A three-dimensional (3D) photochemical grid model, CAMx-2.0 (1998), was employed to analyze the spatial and temporal variations of ambient ozone during ozone episodes (concentration of ozone > 120 ppbv) in the Kao-Ping airshed in 2000-2001. The sensitivity analyses of ozone concentrations to the emission reductions in volatile organic compounds (VOC) and nitrogen oxides (NOx) were performed, and the relationships between ozone concentrations and meteorological parameters were examined. Furthermore, the transport routes were studies using inverse trajectory method. Examinations of meteorological parameters and ozone trends reveal that warm temperature, sufficient sunlight, low wind, and high surface pressure are distinct parameters that tend to trigger ozone episodes in Kao-Ping area in autumn and winter seasons. Seasonal patterns of surface ozone include a summer minimum with two maxima in autumn and late winter to the middle of spring, consistent with low mixing heights in autumn and winter and large mixing height in summer. Predicted values of hourly ozone concentration agree reasonably well with measured data. The assessment of the effect of the initial and boundary conditions on the performance of the model revealed that the model can be improved by specifying an ozone concentration of 70 ppbv rather than 30 ppbv on the top boundary of the model, while separately considering the daytime and nighttime ozone concentration on the lateral boundary conditions. The sensitivity analysis shows a VOC-sensitive regime in Kaohsiung City. In addition to the locally emitted pollutants, the inverse trajectory analysis shows that most pollutants in Kaohsiung City come from Kaohsiung County, followed by Tainan County and Ping-Tung County. In autumn, the air quality is worst in Ping-Tung County and ozone episodes occur most frequently. Because the prevailing wind is north or north-east wind in autumn, most pollutants are transported from the upwind areas, including Kaohsiung City and Kaohsiung County. The sensitivity analysis shows a NOx-sensitive regime for Ping-Tung city, consistent with Sillman¡¦s results (1999), indicating that freshly emitted pollutants are typically (but not always) characterized by VOC-sensitive chemistry and evolve towards NOx-sensitive chemistry as the air parcels move downwind.

The abatement of ground-level ozone has been a priority of air pollution policy because of its harmful effects on human health, ecosystems, and climate. The responsiveness of ozone to emissions of its principal precursors, nitrogen oxides (NOx) and volatile organic compounds (VOCs), is known to depend nonlinearly on spatially and temporally variable factors. Given this variability, scientific understanding of ozone formation processes can facilitate the development of sensible control policies. This thesis applies a high-order sensitivity analysis technique, the Decoupled Direct Method in Three Dimensions (HDDM-3D), to examine ozone response to precursor emissions during summertime air pollution episodes in the southeastern United States. HDDM-3D is shown to accurately capture ozone response within an underlying air quality model, even over large ranges of emission perturbations. Nonlinearity of response is quantified, and nonlinear terms are applied to examine how estimates of sensitivity and source attribution respond to uncertainty in an emissions inventory. Ozone production regime is assessed using both HDDM-3D and species indicator ratios and found to be primarily NOx-limited outside urban centers. However, ozone response to region-wide emissions does not necessarily correspond to its sensitivity to local controls, hindering the usefulness of bipartite ozone regime classification. Significant heterogeneity of ozone response to NOx is found even over small spatial scales of emission origin, a potential complication often ignored in atmospheric modeling and emissions trading mechanisms. Atmospheric sensitivity analysis is linked with a comprehensive menu of potential control measures to demonstrate potential integration of scientific and economic considerations for control strategy formulation. Cost-optimized strategies are identified for attainment of federal ozone standards in Macon, Georgia, and for minimizing potential population exposure to unhealthful concentrations of ozone.

A photochemical mechanism is a very important component of an air quality model, which simulates the change of pollutant concentrations due to chemical reactions in the air. The accuracy of model prediction is directly impacted by the photochemical mechanism. In this study, two state-of-the-science photochemical mechanisms, SAPRC07 and Master Chemical Mechanism (MCM) v3.1, were implemented in the Community Multi-scale Air Quality Model (CMAQ) version 4.6 developed by the US EPA to study a high ozone (O3) episode during the 2000 Texas Air Quality Study (TexAQS) from August 16, 2000 to September 7, 2000. Predicted O3 concentrations by S07C are lower than those of S99 with a maximum difference as high as 20 percent. The two mechanisms also show significant differences in the predicted OH, PAN, HCHO and HNO3 concentrations. Although the two mechanisms predict different ozone concentrations, the relative response factors (RRFs) of O3 at rural, urban and industrial sites under emission controls of anthropogenic NOx and VOC by factors 0.6 – 1.4 predicted by the two mechanisms are very similar. Predicted O3 concentrations by MCM are similar to those of SAPRC07. The MCM predicted total VOC OH reactivity is similar to the SAPRC07 predictions at a suburban site where biogenic emissions dominate the OH reactivity and is slightly lower than the SAPRC07 predictions at an industrial site where anthropogenic emissions dominate. Besides, the predicted 1-hr and 24-hr average concentrations of major O3 precursor VOCs by MCM show under predictions of alkanes and alkenes by a factor of 2-5, 6 for ethane and 8.5 for propane. Major aromatic compounds generally agree better with observations, although benzene is under-predicted by 80 percent. Species specific emission adjustment factors can be derived from these direct comparisons to improve emission inventories in future studies. At the Clinton Drive site, most of the under-predictions occur in the afternoon when industrial facilities are in the immediate upwind direction and the missing industrial emissions are likely evaporative sources whose emission rates are temperature dependent.

L'incertitude entourant la production du pétrole et la pollution associée aux fossiles combustibles ainsi que la série d'accidents bien connus de Three Mile Island, Tchernobyl et Fukushima, en plus que le désir de diversifier les sources d'énergie sont des facteurs importants qui favorisent le développement de la technologie des cellules photovoltaïques. Certaines applications de photovoltaïques organiques sont particulièrement intéressantes à cause de la possibilité d'impréssion des circuits et la création de cellules photovoltaïques flexibles sous la forme d'un ruban adhésif. À la suite des études fondamentales de Tang, que l'on appelle hétérojonction en volume (BHJ), des cellules photovoltaïques ont été créées par une séparation de phase du polymère. Certains appareils BHJ sont déjà disponibles dans le commerce, mais leur efficacité photovoltaïque est encore faible. Afin d'améliorer cette efficacité, nous proposons de modéliser le processus critique par lequel une excitation locale ( « un exciton ») se dissocie pour former une paire électron / trou conducteur. Contrairement à la majorité des physiciens specialiste dans l'état solide impliqués dans l'étude de ce problème qui semble ignorer le caractère non-Born-Oppenheimer typique de cet événement, nous prévoyons de traiter cet événement directement par la modélisation photochimique utilisant la dynamique semiclassique (saut de suface de Tully) avec laquelle nous avons déjà une certaine expérience. Comme l'objectif est la compréhension des systèmes très complexes, nous proposons des calculs exploratoires basées sur la méthode TD-DFTB, une version semiempirique de la théorie de la fonctionnelle de densité en fonction du temps (TD-DFT) pour lequel un de nous est bien connu pour son travail pionnier. L'étude sera menée en collaboration avec le groupe ORGAVOLT des développeurs de méthodes ab initio pour la modélisation des BHJs, et avec des groupes à Singapour intéressés par les BHJs, ainsi qu'avec des groupes en Allemagne spécialisés dans la DFTB. / The uncertainty surrounding petroleum production and the pollution associated with fossil fuels plus the series of well-known accidents of Three Mile Island, Chernobyl and Fukushima plus the desire to diversify energy sources are important factors favoring the development of solar cell technology. For certain applications organic photovoltaics are particularly interesting because (for example) of the possibility of printing these circuits and the creation of flexible solar cells in the form of adhesive tape. Following the seminal studies of Tang, so-called bulk heterojunction (BHJ) solarcells have been created by polymer phase separation. Some BHJ divices are already available commercially but their photovoltaic efficiency is still low. In order to aid in the improving this efficiency, we propose to model the critical process by which a local excitation (an "exciton") dissociates to form a conducting electron/hole pair. In contrast with the majority of solid-state physicists involved in studying this problem who seem to ignore the typically non-Born-Oppenheimer character of this event, we planto treat this event directly by photochemical modeling using semiclassical (Tully-type) surface-hopping dynamics with which we already have some experience. As the objective is the comprehension of highly complex systems, we propose exploratory calculations based on the TD-DFTB method, a semiemprical version of the time-dependent density-functional theory (TD-DFT) for which one of us is well-known for his pioneering work. The study will be carried out in collaboration with the ORGAVOLT group of developers of ab initio methods for modeling BHJs, and with groups in Singapore interested by BHJs, as well as with groups in Germany specializing in DFTB.

Effective pollution mitigation is the key to successful air quality management. Although states invest millions of dollars to predict future air quality, the regulatory modeling and analysis process to inform pollution control strategy remains uncertain. Traditionally deterministic ‘bright-line’ tests are applied to evaluate the sufficiency of a control strategy to attain an air quality standard. A critical part of regulatory attainment demonstration is the prediction of future pollutant levels using photochemical air quality models. However, because models are uncertain, they yield a false sense of precision that pollutant response to emission controls is perfectly known and may eventually mislead the selection of control policies. These uncertainties in turn affect the health impact assessment of air pollution control strategies. This thesis explores beyond the conventional practice of deterministic attainment demonstration and presents novel approaches to yield probabilistic representations of pollutant response to emission controls by accounting for uncertainties in regional air quality planning. Computationally-efficient methods are developed and validated to characterize uncertainty in the prediction of secondary pollutant (ozone and particulate matter) sensitivities to precursor emissions in the presence of uncertainties in model assumptions and input parameters. We also introduce impact factors that enable identification of model inputs and scenarios that strongly influence pollutant concentrations and sensitivity to precursor emissions. We demonstrate how these probabilistic approaches could be applied to determine the likelihood that any control measure will yield regulatory attainment, or could be extended to evaluate probabilistic health benefits of emission controls, considering uncertainties in both air quality models and epidemiological concentration–response relationships. Finally, ground-level observations for pollutant (ozone) and precursor concentrations (oxides of nitrogen) have been used to adjust probabilistic estimates of pollutant sensitivities based on the performance of simulations in reliably reproducing ambient measurements. Various observational metrics have been explored for better scientific understanding of how sensitivity estimates vary with measurement constraints. Future work could extend these methods to incorporate additional modeling uncertainties and alternate observational metrics, and explore the responsiveness of future air quality to project trends in emissions and climate change.

Two long-standing air quality challenges in the United States are the control of tropospheric ozone and particulate matter, both of which are responsible for widespread damage to human health and the environment. This thesis presents three modeling applications in support of policy development and regulatory actions for control of these pollutants in the eastern United States, taking advantage of recent advancements in sensitivity techniques in a regional Eulerian photochemical air quality model. A broad evaluation of regional atmospheric pollution and transboundary air quality management, including the international scale, and an analysis of successful transboundary management efforts are also presented. The first modeling application is an evaluation of local and interstate impacts on ozone and fine particulate matter (PM2.5) from ground-level and elevated nitrogen oxide plus nitrogen dioxide and from sulfur dioxide emissions from individual states. This analysis identifies states responsible for a significant amount of regional secondary pollution, and states which do not have independent control over much of their pollution concentrations. An average of approximately 77% of each state s ozone and PM2.5 concentrations that are sensitive to the emissions evaluated are found to be formed from emissions from other states. The second application is an assessment of impacts from emissions from a single power-plant on resulting regional ozone concentrations. Three sensitivity techniques and two 3D photochemical models are applied. Ozone increases greater than 0.5 ppbv are found over eight states downwind from the power-plant. The third application supports the extension of a body of research aimed at advancing understanding of the ozone formation potential, or reactivity , of VOCs for use in regional-scale, rather than urban-scale, regulations. Air quality impacts of VOCs emissions from solvent use and manufacture are presented, scientific barriers to accounting for reactivity in regulations are discussed, current and upcoming regulatory applications are described, and results from a regional scale evaluation of reactivity quantification are presented.

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. / text