framework and to develop ...
Contributing Partner: UNT Libraries
Modeling of Land Use Change Effects on Storm Water Quantity and Quality in the City of Carrollton and the North Texas Area

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

Access: Use of this item is restricted to the UNT Community.
Date: December 2003
Creator: Duncan, Phillip Brent
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 ...
Contributing Partner: UNT Libraries
Bioavailability and toxicity of 2,4,6-trinitrotoluene in sediment.

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

Access: Use of this item is restricted to the UNT Community.
Date: May 2004
Creator: Conder, Jason M.
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 ...
Contributing Partner: UNT Libraries
City of Denton Municipal Solid Waste Characterization and Management Strategies

City of Denton Municipal Solid Waste Characterization and Management Strategies

Access: Use of this item is restricted to the UNT Community.
Date: May 2004
Creator: Brady, Patricia D.
Description: Due to concern about diminishing landfill space, the City of Denton contracted a municipal solid waste characterization study in 1999 that would identify materials for diversion. This paper describes the results of 5 1-week waste sorting events, a scale-house analysis, a recycling participation study, a recycler profile and a similar city study. The results of the characterization studies suggest that at least 50% of each waste stream is recyclable or divertible though paper products accounted for no more than 45% by weight of any waste stream. Curbside recycling participation rate was 71% during the 6-week study period though the average weekly set-out rate was 37%. Recycling participation rates varied significantly by zip code and by home value categories but not by gender. Denton is fairly progressive in its waste management approach when compared to demographically similar cities on a 15-question assessment though recommendations for improvement have been identified.
Contributing Partner: UNT Libraries
Evaluation of the Economic, Social, and Biological Feasibility of Bioconverting Food Wastes with the Black Soldier Fly (Hermetia illucens)

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

Date: August 2004
Creator: Barry, Tami
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% ...
Contributing Partner: UNT Libraries
Revisiting Aldo Leopold's "Perfect" Land Health: Conservation and Development in Mexico's Rio Gavilan

Revisiting Aldo Leopold's "Perfect" Land Health: Conservation and Development in Mexico's Rio Gavilan

Date: December 2004
Creator: Forbes, William
Description: The Rio Gavilan watershed, located in Mexico 's northern Sierra Madre Occidental , has significance in conservation history. Upon visiting the remote, largely un­developed watershed during two hunting trips in the 1930s, renowned conservationist Aldo Leopold thought it was the best picture of land health he had seen. His main indicators of healthy land were slow water runoff rates regulating erosion and historical predator-prey relationships. The visits confirmed Leopold's concept of land health, inspired many of his essays, and helped shape his land ethic. Leopold proposed the area as a control site to research healthy land throughout North America . The proposal never went forward and the area has since been more intensively logged and grazed. This dissertation research used extensive literature review, archives, oral histories, citizen surveys, and rapid assessment of forest, rangeland, riparian, and socioeconomic health to assess impacts of past cultures and update the area's land health status. Projects that could restore land health, such as linked eco-tourism, forest density reduction, and rotational grazing, were assessed for feasibility. Recent critiques of Leopold's land ethic were also reviewed. Results indicate most pre-1940s impacts were light, current land health status is moderate, and local interest exists in restoring land ...
Contributing Partner: UNT Libraries
Effects on Survival, Reproduction and Growth of Ceriodaphnia dubia following Single Episodic Exposure to Copper or Cadmium

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

Date: August 2005
Creator: Turner, Philip K.
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 ...
Contributing Partner: UNT Libraries
A geospatial tool for assessing potential wildland fire risk in central Texas.

A geospatial tool for assessing potential wildland fire risk in central Texas.

Date: August 2005
Creator: Hunter, Bruce Allan
Description: Wildland fires in the United States are not always confined to wilderness areas. The growth of population centers and housing developments in wilderness areas has blurred the boundaries between rural and urban. This merger of human development and natural landscape is known in the wildland fire community as the wildland urban interface or WUI, and it is within this interface that many wildland fires increasingly occur. As wildland fire intrusions in the WUI increase so too does the need for tools to assess potential impact to valuable assets contained within the interface. This study presents a methodology that combines real-time weather data, a wildland fire behavior model, satellite remote sensing and geospatial data in a geographic information system to assess potential risk to human developments and natural resources within the Austin metropolitan area and surrounding ten counties of central, Texas. The methodology uses readily available digital databases and satellite images within Texas, in combination with an industry standard fire behavior model to assist emergency and natural resource managers assess potential impacts from wildland fire. Results of the study will promote prevention of WUI fire disasters, facilitate watershed and habitat protection, and help direct efforts in post wildland fire mitigation and ...
Contributing Partner: UNT Libraries
FIRST PREV 1 2 3 NEXT LAST