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Temporal assessment of volatile organic compounds at a site with high atmospheric variability in the North-West Province / Kerneels JaarsJaars, Kerneels January 2012 (has links)
Volatile organic compounds (VOCs) are emitted into the atmosphere from biogenic and
anthropogenic sources with atmospheric lifetimes ranging from minutes to months,
depending on the specific VOC compound considered. It is estimated that biogenic VOCs
(BVOCs) (e.g. isoprenes, terpenes) make up 90% of the global atmospheric VOC budget.
However, in highly industrialised regions, anthropogenic VOCs (e.g. benzene, toluene,
ethylbenzene and xylene, combined abbreviated as BTEX) might dominate. VOCs have
various reversible and irreversible effects on human health. They also have environmental
impacts that range from changes in the population of terrestrial and aquatic ecosystems to the
extinction of vulnerable species. VOCs are precursors for the formation of ozone (O3) during
solar radiation initiated reactions in the presence of NOx. Tropospheric O3 is considered a
pollutant, with negative impacts on human health, ecosystems and food security. O3 is also a
short-lived greenhouse gas. Through reactions with radical species, VOCs lead to the
formation of higher molecular weight organic compounds, which produce carbon monoxide
(CO), peroxyacytyl nitrate (PAN) and ultimately secondary organic aerosol (SOA) particles.
SOA particles impact directly on air quality and visibility, as well as directly and indirectly
on the radiation balance of the earth that contributes to the regulation of climate.
Notwithstanding the importance of atmospheric VOCs, limited data is available for VOCs in
South Africa. In this study, a comprehensive dataset of BVOC and anthropogenic VOC
species was obtained at the Welgegund measurement station in the North West Province,
South Africa. Measurements were conducted from 9 February 2011 to 4 February 2012.
Samples were collected on Tenax-TA and Carbopack-B adsorption tubes twice a week for
two hours during day time and two hours during night time. The first 1.25m of the stainless
steel sampling inlet was heated to 120ºC to remove O3 that could lead to sample degradation.
Analyses of the sampled adsorption tubes were conducted by thermal desorption, cryofocusing,
re-desorption, followed by gas chromatography separation and analysis with a mass
selective detector (GC-MS).
The results indicated that toluene was the most abundant aromatic hydrocarbon and heptane
the most abundant alkane. Benzene is currently the only VOC listed as a criteria pollutant in
the South African Air Quality Act with an annual average standard of 1.6ppb. The annual median benzene concentration was 0.13 ppb, while the highest daily benzene concentration
measured was 8.7 ppb. No distinct seasonal cycles were identified for anthropogenic VOC
species measured, i.e. aromatic hydrocarbons and alkanes. However, air mass history
analysis indicated that air masses that passed over the Mpumalanga Highveld, the Vaal
Triangle and the Johannesburg-Pretoria conurbation (collectively referred to as Area I) had
significantly higher concentrations of these anthropogenic VOCs compared to air masses that
passed over the western and eastern Bushveld Igneous Complex, and a region over which air
masses typically followed an anti-cyclonic movement pattern (collectively referred to as Area
II). Anthropogenic VOC levels in air masses that passed over the regional background (areas
with no large point sources) had levels similar to air masses that had passed over Area II.
Relatively good interspecies correlations (r > 0.8) between most of the aromatic
hydrocarbons in air masses that had passed over Area I, with the exception of benzene,
indicated that these species had common sources. Benzene, however, correlated well with
CO, indicating that sources associated with incomplete combustion were most likely the
origin of benzene in air masses that had passed over Area I.
The interspecies concentration ratios for plumes passing over Area I indicated that this source
region is relatively close to the Welgegund monitoring station and air masses that passed over
this source region were substantially influenced by anthropogenic activities. The
concentration ratios for plumes that passed over Area II and the Regional Background
indicated that these were aged air masses. Furthermore, the concentration ratios of toluene,
ethylbenzene and o,m,p-xylene (TEX) to the total aromatic concentration for air masses that
passed over the various source regions showed a greater contribution to the total VOC
concentration during periods of higher temperature, i.e. summer. This proved that the
evaporation of solvents contributes significantly to VOC levels during the months with higher
temperatures.
The relative contribution of aromatic hydrocarbons to photochemical O3 formation in air
masses that passed over the various source regions indicated the highest contribution was
observed for air masses that passed over Area I, with Area II and the Regional Background in
the same order of magnitude.
The annual temporal variations of the measured BVOCs indicated that 2-methyl-3-buten-2-ol
(MBO) and isoprene exhibited distinct seasonal patterns, i.e. higher values in summer and
lower values in winter. The monoterpenes (MT) and the sesquiterpenes (SQT) did not follow distinct seasonal patterns. BVOC concentrations correlated relatively well to seasonal
variations in temperature, photosynthetically active radiation (PAR), rainfall, relative
humidity (RH) and CO2 flux. This proved that biogenic activity is responsible for BVOCs
emitted. The most abundant MT was -pinene, while -caryophyllene was the most abundant
SQT with annual median concentrations of 0.468 ppb and 0.022 ppb, respectively. Pollution
roses for isoprene showed a dominance of sources from the north-west to the north-east, as
well as the south-east. These directions correlated to areas where pockets of the savannah
biome are located. / Thesis (MSc (Environmental Sciences))--North-West University, Potchefstroom Campus, 2013
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152 |
Temporal assessment of volatile organic compounds at a site with high atmospheric variability in the North-West Province / Kerneels JaarsJaars, Kerneels January 2012 (has links)
Volatile organic compounds (VOCs) are emitted into the atmosphere from biogenic and
anthropogenic sources with atmospheric lifetimes ranging from minutes to months,
depending on the specific VOC compound considered. It is estimated that biogenic VOCs
(BVOCs) (e.g. isoprenes, terpenes) make up 90% of the global atmospheric VOC budget.
However, in highly industrialised regions, anthropogenic VOCs (e.g. benzene, toluene,
ethylbenzene and xylene, combined abbreviated as BTEX) might dominate. VOCs have
various reversible and irreversible effects on human health. They also have environmental
impacts that range from changes in the population of terrestrial and aquatic ecosystems to the
extinction of vulnerable species. VOCs are precursors for the formation of ozone (O3) during
solar radiation initiated reactions in the presence of NOx. Tropospheric O3 is considered a
pollutant, with negative impacts on human health, ecosystems and food security. O3 is also a
short-lived greenhouse gas. Through reactions with radical species, VOCs lead to the
formation of higher molecular weight organic compounds, which produce carbon monoxide
(CO), peroxyacytyl nitrate (PAN) and ultimately secondary organic aerosol (SOA) particles.
SOA particles impact directly on air quality and visibility, as well as directly and indirectly
on the radiation balance of the earth that contributes to the regulation of climate.
Notwithstanding the importance of atmospheric VOCs, limited data is available for VOCs in
South Africa. In this study, a comprehensive dataset of BVOC and anthropogenic VOC
species was obtained at the Welgegund measurement station in the North West Province,
South Africa. Measurements were conducted from 9 February 2011 to 4 February 2012.
Samples were collected on Tenax-TA and Carbopack-B adsorption tubes twice a week for
two hours during day time and two hours during night time. The first 1.25m of the stainless
steel sampling inlet was heated to 120ºC to remove O3 that could lead to sample degradation.
Analyses of the sampled adsorption tubes were conducted by thermal desorption, cryofocusing,
re-desorption, followed by gas chromatography separation and analysis with a mass
selective detector (GC-MS).
The results indicated that toluene was the most abundant aromatic hydrocarbon and heptane
the most abundant alkane. Benzene is currently the only VOC listed as a criteria pollutant in
the South African Air Quality Act with an annual average standard of 1.6ppb. The annual median benzene concentration was 0.13 ppb, while the highest daily benzene concentration
measured was 8.7 ppb. No distinct seasonal cycles were identified for anthropogenic VOC
species measured, i.e. aromatic hydrocarbons and alkanes. However, air mass history
analysis indicated that air masses that passed over the Mpumalanga Highveld, the Vaal
Triangle and the Johannesburg-Pretoria conurbation (collectively referred to as Area I) had
significantly higher concentrations of these anthropogenic VOCs compared to air masses that
passed over the western and eastern Bushveld Igneous Complex, and a region over which air
masses typically followed an anti-cyclonic movement pattern (collectively referred to as Area
II). Anthropogenic VOC levels in air masses that passed over the regional background (areas
with no large point sources) had levels similar to air masses that had passed over Area II.
Relatively good interspecies correlations (r > 0.8) between most of the aromatic
hydrocarbons in air masses that had passed over Area I, with the exception of benzene,
indicated that these species had common sources. Benzene, however, correlated well with
CO, indicating that sources associated with incomplete combustion were most likely the
origin of benzene in air masses that had passed over Area I.
The interspecies concentration ratios for plumes passing over Area I indicated that this source
region is relatively close to the Welgegund monitoring station and air masses that passed over
this source region were substantially influenced by anthropogenic activities. The
concentration ratios for plumes that passed over Area II and the Regional Background
indicated that these were aged air masses. Furthermore, the concentration ratios of toluene,
ethylbenzene and o,m,p-xylene (TEX) to the total aromatic concentration for air masses that
passed over the various source regions showed a greater contribution to the total VOC
concentration during periods of higher temperature, i.e. summer. This proved that the
evaporation of solvents contributes significantly to VOC levels during the months with higher
temperatures.
The relative contribution of aromatic hydrocarbons to photochemical O3 formation in air
masses that passed over the various source regions indicated the highest contribution was
observed for air masses that passed over Area I, with Area II and the Regional Background in
the same order of magnitude.
The annual temporal variations of the measured BVOCs indicated that 2-methyl-3-buten-2-ol
(MBO) and isoprene exhibited distinct seasonal patterns, i.e. higher values in summer and
lower values in winter. The monoterpenes (MT) and the sesquiterpenes (SQT) did not follow distinct seasonal patterns. BVOC concentrations correlated relatively well to seasonal
variations in temperature, photosynthetically active radiation (PAR), rainfall, relative
humidity (RH) and CO2 flux. This proved that biogenic activity is responsible for BVOCs
emitted. The most abundant MT was -pinene, while -caryophyllene was the most abundant
SQT with annual median concentrations of 0.468 ppb and 0.022 ppb, respectively. Pollution
roses for isoprene showed a dominance of sources from the north-west to the north-east, as
well as the south-east. These directions correlated to areas where pockets of the savannah
biome are located. / Thesis (MSc (Environmental Sciences))--North-West University, Potchefstroom Campus, 2013
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153 |
Molecular Mechanisms of Polycyclic Aromatic Hydrocarbon-induced Teratogenesis in Zebrafish (Danio rerio)Van Tiem, Lindsey Anne January 2011 (has links)
<p>Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous environmental contaminants formed from the incomplete combustion of fossil fuels and are found in the environment as complex mixtures. PAHs are developmentally toxic to fish, causing yolk sac edema, hemorrhaging, craniofacial malformations and cardiac defects including impaired heart looping, elongated heart, decreased blood flow, and pericardial effusion. Previous research has shown that many of the toxic effects of PAHs are mediated through the aryl hydrocarbon receptor (AHR), which upregulates phase I and II metabolic genes, but the underlying mechanisms of PAH-induced toxicity are not yet known. The primary goal of this dissertation was to better understand the molecular mechanisms by which PAH mixtures cause developmental toxicity in fish. To this end, the zebrafish (Danio rerio) was used as a developmental model. Simple mixtures consisting of a PAH that is an AHR agonist (benzo[a]pyrene or benzo[k]fluoranthene) and a PAH that is a cytochrome P450 1 (CYP1) inhibitor (fluoranthene) were used in these experiments along with the dioxin-like compound 3,3',4,4',5-pentachlorobiphenyl (PCB-126). Morpholino gene knockdown was used to examine the role of specific genes in response to PAHs, gene expression changes in response to PAH exposures were examined via QPCR, quantification of pericardial effusion was used as a metric for cardiac toxicity, and CYP1 activity was measured as an indication of AHR pathway induction. First, PAH mixtures consisting of an AHR agonist (BkF) and a CYP1 inhibitor (FL) induced cardiac toxicity that was preceded by upregulation of CYP1 and redox-responsive gene expression, and these effects were dependent upon the AHR2. Second, knockdown of glutathione s-transferase pi class 2 (GSTp2), part of phase II metabolism, exacerbated PAH-induced toxicity but did not affect PCB-126-induced toxicity. Third, knockdown of another isoform of the AHR, AHR1, exacerbated PAH- and PCB-126-induced toxicity and increased CYP1 activity but did not affect CYP expression in response to these agonists. Simultaneous knockdown of AHR1A and AHR2 did not exacerbate nor ameliorate PAH-induced toxicity but did prevent PCB-126-induced toxicity. Fourth, to examine AHR2-dependent and AHR2-independent gene induction in zebrafish hearts in response to PAHs, microarrays were used. Gene expression changes caused by PAHs were largely AHR2-dependent and consisted of genes involved in cell adhesion, oxidation-reduction, and TGF-&beta signaling processes as well as genes involved in heart structure and function. These findings help to elucidate how PAHs elicit deformities during development and highlight differences between PAHs and other AHR agonists. Additionally, these experiments have identified other genes in addition to AHR2 that are involved in mediating or responding to the toxicity of PAHs.</p> / Dissertation
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The action of 1-nitroso-8-nitropyrene in Escherichia coli: DNA adduct formation and mutational specificity in the lacI gene.Lambert, Iain Baker. MCCALLA, D. R. Unknown Date (has links)
Thesis (Ph. D.)--McMaster University (Canada), 1990. / Source: Dissertation Abstracts International, Volume: 52-10, Section: B, page: 5244. Supervisor: D.R. McCalla.
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155 |
Effects of cyclodextrin on extraction and fungal remediation of polycyclic aromatic hydrocarbon-contaminated Mahoning River sediment /Pabba, Sowmya. January 2008 (has links)
Thesis (M.S.)--Youngstown State University, 2008. / Includes bibliographical references (leaves 57-64). Also available via the World Wide Web in PDF format.
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156 |
Microbial community structure by fatty acid analysis during polycyclic aromatic hydrocarbon degradation in river sediment augmented with Pleurotus ostreatus /Sajja, Sarala Kumari. January 2008 (has links)
Thesis (M.S.)--Youngstown State University, 2008. / Includes bibliographical references (leaves 33-36). Also available via the World Wide Web in PDF format.
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157 |
Study of air-borne polycyclic aromatic hydrocarbons in El Paso, TXSantiago, Lynn Marie, January 2008 (has links)
Thesis (M.S.)--University of Texas at El Paso, 2008. / Title from title screen. Vita. CD-ROM. Includes bibliographical references. Also available online.
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158 |
Large scale synthesis and derivatization of corannulene the smallest buckybowl /Bachawala, Praveen, January 2006 (has links)
Thesis (M.S.) -- Mississippi State University. Department of Chemistry. / Title from title screen. Includes bibliographical references.
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159 |
Mechanisms of resistance to halogenated and nonhalogenated ahr ligands in chronically contaminated killifish populationsArzuaga, Xabier. January 2004 (has links) (PDF)
Thesis (Ph. D.)--University of Kentucky, 2004. / Title from document title page (viewed Jan. 7, 2005). Document formatted into pages; contains ix, 141p. : ill. Includes abstract and vita. Includes bibliographical references (p. 128-139).
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Exposures to silica and inducers of xenobiotic metabolism in the rat lungBattelli, Lori A. January 2004 (has links)
Thesis (M.S.)--West Virginia University, 2004. / Title from document title page. Document formatted into pages; contains vii, 71 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 64-70).
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