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

This thesis introduced the principle and the evolution of polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE), described its usage in monitoring the remediation process for oil and other chemical pollution as well as analyzing the nature microbial community, and finally made a comprehensive comment to its future development. PCR- DGGE was initially developed to study DNA mutations because it is a powerful tool to detect DNA base mutations in a PCR-amplified DNA fragment. Its accuracy can be as high as 100%. The principal of DGGE is based on the differences in DNA sequence that affect the melting points of each amplicons, and caused a decrease in the electrophoretic mobility of a partially melted DNA molecule in a polyacrylamide gel containing a linearly increasing gradient of DNA denaturants. PCR-DGGE can effectively detect the community structure of microorganisms in the environments, including the unculturable microorganisms. Nowadays, it has become one of the most frequently applied techniques to study the community structure of microorganisms. Microbiologists can use this technique to understand the microbial ecology, the shift of the microbial community structure during a bioremediation process, such as the oil pollution and other toxic chemical pollution. In addition, PCR-DGGE can also be used for the fermentation studies in food industry and agricultural industries. We can even identify unculturable microorganism by analyzing the DNA fragment sequences. This can help us to design a suitable medium to culture and isolate these ¡¥unculturable organisms¡¦. There are three directions for the further development of PCR-DGGE technique: 1.Improvement of material preparation processes; 2. development of new DGGE-related tools; and 3. combination of other technology with DGGE. The improvement of preparation processes can make DGGE more accuracy to analyze the community structure of microorganisms, improve the sensitivity of DGGE fingerprint detection, and help the DGGE normalization. The development of DGGE-related tools can overcome the limitations imposed on DGGE by co-migration and help us to have a better understanding of the meanings for a DGGE pattern. The combination of other technology with DGGE can help us to have a clear understanding of the microbial ecology, the shift of the microbial community structure, and the function of microorganisms.

No description available.

No description available.

The primary purpose and object of the study has been to reveal in retrospect the evolving conditions which have affected Ball State UniversityMuncie, IN 47306

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

Thesis (M. Env. St.)--University of Adelaide, Mawson Graduate Centre for Enivironmental Studies, 1994. / Includes bibliographical references (leaves 127-135).

Thesis (M.Sc.)--University of Hong Kong, 2008. / Includes bibliographical references (p. 70-74).

Thesis (Ph. D.)--University of Hong Kong, 2008. / Includes bibliographical references (leaf 161-174) and index. Also available in print.

Thesis (M.S. in Meteorology)--Naval Postgraduate School, March 2009. / Thesis Advisor(s): MacMahan, Jamie ; Pfeiffer, Karl. "March 2009." Description based on title screen as viewed on April 23, 2009. Author(s) subject terms: Sea breeze, inner shelf, cross-shelf transport, Monterey Bay Includes bibliographical references (p. 37-40). Also available in print.