In view of the worsening air quality in the world, more concerns are focused on the environment. This thesis uses the technique of CFD and develops the computer model to investigate the wind and pollutant transport, as well as the chemistry of reactive pollutants in idealized two-dimensional (2D) street canyons. Three scientific questions are raised in this thesis. The first task is to find out the po- sition with the most favorable pollutant removal along the ground level over 2D idealized street canyon of different building-height-to-street-width (aspect) ratios (ARs). The di- mensionless parameter, C, represents the pollutant removal performance. In the isolated roughness regime, the two local maximum C locate at the reattachment point and the windward corner. In the wake interference regime, C is peaked on the windward side. The number of vertically aligned recirculations depends on the street depth in the skimming flow regime. The sizes of the secondary recirculation upstream and downstream deter- mine how the maximum C shifts from the street centre. After identifying the position of peaked pollutant removal rate at the ground level, the emission source should be placed with the highest constant C in order to remove the pollutants upward more quickly to safeguard the street-level air quality. After understanding the best pollutant removal in the street canyon of different ARs, the second task is to find out what AR is the most favorable for the ventilation and pollutant removal across the roof level. The three parameters, namely friction factor, air exchange rate (ACH) and pollutant exchange rate (PCH), are introduced to quantify the pressure difference to sustain the mean flow, the ventilation and pollutant removal, respectively. The turbulence contributes more than 70% to the total ACH and PCH in all the three flow regimes. By increasing the atmospheric turbulence in building geometry as well as the surface roughness, the ventilation and pollutant removal performance can be improved. The linear relation between the friction factor and ACH demonstrates the larger resistance that in turn promotes the air exchange over the roof level. The physical dispersion is studied; however atmospheric pollutants are seldom in- ert but chemically reactive instead. The last task is to include the three common air pollutants, NO, NO2 and O3, in the simple NOx ?O3 mechanism in terms of the photo- stationary state and reaction rates. The Damkohler numbers of NO and O3, DaNO and DaO3, are parameterized by the concentrations of the sources NO and O3. The normalized mean and fluctuation NO, NO2 and O3 are separately considered. The integrated pho- tostationary state (PSS) in the first canyon increases with DaO3 under the same DaNO. The integrated PSS of the second to the twelveth street canyons are compared with each case, the monotonic increase in the PSS from the second to twelveth canyon is perceived in DaNO/DaO3 1, 0.03, 0.02, 0.001 and 0.000333. Further decreases the DaNO/DaO3 to 0.000143, 0.000125, 0.000118, 0.000111 and 0.0001, the PSS is found to be non-linear and the trough appears in the fourth and fifth canyons. / published_or_final_version / Mechanical Engineering / Master / Master of Philosophy

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Distributions of air pollutants and their precursors in the troposphere are driven largely by meteorological conditions (e.g., wind, cloud convection, lightning, and precipitation) and emissions such as those of NOx from anthropogenic sources (e.g., fossil fuel combustion) and natural sources (e.g., soils and lightning). As the most polluted regions in the world, North America and East Asia significantly contribute to climate change on both regional and global scales. Therefore, it deserves to investigate the vertical and horizontal distributions of the air pollutants in the troposphere over these two regions to better quantify the interaction between air pollution and climate change, which remains until now largely uninvestigated. Here, a Regional chEmical trAnsport Model (REAM) was developed and applied to examine the uncertainties in modeling the effect of convective transport and lightning NOx production on upper tropospheric chemical tracer distributions over North America, and to identify the features of air pollutions over East Asia.

Michel M. Benarie. / Includes bibliographies and indexes.

Observational studies have consistently demonstrated associations between exposure to air pollution and increased cardiovascular morbidity and mortality. These associations are strongest for fine particulate matter (PM), of which particulates from the combustion of fossil fuels are an important component. In Europe, the contribution to urban PM from diesel emissions is increasing with the popularity of diesel engines for road transport. Despite the strength of the epidemiological evidence and the emergence of promising hypotheses, the important constituents and biological mechanisms responsible for the cardiovascular effects of air pollution are largely unknown. It is possible that nanoparticulates or soluble components of PM may translocate into the bloodstream, resulting in direct effects on the vascular endothelium and thrombotic pathways. I investigated the potential for inhaled radiolabelled nanoparticulates to translocate into the circulation in man. Using two unique human exposure facilities I assessed the effects of exposure to combustion-derived particulates in dilute diesel exhaust and concentrated ambient fine and ultrafine particles on vascular endothelial, endogenous fibrinolytic and myocardial function in healthy volunteers and patients with stable coronary artery disease. In total, forty-two healthy men and thirty-two patients with stable coronary artery disease were exposed to particulates or filtered air for 1-2 hours in a series of double blind randomised crossover studies. At levels encountered in an urban environment, inhalation of dilute diesel exhaust impaired two important and complementary aspects of vascular function in man: the regulation of vascular tone and endogenous fibrinolysis. Vascular dysfunction persisted for up to 24-hours following exposure and was associated with an increase in systemic inflammatory cytokines. In patients with coronary heart disease exposure to diesel exhaust did not aggravate pre-existing vasomotor dysfunction, but did exacerbate exercise-induced myocardial ischemia and reduce acute endothelial tissue plasminogen activator release. In contrast, exposure to concentrated ambient particulates, low in combustion component, did not affect vascular function in either healthy volunteers or patients. I found little evidence that inhaled radiolabelled nanoparticles translocate into the circulation and suggest the adverse vascular effects of combustion derived air pollution are mediated primarily by their soluble components rather than by a direct interaction between nanoparticles and the vasculature. My findings have identified ischemic, vascular and thrombotic mechanisms that may explain in part the observations that exposure to combustion-derived air pollution is associated with adverse cardiovascular events including acute myocardial infarction. Ongoing research in this area will provide further insight into the adverse effects of PM, with the possibility of targeted interventions, such as the use of retrofit particle traps on diesel powered vehicles, to reduce the impact of environmental air pollution on cardiovascular disease a realistic goal.

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