Abstract  In the crystal structure of the title two-dimensional network, [HgCl(2)(C(11)H(10)N(2)O)](n), the asymmetric unit consists of HgCl(2) dumbbells and one mol-ecule of the quinazoline unit. Pseudo-octa-hedrally coordinated Hg(II) cations are chloride-bridged via a crystallographic inversion centre leading to different Hg-Cl bonds (short and long) and linked by other Cl atoms via translation along the a axis. The quinazoline ligands connect the Hg-Cl-Hg-Cl chains by N and O atoms along the b axis, forming the two-dimensional network structure. The crystal structure is stabilized by weak non-classical C-H⋯Cl hydrogen bonds and aromatic π-π stacking inter-actions [centroid-centroid distances = 3.942 (4) and 3.621 (4) Å].

Abstract  BIOSIS COPYRIGHT: BIOL ABS. RRM THE IDENTIFICATION OF METAL ALLERGENS IN THE LOCAL LYMPH NODE ASSAYYMEETING ABSTRACT MEETING POSTER MURINE ANIMAL MODEL LOCAL LYMPH NODE ASSAY METHODOLOGY IMMUNE SYSTEM TOXICOLOGY GOLD (III) CHLORIDE METAL CONTACT ALLERGEN BERYLLIUM SULFATE TETRAHYDRATE POTASSIUM DICHROMATE COPPER (II) CHLORIDE MERCURY (II) CHLORIDE AMMONIUM TETRACHLOROPLATINATE COBALT CHLORIDE TIN CHLORIDE ALUMINUM CHLORIDE MANGANESE CHLORIDE NICKEL CHLORIDE LEAD ACETATE ZINC SULFATE SKIN SENSITIZATION ANALYTICAL METHOD

Abstract  The chloro(alkyl)metallocenes [MR*(Cl)(eta-C5H5)(2)][R*=-CH(SiMe3)C6H4Me-o; M=Zr 1 or Hf 2] have been prepared from [MCl2(eta-C5H5)(2)] and LiR*(tmen) (tmen=N,N,N',N'-tetramethylethane-1,2-diamine); further alkylation occurred only for M = Zr, affording rac-3a and meso-3b, [ZrR*(2)(eta-C5H5)(2)]. In contrast, reaction of 2 equivalents of Li[CH(SiMe3)(2)](tmen) with [ZrCl2(eta-C5H5)(2)] yielded an alkyl elimination product possessing mu-eta(1):eta(5)-C5H42- ligands. Compound 1 was reversibly reduced (E-1/2(red)=-1.72 V vs. saturated calomel electrode, SCE) whereas 2, 3a or 3b were irreversibly reduced (E-red=-2.12, -2.08, -2.00 V respectively vs. SCE). Thermolysis of 3b in toluene gave 3a (80 degrees C) or 'Zr(C10H8)' (120 degrees C). Photolysis of 3a or 3b at 20 OC in tetrahydrofuran (thf) yielded a 1 : 1 mixture of 3a and 3b; a d(1) intermediate has been unambiguously identified as [ZrR*(eta-C5H5)(2)]. Reduction of 1 (Na-Hg), or 3a and 3b (Na[C10H8]), in thf also gave [ZrR*(eta-C5H5)(2)] but this slowly transformed into [ZrR*(eta-C5H5)(2)(thf)], and 1 with Na[C10H8] and PPh3 gave [ZrR*(eta-C5H5)(2)(PPh3)]. Reduction of 1, 3a or3b or photolysis of 3a or 3b, in the presence of PMe3 gave [ZrR*(eta-C5H5)(2)(PMe3)]. Crystal structure determinations showed a slightly more crowded metal environment in 2 than in 1, consistent with the view that dialkylation in 2 is limited on steric grounds; M-sigma-C 2.359(4) (1), 2.322(8) (2), metal-centroid 2.22 (1), 2.21 (2), M-Cl 2.444(1) (1), 2.418(3) (2) Angstrom. The structure of 3a confirms the rac assignment, M-sigma-C 2.37(4), Angstrom, metal-centroid 2.23, 2.24 Angstrom.

Abstract  Nanocrystalline metal (Cu, Hg, Zn, Pi, Ph) sulfides with different shapes and different particle sizes have been successfully prepared in a formaldehyde solution of metal salt and thioacetamide by microwave irradiation. Powder X-ray diffraction patterns indicated that the products were pure orthorhombic Bi2S3 phase, cubic phase HgS, hexagonal phase CuS, cubic phase ZnS, cubic phase PbS, respectively. The products were also characterized by transmission electron microscopy. Ultraviolet reflection spectrum clearly indicates the presence of quantum size effects in ZnS. (C) 2001 Elsevier Science B.V. All rights reserved.

Abstract  This paper is to discuss the recent observations of elemental mercury (Hg-0) reemissions from a pilot-scale limestone wet scrubber. Simulated flue gas was generated by burning natural gas in a down-tired furnace and doped with 2000 ppm of sulfur dioxide (SO2). Mercuric chloride (HgCl2) solution was delivered to the scrubber at a controlled rate to simulate the absorption of ionized mercury (Hg2+). Testing results have shown that, after Hg2+ was injected, elevated He concentrations were soon detected both in the scrubber effluent flue gas and the hold tank air, which reflected the occurrence of Hg-0 reemissions in both places. When the HgCl2 feed was stopped, the Hg-0 reemission continued for more than 2 h. In addition, a significant Hg-0 reemission was also detected outside the scrubber loop. In an attempt to understand the Hg-0 reemission increase across the wet scrubber system under transient and steady states and to understand the underlying relationship with the mercury complexes retained in the wet scrubber system, a mercury reemission model was developed. With this model, it was found that the Hg-0 reemission rate under the current testing conditions can be simulated by a first-order reaction, and only a portion of Hg center dot S(IV) complexes retained in the slurry were participating in the reemission reaction.

Abstract  Information on the mechanism of metal ion inhibition of NADPH-cytochrome P450 reductase is limited. The purpose of the present paper was to elucidate in vitro effect of Hg(+2), Cd(+2), Ni(+2), Cr(+3) and Zn(+2) ions on the purified mullet NADPH-cytochrome P450 reductase. NADPH-cytochrome P450 reductase was purified from detergent-solubilized liver microsomes from leaping mullet (Liza saliens). All of the metal ions caused inhibition of the enzyme activity except Zn(+2). At 50 microM metal concentration, Hg(+2) inhibited the cytochrome P450 reductase activity completely (100%), while, at the same concentrations, Cd(+2), Cr(+3) and Ni(+2) caused 66%, 65% and 37% inhibition, respectively. At 50 microM metal concentration, Zn(+2) had no apparent effect on cytochrome P450 reductase activity. The IC(50) values of HgCl(2), CrCl(3), CdCl(2) and NiCl(2) were estimated to be 0.07 microM, 24 microM, 33 microM and 143 microM, respectively. Of the metal ions tested, Hg(+2) exhibited much higher inhibitory effect at lower concentrations, so it was evidently a more potent inhibitor than the others. All four metal ions displayed noncompetitive type of inhibition mechanism for the purified reductase as analyzed by Dixon plot. K(i) values of Hg(+2), Cr(+3), Cd(+2), and Ni(+2) were calculated from Dixon plots as 0.048 microM, 18 microM, 73 microM and 329 microM, respectively.

Abstract  Mercury (Hg) is a highly toxic element, and its contamination of groundwater presents a significant threat to terrestrial ecosystems. Understanding the geochemical processes that mediate mercury transformations in the subsurface is necessary to predict its fate and transport. In this study, we investigated the redox transformation of mercuric Hg (Hg[II]) in the presence of the Fe(II)/Fe(III) mixed valence iron oxide mineral magnetite. Kinetic and spectroscopic experiments were performed to elucidate reaction rates and mechanisms. The experimental data demonstrated that reaction of Hg(II) with magnetite resulted in the loss of Hg(II) and the formation of volatile elemental Hg (Hg[0]). Kinetic experiments showed that Hg(II) reduction occurred within minutes, with reaction rates increasing with increasing magnetite surface area (0.5 to 2 m2/L) and solution pH (4.8 to 6.7), and decreasing with increasing chloride concentration (10(-6) to 10(-2) mol/L). Mössbauer spectroscopic analysis of reacted magnetite samples revealed a decrease in Fe(II) content, corresponding to the oxidation of Fe(II) to Fe(III) in the magnetite structure. X-ray photoelectron spectroscopy detected the presence of Hg(II) on magnetite surfaces, implying that adsorption is involved in the electron transfer process. These results suggest that Hg(II) reaction with solid-phase Fe(II) is a kinetically favorable pathway for Hg(II) reduction in magnetite-hearing environmental systems.

Abstract  Non-toxic, conditioning doses of aluminium chloride were tested for induction of adaptive response to the genotoxic challenge doses of methyl mercuric chloride (MMCl), maleic hydrazide (MH) and ethyl methane sulfonate (EMS). Embryonic shoot cells of Hordeum vulgare and root meristem cells of Allium cepa were employed as the assay systems. Plant tissues fixed at different recovery hours following the challenge treatments with or without prior Al-conditioning were analyzed for cells with genotoxicity markers that include spindle and/or chromosome aberrations and micronuclei (MNC). The results provided evidence that Al(3+) triggered adaptive response that protected the plant cells from the genotoxicity of MMCl and EMS. Al(3+), however, failed to induce adaptive response against the genotoxicity of MH. A comparison of Al-induced adaptive response with that induced by heavy metals: Cd(2+), Cu(2+), Hg(2+), Ni(2+), Pb(2+), Zn(2+) and oxidative agents: hydrogen peroxide (H(2)O(2)) and paraquat (PQ) pointed to the similarity of Al-adaptive response to that of PQ rather than to other heavy metals or H(2)O(2). Al-induced adaptive response demonstrated in the present study to MMCl and EMS possibly involved antioxidant defense and DNA repair systems, respectively.

Abstract  A method based on far infrared-assisted solvent extraction (FIASE) and capillary electrophoresis-amperometric detection (CE-AD) has developed for the rapid determination of rutin and quercetin in Flos Sophorae Immaturus and esculin and esculetin in Cortex Fraxini. The effects of the irradiation time and the voltage applied on the infrared generator were investigated to acquire the optimum extraction conditions. It was demonstrated that far IR radiation substantially enhanced the extraction efficiency and the extraction time was significantly reduced from 3 h for conventional hot solvent extraction to 6 min for FIASE. The obtained extracts were subsequently analysed by CE-AD. The detection electrode was a 300-mu m-diameter carbon disc electrode at a detection potential of +0.90 V (vs. saturated calomel electrode). The relation between peak current and analyte concentration was linear over about three orders of magnitude. The proposed method has been applied to determine the bioactive constituents in real samples. (C) 2011 Elsevier Ltd. All rights reserved.

Abstract  Nitrate (NO(3)(-)) contamination of groundwater is a common problem throughout intensive agricultural areas (nonpoint source pollution). Current processes (e.g., ion exchange, membrane separation) for NO(3)(-) removal have various disadvantages. The objective of this study was to evaluate an electrocatalytic reduction process to selectively remove NO(3)(-) from groundwater associated with small agricultural communities. A commercially available ELAT (E-Tek Inc., Natick, MA) carbon cloth with a 30% surface coated Rh (rhodium) (1microg x cm(-1)) was tested at an applied potential of -1.5 V versus standard calomel electrode (SCE) with a Pt auxiliary electrode. Electrocatalytic reduction process (electrolysis) of NO(3)(-) was tested with cyclic voltammetry (CV) in samples containing NO(3)(-) and 0.1M NaClO(4)(-). Nitrate and NO(2)(-) concentrations in test solutions and groundwater samples were analyzed by ion chromatography (IC). The presence of Rh on the carbon cloth surface resulted in current increase of 36% over uncoated carbon cloths. The electrocatalysis experiments using Rh coated carbon cloth resulted in reduction of NO(3)(-) and NO(2)(-) on a timescale of minutes. Nitrite is produced as a product, but is rapidly consumed upon further electrolysis. Field groundwater samples subjected to electrocatalysis experiments, without the addition of NaClO(4)(-) electrolyte, also exhibited removal of NO(3)(-) on a timescale of minutes. Overall, results suggest that at an applied potential of -1.5 V with respect to SCE, Rh coated carbon cloth can reduce NO(3)(-) concentrations in field groundwater samples from 73 to 39 mg/L (16.58 to 8.82 mg/L as N) on a timescale range of 40-60 min. The electrocatalytic reduction process described in this study may prove useful for removing NO(3)(-) and NO(2)(-) from groundwater associated with nonpoint source pollution.

Abstract  Eichhornia crassipes (water hyacinth) is a non-native plant found in abundance in the Sacramento-San Joaquin River Delta (hereafter called Delta). This species has become a problem, clogging waterways and wetlands. Water hyacinth are also known to accumulate mercury. Recent attempts to curb its proliferation have included shredding with specialized boats. The purpose of this research is to better understand the ability of water hyacinth to phytoremediate mercury and to determine the effect of shredding and anoxic conditions on mercury speciation in plant tissue. In the field assessment, total mercury levels in sediment from the Dow Wetlands in the Delta were found to be 0.273 +/- 0.070 ppm Hg, and levels in hyacinth roots and shoots from this site were 1.17 +/- 0.08 ppm and 1.03 +/- 0.52 ppm, respectively, indicating bioaccumulation of mercury. Plant samples collected at this site were also grown in nutrient solution with 1 ppm HgCl2 under (1) aerobic conditions, (2) anaerobic conditions, and (3)with shredded plant material only. The greatest accumulation was found in the roots of whole plants. Plants grown in these conditions were also analyzed at Stanford Synchrotron Radiation Laboratory using Hg L3 X-ray Absorption Near Edge Spectroscopy (XANES), a method to examine speciation that is element-specific and noninvasive. Least-squares fitting of the XANES data to methylated and inorganic mercury(II) model compounds revealed that in plants grown live and aerobically, 5 +/- 3% of the mercury was in the form of methylmercury, in a form similar to methylmercury cysteine. This percentage increased to 16 +/- 4% in live plants grown anaerobically and to 22 +/- 6% in shredded anaerobic plants. We conclude that shredding of the hyacinth plants and, in fact, subjection of plants to anaerobic conditions (e.g., as in normal decay, or in crowded growth conditions) increases mercury methylation. Mechanical removal of the entire plant is significantly more expensive than shredding, but it may be necessary to avoid increased biomagnification of mercury in infested areas.

Abstract  Many biosensors have been developed to detect Hg(2+) using thymine-rich DNA. While sensor response to various cations is often studied to demonstrate selectivity, the effect of anions has been largely overlooked. Anions may compete with DNA for metal binding and thus produce a false negative result. Anions cannot be added alone; the cation part of a salt may cause DNA compaction and other effects, obscuring the role of anions. We find that the sensitivity of a FRET-based Hg(2+) probe is independent of Na(+) concentration. Therefore, by using various sodium salts, any change in sensitivity can be attributed solely to the effect of anions. Halide salts, sulfides, and amines are strong inhibitors; anions containing oxo or hydroxyl groups (e.g. nitrate, sulfate, phosphate, carbonate, acetate, and citrate) do not interfere with Hg(2+) detection even at 100 mM concentration. Mercury hydrolysis and its diffusion into polypropylene containers can also strongly affect the detection results. We conclude that thymine-rich DNA should be useful for Hg(2+) detection in many environmental water samples.

Abstract  Electropolymerization of poly-(o-phenylenediamine) (PoPD) film was performed in a micellar aqueous solution containing sodium dodecyl benzene sulfate (SDBS) by cyclic voltammetry at conducting glass electrode. The experimental results showed that the anionic micelle, i.e., SDBS, can greatly catalyze the electropolymerization reaction of oPD and reduce its oxidation potential from 0.97 to 0.74 V (vs. saturated calomel electrode). In the anionic micellar media, the local concentration of o-phenylenediamine (oPD) on the surface of electrode may be increased, and the oPD cation radicals are more stabilized in the hydrophobic microcircumstance of micelle, which is available to avoid hydrolysis degradation of PoPD and enhance the stability of the PoPD film. The spectroscopy and morphology of the films were characterized by FTIR spectroscopy and atomic force microscopy, respectively. The results suggested the possible presence of columnar structures when the electropolymerization is performed in the micellar medium.. (c) 2007 Wiley Periodicals, Inc.

Abstract  Autoimmune disorders result from a breakdown of immunologic tolerance leading to an immune response against self-molecules. In most instances the events that initiate the immune response to self-molecules are unknown, but a number of studies suggest associations with environmental and genetic factors and certain types of infections. The concordance of autoimmune diseases among identical twins is virtually always less than 50%, often in the 25-40% range. This observation, as well as epidemic clustering of some autoimmune diseases following xenobiotic exposure, reinforces the thesis that autoimmune disease is secondary to both genetic and environmental factors. In addition, because of individual genetic susceptibilities based not only on major histocompatibility complex differences but also on differences in toxin metabolism, lifestyles, and exposure rates, individuals will react differently to the same chemicals. With these comments in mind it is important to note that there have been associations of a number of xenobiotics with human autoimmune disease, including mercury, iodine, vinyl chloride, canavanine, organic solvents, silica, L-tryptophan, particulates, ultraviolet radiation, and ozone. In addition, there is discussion in the literature that raises the possibility that xenobiotics may also exacerbate an existing autoimmune disorder. In this article these issues are discussed, in particular, the evidence for the role of environmental agents in the initiation or progression of autoimmune conditions. With the worldwide deterioration of the environment, this is a particular important subject for human health. This is best illustrated by the epidemics of eosinophilic myalgia syndrome with shared characteristics that occurred about 20 years ago. Another example is the toxic oil syndrome of Spain in 1981 involving cooking oil led to both acute and chronic disease as well as formation of auto-antibodies to collagen, DNA, and skeletal muscle. Currently the question is risen whether there is a link between environmental estrogens and autoimmune disorders, especially since these illnesses are reported possibly more frequent. Yet for the time being, an answer is not available, since the current state of science with respect to autoimmunity and environmental agents is still in the early stages of hazard identification.

Abstract  Pore fluids from Clear Lake sediments collected near the abandoned Sulphur Bank Mercury Mine have low pH (locally <4) and elevated sulfate (>= 197 mmol/L), aluminum (>= 52 mmol/L), and iron (>= 28 mmol/L) contents derived from oxidation of sulfide minerals at the mine site. Acid mine drainage (AMD) is entering Clear Lake by advective subsurface flow nearest the mine and by diffusion at greater distances. Oxygen and hydrogen isotope ratios, combined with pore fluid compositions, constrain the sources and pathways of contaminated fluids. Sediment cores taken nearest the mine have the highest concentrations of dissolved sulfate, aluminum, and iron, which are contributed by direct subsurface flow of AMD from sufide-bearing waste rock. Sediment cores as far as 100 m west of the Clear Lake shoreline show the presence of AMD that originated in the acidic lake that occupies the abandoned Herman Pit at the mine site. High sulfate content in the AMD has the potential to promote the activity of sulfate-reducing bacteria in the organic-rich lake sediments, which leads to methylation of Hg(+2), making it both more toxic and bioavailable. Quantitative depletion of pore water sulfate at depth and sulfur isotope values of diagenetic pyrite near 0 parts per thousand indicate that sulfate availability limits the extent of sulfate reduction in the lake sediments away from the mine. Profiles of pore water sulfate in the sediments near the mine show that excess sulfate is available to support the activity of sulfate-reducing bacteria near the mine site. Enriched isotope values of dissolved sulfate (as high as 17.1 parts per thousand) and highly depleted isotope values for diagenetic pyrite (as low as - 22.6 parts per thousand) indicate active bacterial sulfate reduction in the AMD-contaminated sediments. Sulfate- and iron-rich acid mine drainage entering Clear Lake by shallow subsurface flow likely needs to be controlled in order to lower the environmental impacts of Hg in the Clear Lake ecosystem.

Abstract  Activated carbons chemically modified with sulfur and bromine are known for their greater effectiveness in capturing vapor Hg from coal combustion and other industrial flue gases. The stability of captured Hg in spent activated carbons determines the final fate of Hg and is critical to devising Hg control strategy. However, it remains a subject that is largely unknown, particularly for Br-treated activated carbons. Using a six-step sequential extraction procedure, this work evaluated the leaching potential of Hg captured with four activated carbons, one lignite-derived activated carbon, and three chemically treated with Br(2), KClO(3), and SO(2). The results demonstrated clearly the positive effect of Br- and SO(2)-treatment on the stability of captured Hg. The Hg captured with brominated activated carbon was very stable and likely in the form of mercurous bromide complex. Sulfur added at high temperature with SO(2) was able to stabilize a majority of Hg by forming sulfide and possibly sulfonate chelate. The presence of sulfate however made a small fraction of captured Hg (<10%) labile under mild conditions. Treating activated carbon with KClO(3) lowered the overall stability of captured Hg. A positive dependence of Hg stability on Hg loading temperature was observed for the first time.

Abstract  Bifunctional tetrakis(methylthio)-1,4-benzenedicarboxylic acid and Pb2+ ions form a robust porous net featuring free-standing thioether groups that allow reversible uptake of HgCl2.

Abstract  Cultures of the sulfate reducing bacteria Desulfovibrio desulfuricans were grown under anoxic conditions to study the effect of added sulfide, selenite and mercuric ions. A chemical trap consisting in a CuSO4 solution was used to control the poisoning effect induced by the bacterial production of hydrogen sulfide via the precipitation of CuS. Following the addition of Hg(2+), the formation of methylmercury (MeHg) was correlated to bacterial proliferation with most of MeHg found in the culture medium. A large fraction (50-80%) of added Hg(2+) to a culture ended up in a solid phase (Hg(0) and likely HgS) limiting its bioavailability to cells with elemental Hg representing ~40% of the solid. Following the addition of selenite, a small fraction was converted into Se(0) inside the cells and, even though the conversion to this selenium species increased with the increase of added selenite, it never reached more than 49% of the added amount. The formation of volatile dimethylselenide is suggested as another detoxification mechanism. In cultures containing both added selenite and mercuric ions, elemental forms of the two compounds were still produced and the increase of selenium in the residual fraction of the culture suggests the formation of mercuric selenite limiting the bioavailability of both elements to cells.

Abstract  In this work, the electrogravimetric behavior of copper electrodeposition on TiO2 electrodes was analyzed. Copper electrodeposition was carried out in 0.1 mol L-1 H2SO4 using several concentrations of CuSO4. The voltammetric curve displays a redox processes. The first redox process occurs in the region of -0.30 at 0.1 V (vs. saturated calomel electrode, SCE) and it is related to bulk Cu electrodeposition and stripping. For this cathodic process, it was observed that the mass gain increases both as the sweep rate decreases and as the concentration of copper increases. The second redox process, which occurs between -0.1 V and 0.35 V (vs. SCE), the stripping charge (and mass) are independent of both sweep rate and CuSO4 concentration and, finally, there is a saturation charge (and saturation mass) as the deposition time is increased. From the saturated mass, obtained using an electrochemical quartz crystal nanobalance, for this electrodeposition process (248 ng cm(-2)) a roughness factor of 1.8 was calculated for the TiO2 film. (C) 2009 Elsevier B.V. All rights reserved.

Abstract  Aluminium (Al) was evaluated for induction of oxidative stress and DNA damage employing the growing roots of Allium cepa L. as the assay system. Intact roots of A. cepa were treated with different concentrations, 0, 1, 10, 50, 100, or 200 microM of aluminium chloride, at pH 4.5 for 4 h (or 2 h for comet assay) at room temperature, 25+/-1 degrees C. Following treatment the parameters investigated in root tissue were Al-uptake, cell death, extra cellular generation of reactive oxygen intermediates (ROI), viz. O(2)(*-), H(2)O(2) and (*)OH, lipid peroxidation, protein oxidation, activities of antioxidant enzymes namely catalase (CAT), superoxide dismutase (SOD), guaiacol peroxidase (GPX), ascorbate peroxidase (APX); and DNA damage, assessed by comet assay. The findings indicated that Al triggered generation of extra-cellular ROI following a dose-response. Through application of specific enzyme inhibitors it was demonstrated that extra-cellular generation of ROI was primarily due to the activity of cell wall bound NADH-PX. Generation of ROI in root tissue as well as cell death was better correlated to the levels of root Al-uptake rather than to the concentrations of Al in ambient experimental solutions. Induction of lipid peroxidation and protein oxidation by Al were statistically significant. Whereas Al inhibited CAT activity, enhanced SOD, GPX and APX activities significantly; that followed dose-response. Comet assay provided evidence that Al induced DNA damage in a range of concentrations 50-200 microM, which was comparable to that induced by ethylmethane sulfonate (EMS), an alkylating mutagen served as the positive control. The findings provided evidence that Al comparable to biotic stress induced oxidative burst at the cell surface through up- or down-regulation of some of the key enzymes of oxidative metabolism ultimately resulting in oxidative stress leading to DNA damage and cell death in root cells of A. cepa.

Abstract  Mercury mine waste contains other toxic metals in addition to Hg, such as Ag, Cd, Cu, Ni, Pb, Fe, Mn, As, and Sb, which may contribute to environmental pollution. Leaching characteristics of mine waste treated by solar thermal desorption were studied, and removal and mobilization processes were evaluated. Concentrations of Cd, Ni, and Pb in mine waste leachates before thermal treatment do not exceed the limits in European standards, and after the treatment, their concentration decreased significantly in some samples. Hg is the only metal with concentrations above the European leaching limits, although, in the treated samples, the concentrations of dissolved Hg decreased significantly, showing the effectiveness of the thermal treatment. Thus, in the mining wastes sample AS, Hg concentrations decreased from 1100 mu g/L in the original sample to 73 mu g/L in the treated sample, although this concentration is above the European leachate concentration levels (30 mu g/L). In the calcine sample M03, Hg leached only decreased from 13 to 9 mu g/L in the treated sample, although when characterized by percolation experiments, these levels were below the European leachate limits for nonhazardous solid-waste landfills. In the soil samples M02 and BS, the Hg leaching showed an opposite behavior, indicating in the Azogue soil sample M02 that the Hg concentration decreased from 66 to 6 mu g/L in the treated sample, while in the Bayarque soil sample BS, the concentration of leached Hg increased from 9 to 51 mu g/L in the treated sample. Results of geochemical modeling showed that the dominant species in the leachates of the untreated samples were HgClOH, Hg(OH)(2), HgCl2, HgCl3-, and Hg-0, which was in agreement with the high Hg and chloride concentrations in some leachates. In the leachates of the treated samples, the dominant species were Hg-0, Hg(OH)(2), HgClOH, and HgCl2.

Abstract  Glutamine synthetase (GS) is an essential detoxification enzyme that plays an important role in stress responses; however, little information regarding the function of this enzyme in hymenopteran insects is available. In the present study, we isolated and characterized the gene encoding GS in the Asiatic honeybee, Apis cerana cerana. Multiple alignments and a phylogenetic analysis of GS sequences showed that AccGS belongs to the GSII superfamily and clusters with invertebrate GSs. Real-time quantitative PCR data demonstrated that AccGS is expressed at all developmental stages and in all tissues, with the highest expression observed in the sixth larval instar and in the brain. Moreover, AccGS expression is highly regulated by environmental stress, including xenobiotic, temperature, and ultraviolet light stresses. A disc diffusion assay showed that the recombinant AccGS protein confers resistance to mercuric chloride (HgCl2) stress in E. coli. This suggests that AccGS may play multiple roles in early development and in environmental stress responses.

Abstract  The Nabburg-Wolsendorf vein-type fluorites in SE Germany which are characterized by a pronounced timebound variation in mineral color (blue -> black -> green -> white/colorless -> yellow -> brown) were investigated for their accessory minerals included in or associated with these different fluorite types. Nabburg-Wolsendorf is not a unidirectional fluorite mineralization but a polyphase mineralizing process with several repetitions of the various color types during the vein mineralization event. Accessory minerals of the fluorite mineralization include silicates, sulfates, oxide/hydroxides, phosphates, sulfides and carbonates. These minerals are intimately intergrown with fluorite in the vein-type mineralization and are efficient tools to broaden knowledge on the depositional environment of fluorite that is otherwise poor in marker minerals for redox conditions, temperature, alkalinity/acidity and fluid viscosity. Pyrite, galena and cinnabar, are indicative of hypogene processes, while uranyl phosphates and APS minerals furnish evidence for supergene mineralizing processes. Some minor constituents may be used as marker minerals of redox conditions (hematite, galena, and goethite) or held to be characteristic for the changing pH regime (kaolinite and smectite). Oxidizing conditions prevailed during fluorite mineralization, excluding some phases when fetid and white fluorite precipitation ran through a maximum. Yellow-brown honey spar marks the oxidizing physical-chemical conditions by its brown mineral color at the end of fluorite mineralization. Oxidizing conditions prevailed also during supergene mineralization.

The pH of the mineralizing fluids of the hypogene stages was greater than pH 7. During the supergene stage, Eh fluctuated, but was mainly >0; the pH of fluids ranged between 7 and 4. The black color of fetid fluorite and its pungent odor resulted from the U present primarily in its tetravalent state. Incomplete haloes recognized in some fetid fluorites reflect "frozen" uranium disequilibria and an early phase of supergene alteration. In this respect, the fetid fluorite ("Stinkspat") plays an important part and held to be a marker for the radioactive "hot spot" as well as "ghost" uranium mineralization. Fetid fluorite is defined as to its mineral color, morphology and characteristic spectral features so as to allow for a precise distinction from other dark blue or green fluorite varieties by its outward appearance and easy-to-handle methods. The accessory minerals under study are indicative of the depocentre of the fluids which lies close to an unconformity but does not, however, deliver information on the source of the mineralizing fluids. The nearness to the potential source rock of the fluids can only concluded from the presence of cerite-(Ce) which formed prior to fluorite. This REE silicate is cast as a marker of the root zone of the fluorite veins which fade out into late Variscan granites. Cerium is assumed to have been derived from monazite an accessory mineral largely found outside the fluorite veins, proper, in the late Variscan granites. In the waning stages of fluorite mineralization different types of REE-bearing phosphates, belonging to the rhabdophane solid solution series, and some APS minerals (aluminum-phosphate-sulfate solid solution series) evolved. (C) 2010 Elsevier B.V. All rights reserved.

Abstract  Effects of coexistent gases (HCl, SO(2), O(2), CO(2), and H(2)O) in simulated coal combustion flue gas on mercury removal by a commercial activated carbon (coconut shell AC) were investigated in a laboratory-scale fixed-bed reactor at 80 degrees C. To clarify the contribution of the Deacon reaction 2HCl + 1/2O(2) = Cl(2) + H(2)O (1) on the mercury sorption mechanisms, the experiments were also conducted in the presence of Cl(2) (in the absence of HCl). The characteristics (thermal stability) of the mercury species formed on the AC under the various sorption conditions were investigated by the temperature-programmed decomposition desorption (TPDD) technique. It was found that O(2) promoted mercury removal in the presence of SO(2); however, SO(2) suppressed mercury removal irrespective of the presence of O(2). The promotion of mercury removal by the presence of O(2) may result from the Deacon reaction. However, SO(2) seemed to inhibit the Deacon reaction. It is thought that mercury species formed on AC through the Deacon reaction was HgCl(x) (including HgCl(2)), which decomposed and desorbed at around 300 degrees C. This was supported by confirmation of the presence of HgCl(2) vapor in the reactor effluent gas in TPDD experiments. From the comparison of mercury removal in the gas containing 1 ppmv HCl and gas containing 0.5 ppmv Cl(2) system in the presence of SO(2), O(2), CO(2) and H(2)O, it was suggested that Cl(2) enhances mercury removal more efficiently than HCl. Therefore, efficient removal of mercury with AC is possible to achieve via promoting the Deacon reaction. The high-temperature TPDD peaks were observed at around 500 degrees C in TPDD spectra of the spent sorbents used in mercury removal in the presence of Cl(2) (or high concentrations of HCl), SO(2), O(2), CO(2), and H(2)O. This TPDD peak temperature range is very close to the decomposition temperature of HgSO(4). We suggest that the high-temperature mercury desorption peaks are related to the decomposition of mercury species similar to mercury sulfate containing chlorine (HgS(x)O(y)Cl(z)) on AC.