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Abstract:
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Among the most ubiquitous and persistent air quality problems facing urban areas are high concentrations of gas phase oxidants and fine particulate matter . Ozone and particulate matter concentrations in urban areas are significantly influenced by other factors in addition to local emissions , such as regional transport spanning distances as large as 1000 kilometers . Despite the importance of regional transport in meeting air quality standards , to date most analyses of regional transport have focused only on short duration episodes , or semi -quantitative assessments . The development and evaluation of seasonal , quantitative assessments of regional pollutant transport , based on modeling calculations and observational data is the topic of this dissertation .
The observational data available through the Texas Air Quality Studies in 2000 and 2006 provide a unique opportunity to develop , evaluate , and improve methods for characterizing regional air pollutant transport . Measurements collected during these studies are used as the primary observational basis for characterizing regional ozone transport and to evaluate the performance of photochemical models . Results suggest that measurements (from aircraft and surface monitors ) and the photochemical model provide consistent estimates of the magnitude of ozone transport . On this basis , photochemical modeling is used to determine potential impacts of regional ozone transport in Texas , under varying meteorological and photochemical conditions , as well as to characterize the dominant chemical and physical processes within urban plumes .
While qualitative studies and limited quantitative analyses have been performed to assess regional ozone transport , this work includes the first detailed quantitative characterization of the importance of ozone transport over the course of an entire ozone season using both photochemical modeling and ambient data . Results demonstrate that urban plumes in Texas are capable of transporting significant amounts of ozone over distances spanning hundreds of kilometers . Furthermore , on a seasonal basis , there are a number of days characterized by high contributions from inter -city transport coinciding with high total ozone concentrations , suggesting that the role of inter -city transport will remain significant for many areas to demonstrate attainment of the NAAQS for ozone . Results also indicate that reductions in the impacts of inter -city transport are possible by decreases in emissions from source regions . |