Most Aphidinae species produce and use (E)-ß-farnesene (Eßf) as an alarm pheromone. This sesquiterpene is released by individuals under attack by a predator, and nearby aphids exhibit a variety of alarm behaviours. This PhD thesis aims to better understand how aphids manage their production and emission of alarm pheromone (Chapter IV). We also wanted, in a second step, to improve our knowledge on the roles that Eßf could play in the relationships that aphids have with their predators (Chapter V) and tending ants (Chapter VI), in order to better pinpoint the problem in this very tough context. The aphid predators have indeed a real advantage to be able to use the odorant cues emitted by their prey, to locate them and to select an adequate oviposition site. Ants establish with certain aphid species mutualistic relationships, which occurrence could be facilitated by the use of aphids odours. In Chapter IV, we have highlighted that aphid colonies non subjected to attack by predators release constantly small quantities of Eßf in their headspace, which means that this molecule could have additional roles than just acting as an alarm pheromone. In a second study, we demonstrated that the release of Eßf was not contagious, and therefore that a non stressed aphid receiving the alarm signal does not release additional Eßf. Since the production of alarm pheromone is likely to entail physiological cost, we tested and validated the hypothesis that aphids regulate their Eßf production according to their social environment. In Chapter V, we studied the ability of the hoverfly predator Episyrphus balteatus (Diptera, Syrphidae) to be used as biological control agent against aphids infesting tomato plants (Lycopersicon esculentum). After identifying the odours emitted by aphid infested plants, we have demonstrated that although this Diptera is able to perceive all the odours released by the system, it mainly uses Eßf to select its oviposition site. However, the E. balteatus larvae are not adapted to the architecture of tomato plants. We also showed that the Asian ladybeetle Harmonia axyridis (Coleoptera, Coccinellidae) olfaction was adapted to the perception of Eßf and that this beetle is also attracted by this sesquiterpene. Finally, in Chapter VI, we characterized the benefits accruing to aphid populations that have established mutualistic relationships with Lasius niger (Hymenoptera, Formicidae), and have demonstrated the role of Eßf and honeydew, respectively in locating aphid colonies and in the persistence of the mutualism. La plupart des espèces de pucerons appartenant à la sous-famille des Aphidinae produisent et utilisent le (E)-ß-farnésène (Eßf) comme phéromone dalarme. Ce sesquiterpène est relargué par les individus stressés par lattaque dun prédateur et cause chez les individus qui le perçoivent un comportement dalerte. La présente thèse de doctorat a pour objectif de comprendre comment les pucerons gèrent la production et émission de phéromones dalarme (Chapitre IV). Nous voulions aussi, dans une seconde étape, améliorer les connaissances sur les rôles potentiels que cet Eßf peut jouer au sein des relations que les pucerons entretiennent avec leurs prédateurs (Chapitre V) et avec les fourmis (Chapitre VI) Les prédateurs de pucerons retirent en effet un réel avantage à pouvoir saider des odeurs émises par leurs proies pour les localiser et pour sélectionner un site doviposition adéquat. Les fourmis, quant à elles, établissent des relations de mutualisme avec certaines espèces de pucerons. Les rencontres entre fourmis et pucerons pourraient être facilitées par lutilisation des odeurs de pucerons. Les résultats obtenus peuvent être résumés de la manière suivante: Dans le chapitre IV, nous avons mis en évidence que les colonies de pucerons non soumises à lattaque de prédateurs relarguent constamment de faibles quantités dEßf, ce qui permet dassumer que cette molécule puisse avoir dautres fonctions que celle de phéromone dalarme. Dans une deuxième étude, nous avons démontré que lémission du Eßf nétait pas contagieuse, et donc quun puceron non stressé percevant le signal dalarme német pas à son tour de le Eßf. Puisque la production de phéromone dalarme a inévitablement un coût physiologique, nous avons testé et validé lhypothèse selon laquelle les pucerons régulent leur production de Eßf en fonction de leur environnement social. Dans le chapitre V, nous avons étudié la possibilité dutiliser le syrphe prédateur Episyrphus balteatus (Diptera, Syrphidae) en lutte biologique contre les pucerons infestant les plants de tomate (Lycopersicon esculentum). Après avoir identifié les odeurs émises par les plants infestés, nous avons démontré que, si ce Diptère est capable de percevoir lensemble des odeurs émises par ce système tritrophique, il utilise principalement lEßf pour sélectionner son site doviposition. Cependant, les larves dE. balteatus ne sont pas adaptées à larchitecture des plants de tomate. Nous avons également montré que la coccinelle asiatique Harmonia axyridis (Coleoptera, Coccinellidae) possède le matériel olfactif nécessaire à la perception du Eßf et quelle est aussi attirée par ce sesquiterpène. Enfin, dans le chapitre VI, nous avons caractérisé les bénéfices retirés par les populations de pucerons ayant établi des relations de mutualisme avec Lasius niger (Hymenoptera, Formicidae), et avons démontré le rôle du Eßf et du miellat, respectivement dans la localisation des colonies de pucerons et dans la persistance du mutualisme.

Kyrock is a coarse grained sandstone with a complex mixture of organic and inorganic compounds. Mining of Kyrock is for use in road construction and roofing. Kyrock samples were analyzed using scanning electron microscopy to obtain elemental analysis. High levels of carbon indicate the presence of organic compounds. Analysis of an acid digestion of the samples using inductively coupled plasma spectroscopy showed inorganic compounds such as titanium oxide, vanadium oxide along with traces of arsenic. Elemental analysis of samples indicates a percent of carbon, and sulfur with no notable traces of nitrogen. Pyrolysis of the samples was done using gas chromatography mass spectroscopy with a gradual increase in temperature to 160o C resulted in the release of inorganic and organic compounds. Synthetic rainwater was prepared to examine the leaching of compounds and the leachate was analyzed using liquid chromatography mass spectroscopy and gas chromatography mass spectroscopy.

Thesis (Ph. D.)--University of Canterbury, 2009. / Typescript (photocopy). "16 September 2009." Includes bibliographical references (p. [217]-222). Also available via the World Wide Web.

Source: Masters Abstracts International, Volume: 47-06, page: 3475. Adviser: Thomas H. Stock. Includes bibliographical references.

M.Sc. (Chemistry) / Volatile fatty acids (VFAs) play a pivotal in the process of nutrient removal by biological processes particularly the enhanced biological nutrient removal process with a side-stream elutriation process using activated sludge. These acids are said to act as intermediates which provide feed for the organisms in a biological phosphorus and nitrogen removal (BNPR) system, such as phosphorus-accumulating organisms (PAOs) and nitrate-accumulating bacteria (NABs). In wastewater treatment plants, VFAs play a vital role as intermediate organic compounds during the fermentation processes which generate methane gas and when present at elevated levels they are known to cause microbial stress, acidification as well as the poor performance of anaerobic digesters. For these reasons, the routine monitoring of VFA levels in wastewater treatment plants is crucial as they will act as indicators of the efficiency and optimal operation performance of the anaerobic digesters. Normally the VFAs that are commonly produced during the anaerobic fermentation process include acetic acid, propionic acid, butyric acid, and valeric acid and of these, acetic and propionic acids form the major VFAs that are generated, thus the yields of these two compounds provide a useful measure of the anaerobic digester performance. For example, the ratio of propionic acid to acetic acid is always used as an indicator of digester imbalance while high concentrations of acetic acid (e.g. > 800 mg/ℓ) or a propionic acid to acetic acid ratio greater than 1.4 is an indication of digester failure. This study was thus aimed at establishing the complete VFA profile at the Johannesburg Water (JW) Northern Works Wastewater Treatment Plant in Johannesburg, South Africa, by developing analytical methods to quantify the VFAs in the wastewater treatment plant. In addition, the level of VFAs quantified was used to evaluate the efficiency of the fermentation treatment process in wastewater treatment systems in order to give an indication of the bacterial activities in the systems; to determine the ratios of the VFAs, especially the propionic acid to acetic acid ratio, to establish the performance and efficiency of various wastewater treatment plants; and to determine whether there is any imbalance in the anaerobic digesters. Two analytical methods for the determination of VFAs were successfully developed and applied to real wastewater samples. The first method developed was a liquid-liquid extraction method using gas chromatography time-of-flight mass spectrometry (GC-TOF-MS. The method involved two extracting solvents, namely dichloromethane (DCM) and methyl-tert-butyl ether (MTBE). The extraction capacity of these two solvents was compared. The second method successfully developed and optimised headspace-solid phase microextraction (HS-SPME) using GC-TOF-MS. The microextraction fibre used was a polydimethylsiloxane (PDMS) fibre. Studies to validate the developed methods were also carried out by calculating the limit of detection (LOD) and limit of quantification (LOQ). Ratios of propionic acid to acetic acids were determined as well as the concentrations of acetic acid for both developed methods in order to evaluate the performance and efficiency of the treatment process. The results of the study show that the extraction procedure using solvents DCM and MTBE showed that exhaustive extraction was achieved by MTBE. Higher concentrations of acetic acid and propionic acid were obtained by MTBE. The overall fermentation performance for all three units in the period when the samples were collected, which was measured by the ratio of propionic to acetic acid was good since the ratio did not exceed 1.4. The acetic acid concentration in mg/ℓ was < 800 mg/ℓ for all units thus it can be said that the reactor balance was maintained for the period studied. The method LOD ranged from 0.034 mg/ℓ to 0.21 mg/ℓ and the method LOQ ranged from 0.11 mg/ℓ to 0.70 mg/ℓ. Optimisation of extraction parameters was achieved for headspace solid-phase microextraction using the PDMS fibre method. The extraction method was conducted for 60 min using a sample volume of 4 mℓ and the amount of sodium salt added was 1.50 g. The desorption temperature and time was 210ºC and 5 min, respectively. The LOD values ranged from 0.079 to 2.07. The PDMS fibre was found to be suitable for extracting higher carbon chain fatty acids as compared to lower carbon chain fatty acids. The plant performance for the period studied was on par as indicated by ratios of propionic acid to acetic acid which all fell below 1.4. There were no digester failures for the period studied. The acetic acid concentration in mg/ℓ was < 800 mg/ℓ for all 3 units.

The determination of carbon monoxide is also possible by trapping CO on preconditioned molecular sieve and thermal desorption. Analysis in this case is performed by gas chromatography/mass spectroscopy, although the trapping technique is applicable to other suitable GC techniques.

Volatile organic compounds (VOCs) and semi-volatile organic compounds (SVOCs) constitute important classes of indoor contaminants. Emissions of VOCs and SVOCs from myriad building materials and consumer products cause high indoor concentrations with health risks that may be orders-of-magnitude greater than outdoors. The need to control VOC and SVOC emissions from interior materials and thereby reduce indoor concentrations is made more urgent by the prevailing drive for air-tight, energy efficient buildings. To develop low-emission products, emission rates are usually measured in emission chambers. However, there are three significant problems associated with chamber tests: (1) VOC emissions testing procedures of individual laboratories are frequently subject to error and uncertainty; (2) SVOC emissions testing in chambers is extremely difficult and time-consuming, and also subject to error and uncertainty; and (3) chamber tests provide little insight into the mechanisms controlling emissions. This research aimed to solve these problems by developing reference materials for VOC and SVOC emissions testing. Formaldehyde was studied separately from other VOCs because of its unusual properties. Emission mechanisms, and the related modeling approaches for predicting emissions, were investigated by reviewing the literature and performing chamber studies. Based on the internally controlled VOC and formaldehyde emission mechanisms, diffusion-controlled reference materials, which mimic real sources, were created for VOCs and formaldehyde. Approaches for developing externally controlled reference materials for SVOC emissions testing were also explored. Appropriate mechanistic models can predict the true emission rates of the reference materials and therefore provide reference values to validate emissions testing results and certify procedures of individual laboratories. The potential of a solid phase microextraction (SPME) method was also evaluated and found to be a promising technique that can be used in chamber tests to simplify and improve sampling and analytical procedures. This research elucidates the mass-transfer mechanisms of VOC and SVOC emissions and provides practical approaches for developing reference materials for emissions testing. The fundamental understanding and methodological advances will enhance indoor air quality science, improve the emissions testing industry, and provide a sound basis on which to develop standards and regulations. / Ph. D.

The United States Environmental Protection Agency has estimated that over 111 million people reside in areas that exceed the National Ambient Air Quality Standards for ozone. One major source of the chemical precursors (nitrogen dioxides and volatile organic compounds (VOCs)) for ozone are motor vehicles. The overall goal of this research is to improve the knowledge base related to VOC refueling and evaporative emissions from motor vehicles. Refueling, running loss, hot soak, and diurnal loss total and speciated VOC emissions were investigated. A total of 12 uncontrolled refueling events were completed and involved the determination of volumetric flow rates of gasoline vapor during refueling, as well as total and speciated VOC concentrations. Total VOC emissions were compared with two commonly used algorithms. Speciated VOC vapor profiles were compared with two published gasoline vapor profiles and theoretical predictions based on knowledge of liquid composition and environmental conditions. An evaluation of refueling emissions impacts on ozone formation potentials using MIR was completed and results were compared against speciated emissions and MOBILE-based total VOC emissions estimates coupled with a default speciation profile. Refueling VOC emissions and resultant ozone formation potential may be underestimated in existing emission inventories, particularly during the summer ozone season, A model was developed to predict the speciation of VOCs associated with evaporative emissions from motor vehicles. Model-predicted speciation profiles were evaluated using SHED studies. Running loss, hot soak and diurnal emissions were included in each test. Total VOC emissions measured during each test were compared against MOBILE6 predicted emissions. An evaluation of evaporative emissions impacts on ozone formation potentials using MIR was completed, comparing measured and predicted emissions. The measured:predicted speciation results ranged between 0.93 and 1.11 and had an average value of 1.02. For the conditions tested, MOBILE6 underestimated evaporative emissions in 20 of 24 comparisons. MOBILE6-based ozone formation potentials may be underestimated.

The objectives of this work are related to the kinetic study and characterization of air treatment biofilters with and without percolation which were packed with inert packing materials in order to treat methanol, ethanol and toluene vapours.The thesis is divided into three sections.The first section contains a bibliographic introduction to biofiltration and an experimental study.The review of experimental work shows that methanol, ethanol and toluene can be treated in biofilters with or without percolation. In the experimental study of this section, ethanol is treated in a biotrickling filter at low nitrogen concentrations in the nutrient solution and high removal efficiencies are obtained. In this study, experimental protocols for maintaining the biofilter and controlling the biomass content in the packing bed were developed.The second section is composed of two experimental studies for characterizing biofilters with and without percolation in order to treat methanol. A methodology for calculating the biomass accumulated in the packing bed of a biofilter is among the new experimental protocols developed in this study. In the case of biotrickling filter, methodologies for determining the partition coefficient of methanol and the biomass production rate were developed.The role of the biofilm and the nutrient solution on bioflter performance was also analyzed.The studies of this section lead to a better comprehension of methanol biodegradation in biofilters.The third section contains two kinetic studies for biofilters with and without percolation. In the first study, a new experimental methodology is proposed to calculate microkinetic parameters related to microbial growth in a biofilter. In the second study, the microkinetic and macrokinetic behaviors of methanol and toluene biodegradation are compared.The influence of operating conditions on microbial growth and elimination capacity is also analyzed. This study includes the identification of energy indicators of biofilters with and without percolation, which could be used in energy balances and for estimating the temperature of packing bed.

published_or_final_version / Chemistry / Master / Master of Philosophy