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Most methods for the determination of trace elements in organic matter require the sample to be brought into solution, which may be achieved by heating with strong oxidising agents such as concentrated mineral acids, to decompose the organic matrix sufficiently to render the sample soluble, whilst not necessarily achieving complete decomposition. The use of microwave heating for this purpose, using sealed vessels under pressure, was investigated for a variety of food samples. One drawback of this otherwise rapid method is the time taken to cool the vessels before opening. The use of liquid nitrogen to cool the vessel walls - before, during and after the heating cycle - was investigated, and its effect on the progress of the digestion was assessed. Another problem is the control of internal pressure, which can rise very rapidly when digesting samples of high organic content, and ways of controlling excess pressure when digesting larger samples were devised. These included the use of an open pre-digestion under reflux using a microwavetransparent coolant liquid, and the use of vessels capable of withstanding higher pressures. The latter proved more convenient as they enabled complete dissolution to be achieved in a single stage without pre-digestion, although cooling of these vessels was much slower than for the low pressure vessels, so overall sample preparation time was similar. Various methods were developed for the complete dissolution of the samples using nitric acid and hydrogen peroxide. The degree of decomposition achieved for the different methods and sample types was monitored by measurement of residual carbon in the digests. A few samples were virtually completely decomposed with nitric acid alone, while the use of hydrogen peroxide, following a nitric acid digestion, was found to reduce residual carbon substantially in the others. The undecomposed material was analysed by various methods including ultraviolet/visible spectrometry, infrared spectrometry and thin layer chromatography. Decomposition products were found to include carboxylic acids, oxalates, phosphates, nitrates and nitro-aromatics. Complete decomposition of milk powder, which proved most resistant to oxidation, was achieved by further treatment with perchloric acid. This was found necessary for anodic stripping voltammetric analysis, which required the destruction of interfering organic species for accurate determination of trace elements, unlike other techniques such as inductively coupled plasma-mass spectrometry, where complete decomposition was not required.

The aim of this study was to. examine the relationship between organic maturity and trace element geochemistry of organic rich mudstones, to assess their behaviour as sources or sinks of metals during diagenesis, and their role in mineral deposit genesis. The suite studied consisted of 193 samples from the Draupne, Heather, and Kimmeridge Clay Formations from the Norwegian North Sea and onshore UK. All three formations had above average contents of C and S, and the Draupne and Heather Formations had a low carbonate content. The Draupne Formation was particularly enriched in a number of trace elements but only Cr, Mo, Nb, and U were enriched in all three formations. After transformation of the data to avoid difficulties in interpretation, correlation analysis allowed the trace elements to be divided into three groups on the basis of their mineralogical residences. The use of a battery of geochemical and mineralogical indices demonstrated that variation in sedimentological and environmental factors were significant within the formations studied, and that the relationship between organic maturity and trace element content could not be investigated in isolation. The technique of path analysis was used to assess the strength and nature of this relationship relative to the variation due to other causes. Pb and Zn were found to increase with increasing maturity in both the Draupne and Heather Formations, and Mo was found to decrease. U was seen to decrease, and Cd to increase, in the Draupne Formation only, where they were especially abundant. It is believed that Pb and Zn were supplied by migrating basinal brines which may have acted to remove Mo and U. Other processes which may have mobilised these elements are the in situ generation of organic acids and hydrocarbons.

A summary of the fundamental principles which form the basis of proton induced X-ray emission (PIXE) analysis, proton induced gamma-ray emission (PIGE) analysis, Rutherford backscattering spectrometry (RBS) and instrumental neutron activation analysis (INAA) has been given which is followed by a brief description of the experimental facilities used in this work and their characterization. Knowledge of optimum experimental conditions is always helpful, therefore a programme has been developed to simulate the PIXE spectra and its uses have been described. Reference materials with certified elemental concentrations play an important role in ensuring the accuracy of the elemental analysis work. The FIXE technique has been applied to the analysis of new biological reference materials which consist of IAEA human diet samples and NIST leaf samples, to be introduced in the future. Homogeneity of these and two existing reference materials that is, IAEA soil-7 and Bowen's kale has also been determined at the mug scale. A subsample representative of a material is ascertained by determination of sampling factors for the elements detected in the material. Use of PIXE has been established in experimentally obtaining sampling factors for the above mentioned materials. PIGE analysis in conjunction with PIXE has been employed to investigate F and other elemental concentrations found in human teeth samples. The mean F concentration in enamel and dentine parts of teeth followed an age dependent model. The lowest F concentrations were observed in two out of three careous teeth. Concentrations of Ca and P were found to be higher in the enamel than in the dentine in all the teeth analyzed. Analysis of blood and its components in the study of elemental models in sickle cell disease in Nigerians has been carried out. A total of eight elements were detected. Comparision was made between controls and diseased groups which revealed that Cl, Ca and Cu were at significantly higher levels whereas K, Fe, Zn and Rb were at significantly lower levels in the whole blood of the sicklers as compared to the controls. Similar results were obtained for the erythrocytes except that Br was also found at significantly higher concentration in erythrocytes of the sicklers. Significantly higher concentrations of Cl, K, Fe and Cu were also observed in plasma of the sicklers as compared to that of the controls. Elemental status of the normal controls was found to be comparable to that of the Uzbekistanians (USSR) and North Americans but was better than that of the Bangladeshi population. PIXE and scanning electron microscopy (SEM) was used in the characterization of the Harmattan dust particulates collected at Kano and Ife, two cities of Nigeria. Most of the elements were found to be at higher concentrations as compared to those found in Recife (Brazil) and Toronto (Canada). The value of total suspended particulate matter (TSPM) at both collection sites was also above the relevant national (USA) air quality standards. FIXE in conjunction with RBS and INAA was employed in the analysis of soil samples taken at various depths from within and around two cement factories in Nigeria thereby detecting 31 elements. The results have been discussed with reference to elemental concentrations and Ca/Si ratio. The latter was found to offer a valid indicator of soil pollution by the cement dust.

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Chapter 1 of this thesis is a general review of published work o_ the origins and distribution of Cd, Cu, Fe, Mn and Zn in soils and their uptake and functions in plants. Chapter 2 is a synopsis of the geological history of the Fayoum of relevance to the origins of sediments at the study sties. Previous fractionation procedures, and a proposed modification to improve the determination of carbonate-bound elements are discussed in Chapter 3, while other analytical procedures are described in Chapter 4. Results of general soil analyses, of the fractionation analyses and useful correlation matrices, are tabulated together (for convenience in Chapter 5) and are discussed in detail in the following chapter. Texture was a crucial factor, finer-textured soils generally having lower pH and higher organic matter contents, although the latter were generally greater closer to the surface. Clay and silt contents were highly correlated, probably reflecting water sorting in the Fayoum, which aided the texture/drainage effect. Drainage (i.e. texture) was apparently very important in the fractionation chemistry of elements influenced by redox-reactions, i.e. Fe and Mn, and elements for which distribution depended upon Fe and Mn oxides (e.g., Zn) to a significant extent. Clay was especially important to the concentration of crystalline and amorphous iron oxides. Cd and Cu showed marked surface accumulation, especially in the exchangeable fractions, for many profiles, probably through pollution. The Cu content of organic matter was strikingly uniform at the Fayoum. Amorphous and crystalline Fe oxides seem to be especially important in the distribution of Zn. Clay Cd, Fe and Zn and, to a lesser extent, Cu and Mn contents were relatively constant, suggesting uniform origins. Chapter 7 describes a pot experiment on the soils using barley as a test crop, aimed at relating uptake to the fractionation results. Interpretation was complicated by a dominant effect of soil salinity. Chapter 8 suggests future related research.

Bibliography: pages 94-99. / This thesis describes work performed to establish and demonstrate a quantitative trace element microanalysis technique for geological material using protons accelerated by the Van de Graaff Accelerator at the National Accelerator Centre (NAC) in Faure near Cape Town. The method relies on the analysis of Proton Induced X-ray Emission (PIXE) spectra, interpreted with the help of the GeoPIXE software package. The use of the Si(Li) energy dispersive detector provides simultaneous multi-element detection at the parts-per-million (ppm) level, and a scanning beam facility permits trace element distributions to be studied at these levels. The calibration of the detector efficiency and the thicknesses of selectable X-ray attenuating filters was performed using pure elemental samples. This involved the accurate determination of the target to detector distance, the thickness of the active volume of the Si(Li) detector crystal, the thicknesses of all the absorbing layers between the sample and the detector crystal, and the assessment of the effects of incomplete charge collection in the detector.

The Western Gneiss Region (WGR) in Norway is home to some of the world’s most spectacular exposures of high pressure (HP) and ultrahigh pressure (UHP) eclogites. Despite extensive petrological studies into their pressure, temperature and time (PTt) histories, relatively few have reported on their trace element compositions. Such data can be used to supplement our understanding of the provenance and history of Norwegian eclogites, as well as to further our understanding of trace element fluxes during HP to UHP metamorphism in subduction zone settings. In order to address this shortfall in data availability, the first step was to investigate and apply the best dissolution techniques for preparing eclogite samples for chemical analysis. Eclogites commonly contain up to a few weight percent rutile (TiO2), which is known to be an important host for a variety of major and trace elements (e.g. Ti, Nb and Ta). However, typical rock digestion procedures are incapable of dissolving rutile, and thus may lead to inaccurate measurements. It was found that that total dissolution of rutile can be achieved by dissolving samples in sealed pressure vessels at increased pressures and temperatures, ultimately leading to greatly increased data accuracy for analyses of any rutile-bearing lithology. The solutions were analysed by standard ICP-MS techniques and the results compared to analyses of powders by XRF spectrometry. Our high-accuracy and high-precision data were subjected to immobile trace element discriminant analyses that suggested eclogites belonged to three broad geochemical groups: eclogites with mid ocean ridge Basalt (MORB)-like composition; eclogites with arc-like composition; and eclogites with geochemical signatures significantly perturbed by metamorphism. The geochemistry of eclogites in the first two groups are shown to likely reflect protolith composition, and as such we used model protolith compositions to calculate estimated element mobilities (EMMs) for those elements considered relatively mobile during metamorphism. It was not possible to determine protoliths for eclogites in the third category using trace elements alone. Finally, the trace element geochemistry of a large number of separated eclogite-hosted rutiles was studied. The data collected were used to demonstrate that rutile contains significant amounts of the whole-rock’s high field strength element (HFSE) budget, and may exert significant control on the HFSE composition of passing hydrothermal fluids. Furthermore, Zr-in-rutile thermometry (ZRT) was applied to separated rutiles. This temperature information was used to better our understanding of the thermal history of the WGR, as well as to create a map of eclogite temperatures in the Nordfjord-Statlandet area. This high-resolution thermal map of arguably the most important area of the WGR, supports current interpretations that during the Caledonian Orogeny the leading edge of the Baltica plate was consumed in a northwest to north-northwest-dipping subduction zone under Laurentia. Furthermore, isotherms on this map mimic several major fold hinges in the region rather well, thus providing support to the hypothesis that such structures were most likely formed during the collapse of the Scandinavian Caledonian Orogen after the peak metamorphism of most eclogites.