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

Thesis (MTech (Horticulture))--Cape Peninsula University of Technology, 2018. / Global demand for environmentally-friendly grapevine cultivation and pest control has necessitated an improved understanding of the relationship between soil properties and beneficial naturally occurring antagonists like entomopathogenic fungi (EPF). This group of fungi presents a viable alternative for the control of destructive pests such as the grapevine mealybug. Sixty-six soil samples were collected from 22 vineyards in the Western Cape, South Africa. The association between soil nutrient status and EPF prevalence was then examined. Fungi were isolated with methods of insect baiting and selective media. Fungal strains were identified and characterized using light microscopy and DNA analysis (ITS and BTub). In addition, fungal isolates were tested against a key grapevine pest, Planococcus ficus (Signoret) (Hemiptera: Pseudococcidae) using an immersion bioassay at a concentration of 1 x 108 conidia ml-1. Twenty-three fungal strains were isolated and correspondence analysis (CA) of data indicated a positive association between fungal occurrence and moderate to high levels of soil-based macronutrients. Binomial logistic regression analysis revealed that soil N, K, Ca, Mg and S concentrations and C/N ratio were correlated with at least one EPF species. This study showed that some soil nutrient properties correspond to greater occurrence of EPF in grapevine soils. Strains of Beauvaria bassiana (Hypocreales: Clavicipitaceae) caused the highest mortalities (82% to 87%). In chapter three, I examined the effect of B. bassiana inoculation of grape plants on the infestation level of P. ficus, and the growth and volatile constituents of potted grape plants. The grapevines were inoculated with 1 x 108 conidia ml-1 of B. bassiana by drenching before experimentally infesting them with thirty P. ficus adult females. At four weeks post treatments, the fungus was re-isolated from leaves of 50% of the fungus exposed plants. No significant difference (P > 0.05) was observed in all the plant growth parameters measured in the fungus treated and control plants. Plant tissue analysis revealed markedly higher contents of Ca and Mg in leaf tissue of plants exposed to the B. bassiana relative to the control. GC-MS analyses showed that a significantly (X2=5.1; P<0.02) higher number of known anti-insect volatile compounds (9) including napthtalene were present among fungus treated plants compared to the control plants (5). However, B. bassiana did not have any significant effect on total polyphenol, alkaloid and flavonoids. Overall, treatment with fungus did not offer any protection against infestation of P. ficus. In conclusion, this is the first study to report on the isolation of indigenous entomopathogenic fungal (EPF) strains within vineyards of the Western Cape. The study revealed that inoculating grapevine plants during cultivation had a net positive effect on the production of volatile compounds in grapevines. These findings shed light on the mechanisms involved in endophytic fungus-plant-insect interactions. This study contributes valuable information to future development of ecological approaches involving EPF for insect control in vineyards and in general, agricultural settings.

Atmospheric formaldehyde (H2CO) is an intermediate product common to the degradation of many volatile organic compounds and therefore it is a central component of the tropospheric chemistry. While the global formaldehyde background is due to methane oxidation, emissions of non-methane volatile organic compounds (NMVOCs) from biogenic, biomass burning and anthropogenic continental sources result in important and localised enhancements of the H2CO concentration. Recent spaceborne nadir sensors provide an opportunity to quantify the abundance of tropospheric formaldehyde at the global scale, and thereby to improve our knowledge of NMVOC emissions. This is essential for a better understanding of the processes that control the production and the evolution of tropospheric ozone, a key actor in air quality and climate change, but also of the hydroxyl radical OH, the main cleansing agent of our troposphere. For this reason, H2CO satellite observations are increasingly used in combination with tropospheric chemistry transport models to constrain NMVOC emission inventories in so-called top-down inversion approaches. Such inverse modelling applications require well characterised satellite data products consistently retrieved over long time periods. This work reports on global observations of formaldehyde columns retrieved from the successive solar backscatter nadir sensors GOME, SCIAMACHY and GOME-2, respectively launched in 1995, 2002 and 2006. The retrieval procedure is based on the differential optical absorption spectroscopy technique (DOAS). Formaldehyde concentrations integrated along the mean atmospheric optical path are derived from the recorded spectra in the UV region, and further converted to vertical columns by means of calculated air mass factors. These are obtained from radiative transfer simulations, accounting for cloud coverage, surface properties and best-guess H2CO profiles, the latter being derived from the IMAGES chemistry transport model. A key task of the thesis has consisted in the optimisation of the H2CO retrieval settings from multiple sensors, taking into account the instrumental specificities of each sounder. As a result of these efforts, a homogeneous dataset of formaldehyde columns covering the period from 1996 to 2010 has been created. This comes with a comprehensive error budget that treats errors related to the spectral fit of the columns as well as those associated to the air mass factor evaluation. The time series of the GOME, SCIAMACHY and GOME-2 H2CO observations is shown to be consistent and stable over time. In addition, GOME-2 brings a significant reduction of the noise on spatiotemporally averaged observations, leading to a better identification of the emission sources. Our dataset is used to study the regional formaldehyde distribution, as well as its seasonal and interannual variations, principally related to temperature changes and fire events, but also to anthropogenic activities. Moreover, building on the quality of our 15-year time series, we present the first analysis of long-term changes in the H2CO columns. Positive trends, in the range of 1.5 to 4% yr-1, are found in Asia, more particularly in Eastern China and India, and are related to the known increase of anthropogenic NMVOC emissions in these regions. Finally, our dataset has been extensively used in several studies, in particular by the BIRA-IASB modelling team to constrain NMVOC emission fluxes. The results demonstrate the high potential of satellite data as top-down constraint for biogenic and biomass burning NMVOC emission inventories, especially in Tropical ecosystems, in Southeastern Asia, and in Southeastern US. / Le formaldéhyde (H2CO) joue un rôle central dans la chimie de la troposphère en tant que produit intermédiaire commun à la dégradation chimique de la plupart des composés organiques volatils dans l’atmosphère. L’oxydation du méthane est responsable de plus de la moitié de la concentration moyenne globale du formaldéhyde. Sur les continents en revanche, les hydrocarbures non-méthaniques (NMVOCs) émis par la végétation, les feux de biomasse et les activités humaines, augmentent de façon significative et localisée la concentration de H2CO. Les récents senseurs satellitaires à visée nadir offrent la possibilité de quantifier à l’échelle globale l’abondance du formaldéhyde dans la troposphère et de ce fait, d’améliorer notre connaissance des émissions de NMVOCs. Ceci est essentiel à la compréhension des mécanismes contrôlant la production et l’évolution de l’ozone troposphérique, élément clé pour la qualité de l’air et les changements climatiques, mais aussi du composé hydroxyle OH, le principal agent nettoyant de notre troposphère. C’est pourquoi, une méthode de plus en plus répandue pour améliorer les inventaires d’émissions des NMVOCs consiste en l’utilisation d’observations satellitaires de H2CO en combinaison avec un modèle de chimie et de transport troposphérique, dans une approche appelée modélisation inverse. Ce genre d’application demande des produits satellitaires bien caractérisés et dérivés de façon cohérente sur de longues périodes de temps. Le travail présenté dans ce manuscrit porte sur l’inversion des colonnes de formaldéhyde à partir de spectres de la radiation solaire rétrodiffusée par l’atmosphère terrestre, mesurés par les senseurs GOME, SCIAMACHY et GOME-2, lancés successivement en 1995, 2002 et 2006. La méthode d’inversion est basée sur la spectroscopie d’absorption optique différentielle (DOAS). Les concentrations de formaldéhyde intégrées le long du chemin optique moyen dans l’atmosphère sont dérivées à partir des spectres mesurés, et ensuite transformées en colonnes verticales par le biais de facteurs de conversion appelés facteurs de masse d’air. Ces derniers sont calculés à l’aide d’un modèle de transfert radiatif, en tenant compte de la présence de nuages, des propriétés de la surface terrestre et la distribution verticale supposée du formaldéhyde, fournie par le modèle IMAGES. Un des objectifs principaux de la thèse a été d’optimiser les paramètres d’inversion pour H2CO, et ceci pour les trois senseurs, tout en tenant compte des spécificités de chaque instrument. Ces efforts ont conduit à la création d’un jeu de données homogène, couvrant la période de 1996 à 2010. Les colonnes sont fournies avec un bilan d’erreur complet, incluant les erreurs liées à l’inversion des concentrations dans les spectres, ainsi que celles provenant de l’évaluation des facteurs de masse d’air. La série temporelle des observations de GOME, SCIAMACHY et GOME-2 présente une bonne cohérence et stabilité sur toute la période. Nous montrons aussi que la meilleure couverture terrestre de GOME-2 entraîne une réduction significative du bruit sur les observations moyennées, permettant une meilleure identification des sources d’émission. Notre jeu de données est exploité pour étudier la distribution régionale du formaldéhyde, ainsi que ses variations saisonnières et interannuelles, principalement liées aux variations de température et aux feux de végétation, mais aussi aux activités anthropiques. De plus, en s’appuyant sur la qualité de la série temporelle de 15 ans, nous présentons la première analyse des variations à long terme des concentrations de H2CO. Des tendances positives, de l’ordre de 1.5 à 4% par an, sont observées en Asie, en particulier dans l’est de la Chine et en Inde, liées à l’augmentation des émissions anthropiques d’hydrocarbures dans ces régions. Finalement, nos données ont été largement exploitées par le groupe de modélisation de l’IASB pour faire des études de modélisation inverse des émissions de NMVOCs. Les résultats démontrent le haut potentiel des données satellitaires pour contraindre les inventaires d’émissions dues à la végétation et aux feux de biomasse, particulièrement dans les écosystèmes tropicaux, en Asie du sud-est, et dans le sud-est des Etats-Unis.

A gas-fluidized bed bioreactor was developed in this research as a new method for treating polluted air. The fluidization characteristics of selected packing materials were investigated. Then, bioremediation was tested using two types of packing in a fluidized bioreactor, as well as in a comparable packed bed. Microorganisms on the particles biodegrade contaminants in the polluted air, which flows up through the bed. At high flowrates, the polluted air fluidizes the particles, while at low velocities the operation is in packed bed mode.<p>Initially, sawdust was selected for use as a packing material. Due to the poor fluidization properties of sawdust, glass spheres were added. A mixture of sawdust and glass spheres remained well mixed during fluidization. In the mixture, interparticle forces increased with increasing moisture in the sawdust, eventually causing defluidization of the bed. In the absence of bioremediation, mass transfer was studied between ethanol-contaminated air and sawdust/glass sphere packing, and found to be higher in the fluidized versus packed mode. In bioremediation experiments, ethanol removal efficiencies were as high as 95% in both operating modes. The maximum elimination capacities (EC) of ethanol were 75 and 225 g m^-3 sawdust h^-1 in the fluidized and packed beds respectively.<p>The packing of the fluidized bed bioreactor was optimized in order to boost bioremediation rates. Experiments showed that peat granules fluidized well in a bubbling regime, likely due to their relatively high density and sphericity. In peat bioremediation trials, the fluidized mode outperformed the packed bed; the maximum ECs were 1520 and 530 g m^-3 peat h^-1, respectively. Removal efficiency in the fluidized mode decreased with velocity, because the size and amount of large bubbles increased.<p>A steady-state model of the fluidized bioreactor was developed. By taking account of bubble properties during fluidization, the model helps to explain how bubble size, microbial properties and bioreactor residence time affect removal efficiency and elimination capacity of the bioreactor.<p>A peat gas-fluidized bioreactor shows promise as an efficient, low-cost technology for air treatment. Particle mixing in the fluidized bed may prevent operating problems associated with the packed bed bioreactor. Fluidized bioreactors are ideal for the treatment of high volume, low concentration air emissions.

A gas-fluidized bed bioreactor was developed in this research as a new method for treating polluted air. The fluidization characteristics of selected packing materials were investigated. Then, bioremediation was tested using two types of packing in a fluidized bioreactor, as well as in a comparable packed bed. Microorganisms on the particles biodegrade contaminants in the polluted air, which flows up through the bed. At high flowrates, the polluted air fluidizes the particles, while at low velocities the operation is in packed bed mode.<p>Initially, sawdust was selected for use as a packing material. Due to the poor fluidization properties of sawdust, glass spheres were added. A mixture of sawdust and glass spheres remained well mixed during fluidization. In the mixture, interparticle forces increased with increasing moisture in the sawdust, eventually causing defluidization of the bed. In the absence of bioremediation, mass transfer was studied between ethanol-contaminated air and sawdust/glass sphere packing, and found to be higher in the fluidized versus packed mode. In bioremediation experiments, ethanol removal efficiencies were as high as 95% in both operating modes. The maximum elimination capacities (EC) of ethanol were 75 and 225 g m^-3 sawdust h^-1 in the fluidized and packed beds respectively.<p>The packing of the fluidized bed bioreactor was optimized in order to boost bioremediation rates. Experiments showed that peat granules fluidized well in a bubbling regime, likely due to their relatively high density and sphericity. In peat bioremediation trials, the fluidized mode outperformed the packed bed; the maximum ECs were 1520 and 530 g m^-3 peat h^-1, respectively. Removal efficiency in the fluidized mode decreased with velocity, because the size and amount of large bubbles increased.<p>A steady-state model of the fluidized bioreactor was developed. By taking account of bubble properties during fluidization, the model helps to explain how bubble size, microbial properties and bioreactor residence time affect removal efficiency and elimination capacity of the bioreactor.<p>A peat gas-fluidized bioreactor shows promise as an efficient, low-cost technology for air treatment. Particle mixing in the fluidized bed may prevent operating problems associated with the packed bed bioreactor. Fluidized bioreactors are ideal for the treatment of high volume, low concentration air emissions.

We have investigated the chemical sensitivity of nanoporous (NP) alumina-coated surface acoustic wave (SAW) devices that have been surface-modified with polymeric mediating films. The research in this dissertation covers the refinement of the NP alumina coating, development of dendrimer and/or polymer surface modifications, design of composite ultrathin vapor-phase analyte gates, and preparation of selectively permeable, polymeric films that mediate analyte transport. Nanoporous alumina SAW devices were fabricated from planar Al SAW devices using an anodization process that yields a high-surface-area transduction platform. Refinement of the anodization process results in a homogeneously porous substrate capable of ~40 times the analyte sensitivity of conventional planar SAW devices. Attempts to directly impart selective gas-phase analyte permeation with monolayers of amine-terminated, poly(amidoamine) (PAMAM) dendrimer films were investigated with and without secondary functionalization. We also prepared and characterized pore-bridging polymeric composite ultrathin films (~12 nm) of PAMAM dendrimers and poly(maleic anhydride)-c-poly(methyl vinylether) (Gantrez). Access to the underlying pores of the NP alumina coating can be modulated through the sequential deposition of the composite film. These tailorable ultrathin films result in impermeable surface- modifications which fully gate the analyte response without filling the porous structure. Thin spin-cast films (40 nm) of polydimethylsiloxane (PDMS) were developed to simultaneously provide selective sorption and permeation characteristics towards vapor-phase analytes. The porous nature of the underlying alumina coating provides for this real-time evaluation of sorption and permeation. The results suggest that the thin films offer preferential sorption of non-polar organics and selective permeability towards water vapor.

This research investigate and analysis 77 kinds of volatile organic compounds (VOCs) in the sewage system of a southern urban area (A, B, C, D, E and F). The 77 kinds of VOCs will be divided into BTEX, chlorine-containing hydrocarbons and non-chlorine-containing hydrocarbons, and to estimate the emission of 27 kinds of hazardous air pollutants (HAPs). Cancer risk within 12 kinds of HAPs will also be part of the investigation by using Risk Assessment. In terms of consistency, except A1, D5 and E, VOCs are required mainly of non-chlorine-containing hydrocarbons at other areas, and main contribution species are ethylene, acetylene and ethane. There are 55.05 % of BTEX (1298.2 £gg/m3) and 35.51 % of non-chlorine-containing hydrocarbons (837.6 £gg/m3) in A1, but the main contribution are toluene, m-xylene and p-xylene. In D5, there is 76.39 % of BTEX (3744.7 £gg/m3) and the main contribution are m-xylene, p-xylene and toluene. In E, there is 80.02 % of chlorine-containing hydrocarbons (4807.1 £gg/m3) and the main contribution are chloromethane and toluene. Results show that the most emissions of total HAPs is D5 (12195.3 mg/hr), followed by B2 (4602.9 mg/hr), E (2659.4 mg/hr), A4 (2043.7 mg/hr) and A1 (1526.2 mg/hr). BTEX represent the largest proportion of the emissions of total HAPs in D5, A4 and A1. Chloroethene represents the largest proportion of the emissions of total HAPs in B2, followed by trichloroethene and tetrachloroethene. Chloromethane represents the largest proportion of the emissions of total HAPs in E. The most cumulative cancer risk in the sewage space is B2, followed by C2 and A3. The main contribution of the average cancer risk (not include B2) in a southern urban area are 1,1,2-trichloroethane, 1,2-dichloroethane and 1,4-dichlorobenzene.