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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

Organic Contaminant Release from Melting Snow

Meyer, Torsten 18 March 2010 (has links)
Snow efficiently scavenges organic contaminants from the atmosphere. Those chemicals can be released in short, concentrated pulses during spring snowmelt, potentially affecting both aquatic and terrestrial environments. In order to investigate the behavior of organic contaminants in melting snow laboratory experiments were conducted using artificial snow spiked with the organic target substances naphthalene, phenanthrene, pyrene, benzo(ghi)perylene, lindane, and atrazine. The behavior of those substances during melting is dependent on their partitioning between the different phases present within the bulk snow. Very water soluble organic chemicals, such as atrazine, are preferentially released at an early stage of melting similar to inorganic ions. This first chemical flush becomes more pronounced when a deep, aged, and relatively homogeneous snow pack is exposed to intense melting. Hydrophobic substances attached to particles, such as high molecular weight polycyclic aromatic hydrocarbons, are often released at the very end of the melt period. Dirt cones at the surface of a deep snow pack amplify this late chemical enrichment. Whereas chemicals that are clearly hydrophilic or hydrophobic are likely to be released in pulse loads, the snowmelt behavior of chemicals with intermediate partitioning properties, such as lindane, is more dependent on the varying snow pack and melt characteristics. A notable fraction of volatile chemicals may transfer from the melting snow pack to the lower atmosphere due to evaporation. Shallow snow covers in temperate regions with depths below 10cm that are exposed to recurrent melt phases during the winter are less likely to lead to pulse releases. When the melt water runs off as overland flow over frozen ground, pollutants are directly transferred into catchment streams, and their water quality is affected most. Melt water flow along the soil subsurface dilutes and buffers organic contaminant loads. The findings of this laboratory study may assist in the development of contaminant fate models that includes snowmelt processes. The results may further help to explain observations of organic contaminants in natural snow environments.
2

Organic Contaminant Release from Melting Snow

Meyer, Torsten 18 March 2010 (has links)
Snow efficiently scavenges organic contaminants from the atmosphere. Those chemicals can be released in short, concentrated pulses during spring snowmelt, potentially affecting both aquatic and terrestrial environments. In order to investigate the behavior of organic contaminants in melting snow laboratory experiments were conducted using artificial snow spiked with the organic target substances naphthalene, phenanthrene, pyrene, benzo(ghi)perylene, lindane, and atrazine. The behavior of those substances during melting is dependent on their partitioning between the different phases present within the bulk snow. Very water soluble organic chemicals, such as atrazine, are preferentially released at an early stage of melting similar to inorganic ions. This first chemical flush becomes more pronounced when a deep, aged, and relatively homogeneous snow pack is exposed to intense melting. Hydrophobic substances attached to particles, such as high molecular weight polycyclic aromatic hydrocarbons, are often released at the very end of the melt period. Dirt cones at the surface of a deep snow pack amplify this late chemical enrichment. Whereas chemicals that are clearly hydrophilic or hydrophobic are likely to be released in pulse loads, the snowmelt behavior of chemicals with intermediate partitioning properties, such as lindane, is more dependent on the varying snow pack and melt characteristics. A notable fraction of volatile chemicals may transfer from the melting snow pack to the lower atmosphere due to evaporation. Shallow snow covers in temperate regions with depths below 10cm that are exposed to recurrent melt phases during the winter are less likely to lead to pulse releases. When the melt water runs off as overland flow over frozen ground, pollutants are directly transferred into catchment streams, and their water quality is affected most. Melt water flow along the soil subsurface dilutes and buffers organic contaminant loads. The findings of this laboratory study may assist in the development of contaminant fate models that includes snowmelt processes. The results may further help to explain observations of organic contaminants in natural snow environments.
3

Towards a Structural and Methodological Improvement of Eutrophication Modelling

Ramin, Maryam 09 August 2013 (has links)
The credibility of the scientific methodology of mathematical models and their adequacy to form the basis of public policy decisions has frequently been challenged. Skeptical views of the scientific value of modelling argue that there is no true model of an ecological system, but rather several adequate descriptions of different conceptual basis and structure. The purpose of this work was to first advance the Bayesian calibration of process-based models for guiding the water quality criteria setting process in Hamilton Harbour, Ontario, Canada. The analysis suggests that the water quality targets for total phosphorus and chlorophyll a concentrations will likely be met, if the recommendation for phosphorus loading at the level of 142 kg day-1 is achieved. My dissertation also examines how the Bayesian approach can effectively support the decision making process by synthesizing the predictions of different models developed for the same system. The model averaging approach consolidates the finding that the existing total phosphorus goal is most likely unattainable. The discrepancy between the chlorophyll a predictions of the two models pinpoints the need to delve into the dynamics of phosphorus in the sediment-water column interface. This work also aims to examine statistical formulations that explicitly accommodate the covariance among the process error terms for various model endpoints. The analysis suggests that the statistical characterization of the model error can be influential to the inference drawn by a modelling exercise. Finally, my dissertation challenges the capacity of the ecological foundation of eutrophication models to predict the role of nutrient regeneration. It shows that the recycled nutrients can be significant drivers in low as well as in high-productivity ecosystems depending on the period of the year examined. My dissertation also discusses several prescriptive guidelines that should be helpful towards a structural and methodological improvement of eutrophication modelling.
4

Towards a Structural and Methodological Improvement of Eutrophication Modelling

Ramin, Maryam 09 August 2013 (has links)
The credibility of the scientific methodology of mathematical models and their adequacy to form the basis of public policy decisions has frequently been challenged. Skeptical views of the scientific value of modelling argue that there is no true model of an ecological system, but rather several adequate descriptions of different conceptual basis and structure. The purpose of this work was to first advance the Bayesian calibration of process-based models for guiding the water quality criteria setting process in Hamilton Harbour, Ontario, Canada. The analysis suggests that the water quality targets for total phosphorus and chlorophyll a concentrations will likely be met, if the recommendation for phosphorus loading at the level of 142 kg day-1 is achieved. My dissertation also examines how the Bayesian approach can effectively support the decision making process by synthesizing the predictions of different models developed for the same system. The model averaging approach consolidates the finding that the existing total phosphorus goal is most likely unattainable. The discrepancy between the chlorophyll a predictions of the two models pinpoints the need to delve into the dynamics of phosphorus in the sediment-water column interface. This work also aims to examine statistical formulations that explicitly accommodate the covariance among the process error terms for various model endpoints. The analysis suggests that the statistical characterization of the model error can be influential to the inference drawn by a modelling exercise. Finally, my dissertation challenges the capacity of the ecological foundation of eutrophication models to predict the role of nutrient regeneration. It shows that the recycled nutrients can be significant drivers in low as well as in high-productivity ecosystems depending on the period of the year examined. My dissertation also discusses several prescriptive guidelines that should be helpful towards a structural and methodological improvement of eutrophication modelling.
5

A conceptual model for sustainability (John Berger)

Wanden-Hannay (nee Witten-Hannah), Shalema January 2005 (has links)
The ideas of Berger are used in this thesis to explore humankind's struggle to achieve greater sustainability. In his descriptions of the peasantry and modern high-energy cultures of progress Berger insightfully crystallises and represents graphically the observation made by many authors writing in different contexts and from within various disciplines that there have been two fundamentally different systems of beliefs and values in history. His conception of ‘ cultures of survival’ and ‘cultures of progress ’ is used in this thesis to develop a conceptual model for sustainability. The basic idea underlying the conceptual model for sustainability is that cultural systems self-regulate or self-correct as they strive to achieve balance in their relationship to higher systems levels of the biosphere, while improving quality of life. Over large time scales self-regulation takes the form of quite radical transformations in cultural system's key defining beliefs and values. The model holds that the process of self-regulation results in societies moving back and forth along a cultural continuum of beliefs and values, represented at one end by Berger's cultures of survival and at the other by his cultures of progress. This system of self-regulation is fraught with risks arising from factors like the inherently conservative nature of cultural systems, which reduce the fit or alignment between systems of beliefs and values and their context and in doing so generate un-sustainability. The model suggests that over large spans of time movement back and forth along the cultural continuum creates the dynamic balance needed to achieve greater sustainability, at least if irreversible degradation of the biosphere's life-supporting systems and extinction can be avoided. This conceptual model for sustainability demonstrates the validity of the central hypothesis of the thesis, which is that Berger's ideas in the ‘Historical Afterword’ to ‘Pig Earth’ are important and have a valuable contribution to make to the discourse on sustainability. / Subscription resource available via Digital Dissertations only.
6

A conceptual model for sustainability (John Berger)

Wanden-Hannay (nee Witten-Hannah), Shalema January 2005 (has links)
The ideas of Berger are used in this thesis to explore humankind's struggle to achieve greater sustainability. In his descriptions of the peasantry and modern high-energy cultures of progress Berger insightfully crystallises and represents graphically the observation made by many authors writing in different contexts and from within various disciplines that there have been two fundamentally different systems of beliefs and values in history. His conception of ‘ cultures of survival’ and ‘cultures of progress ’ is used in this thesis to develop a conceptual model for sustainability. The basic idea underlying the conceptual model for sustainability is that cultural systems self-regulate or self-correct as they strive to achieve balance in their relationship to higher systems levels of the biosphere, while improving quality of life. Over large time scales self-regulation takes the form of quite radical transformations in cultural system's key defining beliefs and values. The model holds that the process of self-regulation results in societies moving back and forth along a cultural continuum of beliefs and values, represented at one end by Berger's cultures of survival and at the other by his cultures of progress. This system of self-regulation is fraught with risks arising from factors like the inherently conservative nature of cultural systems, which reduce the fit or alignment between systems of beliefs and values and their context and in doing so generate un-sustainability. The model suggests that over large spans of time movement back and forth along the cultural continuum creates the dynamic balance needed to achieve greater sustainability, at least if irreversible degradation of the biosphere's life-supporting systems and extinction can be avoided. This conceptual model for sustainability demonstrates the validity of the central hypothesis of the thesis, which is that Berger's ideas in the ‘Historical Afterword’ to ‘Pig Earth’ are important and have a valuable contribution to make to the discourse on sustainability. / Subscription resource available via Digital Dissertations only.
7

A conceptual model for sustainability (John Berger)

Wanden-Hannay (nee Witten-Hannah), Shalema January 2005 (has links)
The ideas of Berger are used in this thesis to explore humankind's struggle to achieve greater sustainability. In his descriptions of the peasantry and modern high-energy cultures of progress Berger insightfully crystallises and represents graphically the observation made by many authors writing in different contexts and from within various disciplines that there have been two fundamentally different systems of beliefs and values in history. His conception of ‘ cultures of survival’ and ‘cultures of progress ’ is used in this thesis to develop a conceptual model for sustainability. The basic idea underlying the conceptual model for sustainability is that cultural systems self-regulate or self-correct as they strive to achieve balance in their relationship to higher systems levels of the biosphere, while improving quality of life. Over large time scales self-regulation takes the form of quite radical transformations in cultural system's key defining beliefs and values. The model holds that the process of self-regulation results in societies moving back and forth along a cultural continuum of beliefs and values, represented at one end by Berger's cultures of survival and at the other by his cultures of progress. This system of self-regulation is fraught with risks arising from factors like the inherently conservative nature of cultural systems, which reduce the fit or alignment between systems of beliefs and values and their context and in doing so generate un-sustainability. The model suggests that over large spans of time movement back and forth along the cultural continuum creates the dynamic balance needed to achieve greater sustainability, at least if irreversible degradation of the biosphere's life-supporting systems and extinction can be avoided. This conceptual model for sustainability demonstrates the validity of the central hypothesis of the thesis, which is that Berger's ideas in the ‘Historical Afterword’ to ‘Pig Earth’ are important and have a valuable contribution to make to the discourse on sustainability. / Subscription resource available via Digital Dissertations only.
8

A conceptual model for sustainability (John Berger)

Wanden-Hannay (nee Witten-Hannah), Shalema January 2005 (has links)
The ideas of Berger are used in this thesis to explore humankind's struggle to achieve greater sustainability. In his descriptions of the peasantry and modern high-energy cultures of progress Berger insightfully crystallises and represents graphically the observation made by many authors writing in different contexts and from within various disciplines that there have been two fundamentally different systems of beliefs and values in history. His conception of ‘ cultures of survival’ and ‘cultures of progress ’ is used in this thesis to develop a conceptual model for sustainability. The basic idea underlying the conceptual model for sustainability is that cultural systems self-regulate or self-correct as they strive to achieve balance in their relationship to higher systems levels of the biosphere, while improving quality of life. Over large time scales self-regulation takes the form of quite radical transformations in cultural system's key defining beliefs and values. The model holds that the process of self-regulation results in societies moving back and forth along a cultural continuum of beliefs and values, represented at one end by Berger's cultures of survival and at the other by his cultures of progress. This system of self-regulation is fraught with risks arising from factors like the inherently conservative nature of cultural systems, which reduce the fit or alignment between systems of beliefs and values and their context and in doing so generate un-sustainability. The model suggests that over large spans of time movement back and forth along the cultural continuum creates the dynamic balance needed to achieve greater sustainability, at least if irreversible degradation of the biosphere's life-supporting systems and extinction can be avoided. This conceptual model for sustainability demonstrates the validity of the central hypothesis of the thesis, which is that Berger's ideas in the ‘Historical Afterword’ to ‘Pig Earth’ are important and have a valuable contribution to make to the discourse on sustainability. / Subscription resource available via Digital Dissertations only.
9

A conceptual model for sustainability (John Berger)

Wanden-Hannay (nee Witten-Hannah), Shalema January 2005 (has links)
The ideas of Berger are used in this thesis to explore humankind's struggle to achieve greater sustainability. In his descriptions of the peasantry and modern high-energy cultures of progress Berger insightfully crystallises and represents graphically the observation made by many authors writing in different contexts and from within various disciplines that there have been two fundamentally different systems of beliefs and values in history. His conception of ‘ cultures of survival’ and ‘cultures of progress ’ is used in this thesis to develop a conceptual model for sustainability. The basic idea underlying the conceptual model for sustainability is that cultural systems self-regulate or self-correct as they strive to achieve balance in their relationship to higher systems levels of the biosphere, while improving quality of life. Over large time scales self-regulation takes the form of quite radical transformations in cultural system's key defining beliefs and values. The model holds that the process of self-regulation results in societies moving back and forth along a cultural continuum of beliefs and values, represented at one end by Berger's cultures of survival and at the other by his cultures of progress. This system of self-regulation is fraught with risks arising from factors like the inherently conservative nature of cultural systems, which reduce the fit or alignment between systems of beliefs and values and their context and in doing so generate un-sustainability. The model suggests that over large spans of time movement back and forth along the cultural continuum creates the dynamic balance needed to achieve greater sustainability, at least if irreversible degradation of the biosphere's life-supporting systems and extinction can be avoided. This conceptual model for sustainability demonstrates the validity of the central hypothesis of the thesis, which is that Berger's ideas in the ‘Historical Afterword’ to ‘Pig Earth’ are important and have a valuable contribution to make to the discourse on sustainability. / Subscription resource available via Digital Dissertations only.
10

The Disposable Camera: Image, Energy, Environment

Bozak, Nadia 28 July 2008 (has links)
“The Disposable Camera” theorizes the relationship between the cinematic image and energy resources. Framed by the emergent carbon-neutral cinema, the recent UCLA report on the film industry’s environmental footprint, as well as common perceptions about digital sustainability, “The Disposable Camera” posits that cinema has always been aware of its connection to the environment, the realm from which it sources its power, raw materials and, often enough, subject matter. But because the natural environment is so inextricably embedded within film’s basic means of production, distribution and reception, its effects remain as overlooked as they are complex. “The Disposable Camera” argues that cinematic history and theory can and indeed ought to be reappraised against the emerging ascendancy of environmental politics, all films; as such, all cinema could logically be included within the analytical parameters of this project. Primary focus, however, is given to documentary cinema, as well as notable experimental and narrative films. Selected texts do not overtly represent an environmental issue; rather, they reflexively engage with and theorize themselves as films, thus addressing the technological, industrial, and resource-derived essence of the moving image. Of import here are films that reveal how specific formal or aesthetic choices evidence and critique the ideology attached to resource consumption and/ or abuse. While it composes a distinctly environmental trajectory of the cinematic image, this project likewise historicizes and critiques these same stages and also challenges the utopian and/ or apocalyptical tendencies challenging eco-politics. Additionally, “The Disposable Camera” is committed to mapping out the shift from a distinctly tangible celluloid-based cinematic infrastructure to the ostensibly immaterial form of digital filmmaking. Indeed, the tension that now pits cinema’s material past against its immaterial future corresponds with the decline of natural reality on the one hand and the rise of cyber realities on the other, a parallel condition that fully evidences the increasingly palpable overlap between environmental and cinematic politics.

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