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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.

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

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

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

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.

Predicting the trajectories of hazardous discharges of dense gases

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


King, Gavin 30 November 2011 (has links)
The AQHI, currently used by the Canadian government, is a multi-pollutant public health information tool that is based upon extensive Canadian epidemiological evidence. As the AQHI is a relatively new metric, there is little published information about the accuracy, and behaviour of this metric both spatially and temporally. The goal of this work was to provide more information to the scientific community on the spatial and temporal behaviour of the AQHI in the Halifax, Nova Scotia region. Sampling was conducted in both the winter and summer of 2009, at 50 sites distributed around the city and at the central NAPS site in downtown Halifax. Statistical analysis was conducted using daily calculated AQHI values. AQHI values in the region were predominantly in the 1 to 3 range on the AQHI scale which corresponds to very good air quality. The Government reported AQHI was found to be significantly different from the 50 sample site s AQHI values for both summer and winter (P=<0.001 for both seasons). The Government reported AQHI was significantly higher (P=0.05) than the AQHI calculated for the 50 sampling sites. Analysis identified that more than 50% of the daily AQHI index values were reported differently than the local sites, most commonly over predicted by one AQHI index point. Analysis also indicated a temporal trend of disagreement between the reported and sampled AQHI values. It was observed that during periods when the AQHI was higher, there was greater disagreement between that reported and the sample site AQHI value. This finding raises some concern regarding the behaviour of the AQHI in both larger cities and over the next decade as Halifax increases in size. The miss-reporting of AQHI values also raises some concern for epidemiological work, if the AQHI is used as an exposure metric it could over estimate exposure to air pollution. However, the AQHI is a useful scientific measure having a number of advantages, first it is a multi pollutant measure based on sound epidemiological evidence linking a mixture of three major air pollutant metrics to health effects and second that it has been distilled into a form that is readily understood by the public. This project has been successful in providing more information to the scientific community on the spatial and temporal variation of the AQHI in the Halifax region. It has been able to identify both seasonal and temporal variation, reinforced the understanding of pollutant behaviour and has begun to provide information on the behaviour of the AQHI on small urban scales and provide valuable information for both researchers and policy makers on the AQHI from a public health context.

Ozone-sulphur dioxide effects on petunia : effects of ozone and sulphur dioxide singly and in combination ON Petunia hybrida Vilm. cultivars of differing sensitivities.

Elkiey, Tarek M. January 1978 (has links)
No description available.

Survey of Instrumentation for Air Quality Surveillance

Bowling, John. 04 1900 (has links) (PDF)
Florida Technological University College of Engineering Thesis / M.S.; / Masters; / Engineering; / Environmental Systems Management; / 54 p. / 54 leaves, bound : ill. ; 29 cm.

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