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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.

Transport characteristics and regional source assessment of PM₂₅̣ in Atlanta : cluster analysis and potential source contribution function analysis

Antoine, Melissa K. 05 1900 (has links)
No description available.

Estimates for wet and dry removals' contribution to the residence time for atmospheric pollutants in the eastern United States

Vickers, Dean 14 March 1979 (has links)
The length of time that atmospheric pollutants released from low-level sources in the midwestern United States can expect to remain in the atmosphere is discussed. The pollution is assumed to be removed from the atmosphere by dry deposition and precipitation scavenging. Layer-average trajectories originating from Kansas City, Missouri are used to determine the Lagrangian probability of dry and wet conditions. The residence time of these pollutants is estimated based on parameterizations for the effective scavenging rates during wet and dry conditions. This investigation shows that, in summer, the probability that precipitation is being experienced by the pollutant is twice as great as the probability of precipitation at the origin of the pollution; this same ratio of probabilities is three in winter. Therefore, when precipitation scavenging is the more important removal mechanism, the statistics for the length of wet and dry periods at the source region overestimate the residence time by a factor of about two to three. By taking into consideration the Lagrangian probability of wet and dry periods, the relative importance of dry deposition and precipitation scavenging is discussed as a function of the wet and dry removal rates. It is seen that for a time- and vertical-average dry deposition velocity as large as 1 cm/sec, then dry deposition would normally be the bore important removal process for the meteorological conditions in the midwest to eastern United States. Estimates for the expected atmospheric lifetimes of aerosol particles and trace gases are reported as functions of dry deposition velocities and collection efficiencies (or washout ratios). For example, lead particles of mass mean diameter ~0.5 μm, should have a residence time ~8 days in winter, and ~3 days in summer, based on available data for the dry deposition velocity and washout ratio. In general, the residence time can be expected to be about twice as long during the summer season than the winter. The winter, monthly average distribution of pollutant mass is shown, based on the steady-state Gaussian approximation solution of the convective diffusion equation. The calculations are based on a statistical analysis of the 12 hourly positions of a series of trajectories. Thus, monthly average "diffusion" and removal are incorporated into the Gaussian model. / Graduation date: 1979

Investigation of the level of airborne contamination in the Pebble Bed Modular Reactor(PBMR) building or specific room due to design base leakrate of 0.1% of helium inventory / Reuben Ephraim Makgae

Makgae, Reuben Ephraim January 2003 (has links)
The fission products release into reactor core and primary circuit lead to airborne contamination as a result of helium that leaks from the system into the room. The airborne activity was calculated by deriving and solving a differential equation considering room ventilation and a twin room ventilation to check the effects of ventilation system or migration of airborne activity to the other rooms. The HVAC system was optimized by considering and comparing the activity calculated for the three HVAC system models (i.e. recirculation with and without filter and no recirculation of air or once through model) and by increasing the air change rate. The activity calculated for each nuclide ~as used to calculate the annual dose received by a worker spending 2000 working hours per year in the room. It was found that the dose received for the three HVAC models differs. The recirculation of air without filter was the most contributing in terms of dose followed by recirculation of air with filter model then no recirculation model was the least because there is no activity recirculated back into the room. The filters used for recirculation of air with filter model are radioactively contaminated, but the calculated filter activity was found to be low and can be disposed as low level waste or can be continuously used with an efficiency test regularly performed on the filters. / Thesis (MSc. ARST) North-West University, Mafikeng Campus, 2003

Stakeholders' experiences and perceptions of air pollution in a school environment.

Fray, Patrick Godfrey 20 August 2008 (has links)
The levels and sources of air pollution in the school community of Reiger Park, Boksburg is high and serious. This small township on the eastern outskirts of the Ekhurhuleni Metropolitan Municipality experience pollution problems that are very specific: (1) smoke from coal burning stoves and refuse burning; and (2) dust from abandoned mines or slime dams. The question of sustainable development is now on the international and national policy agendas. The concepts of ‘sustainable development’ and ‘sustainable human settlement’ have strongly emerged as priority concerns globally. Reiger Park, like many settlements in South Africa, encounters acute sustainable development problems. Indeed, the challenge of sustainable development is a national concern and priority in South Africa. Reiger Park shares characteristics of the broader developing world. Reiger Park, like many townships and communities in South Africa depends on the use of firewood and coal for cooking and heating purposes. This is problematic, releasing large amounts of smoke and carbon dioxide, which in turn pollutes the air. The pollution has widespread effects on the population, including learners within schools. This study’s main foci – education and clean air – reveals the typically degrading impact of poor quality air pollution on the education environment, posing serious threats to sustainable development of the poorer communities. Many households in the school community of Reiger Park make use of coal burning stoves for cooking and for keeping warm during the winter months. The coal that is burnt in the community, especially during winter months, releases gases into the atmosphere, which are harmful to the community. Other sources responsible for polluting Reiger Park, other than smoke from chimneys of houses, include dust from the nearby gold mine dumps, and open veldt fires and exhaust pipe emissions from automobiles. The authorities have found it difficult to control or eliminate these aspects of air pollution in the Reiger Park area. Educators were in agreement that, in the event of dust storms, classrooms are used as shelter from dust particles. Teachers and learners generally find the pollution problem in the community unbearable / Prof. H.G.van Rooyen

Predicting the trajectories of hazardous discharges of dense gases

Shaver, Elizabeth M. 08 1900 (has links)
No description available.

Towards sustainable development : application and validation of air dispersion model in urban environment

Sheng, Xiangyu January 1999 (has links)
No description available.

Scientific background on probabilistic air pollution dosage modeling

Gruhl, Jim January 1976 (has links)
No description available.

The design and development of devices for aerial pollution abatement

Lewis, Andrew January 2002 (has links)
No description available.

Fluxes to, and effects of O←3 and SO←2 on Picea sitchensis, P. abies, and Fagus sylvatica

Dobson, Martin C. January 1990 (has links)
No description available.

Studies of building stone weathering in south-east England

Jaynes, Suzanne Margaret January 1985 (has links)
No description available.

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