Ground-level ozone is of a growing concern in many areas of the United States. Ozone is a significant health concern, particularly for people with asthma and other respiratory diseases. Ozone is rarely emitted directly into the air but is formed by the reaction of volatile organic compounds (VOCs) and nitrogen oxides (NOx) in the presence of sunlight. VOCs are emitted from a variety of sources, including motor vehicles, chemical plants, refineries, factories, consumer and commercial products, other industrial sources, and biogenic sources. NOx is emitted from motor vehicles, power plants, and other combustion sources. Ozone and ozone precursors also can be transported into an area from pollution sources found hundreds of miles away.
In accordance with the 1990 Clean Air Act Amendments, EPA has required more extensive monitoring of ozone and its precursors in areas with persistently high ozone levels. In these areas, the States have established ambient air monitoring networks consisting of CAMS (continuous air monitoring system) sites, which collect and report detailed data for volatile organic compounds, nitrogen oxides, ozone and meteorological parameters. Analyses of these data help the regulatory agencies to better understand the underlying causes of ozone pollution, to devise effective remedies and to measure air quality trends. This thesis focuses on how to integrate these measurements of VOCs with the receptor modeling techniques in order to identify the sources of VOCs and to attribute ambient VOC concentrations to their original sources. The measurements taken from three CAMS stations in Houston, TX serve as the basis of this research.
After presenting the source attribution of volatile organic compounds, where the contribution from different sources to ambient VOC levels are determined, the methods to identify the source regions associated with elevated VOC levels are described. The quantitatively reconstructed emissions from a recently prepared VOC emissions inventory are compared with the receptor model calculations of ambient VOC measurements.
Finally, a separate growing concern in the US, the particulate matter pollution, is addressed. The impacts of regional wild fires in Texas on the secondary particulate matter formation are examined. The results of the laboratory investigations on the formation of the secondary sulfate particles through heterogeneous surface reactions are presented.