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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.
41

Nanofiber-enabled multi-target passive sampling device for legacy and emerging organic contaminants

Qian, Jiajie 01 August 2018 (has links)
The widespread environmental occurrence of chemical pollutants presents an ongoing threat to human and ecosystem health. This challenge is compounded by the diversity of chemicals used in industry, commerce, agriculture and medicine, which results in a spectrum of potential fates and exposure profiles upon their inevitable release into the environment. This, in turn, confounds risk assessment, where challenges persist in accurate determination of concentrations levels, as well as spatial and temporal distributions, of pollutants in environmental media (e.g., water, air, soil and sediments). Passive sampling technologies continue to gain acceptance as a means for simplifying environmental occurrence studies and, ultimately, improving the quality of chemical risk assessment. Passive samplers rely on the accumulation of a target analyte into a matrix via molecular diffusion, which is driven by the difference in chemical potential between the analyte in the environment and the sampling media (e.g., sorbent phase). After deployment, the target analyte can be extracted from the sampling media and quantified, providing an integrated, time-weighted average pollutant concentration via a cost-effective platform that requires little energy or manpower when compared to active (e.g., grab) sampling approaches. While a promising, maturing technology, however, limitations exist in current commercially available passive samplers; they are typically limited in the types of chemicals that can be targeted effectively, can require long deployment times to accumulate sufficient chemical for analysis, and struggle with charged analytes. In this dissertation, we have designed a next-generation, nanofiber sorbent as a passive sampling device for routine monitoring of both legacy and emerging organic pollutant classes in water and sediment. The polymer nanofiber networks fabricated herein exhibit a high surface area to volume ratio (SA/V values) which shortens the deployment time. Uptake studies of these polymer nanofiber samplers suggest that field deployment could be shortened to less than one day for surface water analysis, effectively operating as an equilibrium passives sampling device, and twenty days for pore water analysis in soil and sediment studies. By comparison, most commercially available passive sampler models generally require at least a month of deployment before comparable analyses may be made. Another highlight of the nanofiber materials produced herein is their broad target application range. We demonstrate that both hydrophobic (e.g., persistent organic pollutants, or POPs, like PCBs and dioxin) and hydrophilic (e.g., emerging pollutant classes including pesticides, pharmaceuticals and personal care products) targets can be rapidly accumulated with our optimal nanofibers formulations. This suggests that one of our devices could potentially replace multiple commercial passive sampling devices, which often exhibit a more limited range of analyte targets. We also present several approaches for tailoring nanofiber physical and chemical properties to specifically target particular high priority pollutant classes (e.g., PFAS). Three promising modification approaches validated herein include: (i) fabricating carbon nanotube-polymer composites to capture polar compounds; (ii) introducing surface-segregating cationic surfactants to target anionic pollutants (e.g., the pesticide 2,4-D and perfluorooctanoic acid or PFOA); and (iii) use of leachable surfactants as porogens to increase nanofiber pore volume and surface area to increase material capacity. Collectively, outcomes of this work will guide the future development of next generation passive samplers by establishing broadly generalizable structure-activity relationships. All told, we present data related to the influence on the rate and extent of pollutant uptake in polymer nanofiber matrices as a function of both physical (specific surface area, pore volume, and diameter) and chemical (e.g., bulk and surface composition, nanofiber wettability, surface charge) nanofiber properties. We also present modeling results describing sampler operation that can be used to assess and predict passive sampler performance prior to field deployment. The electrospun nanofiber mats (ENMs) developed as passive sampling devices herein provide greater functionality and allow for customizable products for application to a wide range of chemical diverse organic pollutants. Combined with advances in and expansion of the nanotechnology sector, we envision this product could be made commercially available so as to expand the use and improve the performance of passive sampling technologies in environmental monitoring studies.
42

Fotocatálise heterogênea aplicada na degradação de poluentes orgânicos utilizando catalisador híbrido de óxido de zinco-xerogel de carbono / Heterogeneous photocatalysis applied to the degradation of organic pollutants using a zinc oxide-carbon xerogel hybrid catalyst

Moraes, Nícolas Perciani de 01 February 2019 (has links)
Foi explorado o desenvolvimento de fotocatalisadores híbridos ZnO/Xerogel de carbono, visando aumentar a eficiência quântica do processo de degradação de poluentes orgânicos persistentes. Especificamente, foi estudada a preparação do híbrido ZnO-xerogel de carbono, sendo esta, a maior inovação tecnológica deste projeto, considerando que o efeito catalítico deste híbrido não foi estudado na literatura. O uso do xerogel de carbono na preparação do semicondutor-material carbonoso é justificado pela excelente condutividade elétrica, elevada área superficial e porosidade, além de sua estrutura porosa ser facilmente manipulada por modificações nos parâmetros de síntese. A escolha do tanino como precursor do xerogel visa à diminuição de custos e impactos ambientais, além de acrescentar valor à inovação tecnológica proposta. A influência do pH e rota de síntese foram avaliados, assim como a influência da temperatura de calcinação nas propriedades dos materiais. A espectroscopia por refletância difusa foi a técnica empregada para determinação da energia de gap das amostras. A morfologia, a análise elementar, a estrutura cristalina dos materiais, a estrutura química e a constituição dos materiais foram determinadas por microscopia eletrônica de varredura, espectrometria de energia dispersiva, difratometria de raios X, infravermelho e espectroscopia Raman, respectivamente. O balanço de cargas na superfície do material foi analisado pela metodologia do ponto de carga zero (PZC). A ação fotocatalítica do material foi avaliada através da decomposição de 4-clorofenol e bisfenol A, determinada através da espectroscopia no UV-Visível. Todos os materiais apresentam a estrutura cristalina hexagonal do óxido de zinco (wurtzita). Os materiais sem tanino em sua composição também apresentam a fase de hidroxicloreto de zinco mono-hidratado. Os difratogramas de raios-X e valores de bandgap obtidos confirmam a incorporação do carbono na estrutura cristalina do óxido de zinco. Os materiais produzidos via rota alcoólica apresentam menores valores de tamanho de cristalito e partícula, assim como um maior teor de grafite em sua composição e maior área superficial, enquanto que os materiais produzidos em solução aquosa apresentam menores valores de energia de gap. Todos os materiais apresentaram atividade fotocatalítica quando submetidos à radiação solar e visível, sendo que os materiais com proporções intermediárias entre xerogel de carbono e óxido de zinco se mostraram superiores para o processo de fotodegradação. Os materiais produzidos via alcoólica são superiores aos produzidos em solução aquosa, no que tange o processo de fotocatálise. Os valores máximos encontrados para a degradação de 4-clorofenol e bisfenol A foram de 88% e 78%, respectivamente, obtidos pelo material XZnC 3.0 (EtOH). A temperatura de calcinação e quantidade de hidróxido de potássio utilizados na síntese influenciam significativamente as propriedades dos materiais, de modo que as condições ótimas para a síntese dos materiais foram de calcinação em 300oC e 8 g de hidróxido de potássio utilizadas na síntese. O mecanismo de fotocatálise é fortemente influenciado pela geração de radicais hidroxilas e os materiais apresentam estabilidade para reciclo em processos industriais. / The development of ZnO/Carbon xerogel hybrid photocatalysts was studied, in order to increase the quantum efficiency of the degradation process of persistent organic pollutants. Specifically, the preparation of the ZnO-carbon xerogel hybrid was studied, being this the most significant technological innovation of this project, considering that the catalytic effect of this hybrid was not studied in the literature. The use of carbon xerogel in the preparation of the semiconductor-carbonaceous material is justified by its excellent electrical conductivity, high surface area and porosity, the latter being easily manipulated by modifications in the synthesis parameters. The choice of tannin as the precursor of the xerogel aims at reducing costs and environmental impacts, adding value to the proposed technological innovation. The influence of the pH and route of synthesis were evaluated, as well as the influence of the calcination temperature on the properties of the materials. Diffuse reflectance spectroscopy was the technique used to determine the gap energy of the samples. The morphology, elemental analysis, crystalline and chemical structure of the materials were determined by scanning electron microscopy, dispersive energy spectrometry, X-ray diffractometry, infrared and Raman spectroscopy, respectively. The charge balance on the material surface was analyzed by the point of zero charge methodology (PZC). The photocatalytic action of the material was evaluated by the decomposition of 4-chlorophenol and bisphenol A, determined by UV-Visible spectroscopy. All materials have the hexagonal crystalline structure of zinc oxide (wurtzite). The materials without tannin in their composition also present the zinc hydroxychloride monohydrate phase. The X-ray diffractograms and bandgap values obtained confirm the incorporation of the carbon in the crystalline structure of the zinc oxide. The materials produced via the alcohol route have lower values of crystallite and particle size, as well as a higher content of graphite in their composition and larger surface area, while the materials produced in aqueous solution have lower values of gap energy. All the materials presented photocatalytic activity when subjected to visible and solar radiation, and the materials with intermediate proportions between carbon xerogel and zinc oxide were superior for the photodegradation process. The materials produced via alcohol route are superior to those produced in aqueous solution, as far as the photocatalysis process is concerned. The maximum values found for the degradation of 4-chlorophenol and bisphenol A were 88% and 78%, respectively, obtained by the material XZnC 3.0 (EtOH). The calcination temperature and amount of potassium hydroxide used in the synthesis significantly influence the properties of the materials, so that the optimum conditions for the synthesis of the materials were calcination at 300 °C and 8 g of potassium hydroxide used in the synthesis. The mechanism of photocatalysis is strongly influenced by the generation of hydroxyl radicals and the materials present stability for recycling in industrial processes.
43

Circulating levels of persistent organic pollutants (POPs) are associated with left ventricular systolic and diastolic dysfunction in the elderly

Lind, Ylva Sjoberg, Lind, Monica, Salihovic, Samira, van Bavel, Bert, Lind, Lars January 2013 (has links)
Background and objective: Major risk factors for congestive heart failure (CHF) are myocardial infarction, hypertension, diabetes, atrial fibrillation, smoking, left ventricular hypertrophy (LVH) and obesity. However, since these risk factors only explain part of the risk of CHF, we investigated whether persistent organic pollutants (POPs) might also play a role. Methods: In the Prospective Investigation of the Vasculature in Uppsala Seniors (PIVUS) study, left ventricular ejection fraction, (EF), E/A-ratio and isovolumic relaxation time (IVRT), were determined by echocardiography and serum samples of 21 POPs were analyzed in serum measured by high-resolution chromatography coupled to high-resolution mass spectrometry (HRGC/HRMS) in 998 subjects all aged 70 years. Results: In this cross-sectional analysis, high levels of several of the polychlorinated biphenyls (PCB congeners 99, 118, 105, 138, 153, and 180) and octachlorodibenzo-p-dioxin (OCDD) were significantly related to a decreased EF. Some POPs were also related to a decreased E/A-ratio (PCBs 206 and 209). All the results were adjusted for gender, hypertension, diabetes, smoking, LVH and BMI, and subjects with myocardial infarction or atrial fibrillation were excluded from the analysis. Conclusions: Circulating levels of POPs were related to impairments in both left ventricular systolic and diastolic function independently of major congestive heart failure risk factors, suggesting a possible role of POPs in heart failure.
44

Air-Surface Exchange of Persistent Organic Pollutants in North America

Wong, Fiona 18 January 2012 (has links)
This thesis examines the air-soil and air-water gas exchange of persistent organic pollutants (POPs) with emphasis on organochlorine pesticides (OCPs). The current status of net exchange, factors which influence the exchange process, and different approaches used to estimate the surface exchange were explored. The net exchange of chemicals was evaluated using the fugacity approach, with the aid of chemical tracers (congener profiles of complex mixtures and enantiomer proportions of chiral chemicals) to infer current use vs. legacy sources to the atmosphere. DDT in southern Mexico was undergoing net deposition from air to soil. Occurrence of fresher DDT residues in the south was indicated by a higher proportion of p,p’-DDT relative to p,p’-DDE and racemic o,p’-DDT in air and soils. Congener profiles of toxaphene suggested soil emissions as the source to air. The influence of chemical aging on soil-air exchange and bioaccessibility was studied in a high organic soil. The use of nonexhaustive extraction with hydroxypropyl-beta-cyclodextrin (HPCD) to predict bioaccessibility was optimized for OCPs and polychlorinated biphenyls (PCBs). Reduced volatility of spiked chemicals correlated with reduced HPCD extractability for soil that had been aged under indoor and outdoor conditions for 730 d and infers volatility could be used as a surrogate for bioaccessibility. Measured soil-air partition coefficients (Ksa) were lower than those predicted from the Karickhoff relationship, which considers octanol as a surrogate for soil organic matter. The role of soil moisture, organic carbon, temperature, depth of soil surface horizon and dissolved organic carbon in the fate of organic contaminants in soil were assessed using chemical partitioning space maps. These maps allow instant visual prediction of the phase distribution and transport process of a chemical among the three major phases in soil; i.e., air, water and solid. Net volatilization of alpha-hexachlorocyclohexane from water to air was found in the southern Beaufort Sea using fugacity calculations and flux measurements. The influence of ice cover on volatilization was indicated by a winter-summer shift from racemic to nonracemic alpha-HCH in boundary layer air.
45

Air-Surface Exchange of Persistent Organic Pollutants in North America

Wong, Fiona 18 January 2012 (has links)
This thesis examines the air-soil and air-water gas exchange of persistent organic pollutants (POPs) with emphasis on organochlorine pesticides (OCPs). The current status of net exchange, factors which influence the exchange process, and different approaches used to estimate the surface exchange were explored. The net exchange of chemicals was evaluated using the fugacity approach, with the aid of chemical tracers (congener profiles of complex mixtures and enantiomer proportions of chiral chemicals) to infer current use vs. legacy sources to the atmosphere. DDT in southern Mexico was undergoing net deposition from air to soil. Occurrence of fresher DDT residues in the south was indicated by a higher proportion of p,p’-DDT relative to p,p’-DDE and racemic o,p’-DDT in air and soils. Congener profiles of toxaphene suggested soil emissions as the source to air. The influence of chemical aging on soil-air exchange and bioaccessibility was studied in a high organic soil. The use of nonexhaustive extraction with hydroxypropyl-beta-cyclodextrin (HPCD) to predict bioaccessibility was optimized for OCPs and polychlorinated biphenyls (PCBs). Reduced volatility of spiked chemicals correlated with reduced HPCD extractability for soil that had been aged under indoor and outdoor conditions for 730 d and infers volatility could be used as a surrogate for bioaccessibility. Measured soil-air partition coefficients (Ksa) were lower than those predicted from the Karickhoff relationship, which considers octanol as a surrogate for soil organic matter. The role of soil moisture, organic carbon, temperature, depth of soil surface horizon and dissolved organic carbon in the fate of organic contaminants in soil were assessed using chemical partitioning space maps. These maps allow instant visual prediction of the phase distribution and transport process of a chemical among the three major phases in soil; i.e., air, water and solid. Net volatilization of alpha-hexachlorocyclohexane from water to air was found in the southern Beaufort Sea using fugacity calculations and flux measurements. The influence of ice cover on volatilization was indicated by a winter-summer shift from racemic to nonracemic alpha-HCH in boundary layer air.
46

Characterising the scale and significance of persistent organic pollutants in South African sediments / Claudine Roos

Roos, Claudine January 2010 (has links)
Water resources in South Africa are scarce, and should therefore be protected against pollutants, also from persistent organic pollutants (POPs). POPs are a global concern due to their ubiquitous presence, persistence and toxicity. This is emphasised by the Stockholm Convention on POPs, which aims at reducing and ultimately eliminating them. South Africa signed and ratified the treaty, and it became international law on 17 May 2004, but there is still a lack of information regarding POPs in South Africa. This study focussed on establishing the levels of POPs and other organic pollutants, which included various organochlorine pesticides (OCPs), polycyclic aromatic hydrocarbons (PAHs), dioxin-like compounds (DLCs), non-dioxin-like polychlorinated biphenyls (PCBs) and polybrominated diphenyl ether (PBDE). Sampling regions included the industrial cities – Cape Town, Richards Bay, Durban and Bloemfontein, and low-income, high density residential areas surrounding a wetland in Soweto/Lenasia and Botshabelo. Additionally, rivers flowing into neighbouring countries, rivers in the vicinity of paper and pulp producers and high altitude rivers were included. Sediment samples were firstly screened for the presence of DLCs by the H4IIE-luc bio-assay, whereafter sites eliciting quantifiable responses were selected for further chemical analysis by high resolution gas chromatography-high resolution mass spectrometry (HRGC/HRMS). Of the 96 sites, only 23 had quantifiable levels of DLCs. These sites were mainly of industrial, semi-industrial or low-income residential nature. PAHs were the predominant class of compounds at most of the sites, while OCPs and PCBs were present in moderate concentrations and PBDEs in minor concentrations. The concentration of pollutants measured in South African soils and sediments were intermediate when compared to the levels measured in some European, Asian and Scandinavian countries, with the exception of a few sites where exceptionally high levels of compounds were measured. The carbon content normalized concentrations of certain compounds at some of the sites exceeded the Canadian sediment quality guidelines. The estimated cancer risk associated with dermal absorption of OCPs measured in this study was negligible when compared to the background cancer risk expected for South Africans due to life style factors. However, it was estimated that dermal exposure to PCBs, DLCs and PAHs may lead to severe increases in cancer cases, and may seriously impact on human health. / Thesis (Ph.D. (Environmental Science))--North-West University, Potchefstroom Campus, 2011.
47

Characterising the scale and significance of persistent organic pollutants in South African sediments / Claudine Roos

Roos, Claudine January 2010 (has links)
Water resources in South Africa are scarce, and should therefore be protected against pollutants, also from persistent organic pollutants (POPs). POPs are a global concern due to their ubiquitous presence, persistence and toxicity. This is emphasised by the Stockholm Convention on POPs, which aims at reducing and ultimately eliminating them. South Africa signed and ratified the treaty, and it became international law on 17 May 2004, but there is still a lack of information regarding POPs in South Africa. This study focussed on establishing the levels of POPs and other organic pollutants, which included various organochlorine pesticides (OCPs), polycyclic aromatic hydrocarbons (PAHs), dioxin-like compounds (DLCs), non-dioxin-like polychlorinated biphenyls (PCBs) and polybrominated diphenyl ether (PBDE). Sampling regions included the industrial cities – Cape Town, Richards Bay, Durban and Bloemfontein, and low-income, high density residential areas surrounding a wetland in Soweto/Lenasia and Botshabelo. Additionally, rivers flowing into neighbouring countries, rivers in the vicinity of paper and pulp producers and high altitude rivers were included. Sediment samples were firstly screened for the presence of DLCs by the H4IIE-luc bio-assay, whereafter sites eliciting quantifiable responses were selected for further chemical analysis by high resolution gas chromatography-high resolution mass spectrometry (HRGC/HRMS). Of the 96 sites, only 23 had quantifiable levels of DLCs. These sites were mainly of industrial, semi-industrial or low-income residential nature. PAHs were the predominant class of compounds at most of the sites, while OCPs and PCBs were present in moderate concentrations and PBDEs in minor concentrations. The concentration of pollutants measured in South African soils and sediments were intermediate when compared to the levels measured in some European, Asian and Scandinavian countries, with the exception of a few sites where exceptionally high levels of compounds were measured. The carbon content normalized concentrations of certain compounds at some of the sites exceeded the Canadian sediment quality guidelines. The estimated cancer risk associated with dermal absorption of OCPs measured in this study was negligible when compared to the background cancer risk expected for South Africans due to life style factors. However, it was estimated that dermal exposure to PCBs, DLCs and PAHs may lead to severe increases in cancer cases, and may seriously impact on human health. / Thesis (Ph.D. (Environmental Science))--North-West University, Potchefstroom Campus, 2011.
48

Biomagnification and fate of persistent organic pollutants (POPs) in marine mammal food webs in the Northeastern Pacific Ocean

Cullon, Donna Lynn 31 August 2010 (has links)
Elevated polychlorinated biphenyl (PCB) concentrations have been detected in marine mammals inhabiting the Strait of Georgia, British Columbia (Canada) and Puget Sound, Washington State (USA). This raises concerns about adverse health effects and underscores the importance of documenting source, transport, and fate of contaminants. This marine mammal-oriented study- (1) examines dietary exposure to complex mixtures of persistent organic pollutants (POPs); (2) characterizes POP accumulations using congener-specific contaminant analyses, stable isotope ratios, and multivariate statistical methods; and (3) explores some of the influencing factors for POP bioaccumulation in marine mammals. A first application of a food basket approach to assessing real-world dietary exposure to mixtures of chemicals in marine mammals has revealed Puget Sound as a regional “hotspot” for PCB contamination. The consistency between PCB concentrations in Puget Sound and the Strait of Georgia harbour seals (Phoca vitulina) and their food baskets validates the use of this method as a basis for exploring dietary exposure, metabolism, biomagnification, and health risks in marine mammals. Concentration rankings of POPs and estimated daily intakes based on our food baskets suggests that both legacy (e.g., PCB, dichlorodiphenyltrichloroethane [DDT]) and new (polybrominated diphenyl ethers [PBDEs]) POPs may pose potential health risks to seals. Accumulations of PCBs in the Strait of Georgia seal food web demonstrate the bioaccumulative nature and persistence of PCBs. Correlations of PCB concentrations with physicochemical properties and trophic level revealed the important role that metabolism plays in biomagnification in seals, alongside trophic level and log Kow. We estimate a PCB load of 77 kg within the Strait of Georgia biomass, with the largest proportion (36 %) detected in marine mammals. Dietary exposure of POPs to resident killer whales (Orcinus orca) was assessed by measuring POPs in four stocks of chinook salmon (Oncorhynchus tshawytscha), their primary prey. Differences in POP concentrations between chinook smolts and returning adults suggest that the majority of POPs are acquired at sea during the major growth period in their life cycle. Higher POP concentrations and low lipid content were observed among the more southerly stocks suggesting a migration-associated metabolism and loss of lighter congeners, thereby exposing southern residents to more highly contaminated chinook salmon. Consumption on a lipid-weight basis, (higher consumption on a wet weight basis), as well as consuming prey from a more contaminated region, likely increases killer whale exposure to POPs, offering an explanation for higher contaminant burdens in southern residents. While previous research has examined species inhabiting different trophic levels or food chains in other regions, this study has provided an assessment of POP dietary exposure, biomagnification, and influencing factors on trophic accumulations in a North-eastern Pacific marine mammal food web. These results have provided further insight into the influence of such factors as age, sex, lipid content, diet, migration-related metabolism, physicochemical properties (degree of chlorination, log Kow), and chemical structure on POP accumulation in marine mammals. We have identified the largely unregulated PBDEs as posing potential health risks to marine mammals and offered a means to update existing tissue residue guidelines for the protection of wildlife.
49

Distribution and fate of persistent organic pollutants in nearshore marine turtle habitats of Queensland, Australia

Siobhan Hermanussen Unknown Date (has links)
ABSTRACT The tropical and subtropical nearshore marine environments of Queensland, Australia sustain diverse and unique marine wildlife. Continuous population growth and land-use changes along the Queensland coastline are known to exert numerous anthropogenic pressures on these marine ecosystems, including the delivery of high sediment loads. Sediments also provide a transport pathway for persistent organic pollutants (POPs) from rural and urban catchments into the marine environment. While such pollutants are known to be elevated in marine sediment and biota from nearshore areas in Queensland, their input and distribution pathways, as well as exposure and associated risks to wildlife populations are only partially understood. Mounting evidence suggests that POPs may contribute to population declines in marine wildlife species; however, limited information is available regarding the accumulation and effects of these contaminants in endangered or threatened marine turtles. This study aimed to redress some of these information gaps using a case study approach in marine turtle habitats of Moreton Bay, and other embayments in Queensland. Among persistent organic pollutants (POPs), dioxins (polychlorinated dibenzo-p-dioxins; PCDDs) and to some extent also dioxin-like PCBs (polychlorinated biphenyls; PCBs) were found to be widespread and often present at elevated (ppb) levels in surface sediments from Moreton Bay. However, while PCDD/F toxic equivalencies (TEQs) are above international (Canadian) sediment quality guidelines at numerous sites in Moreton Bay, in general TEQs across the Bay are relatively low compared to those from contaminated locations near dense industrial activities. POP contamination in surface sediments across Moreton Bay was investigated by a combination of GIS spatial mapping, geostatistical and traditional statistical modalities. High spatial variability and complex spatial distribution patterns were revealed. High resolution GIS kriging model outputs from the mid to southern Bay facilitated identification of distinct sediment contamination zones, with highest PCB and PCDD/F levels present in nearshore locations, associated with nearby river systems. While primarily governed by organic carbon, a multitude of physical, chemical and hydrological factors were identified to influence the spatial variance of PCDD/F concentrations. The main parameters governing PCDD/F spatial distribution were identified as sediment geochemistry, water depth and anthropogenic alterations of the physical environment and, together, all quantifiable explanatory variables (including hydrodynamic flushing) explained ≈75% of spatial PCDD/F variance. Together, the interaction of these parameters results in complex distribution patterns and highly variable concentrations even among neighbouring sites of 1-3 km resolution. These results suggest that prediction models of POP distributions in the nearshore marine environment may require high-resolution validation, and highlights that the design of low resolution monitoring strategies can have profound impacts on the reliability of contaminant information or any subsequent extrapolations. This knowledge and methodology can be utilised to optimise on-going and future near-shore sediment monitoring programs both locally and in other regions around the world. Using the spatial distributions of dioxin-like contaminants within sediments, this study provided an opportunity to assess field-based relationships between habitat contamination and local marine biota contamination. Detectable levels of PCDD/Fs and dioxin-like PCBs were measured in all green, hawksbill, loggerhead and flatback marine turtle tissues. POP concentrations in sediments were found to significantly correlate with those in the herbivorous green turtle from different sediment contamination zones. These findings demonstrate that sediments represent an important secondary contaminant source and lead to redistribution of POPs to the marine food chain. POP concentrations and TEQs clearly increased from sediment to turtles as well as with increasing trophic levels in marine turtle species. The results from this study demonstrate that the extent of sediment contamination within foraging habitats governs marine turtle exposure, while, trophic status and to some extent age influence contaminant exposure within a particular contamination zone. Despite the relatively low TEQ in sediments from Moreton Bay, TEQ levels in green turtle sub-populations foraging from near-shore locations and higher trophic loggerhead and flatback turtles are similar or elevated compared to those reported for other marine wildlife from Moreton Bay and elsewhere, even compared to higher trophic species from locations impacted by dense industrial activities. High bioaccumulation potential of 2,3,7,8-PCDD/F and dioxin-like PCBs compounds were estimated for green turtles using biota to sediment accumulation factors. Selective accumulation of toxicologically more potent (i.e. lower chlorinated) PCDD/Fs was observed for higher trophic marine turtles, resulting in increasing TEQs for the carnivorous species. Biomagnification was also observed for some non-2,3,7,8-substituted dioxin congeners which typically do not accumulate in most biota. These results are proposed to be due to relatively high accumulation efficiency and/or low metabolic capacity for these POP compounds in marine turtles. These findings are also hypothesised to reflect temperature dependant, greater bioavailability of hydrophobic chemicals in sub-tropical and shallow marine systems. An additional pilot study revealed that in contrast to PCDD/Fs and PCBs, levels of persistent flame retardants (polybrominated diphenyl ethers; PBDEs) were relatively low in marine turtles and other marine species (dugong, fish and shellfish) from Moreton Bay. This suggests relatively low level input of these more recent industrial products into the marine environment. However, as elevated levels of PBDEs have been reported in blood from the general population of Australia, ongoing transport from the terrestrial to the marine system and redistribution of these contaminants, similar to PCDD/F and PCBs, would be expected to occur into the future. Limited information is available regarding the sensitivity of reptiles to and effects of POPs, however, studies have shown that reptiles are sensitive to POPs albeit with uncharacterised relative potency. In the absence of robust toxicological information for reptiles or marine turtles, the potential risks associated with PCDD/F and PCB exposure of Queensland turtle populations was evaluated using toxicity for sensitive biological endpoints observed in mammals and birds. Using probabilistic methodology for marine turtles from Queensland, the body burden of up to 31% and 55% of green and loggerhead turtles, respectively, are above the threshold levels where the most sensitive physiological effects are observed in mammals and birds. While this evaluation illustrates that the contaminants investigated have the potential to impact on the health of marine turtle populations, it must be highlighted that it is compromised by the lack of species-specific (and in this case, class-specific) information, the uncertainty of which is often considered to represent a factor of at least 10. The findings of the present study indicate that exposure to POPs has the potential to adversely affect the health of Queensland’s marine turtle populations, and highlight the need for robust information on reptile specific sensitivity to these compounds.
50

Contaminant dietary exposure assessment for a coastal subpopulation in Queensland, Australia

Veronica Matthews Unknown Date (has links)
Polychlorinated-p-dibenzo dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) (collectively termed ‘dioxins’) and polychlorinated biphenyls (PCBs) are three groups of persistent organic pollutants (POPs) ubiquitous in the environment due to their emission from numerous sources, high persistency and a propensity to be transported long distances. These compounds bioaccumulate in animal tissue, biomagnify through the food web and are toxic to humans and wildlife at relatively low concentrations. Humans may be exposed to POPs via ingestion, inhalation and dermal absorption, however, for the general population, approximately 90% of the total exposure occurs through intake of contaminated food particularly from lipid rich products, including seafood. An Australian national study highlighted that, similar to many other countries, seafood contributes a major proportion to dioxin and PCB exposure of Australians. As typical for national studies, the exposure assessment utilised contaminant concentrations in retail (sea)food and consumption information based on national dietary surveys. The risk assessment showed that the Australian population on the whole has a very low risk of exposure to dioxins through food. However, more than 80% of the Australian population lives within 50 km of the coast, where recreational, cultural and/or subsistence fishing of local seafood is prominent, potentially from areas with elevated PCDD/F and PCB concentrations. Through analysis of local seafood contamination and community seafood consumption patterns, this study assessed PCDD/F and PCB exposure for a coastal subpopulation in Moreton Bay, Queensland who consume locally caught seafood from an area with elevated PCDD/F and PCB concentrations but relatively low (background) toxic equivalency (TEQDP) in sediments, which is typical for Australian nearshore marine systems. Despite low sediment TEQDP levels, due to the dominance of octachlorodibenzo-p-dioxin (which is considered less potent compared to the most toxic 2,3,7,8-tetrachlorodibenzo-p-dioxin), elevated TEQDP concentrations were present in local seafood. In particular higher trophic fish species and some traditional seafood were found to contain TEQDP above current EU action and maximum limits. This highlights the efficiency of species specific contaminant uptake, bioaccumulation and biomagnification processes, which can result in accumulation of higher toxic dioxin and PCB congeners in biota. In contrast, concentrations of most organochlorine pesticides and flame retardants (polybrominated diphenylehters (PBDEs)) were relatively low in seafood from Moreton Bay. For fish, uptake of highly lipophilic contaminants, such as PCDD/Fs and PCBs occurs predominantly via food (biomagnification) and respiratory processes (bioconcentration) followed by selective accumulation of the more toxic, lower chlorinated 2,3,7,8 PCDD/F congeners. This study discovered that physical contact with sediment and dermal absorption of lipophilic contaminants also represents an important exposure pathway for sediment dwelling fish, resulting in higher lipid normalised PCDD/F, PCB and TEQ levels (up to 8, 5 and 3 fold) in skin compared to muscle tissue. PCDD/F and PCB congener profiles differed between muscle and skin suggesting biomagnification and skin absorption as the respective predominant uptake pathways for these tissues. Dermal uptake was estimated to contribute up to 46% to the total TEQDP load on a lipid basis in sediment dwelling fish species, thus representing an important exposure pathway, and extending the bioavailability of sediment-sorbed pollutants to the food web. Accurate determinations of lipid content and lipid TEQDP contamination within seafood samples are critical to human exposure assessments. To ensure quality assurance, different seafood extraction methods were tested to evaluate their impact on lipid yields and contaminant concentration. While levels of PCDD/Fs and PCBs on a lipid basis did not vary across the different methods employed in this study, sample preparation is a significant determinant of lipid yield from fattier fish species. If samples were freeze dried prior to extraction, 30% higher TEQDP values (on a wet weight basis) were obtained as compared to extraction using fresh sample material. Such variance in lipid results will have a significant impact on exposure assessments and should be taken into consideration during seafood contaminant analysis. The median TEQDP concentration from local seafood was approximately 25 fold higher compared to the retail seafood analysed for the national Australian risk assessment. The seafood consumption survey results from this study further indicate that coastal subpopulations consume considerably more seafood than the general population (2 to 6 times more in the present case study). This proved to be an important driver for contaminant exposure in this subpopulation. The average monthly dioxin intake for the coastal community ranged between 34 (best case) to 107 (worst case) pg TEQ kg bw-1 month1, (95th percentile: 114 - 362 pg TEQ kg bw-1 month1), an order of magnitude higher than that estimated for the general population. The contaminant exposure via the local seafood consumption pathway alone exceeded WHO tolerable daily intake levels in 11-44% of the population. These results have important implications with respect to adequate contaminant exposure assessments of Australian and other coastal subpopulations. The study outcomes highlight the importance of considering local conditions and information on contaminant fate processes for human exposure evaluations. Local seafood consumption in coastal communities can result in high exposure to PCDD/F and PCBs, even in background contamination areas. This information would be important to consider for developing future sediment quality guidelines and with respect to exposure and associated risks for coastal communities in general.

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