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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.
151

Polycyclic Aromatic Hydrocarbons (PAHs) iIn the Diep And Plankenburg Rivers and potential remediation using charred Vitis vinifera (GRAPE) leaf litter

Awe, Adetunji Ajibola January 2019 (has links)
Thesis (DPhil (Chemistry))--Cape Peninsula University of Technology, 2019 / Occurrence of polycyclic aromatic hydrocarbons (PAHs) in freshwater systems may aggravate the water crisis currently being experienced in the Western Cape province of South Africa. However, there is dearth of data on the levels of PAHs, necessary for effective assessment of water quality as well as remediation strategies. This study therefore assessed levels of PAHs in two important freshwater systems in the Western Cape Province, South Africa. The potential of grape leaf litter for PAH abatement was also investigated. A solid-phase extraction - gas chromatography - flame ionisation detection (SPE-GC-FID) method was developed to simultaneously determine the 16 United States Environmental Protection Agency (US EPA) priority PAHs in environmental samples. Levels of 16 US EPA priority PAHs were assessed in water, sediment and plants from seven selected sites on the Diep and Plankenburg Rivers. Seasonal variations of some water quality parameters and PAHs levels in water and sediment samples were determined from the selected sites. Activated carbons produced from Vitis vinifera (grape) leaf litter were utilised for PAH-remediation. The SPE-GC-FID method developed for the 16 US EPA priority PAHs determination gave acceptable linearity (R2 > 0.999). Instrument detection limits ranged between 0.02 and 0.04 µg/mL and instrument quantification limits of between 0.06 and 0.13 µg/mL. Recovery studies were also acceptable (70.35 - 100.83%) with the exception of naphthalene that had lower recoveries. The average ∑16 PAHs detected in water samples at a given site, over a one-year period ranged from 73.90 to187.11 µg/L. The highest PAHs levels were detected in water samples from industrial areas of both rivers; chrysene (Chy) followed by benzo[a]anthracene (BaA) were the most abundant PAHs detected in water samples. Higher PAHs levels were detected in sediment samples relative to water samples; the average ∑16 PAHs detected in sediment samples at a given site, over a one-year period ranged from 6.048 to 39.656 µg/g. PAHs levels were also highest in sediment samples from industrial areas of the two rivers; benzo[b]fluoranthene (BbF) followed by benzo[k]fluoranthene (BkF) were the most abundant PAHs detected in sediment samples. The average ∑16 PAHs detected in plant samples [Phragmites australis (common reed) and Eichhornia crassipes (water hyacinth)] at a given site, ranged between 62.11 and 226.72 µg/g. Highest levels of PAHs were therefore detected in plant samples, suggesting possible bioaccumulation of PAHs in plant tissues. The bioaccumulation of PAHs by the plants also indicates the phytoremediation potential of these plants for PAHs remediation. The levels of PAHs measured in water and sediment samples were subjected to probabilistic risk assessment to predict the possibility of regulatory values being exceeded. The average percentage exceedence of 63.26 and 42.81 were obtained for PAHs in water samples of the Diep and Plankenburg Rivers respectively, while the corresponding average percentage exceedence obtained for sediment samples were 63.71 and 77.20. Vitis vinifera (grape) leaf litter showed enormous prospect as precursor for activated carbon. The yield of activated carbons obtained from grape leaf litter ranged from 44.65 to 58.40% and the Brunauer-Emmett-Teller (BET) surface area of up to 616.60 m2/g was obtained for activated carbons. The estimated adsorption capacities of the ZnCl2 and H3PO4 activated carbons for phenanthrene removal from aqueous solutions were 94.12 and 89.13 mg/g respectively. The environmental samples analysed were heavily contaminated with the 16 US EPA priority PAHs and the probabilistic risk assessment suggested risks of the carcinogenic PAHs at the levels measured in the environment. Vitis vinifera leaf litter, showed enormous potential as renewable precursor for activated carbon production, capable of removing varied contaminants from wastewater.
152

Developing Ultrasonically-Activated Persulfate as a Remediation Technology for Legacy and Emerging Contaminants

Fagan, William Peter January 2021 (has links)
No description available.
153

Residual Diesel Range Organics and Selected Frothers in Process Waters from Fine Coal Flotation

Morris, Joshua Powell 06 June 2013 (has links)
The purpose of this thesis is to examine some of the potential fates of processing reagents in a coal preparation plant.  The focus is specifically on petro-diesel (termed "diesel" in this paper), which is used as a collector in the flotation of fine coal.  Diesel range organics (DRO) and polyaromatic hydrocarbons (PAHs) are measured in aqueous samples using gas chromatography equipped with either a flame ionization detector (GC-FID) or a mass spectrometer (GC-MS).  Samples are subjected to a variety of test conditions in order to understand the behavior of diesel compounds in coal processing streams. Results show that frother and collector reagents are not likely to partition completely to a single fraction of the process slurry.  Further test work has shown that sub-ppm levels of DRO dominated by the water soluble fraction of diesel are expected to be present in process waters; however, PAHs and insoluble DRO may be removed via volatilization and/or degradation.  DRO and PAHs are also expected to be desorbed from coal particles when contacted with fresh water.  Flotation tests have revealed that low levels of DRO are found in both the concentrate and tailings processing streams with slightly higher concentrations being found in the concentrate stream.  From the tests performed in this thesis, it appears as though there is no apparent environmental concern when coal preparation plants are operating under normal conditions. / Master of Science
154

Environmental Hazard Assessment of Heterocyclic Polyaromatic Hydrocarbons in Aquatic Compartment: Biodegradation, Bioaccumulation, Acute Toxicity and Chronic Toxicity

Çelik, Göksu 14 February 2024 (has links)
Nitrogen-, sulfur-, and oxygen-substituted heterocyclic polyaromatic hydrocarbons (heterocyclic PAHs) are ubiquitous in all environmental compartments, often co-occurring with their unsubstituted carbocyclic analogues. However, they have received little attention in the hazard assessment of contaminated sites and little is known about their fate and impacts. Due to their higher polarity resulting from the presence of electronegative atoms possessing lone electron pairs, most heterocycles are expected to be less toxic and bioaccumulative than their homocyclic counterparts, which is perhaps why research on their hazard and fate is much more limited. If this assumption is not true (e.g., because factors other than polarity/hydrophobicity drive their hazard), this may lead to an underestimation of the risks posed by contaminated sites or emissions. Therefore, the main objectives of this thesis are (1) to improve the understanding of the physicochemical properties, biodegradability, ecotoxicity, bioaccumulation, and mobility of these compounds in environmental contexts, (2) to evaluate the effectiveness of different modeling approaches in accurately predicting their properties, and (3) to tackle experimental barriers by designing robust techniques that can produce reliable and reproducible data output in the long run. From the large family of heterocycles, structurally comparable representative compounds with log KOW values (as a measure of hydrophobicity) ranging over four orders of magnitude were selected as model structures. First, the most environmentally relevant physicochemical properties of heterocyclic PAHs were investigated, including water solubility (SW), n-octanol-water partition coefficient (KOW), and organic carbon-water partition coefficient (KOC). The effect of molecular size, type and number of heteroatoms on the solubility and partition coefficients was investigated. These properties were then used to test the performance of in silico models, including Quantitative Structure-Property Relationship (QSPR), Polyparameter Linear Free Energy Relationship (pp-LFER), and Conductor-like Screening Model for Realistic Solvation (COSMO-RS), that predict these properties. A screening-level environmental hazard assessment was performed by integrating the data and evidence from multiple sources. The screening results revealed (i) high hazard for 4- and 5-ring compounds mainly due to high persistence and bioaccumulation potential, (ii) limited availability of experimental data, and (iii) notable uncertainty due to the limited applicability domain of the models, stressing the urgent need for a detailed hazard assessment for this group of compounds. The persistence of heterocyclic PAHs in the environment was assessed experimentally through a series of biodegradation tests under aerobic conditions. These included ultimate biodegradation, primary biodegradation and inoculum toxicity tests at different exposure concentrations. None of the test substances (≥3 rings) were found to be readily biodegradable. Therefore, to stimulate the biodegradation process, the microbial community from a wastewater treatment plant was adapted to a mixture of heterocyclic PAHs and biodegradation tests were performed with either adapted or non-adapted bacteria. Surprisingly, there were trade-offs in bacterial adaptation: a positive outcome (degradation of carbazole) is accompanied by a less desirable outcome (increased sensitivity to toxic effects of benzo[c]carbazole). Four of the compounds were identified as primarily biodegradable, while five compounds showed no evidence of biodegradation in any of the tests, indicating a high potential for environmental persistence. Predictions from mathematical models were also compared with measured results and it was found that the models were only partially successful in predicting the degradation timeframe of the heterocycles tested. Furthermore, the short-term acute aquatic toxicity of heterocyclic PAHs was investigated using three surrogate species from different trophic levels of the aquatic food web, including bacteria (Aliivibrio fischeri), unicellular algae (Raphidocelis subcapitata), and water fleas (Daphnia magna). In order to maintain a stable exposure and to avoid loss of concentration caused mainly due to sorption, the passive dosing method was adapted to routine test protocols. Most of the compounds were identified as highly toxic to the tested organisms, and non-polar narcosis (baseline toxicity) was found to be the most likely mode of toxic action for the tested chemicals. Membrane-water partition coefficients (KMW) of heterocyclic PAHs were also determined by solid-supported lipid membrane binding experiments and modeling. The measured KMW values were closely aligned with the KOW values, suggesting that both may be good descriptors for predicting the baseline toxicity and bioaccumulation potential of the tested heterocyclic PAHs. Lastly, the long-term chronic reproductive toxicity and bioaccumulation of large heterocyclic PAHs were investigated using Daphnia magna as an aquatic model organism. The passive dosing method ensured constant exposure even at very low concentration levels (70 ng L-1 to 68 µg L-1) in large and complex experimental systems. Given the enormous time and effort required to conduct long-term toxicity tests with minimal data output, a method was developed to assess chronic toxicity and bioaccumulation potential in a single test. All four substances tested were highly toxic and bioaccumulative in Daphnia magna. However, daphnids’ fecundity recovered rapidly from the toxic effects of the heterocycles during the depuration period in the absence of chemicals. The Predicted No Effect Concentrations (PNECs) of the test compounds were also estimated from the chronic toxicity data and ranged from 1 to 150 ng L-1 in a freshwater environment. Due to the lack of regulation and attention to these compounds, no systematic environmental monitoring data are available for their concentrations in freshwater. However, environmental concentrations of heterocyclic PAHs appear to be higher than the PNECs, particularly at contaminated sites. Thus, the tested heterocycles are of high concern in terms of risks to ecosystems and human health. Overall, the results of this research not only contribute to a comprehensive understanding and progress in the environmental hazard assessment of heterocyclic PAHs, but also present several methodological advances that can be applied to future testing of other challenging substances commonly referred to as 'difficult-to-test'. / Stickstoff-, schwefel- und sauerstoffsubstituierte heterocyclische polyaromatische Kohlenwasserstoffe (heterocyclische PAK) sind in allen Umweltkompartimenten gegenwärtig und treten häufig zusammen mit ihren homocyclischen Analoga auf. Bei der Gefährdungsbeurteilung kontaminierter Standorte wurde ihnen bisher verhältnismäßig wenig Aufmerksamkeit geschenkt, zudem ist über ihr Verhalten und ihre Ökotoxizität nur wenig bekannt. Aufgrund ihrer höheren Polarität, die auf das Vorhandensein elektronegativer Atome zurückzuführen ist, ging man bislang davon aus, dass die meisten heterocyclischen PAK mobiler und weniger toxisch sind als ihre homocyclischen Pendants, weshalb sie wahrscheinlich bislang vergleichsweise wenig studiert wurden. Sollte die Annahme einer geringeren Toxizität nicht zutreffen, weil beispielsweise andere Mechanismen als die Polarität/Hydrophobie für ihre Gefährdung verantwortlich sind, könnte dies zu einer Unterschätzung der Risiken, die von kontaminierten Standorten oder anderen Emissionen ausgehen, führen. Die Hauptziele dieser Arbeit bestehen daher darin, (1) ein umfassenderes Verständnis der physikalisch-chemischen Eigenschaften, der biologischen Abbaubarkeit, der Ökotoxizität, der Bioakkumulation und der Mobilität dieser Verbindungen in der Umwelt zu erlangen; (2) eine Bewertung verschiedener Modellierungsansätze zur Vorhersage dieser Eigenschaften durchzuführen und (3) experimentelle Hindernisse zu überwinden, indem robustere Techniken entwickelt werden, die langfristig zuverlässige und reproduzierbare Daten liefern können. Aus der sehr breiten Gruppe der heterocyclischen Verbindungen wurden strukturell vergleichbare repräsentative Verbindungen mit unterschiedlichen log KOW-Werten (als Maß für die Hydrophobie), die vier Größenordnungen abdecken, als Modellstrukturen ausgewählt. Zunächst erfolgte eine Untersuchung umweltrelevanter physikalisch-chemischer Eigenschaften dieser heterocyclischen PAK, wie die Wasserlöslichkeit (SW), der n-Octanol-Wasser-Verteilungskoeffizient (KOW) und der Verteilungskoeffizient bezogen auf den organischen Kohlenstoff und Wasser (KOC). Dabei wurden die Auswirkungen von Molekülgröße, Art und Anzahl der Heteroatome auf die Löslichkeit und die Verteilungskoeffizienten systematisch untersucht. Diese experimentell ermittelten Parameter wurden dann verwendet, um die Leistung von In-silico-Modellen zu testen, einschließlich der quantitativen Struktur-Eigenschafts-Beziehung (QSPR), der linearen Polyparameter-Energie-Beziehung (pp-LFER) und des Conductor-like Screening Model for Realistic Solvation (COSMO-RS), die diese Eigenschaften vorhersagen. Zudem wurde eine Umweltverträglichkeitsprüfung auf Screening-Ebene durchgeführt, bei der Daten aus verschiedenen Quellen berücksichtigt wurden. Den Screening-Ergebnissen zufolge ist davon auszugehen, dass kleine Verbindungen mit zwei oder drei Ringen in der Umwelt mobil sind, während größere heterocyclische PAK im Allgemeinen als bioakkumulierbare Stoffe identifiziert wurden, was auf ein erhebliches Gefahrenpotenzial hinweist. Die Persistenz von heterocyclischen PAK wurde experimentell durch eine Reihe von Tests zum biologischen Abbau unter aeroben Bedingungen untersucht. Dazu gehörten Tests zur Mineralisierung, zum biologischen Primärabbau und zur Inokulumtoxizität bei unterschiedlichen Expositionskonzentrationen. Keine der Prüfsubstanzen mit drei oder mehr Kohlenstoffringen erwies sich als biologisch gut/schnell abbaubar. Um den biologischen Abbauprozess zu stimulieren, wurde daher die mikrobielle Gemeinschaft aus einer Kläranlage an das Gemisch heterocyclischer PAK angepasst, wobei die Tests zum biologischen Abbau entweder mit angepassten oder nicht angepassten Bakterien durchgeführt wurden. Überraschenderweise gab es bei der bakteriellen Anpassung Widersprüche: positive Effekte (wie der bessere Abbau von Carbazol) gehen mit weniger wünschenswerten Ergebnissen (erhöhte Toxizität gegenüber Benzo[c]carbazol) einher. Für vier der betrachteten Verbindungen wurde ein biologischer Primärabbau festgestellt, während fünf Substanzen in keinem der Tests Anzeichen für eine mikrobielle Umsetzung zeigten, was auf ein hohes Potenzial für eine Persistenz in der Umwelt hindeutet. Die Vorhersagen softwaregestützter Modelle wurden ebenfalls mit den Messergebnissen verglichen, und es zeigte sich, dass die Modelle bei der Vorhersage der Abbaukinetik der getesteten Heterocyclen nur teilweise übereinstimmende Ergebnisse lieferten. Darüber hinaus wurde die akute Kurzzeittoxizität heterocyclischer PAK anhand von drei Arten aus verschiedenen trophischen Ebenen des aquatischen Nahrungsnetzes untersucht: Bakterien (Aliivibrio fischeri), einzellige Algen (Raphidocelis subcapitata) und Wasserflöhe (Daphnia magna). Um eine stabile Exposition aufrechtzuerhalten und Verluste, zum Beispiel durch Sorption an Gefäßwandungen, zu vermeiden, wurde die Methode des „passive dosing“ an Routinetestprotokolle angepasst. Die meisten Verbindungen wurden in diesen Tests als hochgiftig für die getesteten Organismen identifiziert, wobei festgestellt werden konnte, dass unpolare Narkose (Basistoxizität) die wahrscheinlichste Art der toxischen Wirkung der getesteten Chemikalien ist. Darüber hinaus wurden die Membran-Wasser-Verteilungskoeffizienten (KMW) der heterocyclischen PAK durch Lipidmembran-Bindungsexperimente auf festem Trägermaterial sowie mit Hilfe von Vorausberechnungen (Modellierung) bestimmt. Die gemessenen KMW-Werte stimmten eng mit den KOW-Werten überein, was darauf hindeutet, dass beide Werte gute Deskriptoren für die Vorhersage der Basistoxizität bzw. des Bioakkumulationspotenzials der getesteten heterocyclischen PAK sein können. Schließlich wurden die langfristige chronische Reproduktionstoxizität und die Bioakkumulation großer heterocyclischer PAK mit Daphnia magna als aquatischer Modellorganismus untersucht. Die „passive dosing method“ gewährleistete eine konstante Exposition selbst bei sehr niedrigen Konzentrationen (70 ng L-1 bis 68 µg L-1) in groß angelegten und komplexen Versuchssystemen. Angesichts des enormen Zeit- und Arbeitsaufwands, der für die Durchführung von Langzeit-Toxizitätstests erforderlich ist, wurde eine Methode entwickelt, um die chronische Toxizität sowie das Bioakkumulationspotenzial in einem einzigen Test zu bewerten. Alle vier getesteten Substanzen waren gegenüber Daphnia magna hochtoxisch und stark bioakkumulierend. Unerwarteterweise erholte sich die Reproduktionsfähigkeit der Daphnien jedoch schnell von den toxischen Wirkungen der Heterocyclen, wenn die Chemikalienexposition endete. Die PNECs (Predicted No Effect Concentrations) der Testsubstanzen wurden ebenfalls anhand der Daten zur chronischen Toxizität verglichen. Die Werte lagen in einer Süßwasserumgebung zwischen 1 und 150 ng L-1 (PNEC). Für die meisten Testverbindungen gibt es keine Informationen zu Monitoringdaten in der Umwelt. Die Umweltkonzentrationen heterocyclischer PAK scheinen jedoch höher zu sein als die PNEC-Werte, insbesondere an kontaminierten Standorten, was eine Gefahr für die Ökosysteme und die menschliche Gesundheit darstellt. Insgesamt tragen die Ergebnisse dieser Forschungsarbeit nicht nur zu einem umfassenderen Verständnis und zu Fortschritten bei der Bewertung der von heterocyclischen PAK ausgehenden Umweltgefahren bei, sondern liefern auch mehrere methodische Verbesserungen, die in Zukunft bei der Prüfung anderer Stoffe, die gemeinhin als 'schwierig zu testen' bezeichnet werden, angewendet werden können.
155

Determination of degradative gene frequencies: Applications in polycyclic aromatic hydrocarbon contaminated sediments

Mumy, Karen Lynn 25 February 2004 (has links)
No description available.
156

High Performance Liquid Chromatography of Petroleum Asphaltenes and Capillary Electrophoresis of Glycosaminoglycan Carbohydrates

Loegel, Thomas N. 03 December 2012 (has links)
No description available.
157

CHARACTERIZATION OF BACTERIAL COMMUNITIES OF RIVERBANK SEDIMENTS CONTAMINATED WITH POLYCYCLIC AROMATIC HYDROCARBONS

Johnston, Gloria P. 24 April 2014 (has links)
No description available.
158

Evaluation of Water-only Decontamination for Firefighters’ Turnout Gear

Calvillo, Anthony 30 October 2018 (has links)
No description available.
159

BIODEGRADATION AND BIOAVAILABILITY STUDIES ON AGED PAH-CONTAMINATED SEDIMENT

LEI, LI 30 June 2003 (has links)
No description available.
160

PHOTOLYTIC DEGRADATION OF ENVIRONMENTALLY IMPORTANT ORGANIC CONTAMINANTS IN NOVEL ROOM TEMPERATURE IONIC LIQUIDS

YANG, QIAOLIN 31 March 2004 (has links)
No description available.

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