X-ray fluorescence is a well-understood phenomenon in which irradiation of certain materials, such as gold, with x-rays causes the emission of secondary x-rays with characteristic energies. By performing computed tomography using these fluorescence x-rays, the material of interest can be imaged inside an object. Our research group has already demonstrated that x-ray fluorescence computed tomography (XFCT) imaging using a typical 110 kVp microfocus x-ray tube is feasible for a small animal-sized object containing a distribution of a solution of low concentration gold nanoparticles. The primary goal of this thesis work was to study the effect of source x-ray energy spectra on gold fluorescence detection using the XFCT system. A computational approach using the Monte Carlo method was used. First, a computational model was created using the Monte Carlo N-Particle (MCNP) transport code based on the experimental setup of the pre-existing XFCT system. Simulations were run to verify the validity of the MCNP model as an accurate representation of the actual system by means of comparison with experimentally-obtained data. Finally, the model was used for further purely computational work. In the MCNP model, the source spectrum was changed to reflect several theoretical and experimentally obtained options. The effect of these changes on gold fluorescence production was documented and quantified using the signal-to-background ratio and other qualitative measures. The results from this work provided clues on how to improve the detection of fluorescence photons from gold nanoparticle-loaded objects using the XFCT system. This will benefit future research on the development of the XFCT system in the context of making it more feasible for gold nanoparticle-based preclinical molecular imaging applications.

This study was conducted to investigate the urban geochemistry of the city of Windsor (Ontario) and to provide added source apportionment information to work being carried out by the Canadian government. The goal of this study was to investigate the distribution, spatial variation and sources of manganese in urban Windsor soil. The literature indicates that human exposure to high levels of manganese, via inhalation, can cause respiratory and/or neurological effects. At the outset of the present study it was first hypothesized that vehicular traffic was the dominant source of anthropogenic manganese. An alternative hypothesis was that there were multiple anthropogenic sources of manganese in Windsor. The sample collection scheme was designed to determine (1) the current and background soil concentrations of manganese in Windsor, (2) the spatial distribution of manganese in order to reveal sources of manganese, and (3) the manganese content of moss-sequestered airborne particles, which can potentially deposit onto the soil surface, using low-technology biomonitoring. The first phase of the study consisted of a preliminary soil survey which identified elevated areas of soil manganese concentrations. During this survey, the field efficiency of a field portable X-ray fluorescence (FPXRF) instrument, as well as sample preparation methods were evaluated. Efficiency of the FPXRF was determined by comparison to ICP-MS, a traditional trace element analysis method. The preliminary soil survey identified several areas of elevated (ranging from 884 to 2390 ppm) soil manganese which were further investigated during the second, more complete, soil survey. The moss biomonitoring technique of using moss bags was used to collect airborne particles for semi-quantitative analysis. Analysis of soil samples included total manganese and other trace elements, pH, moisture and carbon content, and manganese speciation. Urban Windsor soil manganese distribution revealed both natural and anthropogenic sources of soil manganese and three distinct soil sample types, transect, baseline and natural. In general, manganese in Windsor had a west-to-east trend of decreasing levels in soil and moss-sequestered airborne particles. The latter showed a modern-day elemental signature while the former (collocated soil) a legacy elemental signature. It was concluded that both the FPXRF instrument and the moss biomonitoring technique can be useful screening tools in studies of urban environments.

X-ray fluorescence (XRF) detection of heavy metals is a cost- and time-effective method for investigation of polluted areas. Compared to laboratory analysis, XRF analysis is limited by high detection limits and uncertainties in some situations. Preparation of samples is known to affect the results of measurements. The purpose of this thesis is to bring a deeper understanding of how different factors affect the results of XRF-analysis. A large number of measurements have been made with the instruments Niton XLt 700 and Niton Xli 700. Results from measurements of lead, zinc and copper have been analysed. This study has shown that a greater moisture content will give a lower measured concentration for the same sample. If the moisture content is known, it is possible to make good approximations of concentrations in dry samples. No obvious differences were found between different metals. Proper homogenisation of samples was found to be one of the most critical issues. It should be noted that laboratories do not usually homogenise samples prior to analysis, so samples sent for laboratory verification should therefore be homogenised before sending. Sample preparation, including drying, sieving to finer grain-sizes and analysing in a special sample cup was found to increase the measured concentrations and decrease the variation between measurements. The concentrations differed with different sample matrices and with sample preparation. Because of the differences, measurements should always be correlated with laboratory analysis before any conclusions can be made. In situations when metals are well within detection range of the XRF instrument, the only preparation needed is in most cases homogenisation. If metal levels are just at the limit, or just below the detection limit, further preparations of samples should be made. When drying samples makes detection possible, more preparation is usually not worth the effort. If detection limits still are a problem after drying, the samples should be sieved and analysed in sample cups. In situations where concentrations still are below the detection limit when analysing in sample cups, or if the measurements are disturbed for other reasons, another method than XRF-analysis must be used. When XRF analysis is possible, the method is preferable compared to only laboratory analysis. This cost- and time effective method makes a larger number of measurements possible, and gives a more complete overview of a polluted area. / Analys med röntgenfluorescensdetektor (XRF) är en snabb och kostnadseffektiv fältmetod för detektion av tungmetaller i mark. Nackdelen är att mätningarna inte är tillförlitliga i alla sammanhang och att detektionsgränsen för många ämnen är förhållandevis hög. Det är sedan tidigare känt att olika former av provbearbetning påverkar mätresultaten. I detta examensarbete har undersökts hur olika faktorer påverkar mätresultaten vid analys av jordprover med XRF instrument. Faktorerna som undersökts är inverkan av vattenkvot, kornstorlek, provpåsar och olika provbearbetningsmetoder. Vid provbearbetningsförsöken skickades prover även in till externt laboratorium för jämförande analys. Metaller som undersökts är bly, zink och koppar. Vid undersökningen konstaterades att en ökad vattenkvot ger upphov till lägre mätvärden. Vid kännedom om vattenkvot kan halt per torrsubstans med god överensstämmelse uppskattas utifrån mätningar på fuktiga prov. Är precisionskraven stora och vattenkvoten varierande och okänd bör dock proverna torkas innan mätningar görs. Ingen avsevärd skillnad sågs mellan de olika metaller som undersöktes. Vid undersökningen om provbearbetningens betydelse visade det sig att homogeniseringen av proverna är mycket viktig, inte minst av prover som skickas till laboratorieanalys. Ökad provbearbetning med torkning och siktning till mindre kornstorlek tenderar att ge högre mätvärden med XRF instrument. Storleksmässigt är mätvärden vid obearbetade prov mest överensstämmande med laboratorieanalys. Mest skiljer sig analys på finsiktade prover i provkopp. Korrelationsmässigt finns i en del fall en tendens till bättre överensstämmelse med mer bearbetade prov. Den största vinsten med ökad bearbetning av prover konstaterades i detta arbete vara att mark med lägre metallkoncentrationer då kan analyseras. I de fall där halterna av metaller ligger väl inom XRF instrumentets detektionsområde visade det sig att det oftast är tillräckligt att endast homogenisera proverna innan analys görs. I de fall där koncentrationen av metaller är på gränsen till vad XRF instrumentet kan detektera rekommenderas att proverna torkas, eller om nödvändigt torkas, siktas och analyseras i provkopp. Där nivåerna av metaller ligger under detektionsgränsen för XRF instrument trots provbearbetning, eller där andra ämnen till exempel järn stör mätningarna, måste en annan analysmetod väljas.

The objective of this research project was to establish a better understanding of the mechanism(s) and route(s) by which selenium (Se) may enter an aquatic ecosystem that has been receiving treated metal mine effluent from an upstream uranium milling operation. Synchrotron based X-ray absorption spectroscopy (XAS) and X-ray fluorescence (XRF) imaging, which require little sample pre-treatment, were employed to study the speciation and distribution of Se in complex sediment and benthic invertebrates samples collected from the field. Laboratory based inductively coupled plasma mass spectrometry (ICP-MS) provided quantitative Se concentrations. Samples were taken from Fox Lake and Unknown Lakes, downstream of the mill, and Yeoung Lake as a control. The variation in Se speciation as a function of depth in intact sediment cores may provide insight into the species of Se available to the sediment dwelling benthic invertebrate communities. Therefore, a custom sample holder was designed to facilitate analysis of intact sediment cores at cryogenic temperatures. Additionally, laboratory reared chironomids were water-exposed to various Se species, to compare their Se speciation and localization to chironomids collected in the field. The successful demonstration of the custom sample holder and viable use of synchrotron XAS and XRF in studying sediment and chironomid samples have revealed that biologically relevant Se forms were present in sediment at depths accessible by the benthic invertebrate community. These Se forms included selenomethionine-like and selenite species, and to a lesser degree elemental Se; an increased proportion of reduced Se species was observed as depth increased. Other elements measured concurrently with Se included As, Zn, Cu, Ni, Fe, and Mn, providing an estimation of the redox boundary found both in Fox and Unknown Lake, as well as suggesting the presence of iron species that could aid in the reduction of Se. Field and laboratory reared chironomids showed similar Se species, and XRF imaging revealed the localization of Se in 4 distinct regions: head capsule, brain, salivary glands, and gut lining. Overall, the project has provided important insights into the interactions of Se with this aquatic ecosystem, which may have future applications in cold water systems with elevated Se concentrations.

Friedreichs ataxia (FRDA) is a progressive spinocerebellar ataxia (SCA) inherited as an autosomal recessive trait. The neurodegeneration, cardiomyopathy, diabetes mellitus and skeletal deformities characteristic to FRDA result from a deficiency in the mitochondrial protein frataxin. Frataxin chaperones iron to heme and iron-sulfur clusters and its deficiency causes mitochondrial iron accumulation and oxidative stress.<p> To address the effect of frataxin deficiency on mitochondrial iron chemistry, mitochondria were isolated from FRDA and control fibroblasts. X-ray absorption spectroscopy showed that ferrihydrite was the predominant form of iron in both. Near edge analysis showed that the ferrihydrite in the FRDA mitochondria resembled the highly organized ferrihydrite of ferritin. Western blotting confirmed that FRDA mitochondria had 3-fold more holoferritin containing stainable iron. I conclude that mitochondria from FRDA fibroblasts mineralize excess iron as ferrihydrite within mitochondrial ferritin.<p> To address how cellular iron dysregulation affected metal distribution in brain and spinal cord, a new synchrotron imaging technique, rapid-scanning x-ray fluorescence (RS-XRF) was employed and validated. Brain structures were readily identified by their unique metal content and distribution. This showed that RS-XRF could be used to reveal metal pathologies associated with diseases of metal metabolism such as FRDA. Since human FRDA tissues were not available for a detailed study, RS-XRF was employed to study the distribution of metals in normal cerebellum, a major site of FRDA-associated neurodegeneration, and to localize and quantify metals in the brain and spinal cord from a patient with a SCA of unknown aetiology. The motivation for this work is the prospect of future systematic studies on metal pathology in neurodegenerative diseases with direct application to FRDA. Novel findings arising from this work were the metal segmentation of the dentate nucleus, the high copper content of the olivary region and the different metal content of lesions at different stages of neurodegeneration. My results suggest that not only iron, but also copper and zinc may play a role in the physiopathology of neurodegeneration. Therefore, all three metals should be investigated in FRDA and other SCA of both known and unknown aetiologies to identify possible new therapeutic targets.

This study was conducted to investigate the urban geochemistry of the city of Windsor (Ontario) and to provide added source apportionment information to work being carried out by the Canadian government. The goal of this study was to investigate the distribution, spatial variation and sources of manganese in urban Windsor soil. The literature indicates that human exposure to high levels of manganese, via inhalation, can cause respiratory and/or neurological effects. At the outset of the present study it was first hypothesized that vehicular traffic was the dominant source of anthropogenic manganese. An alternative hypothesis was that there were multiple anthropogenic sources of manganese in Windsor. The sample collection scheme was designed to determine (1) the current and background soil concentrations of manganese in Windsor, (2) the spatial distribution of manganese in order to reveal sources of manganese, and (3) the manganese content of moss-sequestered airborne particles, which can potentially deposit onto the soil surface, using low-technology biomonitoring. The first phase of the study consisted of a preliminary soil survey which identified elevated areas of soil manganese concentrations. During this survey, the field efficiency of a field portable X-ray fluorescence (FPXRF) instrument, as well as sample preparation methods were evaluated. Efficiency of the FPXRF was determined by comparison to ICP-MS, a traditional trace element analysis method. The preliminary soil survey identified several areas of elevated (ranging from 884 to 2390 ppm) soil manganese which were further investigated during the second, more complete, soil survey. The moss biomonitoring technique of using moss bags was used to collect airborne particles for semi-quantitative analysis. Analysis of soil samples included total manganese and other trace elements, pH, moisture and carbon content, and manganese speciation. Urban Windsor soil manganese distribution revealed both natural and anthropogenic sources of soil manganese and three distinct soil sample types, transect, baseline and natural. In general, manganese in Windsor had a west-to-east trend of decreasing levels in soil and moss-sequestered airborne particles. The latter showed a modern-day elemental signature while the former (collocated soil) a legacy elemental signature. It was concluded that both the FPXRF instrument and the moss biomonitoring technique can be useful screening tools in studies of urban environments.

Friedreichs ataxia (FRDA) is a progressive spinocerebellar ataxia (SCA) inherited as an autosomal recessive trait. The neurodegeneration, cardiomyopathy, diabetes mellitus and skeletal deformities characteristic to FRDA result from a deficiency in the mitochondrial protein frataxin. Frataxin chaperones iron to heme and iron-sulfur clusters and its deficiency causes mitochondrial iron accumulation and oxidative stress.<p> To address the effect of frataxin deficiency on mitochondrial iron chemistry, mitochondria were isolated from FRDA and control fibroblasts. X-ray absorption spectroscopy showed that ferrihydrite was the predominant form of iron in both. Near edge analysis showed that the ferrihydrite in the FRDA mitochondria resembled the highly organized ferrihydrite of ferritin. Western blotting confirmed that FRDA mitochondria had 3-fold more holoferritin containing stainable iron. I conclude that mitochondria from FRDA fibroblasts mineralize excess iron as ferrihydrite within mitochondrial ferritin.<p> To address how cellular iron dysregulation affected metal distribution in brain and spinal cord, a new synchrotron imaging technique, rapid-scanning x-ray fluorescence (RS-XRF) was employed and validated. Brain structures were readily identified by their unique metal content and distribution. This showed that RS-XRF could be used to reveal metal pathologies associated with diseases of metal metabolism such as FRDA. Since human FRDA tissues were not available for a detailed study, RS-XRF was employed to study the distribution of metals in normal cerebellum, a major site of FRDA-associated neurodegeneration, and to localize and quantify metals in the brain and spinal cord from a patient with a SCA of unknown aetiology. The motivation for this work is the prospect of future systematic studies on metal pathology in neurodegenerative diseases with direct application to FRDA. Novel findings arising from this work were the metal segmentation of the dentate nucleus, the high copper content of the olivary region and the different metal content of lesions at different stages of neurodegeneration. My results suggest that not only iron, but also copper and zinc may play a role in the physiopathology of neurodegeneration. Therefore, all three metals should be investigated in FRDA and other SCA of both known and unknown aetiologies to identify possible new therapeutic targets.

The primary aim of the work presented in this thesis is to elucidate novel information regarding the uptake, storage, distributions, and functions of both copper and zinc in mammalian cells by predominantly using a combination of the high resolution imaging modalities, synchrotron radiation X-ray fluorescence microscopy (SXRF) and standard fluorescence imaging. Results from studies using cell permeable, metal ion selective fluorescent probes suggested the presence of labile pools of copper and zinc localized within the mitochondria and Golgi apparatus. Furthermore, SXRF imaging of a cell line defective in the copper transporter, Atox1, revealed intriguing differences in the Cu distribution of Atox1-/- cells compared to the corresponding wild-type cells. Finally, spatially well-resolved SXRF elemental maps of single, adherent mouse cells revealed remarkable changes in the distributions of both zinc and copper as the cells progressed through the cell cycle. Taken together, findings suggested major roles for copper and zinc within a native biological setting.

This research developed an on-line measurement systemfor determining the amount of fluorochemicals on carpet fibers using energy-dispersive X-ray fluorescence (EDXRF).This system is designed as a complementary tool to an existingchemical burn test certified by the American Association ofTextile Chemists and Colorists (AATCC), which is performed off-line on randomly selected carpet samples and time consuming.This research reviewed XRF principles and determined parameters that affect XRF spectra such as measurement time, measurement number, X-ray tube voltage, X-ray tube current, primary beam filter, and carpet characteristics. For this application, XRF calibrations must be performed for carpets of all styles and types. However, preparing actual carpet calibration samples is expensive. This research introduced a methodology to synthetically generate reference spectra using XRF spectra from standard fluorochemical stock solution samples and from base carpet samples for each carpet type to be tested. Thus, actual, physical standards are not required for each carpet type or style. This study showed that the synthetically generated XRF spectra alone were not always sufficient to guarantee the confidence interval required by the certified AATCC test. Thus, it is recommended that for on-line implementation, burn test results should be used to create a historical data base for each carpet type to reduce margin of error for calibrations generated from the synthetic spectra.

Mercury (Hg) compounds are some of the most toxic compounds of any heavy metal on earth. Due to long-range transport from point sources Hg can be found world-wide in air, soil, water, and living organisms. Mercury compounds can cause a number of adverse effects, with the unborn fetus, infants, and children being most susceptible. Zebrafish (Danio rerio) are an excellent vertebrate model system for toxicological studies, including developmental effects. The overall objective of this research was to investigate the effects of inorganic forms of Hg in zebrafish larvae. Unique accumulation patterns were observed using synchrotron X-ray fluorescence imaging after zebrafish were exposed to one of four Hg compounds (i.e. mercuric chloride, mercury bis-L-cysteineate, methylmercury chloride, methylmercury L-cysteineate). Specifically, we noted chemical form dependant and tissue-specific Hg accumulation including the sensory cells of the olfactory epithelia and the neuromasts. Phenylthiourea (PTU) is commonly used to block zebrafish melanogenesis to generate transparent larvae to aid with enhanced visualization of immunohistochemical and vital stains. It was determined that PTU dramatically alters Hg toxicity through chemical interaction with Hg so that further studies were conducted in the absence of PTU. To investigate the effects of Hg on primary neurons, the immunohistochemistry protocol using anti-acetylated tubulin was performed and the results demonstrated that mercuric chloride damages primary neurons particularly in the olfactory pits. To study potential detoxification of Hg in zebrafish we examined the efficacy of two sequestration agents, dimercaptosuccinic acid and alpha lipoic acid, as well as endogenous selenium. The levels of Hg were not significantly lower following treatment with either sequestration agent under the conditions used in this research. Previous work examining the antagonistic relationship between Hg and selenium has been conducted by dosing animals with both Hg and selenium (Se). We discovered a mixed chalcogenide of the general form HgSxSe(1-x) forming in vivo following exposure to mercuric chloride without the addition of selenium. Indeed the selenium may have been remobilized from natural stores in the pigment spots. The research presented herein demonstrates that the target tissues for Hg depend strongly on chemical form. In particular inorganic Hg can accumulate in a number of important tissues including sensory systems. The formation of insoluble and non-toxic HgSxSe(1-x) in zebrafish larvae suggests that endogenous selenium may play critical roles in modulating toxicity.