This work explores the metabolism of mercury in liver and spleen tissue of fish from a methylmercury contaminated wetland. Wild-caught bass, catfish, bowfin and gar were collected. Macrophage centers, which are both reactive and primary germinal centers in various fish tissues, were hypothesized to be the cause of demethylation of methylmercury in fish tissue. Macrophage centers are differentially expressed in fish tissue based on phylogenetic lineage, and are found primarily in the livers of preteleostean fish and in the spleen of teleostean fish. Histology of liver and spleen was examined in both control and wild-caught fish for pathology, size and number of macrophage centers, and for localization of mercury. Total mercury was estimated in the muscle tissue of all fish by direct mercury analysis. Selenium and mercury concentrations were examined in the livers of wild-caught fish by liquid introduction inductively coupled plasma mass spectrometry (ICP-MS). Total mercury was localized in histologic sections by laser ablation ICP-MS (LA-ICP-MS). Mercury speciation was determined for inorganic and methylmercury in liver and spleen of fish by bas chromatography-cold vapor atomic fluorescence spectroscopy (GC-CVAFS). Macrophage center tissue distribution was found to be consistent with the literature, with a predominance of centers in preteleostean liver and in spleens of teleostean fish. Little evidence histopathology was found in the livers or spleens of fish examined, but differences in morphology of macrophage centers and liver tissue across species are noted. the sole sign of liver pathology noted was increased hepatic hemosiderosis in fish with high proportions of liver inorganic mercury. Inorganic mercury was found to predominate in the livers of all fish but bass. Organic mercury was found to predominate in the spleens of all fish. Mercury was found to accumulate in macrophage centers, but concentrations of mercury in this compartment were found to vary less in relation to total mercury than hepatocyte mercury. No association was found between selenium content and inorganic mercury proportions. Overall, findings from this study to not support a primary role for macrophage centers in the demethylation of methylmercury in fish tissues.

In an previous 72-hr mercury bioassay with the larval caddisfly Nectopsyche albida, electrophoretically detectable esterase activity was absent in exposed individuals that succumbed to mercury toxicity, while nine other enzymes remained active hours after death. Esterase activity also persisted in unexposed individuals (Benton and Guttman, 1992a.b). To test the effects of mercury exposure duration on esterase activity, additional larval N. albida were exposed under conditions identical to those in the earlier bioassay, and esterase activity in live individuals was tested electrophoretically every 12 hr. To test the effects of mercury concentration on esterase activity, unexposed N. albida larvae were electrophoresed, and the esterase-specific stain was spiked with various concentrations of mercury. Electrophoretic banding patterns were then densitometrically quantified to identity changes in esterase activity with exposure duration and mercury concentration. Results suggest that: inorganic mercury inhibited esterase activity in N. albida, inhibition increased with exposure duration, and inhibition increased with mercury concentration.

A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science. Johannesburg, November 2014. / Unable to load abstract.

Forests provide a multitude of ecological services and are one of Canada’s most important natural resources that support a profitable industry, especially in New Brunswick. The activities associated with harvesting and forest management have documented ecological impacts such as the increased mobilization of mercury from the land to adjacent streams. Methylated mercury bioaccumulates and biomagnifies (concentrates) through food webs and in headwater streams forestry has been shown to change its accumulation. However, not much is known about the spatial trends of mercury accumulation and biomagnification through stream food webs and how different forest management practices affect these trends. To delineate these patterns, food webs were sampled across a spatial gradient from three basins experiencing different levels of forest management intensity. At a basin scale, methylmercury concentrations were greatest in filtered water, food sources, and one invertebrate taxa in a harvested but less intensively managed basin, likely due to increased inorganic sediments and dissolved organic carbon also observed. Biomagnification was lower in this same basin, possibly from inefficient trophic transfer of methylmercury from food sources. Longitudinally this basin also showed differences in fine particulate organic matter (FPOM) and coarse particulate organic matter (CPOM) mercury compared to the other basins, likely due to similar spatial patterns in organic matter. In conclusion, mercury dynamics in stream food webs were impacted by forestry primarily in water and basal food sources at a basin scale, but spatial patterns were inconsistent. / Thesis / Master of Biological Science (MBioSci) / Forest harvesting is an essential and large part of Canada’s economy, and it is important to ensure that its impacts on freshwater systems are minimal. Forest management can increase the amount of the toxic metal mercury entering streams and this can have harmful effects in top predators, like fish, since mercury concentrates through food webs. The knowledge lacking is how different harvesting practices change the amount of mercury in these food webs and whether impacts increase as streams get larger. Of the three basins I studied, the one with harvesting but little assisted regeneration (moderately impacted) had the highest mercury levels in water, leaves, and algae. From upstream to downstream the leaves and biofilm from the moderately impacted basin accumulated less mercury compared to the least harvested basin. Additionally, mercury concentrated less through the food web of this basin. The changes in the moderately impacted basin may be caused by sediments and other materials that transport mercury into the stream and increase water and food levels, but this high mercury was not being transferred to the other organisms in the food web. In conclusion, forest management had some effects on mercury at the base of food webs at a large scale, but patterns through space were inconsistent.

The research described in this Thesis investigates the coordination chemistry of pentafluorooxotellurate(VI) (F5TeO– or “teflate”) and [PnF6]– (Pn = As, F) derivatives of mercury(II), and expands the chemistry of Ng(II) (Ng = Kr, Xe) by characterizing several NgF2 coordination complexes with mercury, and the synthesis of a new xenon(II) oxide cation. The compounds discussed herein were characterized predominately by low-temperature single-crystal X-ray diffraction and Raman spectroscopy, and were frequently complemented by quantum-chemical calculations. The chemistry of the F5TeO–group was developed for Hg(II) derivatives by investigating the Lewis acid properties of Hg(OTeF5)2. Initial efforts investigated interactions with the nitrogen base NSF3, and resulted in the coordination complexes [Hg(OTeF5)2∙N≡SF3]∞, [Hg(OTeF5)2∙2N≡SF3]2, and Hg3(OTeF5)6∙4N≡SF3 at 0oC. Although the F5TeO–group often bonds in a monodendate fashion, these less sterically saturated salts result in oxygen bridging in the solid state. In Hg3(OTeF5)6∙4N≡SF3, oxygen bridging between three metal centers by the pentafluorooxotellurate(VI) group is observed for the first time. The nature of this new bonding was further analysed computationally for Hg3(OTeF5)6∙4N≡SF3 by natural bond orbital analyses (NBO). At room temperature, reactions of Hg(OTeF5)2 with NSF3 resulted in O/F metatheses to yield related F2OSN–derivatives, namely [Hg(OTeF5)(N=SOF2)∙N≡SF3]∞ and [Hg3(OTeF5)5(N=SOF2)-∙2N≡SF3]2, accompanied by the elimination of TeF6 as confirmed by 19F NMR spectroscopy. In related work, the acceptor properties of Hg(OTeF5)2 were further investigated in its reactions with M[OTeF5] (M = [N(CH3)4]+, [N(CH2CH3)4]+, Cs+) to form a series of teflate anion salts; [N(CH2CH3)4]2[Hg(OTeF5)4], [N(CH3)4]3[Hg(OTeF5)5], [N(CH2CH3)4]3[Hg(OTeF5)5], [N(CH3)4]2[Hg2(OTeF5)6], Cs2[Hg(OTeF5)4]•Hg(OTeF5)2, and {Cs3[Hg2(OTeF5)7]•Hg(OTeF5)2}•4SO2ClF. In comparison to their halide counterparts, the less basic and more sterically demanding teflate ligands of the Hg(II) anions show less tendency to extensively bridge. The Raman spectra of the [Hg(OTeF5)4]2−, [Hg(OTeF5)5]3−, and [Hg2(OTeF5)6]2− anions were fully assigned with the aid of their calculated gas-phase vibrational frequencies. NBO analyses further probed the bonding in the anions. The [Hg(OTeF5)5]3− anion provides an unusual square-pyramidal coordination sphere around mercury and the only presently known teflate-substituted anion with a net charge of 3–. In related work, the weakly coordination anion (WCA) [Sb(OTeF5)6]– was substituted in Hg2+ salts using weakly coordinating SO2ClF solvent to give the homoleptic solvent complex, [Hg(SO2ClF)6][Sb(OTeF5)6]2. The ability of this salt to function as a precursor for other ligands was demonstrated by the reaction with the nitrogen bases NCR (R = –CH3 or –CH2CH3) which resulted in the isolation and full characterization of the corresponding homoleptic nitrile complexes [Hg(NCR)5][Sb(OTeF5)6]2ꞏ2SO2ClF. Gas-phase energy-minimized calculation of the cations aided in the vibrational assignment of the Raman spectra, whereas NBO and counterpoise corrected binding energies give insights into the strength of the metal-ligand bonds and resulting electronic effects of these interactions. The established Lewis acidity of Hg(OTeF5)2, and known oxidative resistance of the F5TeO–group, were exploited to form rare examples of noble-gas difluoride adducts, Hg(OTeF5)2•1.5NgF2 (Ng = Xe, Kr). The isostructural complexes were fully characterized, and the KrF2 adduct provided only the second crystallographically characterized KrF2 complex and the first example of bridge coordination by KrF2¬. The chemistry of krypton was significantly extended by further exploring the little studied coordination of KrF2 with the salts Hg(PnF6)2 (Pn = As, Sb) and FHg(AsF6), leading to an important series of coordination complexes. The first homoleptic KrF2 coordination complex, [Hg(KrF2)8][AsF6]2•2HF, was thoroughly characterized by single-crystal X-ray diffraction, Raman spectroscopy, and quantum-chemical analyses. It provides the highest KrF2-to-metal ratio that is currently known for a coordination complex. The bonding was extensively analysed by NBO, calculated binding energies, energy decomposition analyses (EDA), and Extended Transition State Natural Orbitals for Chemical Valence (ETS-NOCV) analyses. This computational work suggests that both orbital interactions, which incorporate covalent bonding, and electrostatic contributions are important stabilization factors and that the 8σg (HOMO‒4) orbital and, to a lesser extent, a degenerate 4πu (HOMO) orbital, derived from free KrF2 (D∞h) are involved in adduct formation. This result helps to rationalize the observed M---F–Kr(F) coordination angles observed for most terminally coordinated NgF2 complexes. A series of related complexes with one to five KrF2 molecules per metal center were also characterized by single-crystal X-ray diffraction, namely Hg(KrF2)(HF)(AsF6)2 (1), Hg(KrF2)2(AsF6)2 (2), Hg(KrF2)3(HF)(SbF6)2 (3), [Hg(KrF2)4(HF)2(SbF6)]2[SbF6]2 (4), Hg(KrF2)5(AsF6)2 (5), Hg(KrF2)4(HF)2(AsF6)2•HF (6), FHg(μ3-FKrF)1.5(KrF2)0.5(AsF6) (7), and FHg(μ3-FKrF)0.5(KrF2)1.5(AsF6) (8). These complexes were unambiguously characterized by single-crystal X-ray diffraction which showed that the structures became more extensively linked due to bridging between mercury and the [PnF6]‒ anions as the number of coordinated KrF2 ligands decreased. While compounds (1)-(6) solely contain terminally coordinated KrF2 ligands, compound (7) also contains the second structurally characterized example of KrF2 bridging two metal centers through each of its fluorine atoms. Replacement of [AsF6]‒ by F‒ in compounds (7) and (8) also resulted in the first examples of a new bonding modality of KrF2, where only one of the fluorine atoms bridges two different metal centers. The Raman spectrum of (5) was assigned with the aid of calculated gas-phase vibrational frequencies. Natural bond orbital (NBO) analyses of [Hg(KrF2)5][AsF6]2 are consistent with coordinate covalent ligand-metal interactions. The nature of bonding for the unprecedented KrF2 bonding modality was further probed computationally with EDA and ETS-NOCV analyses and corroborate an MO description where electron density is donated from both the 8σg (HOMO‒4) and a degenerate 4πu (HOMO) molecular orbital of KrF2 to LUMOs involving the 6s and 6p orbitals of each mercury atom. To further expand the chemistry of the noble-gases, the second known xenon(II) oxide, [XeOXe]2+, was synthesized from the reaction of [FXeOXe---FXeF][AsF6] and acetonitrile at low-temperatures in anhydrous HF. The cation was isolated in macroscopic quantities as its well-isolated adduct-dication [CH3CN---XeOXe---NCCH3][AsF6]2 salt and was fully characterized by single-crystal X-ray diffraction and 16/18O isotopic enrichment Raman studies. The [XeOXe]2+ adduct-cation provides an important example of σ-hole bonding by a nitrogen base to a Xe(II) atom. The nature and strength of the Xe–O and Xe–N bonds in the calculated gas-phase [XeOXe]2+ and [CH3CN---XeOXe---NCCH3]2+ cations were extensively explored using a range of quantum-chemical (QC) methods, namely, NBO, atoms in molecules (AIM), electron localization function (ELF), and molecular electrostatic potential surface (MEPS) analyses. / Thesis / Doctor of Philosophy (PhD) / The coordination chemistry of pentafluorooxotellurate(VI) (F5TeO– or “teflate”) derivatives, as well as [PnF6]– (Pn = As, Sb) salts, of mercury(II), and the chemistry of Ng(II) (Ng = Kr, Xe), are the major focuses of this Thesis. The Lewis acid properties of Hg(OTeF5)2 were investigated using the nitrogen base, NSF3, and M[OTeF5] salts (M = Cs+, N(CH3)4+, N(CH2CH3)4+) which resulted in a series of NSF3 adducts, F2S(O)N– derivatives, and several anions. Reactions of Hg(OTeF5)2 with NgF2 also provided rare examples of bridging NgF2 coordination complexes. Routes to [Sb(OTeF5)6]– salts containing weakly-solvated Hg2+ cations was developed, which provided an important synthetic precursor to explore further ligand substitution reactions at Hg2+. The relatively unexplored chemistry of krypton was further advanced by synthesizing a series of coordination complexes of KrF2 with Hg(PnF6)2 and FHg(AsF6) salts, providing rare examples of terminally coordinated and bridging KrF2 ligands, and a new coordination mode for KrF2 molecules. Advances in the chemistry of Xe(II) were also made through the synthesis and characterization of the second known, and simplest, xenon(II) oxide species. Characterization methods employed in this Thesis predominantly were single-crystal X-ray diffraction and Raman spectroscopy. Quantum-chemical calculations aided with Raman assignments, and were used to further investigate the nature of chemical bonding in the compounds that had been synthesized. The research described in this Thesis significantly contributes to and extends the chemistry of the pentafluorooxotellurate(VI) ligand, to our knowledge and understanding of the reactivity and bonding of krypton(II) and xenon(II) species, and most notably, the coordination chemistry of KrF2.

Mercury levels in the environment have been increasing steadily since the industrial age. Mercury can have deleterious effects on a variety of types of tissue in vertebrates; however, effects of mercury in some animals and/or tissues may be masked by animal's compensatory mechanisms. It is still widely unknown how these rising levels are affecting wildlife, specifically Eastern Bluebirds (Sialia sialis). The goal of this research was to explore a novel method through which mercury may be affecting the fitness of Eastern Bluebirds exposed to varying levels of environmental mercury. Birds on contaminated and reference sites were monitored for two years and various fitness measures were recorded. Four different feather types were also taken to measure mercury's effects on structural coloration. This is the first study to show that mercury in feathers may impact plumage coloration through three possible mechanisms: (1) binding to the sulfide bonds in keratin causing a change in the regular spacing that produces the blue color, (2) inhibition of melanin synthesis, or (3) impacts on the overall health of individuals resulting in lower investment in color production. The overall effects of mercury on bluebirds' fitness and their offspring varied based on adult sex; females with high feather mercury had fewer eggs, and males with high blood mercury fledged fewer offspring. In conclusion, these studies showed a novel way in which mercury may impact birds in an exposed environment as well as ways in which mercury may affect fitness based on sex of the individual and time of exposure. / Master of Science

The problem was to study the behavior of several hydrocarbons when they were subjected to ultraviolet light of 2536 Å in the presence of mercury vapor.

A study of the mercury-sensitized photo-reactions of isobutane.

Final publication is available at http://www.tandfonline.com/doi/full/10.1080/19393210.2014.968808 / 京都大学 / 0048 / 新制・課程博士 / 博士(社会健康医学) / 甲第19637号 / 社医博第70号 / 新制||社医||9(附属図書館) / 32673 / 京都大学大学院医学研究科社会健康医学系専攻 / (主査)教授 木原 正博, 教授 小杉 眞司, 教授 YOUSSEFIAN Shohab / 学位規則第4条第1項該当 / Doctor of Public Health / Kyoto University / DFAM

Mercury is a naturally existing element. It could be transported into human body through food chain, and harm the central nervous system. This is the first study to analyze the concentrations of mercury in different kinds of food in Taiwan. The purpose of the study was to assess the mercury intake of total diet and the health risk. Moreover, the concentration of hair mercury was used to evaluate the body burden. The mercury concentrations in foods were determined by furnace-gold amalgation mercury analyzer. Nine kinds of foods, fish, nonfish seafood, meats, soybean products, eggs, dairy products, vegetables, fruits and cereals were included in the sample. A total of 118 food composites with 574 samples were collected from three largest cities in Taiwan during 2004 to 2006. Dietary information of 446 Taiwanese was collected by using semi-quantitative food frequency questionnaire. Meanwhile, both diet information and hair sample of 355 Taiwanese that were collected. The mean mercury concentrations of nine kinds of food were significantly different (p < 0.05), ranging from 0.5 to 82.9 ng/g wet wt. The mean mercury concentrations was highest in fish, and sequentially decreased in nonfish seafood, eggs, meats, soybean products, vegetables, cereals, dairy products and fruit. All the mean mercury concentrations of foods were below the standard limits of Department of Health in Taiwan, FAO/WHO and European Commission. The dietary mercury intakes for vegetarian, general population lived in the city, fishing village, outlying islands and fishing workers were 0.16, 0.89, 1.22, 1.66 and 3.50 £gg/kg/week, respectively. There were significant differences (p < 0.05) among the five groups mentioned above. The highest mercury intake was found in the fishing workers. However, the mean mercury intakes for those five groups were still within the PTWI safe limit suggested by FAO/WHO, corresponding to 3 to 76% of PTWI. Fishes were the major source of mercury intake among nine kinds of foods for Taiwan population, corresponding to 42 to 77% of mean mercury intake. Mean concentrations of hair mercury of vegetarian, general population lived in the city, fishing village, outlying islands and fishing workers were 0.5¡Ó0.5¡B2.4¡Ó1.8¡B4.4¡Ó3.3¡B4.6¡Ó7.4 and 9.1¡Ó13.6 mg/kg respectively. Significant differences were found among the five groups (p < 0.05). The highest mercury concentration of hair was also found in the fishing workers corresponding to the result of diet intake. 2.3% of Taiwan population with hair mercury higher than the toxic level, 20 mg/kg, proposed by FAO/WHO. They were all fishing workers and outlying islanders. Multiple regression analysis revealed that the concentrations of hair mercury were significantly correlated with the frequency of fish consumption for the population lived in the city, fishing village, and fishing workers. The mercury concentrations of hair was also related with the age of people and the fish species. Aspects of nutrient balance and the health risk, consumption of small and medium-sized fish with mercury lower than 50 ng/g was recommended. No more than 150 g per week was acceptable for the people like to eat large-sized predatory fishes.