The intent of this thesis is to analyze obsidian artifacts from Chiquiuitan, Guatemala to see if the samples can be traced to known obsidian sources in the Maya region based on their unique chemical elements. Another aspect of this analysis is to determine the accuracy and validity of the Handheld XRF instrument on small and irregular obsidian samples. Furthermore, sourcing analysis allows researchers to acquire information about trade, exchange, and acquisition patterns of the material and gives researchers indications to prehistoric, social, and economic features.

<p>Arsenic (As) is an element that is well known for its toxic capabilities. It is odorless and colorless and is known to contaminate the drinking water of populations in several parts of the world. Routine monitoring of arsenic exposure is usually performed with urine, hair or nail, where samples are collected for laboratory analysis. Arsenic’s strong affinity to keratin rich tissues make skin another possible measurement site, in addition to the latter two tissues mentioned above. In some cases, skin samples are extracted for analysis. This is painful and invasive and is not ideal for <em>in vivo</em> monitoring of arsenic. The ability to quantify elemental concentration non-destructively is the major calling card of x-ray fluorescence (XRF). To that end, work was started on development of XRF detection systems for arsenic. The technique has shown promise for other elements and dramatic improvements in As detection capabilities were previously found when going from a radioisotope-based x-ray source to an x-ray tube based approach.</p> <p>This thesis documents the comparison of three x-ray tube based detection systems intended for the measurement of arsenic in skin. Two benchtop systems were used, with a) extended development of the previously assembled system and b) the first use of a separate detection system. Two handheld x-ray analyzers (portable detection systems) were also investigated in stand mode, where they were attached to a purpose-built mounting stand, provided by the manufacturer, during all analysis. Polyester resin phantoms were used to model arsenic in skin and a nylon backing was used to represent as bulk tissue behind skin. During the course of the work, modifications were made to the laboratory setup associated with the benchtop approaches.</p> <p>A benchtop polychromatic Mo anode x-ray tube based x-ray fluorescence (XRF) detection system was the first system used in this work. Through modifications to the existing design of the system, the lowest minimum detection limit (MDL) achievable was found to be (0.611±0.001) ppm normalized to gross scatter, where ppm is ug of arsenic per gram of dry weight (resin). The measurement time was ~1800 seconds real time. The equivalent (skin) and whole body effective doses delivered were (19±3) uSv and (163±47) uSv respectively. The corresponding direct (un-normalized) MDL was (0.499±0.002) ppm, in agreement with that found previously. Modifications to the system allowed a reduction in the localized effective dose delivered, to achieve this MDL, from (0.64±0.03) uSv previously to (0.14±0.04) uSv here.</p> <p>Next, the current work investigated two handheld x-ray analyzers provided by InnovX. A PiN diode detector based Alpha 4000S model unit (W anode x-ray tube) and a Silicon Drift Detector (SDD) based Delta model (Au anode x-ray tube). Both units were operated in benchtop mode: they were mounted in a stand and a phantom was placed on a kapton exit window. The lowest gross-scatter normalized and direct detection limit with the Alpha 4000S unit was (1.649±0.002) ppm and (1.651±0.002) ppm respectively. The equivalent and whole body effective doses delivered were found to be (9.4±2.2) mSv and (94±22) uSv respectively. The localized effective dose was (6.4±1.5) X 10^-3 uSv. By comparison, the Delta unit produced a gross-scatter and direct normalized detection limit of (0.570±0.002) ppm and (0.558±0.002) ppm respectively. The equivalent dose delivered was found to be (19.0±9.0) mSv. The corresponding localized and whole body effective doses delivered were (9.7±4.6) X 10^-3 uSv and (190±90) uSv respectively.</p> <p>The last system used in the current research was a monochromatic Ag anode x-ray tube based XRF setup. A doubly curved crystal (DCC) was used to select the Ag K-alpha line and focused the beam to a spot size of mm² at the focal length. The phantoms were placed at a farther distance where the beam had expanded to a larger area. The lowest Compton scatter normalized detection limit with the Si(Li) detector was found to be (0.696±0.002) ppm. After characterizing its performance in a range of energies, a silicon drift detector was also used on this system. It had the benefit of higher throughput capabilities and superior resolution. The housing of the detector was sufficiently small that it could be placed closer to the phantom surface than the Si(Li) detector. The lowest Compton-scatter normalized detection limit with the SDD was (0.441±0.003) ppm in 1800 seconds real time. The equivalent dose was found to be (11±2) mSv and the localized and whole body effective doses were found to be (3.92±0.87) X 10^-3 uSv and (110±23) uSv respectively. A significantly lower system dead time was observed with the SDD. Finally, Monte Carlo simulations of the system were performed to evaluate the performance of three ratios when their phantom measurement values were compared against simulations of skin. Results were found to be in agreement to withinin vivo concentration of arsenic in skin (ICRP).</p> <p>Finally, EDXRF measurements were performed on bulk cores of skin, <em>ex vivo</em>. While it was not possible to detect arsenic in the samples, due to the samples being collected from members of the public as opposed to an exposed population, a depth profile of numerous skin samples, starting from the surface and running straight down, was obtained for calcium, iron and copper.</p> / Doctor of Philosophy (PhD)

Master of Science / Department of Geology / Matthew Totten / The Woodford shale is recognized as an abundant source rock across Oklahoma and much of the midcontinent (Lambert, 1990), and up to 8% of the world’s hydrocarbon reserves are estimated to have been sourced by the Woodford and its equivalents (Fritz et al, 1991). The Woodford shale is far more complex than other Devonian black shales found in North America due to the presence of alternating bands of chert-like amorphous silica and silica-rich shale. Analysis of chert and its possible role in gas generation and storage in shales has been largely overlooked. The goal of this study is to determine if chert size, amounts, or polycrystallinity can be indicators of thermal maturity within the Woodford shale. Handheld XRF analysis was conducted on the whole rock samples, and a mudrock specific sodium bisulfate fusion was used to separate the non-clay fraction. SEM was performed on the resulting separates to study and observe changes in chert fabric, grain-size, and amount. No correlations were observed to indicate that chert is an indicator of thermal maturity within the Woodford shale. Increase in chert growth and amount was also not detected within the size fractions as thermal maturity increases. Handheld XRF proved to be a good proxy for quick, onsite analysis of silica concentrations, as well as the amount of organic matter within drill core. This could be beneficial as hydraulic fracking produces best results in areas of higher silica content, and the wells with the highest organic matter have the highest potential for petroleum accumulations.

The content of atmospheric dust in ice cores from Greenland varies with changes in climate, but the exact relationship is yet unknown. To determine this correlation, the source of the Greenland dust must be known. There are several hypotheses on the location of the source, but no current methods have been sufficient in determining the exact origin. This study explores the possibility of using elemental geochemical composition as an indicator for the dust origin. Major and trace element concentrations in loess and red clay samples from loess areas in Northern America, Europe, the Middle East, Central Asia and China were determined using handheld XRF. UCC-normalised values of major elements show similar trends for all areas, with depletion of Si, Al, Mg, K, Ti, Fe and Mn and enrichment of Ca and P in most samples. The elemental ratios Fe/Ti, Al2O3/SiO2, Al2O3/Ti, Fe/Al2O3, K2O/Al2O3, CaO/Al2O3, Rb/Sr and Zr/Rb display variations between areas, indicative of differences in weathering rates and grain sizes. The combined ratios Fe/Ti vs. K2O/Al2O3, Fe/Al2O3 or Al2O3/Ti can be used to differentiate loess from Canada, the US, central and eastern Europe, Israel and China. Central Asian loess however shows similar composition to Chinese loess. The results indicate that loess from different parts of the world have significant differences in elemental composition, which could potentially be used to differentiate between suggested sources of the Greenland dust. / Mängden stoft i isborrkärnor från Grönland varierar med förändringar i klimat, men det exakta sambandet är ännu okänt. För att kunna rekonstruera detta samband krävs att källan till stoftet är känd. Flera hypoteser finns idag kring denna källa, men inga hittills prövade metoder har kunnat urskilja ett definitivt ursprung. I detta arbete undersöks möjligheten att använda grundämnessammansättning som en indikator för stoftets ursprung. Koncentrationer av huvudelement och spårämnen i löss och röd lera från lössområden i Nordamerika, Europa, Mellanöstern, Centralasien och Kina bestämdes med handhållen XRF. UCC-normaliserade värden för huvudelement visar att områdena följer huvudsakligen liknande trender med reduktion av Si, Al, Mg, K, Ti, Fe och Mn och anrikning av Ca och P i de flesta prover. Grundämneskvoterna Fe/Ti, Al2O3/SiO2, Al2O3/Ti, Fe/Al2O3, K2O/Al2O3, CaO/Al2O3, Rb/Sr och Zr/Rb uppvisar tydlig variation mellan områden, indikativt för skillnader i vittring och kornstorlek. De kombinerade kvoterna Fe/Ti mot K2O/Al2O3, Fe/Al2O3 eller Al2O3/Ti kan användas för att särskilja löss från Kanada, USA, Central- och Östeuropa, Israel och Kina. Centralasiatisk löss uppvisar dock liknande sammansättning som kinesisk. Resultatet visar att löss från olika delar av världen har betydande skillnader i grundämnessammansättning, vilket skulle kunna användas som indikator för ursprunget till Grönlands stoft.