abstract: Stable isotopes were measured in the groundwaters of the Salt River Valley basin in central Arizona to explore the utility of stable isotopes for sourcing recharge waters and engineering better well designs. Delta values for the sampled groundwaters range from -7.6‰ to -10‰ in 18O and -60‰ to -91‰ in D and display displacements off the global meteoric water line indicative of surficial evaporation during river transport into the area. Groundwater in the basin is all derived from top-down river recharge; there is no evidence of ancient playa waters even in the playa deposits. The Salt and Verde Rivers are the dominant source of groundwater for the East Salt River valley- the Agua Fria River also contributes significantly to the West Salt River Valley. Groundwater isotopic compositions are generally more depleted in 18O and D with depth, indicating past recharge in cooler climates, and vary within subsurface aquifer layers as sampled during well drilling. When isotopic data were evaluated together with geologic and chemical analyses and compared with data from the final well production water it was often possible to identify: 1) which horizons are the primary producers of groundwater flow and how that might change with time, 2) the chemical exchange of cations and anions via water-rock interaction during top-down mixing of recharge water with older waters, 3) how much well production might be lost if arsenic-contributing horizons were sealed off, and 4) the extent to which replacement wells tap different subsurface water sources. In addition to identifying sources of recharge, stable isotopes offer a new and powerful approach for engineering better and more productive water wells. / M.S. Geological Sciences 2010

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The processes by which the three particle final state is formed in the He³(He³,2p)He⁴ reaction were investigated by observing the angular distribution of coincidence events between the two protons as a function of the angle between the protons. The reaction mechanism was determined by comparing the experimental distribution with those predicted for the various possible processes obtained from kinematic and phase space arguments. The reaction was found to proceed predominantly by sequential decays through unbound intermediate states and to a lesser extent by a direct instantaneous three body breakup. The majority of the two stage decays passed through the ground state of Li⁵ , The mean lifetime of this state was measured and found to be (1.0 ± .3) x 10⁻²¹ sec There was also good evidence of a sequential decay through the diproton state. In order to fit the shape of the observed distribution it was necessary to assume that a diproton system exists which is unbound by 600 keV and has a mean lifetime of 1.5 x 10⁻²² sec However another possible interpretation is that a direct breakup occurs and the angular distribution of the protons is distorted by an attractive final state two proton interaction similar to the scattering interaction, although whether this interaction would be strong enough to produce the observed distribution is not known. A more quantitative three body decay theory is therefore necessary in order to draw any firm conclusions about the existence of the diproton state. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

The tests of performance of the modified thin-lens magnetic spectrometer using ring-detection have been extended using improved mechanical controls of detector position. The results show only a small improvement over the performance obtained previously in this laboratory. We conclude that the limit of performance with the thin-lens magnet has been reached. Further improvement: may be achieved only with a precision-wound magnet coil which will produce a completely symmetric field. The decay of [formula omitted] has been investigated using the modified thin-lens spectrometer, a scintillation spectrometer and beta-gamma, conversion-electron gamma coincidence techniques. The results support the simpler decay scheme proposed by Van Wijngaarden and Connor. The beta decay has three components with end-point energies and intensities of 659+3 kev(67 .3%), 411 kev (2.5%) and 89 kev (30.3%), estimated from the energy level intensity balances in Ba¹³⁴. These intensity balances show discrepancies of less than 3% of the total decay intensity. The conversion coefficients, calculated from the conversion electron and gamma-ray intensities lead to the following multipolarity identifications for the transitions in Ba¹³⁴; 473 kev (Ml or E2)j 563-569 kev (Ml or E2), 605 kev (E2), 797-803 kev (E2), 1036 kev (Ml or E2), 1168 kev (E2) and 1366 kev (E2), in agreement with other work. The Ml or E2 character of the 473 kev and 1036 kev transitions makes it possible to assign a spin of 3+ or 4+ to the 1641 kev level which was uncertain before. An unsuccessful search for evidence of a 960 kev gamma-ray reported by others puts an upper limit of 0.2% on its intensity. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

The present work proposes trial wave functions for the three-body problem in nuclear physics taking into account the group theoretical classification of the states given by Derrick and Blatt and by Verde. We start from the Schroedinger equation in the internal variables (the interparticle distances) obtained by Derrick from a summation over the matrix elements for kinetic energy and potential energy extended over all variables except the internal variables. An “equivalent" Schroedinger equation is set up using a potential due to Eckart. This equation has the same form as the original Schroedinger equation in the region outside the range of the nuclear forces. The variables in this equation can be separated in a hyperspherical coordinate system and the resulting separate equations can be solved. Then using a superposition principle the solutions of the original equation are expanded in terms of solutions to the "equivalent" equation. The Rayleigh-Ritz variational procedure is used to determine the coefficients of the expansions with a given potential. Because of the computational labor involved significant approximation is made in allowing only the leading terms in the angular variables to appear in the expansions while keeping a sufficient number of radial terms to insure convergence. The present functions with a radial variable R = [formula omitted] give less than 1/2 of the binding energy predicted by Blatt, Derrick and Lyness (1962) who used a radial variable R = r₁₂ + r₂₃ + r₃₁. This shows that our approximation with the former radial variable is indeed too crude to predict a reliable value for the binding energy and that more angular terms must be included in the expansions, at least for the preponderent symmetric S-state. Wave functions derived by the Rayleigh-Ritz variational principle are used to calculate cross sections for the reaction D(p, γ)He³. The electric dipole cross section depends very sensitively on the potential used to derive the wave function and a comparison with experimental data provides a test of the various model assumptions used to describe the nuclear interaction. A realistic potential must contain a tensor potential plus a hard core in the central potential. The tensor interaction couples the S and D states and is necessary to explain the quadrupole moment of He³ while the hard core produced the required mixed-symmetry S-state. The experimentally observed isotropic component of the gamma ray yield is attributed to a magnetic dipole transition between a continuum quartet S-state and the mixed-symmetry component of the ground state wave function. For a range of the variable parameter used in the calculation comparison with experiment requires a 5% admixture of the mixed-symmetry S-state in the ground state wave function. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

The contamination of groundwater by naturally occurring arsenic (As) in South and South East Asia has resulted in the exposure of an estimated 100 million people to hazardously high concentrations of this known carcinogen. Whilst the biogeochemical processes and mechanisms responsible for releasing As to groundwater are now understood, the fundamental controls on these processes have yet to be resolved. In particular, the role of different sources of organic matter (OM) in controlling the rate and extent of As release and how the contributions of these different sources may be influenced by groundwater abstraction practices, remains poorly constrained. Indeed, it is the absence of such key information which currently limits our capability to accurately predict both where and when As will be released in to the groundwaters of this region. Elucidation of the controls of these processes is therefore of vital importance for aiding policy makers and those responsible for mitigating the effects of the current catastrophe in providing a sustainable source of As free drinking water to millions of people in the countries impacted.We conducted investigations at two known As hotspots in West Bengal and Cambodia to assess the impact of groundwater abstraction practices on the composition of dissolved organic carbon (DOC) and As release. The radiocarbon age of DOC at both sites requires a contribution of young surface or near surface derived OM as well as contributions from older, sedimentary sourced OM. Mixing profiles at the Cambodian study site suggest this subsurface OM end member to have an age of between 1000 and 6000 years. A clear association is observed between high As concentrations in shallow groundwaters containing young DOC, with lower concentrations of As being associated with older DOC in deeper groundwater. This provides the first direct confirmation that younger, more labile sources of OM are able to support more extensive As release in these aquifers. Perhaps more importantly, it is shown that modern surface derived OM can be drawn into As contaminated groundwaters. Comparison of the residence times of groundwaters suggests that the extent of ground-surface water interaction is more extensive and extends to greater depths in aquifers that have been subjected to massive groundwater abstraction. Indeed, it is suggested thatgroundwater abstraction practices may be responsible for driving the downward transport of As contaminated shallow groundwater into deeper groundwater, and may potentially be driving changes in the composition of organic carbon within the groundwater. This could give rise to a more reactive, bioavailable organic carbon pool which has the potential to further influence As mobility in these groundwaters. The potential for secular changes in the groundwater As hazard in these regions must therefore consider the impact that changes in the DOC composition may have on the biogeochemical evolution of these aquifers.

A gas of atomic hydrogen confined at and below 1K in a sealed cell has been studied by magnetic resonance at the zero-field hyperfine transition frequency of 1420 MHz. A review is presented of magnetic resonance theory for a two level system, with emphasis on determination of the absolute magnetization by two methods: calibration of the spectrometer sensitivity and by use of the radiation damping time constant. Measurements at 1K on a gas at low density, 10¹¹<n[sub=H]<5x10¹² cm⁻³, in the saturated ⁴He vapour density have yielded the rate for the reaction H+H+He￫H₂+He, the diffusion constant and pressure shift of the hyperfine transition for H interacting with the He gas, and the cross-section for spin exchange relaxation. At temperatures below 1K, measurements of the frequency shift and effective recombination rate for H adsorbed on the He film have yielded values of the binding energies for H on ³He and for H on ³He as well as the hyperfine transition frequency shift and surface recombination rate for H adsorbed on each of these surfaces. The binding energies are found to be 1.15(5) K for H on ³He and 0.42(5) K for H on ³He. Measurements have been carried out at temperatures as low as 162 mK for H on ³He and 65 mK for H on ³He. lineshape for H atoms undergoing occasional sticking events on the helium surface. This model has been applied to frequency shift and transverse relaxation data at low temperatures to yield sticking probabilities of 0.046(5) for H on ³He and 0.016(5) for H on ³He. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

A completely automated mass spectrometer system has been developed to measure the oxygen isotope ratio of carbon dioxide samples. The system has been shown to have a precision of 0.03°/oo, which is comparable to that quoted for any other system in the world. In addition, the facility is capable of analyzing over one hundred samples per day. The system uses an Interdata minicomputer as the primary controller. The minicomputer monitors the quality of analyses, on-line, and thereby insures that all DEL values are measured to at least 0.04°/oo. Host of the sophistication resides in intelligent controllers within the mass spectrometer console. This design gives a technician considerable power when operating the system in a manual mode. The intelligence of the system is contained within hardware circuits, software within the minicomputer and firmware written for a Motorola 6802 microprocessor. A major contribution of this thesis has been the design and installation of an automated mass spectrometer inlet system. A microprocessor based inlet system controller maximizes the throughput of carbon dioxide samples within the inlet system. The inlet system normally contains four different aliquots of carbon dioxide and introduces these samples to the mass spectrometer, in proper sequence, through a single mass spectrometer admittance leak. The system has been used in the analysis of 111 samples of ice taken from the Steele Glacier, Yukon Territory. The samples taken from a vertical borehole, displayed a sawtooth variation of the oxygen isotope ratio with depth. The data have been explained by a physical model described in an appendix to this thesis. If our interpretation is correct, the isotopic variations have recorded at least four surges of the Steele Glacier. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

A stalagmite was collected in the Salón de la Permencia of the Majaguas Cave, that is a part of the Majaguas-Cantera Cave System in Cuba. The use of this stalagmite as a natural climate archive is advantageous not only because stalagmites can record continuous episodes of growth that are thousands of years in duration but also because they are easily and reliably dated, using U/Th dating methods. With this method, the stalagmite was reliably dated to 100 ka and was still active when removed from the cave for analysis. The stable isotopes of oxygen and carbon from this stalagmite from Western Cuba presents information of significant influencing factors on Caribbean precipitation records, and past climatic events during the Pleistocene. Due to the lack of high- resolution records for Western Cuba, this study verifies and adds to our knowledge of past climate variability for the Cuban region and the Caribbean as a whole. The δ18O data in MCS-01 shows a pattern that is very similar to the D-O and Heinrich events clearly recorded in the NGRIP ice core, especially at ~82ka and between 78-70ka. This study provides a continuous precipitation record for the area during the Pleistocene, allowing a greater understanding of the climate drivers that have had an impact on past precipitation patterns in this region.