This thesis describes the development and improvement of prompt gamma neutron activation analysis and x-ray fluorescence techniques with the goal of reducing the minimum detection limit of cadmium and mercury for non-invasive measurement of occupationally exposed individuals. The detection of cadmium in the liver and kidneys with prompt gamma neutron activation analysis was investigated in this thesis. The cadmium minimum detection limit was determined to be 1.7 mg in the kidney and 3.3 ppm in the liver. This represents a reduction in the minimum detection limit by a factor of 2 in the kidney and 1.4 in the liver, and this improvement was achieved through optimization of a 238Pu-Be-based prompt gamma neutron activation analysis system at McMaster University. This system is now ready for in vivo measurement of cadmium-exposed workers, and possibly for individuals with high levels of environmental exposure. The prompt gamma neutron activation analysis technique was determined to be unsuitable for in vivo mercury measurement in the kidney due to a high detection limit of 315 ppm. This figure was a factor of 23 worse than the detection limit of cadmium in the kidney, when a factor of 10 worse was expected. A comparison was made of mercury and cadmium to chlorine, which is a well-known neutron activation element, and the source of discrepancy was determined to be the enhanced detectability of cadmium due to the non-thermal nature of the 238Pu-Be neutron energy spectrum and the non-l/v behaviour of the cadmium thermal neutron capture cross-section. Since the prompt gamma neutron activation analysis technique was not sensitive enough for mercury detection, a source-based x-ray fluorescence system was developed. This system is based on a 109Cd source that emits 88 keV gamma-rays, a source collimator and planar hyperpure germanium detector in a backscatter (approximately 180°) geometry. Minimum detection limits of 3.9 ppm for a bare kidney phantom and 5.0 ppm for a kidney phantom at 1 cm depth in a torso phantom were obtained. The planar detection system reduced the bare phantom minimum detection limit by a factor of 11 compared to previous source-based x-ray fluorescence studies, however the torso phantom minimum detection limit remains comparable to that of polarized x-ray fluorescence studies. Attempts at improving the mercury minimum detection limit with a cloverleaf detection system (detector consisting of four electronically separate hyperpure germanium crystals) and stronger gamma-ray source were not successful, and currently both the planar and cloverleaf detection systems have a similar minimum detection limit of about 5 ppm at 1 cm kidney depth. In addition, the in vivo measurement of two patients with possible mercury exposure using the cloverleaf x-ray fluorescence system is discussed. / Thesis / Doctor of Philosophy (PhD)

INTRODUÇÃO: Os efeitos deletérios do mercúrio (Hg) no sistema nervoso central, em diferentes formas químicas, têm sido descritos em diversos estudos, entretanto, a ação tóxica sobre a tireoide ainda é pouco compreendida. Experimentos em animais, expostos ao Hg, em diversas formas, mostraram evidências de alterações do parênquima e dos hormônios tireoidianos. A elevada deposição do metal na tireoide e a alta afinidade pelo selênio das desiodases podem ser fatores relevantes para a explicação dos seus efeitos tóxicos. OBJETIVOS: avaliar se a exposição crônica ocupacional ao Hg metálico pode estar associada a alterações da função hormonal tireoidiana, bem como do parênquima da glândula, mesmo depois de cessar a exposição. MÉTODOS: Realizado estudo seccional em 55 expostos ao Hg e 55 controles, do sexo masculino, pareados por idade. Analisadas as concentrações dos hormônios: T3 total e livre (T3T e T3L), T4 livre (T4L) e TSH por eletroquimioluminescência, T3 Reverso (T3R) por cromatografia líquida acoplada à espectrometria de massas em tandem, selênio (no sangue) e Hg na urina (HgU) por espectrofotometria de absorção atômica, iodo urinário por detecção indireta pela Reação de Sandell - Kolthoff, anticorpos anti-tireoperoxidase por ensaio imunoquimioluminométrico. A Ultrassonografia (US) Modo B e Dúplex-doppler da tireoide avaliou as dimensões, ecogenicidade, ecotextura, vascularização e nódulos. Os nódulos com aspecto suspeito de malignidade foram submetidos à punção aspirativa por agulha fina (PAAF) e a análise citológica seguiu a classificação de Bethesda. A análise das variáveis contínuas utilizou os testes t ou U de Mann-Whitney e o Qui-quadrado para associação das variáveis categóricas. A correlação de Spearman utilizada para avaliar a relação entre as variáveis de exposição e as concentrações hormonais. O modelo de regressão logística univariada e múltipla foram empregados para análise do risco. O nível de significância dos testes foi Alfa = 0,05. RESULTADOS: a média de idade dos expostos ao Hg foi 55,2 anos (±6,6 anos) e dos controles 53,4 anos (±6,8 anos). Não houve diferença estatisticamente significativa entre as médias de idade dos grupos (p=0,158). A média das concentrações de Hg urinário, durante o período laboral, foi significativamente mais elevada em expostos (51,9 Microg/L versus 1,79 Micrpg/L; p < 0,01). A média de duração do período laboral foi de 14,5 anos (dp=±7,26). A média das concentrações de TSH foi mais elevada em expostos (3,31 MicroIU/ml versus 2,31MicroIU/ml), com diferença estatisticamente significante entre os grupos (p=0,030). As concentrações de TSH excederam o limite de normalidade (4,20 MicroIU/ml) em 13 indivíduos expostos (27,3%) e em quatro controles (7,3%), com associação estatisticamente significativa entre a elevação de TSH e a exposição ao mercúrio (p =0,018). No modelo de regressão logística, a exposição ao mercúrio mostrou uma razão de chances estatisticamente significativa para elevação das concentrações de TSH (OR=4,86; p=0,038). Não houve diferença estatisticamente significativa da relação T4L:T3L entre os indivíduos expostos e o grupo controle (p=0,791). As médias das concentrações dos hormônios T3, T3L e T4L não apresentaram diferença estatisticamente significativa entre os grupos (p > 0,05). A comparação de médias das concentrações de T3 Reverso mostrou um valor de p próximo do nível de significância do teste (p = 0,06). As proporções de alterações da ecogenicidade foram maiores em expostos (27,3% versus 9,1 %; p=0,026), com associação estatisticamente significativa à exposição ao Hg. Não foi observada associação, estatisticamente significativa, entre a exposição ao Hg e o padrão heterogêneo de ecotextura, ou o aumento de vascularização do parênquima (p > 0,05). A presença de nódulos foi similar entre os grupos. O exame citológico identificou a presença de carcinoma papilífero de tireoide em três indivíduos expostos e um controle. O anatomopatológico confirmou a presença de carcinoma papilífero em quatro indivíduos e identificou o carcinoma folicular em um dos controles. CONCLUSÕES: Os resultados deste estudo mostraram a presença de elevação das concentrações de TSH, e alterações do parênquima tireoidiano, mais frequentes entre os trabalhadores expostos ao Hg, mesmo depois de cessar a atividade laboral, indicando a importância do monitoramento da tireoide / INTRODUCTION: The deleterious effects of mercury (Hg) on the central nervous system, in different chemical forms, have been described in several studies, however, the toxic action on the thyroid is still little understood. Experiments in animals exposed to mercury (Hg), in different states, showed parenchymal and thyroid hormones alterations. The accumulation of metal on thyroid and high affinity for selenium of deiodinases can be a relevant factor for the explanation of his toxic effects. OBJECTIVE: Evaluate the occupational exposure of metallic Hg and its association with the hormones and thyroid parenchyma alterations, even after the labor exposure was discontinued. METHODS: A sectional study in 55 exposed and 55 control males, paired by age was conducted. Serum dosages of total triiodothyronine (T3), free T3 (TT3 and FT3), free T4 (FT4) and TSH were obtained by electrochemical luminescence, the reverse T3 (RT3) by chromatography, selenium (blood), urinary Hg (U-Hg) by atomic absorption spectrophotometry, anti-thyroid peroxidase antibody by immunochemiluminometric assay, urinary iodine by Sandell-Kolthoff reaction. The thyroid parenchyma was evaluated by B-mode ultrasonography with Doppler. The nodules with suspicious aspect of malignancy were submitted to aspiration puncture with a thin needle. The t-test, or Mann-Whitney, chi-square and Spearman correlation were performed. For the risk analysis a univariate and multivariate logistic regression model was used (Alfa = 0.05). RESULTS: The mean age of the exposed to Hg was 55.2 years (SD± 6.6 years) and controls was 53.4 years (SD± 6.8 years). The U-Hg average was significantly higher in exposed (51.9 Microg/L versus 1.79 Microg/L; p=0.000). The longer work duration was 14.5 years (SD ±7.26 years). TSH concentrations exceeded the normality limit (4.20 MicroIU/ml) in 13 exposed individuals (27.3%) and four controls (7.3%), with a statistical significant association between the increase in serum TSH and exposure to mercury (p = 0.018). In the logistic regression model, the exposure to mercury (yes or no) showed a predictive value to the increase of TSH concentrations (OR=4.86; p=0.038). There was no statistical significant difference in the T4L:T3L ratio between the exposed individuals and the control group (p=0.791). The mean concentrations of the hormones T3, T3L and T4L showed no statistically significant difference between the groups (p > 0.05). The comparison of means of the Reverse T3 concentrations showed a p value borderline (p = 0.06). The proportions of the echogenicity alterations were higher at the exposed group (27.3% versus 9.1 %; p=0.026). There was no statistical significant association between the exposure to Hg and the thyroid echotexture pattern or parenchyma increased vascularization (p > 0.05). It was observed a papillary carcinoma in three exposed and one control individual and a follicular in one control. CONCLUSIONS: The results of this study showed the higher serum TSH concentration and prevalence of parenchyma alteration in the Hg exposed group, after cessation of exposure, and indicate the importance of the thyroid monitoring

O Reservatório Rio Grande, localizado na Região Metropolitana de São Paulo (RMSP), é um importante manancial de abastecimento de água dessa região. Foram analisadas amostras de água de fundo e de sedimentos coletadas nesse reservatório em 4 pontos, em 4 campanhas, de setembro de 2008 a janeiro de 2010, sendo estas quantificadas em relação à concentração de Hg total pela técnica de CV AAS. Em seguida, adaptou-se uma metodologia da literatura para quantificação de Hg orgânico em sedimentos, que consistiu na extração dos compostos organomercuriais com diclorometano em meio ácido e, posterior destruição dos compostos orgânicos com cloreto de bromo. A validação dessa metodologia, em termos de precisão e exatidão, foi realizada por meio da análise dos materiais de referência BCR CRM 580 e IAEA 405. Para avaliação dos mecanismos de metilação e desmetilação de Hg nesse ambiente, foram determinados os seguintes parâmetros físicos e químicos, in situ: pH, temperatura da água, potencial redox (EH), transparência e profundidade. Nos sedimentos foram determinados também a granulometria, carbono orgânico total, bactérias redutoras de sulfato, N total e P total, além de Co, Cu, Fe e Mn. A seleção destes parâmetros esteve relacionada diretamente a fatores que influenciam o comportamento do MeHg em sedimentos e sua zona de transição. Foram encontradas concentrações para Hg total variando entre 1,0 e 71,0 mg kg- 1 e de Hg orgânico entre <10,0 a 47,2 &mu;g kg-1 e taxas de metilação entre 0,06 e 1,4% em sedimentos, ao longo do reservatório. Discutiram-se também as diferentes condições de metilação e suas influências, ao longo do reservatório. Como estudo suplementar, avaliou-se a concentração de outros metais e elementos traço presentes nos sedimentos, por meio da técnica de ativação neutrônica. Foram quantificados os elementos As, Ba, Br, Co, Cr, Cs, Hf, Fe, Na, Rb, Sb, Sc, Zn e os elementos terras raras Ce, Eu, La, Lu, Nd, Sm, Tb e Yb. Os fatores de enriquecimento calculados em relação aos valores da crosta terrestre utilizando-se Sc como elemento normalizador apresentaram valores acima de 2,0 para os elementos As, Br, Sb, U e Zn. Verificou-se uma forte influência antrópica para alguns dos elementos analisados, principalmente nos pontos localizados na entrada do reservatório, que recebem descarga de efluentes domésticos e industriais dos rios que alimentam o reservatório. / The Rio Grande reservoir is located in the metropolitan area of São Paulo and it is a very important water supply for this region. In the present study bottom waters and sediment samples collected in this reservoir, in four sampling points, in four campaigns, from September 2008 to January 2010, were analyzed. Firstly total Hg was determined in sediment and bottom waters by cold vapor atomic absorption technique (CV AAS). Following, the analytical methodology for organic Hg was adapted from literature, where the organomercurial compounds were extracted with dichloromethane in acid medium and subsequent destruction of organic compounds by bromine chloride. The validation of this methodology, in terms of precision and accuracy, was performed by means of IAEA 405 and BCR-CRM 580 reference materials analyses. For methylation and demethylation processes evaluation in this environment, the following physical and chemical parameters were assessed, in situ: pH, water temperature, redox potential (EH), transparency and depth. For the sediment samples, granulometry, total organic carbon, sulphate-reducing bacteria, total N and P, besides the metals Co, Cu, Fe and Mn were evaluated. The selection of these parameters was related to the factors that influence the behavior of MeHg in the sediments and its transition zone. Total Hg ranging from 1.0 to 71.0 mg kg-1 and organic mercury from <10.0 to 47.2 &mu;g kg-1 in sediments and methylation rates from 0.06 to 1.4% were found, along the reservoir. Different methylation conditions along the reservoir and its influences were also discussed. As supplementary study the concentration of some metals and trace elements in the sediments by neutron activation analysis technique was determined. As, Ba, Br, Co, Cr, Cs, Hf, Fe, Na, Rb, Sb, Sc and Zn and rare earth elements Ce, Eu, La, Lu, Nd, Sm and Yb were determined. The enrichment factor in relation to earth crust values using Sc as normalizer element reached values higher than 2.0 for the elements As, Br, Sb, Th, U and Zn, indicating a strong enrichment. A strong anthropogenic influence was verified for some of the elements analyzed, mainly in the points located in the entrance of the reservoir that receives domestic and industrial effluents from the rivers that reach the reservoir.

O Reservatório Rio Grande, localizado na Região Metropolitana de São Paulo (RMSP), é um importante manancial de abastecimento de água dessa região. Foram analisadas amostras de água de fundo e de sedimentos coletadas nesse reservatório em 4 pontos, em 4 campanhas, de setembro de 2008 a janeiro de 2010, sendo estas quantificadas em relação à concentração de Hg total pela técnica de CV AAS. Em seguida, adaptou-se uma metodologia da literatura para quantificação de Hg orgânico em sedimentos, que consistiu na extração dos compostos organomercuriais com diclorometano em meio ácido e, posterior destruição dos compostos orgânicos com cloreto de bromo. A validação dessa metodologia, em termos de precisão e exatidão, foi realizada por meio da análise dos materiais de referência BCR CRM 580 e IAEA 405. Para avaliação dos mecanismos de metilação e desmetilação de Hg nesse ambiente, foram determinados os seguintes parâmetros físicos e químicos, in situ: pH, temperatura da água, potencial redox (EH), transparência e profundidade. Nos sedimentos foram determinados também a granulometria, carbono orgânico total, bactérias redutoras de sulfato, N total e P total, além de Co, Cu, Fe e Mn. A seleção destes parâmetros esteve relacionada diretamente a fatores que influenciam o comportamento do MeHg em sedimentos e sua zona de transição. Foram encontradas concentrações para Hg total variando entre 1,0 e 71,0 mg kg- 1 e de Hg orgânico entre <10,0 a 47,2 &mu;g kg-1 e taxas de metilação entre 0,06 e 1,4% em sedimentos, ao longo do reservatório. Discutiram-se também as diferentes condições de metilação e suas influências, ao longo do reservatório. Como estudo suplementar, avaliou-se a concentração de outros metais e elementos traço presentes nos sedimentos, por meio da técnica de ativação neutrônica. Foram quantificados os elementos As, Ba, Br, Co, Cr, Cs, Hf, Fe, Na, Rb, Sb, Sc, Zn e os elementos terras raras Ce, Eu, La, Lu, Nd, Sm, Tb e Yb. Os fatores de enriquecimento calculados em relação aos valores da crosta terrestre utilizando-se Sc como elemento normalizador apresentaram valores acima de 2,0 para os elementos As, Br, Sb, U e Zn. Verificou-se uma forte influência antrópica para alguns dos elementos analisados, principalmente nos pontos localizados na entrada do reservatório, que recebem descarga de efluentes domésticos e industriais dos rios que alimentam o reservatório. / The Rio Grande reservoir is located in the metropolitan area of São Paulo and it is a very important water supply for this region. In the present study bottom waters and sediment samples collected in this reservoir, in four sampling points, in four campaigns, from September 2008 to January 2010, were analyzed. Firstly total Hg was determined in sediment and bottom waters by cold vapor atomic absorption technique (CV AAS). Following, the analytical methodology for organic Hg was adapted from literature, where the organomercurial compounds were extracted with dichloromethane in acid medium and subsequent destruction of organic compounds by bromine chloride. The validation of this methodology, in terms of precision and accuracy, was performed by means of IAEA 405 and BCR-CRM 580 reference materials analyses. For methylation and demethylation processes evaluation in this environment, the following physical and chemical parameters were assessed, in situ: pH, water temperature, redox potential (EH), transparency and depth. For the sediment samples, granulometry, total organic carbon, sulphate-reducing bacteria, total N and P, besides the metals Co, Cu, Fe and Mn were evaluated. The selection of these parameters was related to the factors that influence the behavior of MeHg in the sediments and its transition zone. Total Hg ranging from 1.0 to 71.0 mg kg-1 and organic mercury from <10.0 to 47.2 &mu;g kg-1 in sediments and methylation rates from 0.06 to 1.4% were found, along the reservoir. Different methylation conditions along the reservoir and its influences were also discussed. As supplementary study the concentration of some metals and trace elements in the sediments by neutron activation analysis technique was determined. As, Ba, Br, Co, Cr, Cs, Hf, Fe, Na, Rb, Sb, Sc and Zn and rare earth elements Ce, Eu, La, Lu, Nd, Sm and Yb were determined. The enrichment factor in relation to earth crust values using Sc as normalizer element reached values higher than 2.0 for the elements As, Br, Sb, Th, U and Zn, indicating a strong enrichment. A strong anthropogenic influence was verified for some of the elements analyzed, mainly in the points located in the entrance of the reservoir that receives domestic and industrial effluents from the rivers that reach the reservoir.

Content removed due to copyright restrictions: Anderson, C., Moreno, F., & Meech, J. (2005). A field demonstration of gold phytoextraction technology. Minerals Engineering, 18(4), 385-392. / Mercury (Hg) is a toxic heavy metal that is concentrated in organisms. Injudicious use of Hg and its compounds have resulted in widespread soil contamination. This study investigates the potential use of plants for the remediation of Hg-contaminated mine wastes. Plants can remove soil Hg via phytoextraction and phytovolatilisation. I investigated both of these strategies by focusing on a methodology for Hg analyses in plants and soils with a view to the determination of volatile Hg emitted from plants. Secondly, I determined the feasibility of Hg phytoextraction and phytovolatilisation from contaminated mine wastes. An accurate method for the analysis of Hg in air, plant and various soil fractions was a key component of this study. I developed a hydride-generation atomic absorption spectroscopy method for total Hg analyses in digest and liquid matrices of the aforementioned samples. Quality assurance was ensured by comparing results with those of an external certified laboratory. The maximum discrepancy was 15 %. To measure plant Hg-volatilisation, a method that captures Hg-vapour in solution for subsequent analyses was developed. Initially this system was used to trap Hg vapours released from the root system of Brassica juncea plants grown in hydroponic solutions. A subsequent study improved the Hg trapping system, allowing the capture of volatile Hg from both roots and shoots. Mercury recoveries from the whole plant system (traps + plant + solutions) averaged 90 % using this experimental apparatus. In most contaminated substrates, plant Hg uptake is insignificant, possibly due to the low bioavailability of Hg. This represents an obstacle for effective remediation using phytoextraction. Geochemical studies were carried out in Hg-contaminated substrates to examine the potential of chemical agents to induce Hg solubility and subsequent plant uptake. These studies utilised Hg-contaminated mine tailings collected from three locations: the Tui base-metal mine, in the North Island of New Zealand, the Gold Mountain mine, in North-Central China and, the Serra Pelada artisanal mine site, in Northern Brazil. The results demonstrated that Hg solubility in all tested substrates is increased in the presence of sulphur-containing chemical ligands. The effectiveness of these ligands was influenced by site-specific geochemistry. Plants species were able to accumulate up to 60 mg/kg of Hg in shoot tissues upon addition of sulphur-containing ligands to Tui and Gold Mountain substrates. The degree of plant-Hg accumulation was shown to be dependant on plant species and on the thioligand-induced soluble Hg fraction. Shoot Hg transport was inhibited for Gold Mountain substrate amended with 1.25g/kg of humic acid. The maximum Hg extraction yield for B. juncea plants growing in Tui field sites averaged 25 g per hectare following application of sodium thiosulphate. Volatilisation of Hg vapour from barren substrates occurred as a result of biotic (microorganisms) and abiotic (chemical and photochemical reduction) processes. The presence of B. juncea plants in substrates enhanced the volatilisation process up to 23 fold. Phytovolatilisation was the dominant pathway responsible for between 75 to 99.5 % of the total Hg removed from substrates. It was concluded that Hg removal from contaminated mine wastes can be accomplished by both thioligand-induced phytoextraction and phytovolatilisation. There are risks of groundwater contamination by Hg species mobilised after application of thioligands to substrates. Estimated Hg (0) emissions from plant-based operations at contaminated sites ranged between 1.5 to 3.6 kg of Hg/ha per year. Due to extensive atmospheric dilution, Hg emissions from small-scale phytoremediation operations would not cause serious harm to the local population or the regional environment. Phytoremediation combined with gold-phytoextraction can help to mitigate Hg-pollution in artisanal mine sites in the developing world.

Over the last decade our understanding of mercury cycling has dramatically changed. Evidence of rapid atmospheric oxidation has been observed in the Arctic, Antarctic, the MBL, coastal environments, saline lakes, and the upper troposphere/lower stratosphere. These results show that, Hg0, can undergo rapid gas-phase oxidation under standard atmospheric conditions. However, the mechanism and importance of this transformation is still unclear. The goal of this work was two-fold: to investigate of the kinetics of potential pathway for the gas phase oxidation of atmospheric mercury and to develop new laser based techniques, which can be employed for both laboratory and field studies of Hg(0) and the products of mercury oxidation. First and foremost, this work determined kinetic rate coefficients for the potentially important mercury reactions. Rate coefficients were determined using a Pulse Laser Photolysis - Laser Induced Fluorescence (PLP-LIF) technique monitoring one or more of the following species, Hg(0), Cl, Br, HgCl, and HgBr. The concentrations of these species were measured by LIF as the reaction occurred and a concentration vs. time profile was generated. From these profiles a rate coefficient for the reaction can be obtained. In the course of this work kinetic rate coefficients for the following mercury reactions were measured. Hg(0) + Cl + M --> HgCl + M Hg(0) + Br + M --> HgBr + M HgBr + M --> Hg(0) + Br + M HgBr + Br --> products HgCl + O2 --> products This work is the first direct measurement of a kinetic rate coefficient for these reactions, and the first work which employed one photon LIF to monitor the HgCl and HgBr products. The second aspect of this work was the development of new laser based techniques to detect atmospheric mercury and its oxidation products for both laboratory and field application. In this work a LIF technique was develop to detect HgCl and HgBr. In addition, a two photon LIF technique initially developed by Bauer et al., 2002 was verified and expanded. The two photon LIF technique was used to directly monitor Hg(0) atoms in-situ, to monitor Hg(0) evolving form a gold tube, and to monitor the Hg(0) evolving from the thermal decomposition of reactive gaseous mercury collected on a KCl coated or uncoated denuder. This work represents a significant advance in the development of a viable method the detect mercury and the mercury oxidation products in the laboratory and in the field and is the first study to observe clear differences in the characteristic desorption profiles of HgO and HgX2. This work has broad implications, it enhanced our current knowledge concerning the biogeochemical cycling of mercury, broadened our understanding of the mercury chemistry in high halogen environment, and provided new techniques which can be applied in future field and laboratory studies.

The objectives of this study were to investigate the difference and interaction of mercury (Hg) and selenium (Se) among fish species and tissues. In addition, by comparing with the detected concentrations in other regions, it would be possible to evaluate the pollution status. In the meanwhile, this study analyzed the edibility of the fish, the interaction between Hg and Se as well as their impacts on fish growth. Ten species of fish, including tenpounder (Elops machnata), fourlined terapon (Pelates quadrilineatus), whipfin silverbiddy (Gerres filamentosus), common ponyfish (Leiognathus equulus), Hamilton's thryssa (Thryssa hamiltonii), tilapia (Orechromis niloticus), western Pacific gizzard shad (Nematalosa come), large-scaled mullet (Liza macrolepis), flathead mullet (Mugil cephalus) and milkfish (Chanos chanos), and 20 sediment samples were collected from September to October of 2003 at the reservoir adjacent to a chlor-alkali plant, which had been abandoned for 22 years in Tainan City. Total mercury (THg) and organic mercury (OHg) concentrations were determined in fish muscles, livers, kidneys, gonads, gills and sediment samples. Besides, Se concentrations were also analyzed in fish muscles and livers. Concentrations (mg/kg dry wt.) of THg and OHg in sediment were 43.2¡Ó23.4(mean¡Ósd) and 0.013¡Ó0.008, respectively. THg, OHg and Se concentrations (mg/kg wet wt.) in fish muscles were 0.432¡Ó0.360, 0.305¡Ó0.206 and 0.126¡Ó0.030, similar to the concentrations in other chlor-alkali polluted regions. With the diet habit of Taiwanese, the Hg concentrations of muscles in the seven fish species exceeded the limit of Hg which was allowed to be consumed by humans. THg and OHg concentrations in the fish muscles showed significant species difference. Obviously, the concentrations in carnivorous fishes were higher than those in omnivorous and herbivorous fishes. The OHg concentrations of fish livers and kidneys were highest in carnivorous fishes, but the THg concentrations were higher in omnivorous fishes than in that of carnivorous and herbivorous fishes. Besides, Se concentrations in fish muscles and livers also showed significant species difference, but did not show relation with the feeding habit of fishes. The Hg levels among fish tissues were highest in livers or kidneys, followed by gonads and muscles, lowest in gills. Generally speaking, Se levels were higher in livers than in muscles. The liver THg concentrations of tilapia reached 10 mg/kg wet wt. Their muscle THg concentrations decreased suddenly and maintained at a level about 0.4 mg/kg wet wt. Meanwhile, the liver inorganic Hg and Se concentrations increased with fish weight, while the liver OHg concentrations did not show such a trend but stay at a low level. High Hg concentrations in the fish tissues resulted in adverse effects on fish health. High Hg concentrations in muscles and livers caused heptasomatic index to decrease in western Pacific gizzard shad and milkfish, and condition factor declined in tilipia. Moreover, gonasomatic index remained low while the Hg concentrations of muscles, livers and gonads reached a threshold, which suggested that the growth of those fishes was likely inhibited in Hg polluted environment.

Tampa (US), Guyana (SA), and Bolivia (SA), are geographically, socially, economically, and politically unique which make them ideal sites to study issues of mercury and sustainability. Mercury’s innate ability to bioaccumulate and biomagnify in aquatic and terrestrial ecosystems poses a severe threat to both human and environmental health. The most vulnerable populations affected by mercury consumption include coastal communities, children, women of child-bearing age, the indigenous poor and persons with high environmental/occupational exposure factors. Communities in the regions of Florida, Bolivia, and Guyana whose diets are high in fish and are environmentally/occupationally exposed to mercury may be at a higher risk of mercury intoxication, especially in the absence of education on the topic. Mercury loadings in rivers, streams, and mine tailing waters and sediments ranged from 0.9-114 ng/L and 29- 2891 ng/g, respectively; whilst fish mercury loadings were 0.02-1.034 mg/kg wet wt. Although mining sites had the highest mercury sediment and water loadings there were no significant differences when compared to pristine sites in Guyana. Fish loadings above recommended EPA/WHO regulatory limits were observed at all sites and none had signage, informational warnings or educational material available. A pilot study that included four elementary schools in Tampa showed that Water Awareness Research Education (WARE), a community based participatory environmental educational program, is a sustainable solution to addressing issues of mercury exposure.

The threat of environmental mercury (Hg), particularly methylmercury (MeHg), exposure to the health of humans has been well documented. Thus, it is important to monitor exposure and body burden for public health protection. The first objective of this thesis was to characterize the risk of Hg exposure in two Canadian coastal communities: Grand Marian (n = 91) and St. Andrews/St. Stephen (n = 52), New Brunswick, Canada, using dietary questionnaires and hair analysis. Average Hg intakes and body burden were below the most conservative guidelines. We attributed these results to the low Hg concentrations found in the species commonly consumed: haddock, canned tuna, lobster and pollock (all below 0.2 mg/kg). The analytical method employed to determine Hg in hair, cold vapor atomic absorption (CV-AAS), required a bundle of 100-150 hair strands and involved lengthy chemical digestion procedures which reduce throughput. Direct solid introduction techniques minimize these weaknesses. Our second and third objectives were to evaluate two such methods: (1) combustion, gold amalgamation, atomic absorption spectrometry (C-GA-AAS) and (2) laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) for measuring total Hg in single hair strands. Hair samples with a wide range of Hg exposure were obtained from communities. A 1:1 relationship was observed between C-GA-AAS and the established CV-AAS for analysis of 1-cm hair segments. Additionally, the average relative standard deviation (RSD) of Hg between hair strands within an individual was 6.5 +/- 2.8%, thus justifying the use of a single hair strand for biomonitoring. With a limit of quantification of 0.10 ng of total Hg, a single hair strand with average weight of 0.5 mg and Hg concentrations of 0.2 mg/kg can be measured routinely. Using LA-ICP-MS, we showed that a single laser shot can sample hair material within 50 mum along a single hair strand which is equivalent to less than one day of

Made available in DSpace on 2014-10-09T12:44:17Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:07:54Z (GMT). No. of bitstreams: 1 06788.pdf: 5327793 bytes, checksum: 690e292c11211a103e9ba15155035e6d (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP