Thesis (Ph.D. (Chemistry)) - Rhodes University, 2007.

No description available.

Thesis (Ph. D.)--Joint Program in Oceanography (Massachusetts Institute of Technology, Dept. of Biology; and the Woods Hole Oceanographic Institution), 2007. / "February 2007." Department of origin: Biology. Originally issued as the author's thesis (Ph. D.)--Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2007. Includes bibliographical references.

Thesis (MAppSc) -- Auckland University of Technology, 2004. / Also held in print (110 leaves, 30 cm.) in Wellesley Theses Collection (T 547.01 MAG)

No description available.

Air pollution has become a serious environmental issue around the world. Among the multiple pollutants like NOx and O3, the atmospheric particulate matter with an aerodynamic diameter less than 2.5 µm (PM2.5) has been the most serious problem lately. The daily life and health of general public are greatly affected by PM2.5. For instance, the extended exposure to PM2.5 was reported to have association with increased prevalence of heart and lung diseases. China has suffered from serious PM2.5 pollution for many years. The vast territory, abundant anthropogenic activities and various geographical features make the formation mechanisms and possible health effects of PM2.5 become diverse and complicated. Because of that, regional study is necessary to control PM2.5 pollution and reduce the associated health risks. Taiyuan and Guangzhou are two typical megacities with strong regional characteristics in North and South China, both of which are subjected to PM2.5 pollution for long time. Through the analysis of PM2.5 samples collected from Taiyuan and Guangzhou, it will benefit the investigations of sources and toxicities of PM2.5 in Northern and Southern regions in China. Due to the complexity, research on components of PM2.5 is important. Polyaromatic organic contaminants are an important PM2.5 composition because of their relatively high concentration and obvious toxicity. In this study, polycyclic aromatic hydrocarbons (PAHs), nitro-PAHs (NPAHs), hydroxy-PAHs (OHPAHs) in PM2.5 samples from Taiyuan and Guangzhou were determined. A novel atmospheric pressure gas chromatography-tandem mass spectrometry (APGC-MS/MS) method with higher sensitivity was developed. 19 PAHs, 18 NPAHs and 12 OHPAHs in PM2.5 were analyzed with the method detection limits of 0.021 (PAHs), 0.001 (NPAHs) and 0.005 (OHPAHs) pg m-3, respectively. The developed APGC-MS/MS method provided acceptable recoveries (70 - 120%) and precision (RSD < 15%). PM2.5 samples collected from Taiyuan and Guangzhou from May. 2017 to April. 2018 were analyzed for 19 PAHs, 18 NPAHs and 12 OHPAHs. The pollution characteristics, including contamination levels, sources and possible influences on human health, were investigated and compared between the two sampling sites. Compared to Guangzhou, Taiyuan had higher contamination levels for most of the determined PAHs, NPAHs and OHPAHs in PM2.5. Except for NPAHs, whose major source was the OH· radical-initiated secondary formation, the predominant pollution sources of PAHs and OHPAHs in PM2.5 were different in these two cities. The mixed primary source of coal combustion and traffic emission was predominant for both PAHs and OHPAHs in PM2.5 from Taiyuan. But in Guangzhou, single primary traffic emission was major source. Higher carcinogenic health risks of PM2.5 were found in Taiyuan for adults, children and infants compared to Guangzhou based on the determined concentrations of PAHs and NPAHs. Obvious temporal and spatial variations among Taiyuan and Guangzhou were seen, which indicated that the pollution status of PAHs, NPAHs and OHPAHs in PM2.5 in Taiyuan was serious. The pollution levels of PM2.5-bound PAHs and NPAHs in Guangzhou also became higher in recent years. Besides PAHs and their derivatives, 14 emerging polycyclic aromatic sulfur heterocycles (PASHs) were detected in PM2.5 collected from Taiyuan and Guangzhou. They were assessed by accurate quantification, investigation of contamination levels and pollution sources, and the preliminary studies of pollutant-induced toxic effects. A novel APGC-MS/MS method was developed for the determination of the PASHs in PM2.5 with superior sensitivity of 0.052 -1.673 pg m-3. Higher contamination levels in atmosphere were found in Taiyuan at ng m-3. Coal combustion/secondary formation and traffic emission/secondary formation were found as pollution sources of the PASHs in PM2.5 from Taiyuan and Guangzhou, respectively. Dithiothreitol (DTT) and cell viability assays were performed for the preliminary assessment of PASH-induced reactive oxygen species (ROS) production and cell toxicity based on the exposure dosage for human. The results indicated that PASHs in PM2.5 collected from Taiyuan could lead to oxidative stress and human bronchial epithelial cells' death. The toxicity results suggest that more efforts are necessary to control the local primary sources and secondary formation of PASHs in PM2.5. In summary, a novel analytical method using APGC-MS/MS was developed and successfully applied for determination of different polyaromatic organic contaminants in PM2.5. 19 PAHs, 18 NPAHs, 12 OHPAHs and 14 PASHs in PM2.5 collected from Taiyuan and Guangzhou, the typical regions in North and South China, were determined. The pollution characteristics, including contamination levels, sources, health risks and temporal/spatial distributions were investigated and compared. Significantly different pollution characteristics of PAHs, NPAHs and OHPAHs in PM2.5 showed a close connection between pollution features with local economic structures. For the 14 emerging PASHs, their pollution status, sources and implication for human health in these two sites were studied. Compared to Guangzhou, Taiyuan had relatively higher exposure levels and health risks of PASHs in PM2.5 for local people. The study of pollution characteristics of the polyaromatic organic contaminants in PM2.5 from representative areas could provide a useful guidance for PM2.5 pollution control and general public health protection in China.

Air pollution has become a serious environmental issue around the world. Among the multiple pollutants like NOx and O3, the atmospheric particulate matter with an aerodynamic diameter less than 2.5 µm (PM2.5) has been the most serious problem lately. The daily life and health of general public are greatly affected by PM2.5. For instance, the extended exposure to PM2.5 was reported to have association with increased prevalence of heart and lung diseases. China has suffered from serious PM2.5 pollution for many years. The vast territory, abundant anthropogenic activities and various geographical features make the formation mechanisms and possible health effects of PM2.5 become diverse and complicated. Because of that, regional study is necessary to control PM2.5 pollution and reduce the associated health risks. Taiyuan and Guangzhou are two typical megacities with strong regional characteristics in North and South China, both of which are subjected to PM2.5 pollution for long time. Through the analysis of PM2.5 samples collected from Taiyuan and Guangzhou, it will benefit the investigations of sources and toxicities of PM2.5 in Northern and Southern regions in China. Due to the complexity, research on components of PM2.5 is important. Polyaromatic organic contaminants are an important PM2.5 composition because of their relatively high concentration and obvious toxicity. In this study, polycyclic aromatic hydrocarbons (PAHs), nitro-PAHs (NPAHs), hydroxy-PAHs (OHPAHs) in PM2.5 samples from Taiyuan and Guangzhou were determined. A novel atmospheric pressure gas chromatography-tandem mass spectrometry (APGC-MS/MS) method with higher sensitivity was developed. 19 PAHs, 18 NPAHs and 12 OHPAHs in PM2.5 were analyzed with the method detection limits of 0.021 (PAHs), 0.001 (NPAHs) and 0.005 (OHPAHs) pg m-3, respectively. The developed APGC-MS/MS method provided acceptable recoveries (70 - 120%) and precision (RSD < 15%). PM2.5 samples collected from Taiyuan and Guangzhou from May. 2017 to April. 2018 were analyzed for 19 PAHs, 18 NPAHs and 12 OHPAHs. The pollution characteristics, including contamination levels, sources and possible influences on human health, were investigated and compared between the two sampling sites. Compared to Guangzhou, Taiyuan had higher contamination levels for most of the determined PAHs, NPAHs and OHPAHs in PM2.5. Except for NPAHs, whose major source was the OH· radical-initiated secondary formation, the predominant pollution sources of PAHs and OHPAHs in PM2.5 were different in these two cities. The mixed primary source of coal combustion and traffic emission was predominant for both PAHs and OHPAHs in PM2.5 from Taiyuan. But in Guangzhou, single primary traffic emission was major source. Higher carcinogenic health risks of PM2.5 were found in Taiyuan for adults, children and infants compared to Guangzhou based on the determined concentrations of PAHs and NPAHs. Obvious temporal and spatial variations among Taiyuan and Guangzhou were seen, which indicated that the pollution status of PAHs, NPAHs and OHPAHs in PM2.5 in Taiyuan was serious. The pollution levels of PM2.5-bound PAHs and NPAHs in Guangzhou also became higher in recent years. Besides PAHs and their derivatives, 14 emerging polycyclic aromatic sulfur heterocycles (PASHs) were detected in PM2.5 collected from Taiyuan and Guangzhou. They were assessed by accurate quantification, investigation of contamination levels and pollution sources, and the preliminary studies of pollutant-induced toxic effects. A novel APGC-MS/MS method was developed for the determination of the PASHs in PM2.5 with superior sensitivity of 0.052 -1.673 pg m-3. Higher contamination levels in atmosphere were found in Taiyuan at ng m-3. Coal combustion/secondary formation and traffic emission/secondary formation were found as pollution sources of the PASHs in PM2.5 from Taiyuan and Guangzhou, respectively. Dithiothreitol (DTT) and cell viability assays were performed for the preliminary assessment of PASH-induced reactive oxygen species (ROS) production and cell toxicity based on the exposure dosage for human. The results indicated that PASHs in PM2.5 collected from Taiyuan could lead to oxidative stress and human bronchial epithelial cells' death. The toxicity results suggest that more efforts are necessary to control the local primary sources and secondary formation of PASHs in PM2.5. In summary, a novel analytical method using APGC-MS/MS was developed and successfully applied for determination of different polyaromatic organic contaminants in PM2.5. 19 PAHs, 18 NPAHs, 12 OHPAHs and 14 PASHs in PM2.5 collected from Taiyuan and Guangzhou, the typical regions in North and South China, were determined. The pollution characteristics, including contamination levels, sources, health risks and temporal/spatial distributions were investigated and compared. Significantly different pollution characteristics of PAHs, NPAHs and OHPAHs in PM2.5 showed a close connection between pollution features with local economic structures. For the 14 emerging PASHs, their pollution status, sources and implication for human health in these two sites were studied. Compared to Guangzhou, Taiyuan had relatively higher exposure levels and health risks of PASHs in PM2.5 for local people. The study of pollution characteristics of the polyaromatic organic contaminants in PM2.5 from representative areas could provide a useful guidance for PM2.5 pollution control and general public health protection in China.

Seeds, especially cereals and legumes are a vital component of the human diet and as a result of elevated levels of environmental pollution, seed-bearing crop plants are grown increasingly on contaminated soils. Although several studies have looked at seeds as potential sources of metals that may enter the food chain, very little research has been carried out to examine the effect of such toxicants on the physiology of these plant parts. This study examines the effect of two metal pollutants, namely Cd and Ni, on the development and functioning of soybean seeds. Cadmium was chosen because it is considered to be the most serious of the metal pollutants, is highly toxic to mammals and easily enters the food chain. Nickel, is relatively mobile within plants compared to other metal pollutants and also represents a potential threat to the environment. Soybean plants (cv Crawford) were grown to maturity in a circulating nutrient solution system, which in the case of treatment plants, was amended with either Cd or Ni. From the results of preliminary trials in which the effect of metal pollutant concentration on plant growth and pod production were examined, nutrient solution concentrations of 0.05 mg Cd/litre or 1 mg Ni/litre were used for routine cultivation of the plants (termed metal-treatment plants). Seeds were harvested at four (initially five) different growth stages and the effect of the metal pollutants on size and other developmental parameters investigated. Accumulation and distribution of Cd, Ni and other elements within the seeds was examined. Firstly, by using inductively coupled plasma-atomic emission spectroscopy (ICP-AES) and secondly, at a finer resolution utilising a nuclear rnicroprobe, coupled with proton induced X-ray emission (PIXE). The anatomy and ultra-structure of metal pollutant-treatment seeds was compared with that of control seeds using light as well as transmission electron microscopy (LM and TEM). Possible structural aberrations caused by the presence of Cd or Ni were identified. In another set of experiments, seeds were germinated in solutions of different concentrations of Cd or Ni (termed metal-germinated seeds). The LCso and ECso values for germination and radicle extension respectively, were derived. The effect of metal pollutants on seedling establishment was also examined by cultivating the plants further in nutrient solution containing different concentrations of the metal pollutants. Other seedlings (termed recovery seedlings), subsequent to germination in the metal pollutant, were transferred to the standard control nutrient solution. Uptake of metal pollutant, concentration of photosynthetic pigments and photosynthetic functioning were examined in metal-germinated, recovery and control seedlings. In the final section of the study, chemical speciation in the nutrient solution used for cultivation of metal-treatment plants was modelled using the speciation software MINTEQA2. Percentage bioavailability of the metal pollutants as well as of four nutritionally important metals, Fe, Mn, Mg and Zn was examined. Furthermore, computer simulations were also carried out to model the effect of pH and increasing metal pollutant concentration, on the bioavailability of the abovementioned metals. Addition of even low concentrations of Cd or Ni to the nutrient solution resulted in reduction in root biomass and pod (and hence seed) production. This effect increased with metal pollutant concentration. Cadmium appeared to be more phytotoxic than Ni and lower concentrations of the former were required elicit an equivalent response. Visual toxicity symptoms noted, included red pigmentation in the petioles, chlorosis of the trifoliate leaves followed by the appearance of necrotic areas. In addition, Ni-toxicity symptoms included terminal deformed pods, as well as red spots in the inter-veinal areas of leaves. Both Cd and Ni accelerated plant senescence. Leaf abscission was promoted and in the case of the older growth stages, the rate of pod development was increased relative to that of control pods. Nonetheless, the presence of metal pollutants did not appear to enhance pod abscission during the developmental period examined. In metal-treatment plants, pollutant loads in roots were much higher than in shoots. Cadmium levels in the seeds harvested from these plants were extremely low (approximately 1µg/g.dm) indicating that the metal is excluded from these tissues to a great extent. Nickel was more mobile than Cd, reaching higher levels than the latter in all plant parts and a concentration of approximately 50 µg/g.dm in mature treatment seeds. Pods did not appear to exclude entry of metal pollutants into the seeds and contained similar concentrations as the seeds in the case of Cd and lower concentrations in the case of Ni. Seed concentration of both metal pollutants (when expressed as µg/g.dm) was highest in the youngest growth stages and then decreased with age. Cadmium was found to decrease mean seed size relative to control seeds, but had no effect on the number of seeds per pod. Nickel on the other hand, exerted no effect on size but did reduce the average number of seeds contained in each pod. As a result of reduced mass, the presence of Cd in the nutrient solution reduced the lipid, starch and total N content of seeds harvested from soybean plants grown in such a medium. No significant effect on the quantity of storage reserves could be detected in Ni-treatment seeds. Mature seeds harvested from Cd-treatment plants had lower Fe and Mn, but higher Zn and Mg contents than control seeds. Nickel-treatment seeds also exhibited reduced Fe, Mn and elevated Zn contents, but Mg levels were also reduced. Shifts in seed concentrations of the nutritionally important metals noted above, were also found in pods, most notably a reduction in Fe content. Despite the presence of metal pollutants within the seeds, the extent of germination in metal pollutant-treatment seeds was not impaired compared to control seeds. The rate of germination, however, was depressed slightly in both metal treatments. Examination of metal distribution within seeds using ICP-AES revealed that Cd was localised mainly in the testa and cotyledons, with very little in the axis. Nickel was mainly concentrated in the axis and least in the cotyledons. Cadmium levels in metal-treatment seeds were too low for distribution maps to be made using PIXE and only point analyses were carried out. Overall, these results agreed with those obtained from ICP analysis. Nickel, which accumulated to higher levels within seeds, was mapped successfully using PIXE. The embryo axis appeared to contain the highest concentrations of Ni, particularly in the apical meristem and cortex, but was virtually absent from the root cap area and the central stele. Interesting elemental maps were also obtained for S, Fe and Mn (supplied in the nutrient solution at normal physiological concentrations). Levels of Ni in control seeds were extremely low and could not be mapped. The LC50 and EC50 values for germination and radicle elongation respectively, in the presence of exogenous metal pollutant, were found to be lower for Cd than Ni. This is consistent with the higher phytotoxicity of the former element. Radicle elongation was found to be more sensitive to the presence of exogenous metal pollutants than seed germination. The major effect on seedling establishment was reduction in growth, particularly of the lateral roots. As in the case of mature plants, pollutant loads in the roots of seedlings were higher than in shoots. Recovery seedlings appeared relatively healthy after a period of exposure to metal pollutants, up to a critical concentration of metal pollutant. Nonetheless, although little reduction in the concentration of photosynthetic pigments or the efficiency of photosynthetic functioning was recorded, two weeks after exposure to the metal pollutants, root biomass was still reduced relative to that of control seedlings. The total chlorophyll content of metal pollutant-germinated seedlings decreased at low concentrations of the metal pollutants, but then increased at higher concentrations. It is suggested that this is the result of the combined effects of inhibition of photosynthetic pigment synthesis, coupled to reduced leaf expansion. Metal pollutant-treatment and control seeds did not differ from each other in external appearance nor at the LM level. Slight ultra-structural variations were noted using TEM however, including the presence of vesicles in the nucleoplasm of Cd-treatment cotyledon cells, an increase in the number of crystalloid inclusions in protein bodies (possibly phytate) as well as an increased number of starch grains in the radicle tip cells of Ni-treatment seeds. Further research is needed to confirm these results. Significant ultra-structural changes in metal pollutant-germinated seedlings were noted compared to the controls. From examination of the ultra-structure of such seedlings, both Cd and Ni appeared to affect nuclear functioning, proteolysis, as well as starch grain formation. Cadmium elicited a response at lower concentrations than Ni. It is stressed that these are not necessarily the principal toxic actions of the metals however, as marked structural changes were apparent only at high concentrations. Aberrations to cytoplasm adjacent to the cell wall were also noted in cells from seedlings germinated in the presence of Ni. Computer speciation simulations using MINTEQA2 predicted that in the respective treatment solutions, 87% of Cd, but only 49% of Ni, was in a form suitable for plant uptake. Shifts in seed contents of Mg, Mn and Zn, in response to amendment of the nutrient solution with metal pollutants, could not be explained by changes in chemical speciation in the growth medium. The decrease in Fe content in Ni-treatment seeds on the other hand, may possibly be a consequence of decreased bioavailability of this ion in the nutrient solution. pH was found to exert an effect on the speciation profile of metal pollutants, as well as on that of nutrients. The most marked effect was noted on Nt2. The proportion of metal in this form (the bioavailable form) decreased from 49% to 3% when pH was increased from 6.0 to 7.0. Although plants are able to limit entry of metal pollutants into seeds to some extent, they do still enter these tissues and it is important that the effects on functioning of such plant parts be examined. This study reports preliminary findings on this aspect. Much work remains to be done however particularly with regard to the effect of metal pollutants on the quality of storage reserves, especially proteins. Furthermore, this work should be extended to the seeds of other important crop plants.

Syntheses, spectral, electrochemical and spectroelectrochemical studies of new thiol-derivatised MPc complexes were satisfactorily carried out. For the first time, spectroelectrochemistry gave evidence for the formation of Ni²⁺/Ni⁺ process in a NiPc complex. Significant insights as to the nature of Fe⁺Pc and Ni⁺Pc spectra were obtained. Transformations of chlorophenols using chemical and photochemical methods are presented. For cobalt tetrasulphophthalocyanine catalysed oxidation of chlorophenols using hydrogen peroxide as the oxidant, types of oxidation products formed depended on the solvent conditions. Photolysis of aqueous solutions of chlorophenols in the presence of immobilised non-transition metal phthalocyanine photosensitisers onto Amerlite® was carried out. For the first time, MPcS[subscript mix] complexes were immobilised on Amberlite® for use in heterogeneous photocatalysis. Photolysis of the chlorophenols resulted mainly in the formation of chlorobenzoquinone derivatives. The generation of singlet oxygen (¹O₂) by these immobilised MPc photosensitisers was found to play a major role in their photoactivities. Modifications of gold electrodes with the newly synthesised thiol-derivatised MPc complexes via electropolymerisation and SAM techniques are presented. Cyclic voltammetry, impedance spectroscopy (NiPcs only) and spectroelectrochemical techniques (NiPcs only) confirmed that the complexes formed films on gold electrodes. Stable and well packed SAM films as evidenced by the voltammetric characterisation were obtained. For the first time, optimisation of the time for SAM formation based on CV technique was studied. First example of a formation of MnPc-SAM was achieved. Catalytic activities of the NiPc towards chlorophenol depended on the nature of the NiPc in the polymer films and also anti-fouling ability of the films depended on polymer film thickness. The FeTBMPc polymer modified gold electrode showed the best catalytic activity in terms of peak potential, E[subscript p] when compared to reported work in literature for nitrate electrooxidation. Cyclic voltammetry and spectroscopy studies showed that the CoPcs, FePcs and NiPcs catalysed nitrite oxidation involve 2 electrons in total while that of McPcs involve 1 electron. Better catalytic performance towards sulphite electrooxidation were obtained for the CoPcs, FePcs and MnPcs which have metal based redox processes within the range of the sulphite electrooxidation peak while the NiPcs which did not show metal based oxidation reaction performed less.

No description available.