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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.
11

Fate Mechanisms and Removal of Tetrabromobisphenol-A (2,2’,6,6’-Tetrabromo-4,4’-isopropylidenediphenol) in the Activated Sludge Process

Potvin, Christopher Michael 10 May 2012 (has links)
A novel method for determination of tetrabromobisphenol-A (TBBPA), was developed using gas chromatography-negative ion chemical ionization-mass spectrom- etry (GC-NCI-MS). Samples of municipal wastewater treatment plant (WWTP) influent were analyzed for TBBPA. Levels ranged from 1 to 41 ng/L, with an average of 20 ± 14 ng/L. Matrix effects were shown to be 30 ± 17 % in the influent and -30 ± 11 % in membrane permeate. The method limit of quantitation was 0.1 ng/L TBBPA. Sorption of TBBPA to fresh mixed-liquor suspended solids (MLSS) from a membrane bioreactor (MBR) were studied. In a kinetic study, sorption was found to be essentially complete after 12 hours of exposure to MLSS. Log Koc and log Kd were measured at 4.7 ± 0.8 and 1.9 ± 0.8 respectively (n = 22). These values were much higher than modelled estimates based on Kow (p ≥ 0.05), and higher than modelled estimates based on Kow and pKa (p ≥ 0.05). Data was successfully modelled using the Freundlich isotherm, having a Kf value of 8.5 and an n value of 1.7. TBBPA adsorbed to borosilicate glassware, with a wall-loss coefficient (Kw) of 0.15 ± 0.1 (n ≥ 3). TBBPA levels in WWTP influent varied from 13 to 29 ng/L while effluent concentrations varied from 0 to 2.2 ng/L over the same period. Three pilot-scale membrane bioreactors (MBRs) removed less TBBPA during the same time period, though MBR removal was also significant (p ≥ 0.05). Increasing MBR sludge residence time (SRT) increased removal at the 86 % confidence interval (p = 0.14). A nitrifying MABR was shown to remove TBBPA significantly when spiked with ammonia and TBBPA (p ≥ 0.05), showing that nitrifying bacteria can degrade TBBPA. An MABR hollow fibre was found to adsorb TBBPA. Various soluble microbial products (SMP) were studied from MBRs fed munici- pal influent. Using current measurement practices, SMP were shown to be sensitive to matrix effects. Use of the standard addition technique (SA) can compensate for this. Measurements using SA showed SMP degrades rapidly during storage in the fridge and due to freezing. SA was also used to compare commonly used SMP extraction techniques, and showed that extraction method influences recovery.
12

Brominated flame retardants - sources and exposure pathways

Leisa-Maree LeontjewToms Unknown Date (has links)
Summary Polybrominated diphenyl ethers (PBDEs) are a class of brominated flame retardants. The addition of these chemicals to electrical and electronic equipment, building materials, carpet and textiles reduces flammability and therefore harm and destruction caused by unwanted fire. These chemicals are now internationally ubiquitous in the environment and humans because of their increased usage and physical and chemical properties of persistence and lipophilicity. Although Australian data on both the concentrations and the sources and exposure pathways was limited, a preliminary study of PBDEs in 10 pools of human blood serum revealed that concentrations of PBDEs in Australia were comparatively higher than most countries with the exception of Canada and the USA. The aim of this project was to determine the concentrations of PBDEs in the Australian population and to examine the possible sources and pathways of exposure in humans. Experimental evaluation of PBDE exposure matrices included samples of: sediment (n=46), air (n=19), dust (n=19), surface wipes (n=10) and human milk (157 samples combined into 17 pools, n=10 individual samples); and the general population using human blood serum (10552 samples combined into 169 pools). With accumulating evidence regarding age differences in PBDE concentrations, the scope of this project was broadened to include a focus on infants and young children. This study found that PBDE contamination was widespread in the Australian environment and human population. In sediment, PBDEs were relatively low at the majority of sites with mean ± standard deviation and median ΣPBDE concentrations across all sites of 4707 ± 12580 and 305 pg g-1 dw, respectively. There were elevated concentrations found downstream of sewerage treatment plants; in areas dominated by industrial and urban land-use types; and in estuarine compared to freshwater environments. PBDEs were detected in air, dust and surface wipes. Concentrations on the whole were found to be higher indoors compared to outdoors and in offices compared to homes. ΣPBDE concentrations ranged from 0.5 -179 pg/m3 for homes and 15 - 487 pg/m3 for offices and at the two outdoor sites the concentrations were 1.7 and 6.8 pg/m3. PBDEs were detected on 9 out of 10 surfaces (e.g. television, refrigerator, DVD player) sampled and ranged from non-detectable to 5985 pg/cm2 while in dust, ΣPBDEs ranged from 87 - 733 ng/g dust in homes and 583 - 3070 ng/g dust in offices. PBDEs were detected in all individual and pooled samples of human milk and blood serum and the ΣPBDE and BDE-47 concentrations ranged from 5.5 to 103 and 0.6 to 55 ng/g lipid, respectively. There were no regional differences in concentrations in human milk or blood serum and in general PBDE concentrations were higher in males than in females. Although no temporal trend was apparent in samples of human milk or blood serum collected between 2002 and 2008, the ban on penta- and octa-BDE commercial products in several countries has only been in place since 2004. Hence, effects of the ban may not be reflected in human body burden for several years. The concentrations of PBDEs were found to be highest in young children aged 2 – 5 years of age where concentrations were up to 10 times greater than those detected in adults. Congener profiles for sediment, air, dust and surface wipes were mostly dominated by BDE-209. In human milk and serum, BDE-47 was dominant while BDE-209 contributed only 3% in human milk and was not determined in serum. Concentrations of PBDEs found in Australian human and environmental samples were lower than those reported from North America but higher than those reported from Europe and Asia. The results of modeling and the assessment of matched samples of human milk, indoor air and dust showed that body burden could be partly explained by exposure via food, air, dust and human milk as well as clearance (half-life) data. However, the higher than expected concentrations in young children indicated that there are likely to be missing sources and exposure pathways and/ or the clearance data is inaccurate. The results of this thesis provide baseline data on PBDE concentrations in Australia and will prove important for long term monitoring of the effect of changes in usage rates of these chemicals. It is important to understand the specific sources and exposure pathways of PBDEs in infants and young children in order to identify intervention methods whereby exposure to this vulnerable population can be reduced. In terms of the future use of PBDEs or other flame retardant chemicals, it is important that the risk-benefit ratio is regulated so that the minimization of human exposure and potential associated negative health effects is balanced with the reduction of harm caused by fire.
13

Nové zpomalovače hoření v životním prostředí / New flame retardants in the environment

Ezechiáš, Martin January 2011 (has links)
In the recent years, many research articles focused on endocrine disrupting compounds in the environment. Some of these compounds are listed in a group named brominated flame retardants. However, only few articles investigated endocrine activity of several "new" brominated flame retardants. These chemicals such as 1,2-bis(2,4,6-tribromophenoxy)ethane (BTBPE) or bis(2-ethylhexyl) tetrabromophthalate (TBPH) are newly used due to ban of some previously most produced brominated flame retardant mixes. In this study, we used two recombinant yeast screens to measure estrogenic, androgenic, antiestrognic and antiandrogenic activities of some alternative brominated flame retardants. We also used ligninolytic fungi to investigate biodegradation of these compounds. Our results suggest, that 2,4,6-tribromophenol (TBP) may be a new environmental endocrine disruptor. This substance showed antiestrogenic and antiandrogenic activity in our tests. 1,2-bis(2,4,6- tribromophenoxy)ethane (BTBPE) had certain antagonistic activity too. In the biodegradation experiment, only three compounds showed significant degradation during the test period. No biodegradation have been observed for other compounds. In this study, we applied gas chromatography with mass spectrometry to analyze these "new" flame retardants. Method for gas...
14

Neonatal Developmental Neurotoxicity of Brominated Flame Retardants, the Polybrominated Diphenyl Ethers (PBDEs)

Viberg, Henrik January 2004 (has links)
<p>This thesis examines developmental neurotoxic effects of polybrominated diphenyl ethers (PBDEs), PBDE 99, PBDE 153, and the fully brominated PBDE 209, after exposure during the newborn period in rodents.</p><p>Our environment contains vast numbers of contaminants, including the flame retardants, PBDEs. The PBDEs are widely found in the environment and are increasing in human milk. Individuals can be exposed to PBDEs during their whole lifetime, and especially during the lactation period. The neonatal period, coinciding with the lactation period, is characterized in many mammalian species by rapid growth and development of the immature brain. It has been shown that numerous toxicants can induce permanent disorders in brain function when administered to the neonatal mouse during the brain growth spurt (BGS). In mice and rats this period is postnatal, spanning over the first 3-4 weeks of life, while in humans, BGS begins during the third trimester of pregnancy and continues throughout the first two years of life.</p><p>The present studies identified a defined critical period during BGS in mice when the brain is vulnerable to insults of low doses of PBDEs and that it is the presence of PBDEs or their metabolites in the brain during this critical period that is crucial to evoking neurotoxic effects. The effects observed are permanent altered spontaneous behavior, reduced habituation, deficits in learning and memory, and disturbances in the cholinergic system. These effects worsen with age.</p><p>The ability of PBDEs to induce neurotoxic effects does not appear to be gender-, strain- or species-specific, because the neurotoxic effects are induced in rats and male and female mice of different strains.</p><p>The developmental neurotoxic effects of PBDEs are similar to those observed for polychlorinated biphenyls (PCBs) and possible interactive effects of PBDEs and other environmental contaminants are therefore of concern.</p>
15

Neonatal Developmental Neurotoxicity of Brominated Flame Retardants, the Polybrominated Diphenyl Ethers (PBDEs)

Viberg, Henrik January 2004 (has links)
This thesis examines developmental neurotoxic effects of polybrominated diphenyl ethers (PBDEs), PBDE 99, PBDE 153, and the fully brominated PBDE 209, after exposure during the newborn period in rodents. Our environment contains vast numbers of contaminants, including the flame retardants, PBDEs. The PBDEs are widely found in the environment and are increasing in human milk. Individuals can be exposed to PBDEs during their whole lifetime, and especially during the lactation period. The neonatal period, coinciding with the lactation period, is characterized in many mammalian species by rapid growth and development of the immature brain. It has been shown that numerous toxicants can induce permanent disorders in brain function when administered to the neonatal mouse during the brain growth spurt (BGS). In mice and rats this period is postnatal, spanning over the first 3-4 weeks of life, while in humans, BGS begins during the third trimester of pregnancy and continues throughout the first two years of life. The present studies identified a defined critical period during BGS in mice when the brain is vulnerable to insults of low doses of PBDEs and that it is the presence of PBDEs or their metabolites in the brain during this critical period that is crucial to evoking neurotoxic effects. The effects observed are permanent altered spontaneous behavior, reduced habituation, deficits in learning and memory, and disturbances in the cholinergic system. These effects worsen with age. The ability of PBDEs to induce neurotoxic effects does not appear to be gender-, strain- or species-specific, because the neurotoxic effects are induced in rats and male and female mice of different strains. The developmental neurotoxic effects of PBDEs are similar to those observed for polychlorinated biphenyls (PCBs) and possible interactive effects of PBDEs and other environmental contaminants are therefore of concern.
16

Fate of polybrominated diphenyl ethers during wastewater treatment process producing reclaimed water

Siegel, Kristy 01 January 2013 (has links)
Polybrominated diphenyl ethers (PBDEs), flame retardants, have been applied to consumer goods, such as furniture, electrical devices, textiles, and appliances for decades. Due to their physico-chemical properties, PBDEs are semi-volatile and easily leach off the consumer good during aging, stress, or normal wear and tear of the good. Once airborne, they pose an environmental health threat because they can adsorb onto dust particles, soil, or other particulates that can be inhaled, ingested, or come into contact with the dermal layer. Additionally, PBDEs have a molecular structure similar to other persistent organic pollutants, such as polychlorinated biphenyls and polychlorinated dibenzo-p-dioxins and furans. They are a health threat due to their endocrine-disrupting nature by affecting thyroid functioning, fertility, and child development. The purpose of the study is to measure selected PBDEs in a wastewater treatment plant (WWTP) that produces reclaimed water, such that a mass balance can be completed, and to compare this mass balance with theoretically expected concentrations. The mass balance includes the collection of samples from wastewater, sewage sludge, and air at points within the WWTP. The PBDEs examined are BDE-28, 47, 99, 100, 153, 154, and 183. The second part of the study will compare effluent concentrations to reclaimed water concentrations in order to examine the potential exposure (if any) of using reclaimed water. Influent concentration of mean (sum7)PBDE was found to be 49,117 pg/L and effluent concentration was 4,603 pg/L, illustrating a 91% removal rate of PBDEs during the wastewater treatment plant. Sludge samples contained the highest total concentrations of PBDEs with mean (sum7)PBDE ranging from 14.0 to 41.3 ug/kg dry weight. Air samples were highest at the post-aeration (248 pg/m3 mean (sum7)PBDE) step due to the use of highly oxygenated air assisting in the release and volatilization of the PBDEs. Sludge was found to carry the largest mass loading at 14.2 lb/day (sum7)PBDE. Of the total mass loading of PBDEs from the WWTP, sludge is responsible for 86.7%, followed by reclaimed water and effluent (11.7% and 1.6%, respectively). The mass loading from air was negligible with less than 0.01% contribution to the total mass loading. Whereas reclaimed water overall had higher PBDE congener mean concentrations than the effluent, the independent samples t-test found no statistically significant differences between the two groups. The results of this study can be used to improve the wastewater treatment process to reduce the impact of PBDEs being released into the environment by WWTPs, and to educate the public on utilizing reclaimed water in a safe and healthy manner.
17

Investigating the Use of Hair to Assess Polybrominated Diphenyl Ether (PBDE) Exposure Retrospectively, and in Male Infants with Genitourinary Tract Malformations

Carnevale, Amanda 11 July 2013 (has links)
Polybrominated diphenyl ethers (PBDEs) are synthetic chemicals that are added to a variety of consumer products as flame-retardants. The ubiquitous nature and endocrine disrupting properties of PBDEs are a public concern. A pilot study was performed to investigate whether in utero PBDE exposure, as measured in maternal hair, is associated with genitourinary tract malformations in male infants. In addition, we compared PBDE levels in maternal and infant hair and used segmental analysis to investigate how PBDEs varied along the shaft. Preliminary results suggest a trend toward an elevated PBDE body burden in mothers whose infants were born with genitourinary tract malformations; this was significant for some PBDEs. The sum of PBDEs (ΣPBDEs) in maternal hair did not correlate with infant hair levels; children had significantly greater levels. A significant increase in the ΣPBDEs was observed in distal hair suggesting hair PBDEs may be reflective of both internal and external exposure.
18

Polybrominated Diphenyl Ethers: Soil Sorption and Microbial Degradation

WELSH, GWENDOLYN L. 23 September 2008 (has links)
No description available.
19

Photodégradation des retardateurs de flamme bromés dans des matériaux textiles et plastiques / Photodegradation of brominated flame retardants in textile and plastic materials

Khaled, Amina 02 October 2018 (has links)
Ces travaux de thèse portent sur la photodégradation de retardateurs de flamme bromés  (RFB) : décabromodiphényléther (BDE -209), tétrabromobisphénol A (TBBPA), TBBPA bis (allyl) éther (TBBPA-BAE) et TBBPA bis (2,3-dibromopropyl) éther (TBBPA- DBPE) en milieu solide et dans des échantillons réels. Nous avons d’abord caractérisé par chromatographie en phase liquide-haute résolution couplée à la spectrométrie de masse (LC-HR-MS) le BDE-209 et ses produits de dégradation dans des échantillons de textiles issus de sièges auto des véhicules hors usage (VHUs) des années 90. Puis, nous avons mené des expériences prouvant que ces produits de dégradation étaient d’origine photochimique. Dans un deuxième temps, nous avons étudié l’effet du polystyrène sur la photodégradation du BDE-209, TBBPA et ses dérivés et l’effet de ces RFBs sur la photodégradation du polystyrène. Des analyses par différentes techniques spectroscopiques et chromatographiques (IR, ATR-FTIR, GC-MS, SEC) ont mis en évidence un net effet d’accélération réciproque. La SEC (chromatographie d’exclusion stérique) a révélé une augmentation drastique des coupures de chaîne du PS avec fragmentation. En outre, des photoproduits résultant de l'oxydation du PS et de sa bromation par Br· ont été observés pour la première fois. L’existence de ces sous-produits suggère un nouveau mécanisme de transformation de PS en présence de RFB. Certains de ces photoproduits migrent dans l’eau et l’air, pouvant causer une pollution environnementale. / The main objective of this PhD thesis was to evaluate the photodegradation of brominated flame retardants (BFRs): decabromodiphenyl ether (BDE-209), tetrabromobisphenol A (TBBPA), TBBPA bis (allyl) ether (TBBPA-BAE) and TBBPA bis(2,3-dibromopropyl) ether (TBBPA-DBPE) in solid medium and real samples. As a first step, we characterized by liquid chromatography high-resolution-mass spectrometry (LC-HR-MS) the BDE-209 and its degradation products in textile samples from car seats of end-of-life vehicles (ELVs) of the 1990s. Then we demonstrated that these products were formed by photodegradation. In a second step, we investigated the effect of polystyrene on the photodegradation of BDE-209, TBBPA and its derivatives and the effect of these RFBs on the photodegradation of polystyrene. Analyses carried out by chromatography and spectroscopy techniques (IR, ATR-FTIR, GC-MS, SEC) revealed significant and mutual acceleration effects. SEC (exclusion size chromatography) showed a drastic increase in chain breaks of PS. Morover, additional photoproducts that may result from PS oxidation and Br • bromination has been observed for the first time. The formation of these byproducts suggests a new PS transformation mechanism in the presence of BFR. Some of these photoproducts can migrate into water and air causing environmental pollution.
20

Analytical strategies for the quality assessment of recycled high-impact polystyrene (HIPS)

Vilaplana Domingo, Francisco Javier 30 May 2008 (has links)
Polymers are subjected to physical and chemical changes during their processing, service life, and further recovery, and they may also interact with impurities that can alter their composition. These changes substantially modify the stabilisation mechanisms and mechanical properties of recycled polymers. The assessment of the quality properties of recycled polymers is therefore crucial to guarantee the performance of recyclates in further applications. Three key quality properties have been defined for this quality analysis: degree of mixing (composition), degree of degradation, and presence of low molecular weight compounds (degradation products, contaminants, additives). Furthermore, detailed knowledge about how the different stages of their life cycle affect the degree of degradation of polymeric materials is important when discussing their further waste recovery possibilities and the performance of recycled plastics. A dual-pronged experimental approach employing multiple processing and thermo-oxidation has been proposed to model the life cycle of recycled high-impact polystyrene (HIPS used in packaging applications, and electrical and electronic equipment (E&E). Both reprocessing and thermo-oxidative degradation are responsible for coexistent physical and chemical effects (chain scission, crosslinking, apparition of oxidative moieties, polymeric chain rearrangements, and physical ageing) on the microstructure and morphology of polybutadiene (PB) and polystyrene (PS) phases; these effects ultimately influence the long-term stability, and the rheological and mechanical behaviour of HIPS. The PB phase has proved to be the initiation point of HIPS degradation throughout the life cycle. Thermo-oxidation seems to have more severe effects on HIPS properties; therefore, it can be concluded that previous service life may be the part of the life cycle with the greatest influence on the recycling possibilities and performance of HIPS recyclates in second-market applicat / Vilaplana Domingo, FJ. (2008). Analytical strategies for the quality assessment of recycled high-impact polystyrene (HIPS) [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/2186 / Palancia

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