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Monomethylmercury (CH3Hg+ and its complexes; hereafter referred to as MeHg) in the intracellular environment is known to be predominantly bonded to thiol-containing biomolecules but the identities of these target biomolecules remain unknown. Some evidence suggests that binding with glutathione acts as a detoxification mechanism for MeHg, while binding with L-cysteine permits MeHg transport across the blood–brain barrier resulting in neurotoxicity. However, the occurrence of these complexes in biological tissues has not been confirmed analytically, and little is known about their kinetic stability. In this thesis, methylmercury L-cysteinate (CH3HgCys) and methylmercury L-glutathionate (CH3HgGlu) were synthesized and structurally characterized by proton nuclear magnetic resonance (1H NMR), electrospray ionization mass spectrometry (ESI-MS), and X-ray crystallography. A new analytical method was developed combining high performance liquid chromatography with inductively coupled plasma mass spectrometry (HPLC-ICPMS). The method was capable of separating and analyzing CH3HgCys and CH3HgGlu complexes, as well as CH3HgX and inorganic HgX (X = H2O, OH-, or Cl-), with detection limits at the sub-micromolar levels. Using a new enzymatic hydrolysis method to isolate MeHg species in biological tissues, the HPLC-ICPMS method was successfully applied for the determination of MeHg speciation in the muscle tissue of dogfish (Squalus acanthius). These results provide the first analytical evidence for the presence and dominance of CH3HgCys in fish muscle. The analytical method was also used to study the kinetic stability of CH3HgCys and CH3HgGlu under a range of environmental and intracellular conditions. In general, CH3HgGlu was more stable than CH3HgCys under light exposure or darkness. The stability of both compounds decreases dramatically with increasing ionic strength (I). Half-life of CH3HgCys decreases from 34.1 h (I = 0.01 M) to 5.9 h (I = 0. 5 M) and the half-life of CH3HgGlu decreases from 259 h (I = 0.01 M) to 35.9 h (I = 0. 5 M). Suggesting major differences in their cycling in freshwater (I < 0.01M), seawater (I ≈ 0.7M) and body fluids (I ≈ 0.16 M). The analytical technique and the findings from this thesis research provide a new analytical framework for the study of MeHg speciation in natural waters, and the metallomics of MeHg in biological systems.

Monomethylmercury (CH3Hg+ and its complexes; hereafter referred to as MeHg) in the intracellular environment is known to be predominantly bonded to thiol-containing biomolecules but the identities of these target biomolecules remain unknown. Some evidence suggests that binding with glutathione acts as a detoxification mechanism for MeHg, while binding with L-cysteine permits MeHg transport across the blood–brain barrier resulting in neurotoxicity. However, the occurrence of these complexes in biological tissues has not been confirmed analytically, and little is known about their kinetic stability. In this thesis, methylmercury L-cysteinate (CH3HgCys) and methylmercury L-glutathionate (CH3HgGlu) were synthesized and structurally characterized by proton nuclear magnetic resonance (1H NMR), electrospray ionization mass spectrometry (ESI-MS), and X-ray crystallography. A new analytical method was developed combining high performance liquid chromatography with inductively coupled plasma mass spectrometry (HPLC-ICPMS). The method was capable of separating and analyzing CH3HgCys and CH3HgGlu complexes, as well as CH3HgX and inorganic HgX (X = H2O, OH-, or Cl-), with detection limits at the sub-micromolar levels. Using a new enzymatic hydrolysis method to isolate MeHg species in biological tissues, the HPLC-ICPMS method was successfully applied for the determination of MeHg speciation in the muscle tissue of dogfish (Squalus acanthius). These results provide the first analytical evidence for the presence and dominance of CH3HgCys in fish muscle. The analytical method was also used to study the kinetic stability of CH3HgCys and CH3HgGlu under a range of environmental and intracellular conditions. In general, CH3HgGlu was more stable than CH3HgCys under light exposure or darkness. The stability of both compounds decreases dramatically with increasing ionic strength (I). Half-life of CH3HgCys decreases from 34.1 h (I = 0.01 M) to 5.9 h (I = 0. 5 M) and the half-life of CH3HgGlu decreases from 259 h (I = 0.01 M) to 35.9 h (I = 0. 5 M). Suggesting major differences in their cycling in freshwater (I < 0.01M), seawater (I ≈ 0.7M) and body fluids (I ≈ 0.16 M). The analytical technique and the findings from this thesis research provide a new analytical framework for the study of MeHg speciation in natural waters, and the metallomics of MeHg in biological systems.

A relationship between the sulphur valence of a melt and f 02 has been determined. The relationship has been used to determine the f O2 conditions under which melt inclusions were trapped in andesitic magmas before magma mixing, and of a slowly cooled pyroclastic flow in which Fe-Ti oxide phases have re-equilibrated. The results help distinguish two trends in lavas from Lascar Volcano: In one, the melt fO2 is buffered by iron redox ratio, while in the other f02 is buffered by S02-H2S in a comagmatic vapour phase. The behaviour of sulphur was experimentally investigated in hydrous phonolitic and rhyolitic melt at 930 °C and 0.5 to 4 kbar. Pyrrhotite is stable under reducing conditions in both melts, and immiscible FeS sulphide liquid is stable under certain conditions of pressure and f S2 at 5 log units above the Ni-NiO buffer. Anhydrite and Srich sodalite are the usual magmatic S-bearing phase under oxidising conditions in rhyolitic and phonolitic melts respectfully. Melt sulphur content is positively correlated with f 02 and f S2. pressure has no significant effect for the conditions investigated. A thermodynamic model has been derived that successfully reproduces the results of this study and of a previous study. The partitioning of sulphur between vapour and melt is a function of f 02, f SZ, phase stabilities and mass balance constraints. Sulphur solubilities and f02 were determined for a suite of back arc basin basalts (BABB). The BABB samples follow two trends: those with low values of f02 have high S contents, whereas more oxidised samples have lower sulphur contents. The solubility behaviour can be described by sulphide-sulphate melt-vapour equilibria. The f02 of the oxidised samples implies that subducted material was incorporated into their magmatic source, a hypothesis supported by major and trace element studies of the samples

The properties of an element are highly dependent on its chemical form, it’s called elemental speciation. This study evaluates the arsenic species found in a range of food stuffs together with growing environments and toxicity issues. Total arsenic concentrations in fish tissue and vegetable crops were determined by ICP-MS following microwave-assisted acid digestion using nitric acid/hydrogen peroxide, trypsin and cellulase enzymatic extraction procedures. The extracted arsenic species were then quantified using HPLC-ICP-MS. A dilute nitric acid (1 % (v/v)) digestion procedure was also used to extract arsenic species from rice and the different parts (root, skin, stem, leaf and grain) of a range of plant crops. The study was extended to include the aqua-regia extractable arsenic content of the soils collected from the area where the plants had been cultivated in the Kurdistan region of Iraq. Irrigation water was also investigated, but found to contain low levels of arsenic. An anion-exchange HPLC-ICP-MS method was developed, using sulphate and phosphate, for the separation and quantification of AsB, MMA, DMA, InAsIII and InAsV. The results obtained for fish samples were in the range of 3.53-98.80 µg g-1 (dry weight) with non-toxic AsB being the predominant species. The InAsV concentration was in the range of 0.1-1.19 µg g-1 for all fish species except for the John Dory which was below the limit of detection (0.027 µg g-1). Total arsenic, arsenic species, and total multi-elements (including Ag, Al, B, Ba, Be, Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, Sb, Se, Si, Ti, V and Zn) were determined in rice samples from Kurdistan, Iraq and other regions of geographical origin. The transport of arsenic from the soil and irrigation water into roots, stem, leaf and subsequently into the grain or bean of the plants is important when assessing the potential health risks from food crops. For the soil sample, InAsV was found to be the major species with smaller quantities of InAsIII . After applying a full BCR sequential extraction procedure to the soils, it was found that 7.87 - 21.14 % of the total arsenic was present in an easily acid-soluble extractable form. Finally, a novel method was developed to measure total arsenic and arsenic species associated with vegetative DNA. In rice plant, it was found that InAsV incorporated within the DNA molecule in which it could replace phosphate. It was also found that the concentration of InAsV associated with DNA molecule decreased with decreasing total arsenic in the rice plant from the root to the leaf.

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Peats and organic-rich soils are a key part of the global carbon (C) cycle due to their sequestration and storage of atmospheric C as organic matter. Atmospheric deposition as a result of human activities has led to increased inventories of lead (Pb) and mercury (Hg) in UK peats and organic-rich soils. Ombrotrophic peat bogs, which receive all their nutrients and pollutants from the atmosphere, provide a historic record of Pb and Hg deposition within their solid phase. Organic-rich forest soil systems can also act as sinks for anthropogenic Pb but vertical transport of Pb can distort these temporal records. The long-term outlook may, however, be affected by processes which lead to decomposition of organic matter e.g. drying out of peatlands and soils due to climatic change, since these may release Pb into the aqueous phase and volatile Hg to the atmosphere. The associations and speciation of Pb and Hg within peats and organic-rich soils are not well understood but are key to understanding both the potential for release of these pollutants into other environmental compartments and the risks to ecosystems and human health posed by such a release. Investigation of 4 sites in central Scotland showed that, depending on vertical depth, ~40-99% of Pb in ombrotrophic peat was in association with large (0.22 μm – 100 kDa) humic molecules. Near-surface regions where intact plant material had not yet undergone complete humification showed the lowest proportion of Pb-humic association. Historical Pb deposition was retained to similar degrees across each site with recorded inventories to 1986 of 0.340-0.561 g m-2. However, perturbation of the 206Pb/207Pb isotope ratio profile at Glentress forest indicated that limited migration of petrol-sourced Pb may be occurring. Similarly, perturbation of the 210Pb profile at Auchencorth Moss, in addition to discrepancies in the apparent time period in which peak Pb deposition occurred, indicated that Pb may also be subject to migration within this ombrotrophic system. With respect to Hg, between-site differences in speciation were observed. For example, Hg2+ represented < 25% of the total Hg species in the top 10 cm of solid phase ombrotrophic peat but > 50% of the total in forest soil. In contrast, aqueous phase Hg was entirely in the inorganic form across all sites. The occurrence of a solid phase [Hg] peak in layers corresponding to the ~1955 height of coal burning, in addition to the narrow range of peatland Hg inventories to 1950 (2.20-3.23 g m-2) provide evidence that Hg deposition records may be maintained in organic-rich systems to a greater degree than previously assumed. Differences observed in the associations of Pb and the speciation of Hg between the surface vegetation of ombrotrophic bogs and the underlying peat suggests that plants play an integral role in the biogeochemical behavior and sequestration of Pb and Hg in these terrestrial systems.

Philosophiae Doctor - PhD / Variation in sympatric and allopatric populations is believed to be a precursor to eventual speciation. The dispersion of genes from one gene pool into another is prevented by various processes, including the founder effect, sexual selection, ecological differences and random genetic divergence. Examining patterns of intraspecific variation in phenotypic and genotypic traits may thus provide valuable insights into the processes that govern species origination. Bladder grasshoppers (Orthoptera; Pneumoroidea) are an ideal model system to investigate patterns of geographic and ecological divergence due to their high host plant specificity, low dispersal and distinctive acoustic signals. This dissertation investigates intraspecific diversification in the bladder grasshopper Bullacris unicolor (Orthoptera: Pneumoroidea). Recent research on this species has shown significant intra- and inter-population variation in male advertisement calls and morphological characters. However, the exact cause of this variation has remained unclear. Furthermore, a previous study showed that the calls of B. unicolor from one particular population are highly differentiated from other populations, possibly due to the effects of anthropogenic noise. Here we aim to examine the drivers of diversity within Bullacris unicolor by embracing a multidisciplinary approach that encompasses the effects of environmental factors, genetics, anthropogenic noise and host plant associated divergence.