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1
Yuan, Tao 1968. "Dechlorination of environmentally recalcitrant chlorinated aromatic compounds." Thesis, McGill University, 2002. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=79208.
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Chlorinated aromatic compounds are an important group of compounds. Many of them have been produced in large quantities and they are indispensable to technological and societal benefits. But regulatory agencies have tightened regulations on the use and release of chlorinated aromatic compounds because of the scientific understanding of their toxicity, persistence, behavior in the environment and their potential to cause adverse effects on the ecosystem and human health.Pentachlorophenol (PCP), octachloronaphthalene and decachlorobiphenyl are all highly chlorinated aromatic compounds, of which, PCP has been used mainly as a biocide. Octachloronaphthalene and decachlorobiphenyl don't have practical use, but their congeners have been used widely as chemicals in industry. These compounds are toxic, recalcitrant and bio-accumulated within organisms. As the conventional treatment, incineration of these compounds can cause more serious problems, so that suitable alternatives need to be developed for their detoxification.
When compared with biodegradation or the thermal treatment of these compounds, chemical degradations have several merits. (Abstract shortened by UMI.)
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Jang, Eunseok. "Aspects of the chemistry of tin(IV) chalcogenide cyclic compounds containing sterically demanding amido ligands." Thesis, University of Sussex, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.357883.
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Kabir, Anwar. "Dechlorination of chlorinated organic compounds by zero-valent and bimetallic mixture." Thesis, McGill University, 2000. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=31246.
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Organochlorine (OC) compounds that include several pesticides as well as an array of industrial chemicals were very efficacious for their intended use but were also characterized by deleterious environmental impacts when released either intentionally or inadvertently. Their lipophilic nature, long persistence in the environment and threat to human health caused all the developed countries to ban the production of these chemicals as well as restricted the use of formulations containing these material for food production.A number of scientists have become involved in the development of intentional degradation methods/techniques for these compounds using zero-valent metals or bimetallic mixtures. To date, there is no single, simple and continuous procedure available to completely dechlorinate lindane or pentachlorophenol (PCP). This work describes the complete dechlorination of lindane and pentachlorophenol by zero-valent Zn, Fe and Fe/Ag bimetallic mixture as well as a supercritical fluid extraction technique for a more efficient mass transfer of the substrates to the surfaces of the metal catalyst. The dechlorination reaction occurs on the surface of metal particles with the removal of all the chlorine atoms from lindane and PCP in a matter of minute, and yields completely dechlorinated hydrocarbon molecules and chloride as products. (Abstract shortened by UMI.)
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Turoczy, Nicholas John, and mikewood@deakin edu au. "Adsorption and voltammetry of butyltin compounds." Deakin University, 1994. http://tux.lib.deakin.edu.au./adt-VDU/public/adt-VDU20050915.154112.
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The adsorption of tributyltin onto materials commonly used for the construction of sampling and analytical equipment from aqueous solutions of varying ionic composition has been examined. The adsorption appears to be controlled by non-polar interactions between tributyltin and the surface involved. Since the speciation and hence polarity of tributyltin is affected by the ionic composition of the medium, the extent of adsorption is affected by the salinity and pH of a sample. The adsorption is rapid and, unless strategies are adopted to eliminate its effects, may render analytical results invalid.
The electrochemistry of tributyltin, dibutyltin and monobutyltin, individually and in mixtures, has been investigated in aqueous media at mercury electrodes. The basic electrochemistry of each compound is summarised by the reaction
BunSn (4-n)+ + (4-n)e- right left harpoons BunSn
where n is the number of butyl groups attached to the tin atom. However, the electrochemistry of each compound is largely confined to the surface of the mercury electrode, and the simplicity of the above reaction is disrupted by polymerisation reactions and by butyl exchange processes occurring with the mercury electrode. When mixtures of butyltin compounds are present, the various processes that occur for each individual compound interfere with each other. A direct voltaminetric method for the determination of butyltin compounds in natural waters is therefore probably not possible.
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Wong, Wing-sze, and 黃穎詩. "Water chemistry in the Kam Tin basin, natural and authropogenic influences." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2007. http://hub.hku.hk/bib/B38605843.
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陳承欣 and Shing-yan Jackie Chan. "Environmental planning of new towns in Hong Kong: a case study : Tin Shui Wai." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2002. http://hub.hku.hk/bib/B3126072X.
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Ostertag, Sonja. "Estimated dietary exposure to perfluorinated compounds in Canada." Thesis, McGill University, 2007. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=112549.
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Perfluorinated carboxylates (PFCAs), sulfonates (PFSs) and perfluoroalkylsulfonamides (PFOSAs) have been detected in whole blood and serum of non-occupationally exposed humans, yet sources of exposure have not been fully elucidated. The objectives of this study were to estimate dietary exposure to perfluorooctane sulfonate (PFOS), PFCAs (C7--C 11) and fluorotelomer unsaturated carboxylates (FTUCAs) for the general Canadian and Inuit populations prior to the phase-out of perfluorooctyl-sulfonyl production by 3M and voluntary reductions in PFOA emissions under the PFOA stewardship program. PFCs were measured in 65 archived composite food samples prepared for the 1998 Canadian Total Diet Study (TDS) and 68 archived traditional foods from Nunavut using a newly developed methanol extraction combined with a solid phase extraction clean up. Dietary exposure was estimated using food intake data available from studies carried out between 1997 and 1998 in southern Canada and Nunavut.PFCs were detected in eight composite food samples from the Canadian TDS and in 61 traditional food samples. Elevated concentrations of PFCs were found in caribou liver (6.2+/-5.5 ng/g), ringed seal liver (7.7, 10.2 ng/g), polar bear meat (7.0 ng/g), beluga meat (7.0, 5.8 ng/g), luncheon meats (5.02 ng/g), cookies (2.7 ng/g), processed cheese (2.1 ng/g) and peppers (1.8 ng/g). Low levels of total PFCs (<1.5 ng/g) were measured in 41 traditional foods including: meat (caribou, ptarmigan, snow goose, bearded seal, walrus, black duck), berries, and fish (lake trout, arctic char). PFCs were not detected in beverages, unprocessed meats, breads, cereals and fruits from the TDS composite samples analyzed.
The ranges of estimated daily exposure to PFCs were between 2 and 59 ng-person-1 and 210 to 610 ng-person-1 for average Canadians and Inuit in Nunavut respectively. There were no statistically significant differences in mean PFC exposure levels for different age and gender groups in the general Canadian population. Inuit men in the 41 to 60 year old age group had statistically significantly higher estimated daily exposure to PFCs (p<0.05) than younger men and women from the same age group. This higher exposure was associated with the consumption of beluga muktuk, caribou liver and bearded seal intestine.
Traditional foods contributed a higher percentage to PFC exposure than market foods in all age and gender groups for the Inuit population. In general, caribou meat, arctic char meat and cookies contributed most to dietary exposure for Inuit, with caribou flesh contributing 43 to 75 percent to daily PFC dietary exposure. Dietary exposure for the general Canadian population was associated with the consumption of cakes and cookies, processed cheese, and regular cheese.
Levels of dietary exposure to PFCs estimated in these studies do not pose any significant health risk to either population based on current toxicological information.
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莊景彬 and King-pan Derek Chong. "Environmental and landscape improvements to the engineering orientatedSan Tin East Main Drainage Channel design." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2001. http://hub.hku.hk/bib/B31980818.
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Ho, King-yan, and 何景欣. "Ecological and human health risks associated with organotin contamination in the marine environment of Hong Kong and Shenzhen, China." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2014. http://hdl.handle.net/10722/208427.
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Organotin compounds (OTs), in particular tributyltin (TBT) and triphenyltin (TPT), have caused widespread adverse effects on marine organisms ever since their wide application as biocides in 1960s. For instance, TBT can induce the abnormal development of imposex in marine gastropods, and inhibit development and growth in oysters. A mandatory global ban on the use of OT-based antifouling systems, therefore, has been enacted by the International Maritime Organization to minimize their environmental impacts since September 2008. As a result, it is anticipated to see a reduction of OT contamination in the marine environment around the world. This study, therefore, primarily aims to test the hypothesis that there is a reduction of both OT contamination and its associated adverse impact to a common biomonitor, the rock shell Reishia clavigera along the coast in Hong Kong and Shenzhen, China through a series of field-based investigations.
Before the field study, a method was successfully developed to simultaneously quantify the concentrations of six common OTs (i.e., mono-BT, di-BT and TBT; mono-PT, di-PT and TPT) in molluscan tissues using gas chromatography-mass spectrometry. These six compounds coexist in marine environments. They are highly toxic to marine organisms and are able to induce imposex in gastropods like R. clavigera.
First, a territory-wide survey on tissue concentrations of the OTs and imposex status in R. clavigera collected from 28 coastal sites of Hong Kong was conducted in 2010. The results indicated that all female R. clavigera suffered from imposex, and all rock shells contained high TPT concentrations. A probabilistic ecological risk assessment revealed that 17.6% of R. clavigera across all sites were at risk due to exposure to TPT, whereas the risk associated with TBT was relatively low. The same species collected from Dapeng Bay and Daya Bay, Shenzhen also exhibited high tissue concentrations of TPT. Second, R. clavigera transplanted from relatively clean sites to polluted sites for six months showed increases in both imposex status and tissue concentration of OTs, confirming the association between OT contamination and imposex development. Third, a 25-month population dynamics study of R. clavigera showed a limited recruitment of the species in the polluted sites.
To verify if the observed OT contamination was widespread to other marine species in Hong Kong waters, a survey on the tissue concentrations of OTs in 11 local seafood species was conducted. Among them, the tongue sole Paraplagusia blochii had the highest tissue concentration of total OTs, with TPT as the most abundant residue. Potential health risk for consuming this benthic fish species was identified as both hazard quotient of TPT and hazard index exceeded unity.
The overall results demonstrate that the coastal marine environments in this region are still heavily contaminated with OTs especially TPT, and there is no obvious sign of recovery of R. clavigera populations. Hopefully, with further scientific investigations, both Hong Kong and China governments will take appropriate management actions to control the use and release of these priority pollutants with a view to safeguarding the marine ecosystem and human health in this region.HKU 3 Minute Thesis Award, 2nd Runner-up (2013)
published_or_final_version
Biological Sciences
Doctoral
Doctor of Philosophy
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Lau, Hoi-yin Melody, and 劉凱賢. "Environmental impacts and management of persistent organic pollutants in South China." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2009. http://hub.hku.hk/bib/B43783867.
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Blais, Jean-Simon. "Determination of alkyllead compounds and synthesis of alkyllead radiotracers." Thesis, McGill University, 1987. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=66177.
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Yu, Liang 1978. "Washing to detoxify soil burdened with PCB compounds." Thesis, McGill University, 2007. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=101693.
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Polychlorinated biphenyls (PCBs) are a group of 209 chemical congeners that are toxic and persistent organic contaminants---they have been present in the environmental for several decades. Sites contaminated with PCBs pose serious health and safety risks to the surrounding environment due to their toxicity, persistence and bioaccumulation in creature. Polychlorinated biphenyls were commercially produced complex mixtures for a variety of applications. Before production was discontinued world-wide in 1977, several million tons of PCBs have been directly disposed to the soil. Researchers have been encouraged to develop novel techniques/approaches to detoxify PCB compounds and PCB contaminated soil. Ideally, these methods would be inexpensive, rapid, efficient and environmentally benign.This study investigated novel approaches/techniques for PCB hydrodechlorination with noble metal catalyst in a continuous hydrogenation system, using a reactor column filled with Pd0/gamma-Al2O3 catalyst. Appreciable quantities of PCB compounds or other aromatic compounds were hydrodechlorinated and/or hydrogenated under mild conditions (90°C). The reaction efficiency was virtually complete if sufficient H2 was included in the mobile phase either by pure H2 or supercritical CO 2 combined with 5% H2.
The study also optimized conditions to wash PCBs washing condition from contaminated soil by sonication mixing and outlined an environmentally benign industrial application that combined soil washing with an at line PCBs hydrodechlorination process. The techniques/approaches developed in this study would seem to have a broad application in PCB dechlorination/detoxification and in the remediation of historically contaminated soil/sediments.
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Peatt, Anna C. (Anna Clare-Doreen) 1976. "New reaction media for organometallic chemistry." Monash University, School of Chemistry, 2003. http://arrow.monash.edu.au/hdl/1959.1/5829.
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Al-khzaiym, Tariq Mohammad Saleh. "Implication of the use of organic bismuth compounds on aspects of medical and environmental microbiology." Thesis, University of Sheffield, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.414657.
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Yi, Xianliang Andy, and 易先亮. "A comprehensive study on the ecological toxicity and risk of triphenyltin to aquatic organisms." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2014. http://hdl.handle.net/10722/202351.
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Liu, Zhen'guo. "Syntheses of macrocyclic oligomers for low-VOC coating process on the surface of metal substrates." Diss., Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/27435.
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Thompson, Jill Marie 1961. "Presence of selected organic compounds and their intermediates in municipal landfill leachates." Thesis, The University of Arizona, 1987. http://hdl.handle.net/10150/276632.
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This research involves the evaluation of municipal landfill leachates for specific hazardous compounds in an effort to qualitatively determine the potential for groundwater contamination. Leachate samples from five landfills were evaluated for thirteen EPA priority pollutants using gas chromatography. In addition, samples were analyzed for total organic carbon (TOC) and total organic halide (TOX). A solids analysis was performed on refuse excavated from one landfill. This analysis included organic halide determination of interstitial liquids, and a total halide determination for each solid sample. A solids/liquid partition coefficient was calculated from the results. The literature review includes a detailed section outlining the biological degradation of hazardous organic compounds in anaerobic environments similar to conditions found in landfills.
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Gupta, Ankur Kumar. "Measurement of Henry's constants of volatile organic compounds in aqueous solutions using headspace gas chromatography." Thesis, Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/11209.
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Daso, Adegbenro Peter. "The occurrence of brominated flame retardants (polybrominated diphenyl ethers and polybrominated biphenyl) in the Cape Town environment." Thesis, Cape Peninsula University of Technology, 2011. http://hdl.handle.net/20.500.11838/2010.
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Thesis (DTech (Environmental Health))--Cape Peninsula University of Technology, 2011.This study was aimed to provide baseline information about the environmental levels of selected PBDEs (BDE 28, 47, 100, 99, 154, 153, 183 & 209) and BB 153 in different matrices, including wastewater treatment plants' effluent, sludge, landfill leachate, river water and bottom sediment samples from different locations within the City of Cape Town. The monitoring of these contaminants was carried out bi-monthly over an extended period of 12 months beginning from April 2010 to March 2011. In this study, a total of 63, 168, 312, 93 and 108 samples for leachate, wastewater treatment plant (WWTP) sludge, effluent, river water and bottom sediment, respectively were collected from three landfill sites, four WWTPs and two rivers within the City of Cape Town. The aqueous matrices were extracted using a liquid-liquid extraction technique. The extraction of both sediment and sludge samples were performed using mechanical shaking and soxhlet extraction techniques, respectively. Extract obtained were further purified using multi-layer silica gel column chromatographic technique. The routine analysis of these target compounds was carried out using a gas chromatograph equipped with an electron capture detector (GC-µECD). However, the structural elucidation of these compounds was performed with a gas chromatography-time of flight-mass spectrometry (GC-TOF-MS) instrument.
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Tsui, Kin-yin Jeanie, and 徐健賢. "Biogenic volatile organic compound emissions in Hong Kong." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2006. http://hub.hku.hk/bib/B38597664.
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Abbass, Omed Akber. "Ozone Interaction with Indoor Building Materials and HVAC Filters." PDXScholar, 2017. https://pdxscholar.library.pdx.edu/open_access_etds/3771.
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As modern life develops, humans spend most of their time inside buildings. Understanding the effects of different building materials that exist indoors on indoor air quality is crucial to ensure comfort, health, and productivity of building occupants. Indoor air quality (IAQ) is an important field of building science that focuses on studying the existence of different compounds indoors. These compounds include: airborne particles such as dust, volatile organic compounds (VOCs) such as carbonyls, reactive gases such as radon, ozone and others. Ozone is a strong oxidant gas that has adverse effects on human health, and is highly reactive with building materials that exist indoors. This reaction may reduce its concentration indoors, but may produce other by-products that could be more harmful for human health than ozone itself.
In this dissertation, ozone reaction with different building materials is investigated in four studies. The first includes studying the effect of indoor carpet fiber type on ozone removal and carbonyl emissions. This study provides valuable data and knowledge about the importance of selecting carpet type and its effect on indoor environment. In the second study, different indoor plants were tested to evaluate their ability to remove ozone. The results from this study show wide variation between plants tested on ozone removal. Also, the ability of plants as ozone removal agent changes as light levels change. The third part studies ozone removal efficiency of HVAC filters previously installed in air handling units located on green and white membrane roofs of a commercial building. Detailed filter surface analysis using scanning electron microscope (SEM) was performed to understand the nature of deposits on these filters. The reason for differences in ozone removal efficiency of two filters in comparison with new filter is also discussed. The fourth study investigated ozone removal and carbonyl emissions from three different VOC content indoor latex paints. The outcomes from this research show that zero VOC latex paint has the most ozone effective removal capacity and this paint is the least carbonyl emitter.
The research presented in this dissertation adds new data, valuable knowledge, and expands the understanding of the importance of selecting indoor materials to raise indoor air quality and make the buildings' indoor environment healthier and safer.
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Lin, Wai-kuen, and 練惠娟. "Volatile organic compounds (VOCs) emission estimate of printing industry in the Pearl River Delta Region." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2011. http://hub.hku.hk/bib/B46734478.
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Schlanger, Joshua Lee. "Rates and energetics of organic vapor sorption by soils." Thesis, Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/19916.
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Forsyth, Donald Scott. "Determination of organolead salts in biological tissue." Thesis, McGill University, 1985. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=73971.
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Matzner, Robert Allan. "Characterization of aza-arene transport in saturated porous media." Diss., The University of Arizona, 1993. http://hdl.handle.net/10150/191179.
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Several factors which affect the transport of pyridine, quinoline and acridine (aza-arenes) in saturated porous media were investigated in laboratory experiments in order to provide data for input into coupled models that may be applied to predicting the fate of these compounds in groundwater. The effect of pH and ligand type and concentration on acridine solubility was studied in a series of batch and pH-stat experiments. There was a decrease in acridine solubility below the compound's pKₐ due to acridine/ligand precipitate formation. The reaction stoichiometry and solute/sorbent interactions of aza-arene adsorbed to porous silica were determined from batch adsorption and Raman spectroscopy experiments. The neutral aza-arene was hydrogen bonded to surface sites above the compound's pKₐ and there was a cation/ClO₄⁻ complex interacting with surface sites through dipole-dipole interactions below the pKₐ of the compound. The effect of pH, temperature, ligand type, average linear velocity and initial aqueous phase solute concentration on the adsorption of aza-arenes to porous silica was investigated in a series of column experiments. The extent of adsorption followed the trend pyridine < quinoline < acridine due to greater overlap of the molecule with adsorption sites as the number of rings increases. The extent of adsorption was greater below the compound's pKₐ than above because the complex was able to optimize its orientation with the surface. The extent of adsorption of neutral acridine was enhanced when carbonate was used as a buffer relative to phosphate due to carbonate's more exothermic hydration enthalpy. The isotherms were non-linear above and below the pKₐ of acridine. The enthalpy of the adsorption reaction was less exothermic below the compound's pKₐ than above due to the stronger hydrogen bonds formed between the surface and the neutral molecule compared to the dipole-dipole interactions that bond the complex to the surface below the pKₐ. Non-equilibrium effects on the adsorption reaction were minor. Adsorption-desorption was on the order of seconds to minutes. Kinetic effects became more important as temperature decreased.
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Morris, Kenneth Robert 1951. "THE SOLUBILITY OF HYDROPHOBIC POLLUTANTS IN WATER-COSOLVENT MIXTURES." Thesis, The University of Arizona, 1986. http://hdl.handle.net/10150/276659.
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Niakan, Negar. "Effects of Molecular Structure of the Oxidation Products of Reactive Atmospheric Hydrocarbons on the Formation of Secondary Organic Particulate Matter, Including the Effects of Water." PDXScholar, 2013. https://pdxscholar.library.pdx.edu/open_access_etds/617.
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Organic aerosols have significant effects on human health, air quality and climate. Secondary organic aerosols (SOA) are produced by the oxidation of primary-volatile organic compounds (VOC). For example, α-pinene reacts with oxidants such as hydroxyl radical (OH), ozone (O3), and nitrate radical (NO3), accounting for a significant portion of total organic aerosol in the atmosphere. Experimental studies have shown that the oxidation process between α-pinene and ozone has the most significant impact in the formation of SOA (Hoffmann et al., 1997). Most of the models used to predict SOA formation, however, are limited in that they neglect the role of water due to uncertainty about the structure and nature of organic compounds, in addition to uncertainty about the effect of varying relative humidity (RH) on atmospheric organic particulate matter (OPM) (Kanakidou et al., 2005). For this study, structures of organic compounds involved in the formation of SOA are estimated, and the role of water uptake is incorporated in the process. The Combinatorial Aerosol Formation Model (CAFM) is a deterministic model used to determine the amount of organic mass (Mo µg m-3) formation based on the predicted structures. Results show that the amount of SOA that is formed is almost negligible when the amount of parent hydrocarbon involved in the reaction is low (i.e. around 5 µg m-3), especially at lower RH. Observing compounds with a greater number of polar groups (alcohol and carboxylic acid) indicates that structure has a significant effect on organic mass formation. This observation is in agreement with the fact that the more hydrophilic the compound is, the higher RH, leading to more condensation into the PM phase.
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Howard, Angela L. "Strategies for the analytical determination of thermally labile sulfur-containing environmental pollutants." Diss., Virginia Tech, 1992. http://hdl.handle.net/10919/39291.
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Increasing public awareness of toxic moieties in our environment has put pressure on regulatory agencies to improve testing methods so that these harmful agents can be identified and quantitated at lower and lower levels. The main objective of this work was to investigate analytical methodologies that would allow the sensitive, selective determination of pollutants to be routinely possible. Polar, thermally labile sulfur-containing pesticides and pollutants were our focus analytes. This objective was achieved in two ways: 1) the development of supercritical fluid extraction procedures suitable for these compounds and 2) the interface of a sulfur-selective detector to chromatographic techniques appropriate for thermally labile compound analysis.
Supercritical fluids, particularly CO₂, have recently been shown to be suitable replacements for traditionally used organic solvents in extraction. However, due to the polarity of the sulfonyl urea herbicides and thiocarbamate insecticides studied, pure CO₂ was found to be an ineffective extractant. Polar SF mixtures (2 and 5 % methanol-modified CO₂) were investigated as alternative supercritical extraction fluids. Of the modified fluids, only 2% methanol-modified fluid could be used due to post-SFE trapping problems encountered with the 5% modified fluid. The quantitative extraction of two of these herbicides from water at the 50 ppb level was achieved using the former SF. This SF was also used to extract three thiocarbamates from apples at the 2 ppm level.
In order to achieve the second objective, a sulfur-selective gas chromatographic detector, the ozone-based sulfur chemiluminescence detector (SCD), was successfully interfaced to both packed column supercritical fluid chromatography (SFC) and microcolumn high performance liquid chromatography (micro-HPLC). The packed column SFC/SCD system was shown to be compatible with both pure CO₂ and methanolmodified CO₂ mobile phases with a detector sensitivity (2 pg S/sec.) comparable to that found with capillary SFC/SCD despite the presence of more CO₂, an effective chemiluminescence quenching agent. The equimolar response of this detector to sulfur was shown to be only somewhat affected by the coelution of other organic species and improper analyte combustion conditions. For micro-column HPLC/SCD, the detector was found to be compatible with methanol/water mobile phases. Mobile phase composition, mobile phase flow rate, air flow rate, and hydrogen flow rate were found to affect the detector's sensitivity. The detector's linear dynamic range, response factor, and detection limits were determined to vary as a function of mobile phase composition. Optimum sensitivity (600 fg S/sec.) was achieved with a mobile phase of 40% methano1l60% water mobile phase compositions investigated. The analysis of polyaromatic sulfur-containing hydrocarbons (PASH's), total sulfur in diesel fuel, and sulfonyl urea herbicides was realized with the SFC/SCD system while thiocarbamate pesticides from an apple matrix were examined with the HPLC/SCD system.Ph. D.
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曾志堅 and Chi-kin Tsang. "Analysis and control of organic vapours in air and determination of metals and toxic elements in fish samples by differential pulsevoltammetry and atomic absorption spectrophotometry." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1991. http://hub.hku.hk/bib/B31210995.
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Fagbayigbo, Bamidele Oladapo. "Perfluorooctane acid (PFOA) and perfluorooctane sulfonate (PFOS) in the Plankenburg (Stellenbosch) and Diep (Milnerton) Rivers, and potential remediation using vitis vinifera leaf litter." Thesis, Cape Peninsula University of Technology, 2017. http://hdl.handle.net/20.500.11838/2668.
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Thesis (DTech (Environmental Health))--Cape Peninsula University of Technology, 2017.This study represents the first monitoring campaign to assess the seasonal trend of nine perfluorinated compounds (PFCs) in surface water and sediment from the Plankenburg and Diep Rivers in the Western Cape, South Africa. An analytical protocol was developed and validated for qualitative and quantitative routine determination of nine perfluorinated compounds (PFCs), in water and sediment samples using Ultra performance liquid chromatography-mass spectrometry quadrupole time of flight (UPLC-QTOF-MS). This method was applied to determine levels of PFOA and PFOS in environmental samples. Samples were collected along the Diep (Milnerton) and Plankenburg (Stellenbosch) Rivers respectively. Samples were pre-treated, cleaned-up and extracted using solid-phase extraction (SPE) procedures with hydrophilic-lipophilic balance (HLB) C-18 cartridges. Seasonal variation and distribution of PFCs in surface water and sediment was also investigated. Levels of PFCs were monitored in four seasons (summer, autumn, winter and spring) to establish their trend in the environment. The removal of PFOA and PFOS from aqueous solutions using agro-waste biomass of Vitis vinifera (grape) leaf litter was also studied. Activated carbons were produced from the biomass and chemical activation achieved with phosphoric acid (H3PO4) and potassium hydroxide (KOH) for the modification of the carbons’ (AC-H3PO4 and AC-KOH respectively). Activated carbons were characterized using Fourier Transform infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), and Brunauer- Emmett-Teller (BET) in order to understand the removal mechanisms of the contaminants by activated carbons. The effects of solution concentration, pH, adsorbent dosage, contact time, and the temperature were optimized for evaluation of the removal efficiency of the activated carbons. Adsorption isotherm models were used to analyze the equilibrium data obtained and kinetic models were applied to study sorption mechanisms. A fixed bed column study was conducted using: AC-H3PO4 adsorbent. Experimental parameters such as initial concentration of the solution, column bed height, flow rate and initial concentrations of the influent were optimized to establish the best adsorption efficiency parameters of the column system. Breakthrough curve and exhaustion time were predicted using Adam-Bohart, Yoon-Nelson, and Thomas models for the fixed bed column under varying experimental conditions.
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Tezel, Ulas. "Fate and effect of quaternary ammonium compounds in biological systems." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/28229.
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Thesis (M. S.)--Civil and Environmental Engineering, Georgia Institute of Technology, 2009.Committee Chair: Pavlostathis, Spyros G.; Committee Member: Huang, Ching-Hua; Committee Member: Hughes, Joseph B.; Committee Member: Sobecky, Patricia A.; Committee Member: Spain, Jim C.
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Wutor, Victor Collins. "Development of a novel in situ CPRG-based biosensor and bioprobe for monitoring coliform β-D-Galactosidase in water polluted by faecal matter." Thesis, Rhodes University, 2008. http://hdl.handle.net/10962/d1004003.
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The ultimate objective of this work was to develop a real-time method for detecting and monitoring β-D-galactosidase as a suitable indicator of the potential presence of total coliform bacteria in water environments. Preliminary comparison of the chromogenic substrate, chlorophenol red β-D-galactopyranoside and the fluorogenic substrate, MuGAL, revealed unreliable results with the fluorogenic technique due to interference from compounds commonly found in environmental water samples. Thus, the chromogenic assay was further explored. Hydrolysis of the chromogenic substrate chlorophenol red β-D-galactopyranoside by β-D-galactosidase to yield chlorophenol red was the basis of this assay. Fundamental studies with chlorophenol red β-Dgalactopyranoside showed that β-D-galactosidase occurs extracellularly and in low concentrations in the polluted water environment. A direct correlation between enzyme activity and an increase in environmental water sample volume, as well as enzyme activity with total coliform colony forming unit counts were observed. Spectrophotometric detection was achieved within a maximum period of 24 h with a limit of detection level of 1 colony forming unit 100 ml[superscript -1]. This enzyme also exhibited physical and kinetic properties different from those of the pure commercially available β-D-galactosidase. Cell permeabilisation was not required for releasing enzymes into the extracellular environment. PEG 20 000 offered the best option for concentrating β-D-galactosidase. The source of β-D-galactosidase in the polluted environmental water samples was confirmed as Escherichia coli through SDS-PAGE, tryptic mapping and MALDI-TOF, thus justifying the further use of this method for detecting and/or monitoring total coliforms. Several compounds and metal ions commonly found in environmental water samples (as well as those used in water treatment processes) did have an effect on β-D-galactosidase. All the divalent cations except Mg [superscript 2+], at the concentrations studied, inhibited the relative activity of β-D-galactosidase in both commercial β-D-galactosidase and environmental samples. Immobilisation of chlorophenol red β-D-galactopyranoside onto a solid support material for the development of a strip bioprobe was unsuccessful, even though the nylon support material yielded some positive results. A monthly (seasonal) variation in β-Dgalactosidase activity from the environmental water samples was observed, with the highest activity coinciding with the highest monthly temperatures. Electro-oxidative detection and/or monitoring of chlorophenol red was possible. Chlorophenol red detection was linear over a wide range of concentrations (0.001-0.01 μg ml[superscript -1]). Interference by chlorophenol red β-D-galactopyranoside in the reduction window affected analysis. A range of phthalocyanine metal complexes were studied in an attempt to reduce fouling and/or increase the sensitivity of the biosensor. The selected phthalocyanine metal complexes were generally sensitive to changes in pH with a reduction in sensitivity from acidic pH to alkaline pH. The tetrasulphonated phthalocyanine metal complex of copper was, however, more stable with a minimum change of sensitivity. The phthalocyanine metal complexes were generally stable to changes in temperature. While only two consecutive scans were possible with the unmodified glassy carbon electrode, 77 consecutive scans were performed successfully with the CuPc-modified glassy carbon electrode. Among the phthalocyanine metal complexes studied, the CuPc-modified glassy carbon electrode therefore provided excellent results for the development of a biosensor. The CuPc modified-glassy carbon electrode detected 1 colony forming unit 100 ml[superscript -1] in 15 minutes, while the plain unmodified glassy carbon electrode required 6 hours to detect the equivalent number of colony forming units. CoPc, ZnPc and CuTSPc required 2, 2.25 and 1.75 h, respectively, to detect the same numbers of colony forming units. The CuPcmodified glassy carbon electrode detected 40 colony forming units 100 ml[superscript -1] instantly. In general, a direct correlation between colony forming units and current generated in the sensor was observed (R2=0.92). A higher correlation coefficient of 0.99 for 0-30 coliform colony forming units 100 ml[superscript -1] was determined. Current was detected in some water samples which did not show any colony forming units on the media, probably due to the phenomenon of viable but non-culturable bacteria, which is the major disadvantage encountered in the use of media for detecting indicator microorganisms. This novel biosensor therefore presents a very robust and sensitive technique for the detection and/or monitoring of coliform bacterial activity in water.
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Feng, Xiao Yi. "A survey of inorganic chemical pollution in the Bottelary River, Cape Town." Thesis, University of the Western Cape, 2005. http://etd.uwc.ac.za/index.php?module=etd&.
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Chemical pollution of freshwater is a worldwide environmental problemeutrophication, heavy metals and salinity are amongst the most widely used indicators of pollution. The aim of this study was to assess the status of nutrients, heavy metals and salinity, and the seasonal variation int he Bottelary River.
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Ehsan, Sadia. "Simultaneous mobilization of polychlorinated biphenyl compounds and heavy metals from a field contaminated soil." Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=100355.
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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.
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Alvarez-Dalama, Alina 1960. "CALCIUM-SULFITE HEMIHYDRATE CRYSTALLIZATION IN LIQUORS WITH HIGH TOTAL DISSOLVED SOLIDS (GROWTH, SIZE DISTRIBUTION, NUCLEATION, HABIT)." Thesis, The University of Arizona, 1986. http://hdl.handle.net/10150/275528.
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Brogdon, Brian N. "Effects of ethanol media on chlorine dioxide and extraction stages for kraft pulp bleaching." Diss., Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/7014.
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Poon, Tim-leung, and 潘添良. "Trace organic pollution in the indoor environment." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1993. http://hub.hku.hk/bib/B31252722.
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Wen, Yuan Hua. "Pharmacokinetic modeling of pollutant fluxes by limnoplankton." Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=34481.
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The objective of this thesis was to construct general models to predict pollutant fluxes in limnoplankton by incorporating characteristics of the organism and the structures of the chemical. A two-compartmental pharmacokinetic model was used to quantify the pollutant uptake, depuration and intercompartmental exchanges. The model pollutants were phosphorus and 22 organic chemicals.The rate constants of phosphorus uptake, excretion and intercompartmental changes by algae and cladocerans decreased with cell volume or body size raised to a power close to $-$0.25, except the intercompartmental exchanges for cladocerans which showed more negative slopes. In contrast, uptake, excretion and internal exchange rates per individual increased with cell size or body weight to a power similar to 0.75 with a similar exception for the cladoceran intercompartmental exchanges, which had slopes $<$0.75.
Bioconcentration factors, rate constants and flux rates of uptake and intercompartmental exchange from metabolic pool to structural pool of 22 $ sp{14}$C-labelled organic toxicants by Chlorella pyrenoidosa and Daphnia magna were positively correlated with the octanol/water partition coefficient, molecular weight, parachor, connectivity index, boiling point and melting point, and negatively with aqueous solubility. However, those of elimination and internal transfer from structural pool to metabolic pool showed opposite changes. Comparisons of pharmacokinetic parameters between Daphnia and Chlorella demonstrated that, although all kinetic parameters displayed similar patterns, the relative magnitudes of each corresponding parameters were significantly different between two species.
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Bigazzi, Alexander Y. "Bicyclists' Uptake of Traffic-Related Air Pollution: Effects of the Urban Transportation System." PDXScholar, 2014. https://pdxscholar.library.pdx.edu/open_access_etds/2064.
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While bicyclists and other active travelers obtain health benefits from increased physical activity, they also risk uptake of traffic-related air pollution. But pollution uptake by urban bicyclists is not well understood due to a lack of direct measurements and insufficient analysis of the determinants of exposure and ventilation (breathing). This knowledge gap impedes pollution-conscious transportation planning, design, and health impact assessment.
The research presented in this dissertation generates new connections between transportation system characteristics and pollution uptake by bicyclists. The primary research questions are: 1) how do urban bicyclists' intake and uptake of air pollution vary with roadway and travel characteristics and 2) to what extent can transportation-related strategies reduce uptake.
Breath biomarkers are used to measure absorbed doses of volatile organic compounds (VOCs). This research is the first application of breath biomarkers to travelers and the first uptake measurements of any pollutant to include roadway-level covariates. Novel methods to collect and integrate bicycle, rider, traffic, and environmental data are also introduced.
Bicyclist exposure concentrations, exhaled breath concentrations, respiratory physiology, and travel characteristics were collected on a wide range of facilities in Portland, Oregon. High-resolution trajectory and pollution data were then integrated with roadway and traffic data. Models of exposure, ventilation, and uptake of VOCs were estimated from the on-road data. Important new quantifications in the models include the effects of average daily traffic (ADT) on multi-pollutant exposure, the lagged effect of on-road workload on ventilation, and the effects of exposure and ventilation on absorbed VOCs.
Estimated models are applied to situations of interest to travelers and transportation professionals. Sample applications include the inhalation dose effects of road grade, cruising speed choice, stops, and detouring to parallel low-traffic facilities. In addition, dose-minimizing routing behavior is compared with revealed routing preferences in the literature. Finally, findings from this research and the literature are distilled so that they can be incorporated into bicycle network design guidelines.
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Neill, Holly Ann. "The Production of Organic Nitrates in Portland Oregon and the Columbia River Gorge." PDXScholar, 2013. https://pdxscholar.library.pdx.edu/open_access_etds/681.
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This work studied the production of aerosol-phase organic nitrates in both Portland and the Columbia River Gorge (CRG). Ozone and NOx species were investigated for correlation with organic nitrate aerosol, as they function as precursors to the production of organic nitrates. These ambient gas-phase measurements were collected in the same locations as high-volume (Hi-Vol) filters samples, in an urban and rural gorge setting to investigate correlations at the origin of the pollution plume and downwind. A novel Soxhlet extraction method for Hi-Vol filters was developed based on literature and EPA standard methods. Analysis for nitrate production was done by segregating data based on times when the wind blew out of Portland and down the CRG versus times when flow was not westerly. Filters were then compared to ambient gas-phase measurements and derived NO3 radical production rates to look for trends. Wind direction had a strong influence on the concentrations of precursor molecules in the CRG. On days with a westerly wind direction into the gorge, concentrations of the measure aerosol organic nitrates were similar at both sides. This suggests some contribution of a broader regional production of organic nitrates. There was some correlation between the production rate of NO3 radicals and the measured organic nitrate aerosol, suggesting a role for NO3 + VOC production of organic nitrates that later partition to the aerosol phase. This information will better illuminate the fate of nitrogen downwind of pollution sources. The information will also help to create a better understanding of the way topography and meteorological conditions can influence the flow of pollution. Understanding the downwind oxidative chemistry that happens in the CRG would better support both pollution prevention and mitigation efforts.
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Pellegrino-Peard, Patricia L. "A review of research and literature linking breast cancer to pesticides." CSUSB ScholarWorks, 1995. https://scholarworks.lib.csusb.edu/etd-project/1216.
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周厚華 and Donna Chaw. "Biochemical changes in the fermentation bedding of the "pig-on-litter"method of pig farming: with special emphasison biodegradation of nitrogen compounds and odour production." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1996. http://hub.hku.hk/bib/B43893740.
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Manipura, Walappuly Mudiyanselage Janakasiri Aruna Shantha Bandara. "Bioprocess development for removal of nitrogenous compounds from precious metal refinery wastewater." Thesis, Rhodes University, 2008. http://hdl.handle.net/10962/d1007341.
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Removal of nitrogenous compounds from precious metal refinery (PMR) wastewater is important in terms of avoiding eutrophication (environmental protection), metal recovery (increased overall process efficiency and value recovery) and reuse of treated water (maximum use of natural resources). Extreme pH conditions (4 to 13 depending on the wastewater stream), high chemical oxygen demand (> 10,000 mg/I), numerous metals and high concentrations of those metals (> 20 mg/l of platinum group metals) in the wastewater are the main challenges for biological removal of nitrogenous compounds from PMR wastewater. Nitrogenous compounds such as NH₄⁺-N and N0₃-N are strong metal ligands, which make it difficult to recover metals from the wastewater. Therefore, a bioprocess was developed for removal of nitrogenous compounds from carefully simulated PMR wastewater. A preliminary investigation of metal wastewater was carried out to determine its composition and physico-chemical properties, the ability to nitrify and denitrify under different pH conditions and denitrification with different carbon Source compounds and amounts. Even at pH 4, nitrification could be carried out. A suitable hydraulic retention time was found to be 72 hours. There was no significant difference between sodium acetate and sodium lactate as carbon sources for denitrification. Based on these results, a reactor comparison study was carried out using simulated PMR wastewater in three types of reactors: continuously stirred tank reactor (CSTR), packed-bed reactor (PBR) and airlift suspension reactor (ALSR). These reactors were fed with 30 mg/l of Rh bound in an NH₄⁺ based compound (Claus salt: pentaaminechlororhodium (III) dichloride). Total nitrogen removal efficiencies of > 68 % , > 79 % and > 45 % were obtained in the CSTR, PBR and ALSR, respectively. Serially connected CSTR-PBR and PBR-CSTR reactor configurations were then studied to determine the best configuration for maximum removal of nitrogenous compounds from the wastewater. The PBR-CSTR configuration gave consistent biomass retention and automatic pH control in the CSTR. Ammonium removal efficiencies > 95 % were achieved in both reactors. As poor nitrate removal was observed a toxicity study was carried out using respirometry and the half saturation inhibition coefficients for Pt, Pd, Rh and Ru were found to be 15.81, 25.00, 33.34 and 39.25 mg/l, respectively. A mathematical model was developed to describe the nitrogen removal in PMR wastewater using activated sludge model number 1 (ASMl), two step nitrification and metal toxicity. An operational protocol was developed based on the literature review, experimental work and simulation results. The optimum reactor configuration under the set conditions (20 mg/I of Rh and < 100 mg/I of NH₄⁺-N) was found to be PBR-CSTR-PBR process, which achieved overall NH₄⁺-N and N0₃⁻-N removal efficiencies of > 90 % and 95 %, respectively. Finally, a rudimentary microbial characterisation was carried out on subsamples from the CSTR and PBRsecondary. It was found that the CSTR biomass consisted of both rods and cocci while PBRsecondary consisted of rods only. Based on these experimental works, further research needs and recommendations were made for optimisation of the developed bioprocess for removal of nitrogenous compounds from PMR wastewater.
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Pawlisz, Andrew V. "Internal residues of the narcotic organic chemicals in the Cladoceran, Daphnia magna." Thesis, McGill University, 1993. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=69519.
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The current work determined whether there is a constant tissue residue associated with narcotic compounds. In this investigation, the cladoceran, Daphnia magna was exposed to lethal levels (48h LC50) of ten, $ sp{14}$C-labelled, narcotic organic chemicals in a closed system. Exposure times, ambient concentrations, and body sizes were varied to evaluate their effects. The $ sp{14}$C-method developed in current work can detect chemicals in single D. magna in concentrations ranging from 0.02 to 6310 mmol/kg. Moreover, the technique detected phobic and lipophilic chemicals equally well. The technique's sensitivity (nmol/kg) allowed for detection of differences in the internal concentrations of pollutants among the unaffected, immobilized, and dead D. magna. Immobilized D. magna contained between 0.14 mmol/kg and 200 mmol/kg of narcotics. On the average, however, the internal residues were 3.1 mmol/kg (95%CL = 3.1 $ pm$ 2.0). This agreed with literature values. The effects of time of exposure, ambient concentration, and body size on the tissue residues of narcotics varied with the chemical compound.
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Glas, Bo. "Methodological aspects of unspecific building related symptoms research." Doctoral thesis, Umeå : Institutionen för folkhälsa och klinisk medicin, Umeå universitet, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-30640.
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Dolan, Bianca Christine. "Effects of Increased Nitrogen Deposition on the Dominance of Hedera helix in the Pacific Northwest." PDXScholar, 2013. https://pdxscholar.library.pdx.edu/open_access_etds/680.
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Increased nitrogen deposition has been shown to promote the dominance of invasive species, and nitrogen deposition rates have steadily increased in most of the Western United States in recent years due to population increases. The purpose of this study was to determine if increased rates of nitrogen deposition are contributing to the success of Hedera helix in the Pacific Northwest. Plots were established in Lesser Park in Portland, Oregon and received monthly treatments of ammonium nitrate for one year. Growth, measured as change in percent cover, was compared between treated and untreated plots for both H. helix and native species. Additionally, a greenhouse experiment was employed wherein H. helix was grown in shared pots with two native species, Fragaria vesca and Polystichum munitum, and three treatment levels were compared; none, low, and high nitrogen. Relative growth rate was compared between treatments for each species after twelve weeks of treatment. Results from the greenhouse experiment were highly variable and no general conclusions could be drawn about the effects of increased nitrogen deposition on competition between H. helix and native species. In the field, treatment did not have a significant effect on growth but species did have a significant effect, as H. helix had a greater increase in percent cover than native species regardless of treatment. However, a marginally significant interaction was found between species and treatment. Native species cover actually increased in plots that received nitrogen addition and decreased in control plots, while H. helix had a slightly higher increase in cover in control plots. Though the growth of H. helix was significantly higher than the growth of native species in control plots, nitrogen addition caused the growth rates to converge towards more similar means in treated plots. Results indicate that increased nitrogen deposition may actually have a positive effect on the growth of native species by reducing the invasive potential of H. helix.
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Matin, Maleeha. "A study of the impact of unconventional sources within a large urban area: evidence from spatio-temporal assessment of volatile organic compounds." Thesis, University of North Texas, 2016. https://digital.library.unt.edu/ark:/67531/metadc849645/.
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Conventional sources of emissions have been a prime target for policymakers in designing pollution control strategies. However, the evolution of shale gas activities is a growing concern over the impact of unconventional sources on urban and regional air quality. Owing to the development of Barnett Shale production, the fast-growing Dallas-Fort Worth (DFW) metroplex has encountered both types of these emissions. Oil and gas activities result in emissions of ozone precursors, notably volatile organic compounds (VOC). The major objective of this study was to evaluate the spatio-temporal distribution of VOC in order to highlight the influence of unconventional emissions. The study utilized measurements from automated gas chromatography (AutoGC) monitors to analyze the patterns of the total non-methane organic compounds (TNMOC) and relative contributions from marker species of traffic versus oil and gas activities. In this study, data from 2001-2014 was obtained from the Texas Commission on Environmental Quality (TCEQ) for fifteen monitoring sites within the North Texas region. With over a thousand wells in a 10 mile radius, two of the rural sites measured twice as much TNMOC as compared to the urban site in Dallas. Source apportionment analysis was conducted using Positive Matrix Factorization (PMF) technique. The target site located in the urban zone resolved an eight factor model. Natural gas signature was the dominant source of emission with a 52% contribution followed by 31% from two separate traffic-related sources. Considering ethane to be the dominant species in oil and gas emissions, it was observed that the rising ethane/NOx ratio correlated with increasing annual average ozone post-2007. In this period, higher concentration of ozone was found to be associated with stronger winds from the Barnett Shale area – a region that did not seem to contribute to high ozone during 2001-2007. With traffic emissions having flattened over the years, the recent increase in oil- and gas-related emissions has a negative impact on the air quality in this area. Results indicate that the area has failed to observe a declining trend in ozone despite effective reductions in NOx and traffic-related VOC emissions. The findings of the study would be helpful in proper evaluation of the ozone-forming potential of unconventional VOC emissions. Although these emissions may not be strong enough to cause harm through direct exposure, underestimating their potential towards ozone formation could hinder the progress in ozone attainment in growing urban areas. After all, a major portion of the study area continues to be in nonattainment of the EPA designated ozone standards. The study therefore draws the attention of policymakers towards the new influx of emissions that have emerged as a powerful source within the DFW metropolitan area.
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Roskamp, Melissa Jordan. "Characterization of Secondary Organic Aerosol Precursors Using Two-Dimensional Gas Chromatography with Time of Flight Mass Spectrometry (GC×GC/TOFMS)." PDXScholar, 2013. https://pdxscholar.library.pdx.edu/open_access_etds/1411.
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The oxidation of volatile organic compounds (VOCs) plays a role in both regional and global air quality through the formation of secondary organic aerosols (SOA). More than 1000TgC/yr of non-methane VOCs are emitted from biogenic sources (significantly greater than from anthropogenic sources). Despite this magnitude and potential importance for air quality, the body of knowledge around the identities, quantities and oxidation processes of these compounds is still incomplete (e.g., Goldstein & Galbally, 2007; Robinson et al., 2009). Two-dimensional gas chromatography paired with time-of-flight mass spectrometry (GC×GC/TOFMS) is a powerful analytical technique which is explored here for its role in better characterizing biogenic VOCs (BVOCs) and thus SOA precursors.
This work presents measurements of BVOCs collected during two field campaigns and analyzed using GC×GC/TOFMS. The first campaign, the Bio-hydro-atmosphere Interactions of Energy, Aerosols, Carbon, H2O, Organics & Nitrogen - Rocky Mountain Biogenic Aerosol Study (BEACHON-RoMBAS), took place in a Ponderosa pine forest in Colorado. The second campaign, Particle Investigations at a Northern Ozarks Tower: NOx, Oxidant, Isoprene Research (PINOT NOIR) Study, was conducted in the Ozark region of Missouri. Tens to hundreds of BVOCs were quantified in each set of samples, including primary emissions, atmospheric oxidation products, stress indicators and semi-volatile leaf surface compounds. These findings highlight that there is a largely uncharacterized diversity of BVOCs in ambient samples. Our findings demonstrate that GC×GC can distinguish between compounds with the same molecular weight and similar structures, which have highly variable potentials for production of SOA (Lee et al., 2006). This work represents some of the first analysis of ambient BVOCs with this technology, which is anticipated to contribute greatly to characterization of atmospheric SOA precursors and ultimately, regional and global modeling of SOA and fine particulate matter.
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Thompson, Laura M. "The depletion of nitric oxide by reaction with molten sodium carbonate and sodium carbonate/sodium sulfide mixtures." Diss., Georgia Institute of Technology, 1995. http://hdl.handle.net/1853/5797.
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Sattar, Mohamed Shaheen. "An environmental impact perspective of the management, treatment, and disposal of hazardous pharmaceutical compounds generated as medical waste at selected hospitals in Cape Town, South Africa." Thesis, Cape Peninsula University of Technology, 2011. http://hdl.handle.net/20.500.11838/2012.
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Thesis (MTech (Environmental Health))--Cape Peninsula University of Technology, 2011.Pharmaceuticals have been formulated to influence physiological systems in humans, animals, and microbes but have never been considered as potential environmental pollutants by healthcare professionals. The human body is not a barrier to chemicals, but is permeable to it. Thus after performing their in-vivo functions, pharmaceutical compound introduced into the body, exit mainly via urine and faeces. Sewage therefore contains highly complex mixtures of chemicals in various degrees of biological potency. Sewage treatment works including those in South Africa, on the other hand, are known to be inefficient in removing drugs from sewage and consequently either the unmetabolised pharmaceutical compounds or their metabolites emerge in the environment as pollutants via several trajectories. In the environment, the excreted metabolites may even undergo regeneration to the original parent molecule under bacterial influence, resulting in "trans-vivo-pharmaceutical-pollution-cycles". Although all incinerators are known to generate toxins such dioxins and furans from the drugs they incinerate, all the medicines disposed by the hospitals under research, were incinerated, as the preferred option of disposal. The incineration process employed was found to be environmentally unsafe. Expired and unused medicines which the general public discard as municipal solid waste become landfilled. Because many landfill sites are not appropriately engineered, the unwanted drugs landfilled therein, leach into the surrounding ground water, which is the influent source of water treatment plants. Water treatment plants, including those in South Africa, are also inefficient in eliminating pharmaceutical compounds, releasing them in sub-therapeutic concentrations into potable tap water as pollutants, the full effects of which are yet to be determined.