Volatile organic compounds (VOCs) are those chemical species having sufficiently high vapor pressures to exist largely or entirely in the gaseous phase, whereas reactive organic carbon (ROC) encompasses all organics except methane. ROC can be emitted biogenically and anthropogenically, usually in a pure hydrocarbon form that is susceptible to reaction with common atmospheric oxidants such as hydroxyl and ozone in the initial steps to the formation of particulate matter, the criteria pollutant most strongly implicated in human mortality. The diversity of both the emitted VOCs and their possible atmospheric reactions yields countless different compounds existing in the atmosphere with a correspondingly wide range of volatility, solubility, reactivity, etc.. Moreover, the temporal and spatial variability of a given analyte is often large. Real-time chemical characterization of gaseous and particulate organic compounds can be achieved by instrumentation utilizing chromatographic and/or mass spectrometric techniques, but these methods are expensive, often logistically challenging, and require high levels of skills for both operation and data analysis. Conversely, filter-based measurements for organic particulates are inexpensive and straightforward, but do not give real-time data and analytes may be lost or transformed before analysis. There is a niche for robust, low-maintenance, moderate-cost instrumentation that offers chemical information on atmospheric carbon. Presented here are two projects that develop and validate instrumentation for measuring ROC. The first combines flame ionization detection (FID) with a CO2 detector to estimate the O/C ratios of sampled gases and particulates. O/C ratios are a particularly valuable piece of chemical information as higher ratios give lower volatility and higher solubility, meaning increased propensity to partition into the condensed phase. The second project utilizes portable VOC samplers with sorbent tubes that trap and protect analytes for detailed analysis. The samplers' portability and programmable microcontrollers offers the investigator great flexibility, both spatially and temporally. A third project analyzed the chemical composition of commercially available fragrance mixtures and modeled their emissions' impact on oxidant reactivity. It was observed that terpenes, despite their low mole fractions in the mixtures, represent the vast majority of emitted reactivity and are quantitatively evolved from the mixtures in a matter of hours. / Doctor of Philosophy / Organic (i.e., carbon-containing) compounds are emitted into the atmosphere from a variety of natural and anthropogenic sources. Respective examples would include the agreeable aroma of a pine forest (from terpene compounds) or the pungent smell of gasoline (from additives such as toluene). These emitted compounds are often pure hydrocarbons (molecules formed of carbon and hydrogen atoms), and the category VOCs (volatile organic compound) encompasses hydrocarbons and the products of their chemical reactions with atmospheric oxidants like the hydroxyl radical and ozone. In the presence of pollutant nitrogen oxides, oxidants modify these VOCs; adding oxygen lowers the VOCs' vapor pressure and increases aqueous solubility, resulting in higher likelihood of condensation from the gaseous phase into particulates (liquid or solid phases). "Smog" is a colloquial term for the entire suite of noxious chemical compounds produced in the air from reactions of largely anthropogenic organic precursors. Particulates, a.k.a. aerosols, are the most concerning atmospheric pollutant due to deleterious effects on respiratory and cardiovascular health and has shown strong correlations with increased mortality in exposed groups such city dwellers. Determining the chemical identities of the VOCs is useful for pollution forecasting and possibly identifying and quantifying VOC sources. Current methods for chemical identification are cumbersome, expensive, complex, and wholly unsuitable for many investigators. In this work, we introduce two new approaches to gathering chemical information about organic gases and particulates. The first instrument has been demonstrated to give accurate estimates of oxygen/carbon (O/C) ratios; higher O/C ratios represent higher propensities to condense into particulate forms. The second instrument developed is a portable VOC sampler, which traps (and prevents reaction of) a broad range of organics on a sorbent (such as activated charcoal) in a small metal tube. After sampling in remote locales, the tubes can be analyzed in the lab and the VOCs identified and quantified. The third study investigated the chemical composition of fragrance mixtures (present in perfumes, cleaning agents, etc.) and modeled (i.e., estimated) VOC emissions based on the fragrance components as well as the effects on atmospheric oxidant levels. Fragrance mixtures represent a significant source of atmospheric carbon, so a more thorough understanding of the fragrances' impacts on oxidant levels gives further insight into atmospheric processes and aerosol formation.

In order to preserve groundwater resources from contamination by volatile organic compounds and to clean up sites contaminated with the compounds, we should understand fate and transport of contaminants in the subsurface systems and physicochemical processes involving remediation technologies. To enhance our understanding, numerical studies were performed on the following topics: (i) multiphase flow and contaminant transport in subsurface environments; (ii) biological transformations of contaminants; (iii) in-situ air sparging (IAS); and, thermal-enhanced venting (TEV). Among VOCs, trichloroethylene (TCE) is one of the most-frequently-detected chemicals in the contaminated groundwater. TCE and its daughter products (cis-1,2-dichloroethylene (cDCE) and vinyl chloride (VC)) are chosen as target contaminants. Density-driven advection of gas phase is generated by the increase in gas density due to vaporization of high-molecular weight contaminants such as TCE in the unsaturated zone. The effect of the density-driven advection on fate and transport of TCE was investigated under several environmental conditions involving infiltration and permeability. Biological transformations of contaminants can generate byproducts, which may become new toxic contaminants in subsurface systems. Sequential biotransformations of TCE, cDCE, and VC are considered herein. Under different reaction rates for two bioreaction kinetics, temporal and spatial concentration profiles of the contaminants were examined to evaluate the effect of biotransformations on multispecies transport. IAS injects clean air into the subsurface below the groundwater table to remediate contaminated groundwater. The movement of gas and the groundwater as a multiphase flow in the saturated zone and the removal of TCE by IAS application were analyzed. Each fluid flow under IAS was examined in terms of saturation levels and fluid velocity profiles in a three-dimensional domain. Several scenarios for IAS systems were simulated to evaluate remedial performance of the systems. TEV was simulated to investigate its efficiency on the removal of a nonaqueous phase liquid in the unsaturated zone under different operational conditions. For numerical studies herein, the governing equations for multiphase flow, multispecies transport, and heat energy in porous media were developed and solved using Galerkin finite element method. A three-dimensional numerical model, called TechFlowMP model, has been developed.

The objectives of this study are to determine the non-methane volatile organic carbon emissions from the parts used in the interiors of buses at different temperatures and to analyze the components of these emissions. The total non-methane volatile organic carbon (NMVOC) concentrations in various sections of a bus were measured in order to determine the indoor air pollution in the bus. Different samples of the materials used in the interior parts of the buses were provided by the manufacturing company and they were tested in the METU Air Pollution Laboratory in order to see what hydrocarbon components make up this total NMVOC concentration.The results of experiments showed that the leading constituent emitted from the test pieces was toluene. Benzene concentration was very low. This is very important since benzene is a carcinogen and it has very low indoor concentration limits determined by OSHA and NIOSH. When the concentrations of the total NMVOC emitted from various parts are examined, it was seen that the most of the VOC emissions occur from the floor materials and ventilation channel. After measurements were done in two buses the average indoor total NMVOC concentrations were found as 21.15 &plusmn / 5.8 ppmv (as C3H8) and 46.04 &plusmn / 9.2 ppmv (as C3H8) in the first and second bus, respectively. Suggestions were made to the manufacturing company for some replacement of solvents and adhesives, and measurements were repeated with the newly manufactured parts for the bus. The highest concentrations were observed for toluene in these measurements, too. However, the toluene concentration was at least 40% lower than the initial values. Benzene concentrations were again very low. The average indoor total NMVOC concentrations were found as 10.41 &plusmn / 2 ppmv (as C3H8) in the measurements done in the bus decorated with new materials. This concentration was about 50% and 25% of the values measured in the first and the second bus at the beginning of the study, respectively.

Student Number: 9503012G Master of Science. School of Geography, Archaeology and Environmental Studies / A brown haze which builds-up over Cape Town under calm and cold weather conditions causes public concern. The brown haze is thought to be due to the gaseous and particulate emissions from the city, industries, traffic and townships in the Cape Town region. Volatile organic carbon (VOCs) compounds are an important component of the haze layer particularly because of their reactivity. VOCs play an important role in the carbon budget and radiation balance, regional oxidant balance, and in the distribution of ozone and other reactive gases, both at the regional and global scale. In this study the variation in ambient VOC concentrations during brown and non-brown haze days over Cape Town during July and August 2003 were characterised. Ambient air samples were collected in evacuated stainless steel canistes from the South African Weather Service (SAWS) research aircraft (Aerocommander, ZS-JRB) and later analysed by gas chromotography equipped with a flame ionisation detector (GC-FID). Benzene, toluene, ethylbenzene and xylene (BTEX) were the specific VOCs targeted for this study. Comparable meteorology data was also collected to determine the effects of wind field and atmospheric stability on BTEX concentrations.