Thesis (Ph. D.)--University of Missouri-Columbia, 1998. / Typescript. Vita. Includes bibliographical references (leaves 86-91). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 1998. / Typescript. Vita. Includes bibliographical references (leaves 86-91). Also available on the Internet.

Thesis (M. Phil.)--University of Hong Kong, 2010. / Includes bibliographical references (leaves 139-[147]). Also available in print.

Thesis (M. Phil.)--University of Hong Kong, 2010. / Includes bibliographical references (leaves 139-[147]). Also available online.

Philosophiae Doctor - PhD / In the natural decay series of 238U an inert radioactive gas, 222Rn (radon) is formed in the decay of 226Ra. Because radon is relatively soluble in water, it migrates from places of its generation in rocks and soils to other places either by soil air, or travels with underground water. Therefore, there is a growing interest among hydrogeologists in using radon as a natural tracer for investigating and managing fresh water reservoirs. This work is aimed at investigating and developing radon-in-water measuring techniques applicable to aquifers and rivers. A gamma-ray spectrometry method using a hyper-pure germanium (HPGe) detector, based at iThemba LABS, Cape Town and Marinelli beakers, has been optimized to measure radon in borehole water via the g-rays associated with the decay of radon daughters 214Pb and 214Bi (in secular equilibrium with their parent). An accuracy better than 5% was achieved. Moreover, long-term measurements of radon in water from an iThemba LABS borehole have been carried out to investigate the role of radon for characterizing aquifers. These investigations led to the development of a simplified physical model that reproduces the time-evolution of radon concentration with borehole pumping and may be used to estimate the time for representative sampling of the aquifer. A novel method is also proposed in this thesis to measure radon-in-water in the field after grab sampling - a so-called quasi in-situ method. The quasi in-situ method involves inserting a y-ray detector in a container of large volume filled with water of interest. The g-ray spectra are analyzed using an approach involving energy intervals on the high-energy part of the spectrum (1.3 – 3.0 MeV). Each energy interval corresponds to contributions from one of the major g-ray sources: 40K and the decay series of 238U and 232Th, and cosmic rays. It is assumed that the U interval will be dominated by g-rays emitted from the radon daughters (214Pb and 214Bi). Minor contributions to an interval with major radionuclide are corrected using an MCNPX simulated standard spectra. The two methods in this thesis make a significant contribution to measuring and modelling of radon in aquifers and surface waters. It forms a basis for further development in an interactive mode with hydrological applications. / South Africa

This dissertation explored the multifaceted issue of radon exposure and its connection to lung cancer, focusing on knowledge gaps and proposing mitigation strategies. Despite extensive research, inconsistencies persist in understanding the health impacts, public awareness, and effective mitigation of radon, particularly in regions like Tennessee that are disproportionately burdened by high radon levels. This work addresses this gap by integrating findings from three distinct studies: a scoping review, a cross-sectional survey, and a policy analysis. The review examined national literature about residential radon exposure, revealing variations in exposure levels and conflicting evidence regarding the risk of lung cancer. The cross-sectional study investigated radon Environmental Health Literacy (EHL) and testing behavior among Health Council participants in Northeast Tennessee, which uncovered disparities and associated risk factors. Finally, the policy analysis examined existing radon regulations across federal, state, and local levels, focusing on Tennessee, and proposed strategies for improvement, including standardized licensing for radon professionals. The combined findings of this study highlight the need for interdisciplinary collaboration to address radon challenges effectively in Tennessee. The review underlines the variability in exposure-risk associations, while the survey emphasizes the importance of tailored educational interventions to improve awareness and ameliorate testing rates. The policy analysis advocates for standardized certification to ensure reliable radon services in Tennessee. Overall, this dissertation offers valuable insights into radon's impact on public health and proposes strategies for mitigation through improved regulations, increased awareness initiatives, and targeted interventions, which all depends on collaborative efforts between stakeholders.

A review of the applications of the Radon transform is presented, with emphasis on emission computed tomography and transmission computed tomography. The theory of the 2D and 3D Radon transforms, and the effects of attenuation for emission computed tomography are presented. The algebraic iterative methods, their importance and limitations are reviewed. Analytic solutions of the 2D problem the convolution and frequency filtering methods based on linear shift invariant theory, and the solution of the circular harmonic decomposition by integral transform theory--are reviewed. The relation between the invisible kernels, the inverse circular harmonic transform, and the consistency conditions are demonstrated. The discussion and review are extended to the 3D problem-convolution, frequency filtering, spherical harmonic transform solutions, and consistency conditions. The Cormack algorithm based on reconstruction with Zernike polynomials is reviewed. An analogous algorithm and set of reconstruction polynomials is developed for the spherical harmonic transform. The relations between the consistency conditions, boundary conditions and orthogonal basis functions for the 2D projection harmonics are delineated and extended to the 3D case. The equivalence of the inverse circular harmonic transform, the inverse Radon transform, and the inverse Cormack transform is presented. The use of the number of nodes of a projection harmonic as a filter is discussed. Numerical methods for the efficient implementation of angular harmonic algorithms based on orthogonal functions and stable recursion are presented. The derivation of a lower bound for the signal-to-noise ratio of the Cormack algorithm is derived.

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