Recent research has shown that the Arctic may be a sink for mercury, however, the fate of this deposited mercury in the environment is not known. The objective of this project was to determine the factors affecting methyl mercury (MeHg) production in Arctic organic soil on the Truelove Lowlands, Devon Island, Canada. In the field we observed a steady decrease in MeHg over time, with MeHg concentration at many sampling locations declining below detection limits. This decrease did not correlate to any chemical or biophysical parameter measured. During the study the Lowlands appeared to be mildly reducing with dissolved Fe(II) being present in the porewater, however, no correlation was observed between MeHg production and the variables measured. The dissolved organic matter concentration of the porewater was quite high, the pH was circumneutral and it would seem that in the absence of more highly reducing conditions that mercury would be unavailable for methylation.<p> It seems likely under field conditions MeHg was much more bioavailable then inorganic mercury. This would lead to a higher rate of demethylation then methylation and a net decrease in MeHg. Little research has been done on demethylation and the effect of environmental conditions on demethylation, especially in arctic environments. However, it is possible that the rate of demethylation was not affected by changes in temperature or any other parameter measured over the course of the field study. <p> Laboratory microcosm studies using saturated soil from the organic horizons demonstrated little potential for unspiked organic soil to produce significant amounts of MeHg. The spiked treatment, however, had an eight fold increase in MeHg concentration and the sterile treatment showed no change in MeHg concentration over 40 days of freeze (-5 0C) and 59 days of thaw (4 oC). <p> Our data suggests that a combination of atmospheric and in-situ processes maintain a cycle of MeHg production (spring) and loss (summer) in arctic soils. It would seem that Arctic wetland soils are not a significant source of MeHg to the Arctic ecosystem and that snowmelt is the dominant source.

Generation of reactive oxygen species (ROS) is an important view point to evaluate heavy metal toxicity and resistance in plants. Arabidopsis thaliana is a fully sequenced model plant, and the characteristic between ecotypes due to adaptation towards varied environment can be used as a material for comparing physiological differences. In this experiments, two ecotypes of A. thaliana: Columbia (Col-0) and Landsberg erecta (Ler-0) is observed for the roots growth inhibition, plasma membrane integrity and lipid peroxidation after treated with different concentration of HgCl2 (0, 2, 4, 8 £gM), in attempt to compare the anti-oxidation defensive mechanism of two ecotypes and understand mercury-induced oxidative stress. ROS and Ca2+ generation is determined with CM-H2DCF-DA and Oregon Green 488 BAPTA-1 is under confocal microscopy. Some anti-oxidant enzymes such as superoxide dismutase (SOD EC 1.15.1.1), peroxidase (POD EC1.11.1.7) and ascorbate peroxidase (APX EC 1.11.1.11) are examined for the activity under protein gel electrophoresis. Experiment results showed that mercury-induced inhibition of root growth is more significant in Ler-0. ROS in roots of both ecotypes shows different trends under 8 £gM HgCl2 , however increment of ROS level below 4 £gM HgCl2 ; Ca2+ shows the similar result as ROS. Activity of SOD isoforms reached a peak at 2-4 £gM HgCl2. Expression of POD is correlated to the mercury concentration in both ecotypes. There are two types of APXs expression, one decreased as mercury concentration increased, another increased under 2 £gM HgCl2 and decreased as the concentration getting higher. According to the observation on expression of ROS generations and anti-oxidation system, we speculated that tolerance of Ler-0 towards mercury is weaker than Col-0. The results can be used as a basis for further discussion on influence of mercury towards different anti-oxidation enzymes and the signaling pathways.

Fish provides important nutrients, including the omega-3 fatty acids (£s-3 PUFAs) but it also contains toxic contaminants, such as mercury (Hg) that may decrease the advantage of fish consumption. Therefore, balancing the nutritional requirements for £s-3 PUFAs and risks associated with mercury is an important issue for fish consumption. The aim of this study is to analyze the fatty acid compositions and mercury concentrations of several common wild and farmed fishes in Taiwan in order to evaluate the potential health benefits and risks of fish consumption. Wild and farmed fish sample were collected between 2010 and 2012 from trawlings, local fish markets, and aquaculture farms in western Taiwan. A total of 32 species of fish were collected. Dorsal muscle was dissected, dried, and homogenized. The proximate composition including crude lipid, crude protein, moisture, ash, and fatty acid composition, as well as mercury concentration in the muscle were analyzed. The fishes that were investigated were lean to medium in fat content. Content of £s-3 PUFAs were higher in the carnivorous fishes (0.96¡Ó0.62 g/100 g flesh weight) than in the herbivorous or omnivorous species (0.86¡Ó0.35 g/100 g flesh weight). The crude lipid contents in the wild fishes (6.7¡Ó3.7%) were lower in crude lipid contents than their farmed counterparts (12.1¡Ó7.5%). Fish £s-3 PUFAs concentrations were significantly increased with crude lipid content (p< 0.05). Mean mercury concentrations of all samples (0.048¡Ó0.038 mg/kg flesh weight) were lower than the common food safety standard (0.5 mg/kg flesh weight). Similar to the £s-3 PUFAs, the mean mercury concentrations were higher in the carnivorous fishes (0.06¡Ó0.04 mg/kg flesh weight) than in the herbivorous and omnivorous fishes (0.02¡Ó0.01 mg/kg flesh weight) and higher in the wild fishes (0.052 mg/kg flesh weight) than farmed fishes (0.031 mg/kg flesh weight). From the results of the present study, we can conclude that: to obtain the health benefits of the omega-3 fatty acids with a safe amount of mercury intake, the consumption of high EPA+DHA species (EPA+DHA concentrations are higher than 2 g/100 g flesh weight), such as croaker twice a week (3 oz/serving), or medium EPA+DHA species (EPA+DHA concentrations are between 1.02 to 1.34 g/100 g flesh weight),like fourfinger threadfin, Belanger¡¦s croaker, blue mackerel, and flathead grey mullet 3-4 times a week are desirable. In the case of consume tilapia or milkfish (EPA+DHA concentrations are between 0.60 to 0.72 g/100 g flesh weight) for cardiovascular disease preventative purposes, daily consumption of the fishes are beneficial. Furthermore, those people who have potential cardiovascular disease should double the amount of fish consumption suggested above. Accordingly, for those in the tropical Asian region, consumption of the amount of fish intake stated in this thesis would not exceed the safe Hg intake limit.

This study investigated the adsorptive capacity and isotherm of HgCl2 onto spherical activated carbons (SAC) via thermogravimetric analysis (TGA). Activated carbon injection (ACI) is thought as the best available control technology (BACT) for mercury removal from flue gas. There are two major forms of vapor-phase mercury, Hgo and Hg2+, of which HgCl2 accounts for 60-95% of total mercury. Mercury emitted from the incineration of municipal solid wastes (MSW) could cause severely adverse effects on human health and ecosystem since it exists mainly in vapor phase due to high vapor pressure. Although the adsorptive capacity of HgCl2 onto activated carbon has been studied in previous adsorption column tests, only a few studies have thoroughly investigated the adsorption isotherms of HgCl2 onto SAC. Equilibrium and kinetic studies are important towards obtaining a better understanding of mercury adsorption. Many investigations have addressed the relationship between sorption kinetics and equilibrium for different adsorbent/adsorbate combinations. For the removal of vapor-phase mercury, several bench-pilot, and full-scale tests have be proceeded to examine the influence of carbon types, carbon structures, carbon surface characteristics, injection methods (dry or wet), amount of carbon injected, and flue gas temperature on mercury removal. In addition, the dynamics of spherical activated carbons (SAC) adsorbers for the uptake of gas-phase mercury was evaluated as a function of temperature, influent concentration of mercury, and empty-bed residence time. However, only a few studies investigated the adsorption isotherms of HgCl2 onto activated carbons. In this study, TGA was applied to obtain the adsorptive capacity of HgCl2 onto SAC with adsorption temperature (30~150oC) and influent HgCl2 concentration (50~1,000£gg/m3). Experimental results indicated that the adsorptive capacity of HgCl2 onto SAC was 0.67and 0.20 mg/gC at 30¡B70 and 150oC, respectively. This study investigated the adsorptive capacity of HgCl2 vapor onto SAC via TGA analysis. Experimental results indicated that the adsorptive capacity of SAC decreased with the increase of the adsorption temperature. Furthermore, the results suggested that that the adsorption of SAC on HgCl2 vapor was favorable equilibrium at 30 and 70¢J and unfavorable equilibrium at 150¢J. In comparison of the experimental data with isotherm equations, Freundlich isotherm fitted the experimental results better than Langmuir isotherm. The model simulations were found to fit very well to the high concentration experimental kinetic data for both adsorption and desorptionusing two adjust parameter, effective diffusivity, and the Freundlich isothermexponent.¡@The extracted model parameter, effective diffusivity and n, were then used to predict the experimental kinetic data for the same combination at other concentrations.

This study investigated the production of powdered activated carbon derived from carbon black of pyrolyzed waste tires, and their adsorptive capacity on vapor-phase mercury chloride (HgCl2) using both adsorption column and thermogravimetric adsorption systems. The adsorption isotherms and kinetic models were further simulated in the study. In addition, an innovative compositive impregnation process was developed to increase the sulfur content of powdered activated carbon derived from waste tires. The activation of carbon black to form powdered activated carbon was performed in a tubular oven. The operating parameters including activation temperatures, activation time, and water feed rates were investigated in this study. Experimental results indicated that the yield of carbon-black derived powdered activated carbon (CBPAC) decreased with the increase of activation temperature, activation time, and water feed rate, while the BET surface area and pore volume decreased. In the comparison of activation time and water feed rate in the activation process, activation time had an important impact on the production of specific surface area than water feed rate. The optimal operating parameters included activation temperature of 900¢J, activation time of 180min, water feed rate of 0.5 mLH2O/gC-sec, and water injection behind activation process of 17.5 min. From the analysis of carbon surface, the carbon contents of powdered carbon black (PCB), CBPAC, commercial powdered activated carbon (CPAC) were 89.5%, 87.6%, and 88%, respectively. The C (1s) peak region of PCB consisted of 49.8% C-C, 38.9% C-O, 10.5% C=O or O-C-O. Similar analysis results showed that the total area of the C (1s) peak region of CBPAC consisted of 57.5% C-C, 26.8% C-O, 8.1% C=O or O-C-O, and 7.6% O-C=O. Similar to CPAC, the C (1s) peak region consisted of 42.6% C-C, 41.8% C-O, and 15.6% O-C=O. Furthermore, the sulfur contents of PCB and CBPAC were both 0.5%. The S (2p) peak region of PCB consisted of 58.9% ZnS (zinc sulfide) and 41.1% S=C=S. For CBPAC, the S (2p) peak region solely contained S=C=S. The comparison of two sulfur impregnation processes revealed that the innovative compositive impregnation process could simultaneously increased the sulfur content and the BET surface area of powdered activated carbon (PAC), however, the direct impregnation process increased the sulfur content while the BET surface area of PAC decreased linearly. Without the disadvantages of time and energy consumption associated with direct impregnation, the compositive impregnation is an efficient and energy-saving process for producing sulfurized PAC with a high BET surface area and high sulfur content. Experimental results obtained from the adsorption column tests indicated that the influence of the adsorption depth on the adsorptive capacity of CBPAC did not vary much, while the adsorptive capacity of CBPAC increased with HgCl2 concentration. Furthermore, the adsorptive capacity of CBPAC on vapor-phase HgCl2 was less than that of CPAC at the adsorption temperatures of 25~150¢J and high humidity of 12.3 wt %. The difference of adsorptive capacity for CBPAC and CPAC correlated closely with BET surface area and sulfur content. Results form the thermogravimetric adsorption analysis indicated that the adsorptive capacity of CBPAC and initial adsorption rate on vapor-phase HgCl2 increased with HgCl2 concentration and decreased with adsorption temperature. In the kinetic modeling, the deviation of experimental and simulated values simulated by the pseudo-first-order model was lower than those of pseudo-second-order models. Furthermore, the r (correlation coefficient) of pseudo-first-order and pseudo-second-order models were 0.9745~0.9977 and 0.9217~0.9780, respectively. It suggested that the pseudo-first-order model could simulate the adsorption of HgCl2 onto CBPAC better than pseudo-second-order model.

The objective of this study was to remove mercury vapor from municipal waste incinerator (MWI) by the adsorption of powder activated carbon (PAC) prepared from the pyrolysis of waste tire. The study focused on the measurement of mercury concentration in flue gas emitted from municipal waste incinerator, the preparation of PAC from the pyrolysis of the waste tire and impregnated with sulfur, and the adsorption capacity of mercury by the self-made PAC. The measurement of heavy metals in flue gas emitted from four typical MWIs was conducted in this study. Experimental results obtained from the measurement of mercury from flue gas indicated that the removal efficiency of mercury ranged from 83.71%~96.22%for the tested MWIs. This study revealed that the injection of PAC in flue gas would enhance the removal efficiency of mercury. Besides, oxided mercury (Hg2+) can be removed much more easily than elemental mercury (Hg0). Experimental results obtained from the pyrolysis of waste tires indicated that the pyrolysis temperature of waste tire was approximately 400~500¢J, and the percentage of carbon residue is 35~37%. With higher temperature and water feed rate and longer activation time, the specific surface area and total pore volume of PAC increased while the average pore radius decreased. The highest specific surface area of PAC obtained in this study was 996 m2/g. In addition, experimental results obtained from sulfur impregnation process indicated that the specific surface area of PAC decreased dramatically as sulfur was added to PAC. Experiment results obtained from the adsorption capacity of HgCl2 on PAC by column test indicated that PAC with higher specific surface area could adsorb more HgCl2 at room temperature (25¢J). The adsorption capacity of sulfur impregnated PAC decreased at 25¢J was due to the decrease of specific surface area of PAC. However, results from the comparison of two PAC with similar specific surface area indicated that the PAC with higher sulfur content had higher adsorption capacity. It suggested that the addition of sulfur to PAC could enhance the adsorption of HgCl2 at 25¢J. Experimental results obtained from column tests at 150¢J showed that the adsorption capacity of PAC increased as sulfur content of PAC increased. These results suggested that the adsorption mechanism of HgCl2 by PAC was mainly physical adsorption at lower temperature and it was chemisorption at higher temperature. Besides, the self-made PAC demonstrated the similar adsorption capacity of HgCl2 with commercial PAC used in MWIs.

none

<p>The construction of a high intensity neutrino source requires multi megawatt beams and challenges the targets in use. MERIT is a proof-of-principle test for a novel kind of neutrino factory target, employing a 24 GeV/c proton beam and a 1 cm in diameter free mercury jet as beam target. This thesis describes the design and implementation of a secondary particle flux production detection system. Employed detectors are polycrystalline diamond detectors and electron multipliers. Simulations of the secondary particle production have been made using FLUKA. The detection system is remotely controlled by a LabView interface and experimental observations from the initial analysis are presented.</p>

Thesis (Ph. D.)--University of Washington, 2000. / Vita. Includes bibliographical references (leaves 126-144).

Thesis (Ph. D.)--University of Missouri-Columbia, 2001. / Typescript. Vita. Includes bibliographical references (leaves 123-128). Also available on the Internet.