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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Building dynamic spatial environmental models

Karssenberg, Derek, January 2002 (has links)
Thesis (Ph. D.)--Utrecht University, 2002. / Title from title screen (viewed Mar. 22, 2004). Includes bibliographical references.
2

Risk assessment of viruses in water

Crabtree, Kristina Dawn, 1968- January 1996 (has links)
The human health significance of waterborne viruses has previously relied on epidemiological data from documented waterborne outbreaks. It is difficult, however, to assess the risks involved to individuals and communities from exposure to low levels of contamination. Risk assessment is a useful tool in the interpretation of water quality data and can be used to better understand the significance of exposure to low-level contamination of viruses in water. Microbial risk assessment was applied to determine the risks associated with environmental exposure to waterborne coxsackievirus and adenovirus. Annual risks of infection for drinking water were determined to be as high as 10⁻¹ for both coxsackievirus and adenovirus at exposure levels of 0.13 PFU/l and 0.001 IU/l, respectively. A comprehensive cost-of-illness analysis was conducted for three waterborne viruses--Norwalk virus, rotavirus, and non-polio enterovirus--to determine the economic impact of waterborne viruses in the United States. Annual medical costs and productivity losses were estimated in 1993 dollars using actual outbreak information and data from epidemiological studies. It was estimated that $1.1 to $6.9 billion is spent each year in the United States due to these viral illnesses, with potentially $0.39 to $2.4 billion attributable to water. The United States Environmental Protection Agency (USEPA) has initiated the Information Collection Rule (ICR) in which water utilities serving >100,000 people will be required to collect data on the concentrations of specific microorganisms in source and finished water beginning in 1997. Selected water utilities will be required to archive water samples for possible further viral analyses. A risk assessment approach was undertaken to determine which virus would be appropriate for the analyses of the archived water samples. The following viruses were selected based on the nature of the different diseases associated with each, their occurrence in waterborne outbreaks, and their resistance to inactivation by disinfectants: rotavirus, coxsackievirus, hepatitis A virus, adenovirus, Norwalk and Norwalk-like viruses, astrovirus, and hepatitis E virus. The polymerase chain reaction (PCR) is the recommended detection method. The results of these analyses will provide both a database on the occurrence of these viruses in water as well as their susceptibility to water treatment.
3

Analysis of Personal, Indoor, and Outdoor PM2.5 Monitored at Three Elementary Schools in Ohio

Liu, Bian 30 October 2002 (has links)
No description available.
4

Aquatic Study Field Trip: Benefits and Evaluation

Thompson, John William 09 1900 (has links)
<p>In this project an aquatic field trip resource is developed for both elementary and secondary teachers to use in their classes and at a pond site. It uses the compulsory activity from the grade 11 general level environmental science course as a model. Abiotic factors are measured and water organisms are surveyed so that the water quality can be determined.</p> <p>This study evaluates the effectiveness of a field trip to a pond in meeting the Ministry of Education science course objectives and looks at evaluation methods for the purpose of improving the learning experience for students. A report is given of water quality parameters as presented to the community of teachers who would possibly be using the site and a questionnaire given to survey their reactions and ideas about this report. To assist teachers further, a list of resources to help with this unit was developed from material gathered as the project took form.</p> <p>To put the unit and its teaching into a provincial focus and to gain practical ideas that would make teaching and preparing for the field trip more successful, a survey was done outlining the programs of similar centres nearby. Unfortunately, low data sets of students in the course could not reliably yield any scientific conclusions. The reactions of students to the activity, the historical background to this type of educational activity, and the positive effect of this additional tool in teachers' professional toolkits (Miles, 1990, ), shows this a worthwhile activity to undertake.</p> <p>The project did allow development of a detailed guide to aquatic organisms that can be used by teachers wanting some assistance teaching this unit. With changes by the current government, this particular course will not be offered again after the '98/99 school year. Courses at the elementary level will find this information helpful. Courses at the secondary level are currently being developed that should include units where this resource could be used.</p> / Master's of Science in Teaching (MST)
5

Diagenesis and transformation of aquatic dissolved organic matter in Nova Scotia freshwaters

Clair, Thomas A. January 1991 (has links)
<p>The acid-base and structural chemistry of freshwater dissolved organic matter (DOM) is known to vary with time and location. The purpose of this dissertation is to show how the chemical quality of DOM in temperate streams, wetlands and lakes of the Kejimkujik National Park area in central Nova Scotia varies over an annual cycle and how the changes in quality are related to DOM formation and diagenesis. New techniques were developed and used to better define the chemical quality DOM. A titration method described by Brassard et al. (1990) allowed the description of the acid-base characteristics of DOM. A reverse osmosis method is also described for the concentration of DOM without its fractionation to allow structural determination by ¹³C NMR of whole material. The results indicate that the chemical quality of DOM found in freshwaters is not similar to that found in soils. This difference suggests that interactions between soils, biology and hydrology modify the DOM in streams. A laboratory experiment suggests that the most likely pathway of DOM formation is the breakdown of plant structural material into aliphatic material with subsequent aromatic formation via semi-quinone and quinone. Comparison of incubation experiments with field results also shows that DOM acidity in natural water decreases with time caused by biological and chemical oxidative processes. Theoretical considerations indicate that the acidity of DOM does not follow the simple relationship suggested by Oliver et al. (1983) because of differences in source material and diagenetic processes, as well as the influence of inorganic cations and anions which until now have been assumed to be uncomplexed with organic matter.</p> / Doctor of Philosophy (PhD)
6

THE IMPACT OF INDUCED DROUGHT ON TRANSPIRATION AND GROWTH IN A TEMPERATE PINE PLANTATION FOREST

MacKay, Louise Samantha January 2010 (has links)
<p>A study evaluating the response of canopy transpiration (Ec) and growth rates to reduced water input, was conducted in a managed 70-year old planted temperate white pine (Pinus strobus L.) forest, in Southern Ontario, Canada from January to December 2009. In order to induce the drought, a 20m x 20m throughfall exclusion setup was established using interlocking aluminum troughs at a 3-inch slope. Throughfall was excluded from April 1st until July 3rd. During this period, 270mm of rainfall occurred (27% of annual precipitation) of which 90% was excluded. Sap flow velocity, soil moisture and soil temperature (at multiple depths) were measured continuously in both reference and drought plots. Dendrometer bands were also installed on all instrumented trees. Prior to enforced drought, adjacent plots showed slight variability in soil moisture while tree diameter and soil temperature did not show significant variability. Daily values of Ec from each plot ranged from 0 to 1.6 mm d-1 over the growing season (March-November) for the drought and reference plot respectively. The impact of the rainfall exclusion did not affect Ec until early June, 60 days after the drought was in place. Normalized values of Ec showed a 20% decrease from the drought trees compared to the reference. Cumulative growth rates between the two plots showed a net decrease in the drought trees of 42% from the reference and earlier termination of growth. However, the growing season Ec values were 174 mm y-l and 171 mm y-l for the drought and reference plot respectively. Currently, the effects of extreme drought<br />events on carbon and water balances in conifer forests are poorly understood, due<br />to their sporadic occurrence in natural ecosystems. The findings of this study help<br />to establish the impacts drought may have on these ecosystems and evaluate their<br />potential responses under predicted future climate regimes.</p> / Master of Science (MS)
7

Arsenic Speciation and Phytoremediation Modeling for Environmental Management

Marlborough, Sidney Joseph 04 May 2016 (has links)
Arsenic has been used throughout recorded history but during the industrial revolution widespread use led to global environmental impact. The two forms that should be considered in environment management are arsenate and arsenite. The calculations of environmental risk for arsenic exposure relies the toxicity of arsenite however, in well aeriated surface soils arsenate may be the predominate form. Ecological risk assessments based on arsenite studies will lead to restrictive remediation requirements that do not adequately reflect the level of risk. Arsenate resembles phosphate and as such has a greater affinity for phytoremediation. Phytoremediation is one of the most viable and cost effective cleanup techniques developed. Different mathematical approaches have been implemented to characterize phytoremediation systems to address concerns with performance. A system dynamic model is presented to describe solute transport in groundwater coupled to sorption by plant roots, translocation into plant stems, and evapotranspiration. The model was tested and assessed using published and peer-reviewed experimental data, to assess its capability to mimic phytoremediation processes. The model is consistent with previous research establishing the extraction process as a constringent factor for this cleanup technique. The model included modules that can estimate rainfall, seasonal temperature and growth. The modules allow for the independent verification of data before input into the model. The implementation of phytoremediation model can provide information about: pollutant-media-plant interaction, pollutant concentration and flow rate through the plant.
8

The Photodegradation of 2,6-dichloro-4-nitroaniline (DCNA) in Freshwater and Saltwater

Vebrosky, Emily Noelle 25 April 2016 (has links)
The fungicide 2,6-dichloro-4-nitroaniline (DCNA) is applied to crops grown in areas near both freshwater and saltwater bodies and it can enter the surface waters where it is susceptible to photolysis; limited information is published on the photodegradation of DCNA. It has been shown that the salinity of seawater can influence both the overall rate of degradation of chemicals and impact the distribution and types of photoproducts generated during the photodegradation processes of a pesticide. The photodegradation of DCNA was measured in distilled water, artificial seawater, estuarine water, and phosphate buffer to determine the degree of differences in the degradation rate in various matrices. The brominated analogue 2,6-dibromo-4-nitroaniline (DBNA) was measured identically to determine the impacts of other halogens on the degradation process. Solutions of DCNA and DBNA at a concentration of 1 ppm were prepared and irradiated for 24 hours in an Atlas SUNTEST XXL+ photochamber that mimics the wavelength distribution and intensity of sunlight. Dark controls were run simultaneously. Samples were withdrawn at 0, 2, 4, 6, 12, and 24 hours and analyzed for residual DCNA or DBNA using an Agilent 1260 Infinity High Performance Liquid Chromatograph. The formation of ions such as nitrate, nitrite, bromide, and chloride were measured using a Thermo Dionex ICS-5000+ Ion Chromatograph. The half-life of DCNA in distilled water was calculated to be 7.62 ± 0.094 hours and 7.37 ± 0.279 hours in artificial seawater; statistically there was no significant difference in the degradation rate through the first half-life. Analysis of the quick formation of nitrite and chloride ions, and later formation of nitrate ions, suggests photonucleophilic substitution processes are occurring as the compound is degrading, followed by further degradation of nitrite to nitrate likely also due to photolysis processes. Small aliphatic acids, maleic and fumaric acid, were detected after 12 hours of irradiation by HPLC indicating degradation of the aromatic ring structure. Differences in formation rate and decline for intermediate photoproducts were observed in seawater and distilled water suggesting salinity affects the rate of formation of this photoproduct.
9

Effects of Landscape Fragmentation on Land Loss

Cheng, Weijia 12 July 2016 (has links)
Coastal Louisiana, the seventh largest delta on earth, is one of the most vulnerable coastal areas in the United States of America (USA) because of its land loss problem. Coastal land loss is usually caused by many complicated factors. With the rapid increase in human activities, more studies on land loss have focused on the anthropogenic elements, but less on the pattern of the landscape. It is expected that the type of spatial arrangement, such as high degree of fragmentation, would affect the degree of land erosion. A quantitative evaluation of coastal landscape fragmentation and its influences on land loss would help coastal protection. The purpose of this research is to study the effects of landscape fragmentation on land loss in the Lower Mississippi River Basin (LMRB) region. The main scientific question addressed in this study is: does the degree of fragmentation influence the degree of coastal land loss? This thesis applied fractal analysis and spatial autocorrelation statistics to calculate the degree of fragmentation, using Landsat-TM land cover data in 1996 and 2010 with a pixel size of 30m * 30m. First, 100 samples of a 50-percent land-water ratio for each of the three box sizes 101*101, 51*51, and 31*31 pixels were extracted from the study area. Linear regressions were conducted to compute the relationship between fragmentation and land loss. The hypothesis is that the higher the degree of spatial fragmentation, the greater the degree of land loss. The results show that boxes with a higher degree of fragmentation had more land loss for box sizes of 51*51 and 31*31 with p-values less than 0.001. The relationship is not significant for 101*101 with p-values greater than 0.05. Thus, land fragmentation is a worthy element to be considered as a land loss factor. These results should be useful to the development of better strategies to strengthen the protection of a highly fragmented coast.
10

A model of proenvironmental behavior predicted by dispositional, situational and demographic variables: The case of Mexico.

Corral-Verdugo, Victor. January 1995 (has links)
The purpose of this study was to test a model of conservation behavior in a Mexican community. Reuse and recycling patterns of one-hundred families in a middle-sized city of Northwestern Mexico were analyzed using direct observations of reused and recycled items. Predictors of the studied behaviors were assessed by an inventory administered to housewives, which included self-reports, observations and event-test activities of dispositional variables (motives, competencies, beliefs, knowledge), demographic factors (age, income, education) and situational variables (storage facilities, presence of collectors of recyclables, use of radio, TV, newspapers and books). A comparison of responses to self-reports and observations of reused/recycled items showed a significant lack of correspondence between these measures. Therefore, observation was selected as the method best indicating reuse and recycling. These observations revealed that reuse is a more generalized conservation practice, while recycling is limited to selected items. Multiple regressions of dispositional, demographic and situational variables on both conservation behaviors showed that motives to reuse was the only significant direct predictor of reusing, while motives to recycling predicted recycling in a positive way, and facilities for storage had a significant but negative effect on recycling. However, the use of a structural equations models revealed the presence of significant indirect predictors of most of these variables on reuse and recycling. Motives and competencies to reuse/recycle positively affected conservation behaviors, but conservation beliefs did not; Competencies had a positive influence on motives to reuse and recycle, and the use of TV/radio negatively affected the motivation to reuse. Knowledge of reusables/recyclables had a positive effect on competencies, while reading books and newspapers had a significant influence on knowledge about reusables. The indirect effect of education on these conservation behaviors was manifested through its significant positive influence on reading books/newspapers and a significant negative effect on the use of radio and television. The presence of people collecting recyclables did not affect housewive's recycling while the possession of storage facilities negatively affected such a recycling practice.

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