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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.
61

Fate of trace organic priority pollutants in an enriched continuous culture system

Wei, Lian-Pang 12 1900 (has links)
No description available.
62

Survival and activity of genetically engineered degradative inocula in soil

Mashreghi, Mansour January 1999 (has links)
In this study bioluminescence-marker systems were used to investigate the fate of two genetically engineered degradative bacteria in soil under different conditions. These bacteria were chromosomally <I>lux-</I>marked <I>Alcaligenes eutrophus </I>H850 Lr with <I>lux</I>AB genes which was able to degrade polychlorinated biphenyls (PCBs), and <I>Pseudomonas stutzeri </I>P16. <I>P. stutzeri </I>P16 was genetically marked with the <I>lux</I>AB <I>tet</I> cassette by insertional mutagenesis using mini Tn5-transposons and was characterised for <I>lux</I> gene stability, phenanthrene degradability and sensitivity to aldehyde. Insertion of <I>lux</I> gene into genome of <I>P. stutzeri</I> P16 provided a novel strain with lower maximum specific growth rate and less sensitivity to high concentrations of phenanthrene in liquid culture. Survival and activity of <I>P. stutzeri</I> P16 <I>lux</I>AB4 was further investigated in soil amended with low and high concentrations of phenanthrene. Initially high concentrations of phenanthrene had a less toxic effect on viable cell concentrations and luminescence activity of genetically engineered <I>P. stutzeri</I> P16 comparing with its wild type showing that <I>lux</I>-marking the above degradative strain made the marked strain more suitable for environmental application in heavily polluted sites. However, resistant cells to high concentration of phenanthrene were not able to survive longer than those which was inoculated to microcosms with lower concentrations of phenanthrene. This indicates that toxicity of the target compound and its concentration have to be considered before releasing the GEMs. Degradation of phenanthrene was enhanced in both sterile and non-sterile soil inoculated with <I>P. stutzeri </I>P16 <I>lux</I>AB4. This study could be used as model for further investigated of degradation of other PAHs such as fluoranthene, benz[a]anthracene, benzo[a]pyrene, by degradative bacteria and also monitoring the survival and activity of those bacteria in the environment using bioluminescence-marker systems.
63

Sample preparation in environmental organic analysis

Barnabas, Ian Joseph January 1996 (has links)
No description available.
64

Assessment of the effects of UV-B in marine macroalgae : potential biomarkers of exposure and effect

Cordi, Britt January 1999 (has links)
Studies were undertaken to investigate the suitability of several molecular and physiological responses as biomarkers of UV-B exposure in several marine macroalgal species. Investigations into the sensitivity of mature plants and the reproductive unicells were also carried out. Furthermore, experiments were conducted to determine the interaction between UV-B radiation and the antifouling compound Irgarol 1051 in both a fouling alga and two non-target algal species. Chlorophyll fluorescence, in vivo thallus absorptance and ion leakage were investigated for their suitability as physiological biomarkers of UV -B exposure in the intertidal alga Enteromorpha intestinalis and the subtidal alga Palmaria palmata. DNA damage (measured by Random Amplification Polymorphic DNA fingerprinting, RAPD) and the cellular stress response (measured by induction of the heat shock 70 protein, HSP 70) were evaluated as molecular biomarkers of UV-B exposure. Measurements of thallus growth were used as a measure of adverse biological effects. Fv/Fm ratio showed potential as a sensitive, nonspecific general biomarker of UV-B exposure in both E. intestinalis and P. palmata. In vivo absorptance at wavelengths corresponding to chlorophyll a, phycoerythrin and/or carotenoids, as well as phycoerythrobilin and phycocyanin decreased in a dose-response dependent manner with UV-B exposure. These changes were associated with decreases in growth rate in P. palmata. The RAPD technique used for measuring DNA damage, showed potential as a tool for assessing UV -induced toxicity. These results illustrated that utilising several responses from different levels of biological organisation offer greater possibilities for detecting UV-B induced effects than do single responses. Experiments with 12 h old reproductive unicells of E. intestinalis demonstrated that asexual zoospores were up to 6 times more sensitive to UV-B exposure than mature thalli (measured as variable fluorescence). After 1 hour exposure to elevated UV-B (equivalent to 27% ozone depletion) reproductive unicells experienced decreases in variable fluorescence, accompanied by a 50 % inhibition of germination success and 16.4 % reduction in growth rates. Moreover, consistent patterns of greater sensitivity in the sexual reproductive part of the life cycle compared to the asexual part of the life cycle emerged throughout the experiments. The interactive relationship between UV-B radiation and the s-triazine Irgarol 1051 was investigated in multi-factorial experiments. Inhibitions in optimal quantum yield of approximately 20% were found after exposure to UV-B or Irgarol 1051 (applied singly). When these two stressors were applied simultaneously, however, an additive effect resulting in further reductions of up to 19.6 % compared to a single treatment occurred. These decreases in Fv/Fm were accompanied by up to a 38.5 % reduction in growth rates. Simultaneous exposure of the same stressors to two non-target macroalgae, P. palmata and P. umbilicalis, revealed that these algae were less sensitive to Irgarol 1051 compared to E. intestinalis. However, similar additive effects measured as reductions in both Fv/Fm ratio and growth rates occurred after simultaneous exposure. These results underline the importance of investigating combination effects between UV-B radiation and xenobiotic compounds, if an under-estimation of the ecological implications of elevated UV-B exposure in the marine environment is to be avoided.
65

Cytochrome P4501A Induction by Highly Purified Hexachlorobenzene in Primary Cultures of Avian Hepatocytes

Mundy, Lukas 05 October 2011 (has links)
Hexachlorobenzene (HCB) is a persistent organic pollutant that was primarily produced for use as a fungicide dating back to the 1940s. Worldwide emissions have declined steadily over the past forty years, but HCB is still produced as a by-product of a number of industrial processes and is still detected in remote locations around the globe. Many studies have been conducted to determine the toxic and biochemical effects of HCB, but it has been suggested that reported toxic and biochemical effects initially attributed to HCB exposure may have actually been elicited by contamination of HCB by polychlororinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and dioxin-like polychlorinated biphenyls (PCBs). This thesis investigates whether highly purified HCB (HCB-P; defined as HCB containing < 0.2 ppb of any PCDD, PCDF, or co-planar PCB congener [the detection limit of current analytical methods]) can induce cytochrome P4501A (CYP1A) in three avian species in vitro. Primary cultures of chicken (Gallus gallus domesticus), ring-necked pheasant (Phasianus colchicus) and Japanese quail (Corturnix japonica) embryo hepatocytes were used to compare the potencies of reagent-grade (RG-HCB), HCB-P and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) as inducers of ethoxyresorufin O-deethylase (EROD) activity, CYP1A4 messenger ribonucleic acid (mRNA) and CYP1A5 mRNA. The potencies of two mono-ortho substituted PCBs, 2,3,3’,4,4’-pentachlorobiphenyl (PCB 105) and 2,3’,4,4’,5-pentachlorobiphenyl (PCB 118) were also assessed in chicken embryo hepatocytes using the same endpoints. All compounds induced EROD activity and up-regulated CYP1A4/5 mRNAs in the hepatocytes of each species. The potency of HCB relative to the potency of TCDD (ReP) was 0.0001, 0.001 and 0.01 in chicken, ring-necked pheasant and Japanese quail embryo hepatocytes, respectively. ECthreshold values were suggested to be more appropriate than EC50 values because ECthreshold values account for differences in maximal EROD and CYP1A4/5 mRNA levels that are observed with HCB exposure in avian embryo hepatocytes more so than EC50 values. Differences in species sensitivity to HCB were also assessed, and did not vary as greatly as the listed ReP values. The results presented herein suggest that HCB is capable of inducing effects downstream of activation of the aryl hydrocarbon receptor, and may warrant its inclusion in the World Health Organization’s toxic equivalency concept.
66

Distributions of polychlorinated biphenyls (PCB's), hydrocarbons and fatty acids among sedimentary organic matter fractions

Beller, Harry R. 07 June 1985 (has links)
Graduation date: 1986
67

Levels of pollutants on the surfaces of children's playgrounds situated in public parks

Mostert, Maria M. R. January 2008 (has links)
Small children have been shown to be vulnerable to environmental contaminants, because of their developing nervous systems and small body size. Children may be exposed to environmental contaminants both indoors and outdoors. They are also more likely to ingestion of such pollutants because of the proximity to the pollutants to the surface, their hand-to-mouth behaviour and their tendency to eat soil. The aim of this study was to determine to which degree children may be exposed to pollutants in their outdoor playing areas. Most small children in urban areas spend their outdoor playing time in playgrounds situated in public parks. This study therefore investigated the level of pollutants in 50 playgrounds of public parks from two urban areas in south-east Queensland. The chemicals of interest were both heavy and light metals and polycyclic aromatic hydrocarbons (PAHs), which are known to be detrimental to human health. This is the first study of its kind in Queensland and the first to investigate both metals and PAHs in Australia.. All of the playgrounds investigated contained both metals and PAHs, but none of these exceeded threshold values as determined by the Queensland Department of Health. The highest concentrations of the chemicals were found in the finest particles contained in the playground covers. Moisture played an important role in limiting the concentration of chemicals. More moisture was generally associated with lower concentrations of chemicals. The natural background contributed most of the metals, while most of the PAHs derived from various types of vehicular emissions through atmospheric deposition. Exposure levels for small children were estimated using three different models for calculating the possible exposure equivalent to a recognised reference PAH compound. All estimated values were below threshold exposure levels as provided for under Queensland guidelines. The practice of covering the playground surfaces with fresh bark chips was found to limit the concentrations of metals in playground covers. It is recommended that the practice of covering playground surfaces with bark be continued, and that, further, these surfaces should regularly be sprayed with water, especially in dry areas.
68

Methods for the rapid gelation of liquids /

Markovic, Novica (Nov) Unknown Date (has links)
Thesis (PhDAppliedScience)--University of South Australia, 2003.
69

Characterizing the origin and long-range transport behavior of persistent organic pollutants in the North American atmospheric environment using passive samplers.

Shen, Li. January 2004 (has links)
Thesis (Ph. D.)--University of Toronto, 2004. / Adviser: Frank Wania. Includes bibliographical references (p. 154-163).
70

Chemical exposures, biological monitoring and cancer risks in Swedish aluminium foundries and remelting plants /

Westberg, Håkan, January 2001 (has links) (PDF)
Diss. (sammanfattning) Linköping : Univ., 2001. / Härtill 6 uppsatser.

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