This study used LA-ICP-MS on a documented sample of modern teeth to sample from a continuous line across the cementum increments thus creating a temporal line graph of the elemental composition against distance. The knowledge of cementum was extended through (1) a more complete elemental composition analysis and (2) the relation of element distribution to the ultrastructure structure throughout the life of a tooth. This study was exploratory and demonstrated that lead, zinc, mercury, and barium follow the same general line of changes, and most likely represent changes in health and exposure to these metals in the general environment. Copper, manganese and vanadium varied very little. Technological limitations prevented the examination of element levels in any one annulation.

Mercury (Hg) is a known neurotoxin that is often found in concentrations exceeding safe consumption guidelines in aquatic biota. This is evident in northern Canada, where northerners consume significant amounts of animals such as beluga, seals and burbot. In the Mackenzie River Basin, recent increases in Hg concentration in many of these animals over the past 25 years have been observed. The warming climate, and with it, the changing carbon cycle, are hypothesised in this thesis to play a role in the increases. Within the context of the two major zones (mountainous and peatland), with distinct geomorphology, hydrology and geology, traditional fossil fuel exploration methods (Rock-Eval pyrolysis, organic petrography) have been employed in a novel manner on recent sediments to qualify and quantify the OM and several geochemical analyses have been used to determine the geochemical sources of Hg. The mountainous zone is composed mostly of refractory OM, from forest fire char and heavily reworked OM. It also contains, and fluxes, most of the Hg, which derives from oxidative weathering and erosion of widespread sulfide minerals. However, Hg from this zone is in chemical forms of limited bioavailability. The peatland zone has a greater proportion of labile OM, with higher concentrations of DOC and algal-derived OM. Lake-fed tributaries in this zone contain even higher proportions of labile OM. At one of these sites, the sediment core record shows that Hg has been increasingly associated with labile OM over time, due to increasing primary productivity accelerated by climate change, and is resulting in an increase in scavenged Hg. The temporal trend in algal-bound Hg in the sediment record matches very well with the temporal trend of Hg in burbot sampled from the area, providing one of the first and strongest lines of evidence for the climatic impact on Hg bioaccumulation in Arctic ecosystems.

Hyperthermophilic proteins are of great interest in both the academic and industrial world in understanding how these proteins are capable of retaining their biological activity under such harsh environmental conditions. This thesis studies a tetrabrachion stalk domain from Staphylothermus marinus, know as Right Handed Coiled Coil (RHCC). This protein is of interest due to its extreme thermostability and its affinity for heavy metals. We aim to better understand the reason for the extreme thermal stability of the protein and to take advantage of the proteins affinity for heavy metals with a view to developing a novel approach to bioremediate Hg2+, a major environmental pollutant. Our results clearly indicated that the protein is more thermostable in alkaline conditions in comparison to acidic conditions. This observation can be explained by careful inspection of the high resolution structure. Our data also clearly show that RHCC is able to bind ionic mercury compounds such as mercury nitrate and dipotassium mercury iodide.

No description available.

This thesis covers how global mercury emissions are effecting the Great Lakes region, specifically focusing on Minnesota. Minnesota is sensitive to mercury due to its abundant waters and love of fishing. Establishing state regulation and diversifying the State's economy only addresses a small percentage of emitted mercury prominent in Minnesota. Therefore, Minnesota must look to and promote out of State regulation to significantly decrease mercury exposure.

Mercury concentrations in freshwater and marine biota are an ongoing concern, even in areas remote from local point sources, such as in the Canadian Arctic and sub-Arctic. Anadromous Arctic charr, which feed in the marine environment, have lower mercury concentrations than non-anadromous Arctic charr, which feed strictly in freshwater, but the two life-history forms have rarely been studied together, and the mechanisms driving the difference are unclear. Here, data from nine pairs of closely-located anadromous and non-anadromous Arctic charr populations were used to explore the impact of biological and life-history factors on individual total mercury concentration ([THg]) across a range of latitudes (49 – 81° N) in eastern Canada. From six of these sampling locations, additional samples of lower trophic level biota (i.e., algae, invertebrates, and forage fishes) were obtained in order to investigate patterns of total mercury (THg) and methylmercury (MeHg) biomagnification in the marine and lacustrine foodwebs supporting Arctic charr. Arctic charr mean [THg] ranged from 20 to 114 ng/g wet weight (ww) in anadromous populations, and was significantly higher in non-anadromous populations (all p < 0.01), ranging from 111 to 227 ng/g ww. Within-population variations in Arctic charr [THg] were best explained by fish age, and were also positively related to fork-length and δ15N-inferred trophic level. Across all sampling sites, the relationship between Arctic charr [THg] and fish age was significant and statistically similar in both life-history types, but only the non-anadromous fish demonstrated a significant relationship with trophic level. Fork-length and site latitude did not explain significant additional variation in Arctic charr [THg] across sampling locations. Trophic magnification factors were 1.98 – 5.19 for THg and 3.02 – 6.69 for MeHg in lacustrine foodwebs, and 1.59 – 2.82 for THg and 2.72 – 5.70 for MeHg in marine foodwebs, and did not differ significantly between the two feeding habitats for either THg or MeHg. The biomagnification rate of MeHg exceeded that of THg in both habitats. Mercury concentrations at the base of the foodweb were higher in the lacustrine environment (estimated at 17 – 139 ng/g dw for THg and 5 – 42 ng/g dw for MeHg) than in the marine environment (8 – 39 ng/g dw for THg and 1 – 11 ng/g dw for MeHg). The proportion of mercury in the methylated form was related to trophic level, and the relationship was statistically similar in the lacustrine and marine habitats. There was no effect of site latitude on mercury concentrations in marine or lacustrine biota, thus the difference between feeding habitats was consistent across a range of latitudes (56 – 72°N) in eastern Canada. We conclude that a difference in prey mercury concentration, driven by differential mercury concentrations at of the base of the lacustrine and marine foodwebs, is important for explaining the difference in mercury concentration between anadromous and non-anadromous in Arctic charr.

This study used LA-ICP-MS on a documented sample of modern teeth to sample from a continuous line across the cementum increments thus creating a temporal line graph of the elemental composition against distance. The knowledge of cementum was extended through (1) a more complete elemental composition analysis and (2) the relation of element distribution to the ultrastructure structure throughout the life of a tooth. This study was exploratory and demonstrated that lead, zinc, mercury, and barium follow the same general line of changes, and most likely represent changes in health and exposure to these metals in the general environment. Copper, manganese and vanadium varied very little. Technological limitations prevented the examination of element levels in any one annulation.

Mercury (Hg) is a known neurotoxin that is often found in concentrations exceeding safe consumption guidelines in aquatic biota. This is evident in northern Canada, where northerners consume significant amounts of animals such as beluga, seals and burbot. In the Mackenzie River Basin, recent increases in Hg concentration in many of these animals over the past 25 years have been observed. The warming climate, and with it, the changing carbon cycle, are hypothesised in this thesis to play a role in the increases. Within the context of the two major zones (mountainous and peatland), with distinct geomorphology, hydrology and geology, traditional fossil fuel exploration methods (Rock-Eval pyrolysis, organic petrography) have been employed in a novel manner on recent sediments to qualify and quantify the OM and several geochemical analyses have been used to determine the geochemical sources of Hg. The mountainous zone is composed mostly of refractory OM, from forest fire char and heavily reworked OM. It also contains, and fluxes, most of the Hg, which derives from oxidative weathering and erosion of widespread sulfide minerals. However, Hg from this zone is in chemical forms of limited bioavailability. The peatland zone has a greater proportion of labile OM, with higher concentrations of DOC and algal-derived OM. Lake-fed tributaries in this zone contain even higher proportions of labile OM. At one of these sites, the sediment core record shows that Hg has been increasingly associated with labile OM over time, due to increasing primary productivity accelerated by climate change, and is resulting in an increase in scavenged Hg. The temporal trend in algal-bound Hg in the sediment record matches very well with the temporal trend of Hg in burbot sampled from the area, providing one of the first and strongest lines of evidence for the climatic impact on Hg bioaccumulation in Arctic ecosystems.

Hyperthermophilic proteins are of great interest in both the academic and industrial world in understanding how these proteins are capable of retaining their biological activity under such harsh environmental conditions. This thesis studies a tetrabrachion stalk domain from Staphylothermus marinus, know as Right Handed Coiled Coil (RHCC). This protein is of interest due to its extreme thermostability and its affinity for heavy metals. We aim to better understand the reason for the extreme thermal stability of the protein and to take advantage of the proteins affinity for heavy metals with a view to developing a novel approach to bioremediate Hg2+, a major environmental pollutant. Our results clearly indicated that the protein is more thermostable in alkaline conditions in comparison to acidic conditions. This observation can be explained by careful inspection of the high resolution structure. Our data also clearly show that RHCC is able to bind ionic mercury compounds such as mercury nitrate and dipotassium mercury iodide.

The work presented in this thesis first characterises a high speed channel flow cell and then applies the system to the electro-reduction of nitromethane in aqueous solution. Potential step transient measurements are carried out with the current-time transients simulated using a model based on the absence of axial diffusion. The excellent agreement between theory and experiment confirms the proposed mass transport model and further demonstrates that the combination of current-time transients recorded using the high speed channel flow cell and numerical simulations provide a powerful tool to access homogeneous rate constants of the order 1 x 10⁶s̄¹. The high speed channel flow cell is then used in combination with a range of complementary electrochemical techniques, numerical modelling, in-situ ESR, single crystal experiments and kinetic isotope measurements to infer a mechanistic scheme for the complex electro-reduction pathway of nitromethane in aqueous solution. Platinum, gold, mercury/copper and mercury/gold electrodes are investigated enabling the most conclusive description of the reduction mechanism to date. The reaction pathway is shown to follow an ECEEE type process with the chemical step proceeding at the electrode surface. The heterogeneous rate constant, k_het, describing the chemical step is calculated for each electrode surface. For platinum in the pH range 7.0 - 9.0 this value is 0.3 ± 0.06 cm s̄¹. For mercury/copper it is 0.18 cm s̄¹, for gold/mercury it is 0.06 cm s̄¹ and for Au it is 0.095 cm s̄¹. Consideration of these values shows a surprising independence of the heterogeneous rate constant on the chemical identity of the surface with all of the values being similar to within less than an order of magnitude. The reason for the apparent paradox of the observed surface indifference of the chemical reaction step is explained by a homogeneous H transfer from the carbon to the oxygen of the nitromethane radical anion, formed form the initial electron transfer step, occurring in the layer of solution immediately adjacent to the electrode solution as shown in the scheme below. The resulting species, ^•CH2 N(OH))ˉ then undergoes a rapid irreversible adsorption to the electrode surface and subsequent transformation to the final product the hydroxylamine, CH₃NHOH. It is proposed that if the energy barrier to the adsorption of ^•CH2 N(OH))ˉ is less than that required for the H atom transfer then the reaction rate will be insensitive to the adsorption step and hence the chemical identity of the electrode. This introduces the concept of a whole new electrochemical process: the surface indifferent electrocatalytic reaction.