Thesis (Ph. D.)--University of Washington, 2007. / Vita. Includes bibliographical references (leaves 173-183).

Magister Scientiae - MSc (Biotechnology) / The mining industry in South Africa is of immense importance as this sector contributes largely to the countries income. In the Limpopo province, a large production of antimony (Sb) is generated per year. Antimony (Sb) is a trace element, which accumulates in the environment through anthropogenic activities, such as mining and smelting industries. Antimony is toxic to all living organisms and plants, and it is found to increase the peroxidation of membrane lipids and encourage an antioxidant response. Sb contamination in plants also accounts for DNA damage. The reduction in yield is due to the disruption of plant metabolism by reactive oxygen species (ROS). To combat abiotic stresses, plants have generated a signalling network that utilises multiple growth regulators that would offer protection against the stress. An increase in ROS is one of the responses to abiotic stresses. ROS is generated in response to the pants interaction with heavy metals, through the Harber-Weiss reaction. ROS compounds include: superoxide, hydrogen peroxide and hydroxyl radicals. Under normal conditions ROS molecules are produced as by-products, however, under stressful conditions the production of ROS molecules are increased to levels where they are detrimental to the plants. Therefore, the accumulation of ROS results in damage to proteins, lipids, carbohydrates and DNA which would lead to cellular death. ROS accumulation is thought to be a result of the disruption in the balance of ROS production and the anti-oxidation systems. The antioxidative system is thus introduced to restore the balance of ROS molecule production and to combat oxidative damage caused by the ROS molecules. The anti-oxidative system consists of various enzymes: superoxide dismutase, catalase, and ascorbate peroxidase and glutathione reductase. Each antioxidant scavenges one or two ROS molecules. / 2020-08-31

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No description available.

This thesis describes a study of the remobilisation of heavy metals from sediments by three aminopolycarboxylic acids (APCAs). They are nitrilotriacetic acid, ethylenediaminetetraacetic acid and diethylenetriaminepentaacetic acid. The investigation is introduced by examining the sources, uses and chemistry of these acids. The introduction also includes a discussion of what is known about the inclusion of heavy metals into sediments and their remobilisation from sediments. Typical concentrations of APCAs in natural waters and sediments have been catalogued from the literature. The advantages and disadvantages of various laboratory techniques employed for the remobilisation of heavy metals by APCAs from sediments are assessed, as is the use of such experiments in quantifying the role of APCAs in the remobilisation of heavy metals from sediments. Sediments from three areas were sampled for this study; they were the Alexandra Canal, Captains Flat and Jenolan Caves in New South Wales, Australia. In each area several sites were sampled. For each site there is a brief description of the catchment geology and hydrology. Selected sediment-associated waters in the areas were analysed for their metal concentrations as well as for ultratrace levels of APCAs employing a method developed in the present study. The waters were analysed for the major ions Ca2+, Mg2+, K+, Na+, Cl-, NO3- and SO42-. The sediments from selected sites in each of the areas were dried and fractionated. The dry total and fine sediments were analysed for their metal content and the latter was found to adequately represent the former in this respect. Water samples from the three areas showed different chemistries and exhibited more subtle differences between sites. In general, the Alexandra Canal waters are saline and alkaline and are a mixture of urban runoff and seawater; the Captains Flat waters are acidic and contain high sulfate from acid mine and tailings drainage; the Jenolan Caves waters are neutral and have the features characteristic of waters draining through limestone. The APCA contamination in all water samples when ranked against other global sites is very low. Although the current APCA levels in the waters appear low, it was concluded that they should be closely monitored so that efforts can be made to minimise the risk of APCAs being hazardous environmental contaminants and also that any remobilisation of heavy metals from sediments by APCAs can be controlled. Agitation and column laboratory-scale experiments were carried out in order to obtain an understanding of the remobilisation of metals by contamination levels of APCAs in water, both as the individual APCAs and as a mixture of APCAs. Complimentary experiments were carried out using a molar excess of APCAs calculated from the metal concentrations obtained by acid digestion (assuming 1:1 metal complex formation). Both types of remobilisation experiments were designed to investigate the role that redox potential (Eh) and concentration of APCAs in natural waters have on the remobilisation of heavy metals from the sediments. The agitation experiments were employed to assess metal remobilisation for the situation where the sediments are disturbed while the column experiments explored metal remobilisation for the case where the sediments are left undisturbed in situ. The major conclusions from the agitation experiments that used fine sediment from the Alexandra Canal were that 100 ppm APCA solutions will remobilise metals from the sediments under oxic conditions but only remobilise infinitesimally small amounts of metal under anoxic conditions. The use of fine sediments for the duplicate agitation experiments was found to give adequate duplication of results. A mixture of APCAs in solution acts similarly to the average of the three individual APCA solutions, showing that there are no antagonistic or synergistic effects likely to occur when they are found together in the environment. It was found that the mmoles of the metals remobilised exceeded the mmoles of the APCAs added when 500.0 mL of 100 ppm APCA solution was used on 50.00 g of sediment. This might be due to APCAs remobilising metals from the sediments in ways other than by complexation. Even though an excess of APCAs was available, metal remobilisation was not complete when the experiments were forced to terminate. During the 14 days of the experiment, only one quarter of the metals liberated from the sediment by HNO3 and 30 % H2O2 digestion were remobilised by the APCAs. Therefore an excess of free APCAs remains in solution. Fine sediments from Alexandra Canal, Captains Flat and Jenolan Caves were employed in the oxic agitation experiments using excess APCAs in solution. These experiments resulted in the following major conclusion: when producing an APCA remobilisation signature for trace and ultratrace metals, the geochemistry of the site is of secondary importance to the source of the contaminating metals. This is a feature of the trace and ultratrace metal speciation in the source rather than their concentration in it. From the different levels of calcium present in the three areas it was found that calcium is unlikely to form stable 1:1 APCA complexes at the pH values employed and is unlikely to compete with the heavy metal remobilisation by APCAs. Total sediments from Alexandra Canal and 100 ppm APCA solutions were employed for the column leaching experiments. From mass, pore water volumes and flow measurements it was shown that the ten mini cores taken from the same site were not true replicates. Despite this, when the sediments have settled and the pore waters removed from the cores, the levels of metal being leached stabilise and may represent a clearer picture of the in situ metal leaching from sediment with time. The levels of metal leached from the cores in 14 days suggest that during this period the cores are essentially anoxic, with the oxygen supplied from the oxic leaching solutions used for inorganic and microbial processes in the sediments. Agitation experiments appeared to yield an adequate picture of what would happen if free APCA solution came in contact with fine sediments suspended in the water column. Column leaching experiments employing total sediment were found to be only of limited value in assessing heavy metal remobilisation from undisturbed sediment. These experiments do not give a reliable assessment of the bioavailability of heavy metals and further testing of the acute and chronic toxicity of the sediments is recommended. APCA solutions that have been used in sediment and soil washing under conditions related to those used in the present study may contain an excess of the free APCAs as well as APCA heavy metal complexes and hence may be toxic to biota.

Innovative means and methods were tested to develop an economical, pragmatic and environmentally sustainable soil remediation process for heavy metal contaminated soils. An unsaturated-flow soil washing procedure was devised to dissolve the soil-bound toxic heavy metals; the latter were extracted by a chemical washing solution that percolated through the soil matrix. Subsequently, the leached toxic heavy metals were selectively concentrated, by a chemical precipitation process, into a solid waste. Thereby, a fraction of the spent ethylenediaminetetraacetic acid (EDTA), within the washing and rinsing leachate, was theoretically regenerated and recycle-ready. / The unsaturated-flow washing procedure was perfected by applying different treatments to a soil from a secure landfill. This soil was contaminated with Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, S and Zn. The major contaminants were Fe, Pb, Zn, S, Cu and Mn, making up 25, 1.9, 1.0, 0.4, 0.4 and 0.2%wt of the soil. The extraction responses of the contaminants and those of Al, Ca, Mg and P were established for citric acid (0.5 M) and different molarities of diammonium EDTA ((NH4)2EDTA). The DOW Chemical Company supplied the (NH4)2EDTA (i.e. VERSENE), a 1.37M industrial cleaner, which roughly costs $1.85kg-1 in bulk. The affordability of VERSENE was a pre-condition for hoping to satisfy the economical feasibility of remediating trace metal contaminated soils. / Ultimately, the developed unsaturated-flow washing procedure was tested in a pilot-scale experiment, for its ability to remediate a soil from an abandoned car battery recycling facility. The latter soil was severely contaminated with Pb (3.9%wt). Drip irrigation was used to apply (NH4) 2EDTA and water-rinsing solutions to the surface of soil heaps that rested atop an impermeable barrier, which permitted the retrieval of the leachate. A cumulative EDTA input to the soil of 10.6% wt extracted 49.4% of the total Pb content of the soil. Alternatively, readily biodegradable citric acid barely extracted 2.2% of the total Pb content of the soil, for a cumulative input of 18.1% weight of soil. Different treatments were tested for their effectiveness in concentrating the leached toxic heavy metals into a solid waste. The Pb was best precipitated with Na2S alone, as it provided the most concentrated solid toxic waste. / The environmental sustainability of remediating trace metal contaminated soils was thoroughly examined, as per the amounts of chemical entrants and toxic waste by-products, and per the post-treatment leaching of toxic levels of the remaining and potentially toxic trace metals. (Abstract shortened by UMI.)

A major factor complicating the cleanup at many sites is co-contamination by both organic compounds and heavy metals. Whereas much research has focused on the removal of either organic compounds or metals, relatively few studies have investigated simultaneous removal of organic and inorganic pollutants from soil. / The studies reported in this thesis have evaluated a novel technique for the simultaneous mobilization of polychlorinated biphenyl (PCB) compounds and heavy metals (HMs) from a field contaminated soil. Soil extraction with washing aids {surfactants/cyclodextrin in combination with chelating reagent(s)} was optimized for mobilization efficiency, recovery/recycle of washing additives, and in parallel detoxification of mobilized contaminants. PCB extraction efficiencies were determined with a method that converted all the PCB congeners to dicyclohexyl by hydrogenation over palladium. Studies demonstrated that 10 minutes of ultrasonic mixing of field contaminated soil with a combination of surfactant (30 mL L-1) or cyclodextrin (100 g L-1) and a sparing quantity (2 mmoles) of EDTA, simultaneously mobilized appreciable quantities of PCBs and most analyte metals (Cd, Cu, Mn, Pb, Zn, Ni, Cr). / Relative to individual reagents, combinations of surfactant (Brij 98, Triton X-301, or Triton XQS-20) or cyclodextrin (RAMEB or HPCD) with EDTA did not influence PCB extraction efficiencies perceptibly. The presence of surfactant or cyclodextrin in admixture with EDTA did not appreciably change the efficiency of mobilization of most heavy metals (Al, Cd, Cr, Fe, Mn, Ni, and Zn) but did increase the recovery of Cu and Pb with nonionic surfactant and cyclodextrin. When coupled with PCB removal by hexane back-extraction and precipitation of the HMs (mediated by hydrolysis of zero-valent magnesium (Mg0)}, aqueous washing suspension was regenerated and recycled twice to mobilize more contaminants from the soil. Three sonication-washes with the same charge of reagent mobilized appreciable quantities of PCBs (68 - 83%) and virtually all of the available Cd, Cu, Mn, and Pb and lesser amounts of the Zn (56%), Ni (59%), and Cr (50%) but only small quantities of Al (28%) and Fe (30%). / The release of EDTA from heavy metals complexes was efficient for most metals (99%) but was influenced by the nature of surfactant. EDTA recovery (62-65%) post three cycles of soil washing, hexane back-extraction, and Mg 0 treatment was similar for all reagent combinations. Among surfactants and cyclodextrin, only anionic surfactants suffered losses to Mg0 treatment.

This thesis describes a study of the remobilisation of heavy metals from sediments by three aminopolycarboxylic acids (APCAs). They are nitrilotriacetic acid, ethylenediaminetetraacetic acid and diethylenetriaminepentaacetic acid. The investigation is introduced by examining the sources, uses and chemistry of these acids. The introduction also includes a discussion of what is known about the inclusion of heavy metals into sediments and their remobilisation from sediments. Typical concentrations of APCAs in natural waters and sediments have been catalogued from the literature. The advantages and disadvantages of various laboratory techniques employed for the remobilisation of heavy metals by APCAs from sediments are assessed, as is the use of such experiments in quantifying the role of APCAs in the remobilisation of heavy metals from sediments. Sediments from three areas were sampled for this study; they were the Alexandra Canal, Captains Flat and Jenolan Caves in New South Wales, Australia. In each area several sites were sampled. For each site there is a brief description of the catchment geology and hydrology. Selected sediment-associated waters in the areas were analysed for their metal concentrations as well as for ultratrace levels of APCAs employing a method developed in the present study. The waters were analysed for the major ions Ca2+, Mg2+, K+, Na+, Cl-, NO3- and SO42-. The sediments from selected sites in each of the areas were dried and fractionated. The dry total and fine sediments were analysed for their metal content and the latter was found to adequately represent the former in this respect. Water samples from the three areas showed different chemistries and exhibited more subtle differences between sites. In general, the Alexandra Canal waters are saline and alkaline and are a mixture of urban runoff and seawater; the Captains Flat waters are acidic and contain high sulfate from acid mine and tailings drainage; the Jenolan Caves waters are neutral and have the features characteristic of waters draining through limestone. The APCA contamination in all water samples when ranked against other global sites is very low. Although the current APCA levels in the waters appear low, it was concluded that they should be closely monitored so that efforts can be made to minimise the risk of APCAs being hazardous environmental contaminants and also that any remobilisation of heavy metals from sediments by APCAs can be controlled. Agitation and column laboratory-scale experiments were carried out in order to obtain an understanding of the remobilisation of metals by contamination levels of APCAs in water, both as the individual APCAs and as a mixture of APCAs. Complimentary experiments were carried out using a molar excess of APCAs calculated from the metal concentrations obtained by acid digestion (assuming 1:1 metal complex formation). Both types of remobilisation experiments were designed to investigate the role that redox potential (Eh) and concentration of APCAs in natural waters have on the remobilisation of heavy metals from the sediments. The agitation experiments were employed to assess metal remobilisation for the situation where the sediments are disturbed while the column experiments explored metal remobilisation for the case where the sediments are left undisturbed in situ. The major conclusions from the agitation experiments that used fine sediment from the Alexandra Canal were that 100 ppm APCA solutions will remobilise metals from the sediments under oxic conditions but only remobilise infinitesimally small amounts of metal under anoxic conditions. The use of fine sediments for the duplicate agitation experiments was found to give adequate duplication of results. A mixture of APCAs in solution acts similarly to the average of the three individual APCA solutions, showing that there are no antagonistic or synergistic effects likely to occur when they are found together in the environment. It was found that the mmoles of the metals remobilised exceeded the mmoles of the APCAs added when 500.0 mL of 100 ppm APCA solution was used on 50.00 g of sediment. This might be due to APCAs remobilising metals from the sediments in ways other than by complexation. Even though an excess of APCAs was available, metal remobilisation was not complete when the experiments were forced to terminate. During the 14 days of the experiment, only one quarter of the metals liberated from the sediment by HNO3 and 30 % H2O2 digestion were remobilised by the APCAs. Therefore an excess of free APCAs remains in solution. Fine sediments from Alexandra Canal, Captains Flat and Jenolan Caves were employed in the oxic agitation experiments using excess APCAs in solution. These experiments resulted in the following major conclusion: when producing an APCA remobilisation signature for trace and ultratrace metals, the geochemistry of the site is of secondary importance to the source of the contaminating metals. This is a feature of the trace and ultratrace metal speciation in the source rather than their concentration in it. From the different levels of calcium present in the three areas it was found that calcium is unlikely to form stable 1:1 APCA complexes at the pH values employed and is unlikely to compete with the heavy metal remobilisation by APCAs. Total sediments from Alexandra Canal and 100 ppm APCA solutions were employed for the column leaching experiments. From mass, pore water volumes and flow measurements it was shown that the ten mini cores taken from the same site were not true replicates. Despite this, when the sediments have settled and the pore waters removed from the cores, the levels of metal being leached stabilise and may represent a clearer picture of the in situ metal leaching from sediment with time. The levels of metal leached from the cores in 14 days suggest that during this period the cores are essentially anoxic, with the oxygen supplied from the oxic leaching solutions used for inorganic and microbial processes in the sediments. Agitation experiments appeared to yield an adequate picture of what would happen if free APCA solution came in contact with fine sediments suspended in the water column. Column leaching experiments employing total sediment were found to be only of limited value in assessing heavy metal remobilisation from undisturbed sediment. These experiments do not give a reliable assessment of the bioavailability of heavy metals and further testing of the acute and chronic toxicity of the sediments is recommended. APCA solutions that have been used in sediment and soil washing under conditions related to those used in the present study may contain an excess of the free APCAs as well as APCA heavy metal complexes and hence may be toxic to biota.

Thesis (Ph.D.) -- McMaster University, 1997. / Includes bibliographical references (leaves 175-181). Also available via World Wide Web.

Made available in DSpace on 2015-03-26T13:47:22Z (GMT). No. of bitstreams: 1 texto completo.pdf: 652961 bytes, checksum: 0a4c25df5d112d62a6fc101c27fb0466 (MD5) Previous issue date: 2013-03-15 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / One of the main deleterious factors inherent to the process of canine semen freezing is the large amount of sperm membranes lesions observed in the thawing. The freezing induce some destabilization of cell membrane and changes in the conformation between membrane receptors and ionic channels, promoting the calcium influx and increasing the probability of a premature acrosome reaction (AR), that invalidate the fertilizantion of the oocyte. The calcium is the principal inducing agent of the AR in vitro, and there is not recent reports about the biochemical composition of the seminal plasm and about the calcium levels that prevent the premature AR in the frozen of the domestic dog semen too. This study aimed to evaluate the alkaline phosphatase and cationic composition in seminal plasma of the fractions of dog ejaculate; and also test the effects of calcium amount reducing in freezing medium using the EDTA as a chelating agent. The semen was collected from three half-breed dogs. The sperm-rich fraction (SRF) and the prostatic fraction (PF) were separately collected. Both samples were evaluated by spectrophotometry, measuring the concentrations of calcium, sodium, potassium, alkaline phosphatase (AP), and the freezing medium. The fresh semen was evaluated by classical tests (strength, progressive motility, morphology, and membrane integrity). The remainder was divided into three aliquots that were diluted in a freezing medium based on tris-citrate-egg yolk, glycerol and equex with different concentrations of EDTA. The first treatment did not contain EDTA, treatment 2 contained 0.1% EDTA and the third, 0.25%. The most abundant cation in seminal plasma of these dogs was sodium, followed by potassium and calcium, respectively, both in SRF and in PF, without significant difference between the concentrations of these ions in both fractions. The AP obtained in SRF was significantly higher (p <0.000001) than that obtained in PF. There was a high concentration of calcium in the freezing medium based, that was significantly reduced in the treatments with EDTA. Deleterious effects were observed in all analyzed parameters in thawed semen compared with fresh semen (progressive motility, morphology, and membrane integrity). With the use of fluorescent probes, we did not note significant difference in the percentage of the plasmatic membranes e acrosomal membranes injured among the treatments with different EDTA concentrations. The extracellular medium has high calcium concentration, and despite the EDTA had significantly reduced the extracellular calcium in those treatments that it was added, there was not acrosomal membrane injury reduction in these treatments. This may have been caused because the concentration of this cation still remained high in comparision with its concentration in the original seminal plasma. We note too that the EDTA did not presented deleterious effects on the spermatozoa inside the evaluated parameters. / Um dos principais fatores deletérios, inerentes ao processo de congelamento de sêmen canino, é a grande quantidade de lesões de membranas espermáticas observada ao descongelamento. O congelamento induz a desestabilização das membranas celulares e alterações na conformação de receptores e canais iônicos, promovendo influxo de cálcio para o citosol, aumentando a chance de ocorrer prematuramente a reação acrossomal (RA), o que pode inviabilizar a fertilização do ovócito. O cálcio é reconhecido como o principal agente indutor da RA em espermatozoides de mamíferos. Não existem relatos recentes sobre meios de congelamento de sêmen de cão que contenham concentrações de cálcio preventivas à RA prematura. Os objetivos deste estudo foram avaliar quantitativamente a concentração dos cátions cálcio, sódio e potássio e da enzima fosfatase alcalina nas frações dos ejaculados de cães e também testar o efeito da redução da quantidade de cálcio no meio de congelamento utilizando o EDTA como quelante. Utilizou-se ejaculados de três cães mestiços, coletando em separado a fração rica em espermatozoides (FR) e a fração prostática (FP). Ambas foram avaliadas por espectrofotometria para aferição das concentrações dos cátions e da FA, assim como os meios de congelamento utilizados. O sêmen fresco foi avaliado por meio de testes clássicos (vigor, motilidade, hiposmótico e morfologia espermática) e o restante foi dividido em três alíquotas para diluição em meio base de congelamento tris-citrato- gema de ovo com glicerol e equex, meio básico contendo 0,1% de EDTA e meio básico contendo 0,25% de EDTA. O cátion estudado que se apresentou mais abundante no plasma seminal foi o sódio, seguido pelo potássio e o cálcio, tanto na FR quanto na FP, não havendo diferença entre as concentrações em ambas as frações (p >0,05). A FA obtida na FR foi maior que a obtida na FP (p<0,05). Observou-se elevada concentração de cálcio no meio base de congelamento, a qual foi reduzida nos tratamentos com EDTA (p<0,05). Houve efeitos deletérios em todos os parâmetros analisados no sêmen descongelado em comparação com o sêmen fresco (vigor, motilidade, integridade de membrana plasmática e morfologia). Não foi observada diferença na avaliação de lesões nas membranas plasmática e acrossomal com uso de sondas fluorescentes entre os meios com diferentes concentrações de EDTA (p>0,05). Embora o uso de EDTA tenha reduzido o cálcio extracelular, a concentração deste cátion permaneceu alta em comparação com sua concentração original no plasma seminal, fator que pode ser responsável pela não redução de lesões de membrana acrossomal nos tratamentos com EDTA. Por outro lado o EDTA não apresentou efeito deletério sobre os espermatozoides de acordo com os parâmetros avaliados.