Hg Vapor Research Articles

Effect of alloy disorder on photoluminescence in HgCdTe

Hg1−xCdxTe samples with x = 0.38 and 0.57 fabricated by molecular beam epitaxy, both as-grown and after annealing, were studied. Photoluminescence (PL) was measured in the temperature range 4.2 < T < 300 K. The PL peak energy was found to be less than that of the energy gap by a certain value δE that depended on temperature. This effect was attributed to recombination of excitons localized at composition non-homogeneities. An analysis was carried out that provided a way for evaluation of a non-homogeneity measure. The amplitude of the non-homogeneities was shown to decrease by about 50% as a result of post-growth annealing in a He atmosphere and Hg vapour.

Photo-reduction of hexavalent chromium in aqueous solution in the presence of zinc oxide as semiconductor catalyst

Common sources of chromium in wastewater are electroplating and leather industries. Hexavalent chromium is more toxic and carcinogenic compared to its trivalent counterpart. Conversion of Cr(VI) to Cr(III) in an aqueous medium by photocatalytic reduction using UV radiation and ZnO semiconductor catalyst has been investigated using potassium dichromate as the model compound. Effects of the process parameters such as ZnO loading (0–3 g/L) and intensity of UV radiation (0–125 W medium pressure Hg vapour lamp) on photocatalytic reduction were investigated. Initial concentration of substrate solution was varied from 40 to 120 mg/L. A comparison of the performance of the ZnO photocatalyst achieved in this study with that reported in the literature for photocatalytic and conventional processes is presented. The initial rate of the photochemical method was found to be independent of the concentration of potassium dichromate. Methanol was added as a hole scavenger for enhancement of the photo-reduction. Initial rate of photo-reduction was found to be independent of the concentration of methanol above a particular value. A probable mechanism and the corresponding kinetic model have been proposed for the photo-reduction and tested by experimental results. An alternative rate equation based on the LHHW model compares well with the mechanistic rate equation.

A Nano-Selenium Reactive Barrier Approach for Managing Mercury over the Life-Cycle of Compact Fluorescent Lamps

Compact fluorescent lamps contain small quantities of mercury, release of which can lead to human exposures of potential concern in special cases involving multiple lamps, confined spaces, or young children. The exposure scenarios typically involve solid lamp debris that slowly releases elemental mercury vapor to indoor spaces. Here we propose and demonstrate a reactive barrier approach for the suppression of that mercury release, and demonstrate the concept using uncoated amorphous nanoselenium as the reactive component. Multilayer structures containing an impregnated reactive layer and a mercury vapor barrier are fabricated, characterized, and evaluated in three exposure prevention scenarios: carpeted break sites, disposal/recycling bags, and boxes as used for retail sales, shipping, and collection. The reactive barriers achieve significant suppression of mercury release to indoor spaces in each of thethree scenarios. The nanoselenium barriers also exhibit a unique indicator function that can reveal the location of Hg contamination by local reaction-induced change in optical properties. The article also presents results on equilibrium Hg vapor pressure above lamp debris, mathematical modeling of reaction and transport processes within reactive barriers, and landfill stability of nanoselenium and its reaction products.

Methylmercury determination using a hyphenated high performance liquid chromatography ultraviolet cold vapor multipath atomic absorption spectrometry system

The present work investigates the use of a multipath cell atomic absorption mercury detector for mercury speciation analysis in a hyphenated high performance liquid chromatography assembly. The multipath absorption cell multiplies the optical path while energy losses are compensated by a very intense primary source. Zeeman-effect background correction compensates for non-specific absorption. For the separation step, the mobile phase consisted in a 0.010% m/v mercaptoethanol solution in 5% methanol (pH = 5), a C 18 column was used as stationary phase, and post column treatment was performed by UV irradiation (60 °C, 13 W). The eluate was then merged with 3 mol L − 1 HCl, reduction was performed by a NaBH 4 solution, and the Hg vapor formed was separated at the gas–liquid separator and carried through a desiccant membrane to the detector. The detector was easily attached to the system, since an external gas flow to the gas–liquid separator was provided. A multivariate approach was used to optimize the procedure and peak area was used for measurement. Instrumental limits of detection of 0.05 µg L − 1 were obtained for ionic (Hg 2+) and HgCH 3 +, for an injection volume of 200 µL. The multipath atomic absorption spectrometer proved to be a competitive mercury detector in hyphenated systems in relation to the most commonly used atomic fluorescence and inductively coupled plasma mass spectrometric detectors. Preliminary application studies were performed for the determination of methyl mercury in sediments.

Thermal analysis of sulphur impregnated activated carbons with mercury adsorbed from the vapour phase

Activated carbons (AC), particularly those containing sulphur, are effective adsorbents for mercury (Hg) vapour at elevated temperatures. Activated carbon-based technologies are expected to become a major part of the strategy for controlling mercury emission from coal-fired power plants. Understanding the mechanism of mercury adsorption on sulphur impregnated activated carbons (SIAC) is essential to optimizing activated carbons for better mercury removal efficiency and to developing technologies for the handling of the spent AC.

Brewster angle reflection measurements of Hg density and laser deflection (Schlieren) measurements of Hg density gradients in an ultra-high pressure arc lamp

A Brewster angle reflection measurement is used to determine the Hg vapor density at the arc tube wall of an ultra-high pressure lamp. The density measurement in combination with the wall temperature yields a pressure of 201 ± 11 bar. This lamp pressure in combination with an arc core temperature measurement yields an arc core Hg vapor density of 1.78 × 1020 cm−3, which agrees with the density from resonance collisional line broadening measurements of the 1014 nm Hg line. These density results are combined with Abel inverted laser deflection or schlieren measurements to determine a density/temperature map of the Hg vapor in the lamp. The laser deflection technique is sensitive in the arc core and mantle, unlike emission techniques which are sensitive only in the arc core.

Self-consistent compensated microfield model for a strongly coupled plasma

A compensated microfield model of plasma nonideality is proposed as an improvement of the traditional microfield models. In this model, a double contribution of a microfield to the truncation of statistical sums removed. The new method of truncation of the statistical sums of atoms or ions is compared with the results of experiments and computations performed by well-known Debye-type and other models. It is shown that only the microfield model correctly describes experiments. Ionization of Li and Hg atoms is calculated. The effect of metallization of plasma—an abrupt increase of ionization from zero to a single ionization at low temperatures and nearly normal densities—is qualitatively described. The results of calculation of Hg vapor ionization qualitatively agree with known experimental results on the measurement of electric conductivity of this vapor.

Effect of orientation of the substrate on the conditions of growth of HgTe films by molecular beam epitaxy

The kinetics of growth of HgTe films under conditions of molecular beam epitaxy on the (310)- and (100)-oriented CdTe buffer layers is studied by ellipsometry. It is established that the minimum pressure of Hg vapors required for growth of HgTe films on the (310) surface is four times lower than the pressure required for growth on the (100) surface. It is found that, during the growth of HgTe films, no Te adsorption layer is formed on the (310) surface, whereas a Te adsorption layer is actually formed on the (100) surface. The equivalent thickness of this layer is 1 A.

Optimization of a single-drop microextraction method for multielemental determination by electrothermal vaporization inductively coupled plasma mass spectrometry following in situ vapor generation

A headspace single-drop microextraction (HS-SDME) method has been developed in combination with electrothermal vaporization inductively coupled plasma mass spectrometry (ETV-ICP-MS) for the simultaneous determination of As, Sb, Bi, Pb, Sn and Hg in aqueous solutions. Vapor generation is carried out in a 40 mL volume closed-vial containing a solution with the target analytes in hydrochloric acid and potassium ferricyanide medium. Hydrides (As, Sb, Bi, Pb, Sn) and Hg vapor are trapped onto an aqueous single drop (3 µL volume) containing Pd(II), followed by the subsequent injection in the ETV. Experimental variables such as medium composition, sodium tetrahydroborate (III) volume and concentration, stirring rate, extraction time, sample volume, ascorbic acid concentration and palladium amount in the drop were fully optimized. The limits of detection (LOD) (3 σ criterion) of the proposed method for As, Sb, Bi, Pb, Sn and Hg were 0.2, 0.04, 0.01, 0.07, 0.09 and 0.8 µg/L, respectively. Enrichment factors of 9, 85, 138, 130, 37 and 72 for As, Sb, Bi, Pb, Sn and Hg, respectively, were achieved in 210 s. The relative standard deviations ( N = 5) ranged from 4 to 8%. The proposed HS-SDME-ETV-ICP-MS method has been applied for the determination of As, Sb, Bi, Pb, Sn and Hg in NWRI TM-28.3 certified reference material.

Mercury diffusion in gold and silver thin film electrodes on quartz crystal microbalance sensors

Diffusion behavior of mercury into both gold and silver electrodes of polished and roughened quartz crystal microbalances (QCMs) is presented. Several QCM devices were exposed to mercury vapor for 8 h and allowed to desorb for 5 h under controlled nitrogen atmosphere. The process was repeated for different Hg concentrations of 1.02, 1.87 and 3.65 mg/m 3 at an elevated temperature of 40 °C. The chemical composition and surface morphology of each QCM surface was characterized by Inductively Coupled Plasma Mass Spectroscopy (ICP-MS), Secondary Ion Mass Spectroscopy (SIMS), Atomic Force Microscope (AFM) and Field Emission Secondary Electron Microscope (FE-SEM). The Ag electrodes were found to contain up to 16% more adsorbed/amalgamated Hg by mass than the Au samples. It was found that the ratio of amalgamated to adsorbed Hg is less for Au than Ag. SIMS analysis confirmed high Hg diffusion through rough substrates, 40 days after Hg exposure. In situ sticking probability of the tested mercury vapor concentrations to Au and Ag surfaces at 40 °C was found to drop at quicker rates than the reported Hg–Au and Hg–Ag room temperature values. Overall, in the context of Hg vapor phase gas sensing applications, the rougher gold substrate was found to outperform the other samples due to its superior adsorption/desorption properties.

Lâmpada de Hg para experimentos e demonstrações de física moderna: introdução ao efeito fotoelétrico e outros tópicos

Neste trabalho são apresentados os resultados de um projeto para o ensino de física moderna e contemporânea para um curso de licenciatura em física. Os objetivos do projeto consistiram no desenho, construção e utilização de uma lâmpada de vapor de Hg para atividades práticas e demonstrações didáticas. Questões relativas à utilização deste equipamento seguindo padrões de segurança serão detalhadas. Será dada ênfase à discussão metodológica para aplicações do instrumento na introdução do efeito fotoelétrico e outros assuntos da física moderna.

Use of a Solution Cathode Glow Discharge for Cold Vapor Generation of Mercury with Determination by ICP-Atomic Emission Spectrometry

A novel vapor-generation technique is described for mercury determination in aqueous solutions. Without need for a chemical reducing agent, dissolved mercury species are converted to volatile Hg vapor in a solution cathode glow discharge. The generated Hg vapor is then transported to an inductively coupled plasma for determination by atomic emission spectrometry. Mercury vapor is readily generated from a background electrolyte containing 0.1 M HNO 3. Vapor generation efficiency was found to be higher by a factor of 2-3 in the presence of low molecular weight organic acids (formic or acetic acids) or alcohols (ethanol). Optimal conditions for discharge-induced vapor generation and reduced interference from concomitant inorganic ions were also identified. However, the presence of chloride ion reduces the efficiency of Hg-vapor generation. In the continuous sample introduction mode, the detection limit was found to be 0.7 microg L (-1), and repeatability was 1.2% RSD ( n = 11) for a 20 microg L (-1) standard. In comparison with other vapor generation methods, it offers several advantages: First, it is applicable to both inorganic and organic Hg determination; organic mercury (thiomersal) can be directly transformed into volatile Hg species without the need for prior oxidation. Second, the vapor-generation efficiency is high; the efficiency (with formic acid as a promoter) is superior to that of conventional SnCl 2-HCl reduction. Third, the vapor generation is extremely rapid and therefore is easy to couple with flow injection. The method is sensitive and simple in operation, requires no auxiliary reagents, and serves as a useful alternative to conventional vapor generation for ultratrace Hg determination.

Mercury pollution in Guizhou, Southwestern China — An overview

Mercury (Hg) is a global pollutant and poses a worldwide concern due to its high toxicity. Guizhou province is recognized as a heavily Hg-polluted area in China due to both the special geochemical background and human activities. Here an integrated overview of current knowledge on the behavior of Hg in environments, as well as human health risk with respect to Hg contaminations in Guizhou was presented. Two key anthropogenic Hg emission sources in Guizhou were coal combustion and metals smelting, which dominantly contributed to the high levels of Hg in local ecosystems and high fluxes of Hg deposition. The annual Hg emission from anthropogenic sources ranged between 22.6 and 55.5 t, which was about 6.3–10.3% of current total Hg emissions in China. Meanwhile, Hg Hg-enriched soil in the province serves an important natural Hg emission source to the ambient air. The local environment of Hg mining and zinc smelting areas are seriously contaminated with Hg. It is demonstrated that rice growing in Hg Hg-contaminated soil can accumulate methylmercury (MeHg) to a level to pose health threat to local inhabitants whose staple food is rice. Local inhabitants in Hg mining areas are exposed to Hg through inhalation of Hg vapor and consumption of rice with high level of MeHg. Rice intake is indeed the main MeHg exposure pathway to local inhabitants in Hg mining areas in Guizhou, which is contrary to the general point of view that fish and fish products are the main pathway of MeHg exposure to humans.

Quantitative x-ray absorption imaging with a broadband source: application to high-intensity discharge lamps

The case of x-ray absorption imaging in which the x-ray source is broadband and the detector does not provide spectral resolution is analysed. The specific motivation is observation of the Hg vapour distribution in high-intensity discharge (HID) lamps. When absorption by the vapour is small, the problem can be couched accurately in terms of a mean absorption cross section averaged over the x-ray spectral distribution, weighted by the energy-dependent response of the detector. The method is tested against a Au foil standard and then applied to Hg. The mean absorption cross section for Hg is calculated for a Ag-anode x-ray tube at accelerating voltages of 25, 30 and 35 kV, and for HIDs in fused silica or polycrystalline alumina arc tubes.

Mercury vapor release from broken compact fluorescent lamps and in situ capture by new nanomaterial sorbents.

The projected increase in the use of compact fluorescent lamps (CFLs) motivates the development of methods to manage consumer exposure to mercury and its environmental release at the end of lamp life. This work characterizes the time-resolved release of mercury vapor from broken CFLs and from underlying substrates after removal of glass fragments to simulate cleanup. In new lamps, mercury vapor is released gradually in amounts that reach 1.3 mg or 30% of the total lamp inventory after four days. Similar time profiles but smaller amounts are released from spent lamps or from underlying substrates. Nanoscale formulations of S, Se, Cu, Ni, Zn, Ag, and WS2 are evaluated for capture of Hg vapor under these conditions and compared to conventional microscale formulations. Adsorption capacities range over 7 orders of magnitude, from 0.005 (Zn micropowder) to 188 000 μg/g (unstabilized nano-Se), depending on sorbent chemistry and particle size. Nanosynthesis offers clear advantages for most sorbent chemistries. Unstabilized nano-selenium in two forms (dry powder and impregnated cloth) was successfully used in a proof-of-principle test for the in situ, real-time suppression of Hg vapor escape following CFL fracture.

Indoor Concentrations of Hg Vapor Following Various Spill Scenarios

Hg vapor concentrations were measured in an indoor full-scale test environment representative of homes in the rural highlands of Peru, the location of an Hg spill in June 2000. We tested several scenarios of liquid Hg spilled onto a compacted dirt floor in a test room to determine the effect of various parameters, including liquid Hg surface area, temperature, air change rate, and Hg oxidation on room vapor concentrations. The measurements demonstrated that an increase in surface area and/or temperature significantly increased the evaporation rate, whereas oxidation (or age of the Hg) reduced the evaporation rate. We also verified that the Hg vapor analyzers used to test indoor air were capable of detecting very small spills.

Irreversible color vision losses in patients with chronic mercury vapor intoxication

This longitudinal study addresses the reversibility of color vision losses in subjects who had been occupationally exposed to mercury vapor. Color discrimination was assessed in 20 Hg-exposed patients (mean age = 42.4 +/- 6.5 years; 6 females and 14 males) with exposure to Hg vapor during 10.5 +/- 5.3 years and away from the work place (relative to 2002) for 6.8 +/- 4.2 years. During the Hg exposure or up to one year after ceasing it, mean urinary Hg concentration was 47 +/- 35.4 mug/g creatinine. There was no information on Hg urinary concentration at the time of the first tests, in 2002 (Ventura et al., 2005), but at the time of the follow-up tests, in 2005, this value was 1.4 +/- 1.4 microg/g creatinine for patients compared with 0.5 +/- 0.5 microg/g creatinine for controls (different group from the one in Ventura et al. (2005)). Color vision was monocularly assessed using the Cambridge Colour Test (CCT). Hg-exposed patients had significantly worse color discrimination (p < 0.02) than controls, as evaluated by the size of MacAdam's color discrimination ellipses and color discrimination thresholds along protan, deutan, and tritan confusion axes. There were no significant differences between the results of the study in Ventura et al. (2005) and in the present follow-up measurements, in 2005, except for worsening of the tritan thresholds in the best eye in 2005. Both chromatic systems, blue-yellow and red-green, were affected in the first evaluation (Ventura et al., 2005) and remained impaired in the follow-up testing, in 2005. These findings indicate that following a long-term occupational exposure to Hg vapor, even several years away from the source of intoxication, color vision impairment remains irreversible.

Simultaneous Determination of Species-Specific Isotopic Composition of Hg by Gas Chromatography Coupled to Multicollector ICPMS

This work presents the simultaneous online determination of the isotopic composition of different Hg species in a single sample by the hyphenation of gas chromatography (GC) with multicollector-inductively coupled plasma mass spectrometry (MC-ICPMS). With the use of commercially available instrumentation, precise and accurate species-specific Hg isotope delta values (per mil deviation of the Hg isotope ratio in the sample relative to a reference standard) have been obtained online from consecutive GC transient signals. The use of isothermal temperature programs to extend the elution of the Hg species, the proper selection of the peak integration window, as well as the preconcentration of real samples are critical to provide optimal counting statistics. Also, isotope ratio drift during transient signal elution was overcome by introducing a mixed Hg(II) and MeHg standard bracketing scheme and expressing all results using the delta-notation relative to SRM NIST-3133. Using the proposed methodology, we have obtained an external 2SD precision of 0.56 per thousand for delta (202)Hg that is more than 10 times smaller than the overall Hg stable isotope variation thus far observed in terrestrial samples. The measurement of species-specific Hg isotopic composition relative to SRM NIST-3133 has been validated versus two other analytical techniques, i.e., conventional nebulization (CN) of Hg(II) solution and cold vapor (CV) generation of Hg (0) vapor. A good agreement between the species-specific delta values obtained by the different techniques has been obtained in secondary fractionated reference standard (UM-Almaden) and environmental matrixes, i.e., BCR-CRM 464 (tuna fish) and IAEA-085 (human hair). The results show mass-dependent and mass-independent fractionation in environmental samples, i.e., mass-independent fractionation of odd isotopes (199)Hg and (201)Hg in tuna fish was observed. This methodology provides new possibilities for the future study of species-specific stable isotope geochemistry of Hg and other trace metals.

Mercury exposure in the population from Wuchuan mercury mining area, Guizhou, China

Mercury (Hg) exposure in the population from Wuchuan mercury mining area (WMMA), Guizhou, China, was evaluated by human hair Hg investigation. Total gaseous mercury (TGM) in the ambient air and Hg in rice were measured to assess human risk of Hg exposure. High TGM concentrations in the ambient air were found near smelting workshop. Rice not only contained high total mercury (T-Hg) which ranged from 6.0–113 ng/g, but also contained highly elevated methylmercury (Me-Hg) which ranged from 3.1–13.4 ng/g. The means of hair T-Hg concentrations were 33.9 μg/g and 21.5 μg/g at YQG and JXC sites, respectively. Residents from other sites also reflected a certain level of Hg exposure. Age had no significant effect on hair Hg levels, but male had higher hair T-Hg concentrations due to occupational exposure and also higher Me-Hg levels which might be related to larger amount of rice consumption. Hair may be a useful tool for monitoring human exposure of Hg vapor in Hg-mining areas. By a preliminary estimation, the inhalation of Hg polluted air was the main route of inorganic Hg exposure to the smelting workers and vicinal residents; but the population in the study area was also at a potential risk of Me-Hg exposure via rice intake.

Experimental Bias Involved in the Collection of Gaseous Elemental Mercury by the Gold Amalgam Method

The analytical bias involved in the application of the gold (Au) amalgamation method for gaseous elemental mercury (Hg) analysis was investigated as a function of three major parameters such as the total sampling volume, concentration levels of Hg samples, and differences in the tube sampler used for replicate sampling. Gaseous standards of Hg were prepared at five different concentration levels (S1–S5, ranging from the highest 876 ng m−3(S1) to the lowest 16.6 ng m−3 (S5) by mixing Hg vapor and ultrapure N2 gas at varying ratios. Each standard gas type was then analyzed by the Au amalgam method by adjusting sampling volumes to a large degree (0.1, 0.5, 1, 5, and 10 L). All of experiments were basically conducted to obtain five replicate analyses using five individual tubes at a given sampling volume. An ancillary experiment was also performed to obtain replicate data using a single tube for comparison against those data sets obtained using multiple tube applications. The overall results are evaluated in ...