The interactions of sulfate-reducing bacteria and Spartina alterniflora marsh grass have been established using a simulated salt marsh system and these interactions have been quantified using geochemical and molecular tools. Plant activities have a direct influence on mercury methylators and therefore control mercury transformation in the environment. Biogeochemical data show that sulfate and sulfide profiles change seasonally due to plant growth and senescence. Spartina alterniflora impact the two drivers for sulfate and sulfide transformation. The community of sulfate-reducing bacteria serve as the anaerobic driver and transform sulfate to sulfide (sulfate reduction). Sulfate-reducing bacteria have been identified as the principal methylators of mercury (Andersson, et al., 1990; Compeau and Bartha, 1985; Compeau and Bartha, 1984; Blum and Bartha, 1980; Gilmour and Capone). The aerobic driver is dissolved oxygen present in both porewater and plant root exudates, which transform sulfide back to sulfate (sulfide oxidation). Sulfate is not limiting in the vegetated sediment, even at the lower depths. Therefore, although sulfate reduction rates were high when plant activity was high, oxidative processes were also significant in the upper 4-cm of the sediment. In addition, demethylation of methylmercury to ionic Hg(II) in the porewater can occur through oxidative processes (Oremland et al., 1991). Therefore, the significance of sulfide oxidation may have strong implications for methylmercury demethylation in our marsh system.

Ninty three yellowfin tuna, Thunnus albacares, the fork length ranged from 80 to 168 cm were collected from the waters around Seychelles by two longline fishing vessels from April to December in 2006. The muscle and liver samples were analyzed for total mercury (THg) and organic mercury (OHg) concentrations.The concentrations of THg and OHg of the muscle were similar to previous studies. The concentrations of THg and OHg form the muscles and livers were positive-linearly regressed with the fish of Fork Length larger than 113 cm (big fish group), but only THg concentration of muscle was negative- linearly regressed 80- 112 cm (small fish group). Such patterns were first found in yellowfin tuna. It might be related to the ¡§growth rate¡¨ . Only one THg concentration of liver were over the standard set by the European Commission Decision (1 mg / kg THg wet wt.), other samples were in accordance with standard set by the European Commission Decision and the US-FDA food safty standard (1 mg / kg MeHg wet wt.). According to the dietary recommendations set by the Department of Health, Executive Yuan, yellowfin tuna can replace 86% animal protein source per week of people.

Treatment of 1-(methylsulfinyl)-2-(phenylethynyl)benzene with 10 mol % of mercury dichloride and 1 equivalent of 2,3-dichloro-5,6-dicyano-1,4-benzoquinone in refluxing benzene gave benzo[b]thiophene in good yields. This method tolerated various functional groups in phenylethynyl moiety, including electron donating groups and electron withdrawing groups. Useing 1-(benzylsulfinyl)-2-(phenylethynyl)benzene as reaction substrate increased the yields of benzo[b]thiophene derivatives. Isotope effect showed that this cyclization reaction belong to Pummerer type cyclization reaction.

Of all the trace elements emitted during coal combustion, mercury is most problematic. Mercury from the atmosphere enters into oceanic and terrestrial waters. Part of the inorganic Hg in water is converted into organic Hg (CH3Hg), which is toxic and bioaccumulates in human and animal tissue. The largest source of human-caused mercury air emissions in the U.S is from combustion coal, a dominant fuel used for power generation. The Hg emitted from plants primarily occurs in two forms: elemental Hg and oxidized Hg (Hg2+). The coal chlorine content and ash composition, gas temperature, residence time and presence of different gases will decide the speciation of Hg into Hg0 and Hg2+. For Wyoming coal the concentrations of mercury and chlorine in coal are 120ppb and 140ppb. In order to understand the basic process of formulation of HgCl2 and Hg0 a numerical model is developed in the current work to simulate in the detail i) heating ii) transient pyrolysis of coal and evolution of mercury and chlorine, iii) gas phase oxidation iv) reaction chemistry of Hg and v) heterogeneous oxidation of carbon during isolated coal particle combustion. The model assumes that mercury and chlorine are released as a part of volatiles in the form of elemental mercury and HCl. Homogenous reaction are implemented for the oxidation of mercury. Heterogeneous Hg reactions are ignored. The model investigates the effect of different parameters on the extent of mercury oxidation; particle size, ambient temperature, volatile matter, blending coal with high chlorine coal and feedlot biomass etc,. Mercury oxidation is increased when the coal is blended with feedlot biomass and high chlorine coal and Hg % conversion to HgCl2 increased from 10% to 90% when 20% FB is blended with coal. The ambient temperature has a negative effect on mercury oxidation, an increase in ambient temperature resulted in a decrease in the mercury oxidation. The percentage of oxidized mercury increases from 9% to 50% when the chlorine concentration is increased from 100ppm to 1000ppm. When the temperature is decreased from 1950 K to 950 K, the percentage of mercury oxidized increased from 3% to 27%.

The objective of this study was to investigate the removal of mercury chloride in flue gas emitted from municipal waste incinerator (MWI) by the adsorption of powdered activated carbon derived from the pyrolysis of waste tires (PAC-T). This study focused on the removal efficiency of mercury chloride and the adsorption capacity of PAC-T. The operation parameters investigated included temperature (30¢J and 150¢J) and powdered activated carbon injection rate (0.1, 0.2 and 0.3 g/hr). Experimental tests were conducted by the following three steps¡G the adsorption column test, the adsorption isotherm simulation, and the removal efficiency test in a pilot plant. The adsorption capacity of PAC-T for various inlet mercury chloride concentrations (55~215£gg/m3) at room temperature (30¢J) were 811~2,188£gg-HgCl2/g-PAC, while the absorption capacity of PAC-T at 150¢J were 214~700£gg-HgCl2/g-PAC which were lower than those at room temperature. It suggested that the adsorption capacity of PAC-T decreased as adsorption temperature increased. Furthermore, the adsorption of mercury chloride by PAC-T was an unfavorable adsorption isotherm. The adsorption column tests were performed to assess the rate of mercury chloride uptake by PAC-T at 30 and 150¢J. Results from the adsorption isotherm simulation indicated that mercury chloride at room temperature (30¢J) can be simulated by the Redlich and Peterson isotherm. However, the adsorption of mercury chloride at 150¢J can be simulated by the Langmuir isotherm. Experimental results from the pilot tests indicated that the removal efficiency of mercury chloride increased gradually with retention time and then leveled off as retention time was higher than thirty minutes. Moreover, the removal efficiency of mercury chloride increased dramatically as PAC-T injection rate increased from 0.1 to 0.3 g/hr. The highest removal efficiency of mercury chloride which can be achieved by waste-tire derived powdered activated carbon (PAC-T) and commercial powdered activated carbon (PAC-C) were 86.5% and 98.9%, respectively. In general, PAC-T was comparative to PAC-C for the removal of mercury chloride from flue gas on the basis of both physical and chemical properties and removal efficiency of mercury chloride.

Abstract The effect of mercury (Hg2+), a known nephrotoxicant, on intracellular free Ca2+ levels ([Ca2+]i) in Madin Darby canine kidney (MDCK) cells was explored. [Ca2+]i was measured by using the Ca2+-sensitive dye fura-2. Hg2+ increased [Ca2+]i in a concentration-dependent manner with an EC50 of 6 mM. The Ca2+ signal comprised a gradual increase. Removal of extracellular Ca2+ decreased the Hg2+-induced [Ca2+]i increase by 67%, suggesting that the Ca2+ signal was due to both extracellular Ca2+ influx and store Ca2+ release. In Ca2+-free medium, the Hg2+-induced [Ca2+]i increase was nearly abolished by pretreatment with 1 mM thapsigargin (an endoplasmic reticulum Ca2+ pump inhibitor), and conversely, pretreatment with Hg2+ abolished thapsigargin-induced Ca2+ increase. Hg2+-induced Ca2+ release was not altered by inhibition of phospholiase C but was potentiated by activation of protein kinase C. Overnight treatment with 1 mM Hg2+ did not alter cell proliferation rate, but 10 mM Hg2+ killed all cells. Collectively, this study shows that Hg2+ induced protein kinase C-regulated [Ca2+]i increases in renal tubular cells via releasing store Ca2+ from the endoplasmic reticulum in a manner independent of phospholipase C activity. Hg2+ also caused cytotoxicity at higher concentrations.

Total mercury (Hg) levels were determined in the tissues of ten taxa of pelagic fishes, with a special emphasis on apex predators (large vertebrates). Highest Hg levels were observed in blue marlin (Makaira nigricans), carcharhinid sharks (Genus Carcharhinus) and little tunny (Euthynnus alletteratus), ranging from 1.08 to 10.52 ppm. Moderate to low concentrations (<1.0 ppm) were observed in blackfin tuna (Thunnus atlanticus), cobia (Rachycentron canadum), dolphinfish (Coryphaena hippurus), greater amberjack (Seriola dumerili), king mackerel (Scomberomorus cavalla), wahoo (Acanthocybium solandri) and yellowfin tuna (Thunnus albacares). For the majority of species examined, Hg level did not vary significantly between locations (Texas and Louisiana) and years (2002 and 2003). The relationship between Hg level and fish size/weight was also explored and six taxa (blackfin tuna, carcharhinid sharks, dolphinfish, king mackerel, wahoo, yellowfin tuna) showed significant positive relationships between Hg level and body size and/or weight. Natural dietary tracers, stable isotopes (15N, 13C) and fatty acids were used to evaluate the relationship between Hg and trophic position and the relationship between Hg and dietary history. Stable nitrogen isotope analysis showed that Hg levels in fish tissues were positively associated with trophic position. Based on the 13C and 15N values of pelagic consumers examined in this study, three natural groups were identified with cluster analysis, and the same groupings were detected based on fatty acid profiles. This not only confirmed the existence of these natural groupings, but also indicated that the distinguishing factors for the grouping was likely connected with the dietary history of these fishes. The classification tree based on the fatty acid profiles of pelagic fishes readily separated fishes from different regions, suggesting that diets of pelagic taxa within the same region are similar or these consumers share a common source of organic matter in their food web. Findings from this study complement other Hg investigations conducted in the Gulf and also furthered our understanding of the link between feeding ecology and Hg accumulation. Moreover, the combined use of stable isotope and fatty acid techniques provided new insights on the dietary history of pelagic fishes in the Gulf of Mexico.

Mercury -contaminated sediments often act as a sink of mercury and produce methyl-mercury, an acute neurotoxin which readily bio accumulates, due to the presence of bacterial communities hosted by the sediment. One common remediation approach to manage methyl-mercury is to amend the sediment by capping or directly mixing with a sorbent. This thesis aims to assess the capabilities of some calcium-based sorbent to act in that capacity. Laboratory experiments were implemented to simulate mercury fate and behavior in geochemical conditions that capping would likely create. Well-mixed slurries showed that gypsum materials were disparate and their behavior was similar from sand to organocaly. Mercury sorption capacities of these gypsums were poor with a sorption coefficient approximately equal to 300 L/kg. Reduction of methylmercury was minimal and even increased in two of the three materials. Therefore, the three gypsums, which tend to be more cohesive when wetted, doesn’t constitute a viable material for sediment capping. / text

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Thesis (MTech. degree in Chemistry)--Tshwane University of Technology, 2010. / Discusses an accurate and sensitive method for the determination of trace levels of mercury in environmental air samples may be established using cost effective technologies.