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Sample records for odd-mass hg isotopes

  1. QPNM calculation for the ground state magnetic moments of odd-mass deformed nuclei: 157-167Er isotopes

    NASA Astrophysics Data System (ADS)

    Yakut, H.; Guliyev, E.; Guner, M.; Tabar, E.; Zenginerler, Z.

    2012-08-01

    A new microscopic method has been developed in the framework of the Quasiparticle-Phonon Nuclear Model (QPNM) in order to investigate spin polarization effects on the magnetic properties such as magnetic moment, intrinsic magnetic moment and effective gs factor of the ground state of odd-mass 157-167Er isotopes. The calculations were performed using both Tamm-Dancoff Approximation (TDA) and Quasiparticle Random-Phase Approximation (QRPA). Reasonably good agreement has been obtained between the QRPA results and the relevant experimental data. Furthermore the variation of the intrinsic magnetic moment gK values with the mass number A exhibits similar behavior for both theoretical and experimental results. From the compression of the calculated intrinsic magnetic moment values with the experimental data the spin-spin interaction parameter has been found as χ=(30/A) MeV for odd-mass 157-167Er isotopes. Our results clarify the possibility of using this new method to describe the magnetic properties of odd-mass deformed nuclei.

  2. Shape-changing particle decays of 185 Bi and structure of the lightest odd-mass Bi isotopes

    NASA Astrophysics Data System (ADS)

    Andreyev, A. N.; Ackermann, D.; Heßberger, F. P.; Heyde, K.; Hofmann, S.; Huyse, M.; Karlgren, D.; Kojouharov, I.; Kindler, B.; Lommel, B.; Münzenberg, G.; Page, R. D.; van de Vel, K.; van Duppen, P.; Walters, W. B.; Wyss, R.

    2004-05-01

    Proton and α decay of the proton-rich nuclide 185 Bi has been restudied in more detail in the complete fusion reaction 93 Nb ( 95 Mo ,3n ) 185 Bi at the velocity filter SHIP. The observed decay pattern of 185 Bi and of the heavier odd-mass isotopes 187,189,191,193 Bi are interpreted based on potential-energy surface calculations. It is shown that the experimental systematics of the particle decays and of the excited states in these nuclei (where known) can be explained by the prolate-oblate shape co-existence at low excitation energy. The observed state in 185 Bi is proposed to be of prolate nature, which is in contrast with the previously proposed oblate interpretation.

  3. Mass-Dependent and -Independent Fractionation of Hg Isotopes by Photoreduction in Aquatic Systems

    NASA Astrophysics Data System (ADS)

    Bergquist, Bridget A.; Blum, Joel D.

    2007-10-01

    Mercury (Hg) isotopes can be used as tracers of Hg biogeochemical pathways in the environment. The photochemical reduction of aqueous Hg species by natural sunlight leads to both mass-dependent fractionation (MDF) of Hg isotopes and mass-independent fractionation (MIF) of the odd-mass isotopes, with the relation between the MIF for the two odd isotopes being distinct for different photoreduction pathways. Large variations in MDF and MIF are observed in fish and provide new insights into the sources and bioaccumulation of Hg in food webs. MIF in fish can also be used to estimate the loss of methylmercury via photoreduction in aquatic ecosytems.

  4. Phase transition studies of the odd-mass 123‑135Xe isotopes based on SU(1,1) algebra in IBFM

    NASA Astrophysics Data System (ADS)

    Jafarizadeh, M. A.; Fouladi, N.; Ghapanvari, M.; Fathi, H.

    2016-07-01

    In this paper, we have investigated the positive-parity states in the odd-mass transitional 123‑135Xe isotopes within the framework of the interacting boson-fermion model. Two solvable extended transitional Hamiltonians which are based on SU(1,1) algebra are employed to provide an investigation of quantum phase transition (QPT) between the spherical and deformed gamma — unstable shapes along the chain of Xe isotopes. The low-states energy spectra and B(E2) values for these nuclei have been calculated and compared with the experimental data. The predicted excitation energies and B(E2) transition rates of the odd isotopes are found to agree well with the experimental data. We have also analyzed the critical behavior of even-odd Xe isotopes via Catastrophe Theory in combination with a coherent state formalism to generate energy surfaces and special isotopes which are the best candidates for the critical point are identified.

  5. β -decay rates of odd-mass neutron-rich isotopes in the deformed quasiparticle random-phase approximation with realistic interactions

    NASA Astrophysics Data System (ADS)

    Ni, Dongdong; Ren, Zhongzhou

    2015-09-01

    The deformed quasiparticle random-phase approximation with realistic nucleon-nucleon interactions is extended for the β- decay of odd-mass neutron-rich Kr, Sr, Zr, and Mo isotopes, from their longest-lived isotopes to the experimentally unknown nuclei. The particle-particle and particle-hole channels of residual interactions are handled in large single-particle model spaces, based on the Brückner G matrix with charge-dependent Bonn nucleon-nucleon forces. Both allowed Gamow-Teller and first-forbidden transitions are considered and different treatments for odd-mass systems are emphasized. The sensitivity of the calculated results to the single-particle level scheme and the particle-particle strength is discussed. The calculated Gamow-Teller strengths are analyzed, together with the contributions from first-forbidden transitions. The calculated half-lives are found to agree well with the experimental data over the orders of magnitude from 10-2 to 103 s.

  6. Stable mercury isotope ratios as tracers for Hg cycling at the inoperative New Idria Hg mine, California

    NASA Astrophysics Data System (ADS)

    Wiederhold, J. G.; Jew, A. D.; Brown, G. E.; Bourdon, B.; Kretzschmar, R.

    2010-12-01

    The seven stable isotopes of Hg are fractionated in the environment as a result of mass-dependent (MDF) and mass-independent (MIF) fractionation processes that can be studied in parallel by analyzing the ratios of even and odd mass Hg isotopes. MDF and MIF Hg isotope signatures of natural samples may provide a new tool to trace sources and transformations in environmental Hg cycling. However, the mechanisms controlling the extent of kinetic and equilibrium Hg isotope fractionations are still only partially understood. Thus, development of this promising tracer requires experimental calibration of relevant fractionation factors as well as assessment of natural variations of Hg isotope ratios under different environmental conditions. The inoperative Hg mine in New Idria (California, USA) represents an ideal case study to explore Hg isotope fractionation during Hg transformation and transport processes. More than a century of Hg mining and on-site thermal refining to obtain elemental Hg until 1972 produced large volumes of contaminated mine wastes which now represent sources of Hg pollution for the surrounding ecosystems. Here, we present Hg isotope data from various materials collected at New Idria using Cold-Vapor-MC-ICPMS with a long-term δ202Hg reproducibility of ±0.1‰ (2SD). Uncalcined mine waste samples were isotopically similar to NIST-3133 and did not exhibit any MIF signatures. In contrast, calcine samples, which represent the residue of the thermal ore processing at 700°C, had significantly heavier δ202Hg values of up to +1.5‰. In addition, we observed small negative MIF anomalies of the odd-mass Hg isotopes in the calcine samples, which could be caused either by nuclear volume fractionation or a magnetic isotope effect during or after the roasting process. The mass-dependent enrichment of heavy Hg isotopes in the calcine materials indicates that light Hg isotopes were preferentially removed during the roasting process, in agreement with a previous

  7. Investigation of 198,200Hg isotopes

    NASA Astrophysics Data System (ADS)

    Diaz Varela, A.; Rand, E. T.; Garrett, P. E.; Bildstein, V.; Burbadge, C.; Hadinia, B.; Jamieson, D. S.; Jimeddorj, B.; Laffoley, A. T.; Leach, K. G.; Maclean, A. D.; Radich, A.; Svensson, C. E.; Ball, G. C.; Faestermann, T.; Hertenberger, R.; Wirth, H.-F.; Rebeiro, B.; Triambak, S.

    2015-10-01

    Limits on the electric dipole moment (EDM) continue to decrease for 199Hg, which provides the most stringent upper limit for a nuclear EDM to date. The E 3 and E 1 strength distributions to the ground state of 199Hg, and E 2 transitions among excited states, would be ideal information to constrain theoretical models of the 199Hg Schiff moment. The high level density of 199Hg makes those determinations challenging, however similar information can be obtained from exploring surrounding even-even Hg isotopes. As part of a campaign to study the 198,200Hg isotopes, a number of experiments have been performed using the Q3D spectrograph at the Maier-Leibnitz Laboratory, with 22 MeV deuteron beams impinging on enriched Hg32S targets. Inelastic scattering allows us to probe the desired E 2 and E 3 matrix elements, while the 198Hg (d , p) and 200Hg (d , t) reactions provide information on the neutron single-particle states of 199Hg.

  8. Nuclear Volume Effects in Equilibrium Stable Isotope Fractionations of Hg, Tl and Pb Isotope Systems

    NASA Astrophysics Data System (ADS)

    Yang, S.; Liu, Y.

    2014-12-01

    Many evidences showed that heavy isotope systems could be significantly fractionated as the consequence of the nuclear volume effect (NVE) or so-called nuclear field shift effect. Here we investigate NVEs of Hg, Tl and Pb isotope systems by using quantum chemistry computational methods with careful evaluation on quantum relativistic effects via the Dirac's formalism of full-electron wavefunction. Our results generally agree with previous studies but with noticeable differences in many cases. With the unique NVE driving force, equilibrium 202Hg/198Hg and 205Tl/203Tl isotopes can be fractionated up to 3.94‰ and 2.78‰ at 0℃, respectively, showing potentially large equilibrium isotope fractionations can be expected for future studies of these two isotope systems. Moreover, the NVE causes large mass-independent fractionations (MIF) for odd-mass isotopes (e.g., ∆199NVHg and ∆201NVHg) and small MIFs for even-mass isotopes (e.g., ∆200NVHg). For Pb isotope system, NVEs induce isotope fractionations up to 1.62‰ (207Pb/206Pb) and 4.06‰ (208Pb/206Pb) at 0℃. However, contributions from classical mass-dependent driving force are small, about 0.1-0.5‰ for 207Pb/206Pb and 0.2-0.9‰ for 208Pb/206Pb. We find that Pb4+-bearing species can be significantly enriched heavy isotopes than Pb2+-bearing species. Comparing to Pb0, Pb2+-bearing species even enrich lighter Pb isotopes. A very strange and interesting thing is that the beta value of Pb2+-bearing species can be smaller than the unity (1.000). Similar thing has been found on Tl+-bearing species. This is an impossible and unexplained situation if only based on classical mass-dependent isotope fractionation theory (e.g., Bigeleisen-Mayer equation). The consequence is that the different direction of beta values of Pb2+-bearing species will let the Pb isotope fractionation even larger when they fractionate with Pb4+-bearing species. Moreover, NVEs also cause mass-independent fractionation (MIF) of odd 207Pb

  9. Mercury isotope signatures as tracers for Hg cycling at the New Idria Hg mine.

    PubMed

    Wiederhold, Jan G; Smith, Robin S; Siebner, Hagar; Jew, Adam D; Brown, Gordon E; Bourdon, Bernard; Kretzschmar, Ruben

    2013-06-18

    Mass-dependent fractionation (MDF) and mass-independent fractionation (MIF) of Hg isotopes provides a new tool for tracing Hg in contaminated environments such as mining sites, which represent major point sources of Hg pollution into surrounding ecosystems. Here, we present Hg isotope ratios of unroasted ore waste, calcine (roasted ore), and poplar leaves collected at a closed Hg mine (New Idria, CA, U.S.A.). Unroasted ore waste was isotopically uniform with δ(202)Hg values from -0.09 to 0.16‰ (± 0.10‰, 2 SD), close to the estimated initial composition of the HgS ore (-0.26‰). In contrast, calcine samples exhibited variable δ(202)Hg values ranging from -1.91‰ to +2.10‰. Small MIF signatures in the calcine were consistent with nuclear volume fractionation of Hg isotopes during or after the roasting process. The poplar leaves exhibited negative MDF (-3.18 to -1.22‰) and small positive MIF values (Δ(199)Hg of 0.02 to 0.21‰). Sequential extractions combined with Hg isotope analysis revealed higher δ(202)Hg values for the more soluble Hg pools in calcines compared with residual HgS phases. Our data provide novel insights into possible in situ transformations of Hg phases and suggest that isotopically heavy secondary Hg phases were formed in the calcine, which will influence the isotope composition of Hg leached from the site. PMID:23662941

  10. Mercury isotope fractionation during precipitation of metacinnabar (β-HgS) and montroydite (HgO).

    PubMed

    Smith, Robin S; Wiederhold, Jan G; Kretzschmar, Ruben

    2015-04-01

    To utilize stable Hg isotopes as a tracer for Hg cycling and pollution sources in the environment, it is imperative that fractionation factors for important biogeochemical processes involving Hg are determined. Here, we report experimental results on Hg isotope fractionation during precipitation of metacinnabar (β-HgS) and montroydite (HgO). In both systems, we observed mass-dependent enrichments of light Hg isotopes in the precipitates relative to the dissolved Hg. Precipitation of β-HgS appeared to follow equilibrium isotope fractionation with an enrichment factor ε(202)Hg(precipitate-supernatant) of -0.63‰. Precipitation of HgO resulted in kinetic isotope fractionation, which was described by a Rayleigh model with an enrichment factor of -0.32‰. Small mass-independent fractionation was observed in the HgS system, presumably related to nuclear volume fractionation. We propose that Hg isotope fractionation in the HgS system occurred in solution during the transition of O- to S-coordination of Hg(II), consistent with theoretical predictions. In the HgO system, fractionation was presumably caused by the faster precipitation of light Hg isotopes, and no isotopic exchange between solid and solution was observed on the timescale investigated. The results of this work emphasize the importance of Hg solution speciation and suggest that bonding partners of Hg in solution complexes may control the overall isotope fractionation. The determined fractionation factor and mechanistic insights will have implications for the interpretation of Hg isotope signatures and their use as an environmental tracer. PMID:25782104

  11. Isotopic Hg in an Allende carbon-rich residue

    NASA Technical Reports Server (NTRS)

    Reed, G. W., Jr.; Jovanovic, S.

    1990-01-01

    A carbon-rich residue from Allende subjected to stepwise heating yielded two isotopically resolvable types of Hg: one with an (Hg-196)/(Hg-202) concentration ratio the same as terrestrial (monitor) Hg; the other enriched in Hg-196 relative to Hg-202 by about 60 percent. Hg with the 202 isotope enriched relative to 196, as is found in bulk Allende, was not observed. Whether the result of mass fractionation or nucleosynthesis, the distinct types of Hg entered different carrier phases and were not thermally mobilized since the accretion of the Allende parent body.

  12. Unique Hg stable isotope signatures of compact fluorescent lamp-sourced Hg.

    PubMed

    Mead, Chris; Lyons, James R; Johnson, Thomas M; Anbar, Ariel D

    2013-03-19

    The recent widespread adoption of compact fluorescent lamps (CFL) has increased their importance as a source of environmental Hg. Stable isotope analysis can identify the sources of environmental Hg, but the isotopic composition of Hg from CFL is not yet known. Results from analyses of CFL with a range of hours of use show that the Hg they contain is isotopically fractionated in a unique pattern during normal CFL operation. This fractionation is large by comparison to other known fractionating processes for Hg and has a distinctive, mass-independent signature, such that CFL Hg could be uniquely identified from other sources. The fractionation process described here may also explain anomalous fractionation of Hg isotopes in precipitation. PMID:23373764

  13. Experimental Identification of Intruder Bandheads in Odd-Mass {sup 187-193}Pb

    SciTech Connect

    A.N. Andreyev; J.F.C. Cocks; O. Dorvaux; K. Eskola; P. Greenlees; P. Jones; R. Julin; S. Juutinen; K. Helariutta; M. Huyse; H. Kettunen; P. Kuusiniemi; M. Leino; M. Muikku; W.H. Trzaska; K. Van de Vel; P. Van Duppen; R. Wyss

    1999-12-31

    Fine-structure {alpha}-decays of the odd mass {sup 191-197}Po identifying proton based intruder states in the daughter lead nuclei have been observed, leading to a systematics of intruder states in odd mass lead isotopes from {sup 197}Pb down to {sup 187}Pb. The interpretation of these states involves the coupling of the i{sub 13/2} or p{sub 3/2} odd neutron to the oblate deformed even lead core.

  14. Experimental identification of intruder bandheads in odd-mass {sup 187-193}Pb

    SciTech Connect

    Andreyev, A. N.; Huyse, M.; Van de Vel, K.; Van Duppen, P.; Cocks, J. F. C.; Dorvaux, O.; Greenlees, P.; Jones, P.; Julin, R.; Juutinen, S.; Helariutta, K.; Kettunen, H.; Kuusiniemi, P.; Leino, M.; Muikku, M.; Trzaska, W. H.; Eskola, K.; Wyss, R.

    1999-11-16

    Fine-structure {alpha}-decays of the odd mass {sup 191-197}Po identifying proton based intruder states in the daughter lead nuclei have been observed, leading to a systematics of intruder states in odd mass lead isotopes from {sup 197}Pb down to {sup 187}Pb. The interpretation of these states involves the coupling of the i{sub 13/2} or p{sub 3/2} odd neutron to the oblate deformed even lead core.

  15. Mass Independent Fractionation of Hg Isotopes Preserved in the Precambrian

    NASA Astrophysics Data System (ADS)

    Thibodeau, A. M.; Bergquist, B. A.; Kah, L. C.; Ono, S.; Ghosh, S.; Hazen, R. M.

    2013-12-01

    Mercury (Hg) is a photochemically active, redox-sensitive, chalcophilic metal with complex biogeochemistry that displays a wide range of mass-dependent (MDF) and mass-independent (MIF) stable isotopic fractionation. In the past decade, Hg isotopes have emerged as important tracers of both the sources and cycling of Hg in the modern environment. However, their utility as environmental proxies in ancient rocks remains largely unexplored. The potential of Hg isotopes to inform Precambrian environments derives from the observation that Hg isotopes with odd atomic mass numbers (199Hg and 201Hg) undergo large MIF by the magnetic isotope effect (MIE) and smaller MIF through the nuclear volume effect (NVE). Small MIF produced via NVE has been observed for numerous transformations and is characterized by MIF ratios (Δ199Hg/Δ201Hg) of about 1.6. Large Hg-MIF driven by MIE has been observed during photochemical transformations and is characterized by Δ199Hg/Δ201Hg ratios between 1 and 1.3. This MIF signal is sensitive to a range of environmental conditions, including the amount and type of solar radiation, the presence and type of complexing organic ligands, and the Hg/dissolved organic carbon (DOC) ratio. Thus, it is hoped that Hg-MIF signals may indirectly record changes in atmospheric composition or seawater chemistry if preserved in marine sedimentary records. Previous work has clearly demonstrated that Hg-MIF signals are preserved in Archean and Paleoproterozoic marine shales and massive sulfide deposits. Here, we present evidence that such signals are also preserved in marine shales of mid-Proterozoic age, including the ~1.3 Ga Sulky formation (Dismal Lakes Group, NW Arctic), the ~1.45 Ga Greyson Shale (Belt Basin, Montana), and the ~1.5 Ga Katalsy formation (Kypry Group, Eastern European Platform). We observe that the Greyson shale and shales within the Sulky formation yield negative Hg-MIF with Δ199Hg/Δ201Hg ratios close to 1 and that Kaltasy group sediments

  16. Pathways of CH3Hg and Hg Ingestion in Benthic Organisms: An Enriched Isotope Approach

    PubMed Central

    2015-01-01

    Mercury is a widespread contaminant in marine food webs, and identifying uptake pathways of mercury species, CH3Hg+ and Hg2+, into low trophic level organisms is important to understanding its entry into marine food webs. Enriched stable isotope tracers were used to study benthic vs. pelagic pathways of CH3Hg+ and Hg2+ uptake via food to the infaunal estuarine amphipod, Leptocheirus plumulosus. Algal cells differentially labeled with isotopically enriched CH3Hg+ or Hg2+ were added simultaneously to the sediment and water column of microcosms, and Hg species were monitored in amphipods and in sediment and water compartments. Methylation of Hg2+ occurred during the course of the experiment, enhancing the uptake of Hg2+ spikes. Trophic transfer of Hg from algae added to the water column was determined to be the major uptake route for amphipods, suggesting inputs of contaminated organic matter from the pelagic zone are important to mercury bioaccumulation even in organisms living in sediments. PMID:24678910

  17. Mercury Isotopes in Earth and Environmental Sciences

    NASA Astrophysics Data System (ADS)

    Blum, Joel D.; Sherman, Laura S.; Johnson, Marcus W.

    2014-05-01

    Virtually all biotic, dark abiotic, and photochemical transformations of mercury (Hg) produce Hg isotope fractionation, which can be either mass dependent (MDF) or mass independent (MIF). The largest range in MDF is observed among geological materials and rainfall impacted by anthropogenic sources. The largest positive MIF of Hg isotopes (odd-mass excess) is caused by photochemical degradation of methylmercury in water. This signature is retained through the food web and measured in all freshwater and marine fish. The largest negative MIF of Hg isotopes (odd-mass deficit) is caused by photochemical reduction of inorganic Hg and has been observed in Arctic snow and plant foliage. Ratios of MDF to MIF and ratios of 199Hg MIF to 201Hg MIF are often diagnostic of biogeochemical reaction pathways. More than a decade of research demonstrates that Hg isotopes can be used to trace sources, biogeochemical cycling, and reactions involving Hg in the environment.

  18. Stable Hg isotope signatures in creek sediments impacted by a former Hg mine.

    PubMed

    Smith, Robin S; Wiederhold, Jan G; Jew, Adam D; Brown, Gordon E; Bourdon, Bernard; Kretzschmar, Ruben

    2015-01-20

    The goal of this study was to investigate the Hg stable isotope signatures of sediments in San Carlos Creek downstream of the former Hg mine New Idria, CA, USA and to relate the results to previously studied Hg isotope signatures of unroasted ore waste and calcine materials in the mining area. New Idria unroasted ore waste was reported to have a narrow δ(202)Hg range (−0.09 to 0.16‰), while roasted calcine materials exhibited a very large variability in δ(202)Hg (−5.96 to 14.5‰). In this study, creek sediment samples were collected in the stream bed from two depths (0–10 and 10–20 cm) at 10 locations between the mine adit and 28 km downstream. The sediment samples were size-fractionated into sand, silt, and (if possible) clay fractions as well as hand-picked calcine pebbles. The sediment samples contained highly elevated Hg concentrations (8.2 to 647 μg g(–1)) and displayed relatively narrow mass-dependent fractionation (MDF, δ(202)Hg; ± 0.08‰, 2SD) ranges (−0.58 to 0.24‰) and little to no mass-independent fractionation (MIF, Δ(199)Hg; ± 0.04‰, 2SD) (0.00 to 0.10‰), similar to what was observed previously for the unroasted ore waste. However, due to the highly variable and overlapping δ(202)Hg signatures of the calcines, they could not be ruled out as source of Hg to the creek sediments. Overall, our results suggest that analyzing creek sediments downstream of former Hg mines can provide a more reliable Hg isotope source signature for tracing studies at larger spatial scales, than analyzing the isotopically highly heterogeneous tailing piles typically found at former mining sites. Creek sediments carry an integrated isotope signature of Hg transported away from the mine with runoff into the creek, eventually affecting ecosystems downstream. PMID:25489982

  19. Mass Dependent and Mass Independent Fractionation of Hg Isotopes and Estimation of Photochemical Loss of Hg in Aquatic Systems

    NASA Astrophysics Data System (ADS)

    Bergquist, B. A.; Blum, J. D.

    2007-12-01

    Mercury is a globally distributed and highly toxic pollutant, the mobility and bioaccumulation of which is dependent on its redox cycling. Hg isotope analysis is an important new tool for identifying Hg sources and tracking Hg transformations in the environment. Most natural samples analyzed for Hg isotopes display mass-dependent isotope fractionation (MDF), but a small body of data suggests that some natural samples also display mass- independent isotope fractionation (MIF) of the odd Hg isotopes. Here we document MIF of Hg isotopes during an important natural process, constrain the potential mechanism of isotope fractionation, and apply the MIF observed in natural samples to quantify the photochemical reduction of Hg species in the environment. Reduction of Hg species to Hg0 vapor is an important pathway for removal of Hg from aqueous systems into the atmosphere and occurs by abiotic and biotic mechanisms. In laboratory experiments, we find that photochemical reduction Hg species by natural sunlight leads to large MIF of the odd isotopes. Also, the relationship between MIF for the two odd isotopes of Hg is significantly different for different photo-reduction pathways. In contrast, both biological reduction (Kritee et al., 2006) and dark abiotic organically-mediated reduction follow MDF. Natural samples from aquatic ecosystems preserve both MDF and MIF. In fish, MDF increases with the size and Hg concentration of fish suggesting MDF may be useful in understanding Hg bioaccumulation. Fish also display a large range in MIF (4‰), and the relationship between the MIF of the two odd isotopes in fish has a similar slope to the slope found for photo-reduction of CH3Hg+. Since fish bioaccumulate CH3Hg+, fish may be recording the extent to which CH3Hg+ is lost via photochemical reduction in an aquatic ecosystem. Fish populations from different locations have different MIF values, but mostly display similar MIF within a given locale. This suggests that MIF is preserved

  20. Hg Isotope Ratios of a Sediment Core from Plastic Lake, Ontario: Implications for Hg Cycle in Aquatic Environment

    NASA Astrophysics Data System (ADS)

    Xie, Q.; Dillon, P.; Evans, D.; Lu, S.

    2004-12-01

    Hg isotope ratios in a sediment core obtained in Plastic Lake, Ontario, Canada, have been measured by coupling a gold trap with an MC-ICP-MS. The core is about 30 cm in depth and corresponds to a time period of about 250 years, based on 210Pb dating. The samples were combusted at high temperature and the Hg collected onto a gold trap. The gold trap was subsequently heated to release Hg directly into the MC-ICP-MS. An in-house sample introduction system was employed to extend Hg signal duration in order to obtain high precision in isotope ratio measurement. The instrumental mass bias was corrected using Tl introduced simultaneously via an Aridus membrane desolvation nebulizer. Based on long term measurement of a NIST-2225 elemental Hg standard (over 120 measurements since Oct. 2002), the external reproducibility ranges from 45 ppm for 201Hg/202Hg to 100 ppm for 199Hg/202Hg (2 sigma relative standard error). Hg in the sediments shows an increase in light isotope enrichment at about 10 cm depth. The total Hg also displays an increase at the same depth. The depth corresponds to approximately the 1920s, a time period when there was a major increase in coal-burning power generation. Limited Hg isotope data for other terrestrial samples appears to indicate that Hg bound to organic carbon is enriched in light isotopes relative to elemental Hg. For example, the DOLT-3, a dogfish liver standard reference material with half of its Hg as MeHg, has the lightest Hg isotope composition among measured terrestrial samples. It is not clear at this stage whether the increase in total Hg and light Hg isotope enrichment in recent years represent a change in methylation rate of the lake, or an increase in atmospheric deposition of Hg combined with a change in source. Discussions based on available Hg isotope data of terrestrial samples together with other chemical data for the lake will be presented.

  1. The Abundance and Isotopic Composition of Hg in Extraterrestrial Materials

    NASA Technical Reports Server (NTRS)

    Lauretta, D. S.

    2004-01-01

    During the past three year grant period we made excellent progress in our study of the abundances and isotopic compositions of Hg and other volatile trace elements in extraterrestrial materials. As part of my startup package I received funds to construct a state-of-the-art experimental facility to study gas-solid reaction kinetics. Much of our effort was spent developing the methodology to measure the abundance and isotopic composition of Hg at ultratrace levels in solid materials. In our first study, the abundance and isotopic composition of Hg was determined in bulk samples of the Murchison (CM) and Allende (CV) carbonaceous chondrites. We have continued our study of mercury in primitive meteorites and expanded the suite of meteorites to include other members of the CM and CV chondrite group as well as CI and CO chondrites. Samples of the CI chondrite Orgueil, the CM chondrites Murray, Nogoya, and Cold Bokkeveld, the CO chondrites Kainsaz, Omans, and Isna, and the CV chondrites Vigarano, Mokoia, and Grosnaja were tested. We have developed a thermal analysis ICP-MS technique and applied it to the study of a suite of thermally labile elements (Zn, As, Se, Cd, In, Sn, Sb, Te, Hg, Au, Tl, Pb, and Bi) in geologic materials as well.

  2. Mass distributions for induced fission of different Hg isotopes

    NASA Astrophysics Data System (ADS)

    Andreev, A. V.; Adamian, G. G.; Antonenko, N. V.

    2012-10-01

    With the improved scission-point model mass distributions are calculated for induced fission of different Hg isotopes with even mass numbers A=180, 184, 188, 192, 196, and 198. The calculated mass distribution and mean total kinetic energy of fission fragments are in good agreement with the existing experimental data. The asymmetric mass distribution of fission fragments of 180Hg observed in the recent experiment is explained. The change in the shape of the mass distribution from asymmetric to more symmetric is revealed with increasing A of the fissioning AHg nucleus, and reactions are proposed to verify this prediction experimentally.

  3. Investigation of uptake and retention of atmospheric Hg(II) by boreal forest plants using stable Hg isotopes

    USGS Publications Warehouse

    Graydon, J.A.; St. Louis, V.L.; Hintelmann, H.; Lindberg, S.E.; Sandilands, K.A.; Rudd, J.W.M.; Kelly, C.A.; Tate, M.T.; Krabbenhoft, D.P.; Lehnherr, I.

    2009-01-01

    Although there is now a general consensus among mercury (Hg) biogeochemists that increased atmospheric inputs of inorganic Hg(II) to lakes and watersheds can result in increased methylmercury (MeHg) concentrations in fish, researchers still lack kinetic data describing the movement of Hg from the atmosphere, through watershed and lake ecosystems, and into fish. The use of isotopically enriched Hg species in environmental studies now allows experimentally applied new Hg to be distinguished from ambient Hg naturally present in the system. Four different enriched stable Hg(II) isotope "spikes" were applied sequentially over four years to the ground vegetation of a microcatchment at the Experimental Lakes Area (ELA) in the remote boreal forest of Canada to examine retention of Hg(II) following deposition. Areal masses of the spikes and ambient THg (all forms of Hg in a sample) were monitored for eight years, and the pattern of spike retention was used to estimate retention of newly deposited ambient Hg within the ground vegetation pool. Fifty to eighty percent of applied spike Hg was initially retained by ground vegetation. The areal mass of spike Hg declined exponentially over time and was best described by a first-order process with constants (k) ranging between 9.7 ?? 10-4 day -1 and 11.6 ?? 10-4 day-1. Average half-life (t1/2) of spike Hg within the ground vegetation pool (??S.D.) was 704 ?? 52 days. This retention of new atmospheric Hg(II) by vegetation delays movement of new Hg(II) into soil, runoff, and finally into adjacent lakes. Ground-applied Hg(II) spikes were not detected in tree foliage and litterfall, indicating that stomatal and/or root uptake of previously deposited Hg (i.e., "recycled" from ground vegetation or soil Hg pools) were likely not large sources of foliar Hg under these experimental conditions. ?? 2009 American Chemical Society.

  4. Isotopic Composition of Gaseous Elemental Mercury (Hg0) at Various Sites in Japan

    NASA Astrophysics Data System (ADS)

    Yamakawa, A.; Moriya, K.; Yoshinaga, J.

    2015-12-01

    Mercury (Hg) is a toxic heavy metal, which exists in various chemical forms in the environmental system. In the atmosphere, Hg exists in three forms (Hg0(g), Hg+2(g), and Hg(p)). Hg0(g) is the dominant species of atmospheric Hg, accounting for >95% of the total Hg in the atmosphere. Because Hg0(g) is highly volatile and has limited solubility in water, it cannot be easily removed by wet or dry deposition processes. Therefore, the residence time of Hg0(g) in the atmosphere is relatively long (1 to 2 years), allowing long-range transport from mercury emission source(s). Conversely, Hg+2(g) and Hg(p) are effectively removed from the atmosphere through wet and dry depositions. The determination of mercury source attribution using quantitative data is challenging because Hg0(g) may be deposited on an area upon oxidation to Hg+2(g) and associated with aerosols and particulates to form Hg(p) while the global cycling of Hg0(g). Over the last decade, the development of analytical methods of highly precise Hg isotopic measurements demonstrated mass-dependent fractionation (MDF) and mass-independent fractionation (MIF) of Hg isotopes in environmental samples. For instance, MDF of Hg isotopes is thought to occur during various natural and industrial Hg transformations. MIF of Hg isotopes is observed during abiotic reduction, photochemical and non-photochemical, and physical and chemical processes. Such processes lead to differences in the Hg isotopic composition of different emission sources, both natural and anthropogenic, and atmospheric processes (i.e., transportation, oxidation/reduction, deposition, and reemission). Therefore, Hg isotopic compositions could be used to trace the sources and processes of atmospheric Hg. For securing the reliability and accuracy of atmospheric Hg isotope data, the methods of collection, pretreatment, and isotopic measurement for Hg0(g) were developed to obtain high recovery yield of samples with no Hg isotopic fractionation during each

  5. Isospin dependence of mass-distribution shape of fission fragments of Hg isotopes

    NASA Astrophysics Data System (ADS)

    Andreev, A. V.; Adamian, G. G.; Antonenko, N. V.; Andreyev, A. N.

    2013-10-01

    Using an improved scission-point model, the mass distributions are calculated for induced fission of even Hg isotopes with mass numbers A=174to196. With increasing A of a fissioning AHg nucleus the mass distribution evolves from symmetric for 174Hg, to asymmetric for isotopes close to 180Hg, and back to more symmetric for 192,194,196Hg. In the fissioning Hg isotopes their excitation energy weakly influences the shape of the mass distribution. In 180,184Hg, the mass distributions of fission fragments remain asymmetric even at high excitation energies.

  6. The Abundance and Isotopic Composition of Hg in Extraterrestrial Materials

    NASA Technical Reports Server (NTRS)

    Blum, J. D.; Klaue, Bjorn

    2005-01-01

    During the three year grant period we made excellent progress in our study of the abundances and isotopic compositions of Hg and other volatile trace elements in extraterrestrial materials. At the time the grant started, our collaborating PI, Dante Lauretts, was a postdoctoral research associate working with Peter Buseck at Arizona State University. The work on chondritic Hg was done in collaboration with Dante Lauretta and Peter Buseck and this study was published in Lauretta et a1 (2001a). In July, 2001 Dante Lauretta accepted a position as an Assistant Professor in the Lunar and Planetary Laboratory at the University of Arizona. His funding was transferred and this grant has supported much of his research activities during his first two years at the U of A. Several other papers are in preparation and will be published soon. We presented papers on this topic at Goldschmidt Conferences, the Lunar and Planetary Science Conferences, and the Annual Meetings of the Meteoritical Society. The work done under this grant has spurred several new directions of inquiry, which we are still pursuing. Included in this paper are the studies of bulk abundances and isotopic compositions of metreoritic Mercury, and the development of a thermal analysis ICP-MS technique applied to thermally liable elements.

  7. Study of nuclear structure of odd mass 119-127I nuclei in a phenomenological approach

    NASA Astrophysics Data System (ADS)

    Singh, Dhanvir; Gupta, Anuradha; Kumar, Amit; Sharma, Chetan; Singh, Suram; Bharti, Arun; Khosa, S. K.; Bhat, G. H.; Sheikh, J. A.

    2016-08-01

    By using the phenomenological approach of Projected Shell Model (PSM), the positive and negative-parity band structures of odd mass neutron-rich 119-127I nuclei have been studied with the deformed single-particle states generated by the standard Nilsson potential. For these isotopes, the band structures have been analyzed in terms of quasi-particles configurations. The phenomenon of backbending in moment of inertia is also studied in the present work. Besides this, the reduced transition probabilities, i.e. B (E 2) and B (M 1), are obtained from the PSM wavefunction for the first time for yrast bands of these isotopes.

  8. Dipole strength distributions of the stable odd-mass N=82 isotones {sup 139}La and {sup 141}Pr

    SciTech Connect

    Scheck, M.; Brentano, P. von; Fransen, C.; Linnemann, A.; Muecher, D.; Pietralla, N.; Scholl, C.; Werner, V.; Kneissl, U.; Kohstall, C.; Pitz, H. H.; Stedile, F.; Walter, S.; Yates, S. W.

    2007-04-15

    The low-lying dipole strength distributions of the odd-mass isotopes {sup 139}La and {sup 141}Pr were studied in nuclear resonance fluorescence experiments using bremsstrahlung beams. Excited states were observed at excitation energies up to 4 MeV. Spectroscopic information was obtained on excitation energies, decay widths, decay branching ratios, and transition probabilities. The states belonging to the [[2{sup +}(multiply-in-circle sign)3{sup -}](multiply-in-circle sign)particle/hole] coupling were a special focus, and the results are compared with other stable odd-mass nuclei at or near the N=82 shell closure.

  9. Mercury deposition and re-emission pathways in boreal forest soils investigated with Hg isotope signatures.

    PubMed

    Jiskra, Martin; Wiederhold, Jan G; Skyllberg, Ulf; Kronberg, Rose-Marie; Hajdas, Irka; Kretzschmar, Ruben

    2015-06-16

    Soils comprise the largest terrestrial mercury (Hg) pool in exchange with the atmosphere. To predict how anthropogenic emissions affect global Hg cycling and eventually human Hg exposure, it is crucial to understand Hg deposition and re-emission of legacy Hg from soils. However, assessing Hg deposition and re-emission pathways remains difficult because of an insufficient understanding of the governing processes. We measured Hg stable isotope signatures of radiocarbon-dated boreal forest soils and modeled atmospheric Hg deposition and re-emission pathways and fluxes using a combined source and process tracing approach. Our results suggest that Hg in the soils was dominantly derived from deposition of litter (∼90% on average). The remaining fraction was attributed to precipitation-derived Hg, which showed increasing contributions in older, deeper soil horizons (up to 27%) indicative of an accumulation over decades. We provide evidence for significant Hg re-emission from organic soil horizons most likely caused by nonphotochemical abiotic reduction by natural organic matter, a process previously not observed unambiguously in nature. Our data suggest that Histosols (peat soils), which exhibit at least seasonally water-saturated conditions, have re-emitted up to one-third of previously deposited Hg back to the atmosphere. Re-emission of legacy Hg following reduction by natural organic matter may therefore be an important pathway to be considered in global models, further supporting the need for a process-based assessment of land/atmosphere Hg exchange. PMID:25946594

  10. Influence of shell effects on mass asymmetry in fission of different Hg isotopes

    NASA Astrophysics Data System (ADS)

    Andreev, A. V.; Adamian, G. G.; Antonenko, N. V.

    2013-12-01

    With the improved scission-point model mass distributions are calculated for induced fission of Hg isotopes with even mass numbers A = 174 - 198. The calculated mass distributions and mean total kinetic energy of fission fragments are in good agreement with the existing experimental data. The asymmetric mass distribution of fission fragments of 180Hg observed in the recent experiment is explained. The change in the shape of the mass distribution with increasing A of the fissioning AHg nucleus from symmetric for 174Hg to asymmetric around 180Hg, and to more symmetric for 192-198Hg is revealed.

  11. Neutron-proton pairing correlations in odd mass systems

    SciTech Connect

    Fellah, M. Allal, N. H.; Oudih, M. R.

    2015-03-30

    An expression of the ground-state which describes odd mass systems within the BCS approach in the isovector neutron-proton pairing case is proposed using the blocked level technique. The gap equations as well as the energy expression are then derived. It is shown that they exactly generalize the expressions obtained in the pairing between like-particles case. The various gap parameters and the energy are then numerically studied as a function of the pairing-strength within the schematic one-level model.

  12. Nested reactor chamber and operation for Hg-196 isotope separation process

    DOEpatents

    Grossman, M.W.

    1991-10-08

    The present invention is directed to an apparatus for use in [sup 196]Hg separation and its method of operation. Specifically, the present invention is directed to a nested reactor chamber useful for [sup 196]Hg isotope separation reactions avoiding the photon starved condition commonly encountered in coaxial reactor systems. 6 figures.

  13. Nested reactor chamber and operation for Hg-196 isotope separation process

    DOEpatents

    Grossman, Mark W.

    1991-01-01

    The present invention is directed to an apparatus for use in .sup.196 Hg separation and its method of operation. Specifically, the present invention is directed to a nested reactor chamber useful for .sup.196 Hg isotope separation reactions avoiding the photon starved condition commonly encountered in coaxial reactor systems.

  14. Natural Hg isotopic composition of different Hg compounds in mammal tissues as a proxy for in vivo breakdown of toxic methylmercury.

    PubMed

    Perrot, Vincent; Masbou, Jeremy; Pastukhov, Mikhail V; Epov, Vladimir N; Point, David; Bérail, Sylvain; Becker, Paul R; Sonke, Jeroen E; Amouroux, David

    2016-02-01

    In the last decade, specific attention has been paid to total mercury (HgT) stable isotopic composition, especially in natural samples such as aquatic organisms, due to its potential to track the cycle of this toxic element in the environment. Here, we investigated Hg Compound Specific stable Isotopic Composition (CSIC) of natural inorganic Hg (iHg) and methylmercury (MMHg) in various tissues of aquatic mammals (Beluga whale from the Arctic marine environment and seals from the freshwater lake Baikal, Russia). In seals' organs the variation in mass dependent fractionation (MDF, δ(202)Hg) for total Hg was significantly correlated to the respective fraction of iHg and MMHg compounds, with MMHg being enriched by ∼ 3‰ in heavier isotopes relative to iHg. On the other hand, we observe insignificant variation in Hg mass independent isotope fractionation (MIF, Δ(199)Hg) among iHg and MMHg in all organs for the same mammal species and MMHg in prey items. MIF signatures suggest that both MMHg and iHg in aquatic mammals have the same origin (i.e., MMHg from food), and are representative of Hg photochemistry in the water column of the mammal ecosystem. MDF signatures of Hg compounds indicate that MMHg is demethylated in vivo before being stored in the muscle, and the iHg formed is stored in the liver, and to a lesser extent in the kidney, before excretion. Thus, Hg CSIC analysis in mammals can be a powerful tool for tracing the metabolic response to Hg exposure. PMID:26680232

  15. Identifying the sources and processes of mercury in subtropical estuarine and ocean sediments using Hg isotopic composition.

    PubMed

    Yin, Runsheng; Feng, Xinbin; Chen, Baowei; Zhang, Junjun; Wang, Wenxiong; Li, Xiangdong

    2015-02-01

    The concentrations and isotopic compositions of mercury (Hg) in surface sediments of the Pearl River Estuary (PRE) and the South China Sea (SCS) were analyzed. The data revealed significant differences between the total Hg (THg) in fine-grained sediments collected from the PRE (8-251 μg kg(-1)) and those collected from the SCS (12-83 μg kg(-1)). Large spatial variations in Hg isotopic compositions were observed in the SCS (δ(202)Hg, from -2.82 to -2.10‰; Δ(199)Hg, from +0.21 to +0.45‰) and PRE (δ(202)Hg, from -2.80 to -0.68‰; Δ(199)Hg, from -0.15 to +0.16‰). The large positive Δ(199)Hg in the SCS indicated that a fraction of Hg has undergone Hg(2+) photoreduction processes prior to incorporation into the sediments. The relatively negative Δ(199)Hg values in the PRE indicated that photoreduction of Hg is not the primary route for the removal of Hg from the water column. The riverine input of fine particles played an important role in transporting Hg to the PRE sediments. In the deep ocean bed of the SCS, source-related signatures of Hg isotopes may have been altered by natural geochemical processes (e.g., Hg(2+) photoreduction and preferential adsorption processes). Using Hg isotope compositions, we estimate that river deliveries of Hg from industrial and urban sources and natural soils could be the main inputs of Hg to the PRE. However, the use of Hg isotopes as tracers in source attribution could be limited because of the isotope fractionation by natural processes in the SCS. PMID:25565343

  16. Food preferences and Hg distribution in Chelonia mydas assessed by stable isotopes.

    PubMed

    Bezerra, M F; Lacerda, L D; Rezende, C E; Franco, M A L; Almeida, M G; Macêdo, G R; Pires, T T; Rostán, G; Lopez, G G

    2015-11-01

    Mercury (Hg) is a highly toxic pollutant that poses in risk several marine animals, including green turtles (Chelonia mydas). Green turtles are globally endangered sea turtle species that occurs in Brazilian coastal waters as a number of life stage classes (i.e., foraging juveniles and nesting adults). We assessed total Hg concentrations and isotopic signatures ((13)C and (15)N) in muscle, kidney, liver and scute of juvenile green turtles and their food items from two foraging grounds with different urban and industrial development. We found similar food preferences in specimens from both areas but variable Hg levels in tissues reflecting the influence of local Hg backgrounds in food items. Some juvenile green turtles from the highly industrialized foraging ground presented liver Hg levels among the highest ever reported for this species. Our results suggest that juvenile foraging green turtles are exposed to Hg burdens from locally anthropogenic activities in coastal areas. PMID:26196313

  17. Beyond-mean-field boson-fermion model for odd-mass nuclei

    NASA Astrophysics Data System (ADS)

    Nomura, K.; Nikšić, T.; Vretenar, D.

    2016-05-01

    A novel method for calculating spectroscopic properties of medium-mass and heavy atomic nuclei with an odd number of nucleons is introduced, based on the framework of nuclear energy density functional theory and the particle-core coupling scheme. The deformation energy surface of the even-even core, as well as the spherical single-particle energies and occupation probabilities of the odd particle(s), are obtained in a self-consistent mean-field calculation determined by the choice of the energy density functional and pairing interaction. This method uniquely determines the parameters of the Hamiltonian of the boson core, and only the strength of the particle-core coupling is specifically adjusted to selected data for a particular nucleus. The approach is illustrated in a systematic study of low-energy excitation spectra and transition rates of axially deformed odd-mass Eu isotopes.

  18. Beyond mean-field calculations for odd-mass nuclei.

    PubMed

    Bally, B; Avez, B; Bender, M; Heenen, P-H

    2014-10-17

    Beyond mean-field methods are very successful tools for the description of large-amplitude collective motion for even-even atomic nuclei. The state-of-the-art framework of these methods consists in a generator coordinate method based on angular-momentum and particle-number projected triaxially deformed Hartree-Fock-Bogoliubov (HFB) states. The extension of this scheme to odd-mass nuclei is a long-standing challenge. We present for the first time such an extension, where the generator coordinate space is built from self-consistently blocked one-quasiparticle HFB states. One of the key points for this success is that the same Skyrme interaction is used for the mean-field and the pairing channels, thus avoiding problems related to the violation of the Pauli principle. An application to ^{25}Mg illustrates the power of our method, as agreement with experiment is obtained for the spectrum, electromagnetic moments, and transition strengths, for both positive and negative parity states and without the necessity for effective charges or effective moments. Although the effective interaction still requires improvement, our study opens the way to systematically describe odd-A nuclei throughout the nuclear chart. PMID:25361253

  19. Beyond Mean-Field Calculations for Odd-Mass Nuclei

    NASA Astrophysics Data System (ADS)

    Bally, B.; Avez, B.; Bender, M.; Heenen, P.-H.

    2014-10-01

    Beyond mean-field methods are very successful tools for the description of large-amplitude collective motion for even-even atomic nuclei. The state-of-the-art framework of these methods consists in a generator coordinate method based on angular-momentum and particle-number projected triaxially deformed Hartree-Fock-Bogoliubov (HFB) states. The extension of this scheme to odd-mass nuclei is a long-standing challenge. We present for the first time such an extension, where the generator coordinate space is built from self-consistently blocked one-quasiparticle HFB states. One of the key points for this success is that the same Skyrme interaction is used for the mean-field and the pairing channels, thus avoiding problems related to the violation of the Pauli principle. An application to Mg25 illustrates the power of our method, as agreement with experiment is obtained for the spectrum, electromagnetic moments, and transition strengths, for both positive and negative parity states and without the necessity for effective charges or effective moments. Although the effective interaction still requires improvement, our study opens the way to systematically describe odd-A nuclei throughout the nuclear chart.

  20. Study of asymmetric fission yield behavior from neutron-deficient Hg isotope

    SciTech Connect

    Perkasa, Y. S.; Waris, A. Kurniadi, R. Su'ud, Z.

    2014-09-30

    A study of asymmetric fission yield behavior from a neutron-deficient Hg isotope has been conducted. The fission yield calculation of the neutron-deficient Hg isotope using Brownian Metropolis shape had showed unusual result at decreasing energy. In this paper, this interesting feature will be validated by using nine degree of scission shapes parameterization from Brosa model that had been implemented in TALYS nuclear reaction code. This validation is intended to show agreement between both model and the experiment result. The expected result from these models considered to be different due to dynamical properties that implemented in both models.

  1. Mercury (Hg) in meteorites: Variations in abundance, thermal release profile, mass-dependent and mass-independent isotopic fractionation

    NASA Astrophysics Data System (ADS)

    Meier, Matthias M. M.; Cloquet, Christophe; Marty, Bernard

    2016-06-01

    We have measured the concentration, isotopic composition and thermal release profiles of Mercury (Hg) in a suite of meteorites, including both chondrites and achondrites. We find large variations in Hg concentration between different meteorites (ca. 10 ppb to 14,000 ppb), with the highest concentration orders of magnitude above the expected bulk solar system silicates value. From the presence of several different Hg carrier phases in thermal release profiles (150-650 °C), we argue that these variations are unlikely to be mainly due to terrestrial contamination. The Hg abundance of meteorites shows no correlation with petrographic type, or mass-dependent fractionation of Hg isotopes. Most carbonaceous chondrites show mass-independent enrichments in the odd-numbered isotopes 199Hg and 201Hg. We show that the enrichments are not nucleosynthetic, as we do not find corresponding nucleosynthetic deficits of 196Hg. Instead, they can partially be explained by Hg evaporation and redeposition during heating of asteroids from primordial radionuclides and late-stage impact heating. Non-carbonaceous chondrites, most achondrites and the Earth do not show these enrichments in vapor-phase Hg. All meteorites studied here have however isotopically light Hg (δ202Hg = ∼-7 to -1) relative to the Earth's average crustal values, which could suggest that the Earth has lost a significant fraction of its primordial Hg. However, the late accretion of carbonaceous chondritic material on the order of ∼2%, which has been suggested to account for the water, carbon, nitrogen and noble gas inventories of the Earth, can also contribute most or all of the Earth's current Hg budget. In this case, the isotopically heavy Hg of the Earth's crust would have to be the result of isotopic fractionation between surface and deep-Earth reservoirs.

  2. Hg Isotopic Compositions of Chimneys and Pelagic Sediments at Active Submarine Hydrothermal Field in the Okinawa Trough, Japan

    NASA Astrophysics Data System (ADS)

    Takeuchi, A.; Marumo, K.; Tomiyasu, T.; Yamamoto, M.; Komuro, K.

    2012-12-01

    Mercury (Hg) is a globally distributed and highly toxic pollutant in the environment. It is known that a submarine hydrothermal activity is one of the natural processes to emit Hg to marine environment. In order to estimate the degree to which the Hg found in the marine environment is from anthropogenic versus natural sources, it is important to characterize the Hg from the hydrothermal vents. Samples of chimneys and a ~20 cm sediment core, collected by a deep-sea remotely operated vehicle, from Iheya North hydrothermal field in Okinawa Trough, Japan, were analyzed for Hg concentrations and Hg isotopic compositions. Total Hg concentrations of chimneys range between 8.2 and 16.9 mg/kg, whereas seafloor sediment total Hg concentrations are from 3.8 to 34.8 mg/kg. Approximately 0.4 to 1.1 μg/kg of monomethyl Hg (MMHg) was detected in the top 6 cm sediment cores. Hg isotopic compositions (δ202Hg) of chimneys are between -0.30 and -0.96 ‰, whereas δ202Hg values of sediment samples range from -0.85 to -1.60 ‰. Neither chimneys nor sediment samples exhibit the significant mass independent fractionations in Hg isotopes (Δ201Hg > ± 0.10). The chimney δ202Hg values are slightly higher than the δ202Hg values of sediments. This may indicate that the heavier Hg isotopes tend to be incorporated with mercury-bearing sulfides in chimneys, and the lighter isotopes tend to be remained in the hydrothermal fluid and distributed in the surrounding sediments. Also, the sediment samples from the upper portion of cores demonstrate approximately 0.4 - 0.5 ‰ lower δ202Hg values than those from the lower part. This isotopic fractionation may be resulted from a demethylated process of MMHg by microbes. Several studies have previously demonstrated the rapid demethylation of MMHg by microbes in Hg-contaminated aquatic sediments, and range of the isotopic fractionation is similar to that of the experimentally determined isotopic fractionation of MMHg by bacterial reduction

  3. Hg-Cu-Bearing Metal-Sulfide Assemblage in the H3 Chondrite Tieschitz: Important Carriers of Pristine Hg and Possibly Cd-Isotopic Signatures in the Early Solar System

    NASA Astrophysics Data System (ADS)

    Caillet-Komorowski, C.; El Goresy, A.; Miyahara, M.; Boudouma, O.; Ma, C.

    2012-09-01

    The study of a unique assemblage consisting of metallic Hg, HgS, Cu-sulfide and native Cu in the matrix of Tieschitz allows for the first time to determine the isotopic abundance of the Hg isotopes both in matrix and chondrules (and potentially Cd).

  4. Band structure of odd-mass lanthanum nuclei

    NASA Astrophysics Data System (ADS)

    Sharma, Deepti; Verma, Preeti; Singh, Suram; Bharti, Arun; Khosa, S. K.

    2014-04-01

    Negative parity energy states in 121-131La have been studied using Projected Shell Model (PSM). Some nuclear structure properties like yrast spectra, back-bending in moment of inertia, reduced transition probabilities and band diagrams have been described. The experimental feature of the co-existence of prolate-oblate shapes in 125-131La isotopes has been satisfactorily explained by PSM results. Comparison of the theoretical data with their experimental counterparts has also been made. From the calculations, it is found that the yrast states arise because of multi-quasiparticle states.

  5. Hg speciation and stable isotope signatures in human hair as a tracer for dietary and occupational exposure to mercury.

    PubMed

    Laffont, Laure; Sonke, Jeroen E; Maurice, Laurence; Monrroy, Selma Luna; Chincheros, Jaime; Amouroux, David; Behra, Philippe

    2011-12-01

    Exposure of humans and wildlife to various inorganic and organometallic forms of mercury (Hg) may induce adverse health effects. While human populations in developed countries are mainly exposed to marine fish monomethylmercury (MMHg), this is not necessarily the case for developing countries and diverse indigenous people. Identification of Hg exposure sources from biomonitor media such as urine or hair would be useful in combating exposure. Here we report on the Hg stable isotope signatures and Hg speciation in human hair across different gold miner, indigenous and urban populations in Bolivia and France. We found evidence for both mass-dependent isotope fractionation (MDF) and mass-independent isotope fractionation (MIF) in all hair samples. Three limiting cases of dominant exposure to inorganic Hg (IHg), freshwater fish MMHg, and marine fish MMHg sources are used to define approximate Hg isotope source signatures. Knowing the source signatures, we then estimated Hg exposure sources for the Bolivian gold miner populations. Modeled IHg levels in hair correspond well to measured IHg concentrations (R = 0.9), demonstrating that IHg exposure sources to gold miners can be monitored in hair samples following either its chemical speciation or isotopic composition. Different MMHg and inorganic exposure levels among gold miners appear to correspond to living and working conditions, including proximity to small towns, and artisanal vs large scale mining activity. PMID:22003970

  6. Isotope tracing of Hg pollution from artisanal small scale gold mining in an aquatic ecosystem of Amapá, Brazil

    NASA Astrophysics Data System (ADS)

    Adler Miserendino, R.; Silbergeld, E. K.; Guimarães, J. D.; Ghosh, S.; Bergquist, B. A.

    2010-12-01

    Artisinal small scale gold mining (ASGM) is a central economic activity throughout the developing world. It is both a poverty driven and poverty alleviating process; however, ASGM leads to extensive pollution of waterways through the use of Hg to extract gold from deposits. There have been many studies conducted in the Amazon showing elevated levels of Hg in fish and sediment downstream of ASGM sites; however, the debate continues about the contribution of Hg from ASGM versus other potential sources of Hg. In this study, we investigate whether Hg stable isotope analysis can be used to trace mercury pollution from an ASGM site through an aquatic ecosystem in Amapá, Brazil. We measured the Hg isotopic composition of sediment cores from two lakes, only one of which was heavily impacted by the use of elemental Hg in ASGM, as well as from grab samples at the AGSM site and upstream and downstream from the AGSM site along the river which connects the polluted lake to the ASGM site. Hg from all samples were trapped via combustion using the Leeman Labs Hydra-C mercury analyzer and analyzed for both mass-independent and mass-dependent signatures using cold vapor multi-collector inductively coupled plasma mass spectrometry (CV-MC-ICP-MS). Detectable variations in the Hg isotopic signatures were apparent across our field sites, suggesting stable isotopic analysis has great potential to trace contamination pathways in waterways. Preliminary data demonstrate Hg from the ASGM site has unique isotopic signatures that are seen downstream. However, the impacted lake sediments do not have the mining signature despite having three times more Hg than the non-impacted lake. Based on this data, it may be possible to trace Hg from ASGM and assess whether it is impacting local ecosystems and food webs. Hair and soil samples will also be discussed. This demonstration is essential for the broader application of these tools for understanding and applying Hg isotopic analysis in other

  7. β-decay properties of neutron-deficient Pt, Hg, and Pb isotopes

    SciTech Connect

    Sarriguren, P.; Boillos, J. M.; Moreno, O.; Moya de Guerra, E.

    2015-10-15

    Neutron-deficient isotopes in the lead region are well established examples of the shape coexistence phenomenon in nuclei. In this work, bulk and decay properties, including deformation energy curves, charge mean square radii, Gamow-Teller (GT) strength distributions, and β-decay half-lives, are studied in neutron-deficient Pt, Hg, and Pb isotopes. The nuclear structure involved is described microscopically from deformed quasiparticle random-phase approximation calculations with residual interactions in both particle-hole and particle-particle channels, performed on top of a self-consistent deformed quasiparticle Skyrme Hartree-Fock basis. The sensitivity to deformation of the GT strength distributions in those isotopes is proposed as an additional complementary signature of the nuclear shape. The β-decay half-lives resulting from the GT strength distributions are compared to experiment to demonstrate the ability of the method.

  8. Hg Stable Isotope Time Trend in Ringed Seals Registers Decreasing Sea Ice Cover in the Alaskan Arctic.

    PubMed

    Masbou, Jérémy; Point, David; Sonke, Jeroen E; Frappart, Frédéric; Perrot, Vincent; Amouroux, David; Richard, Pierre; Becker, Paul R

    2015-08-01

    Decadal time trends of mercury (Hg) concentrations in Arctic biota suggest that anthropogenic Hg is not the single dominant factor modulating Hg exposure to Arctic wildlife. Here, we present Hg speciation (monomethyl-Hg) and stable isotopic composition (C, N, Hg) of 53 Alaskan ringed seal liver samples covering a period of 14 years (1988-2002). In vivo metabolic effects and foraging ecology explain most of the observed 1.6 ‰ variation in liver δ(202)Hg, but not Δ(199)Hg. Ringed seal habitat use and migration were the most likely factors explaining Δ(199)Hg variations. Average Δ(199)Hg in ringed seal liver samples from Barrow increased significantly from +0.38 ± 0.08‰ (±SE, n = 5) in 1988 to +0.59 ± 0.07‰ (±SE, n = 7) in 2002 (4.1 ± 1.2% per year, p < 0.001). Δ(199)Hg in marine biological tissues is thought to reflect marine Hg photochemistry before biouptake and bioaccumulation. A spatiotemporal analysis of sea ice cover that accounts for the habitat of ringed seals suggests that the observed increase in Δ(199)Hg may have been caused by the progressive summer sea ice disappearance between 1988 and 2002. While changes in seal liver Δ(199)Hg values suggests a mild sea ice control on marine MMHg breakdown, the effect is not large enough to induce measurable HgT changes in biota. This suggests that Hg trends in biota in the context of a warming Arctic are likely controlled by other processes. PMID:26132925

  9. Stable isotope (N, C, Hg) study of methylmercury sources and trophic transfer in the northern gulf of Mexico.

    PubMed

    Senn, David B; Chesney, Edward J; Blum, Joel D; Bank, Michael S; Maage, Amund; Shine, James P

    2010-03-01

    We combined N, C, and Hg stable isotope measurements to identify the most important factors that influence MeHg accumulation in fish from the northern Gulf of Mexico (nGOM), and to determine if coastal species residing in the Mississippi River (MR) plume and migratory oceanic species derive their MeHg from the same, or different, sources. In six coastal species and two oceanic species (blackfin and yellowfin tuna), trophic position as measured by delta(15)N explained most of the variance in log[MeHg] (r(2) approximately 0.8), but coastal species and tuna fell along distinct, nearly parallel lines with significantly different intercepts. The tuna also had significantly higher delta(202)Hg (0.2-0.5 per thousand) and Delta(201)Hg ( approximately 1.5 per thousand) than the coastal fish (delta(202)Hg = 0 to -1.0 per thousand; Delta(201)Hg approximately 0.4 per thousand). The observations can be best explained by largely disconnected food webs rooted in different baseline delta(15)N signatures (MR-plume vs oceanic) and isotopically distinct MeHg sources, with oceanic MeHg having undergone substantial photodegradation ( approximately 50%) before entering the base of the food web. Given the MR's large, productive footprint in the nGOM and the potential for exporting prey and MeHg to the adjacent oligotrophic GOM, the disconnected food webs and different MeHg sources are consistent with recent evidence in other systems of important oceanic MeHg sources. PMID:20104887

  10. The use of Pb, Sr, and Hg isotopes in Great Lakes precipitation as a tool for pollution source attribution.

    PubMed

    Sherman, Laura S; Blum, Joel D; Dvonch, J Timothy; Gratz, Lynne E; Landis, Matthew S

    2015-01-01

    The anthropogenic emission and subsequent deposition of heavy metals including mercury (Hg) and lead (Pb) present human health and environmental concerns. Although it is known that local and regional sources of these metals contribute to deposition in the Great Lakes region, it is difficult to trace emissions from point sources to impacted sites. Recent studies suggest that metal isotope ratios may be useful for distinguishing between and tracing source emissions. We measured Pb, strontium (Sr), and Hg isotope ratios in daily precipitation samples that were collected at seven sites across the Great Lakes region between 2003 and 2007. Lead isotope ratios ((207)Pb/(206)Pb=0.8062 to 0.8554) suggest that Pb deposition was influenced by coal combustion and processing of Mississippi Valley-Type Pb ore deposits. Regional differences in Sr isotope ratios ((87)Sr/(86)Sr=0.70859 to 0.71155) are likely related to coal fly ash and soil dust. Mercury isotope ratios (δ(202)Hg=-1.13 to 0.13‰) also varied among the sites, likely due to regional differences in coal isotopic composition, and fractionation occurring within industrial facilities and in the atmosphere. These data represent the first combined characterization of Pb, Sr, and Hg isotope ratios in precipitation collected across the Great Lakes region. We demonstrate the utility of multiple metal isotope ratios in parallel with traditional trace element multivariate statistical modeling to enable more complete pollution source attribution. PMID:25265397

  11. Evaluating the role of re-adsorption of dissolved Hg(2+) during cinnabar dissolution using isotope tracer technique.

    PubMed

    Jiang, Ping; Li, Yanbin; Liu, Guangliang; Yang, Guidi; Lagos, Leonel; Yin, Yongguang; Gu, Baohua; Jiang, Guibin; Cai, Yong

    2016-11-01

    Cinnabar dissolution is an important factor controlling mercury (Hg) cycling. Recent studies have suggested the co-occurrence of re-adsorption of the released Hg during the course of cinnabar dissolution. However, there is a lack of feasible techniques that can quantitatively assess the amount of Hg re-adsorbed on cinnabar when investigating cinnabar dissolution. In this study, a new method, based on isotope tracing and dilution techniques, was developed to study the role of Hg re-adsorption in cinnabar dissolution. The developed method includes two key components: (1) accurate measurement of both released and spiked Hg in aqueous phase and (2) estimation of re-adsorbed Hg on cinnabar surface via the reduction in spiked (202)Hg(2+). By adopting the developed method, it was found that the released Hg for trials purged with oxygen could reach several hundred μgL(-1), while no significant cinnabar dissolution was detected under anaerobic condition. Cinnabar dissolution rate when considering Hg re-adsorption was approximately 2 times the value calculated solely with the Hg detected in the aqueous phase. These results suggest that ignoring the Hg re-adsorption process can significantly underestimate the importance of cinnabar dissolution, highlighting the necessity of applying the developed method in future cinnabar dissolution studies. PMID:27322904

  12. Experimental investigation of mass-dependent and mass-independent fractionation of mercury isotopes

    NASA Astrophysics Data System (ADS)

    Bergquist, B. A.; Blum, J. D.; Marcus, J. W.; Biswas, A.

    2006-12-01

    Mercury is a globally distributed and highly toxic pollutant, the mobility and bioaccumulation of which is highly dependent on its redox cycling. With seven isotopes (including two odd-mass isotopes) and a relative mass difference of 4%, stable isotope fractionation of Hg could be a powerful tool to track and understand Hg cycling in the environment. Ongoing studies of natural mercury isotope variations in ore deposits, hydrothermal fluids, sediments, soils, fish tissues and bacterial cultures have documented a measurable range in Hg isotopes of up to ~5‰ in the ^{202}Hg/^{198}Hg ratio with most samples displaying mass-dependent fractionation. A small, but growing, body of data also suggests that natural samples display mass-independent fractionation of Hg isotopes. In this study, we explore mechanisms that lead to both mass- dependent and mass-independent fractionation of Hg isotopes. Isotope ratios were measured by continuous- flow cold-vapor generation coupled to MC-ICPMS with an external precision of ±0.1‰ (2SD). We observe three distinct types of isotope fractionation for Hg: (1) mass-dependent fractionation, (2) mass- independent fractionation of odd isotopes concurrent with mass-dependent fractionation of even isotopes, and (3) mass-independent fractionation of all Hg isotopes. Reduction of Hg species to Hg(0) vapor is an important mechanism for removal of Hg from aqueous systems into the atmosphere. Reduction of Hg occurs through numerous pathways including photoreduction, abiotic organic reduction, and biological reduction. We find that photoreduction of Hg(II) by natural sunlight leads to mass-independent fractionation of the odd isotopes (^{201}Hg, ^{199}Hg) with several permil deviations from predicted mass dependence, and mass- dependent fractionation of the even isotopes. In contrast, both biological reduction (Kritee et al., 2006) and dark abiotic organically mediated reduction follow mass-dependent fractionation of even and odd isotopes

  13. {beta}-decay in neutron-deficient Hg, Pb, and Po isotopes

    SciTech Connect

    Moreno, O.; Sarriguren, P.; Alvarez-Rodriguez, R.; Guerra, E. Moya de

    2006-05-15

    The effect of nuclear deformation on the energy distributions of the Gamow-Teller strength is studied in neutron-deficient Hg, Pb, and Po even isotopes. The theoretical framework is based on a self-consistent deformed Skyrme Hartree-Fock mean field with pairing correlations between like nucleons in BCS approximation and residual spin-isospin interactions treated in the proton-neutron quasiparticle random-phase approximation. After a systematic study of the Gamow-Teller strength distributions in the low-excitation-energy region, relevant for {beta}{sup +} decay, we have identified the best candidates to look for deformation signatures in their {beta}{sup +}-decay patterns. {beta}{sup +} half-lives and total Gamow-Teller strengths B(GT{sup {+-}}) are analyzed as well.

  14. A case for in vivo mass-independent fractionation of mercury isotopes in fish

    NASA Astrophysics Data System (ADS)

    Das, Reshmi; Salters, Vincent J. M.; Odom, A. Leroy

    2009-11-01

    The recent discovery of mass-independent fractionation of mercury isotopes allows new constraints to be placed on the mercury cycle. Here we report new Hg isotopic analyses of zooplankton and fish from different trophic levels of a freshwater lake (Lake Jackson, Florida) bearing systematic mass-independent fractionation of mercury isotopes. Fish muscle tissues show a progressive enrichment in the odd-mass mercury isotopes having odd atomic mass numbers (199 and 201) with increasing trophic level. Trophic level was determined based on nitrogen isotopic composition as well as fish stomach content. Zooplankton in the lake contain mercury with Δ199Hg and Δ201Hg values of +0.43 (±0.07)‰ and +0.44 (±0.07)‰, respectively. The Δ199Hg values increase by ˜1‰ from ˜+0.4‰ in zooplankton, juvenile bluegill, and several other small fishes to Δ199Hg = +1.36‰ for the Florida gar, which is the top predator fish in the lake. Previous observations of odd-mass-number isotope enrichment of mercury have been explained by photoreduction and demethylation of methyl mercury in the water column or as isotope effects related to microbial methylation. However, our data and the data of Jackson et al. (2008) are also consistent with in vivo production of mass-independent fractionation. Considering the alternatives, mass-independent fractionation by metabolic processes is the most straightforward explanation for the mercury isotope data. There are two known mechanisms for mass-independent fractionation of mercury, i.e., the nuclear volume effect and the magnetic isotope effect. While the data are insufficient to serve as proof, the magnitude of the mass-independent effect and the nearly equal enrichment of 199Hg and 201Hg seem most suggestive of a magnetic isotope effect.

  15. Identical Hg isotope mass dependent fractionation signature during methylation by sulfate-reducing bacteria in sulfate and sulfate-free environment.

    PubMed

    Perrot, Vincent; Bridou, Romain; Pedrero, Zoyne; Guyoneaud, Remy; Monperrus, Mathilde; Amouroux, David

    2015-02-01

    Inorganic mercury (iHg) methylation in aquatic environments is the first step leading to monomethylmercury (MMHg) bioaccumulation in food webs and might play a role in the Hg isotopic composition measured in sediments and organisms. Methylation by sulfate reducing bacteria (SRB) under sulfate-reducing conditions is probably one of the most important sources of MMHg in natural aquatic environments, but its influence on natural Hg isotopic composition remains to be ascertained. In this context, the methylating SRB Desulfovibrio dechloracetivorans (strain BerOc1) was incubated under sulfate reducing and fumarate respiration conditions (SR and FR, respectively) to determine Hg species specific (MMHg and IHg) isotopic composition associated with methylation and demethylation kinetics. Our results clearly establish Hg isotope mass-dependent fractionation (MDF) during biotic methylation (-1.20 to +0.58‰ for δ(202)Hg), but insignificant mass-independent fractionation (MIF) (-0.12 to +0.15‰ for Δ(201)Hg). During the 24h of the time-course experiments Hg isotopic composition in the produced MMHg becomes significantly lighter than the residual IHg after 1.5h and shows similar δ(202)Hg values under both FR and SR conditions at the end of the experiments. This suggests a unique pathway responsible for the MDF of Hg isotopes during methylation by this strain regardless the metabolism of the cells. After 9 h of experiment, significant simultaneous demethylation is occurring in the culture and demethylates preferentially the lighter Hg isotopes of MMHg. Therefore, depending on their methylation/demethylation capacities, SRB communities in natural sulfate reducing conditions likely have a significant and specific influence on the Hg isotope composition of MMHg (MDF) in sediments and aquatic organisms. PMID:25564955

  16. Anisotropic alpha decay from oriented odd-mass isotopes of some light actinides

    SciTech Connect

    Berggren, T. )

    1994-11-01

    Half-lives and anisotropies in the [alpha] decay of [sup 205,207,209]Rn, [sup 219]Rn, [sup 221]Fr, [sup 227,229]Pa, and [sup 229]U have been calculated using the reaction-theoretical formalism proposed by Jackson and Rhoades-Brown and adapted for axially symmetric deformed nuclei by Berggren and Olanders. The possibility of octupole deformation has been taken into account. In addition, a variant of triaxial octupole deformation has been considered tentatively in the case of [sup 227]Pa and [sup 229]Pa.

  17. Use of stable isotope signatures to determine mercury sources in the Great Lakes

    USGS Publications Warehouse

    Lepak, Ryan F.; Yin, Runsheng; Krabbenhoft, David P.; Ogorek, Jacob M.; DeWild, John F.; Holsen, Thomas M.; Hurley, James P.

    2015-01-01

    Sources of mercury (Hg) in Great Lakes sediments were assessed with stable Hg isotope ratios using multicollector inductively coupled plasma mass spectrometry. An isotopic mixing model based on mass-dependent (MDF) and mass-independent fractionation (MIF) (δ202Hg and Δ199Hg) identified three primary Hg sources for sediments: atmospheric, industrial, and watershed-derived. Results indicate atmospheric sources dominate in Lakes Huron, Superior, and Michigan sediments while watershed-derived and industrial sources dominate in Lakes Erie and Ontario sediments. Anomalous Δ200Hg signatures, also apparent in sediments, provided independent validation of the model. Comparison of Δ200Hg signatures in predatory fish from three lakes reveals that bioaccumulated Hg is more isotopically similar to atmospherically derived Hg than a lake’s sediment. Previous research suggests Δ200Hg is conserved during biogeochemical processing and odd mass-independent fractionation (MIF) is conserved during metabolic processing, so it is suspected even is similarly conserved. Given these assumptions, our data suggest that in some cases, atmospherically derived Hg may be a more important source of MeHg to higher trophic levels than legacy sediments in the Great Lakes.

  18. An in-depth evaluation of accuracy and precision in Hg isotopic analysis via pneumatic nebulization and cold vapor generation multi-collector ICP-mass spectrometry.

    PubMed

    Rua-Ibarz, Ana; Bolea-Fernandez, Eduardo; Vanhaecke, Frank

    2016-01-01

    Mercury (Hg) isotopic analysis via multi-collector inductively coupled plasma (ICP)-mass spectrometry (MC-ICP-MS) can provide relevant biogeochemical information by revealing sources, pathways, and sinks of this highly toxic metal. In this work, the capabilities and limitations of two different sample introduction systems, based on pneumatic nebulization (PN) and cold vapor generation (CVG), respectively, were evaluated in the context of Hg isotopic analysis via MC-ICP-MS. The effect of (i) instrument settings and acquisition parameters, (ii) concentration of analyte element (Hg), and internal standard (Tl)-used for mass discrimination correction purposes-and (iii) different mass bias correction approaches on the accuracy and precision of Hg isotope ratio results was evaluated. The extent and stability of mass bias were assessed in a long-term study (18 months, n = 250), demonstrating a precision ≤0.006% relative standard deviation (RSD). CVG-MC-ICP-MS showed an approximately 20-fold enhancement in Hg signal intensity compared with PN-MC-ICP-MS. For CVG-MC-ICP-MS, the mass bias induced by instrumental mass discrimination was accurately corrected for by using either external correction in a sample-standard bracketing approach (SSB) or double correction, consisting of the use of Tl as internal standard in a revised version of the Russell law (Baxter approach), followed by SSB. Concomitant matrix elements did not affect CVG-ICP-MS results. Neither with PN, nor with CVG, any evidence for mass-independent discrimination effects in the instrument was observed within the experimental precision obtained. CVG-MC-ICP-MS was finally used for Hg isotopic analysis of reference materials (RMs) of relevant environmental origin. The isotopic composition of Hg in RMs of marine biological origin testified of mass-independent fractionation that affected the odd-numbered Hg isotopes. While older RMs were used for validation purposes, novel Hg isotopic data are provided for the

  19. Particle-hole intruder levels in 67Cu, collectivity, monopole shifts, and the hockey-stick behaviour of ell - 1/2 5/2- levels in neutron-rich odd-mass Cu nuclei

    NASA Astrophysics Data System (ADS)

    Walters, W. B.; Chiara, C. J.

    2011-01-01

    A new sequence of gamma rays with energies of 572, 499, 585, and 674 keV has been identified in 67Cu populating the 7/2- level at 2362 keV. Owing to the strong population of the 2362-keV level via an ell = 3 proton pickup reaction, that level is assigned to be an f7/2-1 2-particle-1-hole "intruder" proton configuration, and the new levels are found to form a sequence consistent with intruder sequences in the adjacent odd-mass Cu isotopes and in the odd-mass Sb isotopes. The changing position of the intruder sequence in the odd-mass Cu isotopes is discussed and related to the onset of collectivity associated with the presence of g9/2 neutrons beyond N = 40. The increase in collectivity is also discussed for a number of isotonic and isotopic chains as more protons or neutrons, respectively, are added beyond an oscillator shell boundary. For most of these systems, the ell -1/2 levels show a systematic "hockey-stick-like" behaviour with a sharp decrease in energy with the addition of the first protons or neutrons, owing to both the added collectivity and the tensor interaction, and then a lower slope when collectivity changes are diminished and only the tensor interaction is influencing the changes in level positions.

  20. Mass-independent fractionation of mercury isotopes in compact fluorescent light bulbs

    NASA Astrophysics Data System (ADS)

    Mead, C.; Anbar, A. D.; Lyons, J. R.; Johnson, T. M.

    2010-12-01

    Compact fluorescent lightbulbs (CFLs) are a growing source of Hg pollution. The high-energy environment of the CFLs combined with the known partitioning of Hg into the bulb walls could provide an environment for unusual isotope fractionation that could be used to trace pollution from improper bulb disposal. To investigate this possibility, we analyzed the isotope composition of Hg in CFL glass, phosphor powder, and whole bulbs from CFLs of known ages. We observed large, mass-independent fractionation of Hg isotopes between Hg embedded in the bulb wall and Hg in the liquid and vapor phases, which are the initial reservoir of Hg in the bulb. This fractionation results in the bulb wall showing enrichment of 198Hg, 199Hg, 200Hg, 201Hg, and 204Hg relative to 202Hg, the most abundant isotope. Both the amount of Hg embedded in the glass and the magnitude of the isotope enrichment were found to increase with the number of hours of light bulb use. For a CFL used for 3600 hours (with a rated lifetime of 10,000 hours), the isotopic composition of the Hg in the glass was enriched by 34.5‰, 4.1‰, 6.3‰, 21.1‰, and 12.1‰ for 198Hg/202Hg, 199Hg/202Hg, 200Hg/202Hg, 201Hg/202Hg, and 204Hg/202Hg, respectively, compared to NIST SRM-3133. This pattern of isotope enrichments is not correlated with mass differences for any of the isotope ratios. In contrast, the other mass-independent effects that have recently been observed in Hg isotopes (i.e., the nuclear volume and magnetic isotope effects) resemble mass-dependent fractionation for the even mass isotopes and are anomalous only for the odd mass isotopes, 199Hg and 201Hg. First order theoretical calculations using Hg absorption and emission data for each of the hyperfine components of the 253.7 nm line have shown that similar fractionation can be produced through an optical self-shielding effect. This effect occurs because each Hg isotope has a different degree of optical saturation at their respective absorption wavelength

  1. Description of electromagnetic and favored α transitions in heavy odd-mass nuclei

    NASA Astrophysics Data System (ADS)

    Dumitrescu, A.; Delion, D. S.

    2016-02-01

    We describe electromagnetic and favored α transitions to rotational bands in odd-mass nuclei built upon a single particle state with angular momentum projection Ω ≠1/2 in the region 88 ≤Z ≤98 . We use the particle coupled to an even-even core approach described by the coherent state model and the coupled channels method to estimate partial α -decay widths. We reproduce the energy levels of the rotational band where favored α transitions occur for 26 nuclei and predict B (" close=")E 2 )">E 2 values for electromagnetic transitions to the band head using a deformation parameter and a Hamiltonian strength parameter for each nucleus, together with an effective collective charge depending linearly on the deformation parameter. Where experimental data are available, the contribution of the single particle effective charge to the total B value is calculated. The Hamiltonian describing the α -nucleus interaction contains two terms, a spherically symmetric potential given by the double-folding of the M3Y nucleon-nucleon interaction plus a repulsive core simulating the Pauli principle and a quadrupole-quadrupole (QQ) interaction. The α -decaying state is identified as a narrow outgoing resonance in this potential. The intensity of the transition to the first excited state is reproduced by the QQ coupling strength. It depends linearly both on the nuclear deformation and the square of the reduced width for the decay to the band head, respectively. Predicted intensities for transitions to higher excited states are in a reasonable agreement with experimental data. This formalism offers a unified description of energy levels, electromagnetic and favored α transitions for known heavy odd-mass α emitters.

  2. Double-neutron capture reaction and natural abundance of 183W, 195Pt and 199Hg isotopes

    NASA Astrophysics Data System (ADS)

    Karamian, S. A.; Aksenov, N. V.; Bozhikov, G. A.

    2016-06-01

    There are much data on neutron cross sections over the chart of nuclides for stable isotopes and not as much for the radioactive ones. Double neutron capture experiments could be fruitful to provide more data. Time-integrated mean flux of slow neutrons reaches the value of 2.3-1012 n/cm2 s at the irradiation port near the active zone of the IBR-2 pulsed reactor of JINR. This is enough to detect the double neutron capture products by the activation method. A high capture cross section is obtained in the present experiment for intermediate radioactive 182Ta and 194Ir target nuclides. Together with the known data for 198Au, these values may prove an essential role of double neutron capture process for nucleosynthesis of 183W, 195Pt and 199Hg isotopes at stellar conditions.

  3. α -decay half-lives of odd-mass nuclei with differences between neutron and proton distributions

    NASA Astrophysics Data System (ADS)

    Ni, Dongdong; Ren, Zhongzhou

    2016-05-01

    Effects of differences between neutron and proton distributions on α decay are investigated for odd-mass nuclei within the generalized density-dependent cluster model. The neutron skin thickness is employed to gauge the differences and it is considered in numerically computing the double-folding α -nucleus potentials. In terms of the characteristic of odd-mass α emitters, special attention is paid to the α decays from ground or isomeric states which end in the ground states of daughter nuclei and furthermore belong to favored α decays. The calculations with the neutron skin thickness yield shorter half-lives, suggesting a smaller preformation factor. This is quite consistent with the conclusions for even-even α emitters. Moreover, α -decay calculations are extended for odd-mass isomers and superheavy nuclei. The calculated α -decay half-lives are found to be in good agreement with the experimental data.

  4. Stellar (n ,γ ) cross sections of neutron-rich nuclei: Completing the isotope chains of Yb, Os, Pt, and Hg

    NASA Astrophysics Data System (ADS)

    Marganiec, J.; Dillmann, I.; Domingo-Pardo, C.; Käppeler, F.

    2014-12-01

    The (n ,γ ) cross sections of the most neutron-rich stable isotopes of Yb, Os, Pt, and Hg have been determined in a series of activation measurements at the Karlsruhe 3.7 MV Van de Graaff accelerator, using the quasistellar neutron spectrum for k T =25 keV that can be produced with the 7Li(p ,n ) 7Be reaction. In this way, Maxwellian averaged cross sections could be directly obtained with only minor corrections. After irradiation the induced activities were counted with a HPGe detector via the strongest γ -ray lines. The stellar neutron capture cross sections of Yb,176174, Os,192190, Pt,198196, and Hg,204202, extrapolated to k T =30 keV, were found to be 157 ±6 mb, 114 ±8 mb, 278 ±11 mb, 160 ±7 mb, 171 ±19 mb, 94 ±4 mb, 62 ±2 mb, and 32 ±15 mb, respectively. In the case of 196Pt the partial cross section to the isomeric state at 399.5 keV could be determined as well. With these results the cross section data for long isotopic chains could be completed for a discussion of the predictive power of statistical model calculations towards the neutron-rich and proton-rich sides of the stability valley.

  5. Automated product recovery in a Hg-196 photochemical isotope separation process

    DOEpatents

    Grossman, M.W.; Speer, R.

    1992-07-21

    A method of removing deposited product from a photochemical reactor used in the enrichment of [sup 196]Hg has been developed and shown to be effective for rapid re-cycling of the reactor system. Unlike previous methods relatively low temperatures are used in a gas and vapor phase process of removal. Importantly, the recovery process is understood in a quantitative manner so that scaling design to larger capacity systems can be easily carried out. 2 figs.

  6. Automated product recovery in a HG-196 photochemical isotope separation process

    DOEpatents

    Grossman, Mark W.; Speer, Richard

    1992-01-01

    A method of removing deposited product from a photochemical reactor used in the enrichment of .sup.196 Hg has been developed and shown to be effective for rapid re-cycling of the reactor system. Unlike previous methods relatively low temperatures are used in a gas and vapor phase process of removal. Importantly, the recovery process is understood in a quantitative manner so that scaling design to larger capacity systems can be easily carried out.

  7. A new approach to understand methylmercury (CH3Hg) sources and transformation pathways: Compound-specific carbon stable isotope analysis by GC-C-IRMS

    NASA Astrophysics Data System (ADS)

    Baya, P. A.; Point, D.; Amouroux, D. P.; Lebreton, B.; Guillou, G.

    2015-12-01

    Methylmercury (CH3Hg) is a potent neurotoxin which is readily assimilated by organisms and bio-accumulates in aquatic food webs. In humans, consumption of CH3Hg contaminated marine fish is the major route of mercury exposure. However, our understanding of CH3Hg transformation pathways is still incomplete. To close this knowledge gap, we propose to explore the stable carbon isotopic composition (δ13C) of the methyl group of CH3Hg for a better understanding of its sources and transformation mechanisms. The method developed for the determination of the δ13C value of CH3Hg in biological samples involves (i) CH3Hg selective extraction, (ii) derivatization, and (iii) separation by gas chromatography (GC) prior to analysis by combustion isotope ratio mass spectrometry (C-IRMS). We present the figures of merit of this novel method and the first δ13C signatures for certified materials (ERM-CE464, BCR414) and biological samples at different marine trophic levels (i.e., tuna fish, zooplankton). The implications of this new approach to trace the pathways associated with Hg methylation and the mechanisms involved will be discussed.

  8. Mass-Dependent and -Independent Fractionation of Mercury Isotope during Gas-Phase Oxidation of Elemental Mercury Vapor by Atomic Cl and Br.

    PubMed

    Sun, Guangyi; Sommar, Jonas; Feng, Xinbin; Lin, Che-Jen; Ge, Maofa; Wang, Weigang; Yin, Runsheng; Fu, Xuewu; Shang, Lihai

    2016-09-01

    This study presents the first measurement of Hg stable isotope fractionation during gas-phase oxidation of Hg(0) vapor by halogen atoms (Cl(•), Br(•)) in the laboratory at 750 ± 1 Torr and 298 ± 3 K. Using a relative rate technique, the rate coefficients for Hg(0)+Cl(•) and Hg(0)+Br(•) reactions are determined to be (1.8 ± 0.5) × 10(-11) and (1.6 ± 0.8) × 10(-12) cm(3) molecule(-1) s(-1), respectively. Results show that heavier isotopes are preferentially enriched in the remaining Hg(0) during Cl(•) initiated oxidation, whereas being enriched in the product during oxidation by Br(•). The fractionation factors for (202)Hg/(198)Hg during the Cl(•) and Br(•) initiated oxidations are α(202/198) = 0.99941 ± 0.00006 (2σ) and 1.00074 ± 0.00014 (2σ), respectively. A Δ(199)Hg/Δ(201)Hg ratio of 1.64 ± 0.30 (2σ) during oxidation of Hg(0) by Br atoms suggests that Hg-MIF is introduced by the nuclear volume effect (NVE). In contrast, the Hg(0) + Cl(•) reaction produces a Δ(199)Hg/Δ(201)Hg-slope of 1.89 ± 0.18 (2σ), which in addition to a high degree of odd-mass-number isotope MIF suggests impacts from MIF effects other than NVE. This reaction also exhibits significant MIF of (200)Hg (Δ(200)Hg, up to -0.17‰ in the reactant) and is the first physicochemical process identified to trigger (200)Hg anomalies that are frequently detected in atmospheric samples. PMID:27501307

  9. Nuclear volume effects in equilibrium stable isotope fractionations of mercury, thallium and lead.

    PubMed

    Yang, Sha; Liu, Yun

    2015-01-01

    The nuclear volume effects (NVEs) of Hg, Tl and Pb isotope systems are investigated with careful evaluation on quantum relativistic effects via the Dirac's formalism of full-electron wave function. Equilibrium (202)Hg/(198)Hg, (205)Tl/(203)Tl, (207)Pb/(206)Pb and (208)Pb/(206)Pb isotope fractionations are found can be up to 3.61‰, 2.54‰, 1.48‰ and 3.72‰ at room temperature, respectively, larger than fractionations predicted by classical mass-dependent isotope fractionations theory. Moreover, the NVE can cause mass-independent fractionations (MIF) for odd-mass isotopes and even-mass isotopes. The plot of [formula in text] for Hg-bearing species falls into a straight line with the slope of 1.66, which is close to previous experimental results. For the first time, Pb(4+)-bearing species are found can enrich heavier Pb isotopes than Pb(2+)-bearing species to a surprising extent, e.g., the enrichment can be up to 4.34‰ in terms of (208)Pb/(206)Pb at room temperature, due to their NVEs are in opposite directions. In contrast, fractionations among Pb(2+)-bearing species are trivial. Therefore, the large Pb fractionation changes provide a potential new tracer for redox conditions in young and closed geologic systems. The magnitudes of NVE-driven even-mass MIFs of Pb isotopes (i.e., [formula in text]) and odd-mass MIFs (i.e., [formula in text) are almost the same but with opposite signs. PMID:26224248

  10. Nuclear volume effects in equilibrium stable isotope fractionations of mercury, thallium and lead

    PubMed Central

    Yang, Sha; Liu, Yun

    2015-01-01

    The nuclear volume effects (NVEs) of Hg, Tl and Pb isotope systems are investigated with careful evaluation on quantum relativistic effects via the Dirac’s formalism of full-electron wave function. Equilibrium 202Hg/198Hg, 205Tl/203Tl, 207Pb/206Pb and 208Pb/206Pb isotope fractionations are found can be up to 3.61‰, 2.54‰, 1.48‰ and 3.72‰ at room temperature, respectively, larger than fractionations predicted by classical mass-dependent isotope fractionations theory. Moreover, the NVE can cause mass-independent fractionations (MIF) for odd-mass isotopes and even-mass isotopes. The plot of vs. for Hg-bearing species falls into a straight line with the slope of 1.66, which is close to previous experimental results. For the first time, Pb4+-bearing species are found can enrich heavier Pb isotopes than Pb2+-bearing species to a surprising extent, e.g., the enrichment can be up to 4.34‰ in terms of 208Pb/206Pb at room temperature, due to their NVEs are in opposite directions. In contrast, fractionations among Pb2+-bearing species are trivial. Therefore, the large Pb fractionation changes provide a potential new tracer for redox conditions in young and closed geologic systems. The magnitudes of NVE-driven even-mass MIFs of Pb isotopes (i.e., ) and odd-mass MIFs (i.e., ) are almost the same but with opposite signs. PMID:26224248

  11. Shape trends and triaxiality in neutron-rich odd-mass Y and Nbisotopes

    SciTech Connect

    Luo, Y.X.; Rasmussen, J.O.; Gelberg, A.; Stefanescu, I.; Hamilton, J.H.; Ramayya, A.V.; Hwang, J.K.; Zhu, S.J.; Gore, P.M.; Fong,D.; Jones, E.F.; Wu, S.C.; Lee, I.Y.; Ginter, T.N.; Ma, W.C.; Ter-Akopian, G.M.; Daniel, A.V.; Stoyer, M.A.; Donangelo, R.

    2004-09-28

    New level schemes of Y and Nb isotopes are proposed based on measurements of prompt gamma rays from 252Cf fission at Gammasphere. Shape trends regarding triaxiality and quadrupole deformations are studied.

  12. Projected Shell Model Study of Yrast States of Neutron-Deficient Odd-Mass Pr Nuclei

    SciTech Connect

    Ibanes, A.; Ortiz, Mark E; Velazquez, V.; Galindo-Uribarri, Alfredo {nmn}; Hess, P. O.; Sun, Y.

    2011-01-01

    A wide variety of modern instruments allow us to study neutron-deficient nuclei in the A = 130 mass region. Highly deformed nuclei have been found in this region, providing opportunities to study the deformed rotational bands. The description of the 125,127,129,131,133Pr isotopes with the projected shell model is presented in this paper. Good agreement between theory and experiment is obtained and some characteristics are discussed, including the dynamic moment of inertia J (2), kinetic moment of inertia J (1), the crossing of rotational bands, and backbending effects.

  13. Projected shell model study of yrast states of neutron-deficient odd-mass Pr nuclei

    SciTech Connect

    Ibanez-Sandoval, A.; Ortiz, M. E.; Velazquez, V.; Galindo-Uribarri, A.; Hess, P. O.; Sun, Y.

    2011-03-15

    A wide variety of modern instruments allow us to study neutron-deficient nuclei in the A=130 mass region. Highly deformed nuclei have been found in this region, providing opportunities to study the deformed rotational bands. The description of the {sup 125,127,129,131,133}Pr isotopes with the projected shell model is presented in this paper. Good agreement between theory and experiment is obtained and some characteristics are discussed, including the dynamic moment of inertia J{sup (2)}, kinetic moment of inertia J{sup (1)}, the crossing of rotational bands, and backbending effects.

  14. Projected shell model study of yrast states of neutron-deficient odd-mass Pr nuclei

    NASA Astrophysics Data System (ADS)

    Ibáñez-Sandoval, A.; Ortiz, M. E.; Velázquez, V.; Galindo-Uribarri, A.; Hess, P. O.; Sun, Y.

    2011-03-01

    A wide variety of modern instruments allow us to study neutron-deficient nuclei in the A=130 mass region. Highly deformed nuclei have been found in this region, providing opportunities to study the deformed rotational bands. The description of the Pr125,127,129,131,133 isotopes with the projected shell model is presented in this paper. Good agreement between theory and experiment is obtained and some characteristics are discussed, including the dynamic moment of inertia J(2), kinetic moment of inertia J(1), the crossing of rotational bands, and backbending effects.

  15. Schottky Mass Measurement of the {sup 208}Hg Isotope: Implication for the Proton-Neutron Interaction Strength around Doubly Magic {sup 208}Pb

    SciTech Connect

    Chen, L.; Plass, W. R.; Geissel, H.; Scheidenberger, C.; Litvinov, Yu. A.; Beckert, K.; Beller, P.; Bosch, F.; Caceres, L.; Franzke, B.; Gerl, J.; Gorska, M.; Knoebel, R.; Kozhuharov, C.; Litvinov, S. A.; Mandal, S.; Muenzenberg, G.; Nolden, F.; Saito, N.; Saito, T.

    2009-03-27

    Time-resolved Schottky mass spectrometry has been applied to uranium projectile fragments which yielded the mass value for the {sup 208}Hg (Z=80, N=128) isotope. The mass excess value of ME=-13 265(31) keV has been obtained, which has been used to determine the proton-neutron interaction strength in {sup 210}Pb, as a double difference of atomic masses. The results show a dramatic variation of the strength for lead isotopes when crossing the N=126 neutron shell closure, thus confirming the empirical predictions that this interaction strength is sensitive to the overlap of the wave functions of the last valence neutrons and protons.

  16. Schottky mass measurement of the 208Hg isotope: implication for the proton-neutron interaction strength around doubly magic 208Pb.

    PubMed

    Chen, L; Litvinov, Yu A; Plass, W R; Beckert, K; Beller, P; Bosch, F; Boutin, D; Caceres, L; Cakirli, R B; Carroll, J J; Casten, R F; Chakrawarthy, R S; Cullen, D M; Cullen, I J; Franzke, B; Geissel, H; Gerl, J; Górska, M; Jones, G A; Kishada, A; Knöbel, R; Kozhuharov, C; Litvinov, S A; Liu, Z; Mandal, S; Montes, F; Münzenberg, G; Nolden, F; Ohtsubo, T; Patyk, Z; Podolyák, Zs; Propri, R; Rigby, S; Saito, N; Saito, T; Scheidenberger, C; Shindo, M; Steck, M; Ugorowski, P; Walker, P M; Williams, S; Weick, H; Winkler, M; Wollersheim, H-J; Yamaguchi, T

    2009-03-27

    Time-resolved Schottky mass spectrometry has been applied to uranium projectile fragments which yielded the mass value for the 208Hg (Z=80, N=128) isotope. The mass excess value of ME=-13 265(31) keV has been obtained, which has been used to determine the proton-neutron interaction strength in 210Pb, as a double difference of atomic masses. The results show a dramatic variation of the strength for lead isotopes when crossing the N=126 neutron shell closure, thus confirming the empirical predictions that this interaction strength is sensitive to the overlap of the wave functions of the last valence neutrons and protons. PMID:19392270

  17. Pyrogenic inputs of anthropogenic Pb and Hg to sediments of the Hood Canal, Washington, in the 20th century: source evidence from stable Pb isotopes and PAH signatures.

    PubMed

    Louchouarn, Patrick; Kuo, Li-Jung; Brandenberger, Jill M; Marcantonio, Franco; Garland, Charity; Gill, Gary A; Cullinan, Valerie

    2012-06-01

    Combustion-derived PAHs and stable Pb isotopic signatures ((206)Pb/(207)Pb) in sedimentary records assisted in reconstructing the sources of atmospheric inputs of anthropogenic Pb and Hg to the Hood Canal, Washington. The sediment-focusing corrected peak fluxes of total Pb and Hg (1960-70s) demonstrate that the watershed of Hood Canal has received greater atmospheric inputs of these metals than its mostly rural land use would predict. The tight relationships between the Pb, Hg, and organic markers in the cores indicate that these metals are derived from industrial combustion emissions. Multiple lines of evidence point to the Asarco smelter, located in the Main Basin of Puget Sound, as the major emission source of these metals to the watershed of the Hood Canal. The evidence includes (1) similar PAH isomer ratios in sediment cores from the two basins, (2) the correlations between Pb, Hg, and Cu in sediments and previously studied environmental samples including particulate matter emitted from the Asarco smelter's main stack at the peak of production, and (3) Pb isotope ratios. The natural rate of recovery in Hood Canal since the 1970s, back to preindustrial metal concentrations, was linear and contrasts with recovery rates reported for the Main Basin which slowed post late 1980s. PMID:22541021

  18. Accumulation of methylmercury in rice and flooded soil in experiments with an enriched isotopic Hg(II) tracer

    NASA Astrophysics Data System (ADS)

    Strickman, R. J.; Mitchell, C. P. J.

    2015-12-01

    Methylmercury (MeHg) is a neurotoxin produced in anoxic aquatic sediments. Numerous factors, including the presence of aquatic plants, alter the biogeochemistry of sediments, affecting the rate at which microorganisms transform bioavailable inorganic Hg (IHg) to MeHg. Methylmercury produced in flooded paddy soils and its transfer into rice has become an important dietary consideration. An improved understanding of how MeHg reaches the grain and the extent to which rice alters MeHg production in rhizosphere sediments could help to inform rice cultivation practices. We conducted a controlled greenhouse experiment with thirty rice plants grown in individual, flooded pots amended with enriched 200Hg. Unvegetated controls were maintained under identical conditions. At three plant growth stages (vegetative growth, flowering, and grain maturity), ten plants were sacrificed and samples collected from soil, roots, straw, panicle, and grain of vegetated and unvegetated pots, and assessed for MeHg and THg concentrations. We observed consistent ratios between ambient and tracer MeHg between soils (0.36 ±0.04 — 0.44 ± 0.09) and plant compartments (0.23 ± 0.07 -0.34 ± 0.05) indicating that plant MeHg contamination originates in the soil rather than in planta methylation. The majority of this MeHg was absorbed between the tillering (4.48 ± 2.38 ng/plant) and flowering (8.43 ± 5.12 ng/pl) phases, with a subsequent decline at maturity (2.87 ± 1.23 ng/pl) only partly explained by translocation to the developing grain, indicating that MeHg was demethylated in planta. In contrast, IHg was absorbed from both soil and air, as evidenced by the higher ambient IHg concentrations compared to tracer (3.76 ± 1.19 vs. 0.27 ± 0.40 ng/g). Surprisingly, MeHg accumulation was significantly (p= 0.042-- 0.003) lower in vegetated vs. unvegetated sediments at flowering (1.41 ± 0.26 vs. 1.57 ± 0.23) and maturity (1.27 ± 0.22 vs. 1.71 ± 0.25), suggesting that plant exudates bound Hg

  19. Stellar (n,{gamma}) cross sections of p-process isotopes. II. {sup 168}Yb, {sup 180}W, {sup 184}Os, {sup 190}Pt, and {sup 196}Hg

    SciTech Connect

    Marganiec, J.; Dillmann, I.; Pardo, C. Domingo; Kaeppeler, F.; Walter, S.

    2010-09-15

    The neutron-capture cross sections of {sup 168}Yb, {sup 180}W, {sup 184}Os, {sup 190}Pt, and {sup 196}Hg have been measured by means of the activation technique. The samples were irradiated in a quasistellar neutron spectrum of kT=25 keV, which was produced at the Karlsruhe 3.7-MV Van de Graaff accelerator via the {sup 7}Li(p,n){sup 7}Be reaction. Systematic uncertainties were investigated in repeated activations with different samples and by variation of the experimental parameters, that is, irradiation times, neutron fluxes, and {gamma}-ray counting conditions. The measured data were converted into Maxwellian-averaged cross sections at kT=30 keV, yielding 1214{+-}61, 624{+-}54, 590{+-}43, 511{+-}46, and 201{+-}11 mb for {sup 168}Yb, {sup 180}W, {sup 184}Os, {sup 190}Pt, and {sup 196}Hg, respectively. The present results either represent first experimental data ({sup 168}Yb, {sup 184}Os, and {sup 196}Hg) or could be determined with significantly reduced uncertainties ({sup 180}W and {sup 190}Pt). These measurements are part of a systematic study of stellar (n,{gamma}) cross sections of the stable p isotopes.

  20. The use of Pb, Sr, and Hg isotopes in Great Lakes precipitation as a tool for pollution source attribution

    EPA Science Inventory

    The anthropogenic emission and subsequent deposition of heavy metals including mercury (Hg) and lead (Pb) presents human health and environmental concerns. Although it is known that local and regional sources of these metals contribute to deposition in the Great Lakes region, it ...

  1. A non-LTE spectral analysis of the 3He and 4He isotopes in the HgMn star κ Cancri

    NASA Astrophysics Data System (ADS)

    Maza, Natalia L.; Nieva, María-Fernanda; Przybilla, Norbert

    2014-12-01

    Aims: We present a pilot study on non-local thermodynamic equilibrium (NLTE) line-formation computations for the isotopes 3He and 4He in the mercury-manganese star κ Cancri. The impact of NLTE effects on the determination of isotopic abundances and the vertical stratification of helium in the atmosphere is investigated. Methods: Modern NLTE line-formation computations were employed to analyse a high-resolution and high signal-to-noise ratio ESO-VLT/UVES spectrum of κ Cnc. The atmospheric parameters were determined from fitting the hydrogen Balmer lines and the spectral energy distribution. Multiple He i lines were investigated, including He i λ4921 Å and λ6678 Å, which show the widest isotopic splits. Results: Half of the observed He i lines in the spectrum of κ Cnc show significant NLTE strengthening, the effects are strongest in the red lines He iλ5875 Å and He iλ6678 Å. NLTE abundances from individual He i lines are up to a factor of ~3 lower than LTE values. Helium is found to be stratified in the atmosphere of κ Cnc. While the LTE analysis indicates a step-like profile of the helium abundance, a gradual decrease with height is indicated by the NLTE analysis. A 3He/4He ratio of ~0.25-0.30 is found. With the available data it cannot be decided whether the two isotopes follow the same stratification profile, or not. Conclusions: This work implies that NLTE effects may be ubiquitous in the atmospheres of HgMn stars and may have a significant impact on abundance determinations and the interpretation of the vertical abundance stratification of elements. Based on data products from observations made with ESO Telescopes at the La Silla Paranal Observatory under programme ID 076.B-0055(A).Figures 3 and 4 are available in electronic form at http://www.aanda.org

  2. The mass dependent and independent equilibrium fractionation of stable mercury isotopes during laboratory synthesis of metacinnabar and other mercury-bearing phases

    NASA Astrophysics Data System (ADS)

    Smith, R. S.; Wiederhold, J. G.; Bourdon, B.; Kretzschmar, R.

    2010-12-01

    that precipitates created from the Hg-nitrate had a Hg:S stoichiometry greater than 1:1 suggesting the formation of mixed Hg-S-nitrate phases. In contrast, the stoichiometry of the precipitates from the Hg-acetate experiments was close to 1:1. XRD analysis of the precipitates from the Hg-acetate system confirmed that metacinnabar was formed. The similarity of the concentration and isotope results obtained from the two time steps suggests that reactant and product were in equilibrium for both Hg systems. In all experimental samples, the precipitates were isotopically lighter than the corresponding supernatants. Small negative MIF anomalies for the odd mass Hg isotopes were found in the supernatants of the Hg-acetate. The observed MDF and MIF signatures can be explained by the change from Hg-O to Hg-S coordination during precipitation and are consistent in direction and magnitude with the predictions for equilibrium isotope effects caused by a combination of MDF and nuclear volume fractionation (Wiederhold et al., ES&T, 2010, 44:4191-4197). Additional experiments will be performed to confirm these findings.

  3. Methylation of Hg downstream from the Bonanza Hg mine, Oregon

    USGS Publications Warehouse

    Gray, John E.; Hines, Mark E.; Krabbenhoft, David P.; Thoms, Bryn

    2012-01-01

    Speciation of Hg and conversion to methyl-Hg were evaluated in stream sediment, stream water, and aquatic snails collected downstream from the Bonanza Hg mine, Oregon. Total production from the Bonanza mine was >1360t of Hg, during mining from the late 1800s to 1960, ranking it as an intermediate sized Hg mine on an international scale. The primary objective of this study was to evaluate the distribution, transport, and methylation of Hg downstream from a Hg mine in a coastal temperate climatic zone. Data shown here for methyl-Hg, a neurotoxin hazardous to humans, are the first reported for sediment and water from this area. Stream sediment collected from Foster Creek flowing downstream from the Bonanza mine contained elevated Hg concentrations that ranged from 590 to 71,000ng/g, all of which (except the most distal sample) exceeded the probable effect concentration (PEC) of 1060ng/g, the Hg concentration above which harmful effects are likely to be observed in sediment-dwelling organisms. Concentrations of methyl-Hg in stream sediment collected from Foster Creek varied from 11 to 62ng/g and were highly elevated compared to regional baseline concentrations (0.11-0.82ng/g) established in this study. Methyl-Hg concentrations in stream sediment collected in this study showed a significant correlation with total organic C (TOC, R2=0.62), generally indicating increased methyl-Hg formation with increasing TOC in sediment. Isotopic-tracer methods indicated that several samples of Foster Creek sediment exhibited high rates of Hg-methylation. Concentrations of Hg in water collected downstream from the mine varied from 17 to 270ng/L and were also elevated compared to baselines, but all were below the 770ng/L Hg standard recommended by the USEPA to protect against chronic effects to aquatic wildlife. Concentrations of methyl-Hg in the water collected from Foster Creek ranged from 0.17 to 1.8ng/L, which were elevated compared to regional baseline sites upstream and downstream

  4. Microscopic description of ground state magnetic moment and low-lying magnetic dipole excitations in heavy odd-mass 181Ta nucleus

    NASA Astrophysics Data System (ADS)

    Tabar, Emre; Yakut, Hakan; Kuliev, Ali Akbar

    2016-07-01

    The ground state magnetic moments and the low-lying magnetic dipole (Ml) transitions from the ground to excited states in heavy deformed odd-mass 181Ta have been microscopically investigated on the basis of the quasiparticle-phonon nuclear model (QPNM). The problem of the spurious state mixing in M1 excitations is overcome by a restoration method allowing a self-consistent determination of the separable effective restoration forces. Due to the self-consistency of the method, these effective forces contain no arbitrary parameters. The results of calculations are compared with the available experimental data, the agreement being reasonably satisfactory.

  5. Studies of the 198Hg(d,d') and 198Hg(d,p) reactions

    NASA Astrophysics Data System (ADS)

    Diaz Varela, A.; Garrett, P. E.; Bildstein, V.; Laffoley, A. T.; Maclean, A. D.; Rand, E. T.; Svensson, C. E.; Ball, G. C.; Faestermann, T.; Hertenberger, R.; Wirth, H.-F.

    2014-09-01

    Limits on the electric dipole moment (EDM) continue to decrease for 199Hg, the most stringent upper limit for a nuclear EDM to date. The experimental limit on the observed atomic EDM for 199Hg is converted to limits on fundamental CP-odd interactions via a calculation of the nuclear Schiff moment, requiring knowledge of the nuclear structure of 199Hg. The E 3 and E 1 strength distributions to the ground state of 199Hg, and E 2 transitions amongst excited states, would be ideal information to further constrain 199Hg Schiff moment theoretical models. The high level density of 199Hg makes those determinations challenging, however similar information can be obtained from exploring surrounding even-even Hg isotopes. As part of a campaign to study the Hg isotopes near 199Hg, two reactions, 198Hg(d,d')198 Hg and 198Hg(d,p)199Hg were studied using the Q3D spectrograph at the Maier-Leibnitz Laboratory (MLL) at Garching, Germany. A 22 MeV deuterium beam was used to impinge a 198Hg32S target. The (d,d') reaction allows us to probe the desired E 2 and E 3 matrix elements, while the (d,p) reaction provides information on the neutron single-particle states of 199Hg.

  6. Delta I = 1 staggering effect for negative parity rotational bands with K = 1/2 in W/Os/Pt odd-mass nuclei

    NASA Astrophysics Data System (ADS)

    Taha, M. M.

    2015-11-01

    The anomalous negative-parity bands of odd-mass nuclei W/Os/Pt for N = 103 isotones are studied within the framework of particle rotor model (PRM). The phenomenon of Δ I = 1 staggering or signature splitting in energies occurs as one plots the gamma transitional energy over spin (EGOS) versus spin for the 1/2-[521] band originating from N = 5 single particle orbital. The rotational band with K = 1/2 separates into two signature partners. The levels with I = 1/2, 5/2, 9/2,… are displaced relatively to the levels with I = 3/2,7/2,11/2,…. The deviations of the level energies from the rigid rotor values is described by Coriolis coupling.

  7. Identification of Atmospheric Mercury Input to Ecosystems From Precipitation Using Coupled Δ200Hg and Δ204Hg Fractionation

    NASA Astrophysics Data System (ADS)

    Blum, J. D.; Johnson, M. W.

    2015-12-01

    Mercury has seven stable isotopes, and during most biogeochemical reactions all of the isotopes fractionate mass dependently (MDF; relative to δ202/198Hg). The odd isotopes also fractionate mass independently (MIF) during reactions involving the magnetic isotope and nuclear volume effects. In 2010 we first reported MIF of 200Hg in precipitation (Gratz et al), and in 2013 we reported MIF of 204Hg in precipitation (Demers et al). Measurements of Δ200Hg are becoming more common and several studies have now used Δ200Hg as a tracer of Hg(II) deposited from the atmosphere (Chen et al, 2012; Strok et al 2015). Δ204Hg is much less commonly measured and reported, but sheds additional light on the mechanisms that might cause even isotope MIF. We observe Δ204Hg to be of opposite sign and ~2x the magnitude of Δ200Hg. The presence of coupled Δ200Hg and Δ204Hg is most useful for detecting precipitation inputs of Hg to ecosystems. We have measured Δ200Hg and Δ204Hg in hundreds of samples of precipitation, invertebrates, fish, moss, lichen, ice crystals and GEM at many locations in North America and Hawaii. When average values for each sample type at each study location are plotted as Δ200Hg versus Δ204Hg they fall on a linear array with slope=0.57 and R2=0.92. Samples of sediment, coal, various rock-types, and point-source contaminants have contrasting Δ200Hg and Δ204Hg indistinguishable from zero. We also use combined Δ200Hg and Δ204Hg to explore mechanisms leading to even isotope MIF. Ghosh et al (2012) measured nuclear volume fractionation and found even MIF to be undetectable. Mead et al (2013) calculated even mass MIF from nuclear self-shielding and it does not fit our observations of Δ200Hg/Δ204Hg in natural samples; they also measured MIF caused by implantation of Hg into glass in compact fluorescent lights (CFLs) and this is consistent with Δ200Hg/Δ204Hg in atmospheric Hg(II), suggesting the possibility of a common fractionation mechanism.

  8. Coupling atmospheric mercury isotope ratios and meteorology to identify sources of mercury impacting a coastal urban-industrial region near Pensacola, Florida, USA

    NASA Astrophysics Data System (ADS)

    Demers, Jason D.; Sherman, Laura S.; Blum, Joel D.; Marsik, Frank J.; Dvonch, J. Timothy

    2015-10-01

    Identifying the anthropogenic and natural sources of mercury (Hg) emissions contributing to atmospheric mercury on local, regional, and global scales continues to be a grand challenge. The relative importance of various direct anthropogenic emissions of mercury, in addition to natural geologic sources and reemission of previously released and deposited mercury, differs regionally and temporally. In this study, we used local-scale, mesoscale, and synoptic-scale meteorological analysis to couple the isotopic composition of ambient atmospheric mercury with potential sources of mercury contributing to a coastal urban-industrial setting near a coal-fired power plant in Pensacola, Florida, USA. We were able to broadly discern four influences on the isotopic composition of ambient atmospheric mercury impacting this coastal urban-industrial region: (1) local to regional urban-industrial anthropogenic emissions (mean δ202Hg = 0.44 ± 0.05‰, 1SD, n = 3), (2) marine-influenced sources derived from the Gulf of Mexico (mean δ202Hg = 0.77 ± 0.15‰, 1SD, n = 4), (3) continental sources associated with north-northwesterly flows from within the planetary boundary layer (mean δ202Hg = 0.65 ± 0.04‰, 1SD, n = 3), and (4) continental sources associated with north-northeasterly flows at higher altitudes (i.e., 2000 m above ground level; mean δ202Hg = 1.10 ± 0.21‰, 1SD, n = 8). Overall, these data, in conjunction with previous studies, suggest that the background global atmospheric mercury pool is characterized by moderately positive δ202Hg values; that urban-industrial emissions drive the isotopic composition of ambient atmospheric mercury toward lower δ202Hg values; and that air-surface exchange dynamics across vegetation and soils of terrestrial ecosystems drive the isotopic composition of ambient atmospheric mercury toward higher positive δ202Hg values. The data further suggest that mass-independent fractionation (MIF) of both even-mass- and odd-mass-number isotopes

  9. Unusual mercury isotopic compositions in aqueous environment

    NASA Astrophysics Data System (ADS)

    Chen, J.; Hintelmann, H.; Zheng, W.; Feng, X.; Cai, H.; Wang, Z.; Yuan, S.

    2014-12-01

    Preliminary studies have demonstrated both mass-dependent fractionation (MDF) and mass-independent fractionation (MIF) of Hg isotopes in natural samples. Laboratory experiments showed that photochemical reduction of inorganic mercury (iHg) and methylmercury (MMHg) and liquid-vapour evaporation could produce MIF of odd Hg isotopes. This was thought to cause the MIF actually observed in aquatic organisms. Although isotopic measurements of Hg in aqueous environment would give direct evidence, little data was reported for surface water samples. Recent work reported, unexpectedly, positive MIF of odd Hg isotopes in both precipitation and ambient air, in contrast with the prediction of laboratory experiments and measurements of Hg accumulated in lichens . Intriguingly, MIF of even-mass Hg isotope (200Hg) was also recently determined in the atmosphere. In contrast with the now mainstream observation of odd Hg isotope anomaly that has several theoretical explanations, the hitherto mysterious even Hg isotope anomalies were neither reported in laboratory experiments, nor predicted by isotope fractionation mechanisms, highlighting the importance of further study on Hg isotopes in variable systems. Our measurements of lichens and lake water samples from different countries show for the first time significant Δ200Hg in surface terrestrial reservoirs, realizing a direct connection of even Hg isotope anomaly in the terrestrial reservoirs to the atmospheric deposition, and fulfilling the gap of Δ200Hg between the atmosphere and the terrestrial receptors. The specific odd Hg isotope compositions determined in lake waters also support the atmosphere contribution, and may be directly linked to the high Δ199Hg values largely determined and manifested on the top of aqueous food web. Our data show that the watershed Hg input is another contributing source, rather than the in-lake processes, to explain the lacustrine Hg isotope anomalies. Interestingly, lake sediments are isotopically

  10. Elemental Mercury in Natural Waters: Occurrence and Determination of Particulate Hg(0).

    PubMed

    Wang, Yongmin; Li, Yanbin; Liu, Guangliang; Wang, Dingyong; Jiang, Guibin; Cai, Yong

    2015-08-18

    Elemental mercury, Hg(0), is ubiquitous in water and involved in key Hg biogeochemical processes. It is extensively studied as a purgeable dissolved species, termed dissolved gaseous mercury (DGM). Little information is available regarding nonpurgeable particulate Hg(0) in water, Hg(0) bound to suspended particulate matter (SPM), which is presumably present due to high affinity of Hg(0) adsorption on solids. By employing stable isotope tracer and isotope dilution (ID) techniques, we investigated the occurrence and quantification of particulate Hg(0) after Hg(0) being spiked into natural waters, aiming to provide firsthand information on particulate Hg(0) in water. A considerable fraction of (201)Hg(0) spiked in water (about 70% after 4 h equilibration) was bound to SPM and nonpurgeable, suggesting the occurrence of particulate Hg(0) in natural waters. A scheme, involving isotope dilution, purge and trap, and inductively coupled plasma mass spectrometry detection, was proposed to quantify particulate Hg(0) by the difference between DGM and total Hg(0), determined immediately and at equilibration after spiking ID Hg isotope, respectively. The application of this newly established method revealed the presence of particulate Hg(0) in Florida Everglades water, as the determined DGM levels (0.14 to 0.22 ng L(-1)) were remarkably lower than total Hg(0) (0.41 to 0.75 ng L(-1)). PMID:26196077

  11. Accumulation and translocation of 198Hg in four crop species.

    PubMed

    Cui, Liwei; Feng, Xinbin; Lin, Che-Jen; Wang, Xinming; Meng, Bo; Wang, Xun; Wang, Heng

    2014-02-01

    The uptake and transport of mercury (Hg) through vegetation play an important role in the biogeochemical cycling of Hg. However, quantitative information regarding Hg translocation in plants is poorly understood. In the present study, Hg uptake, accumulation, and translocation in 4 crops-rice (Oryza.sativa L.), wheat (Triticum L.), corn (Zea mays L.), and oilseed rape (Brassica campestris L.)-grown in Hoagland solution were investigated using a stable isotope ((198)Hg) tracing technique. The distribution of (198)Hg in root, stem, and leaf after uptake was quantified, and the release of (198)Hg into the air from crop leaf was investigated. It was found that the concentration of Hg accumulated in the root, stem, and leaf of rice increased linearly with the spiked (198)Hg concentration. The uptake equilibrium constant was estimated to be 2.35 mol Hg/g dry weight in rice root per mol/L Hg remaining in the Hoagland solution. More than 94% of (198)Hg uptake was accumulated in the roots for all 4 crops examined. The translocation to stem and leaf was not significant because of the absence of Hg(2+) complexes that facilitate Hg transport in plants. The accumulated (198)Hg in stem and leaf was not released from the plant at air Hg(0) concentration ranging from 0 ng/m(3) to 10 ng/m(3). Transfer factor data analysis showed that Hg translocation from stems to leaves was more efficient than that from roots to stems. PMID:24173818

  12. Interplay between octupole and quasiparticle excitations in {sup 178}Hg and {sup 180}Hg

    SciTech Connect

    Kondev, F. G.; Janssens, R. V. F.; Carpenter, M. P.; Abu Saleem, K.; Ahmad, I.; Alcorta, M.; Amro, H.; Bhattacharyya, P.; Brown, L. T.; Caggiano, J.

    2000-10-01

    Excited structures in the Z=80, {sup 178}Hg (N=98), and {sup 180}Hg (N=100) isotopes have been investigated with the Gammasphere spectrometer in conjunction with the recoil-decay tagging technique. The present data extend the previously known ground-state bands to higher spin and excitation energy. Negative parity bands with a complex decay towards the low spin states arising from both the prolate-deformed and the nearly spherical coexisting minima have been observed for the first time in both nuclei. It is shown that these sequences have characteristics in common with negative-parity bands in the heavier even-even Hg isotopes as well as in the Os and Pt isotones. These structures are interpreted as being associated at low spin with an octupole vibration which is crossed at moderate frequency by a shape driving, two-quasiproton excitation.

  13. Mercury isotope compositions in North American forest soils and litters

    NASA Astrophysics Data System (ADS)

    Zheng, W.; Obrist, D.; Bergquist, B. A.

    2013-12-01

    Soils represent one of the largest reservoirs of mercury on Earth, playing a critical role in the natural cycle of mercury by acting as both a sink and source. However, it is not well understood how soils sequestrate and remobilize Hg. Natural variations in stable Hg isotopes are being explored as a promising tool in studying the transformation and transport of Hg. However, Hg isotopic data in soils is scarce. In addition, the limited isotopic data that exists is significantly different from those of atmospheric Hg, which is one of the major sources of Hg to soils. For example, Hg mass independent fractionation (MIF, typically reported as Δ199Hg) is positive in atmospheric wet deposition, but most soils display negative Δ199Hg. MIF on 200Hg (Δ200Hg) is also observed in atmospheric wet deposition, but not in soils. The discrepancy between soils and atmospheric samples is still unexplained. In this study, we surveyed the Hg isotope compositions in soil profiles, litters and fresh vegetation from four different forest sites across United States (Thompson forest, WA, Truckee, CA, Niwot Ridge, CO and Howland, MA). The current results from the WA site show that soils primarily display negative mass dependent fractionation for the even isotopes (MDF, reported as δ202Hg) with values for δ202Hg of up to -2.0‰. Significant MIF for both odd isotopes is also observed in all WA soil samples and Δ199Hg is mostly negative (up to -0.4‰). No MIF on 200Hg is observed in these soils. The negative Δ199Hg in soils is inconsistent with the positive Δ199Hg reported in atmospheric wet deposition, suggesting that either Hg transformations within or on the surface of soils and/or plants alter its isotope composition after deposition or other types of Hg deposition (e.g., Hg(0) or Hg(II) dry deposition) is more predominant. The Δ199Hg/Δ201Hg ratio is close to 1 in the soils, which is consistent with the results of laboratory photochemical reduction of inorganic Hg

  14. Hg-1212 and Hg-1223 single crystals: Synthesis and characterisation

    NASA Astrophysics Data System (ADS)

    Gatt, R.; Olsson, E.; Morawski, A.; Lada, T.; Paszewin, A.; Bryntse, I.; Grishin, A. M.; Eeltsev, Yu.; Berastegui, P.; Johansson, L.-G.

    1997-02-01

    Single crystals of HgBa 2CaCu 2O 6+δ (Hg-1212) and HgBa 2Ca 2Cu 3O 8+δ (Hg-1223) were grown from the melt at an argon pressure of 10 kbar. Electron microscopy, as well as single crystal X-ray diffraction studies show that the crystals are well ordered. The EDS analysis indicates the presence of a minor amount of other cations replacing Hg, Ba and Ca in the structure. Refined fractional coordinates and thermal parameters are given for a crystal of Hg-1223 type. Magnetic and resistive measurements show a Tc of 133 K for the Hg-1223 phase.

  15. A New Trapped Ion Clock Based on Hg-201(+)

    NASA Technical Reports Server (NTRS)

    Taghavi-Larigani, S.; Burt, E. A.; Lea, S. N.; Prestage, J. D.; Tjoelker, R. L.

    2009-01-01

    There are two stable odd isotopes of mercury with singly ionized hyperfine structure suitable for a microwave clock: Hg-199(+) and Hg-201(+). Virtually all trapped mercury ion clocks to date have used the 199 isotope. We have begun to investigate the viability of a trapped ion clock based on Hg-201(+). We have measured the unperturbed frequency of the (S-2)(sub 1/2) F = 1, m(sub F) = 0 to (S-2)(sub 1/2) F = 2, m(sub F) = 0 clock transition to be 29.9543658211(2) GHz. In this paper we describe initial measurements with Hg-201(+) and new applications to clocks and fundamental physics.

  16. Mercury isotope fractionation during ore retorting in the Almadén mining district, Spain

    USGS Publications Warehouse

    Gray, John E.; Pribil, Michael J.; Higueras, Pablo L.

    2013-01-01

    Almadén, Spain, is the world's largest mercury (Hg) mining district, which has produced over 250,000 metric tons of Hg representing about 30% of the historical Hg produced worldwide. The objective of this study was to measure Hg isotopic compositions of cinnabar ore, mine waste calcine (retorted ore), elemental Hg (Hg0(L)), and elemental Hg gas (Hg0(g)), to evaluate potential Hg isotopic fractionation. Almadén cinnabar ore δ202Hg varied from − 0.92 to 0.15‰ (mean of − 0.56‰, σ = 0.35‰, n = 7), whereas calcine was isotopically heavier and δ202Hg ranged from − 0.03‰ to 1.01‰ (mean of 0.43‰, σ = 0.44‰, n = 8). The average δ202Hg enrichment of 0.99‰ between cinnabar ore and calcines generated during ore retorting indicated Hg isotopic mass dependent fractionation (MDF). Mass independent fractionation (MIF) was not observed in any of the samples in this study. Laboratory retorting experiments of cinnabar also were carried out to evaluate Hg isotopic fractionation of products generated during retorting such as calcine, Hg0(L), and Hg0(g). Calcine and Hg0(L) generated during these retorting experiments showed an enrichment in δ202Hg of as much as 1.90‰ and 0.67‰, respectively, compared to the original cinnabar ore. The δ202Hg for Hg0(g) generated during the retorting experiments was as much as 1.16‰ isotopically lighter compared to cinnabar, thus, when cinnabar ore was roasted, the resultant calcines formed were isotopically heavier, whereas the Hg0(g) generated was isotopically lighter in Hg isotopes.

  17. Methylmercury (MeHg)

    Integrated Risk Information System (IRIS)

    Methylmercury ( MeHg ) ; CASRN 22967 - 92 - 6 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarci

  18. Method of preparing mercury with an arbitrary isotopic distribution

    DOEpatents

    Grossman, M.W.; George, W.A.

    1986-12-16

    This invention provides for a process for preparing mercury with a predetermined, arbitrary, isotopic distribution. In one embodiment, different isotopic types of Hg[sub 2]Cl[sub 2], corresponding to the predetermined isotopic distribution of Hg desired, are placed in an electrolyte solution of HCl and H[sub 2]O. The resulting mercurous ions are then electrolytically plated onto a cathode wire producing mercury containing the predetermined isotopic distribution. In a similar fashion, Hg with a predetermined isotopic distribution is obtained from different isotopic types of HgO. In this embodiment, the HgO is dissolved in an electrolytic solution of glacial acetic acid and H[sub 2]O. The isotopic specific Hg is then electrolytically plated onto a cathode and then recovered. 1 fig.

  19. Method of preparing mercury with an arbitrary isotopic distribution

    DOEpatents

    Grossman, Mark W.; George, William A.

    1986-01-01

    This invention provides for a process for preparing mercury with a predetermined, arbitrary, isotopic distribution. In one embodiment, different isotopic types of Hg.sub.2 Cl.sub.2, corresponding to the predetermined isotopic distribution of Hg desired, are placed in an electrolyte solution of HCl and H.sub.2 O. The resulting mercurous ions are then electrolytically plated onto a cathode wire producing mercury containing the predetermined isotopic distribution. In a similar fashion, Hg with a predetermined isotopic distribution is obtained from different isotopic types of HgO. In this embodiment, the HgO is dissolved in an electrolytic solution of glacial acetic acid and H.sub.2 O. The isotopic specific Hg is then electrolytically plated onto a cathode and then recovered.

  20. Supersymmetry and 198Hg

    NASA Astrophysics Data System (ADS)

    Bernards, Christian; Heinze, Stefan; Jolie, Jan; Fransen, Christoph; Linnemann, Andreas; Radeck, Désirée

    2009-01-01

    The energy spectrum and electromagnetic transition properties of the supermultiplet members with two proton fermions can be constructed using the dynamical Uv(6/12)⊗Uπ(6/4) extended supersymmetry. In order to investigate predictions of the two proton fermion—four neutron boson supermultiplet member 198Hg, an experiment with the HORUS cube γ-ray spectrometer at the Cologne TANDEM accelerator was performed using the 196Pt(α,2n)198Hg reaction. By analyzing γγ coincidence spectra and γγ angular correlations, the required experimental data—level and decay energies, level spins and multipole mixing ratios—could be obtained. For the low-energy states, the experimental data show good agreement with theory.

  1. Hg(+) Frequency Standards

    NASA Technical Reports Server (NTRS)

    Prestage, John D.; Tjoelker, Robert L.; Maleki, Lute

    2000-01-01

    In this paper we review the development of Hg(+) microwave frequency standards for use in high reliability and continuous operation applications. In recent work we have demonstrated short-term frequency stability of 3 x 10(exp -14)/nu(sub tau) when a cryogenic oscillator of stability 2-3 x 10(exp 15) was used a the local oscillator. The trapped ion frequency standard employs a Hg-202 discharge lamp to optically pump the trapped Hg(+)-199 clock ions and a helium buffer gas to cool the ions to near room temperature. We describe a small Hg(+) ion trap based frequency standard with an extended linear ion trap (LITE) architecture which separates the optical state selection region from the clock resonance region. This separation allows the use of novel trap configurations in the resonance region since no optical pumping is carried out there. A method for measuring the size of an ion cloud inside a linear trap with a 12-rod trap is currently being investigated. At approx. 10(exp -12), the 2nd order Doppler shift for trapped mercury ion frequency standards is one of the largest frequency offsets and its measurement to the 1% level would represent an advance in insuring the very long-term stability of these standards to the 10(exp -14) or better level. Finally, we describe atomic clock comparison experiments that can probe for a time variation of the fine structure constant, alpha = e(exp 2)/2(pi)hc, at the level of 10(exp -20)/year as predicted in some Grand Unified String Theories.

  2. Importance of Dissolved Neutral Hg-Sulfides, Energy Rich Organic Matter and total Hg Concentrations for Methyl Mercury Production in Sediments

    NASA Astrophysics Data System (ADS)

    Drott, A.; Skyllberg, U.

    2007-12-01

    Methyl mercury (MeHg) is the mercury form that biomagnifies to the greatest extent in aquatic food webs. Therefore information about factors determining MeHg concentrations is critical for accurate risk assessment of contaminated environments. The concentration of MeHg in wetlands and sediments is the net result of: 1) methylation rates, 2) demethylation rates, and 3) input/output processes. In this study, the main controls on Hg methylation rates and total concentrations of MeHg, were investigated at eight sites in Sweden with sediments that had been subjected to local Hg contamination either as Hg(0), or as phenyl-Hg. Sediments were selected to represent a gradient in total Hg concentration, temperature climate, salinity, primary productivity, and organic C content and quality. Most sediments were high in organic matter content due to wood fibre efflux from pulp and paper industry. The pore water was analysed for total Hg, MeHg, DOC, H2S(aq), pH, DOC, Cl and Br. The chemical speciation of Hg(II) and MeHg in pore water was calculated using equilibrium models. Potential methylation and demethylation rates in sediments were determined in incubation experiments at 23° C under N2(g) for 48 h, after addition of isotopically enriched 201Hg(II) and Me204Hg. In all surface (0-20 cm) sediments there was a significant (p<0.001) positive relationship between the experimentally determined specific potential methylation rate constant (Km, day-1) and % MeHg (concentrations of MeHg normalized to total Hg) in the sediment. This indicates that MeHg production overruled degradation and input/output processes of MeHg in surface sediments, and that % MeHg in surface sediments may be used as a proxy for net production of MeHg. To our knowledge, these are the first data showing significant positive relationships between short term (48 h) MeHg production and longer term accumulation of MeHg, across a range of sites with different properties (1). If MeHg was not normalized to total Hg

  3. Low-lying states of ruthenium isotopes within the nucleon pair approximation

    NASA Astrophysics Data System (ADS)

    Jiang, H.; Li, B.; Lei, Y.

    2016-05-01

    Low-lying states of even-even and odd-mass ruthenium isotopes with mass numbers from 95 to 102, including level schemes, electric quadrupole and magnetic dipole moments, and E 2 transition rates, are studied within the framework of the nucleon pair approximation (NPA) of the shell model, by using the phenomenological pairing plus quadrupole interactions. Good agreement is obtained between the calculated results and experimental data. The interesting behaviors of g (J1+) factors versus nuclear spin J (and mass number A ) in even-even Ru-10296 nuclei are analyzed. The dominant configurations of yrast low-lying states in odd-mass Ru-10195 isotopes are discussed in the collective nucleon-pair subspace. The calculated electric quadrupole moments and magnetic moments of low-lying states, many of which have not yet been measured for these nuclei, are useful for future studies.

  4. Hg-Mask Coronagraph

    NASA Astrophysics Data System (ADS)

    Bourget, P.; Veiga, C. H.; Vieira Martins, R.; Assus, P.; Colas, F.

    In order to optimize the occulting process of a Lyot coronagraph and to provide a high dynamic range imaging, a new kind of occulting disk has been developed at the National Observatory of Rio de Janeiro. A mercury (Hg) drop glued onto an optical window by molecular cohesion and compressed by a pellicle film is used as the occulting disk. The minimum of the superficial tension potential function provides an optical precision (lambda/100) of the toric free surface of the mercury. This process provides a size control for the adaptation to the seeing conditions and to the apparent diameter of a resolved object, and in the case of adaptive optics, to the Airy diameter fraction needed. The occultation is a three dimensional process near the focal plane on the toric free surface that provides an apodization of the occultation. The Hg-Mask coronagraph has been projected for astrometric observations of faint satellites near to Jovian planets and works since 2000 at the 1.6 m telescope of the Pico dos Dias Observatory (OPD - Brazil).

  5. Fractionation of Mercury Stable Isotopes during Microbial Methylmercury Production by Iron- and Sulfate-Reducing Bacteria.

    PubMed

    Janssen, Sarah E; Schaefer, Jeffra K; Barkay, Tamar; Reinfelder, John R

    2016-08-01

    The biological production of monomethylmercury (MeHg) in soils and sediments is an important factor controlling mercury (Hg) accumulation in aquatic and terrestrial food webs. In this study we examined the fractionation of Hg stable isotopes during Hg methylation in nongrowing cultures of the anaerobic bacteria Geobacter sulfurreducens PCA and Desulfovibrio desulfuricans ND132. Both organisms showed mass-dependent, but no mass-independent fractionation of Hg stable isotopes during Hg methylation. Despite differences in methylation rates, the two bacteria had similar Hg fractionation factors (αr/p = 1.0009 and 1.0011, respectively). Unexpectedly, δ(202)Hg values of MeHg for both organisms were 0.4‰ higher than the value of initial inorganic Hg after about 35% of inorganic Hg had been methylated. These results indicate that a (202)Hg-enriched pool of inorganic Hg was preferentially utilized as a substrate for methylation by these organisms, but that multiple intra- and/or extracellular pools supplied inorganic Hg for biological methylation. Understanding the controls of the Hg stable isotopic composition of microbially produced MeHg is important to identifying bioavailable Hg in natural systems and the interpretation of Hg stable isotopes in aquatic food webs. PMID:27392249

  6. Mercury Isotopic Evidence for Contrasting Mercury Transport Pathways to Coastal versus Open Ocean Fisheries (Invited)

    NASA Astrophysics Data System (ADS)

    Blum, J. D.; Senn, D. B.; Chesney, E. J.; Bank, M. S.; Maage, A.; Shine, J. P.

    2009-12-01

    Mercury stable isotopes provide a new method for tracing the sources and chemical transformations of Hg in the environment. In this study we used Hg isotopes to investigate Hg sources to coastal versus migratory open-ocean species of fish residing in the northern Gulf of Mexico (nGOM). We report Hg isotope ratios as δ202Hg (mass dependent fractionation relative to NIST 3133) and Δ201Hg (mass independent fractionation of odd isotopes). In six coastal and two open ocean species (blackfin and yellowfin tuna), Hg isotopic compositions fell into two non-overlapping ranges. The tuna had significantly higher δ202Hg (0.1 to 0.7‰) and Δ201Hg (1.0 to 2.2‰) than the coastal fish (δ202Hg = 0 to -1.0‰; Δ201Hg = 0.4 to 0.5‰). The observations can be best explained by largely disconnected food webs with isotopically distinct MeHg sources. The ratio Δ199Hg/Δ201Hg in nGOM fish is 1.30±0.10 which is consistent with laboratory studies of photochemical MeHg degradation and with ratios measured in freshwater fish (Bergquist and Blum, 2007). The magnitude of mass independent fractionation of Hg in the open-ocean fish suggests that this source of MeHg was subjected to extensive photodegradation (~50%) before entering the base of the open-ocean food web. Given the Mississippi River’s large, productive footprint in the nGOM and the potential for exporting prey and MeHg to the adjacent oligotrophic GOM, the different MeHg sources are noteworthy and consistent with recent evidence in other systems of important open-ocean MeHg sources. Bergquist, B. A. and Blum, J. D., 2007. Mass-dependent and -independent fractionation of Hg isotopes by photoreduction in aquatic systems. Science 318, 417-420.

  7. THE DEVELOPMENT OF A PREDICTIVE TOLL USING LARGEMOUTH BASS (MICROPTERUS SALMOIDES) SCALES TO ESTIMATE MERCURY (HG) CONCENTRATIONS AND STABLE-NITROGEN (15N/14N) ISOTOPE RATIOS IN FISH MUSCLE TISSUE

    EPA Science Inventory

    Knowledge of the trophic structure of biota in aquatic sites offers potential for the construction of models to allow the prediction of contaminant bioaccumulation. Measurements of trophic position have been conducted using stable-nitrogen isotope ratios ( 15N) measured in fish m...

  8. Mercury Stable Isotopic Composition of Monomethylmercury in Estuarine Sediments and Pure Cultures of Mercury Methylating Bacteria

    NASA Astrophysics Data System (ADS)

    Janssen, S.; Johnson, M. W.; Barkay, T.; Blum, J. D.; Reinfelder, J. R.

    2014-12-01

    Tracking monomethylmercury (MeHg) from its source in soils and sediments through various environmental compartments and transformations is critical to understanding its accumulation in aquatic and terrestrial food webs. Advances in the field of mercury (Hg) stable isotopes have allowed for the tracking of discrete Hg sources and the examination of photochemical and bacterial transformations. Despite analytical advances, measuring the Hg stable isotopic signature of MeHg in environmental samples or laboratory experiments remains challenging due to difficulties in the quantitative separation of MeHg from complex matrices with high concentrations of inorganic Hg. To address these challenges, we have developed a MeHg isolation method for sediments and bacterial cultures which involves separation by gas chromatography. The MeHg eluting from the GC is passed through a pyrolysis column and purged onto a gold amalgam trap which is then desorbed into a final oxidizing solution. A MeHg reference standard carried through our separation process retained its isotopic composition within 0.02 ‰ for δ202Hg, and for native estuarine sediments, MeHg recoveries were 80% to 100%. For sediment samples from the Hackensack and Passaic Rivers (New Jersey, USA), δ202Hg values for MeHg varied from -1.2 to +0.58 ‰ (relative to SRM 3133) and for individual samples were significantly different from that of total Hg (-0.38 ± 0.06 ‰). No mass independent fractionation was observed in MeHg or total Hg from these sediments. Pure cultures of Geobacter sulfurreducens, grown under fermentative conditions showed preferential enrichment of lighter isotopes (lower δ202Hg) during Hg methylation. The Hg stable isotope signatures of MeHg in sediments and laboratory methylation experiments will be discussed in the context of the formation and degradation of MeHg in the environment and the bioaccumulation of MeHg in estuarine food webs.

  9. The Upside to Hg-DOM Associations for Water Quality: Removal of Hg from Solution Using Coagulaion with Metal-Based Salts

    NASA Astrophysics Data System (ADS)

    Henneberry, Y.; Kraus, T. E.; Fleck, J.; Krabbenhoft, D. P.; Horwath, W. R.

    2011-12-01

    This study assessed the potential use of metal-based coagulants to remove dissolved mercury (Hg) from natural waters and provides information regarding the importance of Hg associations with the dissolved organic matter (DOM) fraction and metal hydroxides. Previous research indicated coagulants were not effective at removing Hg from solution; however those studies used high concentrations of Hg, which did not reflect naturally occurring concentrations of Hg. Filtered water collected from an agricultural drain in the Sacramento-San Joaquin Delta (Delta) was treated with three industrial-grade coagulants (ferric chloride, ferric sulfate, and polyaluminum chloride) to determine their efficacy in removing both inroganic (IHg) and methylmercury (MeHg) from the water column. The Delta suffers from elevated surface water Hg concentrations and as a result is listed as an imparied water body. Coagulants removed up to 85% of DOM from solution. In the absence of DOM, all three coagulants released IHg into solution, however in the presence of DOM the coagulants removed up to 97% of IHg and 80% of MeHg. Results suggest that the removal of Hg is mediated by DOM-coagulant interactions. There was a preferential association of IHg with the more aromatic, higher molecular weight fraction of DOM but no such relationship was found for MeHg. This study offers new fundamental insights regarding large-scale removal of Hg at environmentally relevant concentrations. Research using isotopically labeled Hg is providing insight into whether coagulation can remove recently added Hg (e.g. atmospheric deposition) from solution and whether once formed, the floc can remove additional Hg from the water column.

  10. Assessing sources of human methylmercury exposure using stable mercury isotopes.

    PubMed

    Li, Miling; Sherman, Laura S; Blum, Joel D; Grandjean, Philippe; Mikkelsen, Bjarni; Weihe, Pál; Sunderland, Elsie M; Shine, James P

    2014-01-01

    Seafood consumption is the primary route of methylmercury (MeHg) exposure for most populations. Inherent uncertainties in dietary survey data point to the need for an empirical tool to confirm exposure sources. We therefore explore the utility of Hg stable isotope ratios in human hair as a new method for discerning MeHg exposure sources. We characterized Hg isotope fractionation between humans and their diets using hair samples from Faroese whalers exposed to MeHg predominantly from pilot whales. We observed an increase of 1.75‰ in δ(202)Hg values between pilot whale muscle tissue and Faroese whalers' hair but no mass-independent fractionation. We found a similar offset in δ(202)Hg between consumed seafood and hair samples from Gulf of Mexico recreational anglers who are exposed to lower levels of MeHg from a variety of seafood sources. An isotope mixing model was used to estimate individual MeHg exposure sources and confirmed that both Δ(199)Hg and δ(202)Hg values in human hair can help identify dietary MeHg sources. Variability in isotopic signatures among coastal fish consumers in the Gulf of Mexico likely reflects both differences in environmental sources of MeHg to coastal fish and uncertainty in dietary recall data. Additional data are needed to fully refine this approach for individuals with complex seafood consumption patterns. PMID:24967674

  11. Thermal and Isotopic Anomalies when pd Cathodes are Electrolyzed in Electrolytes Containing Th-Hg Salts Dissolved at Micromolar Concentration in C2H5OD/D2O Mixtures

    NASA Astrophysics Data System (ADS)

    Celani, F.; Spallone, A.; Righi, E.; Trenta, G.; Catena, C.; D'Agostaro, G.; Quercia, P.; Andreassi, V.; Marini, P.; di Stefano, V.; Nakamura, M.; Mancini, A.; Sona, P. G.; Fontana, F.; Gamberale, L.; Garbelli, D.; Falcioni, F.; Marchesini, M.; Novaro, E.; Mastromatteo, U.

    2005-12-01

    Discussed in this paper is the evolution of work that started by using the M. Fleischmann and S. Pons method and ended by using thin palladium wires electrolyzed in an electrolyte consisting of slightly acidic heavy alcohol-water solution containing thorium (Th) and mercury (Hg) salts at micromolar concentrations. The resulting large and dynamic loading of the Pd wires was studied. The recent use of thorium instead of strontium resulted in thermal anomalies and detection of new elements in larger amounts. The results with Sr are qualitatively in agreement with what was found by Y. Iwamura (Mitsubishi Heavy Industries) using multilayers of Pd-CaO-Pd-Sr in flowing deuterium gas. Most results seem to be in agreement with a "multi-body resonance fusion of deuterons" model recently developed by A.Takahashi (Osaka University).

  12. Mercury isotope signatures in contaminated sediments as a tracer for local industrial pollution sources.

    PubMed

    Wiederhold, Jan G; Skyllberg, Ulf; Drott, Andreas; Jiskra, Martin; Jonsson, Sofi; Björn, Erik; Bourdon, Bernard; Kretzschmar, Ruben

    2015-01-01

    Mass-dependent fractionation (MDF) and mass-independent fractionation (MIF) may cause characteristic isotope signatures of different mercury (Hg) sources and help understand transformation processes at contaminated sites. Here, we present Hg isotope data of sediments collected near industrial pollution sources in Sweden contaminated with elemental liquid Hg (mainly chlor-alkali industry) or phenyl-Hg (paper industry). The sediments exhibited a wide range of total Hg concentrations from 0.86 to 99 μg g(-1), consisting dominantly of organically-bound Hg and smaller amounts of sulfide-bound Hg. The three phenyl-Hg sites showed very similar Hg isotope signatures (MDF δ(202)Hg: -0.2‰ to -0.5‰; MIF Δ(199)Hg: -0.05‰ to -0.10‰). In contrast, the four sites contaminated with elemental Hg displayed much greater variations (δ(202)Hg: -2.1‰ to 0.6‰; Δ(199)Hg: -0.19‰ to 0.03‰) but with distinct ranges for the different sites. Sequential extractions revealed that sulfide-bound Hg was in some samples up to 1‰ heavier in δ(202)Hg than organically-bound Hg. The selectivity of the sequential extraction was tested on standard materials prepared with enriched Hg isotopes, which also allowed assessing isotope exchange between different Hg pools. Our results demonstrate that different industrial pollution sources can be distinguished on the basis of Hg isotope signatures, which may additionally record fractionation processes between different Hg pools in the sediments. PMID:25437501

  13. A new trapped ion atomic clock based on 201Hg+.

    PubMed

    Burt, Eric A; Taghavi-Larigani, Shervin; Tjoelker, Robert L

    2010-03-01

    High-resolution spectroscopy has been performed on the ground-state hyperfine transitions in trapped (201)Hg+ ions as part of a program to investigate the viability of (201)Hg+ for clock applications. Part of the spectroscopy work was directed at magnetic-field-sensitive hyperfine lines with delta m(F) = 0, which allow accurate Doppler-free measurement of the magnetic field experienced by the trapped ions. Although it is possible to measure Doppler-free magnetic-field-sensitive transitions in the commonly used clock isotope, (199)Hg+, it is more difficult. In this paper, we discuss how this (199)Hg+ feature may be exploited to produce a more stable clock or one requiring less magnetic shielding in environments with magnetic field fluctuations far in excess of what is normally found in the laboratory. We have also determined that in discharge-lamp-based trapped mercury ion clocks, the optical pumping time for (201)Hg+ is about 3 times shorter than that of (199)Hg+ This can be used to reduce dead time in the interrogation cycle for these types of clocks, thereby reducing the impact of local oscillator noise aliasing effects. PMID:20211781

  14. Final Project Report: "Exploratory Research: Mercury Stable Isotopes as Indicators of the Biogeochemical Cycling of Mercury"

    SciTech Connect

    Johnson, Thomas M

    2012-08-01

    This is the final project report for award DE-SC0005351, which supported the research project "Exploratory Research: Mercury Stable Isotopes as Indicators of the Biogeochemical Cycling of Mercury. "This exploratory project investigated the use of mercury (Hg) stable isotope measurements as a new approach to study how Hg moves and changes its chemical form in environmental systems, with particular focus on the East Fork of Poplar Creek (EFPC) near the DOE Y-12 plant (a Hg contamination source). This study developed analytical methods and collected pilot data that have set the stage for more detailed studies and have begun to provide insights into Hg movement and chemical changes. The overall Hg stable isotope approach was effective. The Hg isotope analysis methods yielded high-precision measurements of the sediment, water, and fish samples analyzed; quality control measures demonstrated the precision. The pilot data show that the 202Hg/198Hg, 199Hg/198Hg, and 201Hg/198Hg isotope ratios vary in this system. 202Hg/198Hg ratios of the Hg released from the Y-12 plant are relatively high, and those of the regional Hg background in soils and river sediments are significantly lower. Unfortunately, 202Hg/198Hg differences that might have been useful to distinguish early Hg releases from later releases were not observed. However, 202Hg/198Hg ratios in sediments do provide insights into chemical transformations that may occur as Hg moves through the system. Furthermore, 199Hg/198Hg and 201Hg/198Hg ratio analyses of fish tissues indicate that the effects of sunlight-driven chemical reactions on the Hg that eventually ends up in EFPC fish are measureable, but small. These results provide a starting point for a more detailed study (already begun at Univ. of Michigan) that will continue Hg isotope ratio work aimed at improving understanding of how Hg moves, changes chemically, and does or does not take on more highly toxic forms in the Oak Ridge area. This work also benefits

  15. Natural mercury isotope variation in coal deposits and organic soils

    SciTech Connect

    Abir, Biswas; Joel D. Blum; Bridget A. Bergquist; Gerald J. Keeler; Zhouqing Xie

    2008-11-15

    There is a need to distinguish among sources of Hg to the atmosphere in order to more fully understand global Hg pollution. In this study we investigate whether coal deposits within the United States, China, and Russia-Kazakhstan, which are three of the five greatest coal-producing regions, have diagnostic Hg isotopic fingerprints that can be used to discriminate among Hg sources. We also investigate the Hg isotopic composition of modern organic soil horizons developed in areas distant from point sources of Hg in North America. Mercury stored in coal deposits displays a wide range of both mass dependent fractionation and mass independent fractionation. {delta}{sup 202}Hg varies in coals by 3{per_thousand} and {Delta}{sup 201}Hg varies by 0.9{per_thousand}. Combining these two Hg isotope signals results in what may be a unique isotopic 'fingerprint' for many coal deposits. Mass independent fractionation of mercury has been demonstrated to occur during photochemical reactions of mercury. This suggests that Hg found in most coal deposits was subjected to photochemical reduction near the Earth's surface prior to deposition. The similarity in MDF and MIF of modern organic soils and coals from North America suggests that Hg deposition from coal may have imprinted an isotopic signature on soils. This research offers a new tool for characterizing mercury inputs from natural and anthropogenic sources to the atmosphere and provides new insights into the geochemistry of mercury in coal and soils. 35 refs., 2 figs., 1 tab.

  16. Fractionated Mercury Isotopes in Fish: The Effects of Nuclear Mass, Spin, and Volume

    NASA Astrophysics Data System (ADS)

    Das, R.; Odom, A. L.

    2007-12-01

    Mercury is long known as a common environmental contaminant. In methylated form it is even more toxic and the methylation process is facilitated by microbial activities. Methyl mercury easily crosses cell membrane and accumulates in soft tissues of fishes and finally biomagnifies with increasing trophic levels. Natural variations in the isotopic composition of mercury have been reported and such variations have emphasized mass dependent fractionations, while theory and laboratory experiments indicate that mass-independent isotopic fractionation (MIF) effects are likely to be found as well. This study focuses on the MIF of mercury isotopes in the soft tissues of fishes. Samples include both fresh water and marine fish, from different continents and oceans. Approximately 1 gm of fish soft tissue was dissolved in 5 ml of conc. aqua regia for 24 hrs and filtered through a ¬¬¬100 μm filter paper and diluted with DI water. Hg is measured as a gaseous phase generated by reduction of the sample with SnCl2 in a continuous- flow cold-vapor generator connected to a Thermo-Finnigan Neptune MC-ICPMS. To minimize instrumental fractionation isotope ratios were measured by sample standard bracketing and reported as δ‰ relative to NIST SRM 3133 Hg standard where δAHg = [(A Hg/202Hg)sample/(A Hg/202Hg)NIST313] -1 ×1000‰. In this study we have measured the isotope ratios 198Hg/202Hg, 199Hg/202Hg, 200Hg/202Hg, 201Hg/202Hg and 204Hg/202Hg. In all the fish samples δ198Hg, δ200Hg, δ202Hg, δ204Hg define a mass- dependent fractionation sequence, where as the δ199Hg and δ201Hg depart from the mass- dependent fractionation line and indicate an excess of the odd-N isotopes. The magnitude of the deviation (ΔAHg where A=199 or 201) as obtained by difference between the measured δ199Hg and δ201Hg of the samples and the value obtained by linear scaling defined by the even-N isotopes ranges from approximately 0.2 ‰ to 3‰. The ratios of Δ199Hg /Δ201Hg range from 0.8 to 1

  17. Mercury Isotope Study of Sources and Exposure Pathways of Methylmercury in Estuarine Food Webs in the Northeastern U.S.

    PubMed Central

    2015-01-01

    We measured mercury (Hg) isotope ratios in sediments and various estuarine organisms (green crab, blue mussel, killifish, eider) to investigate methylmercury (MMHg) sources and exposure pathways in five Northeast coast (U.S.) estuaries. The mass independent Hg isotopic compositions (MIF; Δ199Hg) of the sediments were linearly correlated with the sediment 1/Hg concentrations (Δ199Hg: r2 = 0.77, p < 0.05), but the mass dependent isotope compositions (MDF; δ202Hg) were not (r2 = 0.26, p = 0.16), reflecting inputs of anthropogenic Hg sources with varying δ202Hg. The estuarine organisms all display positive Δ199Hg values (0.21 to 0.98 ‰) indicating that MMHg is photodegraded to varying degrees (5–12%) prior to entry into the food web. The δ202Hg and Δ199Hg values of most organisms can be explained by a mixture of MMHg and inorganic Hg from sediments. At one contaminated site mussels have anomalously high δ202Hg, indicating exposure to a second pool of MMHg, compared to sediment, crabs and fish. Eiders have similar Δ199Hg as killifish but much higher δ202Hg, suggesting that there is an internal fractionation of δ202Hg in birds. Our study shows that Hg isotopes can be used to identify multiple anthropogenic inorganic Hg and MMHg sources and determine the degree of photodegradation of MMHg in estuarine food webs. PMID:25116221

  18. Mercury isotope study of sources and exposure pathways of methylmercury in estuarine food webs in the Northeastern U.S.

    PubMed

    Kwon, Sae Yun; Blum, Joel D; Chen, Celia Y; Meattey, Dustin E; Mason, Robert P

    2014-09-01

    We measured mercury (Hg) isotope ratios in sediments and various estuarine organisms (green crab, blue mussel, killifish, eider) to investigate methylmercury (MMHg) sources and exposure pathways in five Northeast coast (U.S.) estuaries. The mass independent Hg isotopic compositions (MIF; Δ(199)Hg) of the sediments were linearly correlated with the sediment 1/Hg concentrations (Δ(199)Hg: r(2) = 0.77, p < 0.05), but the mass dependent isotope compositions (MDF; δ(202)Hg) were not (r(2) = 0.26, p = 0.16), reflecting inputs of anthropogenic Hg sources with varying δ(202)Hg. The estuarine organisms all display positive Δ(199)Hg values (0.21 to 0.98 ‰) indicating that MMHg is photodegraded to varying degrees (5-12%) prior to entry into the food web. The δ(202)Hg and Δ(199)Hg values of most organisms can be explained by a mixture of MMHg and inorganic Hg from sediments. At one contaminated site mussels have anomalously high δ(202)Hg, indicating exposure to a second pool of MMHg, compared to sediment, crabs and fish. Eiders have similar Δ(199)Hg as killifish but much higher δ(202)Hg, suggesting that there is an internal fractionation of δ(202)Hg in birds. Our study shows that Hg isotopes can be used to identify multiple anthropogenic inorganic Hg and MMHg sources and determine the degree of photodegradation of MMHg in estuarine food webs. PMID:25116221

  19. {beta} decay of odd-A As to Ge isotopes in the interacting boson-fermion model

    SciTech Connect

    Brant, S.; Yoshida, N.; Zuffi, L.

    2004-11-01

    The structure of odd-mass isotopes of As and Ge is described in the framework of the proton-neutron interacting boson-fermion model. The energy levels and the electromagnetic properties of {sup 69,71,73}As and {sup 69,71,73}Ge are calculated and compared with the experiment. The {beta}-decay rates from the As isotopes to the Ge isotopes are calculated. The calculated decays tend to be stronger than the observed ones. This may indicate a mixture of components outside the model space in the wave functions of actual nuclei. The effect of the higher-order terms in the decay operators seems small.

  20. Historical Records of Mercury Stable Isotopes in Sediments of Tibetan Lakes.

    PubMed

    Yin, Runsheng; Feng, Xinbin; Hurley, James P; Krabbenhoft, David P; Lepak, Ryan F; Kang, Shichang; Yang, Handong; Li, Xiangdong

    2016-01-01

    The Tibetan Plateau (TP), known as the "Third Pole", is a critical zone for atmospheric mercury (Hg) deposition. Increasing anthropogenic activities in the globe leads to environmental changes, which may affect the loading, transport and deposition of Hg in the environment. However, the deposition history and geochemical cycling of Hg in the TP is still uncertain. Our records of Hg and Hg isotopes in sediment profiles of the two largest lakes in the TP, Lake Qinghai and Nam Co, show increased Hg influx since last century, with the maximum Hg influx enrichment ratios of 5.4 and 3.5 in Lake Qinghai and Nam Co, respectively. Shifts in negative δ (202)Hg in Lake Qinghai (-4.55 to -3.15‰) and Nam Co (-5.04 to -2.16‰) indicate increased atmospheric Hg deposition through rainfall, vegetation and runoff of soils. Mass independent fractionation of both even-Hg (∆ (200)Hg: +0.05 to +0.10‰) and odd-Hg (∆ (199)Hg: +0.12 to +0.31‰) isotopes were observed. Positive Δ (200)Hg suggest high proportion of precipitation-derived Hg in the TP, whereas the positive Δ (199)Hg results from Hg(II) photo-reduction. Both lakes show increasing Δ (199)Hg since the 1900 s, and we conclude that with the decrease of ice duration, Hg(II) photo-reduction may have been accelerated in these TP lakes. PMID:26996936

  1. Unusual fractionation of both odd and even mercury isotopes in precipitation from Peterborough, ON, Canada

    NASA Astrophysics Data System (ADS)

    Chen, JiuBin; Hintelmann, Holger; Feng, XinBin; Dimock, Brian

    2012-08-01

    Once released into the atmosphere, mercury (Hg) is subject to long-range transport and a series of physico-chemical reactions before reentering terrestrial ecosystems. Though impressive progress has been made in understanding all aspects of Hg behavior in the atmosphere, many processes involved in the transformation and deposition of atmospheric Hg remain unidentified and source attribution is still an enormous challenge. Here, we examine the isotopic composition of Hg in precipitation collected during 2010 in Peterborough, ON, Canada and combine data on seasonal variations of mass-dependent (MDF) and mass-independent (MIF) fractionation with meteorological back-trajectory calculations to identify the Hg sources and to decipher Hg atmospheric transformation reactions. All precipitation samples displayed significant MDF (δ202Hg between -0.02‰ and -1.48‰) and MIF of odd isotopes (Δ199Hg varying from -0.29‰ to 1.13‰). We also report for the first time a seasonal variation of MIF of even Hg isotopes (Δ200Hg) in wet precipitation. Our results may suggest that photoreduction in droplets or on the surface layer of snow crystals induces odd Hg isotope anomalies, while mass independent fractionation of 200Hg is probably triggered by photo-initiated oxidation occurring on aerosol or solid surfaces in the tropopause. The observed seasonal variation of even Hg isotope MIF (Δ200Hg decrease with ambient temperature) is possibly a powerful tool for meteorological research and may aid in monitoring related climate changes.

  2. Application of mercury isotopes for tracing trophic transfer and internal distribution of mercury in marine fish feeding experiments.

    PubMed

    Kwon, Sae Yun; Blum, Joel D; Chirby, Michelle A; Chesney, Edward J

    2013-10-01

    Feeding experiments were performed to investigate mercury (Hg) isotope fractionation during trophic transfer and internal distribution of total Hg (THg) in marine fish on exposure to natural seafood. Young-of-the-year amberjack (Seriola dumerili) were fed with either blackfin tuna (Thunnus atlanticus; 2647 ng/g THg) or brown shrimp (Farfantepenaeus aztecus; 25.1 ng/g THg) for 80 d or 50 d, respectively, and dissected for muscle, liver, kidney, brain, and blood. After 30 d of tuna consumption, Hg isotopes (δ(202) Hg and Δ(199)Hg) of the amberjack organs shifted to the tuna value (δ(202)Hg = 0.55‰, Δ(199)Hg = 1.54‰,), demonstrating the absence of Hg isotope fractionation. When amberjack were fed a shrimp diet, there was an initial mixing of the amberjack organs toward the shrimp value (δ(202)Hg = -0.48‰, Δ(199)Hg = 0.32‰), followed by a cessation of further shifts in Δ(199)Hg and a small shift in δ(202)Hg. The failure of Δ(199)Hg to reach the shrimp value can be attributed to a reduction in Hg bioaccumulation from shrimp resulting from feeding inhibition and the δ(202)Hg shift can be attributed to a small internal fractionation during excretion. Given that the feeding rate and Hg concentration of the diet can influence internal Hg isotope distribution, these parameters must be considered in biosentinel fish studies. PMID:23787815

  3. Mercury isotopes in a forested ecosystem: Implications for air-surface exchange dynamics and the global mercury cycle

    NASA Astrophysics Data System (ADS)

    Demers, Jason D.; Blum, Joel D.; Zak, Donald R.

    2013-01-01

    ABSTRACT Forests mediate the biogeochemical cycling of mercury (Hg) between the atmosphere and terrestrial ecosystems; however, there remain many gaps in our understanding of these processes. Our objectives in this study were to characterize Hg isotopic composition within forests, and use natural abundance stable Hg isotopes to track sources and reveal mechanisms underlying the cycling of Hg. We quantified the stable Hg isotopic composition of foliage, forest floor, mineral soil, precipitation, and total gaseous mercury (THg(g)) in the atmosphere and in evasion from soil, in 10-year-old aspen forests at the Rhinelander FACE experiment in northeastern Wisconsin, USA. The effect of increased atmospheric CO2 and O3 concentrations on Hg isotopic composition was small relative to differences among forest ecosystem components. Precipitation samples had δ202Hg values of -0.74 to 0.06‰ and ∆199Hg values of 0.16 to 0.82‰. Atmospheric THg(g) had δ202Hg values of 0.48 to 0.93‰ and ∆199Hg values of -0.21 to -0.15‰. Uptake of THg(g) by foliage resulted in a large (-2.89‰) shift in δ202Hg values; foliage displayed δ202Hg values of -2.53 to -1.89‰ and ∆199Hg values of -0.37 to -0.23‰. Forest floor samples had δ202Hg values of -1.88 to -1.22‰ and ∆199Hg values of -0.22 to -0.14‰. Mercury isotopes distinguished geogenic sources of Hg and atmospheric derived sources of Hg in soil, and showed that precipitation Hg only accounted for ~16% of atmospheric Hg inputs. The isotopic composition of Hg evasion from the forest floor was similar to atmospheric THg(g); however, there were systematic differences in δ202Hg values and MIF of even isotopes (∆200Hg and ∆204Hg). Mercury evasion from the forest floor may have arisen from air-surface exchange of atmospheric THg(g), but was not the emission of legacy Hg from soils, nor re-emission of wet-deposition. This implies that there was net atmospheric THg(g) deposition to the forest soils. Furthermore, MDF of

  4. Isotopic Composition of Atmospheric Mercury in China: New Evidence for Sources and Transformation Processes in Air and in Vegetation.

    PubMed

    Yu, Ben; Fu, Xuewu; Yin, Runsheng; Zhang, Hui; Wang, Xun; Lin, Che-Jen; Wu, Chuansheng; Zhang, Yiping; He, Nannan; Fu, Pingqing; Wang, Zifa; Shang, Lihai; Sommar, Jonas; Sonke, Jeroen E; Maurice, Laurence; Guinot, Benjamin; Feng, Xinbin

    2016-09-01

    The isotopic composition of atmospheric total gaseous mercury (TGM) and particle-bound mercury (PBM) and mercury (Hg) in litterfall samples have been determined at urban/industrialized and rural sites distributed over mainland China for identifying Hg sources and transformation processes. TGM and PBM near anthropogenic emission sources display negative δ(202)Hg and near-zero Δ(199)Hg in contrast to relatively positive δ(202)Hg and negative Δ(199)Hg observed in remote regions, suggesting that different sources and atmospheric processes force the mass-dependent fractionation (MDF) and mass-independent fractionation (MIF) in the air samples. Both MDF and MIF occur during the uptake of atmospheric Hg by plants, resulting in negative δ(202)Hg and Δ(199)Hg observed in litter-bound Hg. The linear regression resulting from the scatter plot relating the δ(202)Hg to Δ(199)Hg data in the TGM samples indicates distinct anthropogenic or natural influences at the three study sites. A similar trend was also observed for Hg accumulated in broadleaved deciduous forest foliage grown in areas influenced by anthropogenic emissions. The relatively negative MIF in litter-bound Hg compared to TGM is likely a result of the photochemical reactions of Hg(2+) in foliage. This study demonstrates the diagnostic stable Hg isotopic composition characteristics for separating atmospheric Hg of different source origins in China and provides the isotopic fractionation clues for the study of Hg bioaccumulation. PMID:27485289

  5. A review of isotopic composition as an indicator of the natural and anthropogenic behavior of mercury

    USGS Publications Warehouse

    Ridley, W.I.; Stetson, S.J.

    2006-01-01

    There are seven stable isotopes of Hg that can be fractionated as a result of inorganic and organic interactions. Important inorganic reactions involve speciation changes resulting from variations in environmental redox conditions, and phase changes resulting from variations in temperature and/or atmospheric pressure. Important organic reactions include methylation and demethylation, reactions that are bacterially mediated, and complexing with organic anions in soils. The measurement of Hg isotopes by multi-collector-inductively coupled plasma-mass spectrometry (MC-ICP-MS) is now sufficiently precise and sensitive that it is potentially possible to develop the systematics of Hg isotopic fractionation. This provides an opportunity to evaluate the utility of Hg isotopes in identifying source processes, transport mechanisms, and sinks. New values are provided for, 201Hg/198Hg, 200Hg/198Hg, 199Hg/198Hg for three standard materials (IRMM-AE639, SRM 1641c, SRM 3133) that can be used to make inter-laboratory data comparisons, and these values are tabulated with published isotopic information. Overall, the isotopic data for these standards agree to approximately 0.2???. The paper reviews Hg isotope studies that deal with hydrothermal ore deposits, sediments, coal and organic complexing. ?? 2006 Elsevier Ltd. All rights reserved.

  6. Absence of fractionation of mercury isotopes during trophic transfer of methylmercury to freshwater fish in captivity

    PubMed Central

    Kwon, Sae Yun; Blum, Joel D; Carvan, Michael J; Basu, Niladri; Head, Jessica A; Madenjian, Charles P; David, Solomon R

    2015-01-01

    We performed two controlled experiments to determine the amount of mass-dependent and mass-independent fractionation (MDF and MIF) of methylmercury (MeHg) during trophic transfer into fish. In Experiment 1, juvenile yellow perch (Perca flavescens) were raised in captivity on commercial food pellets and then their diet was either maintained on un-amended food pellets (0.1 µg/g MeHg), or was switched to food pellets with 1.0 µg/g or 4.0 µg/g of added MeHg, for a period of 2 months. The difference in δ202Hg (MDF) and Δ199Hg (MIF) between fish tissues and food pellets with added MeHg were within the analytical uncertainty (δ202Hg; 0.07 ‰, Δ199Hg; 0.06 ‰) indicating no isotope fractionation. In Experiment 2, lake trout (Salvelinus namaycush) were raised in captivity on food pellets, and then shifted to a diet of bloater (Coregonus hoyi) for 6 months. The δ202Hg and Δ199Hg of the lake trout equaled the isotopic composition of the bloater after 6 months, reflecting re-equilibration of the Hg isotopic composition of the fish to new food sources and a lack of isotope fractionation during trophic transfer. We suggest that the stable Hg isotope ratios in fish can be used to trace environmental sources of Hg in aquatic ecosystems. PMID:22681311

  7. Absence of fractionation of mercury isotopes during trophic transfer of methylmercury to freshwater fish in captivity.

    PubMed

    Kwon, Sae Yun; Blum, Joel D; Carvan, Michael J; Basu, Niladri; Head, Jessica A; Madenjian, Charles P; David, Solomon R

    2012-07-17

    We performed two controlled experiments to determine the amount of mass-dependent and mass-independent fractionation (MDF and MIF) of methylmercury (MeHg) during trophic transfer into fish. In experiment 1, juvenile yellow perch (Perca flavescens) were raised in captivity on commercial food pellets and then their diet was either maintained on unamended food pellets (0.1 μg/g MeHg) or was switched to food pellets with 1.0 μg/g or 4.0 μg/g of added MeHg, for a period of 2 months. The difference in δ(202)Hg (MDF) and Δ(199)Hg (MIF) between fish tissues and food pellets with added MeHg was within the analytical uncertainty (δ(202)Hg, 0.07 ‰; Δ(199)Hg, 0.06 ‰), indicating no isotope fractionation. In experiment 2, lake trout (Salvelinus namaycush) were raised in captivity on food pellets and then shifted to a diet of bloater (Coregonus hoyi) for 6 months. The δ(202)Hg and Δ(199)Hg of the lake trout equaled the isotopic composition of the bloater after 6 months, reflecting reequilibration of the Hg isotopic composition of the fish to new food sources and a lack of isotope fractionation during trophic transfer. We suggest that the stable Hg isotope ratios in fish can be used to trace environmental sources of Hg in aquatic ecosystems. PMID:22681311

  8. Absence of fractionation of mercury isotopes during trophic transfer of methylmercury to freshwater fish in captivity

    USGS Publications Warehouse

    Kwon, Sae Yun; Blum, Joel D.; Carvan, Michael J.; Basu, Niladri; Head, Jessica A.; Madenjian, Charles P.; David, Solomon R.

    2012-01-01

    We performed two controlled experiments to determine the amount of mass-dependent and mass-independent fractionation (MDF and MIF) of methylmercury (MeHg) during trophic transfer into fish. In experiment 1, juvenile yellow perch (Perca flavescens) were raised in captivity on commercial food pellets and then their diet was either maintained on unamended food pellets (0.1 μg/g MeHg) or was switched to food pellets with 1.0 μg/g or 4.0 μg/g of added MeHg, for a period of 2 months. The difference in δ202Hg (MDF) and Δ199Hg (MIF) between fish tissues and food pellets with added MeHg was within the analytical uncertainty (δ202Hg, 0.07 ‰; Δ199Hg, 0.06 ‰), indicating no isotope fractionation. In experiment 2, lake trout (Salvelinus namaycush) were raised in captivity on food pellets and then shifted to a diet of bloater (Coregonus hoyi) for 6 months. The δ202Hg and Δ199Hg of the lake trout equaled the isotopic composition of the bloater after 6 months, reflecting reequilibration of the Hg isotopic composition of the fish to new food sources and a lack of isotope fractionation during trophic transfer. We suggest that the stable Hg isotope ratios in fish can be used to trace environmental sources of Hg in aquatic ecosystems.

  9. Isotopic study of mercury sources and transfer between a freshwater lake and adjacent forest food web.

    PubMed

    Kwon, Sae Yun; Blum, Joel D; Nadelhoffer, Knute J; Timothy Dvonch, J; Tsui, Martin Tsz-Ki

    2015-11-01

    Studies of monomethylmercury (MMHg) sources and biogeochemical pathways have been extensive in aquatic ecosystems, but limited in forest ecosystems. Increasing evidence suggests that there is significant mercury (Hg) exchange between aquatic and forest ecosystems. We use Hg stable isotope ratios (δ(202)Hg and Δ(199)Hg) to investigate the relative importance of MMHg sources and assess Hg transfer pathways between Douglas Lake and adjacent forests located at the University of Michigan Biological Station, USA. We characterize Hg isotopic compositions of basal resources and use linear regression of % MMHg versus δ(202)Hg and Δ(199)Hg to estimate Hg isotope values for inorganic mercury (IHg) and MMHg in the aquatic and adjacent forest food webs. In the aquatic ecosystem, we found that lake sediment represents a mixture of IHg pools deposited via watershed runoff and precipitation. The δ(202)Hg and Δ(199)Hg values estimated for IHg are consistent with other studies that measured forest floor in temperate forests. The Δ(199)Hg value estimated for MMHg in the aquatic food web indicates that MMHg is subjected to ~20% photochemical degradation prior to bioaccumulation. In the forest ecosystem, we found a significant negative relationship between total Hg and δ(202)Hg and Δ(199)Hg of soil collected at multiple distances from the lakeshore and lake sediment. This suggests that IHg input from watershed runoff provides an important Hg transfer pathway between the forest and aquatic ecosystems. We measured Δ(199)Hg values for high trophic level insects and compared these insects at multiple distances perpendicular to the lake shoreline. The Δ(199)Hg values correspond to the % canopy cover suggesting that forest MMHg is subjected to varying extents of photochemical degradation and the extent may be controlled by sunlight. Our study demonstrates that the use of Hg isotopes adds important new insight into the relative importance of MMHg sources and complex Hg transfer

  10. 40 CFR 60.4112 - Changing Hg designated representative and alternate Hg designated representative; changes in...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 6 2010-07-01 2010-07-01 false Changing Hg designated representative and alternate Hg designated representative; changes in owners and operators. 60.4112 Section 60.4112... Generating Units Hg Designated Representative for Hg Budget Sources § 60.4112 Changing Hg...

  11. The abundances of Pt, Au, and Hg in the chemically peculiar HgMn-type stars kappa Cancri and chi Lupi

    NASA Technical Reports Server (NTRS)

    Wahlgren, Glenn M.; Leckrone, David S.; Johansson, Sveneric G.; Rosberg, Maria; Brage, Tomas

    1995-01-01

    Echelle mode spectra obtained with the Goddard High Resolution Spectrograph (GHRS) onboard the Hubble Space Telescope (HST) have been used to determine the abundances of the heavy elements Pt, Au, and Hg in the chemically peculiar HgMn-type stars kappa Cancri and chi Lupi. The abundances were determined by fitting observed line profiles with synthetically generated spectra and are found to be enhanced relative to solar system values by between three and five orders of magnitude in both stars. The Hg isotope mixture in kappa Cancri is found to resemble the terrestrial mixture while that of chi Lupi is dominated by the heaviest isotope. As determined from multiple ionization states, the abundances place constraints upon theories attempting to explain the large superficial abundances of heavy elements.

  12. Sources of mercury to San Francisco Bay surface sediment as revealed by mercury stable isotopes

    NASA Astrophysics Data System (ADS)

    Gehrke, Gretchen E.; Blum, Joel D.; Marvin-DiPasquale, Mark

    2011-02-01

    Mercury (Hg) concentrations and isotopic compositions were examined in shallow-water surface sediment (0-2 cm) from San Francisco (SF) Bay to determine the extent to which historic Hg mining contributes to current Hg contamination in SF Bay, and to assess the use of Hg isotopes to trace sources of contamination in estuaries. Inter-tidal and wetland sediment had total Hg (Hg T) concentrations ranging from 161 to 1529 ng/g with no simple gradients of spatial variation. In contrast, inter-tidal and wetland sediment displayed a geographic gradient of δ 202Hg values, ranging from -0.30‰ in the southern-most part of SF Bay (draining the New Almaden Hg District) to -0.99‰ in the northern-most part of SF Bay near the Sacramento-San Joaquin River Delta. Similar to SF Bay inter-tidal sediment, surface sediment from the Alviso Slough channel draining into South SF Bay had a δ 202Hg value of -0.29‰, while surface sediment from the Cosumnes River and Sacramento-San Joaquin River Delta draining into north SF Bay had lower average δ 202Hg values of -0.90‰ and -0.75‰, respectively. This isotopic trend suggests that Hg-contaminated sediment from the New Almaden Hg District mixes with Hg-contaminated sediment from a low δ 202Hg source north of SF Bay. Tailings and thermally decomposed ore (calcine) from the New Idria Hg mine in the California Coast Range had average δ 202Hg values of -0.37 and +0.03‰, respectively, showing that Hg calcination fractionates Hg isotopes resulting in Hg contamination from Hg(II) mine waste products with higher δ 202Hg values than metallic Hg(0) produced from Hg mines. Thus, there is evidence for at least two distinct isotopic signals for Hg contamination in SF Bay: Hg associated with calcine waste materials at Hg mines in the Coast Range, such as New Almaden and New Idria; and Hg(0) produced from these mines and used in placer gold mines and/or in other industrial processes in the Sierra Nevada region and SF Bay area.

  13. Impacts of Activated Carbon Amendment on Hg Methylation, Demethylation and Microbial Activity in Marsh Soils

    NASA Astrophysics Data System (ADS)

    Gilmour, C. C.; Ghosh, U.; Santillan, E. F. U.; Soren, A.; Bell, J. T.; Butera, D.; McBurney, A. W.; Brown, S.; Henry, E.; Vlassopoulos, D.

    2015-12-01

    In-situ sorbent amendments are a low-impact approach for remediation of contaminants in sediments, particular in habitats like wetlands that provide important ecosystem services. Laboratory microcosm trials (Gilmour et al. 2013) and early field trials show that activated carbon (AC) can effectively increase partitioning of both inorganic Hg and methylmercury to the solid phase. Sediment-water partitioning can serve as a proxy for Hg and MeHg bioavailability in soils. One consideration in using AC in remediation is its potential impact on organisms. For mercury, a critical consideration is the potential impact on net MeHg accumulation and bioavailability. In this study, we specifically evaluated the impact of AC on rates of methylmercury production and degradation, and on overall microbial activity, in 4 different Hg-contaminated salt marsh soils. The study was done over 28 days in anaerobic, sulfate-reducing slurries. A double label of enriched mercury isotopes (Me199Hg and inorganic 201Hg) was used to separately follow de novo Me201Hg production and Me199Hg degradation. AC amendments decreased both methylation and demethylation rate constants relative to un-amended controls, but the impact on demethylation was stronger. The addition of 5% (dry weight) regenerated AC to soil slurries drove demethylation rate constants to nearly zero; i.e. MeHg sorption to AC almost totally blocked its degradation. The net impact was increased solid phase MeHg concentrations in some of the soil slurries with the highest methylation rate constants. However, the net impact of AC amendments was to increase MeHg (and inorganic Hg) partitioning to the soil phase and decrease concentrations in the aqueous phase. AC significantly decreased aqueous phase inorganic Hg and MeHg concentrations after 28 days. Overall, the efficacy of AC in reducing aqueous MeHg was highest in the soils with the highest MeHg concentrations. The AC addition did not significantly impact microbial activity, as

  14. Small-scale studies of roasted ore waste reveal extreme ranges of stable mercury isotope signatures

    NASA Astrophysics Data System (ADS)

    Smith, Robin S.; Wiederhold, Jan G.; Jew, Adam D.; Brown, Gordon E.; Bourdon, Bernard; Kretzschmar, Ruben

    2014-07-01

    Active and closed Hg mines are significant sources of Hg contamination to the environment, mainly due to large volumes of mine waste material disposed of on-site. The application of Hg isotopes as source tracer from such contaminated sites requires knowledge of the Hg isotope signatures of different materials potentially released to the environment. Previous work has shown that calcine, the waste residue of the on-site ore roasting process, can exhibit distinct Hg isotope signatures compared with the primary ore. Here, we report results from a detailed small-scale study of Hg isotope variations in calcine collected from the closed New Idria Hg mine, San Benito County, CA, USA. The calcine samples exhibited different internal layering features which were investigated using optical microscopy, micro X-ray fluorescence, micro X-ray absorption spectroscopy (μ-XAS), and stable Hg isotope analysis. Significant Fe, S, and Hg concentration gradients were found across the different internal layers. Isotopic analyses revealed an extreme variation with pronounced isotopic gradients across the internal layered features. Overall, δ202Hg (±0.10‰, 2 SD) describing mass-dependent fractionation (MDF) ranged from -5.96 to 14.49‰, which is by far the largest range of δ202Hg values reported for any environmental sample. In addition, Δ199Hg (±0.06‰, 2 SD) describing mass-independent fractionation (MIF) ranged from -0.17 to 0.21‰. The μ-XAS analyses suggested that cinnabar and metacinnabar are the dominant Hg-bearing phases in the calcine. Our results demonstrate that the incomplete roasting of HgS ores in Hg mines can cause extreme mass-dependent Hg isotope fractionations at the scale of individual calcine pieces with enrichments in both light and heavy Hg isotopes relative to the primary ore signatures. This finding has important implications for the application of Hg isotopes as potential source tracers for Hg released to the environment from closed Hg mines and

  15. Mercury stable isotopic compositions in coals from major coal producing fields in China and their geochemical and environmental implications.

    PubMed

    Yin, Runsheng; Feng, Xinbin; Chen, Jiubin

    2014-05-20

    Total mercury (Hg) concentrations (THg) and stable mercury isotopic compositions were measured in coal samples (n = 61) from major coal producing fields in China. The THg concentrations in coals ranged from 0.05 to 0.78 μg g(-1), with a geometric mean of 0.22 μg g(-1). Hg isotopic compositions in coals showed large variations both in mass-dependent fractionation (MDF, δ(202)Hg: -2.36 to -0.14‰) and mass-independent fractionation (MIF, Δ(199)Hg: -0.44 to +0.38‰). The MIF signatures in coals may reveal important information on the coal-forming conditions (e.g., humic and sapropelic). The Δ(199)Hg/Δ(201)Hg of ∼1 determined in coals indicated that a portion of Hg has been subjected to photoreduction process prior to being incorporated to coals. On the basis of THg, Hg isotopic signatures, and other geological factors (e.g., total ash content and total sulfur content), the potential sources of Hg in coals from different coal producing regions were estimated. The main source of Hg in coals from southwestern China and eastern part of northern China is likely geogenic Hg, whereas the source of Hg in coals from other parts of northern China is mainly biogenic Hg. Finally, we estimated that Hg emission from coal combustion in China is characterized by diagnostic Hg isotopic signatures (δ(202)Hg: ∼-0.70‰ and Δ(199)Hg: ∼-0.05‰). The present study demonstrates that Hg isotopes can serve as a tool in understanding the sources and transformation of Hg in coals and may also be used as a tracer to quantify Hg emissions from coal combustion. PMID:24742360

  16. Assessment of mercury exposure among small-scale gold miners using mercury stable isotopes

    SciTech Connect

    Sherman, Laura S.; Blum, Joel D.; Basu, Niladri; Rajaee, Mozhgon; Evers, David C.; Buck, David G.; Petrlik, Jindrich; DiGangi, Joseph

    2015-02-15

    Total mercury (Hg) concentrations in hair and urine are often used as biomarkers of exposure to fish-derived methylmercury (MeHg) and gaseous elemental Hg, respectively. We used Hg stable isotopes to assess the validity of these biomarkers among small-scale gold mining populations in Ghana and Indonesia. Urine from Ghanaian miners displayed similar Δ{sup 199}Hg values to Hg derived from ore deposits (mean urine Δ{sup 199}Hg=0.01‰, n=6). This suggests that urine total Hg concentrations accurately reflect exposure to inorganic Hg among this population. Hair samples from Ghanaian miners displayed low positive Δ{sup 199}Hg values (0.23–0.55‰, n=6) and low percentages of total Hg as MeHg (7.6–29%, n=7). These data suggest that the majority of the Hg in these miners' hair samples is exogenously adsorbed inorganic Hg and not fish-derived MeHg. Hair samples from Indonesian gold miners who eat fish daily displayed a wider range of positive Δ{sup 199}Hg values (0.21–1.32‰, n=5) and percentages of total Hg as MeHg (32–72%, n=4). This suggests that total Hg in the hair samples from Indonesian gold miners is likely a mixture of ingested fish MeHg and exogenously adsorbed inorganic Hg. Based on data from both populations, we suggest that total Hg concentrations in hair samples from small-scale gold miners likely overestimate exposure to MeHg from fish consumption. - Highlights: • Mercury isotopes were measured in hair and urine from small-scale gold miners. • Mercury isotopes indicate that Hg in urine comes from mining activity. • Mercury isotopes suggest Hg in hair is a mixture of fish MeHg and inorganic Hg. • A large percentage of Hg in miner’s hair is released during amalgam burning and adsorbed.

  17. Dissolved Organic Matter Enhances Hg Bioavailability to a Hg-Methylating Bacterium Under Mildly Sulfidic Conditions

    NASA Astrophysics Data System (ADS)

    Graham, A. M.; Gilmour, C. C.

    2011-12-01

    Field studies have demonstrated a strong linkage between dissolved organic matter (DOM) quantity and quality and in-situ methylmercury (MeHg) production. The biogeochemical basis for these field observations is unknown however. Here, we investigate the roles of DOM and sulfide in controlling Hg bioavailability to the Hg-methylating bacterium Desulfovibrio desulfuricans ND132 in short-term washed cell assays. At environmentally relevant Hg/DOM ratios (2-4300 ng Hg/mg DOM), MeHg production increased linearly with increasing Suwannee River humic acid (SRHA) concentration, even in the presence of sulfide concentrations (5-10 μM) sufficient to outcompete SRHA for inorganic Hg. The DOM-dependent enhancement in Hg-methylation cannot be attributed to an enhancement of ND132 metabolic activity or alteration of Hg sorption to cells or bottle walls. Equilibrium speciation calculations indicated that cell suspensions were supersaturated with respect to metacinnabar (β-HgS(s)) and that Hg-DOM thiol complexes were relatively minor species. Notably, SRHA addition had no effect on Hg methylation in solutions where Hg-cysteine species predominated and β-HgS(s) precipitation was not predicted. We hypothesize that DOM enhances Hg-methylation by stabilizing HgS(s) colloids or nanoparticles against aggregation and/or by reducing the crystallinty of HgS(s) particles, and that such HgS(s) colloids are bioavailable to Hg-methylating bacteria. Ongoing work in the laboratory is evaluating the role of DOM character (size, aromaticity, reduced S content, etc.) in controlling the extent of the enhancement in MeHg production. These findings highlight the limits of equilibrium speciation approaches to predicting Hg bioavailability to methylating bacteria given the demonstrated significance of Hg-DOM-sulfide interactions in the anoxic environments where methylation occurs. Our laboratory experiments provide additional insight into the role that DOM plays in determining spatial and temporal

  18. Isotopic Composition of Gaseous Elemental Mercury in the Free Troposphere of the Pic du Midi Observatory, France.

    PubMed

    Fu, Xuewu; Marusczak, Nicolas; Wang, Xun; Gheusi, François; Sonke, Jeroen E

    2016-06-01

    Understanding the sources and transformations of mercury (Hg) in the free troposphere is a critical aspect of global Hg research. Here we present one year of observations of atmospheric Hg speciation and gaseous elemental Hg (GEM) isotopic composition at the high-altitude Pic du Midi Observatory (2860 m above sea level) in France. Biweekly integrated GEM from February 2012 to January 2013 revealed significant variations in δ(202)HgGEM (-0.04‰ to 0.52‰) but not in Δ(199)HgGEM (-0.17‰ to -0.27‰) or Δ(200)HgGEM (-0.10‰ to 0.05‰). δ(202)HgGEM was negatively correlated with CO and reflected air mass origins from Europe (high CO, low δ(202)HgGEM) and from the Atlantic Ocean (low CO, high δ(202)HgGEM). We suggest that the δ(202)HgGEM variations represent mixing of recent low δ(202)HgGEM European anthropogenic emissions with high δ(202)HgGEM northern hemispheric background GEM. In addition, Atlantic Ocean free troposphere air masses showed a positive correlation between δ(202)HgGEM and gaseous oxidized Hg (GOM) concentrations, indicative of mass-dependent Hg isotope fractionation during GEM oxidation. On the basis of atmospheric δ(202)HgGEM and speciated Hg observations, we suggest that the oceanic free troposphere is a reservoir within which GEM is readily oxidized to GOM. PMID:27214126

  19. Supersymmetry and {sup 198}Hg

    SciTech Connect

    Bernards, Christian; Heinze, Stefan; Jolie, Jan; Fransen, Christoph; Linnemann, Andreas; Radeck, Desiree

    2009-01-28

    The energy spectrum and electromagnetic transition properties of the supermultiplet members with two proton fermions can be constructed using the dynamical U{sub v}(6/12) x U{sub {pi}}(6/4) extended supersymmetry. In order to investigate predictions of the two proton fermion--four neutron boson supermultiplet member {sup 198}Hg, an experiment with the HORUS cube {gamma}-ray spectrometer at the Cologne TANDEM accelerator was performed using the {sup 196}Pt({alpha},2n){sup 198}Hg reaction. By analyzing {gamma}{gamma} coincidence spectra and {gamma}{gamma} angular correlations, the required experimental data--level and decay energies, level spins and multipole mixing ratios--could be obtained. For the low-energy states, the experimental data show good agreement with theory.

  20. Mercury Isotopic Composition of Young-of-Year Fish in San Francisco Bay

    NASA Astrophysics Data System (ADS)

    Gehrke, G. E.; Blum, J. D.; Slotton, D. G.; Greenfield, B. K.

    2009-12-01

    Variations in the stable isotopic composition of mercury (Hg) can provide information about sources and biogeochemical transformations of Hg in the environment. Mass-dependent fractionation of Hg isotopes, reported as δ202Hg relative to NIST 3133, has been observed during multiple processes including volatilization, diffusion, reduction and de-methylation. Large mass-independent fractionation of Hg (>0.2‰) reported as Δ199Hg, has been observed only during photochemical reduction of Hg and MeHg. In this study we analyzed the Hg isotopic composition of sediments and young (<4 months) fish from localized polyhaline habitats throughout San Francisco Bay to investigate sources of Hg to the aquatic food web and Hg cycling. Mississippi silverside have δ202Hg values ranging from -0.25 to +0.60‰, with regional variation among South and Lower South Bay (+0.10 to +0.60‰), San Pablo Bay (-0.25 to -0.03‰), and Suisun Bay (+0.13 to +0.42‰). Fish δ202Hg values roughly correlate with sediment δ202Hg values from the same sites. We suggest that each of the Guadalupe, Petaluma, and Sacaramento-San Joaquin river systems supply a distinct source of Hg to San Francisco Bay, likely associated with contaminated sediment. Mississippi silverside have Δ199Hg values ranging +0.46 to +1.55‰. Unlike the δ202Hg values, fish Δ199Hg values do not vary in a regular pattern throughout the Bay. Rather, fish from approximately one-third of sites analyzed exhibit relatively elevated Δ199Hg (> 0.8‰), possibly associated with high water clarity. In all fish analyzed, the ratio of Δ199Hg to Δ201Hg values have a narrow range of 1.19 to 1.40 (avg = 1.26 ± 0.06). These ratios in fish are consistent with laboratory studies of photochemical MeHg degradation, which yielded Δ199Hg: Δ201Hg ratios of ~1.3 (Bergquist and Blum, 2007). We suggest that Δ199Hg in fish varies with the extent of photochemical MeHg degradation prior to food web uptake. Bergquist, B. A. and Blum, J. D., 2007

  1. Fabrication and microstructure of Hg-1223 tape

    NASA Astrophysics Data System (ADS)

    Meng, R. L.; Wang, Y. Q.; Lewis, K.; Garcia, C.; Gao, L.; Xue, Y. Y.; Chu, C. W.

    1997-08-01

    A two-step spray/press process for the fabrication of Hg-1223 tape on a flexible Ni-substrate coated with Cr/(Ag,Pd) has been developed by using the mechanically aligned c-axis oriented Hg-1212 micrograins as the nucleation sites for the large c-axis oriented Hg-1223 grain growth. The self-field Jc of Hg-1223 tapes so reproducibly obtained is 7×104 A/cm2 at 77 K.

  2. New insight into biomarkers of human mercury exposure using naturally occurring mercury stable isotopes.

    PubMed

    Sherman, Laura S; Blum, Joel D; Franzblau, Alfred; Basu, Niladri

    2013-04-01

    Human exposure to methylmercury (MeHg) and elemental mercury vapor (Hg(0)(g)) are often estimated using total Hg concentrations in hair and urine, respectively. We investigated whether Hg stable isotopes could be used to better distinguish between exposure to Hg(0)(g) versus MeHg. We found that hair from North American dental professionals was characterized by high positive Δ(199)Hg values (mean = 1.86‰, 1 SD = 0.12‰, n = 11). This confirms that among people who regularly consume fish, total Hg concentrations in hair reflect exposure to MeHg. In contrast, we found that urine from the same individuals was characterized by a range of Δ(199)Hg values (0.29 to 1.77‰, 2 SD = 0.06‰, n = 12) that were significantly correlated to the number of dental amalgams in each individual's mouth. We hypothesize that fish-derived MeHg is demethylated within the body, causing mass-dependent fractionation and the excretion of inorganic Hg in urine. Mercury in urine therefore represents a mixture of demethylated fish-derived MeHg and amalgam-derived inorganic Hg. We estimate that the majority (>70%) of Hg in urine from individuals with <10 dental amalgams is derived from ingestion of MeHg in fish. These data suggest that within populations that consume fish, urine total Hg concentrations may overestimate Hg exposure from personal dental amalgams. PMID:23463943

  3. Evolution of Shell Structure in Neutron-Rich Calcium Isotopes

    SciTech Connect

    Hagen, G.; Hjorth-Jensen, M.; Machleidt, R; Papenbrock, T.

    2012-01-01

    We employ interactions from chiral effective field theory and compute the binding energies and low-lying excitations of calcium isotopes with the coupled-cluster method. Effects of three-nucleon forces are included phenomenologically as in-medium two-nucleon interactions, and the coupling to the particle continuum is taken into account using a Berggren basis. The computed ground-state energies and the low-lying J =2+ states for the isotopes 42,48,50,52Ca are in good agreement with data, and we predict the excitation energy of the first J =2+ state in 54Ca at 1.9 MeV, displaying only a weak subshell closure. In the odd-mass nuclei 53,55,61Ca we find that the positive parity states deviate strongly from the naive shell model.

  4. Exploiting Stable Mercury Isotopic Analysis to Differentiate between Mercury Sources: Gold Mining vs. Land-Use Change (Invited)

    NASA Astrophysics Data System (ADS)

    Bergquist, B. A.; Adler Miserendino, R. A.; Guimarães, J. R.; Veiga, M.; Velasquez-López, P.; Lees, P. S.; Thibodeau, A. M.; Fernandez, L. E.

    2013-12-01

    In parts of the developing world, mercury (Hg) is used to extract gold by amalgamation during artisanal and small-scale gold mining (ASGM) and this can lead to contamination of downstream aquatic ecosystems. Differentiation between Hg from ASGM and from other sources of Hg, such as increased erosion from land cover and land use change (LCLUC), is challenging and has lead to heated debates over the dominant sources of elevated Hg in some ecosystems. Here, stable Hg isotopic analysis was applied in two aquatic ecosystems in South America: (1) the Amazonian aquatic ecosystem of Amapá, Brazil downstream of artisanal gold mining (AGM) and (2) the Puyango-Tumbes River ecosystem downstream of Portovelo-Zaruma, Ecuador, a large mining area where both AGM and small-scale gold mining (SGM) are in operation. The Hg isotopic analyses from Amapá, Brazil, do not support AGM as the source of elevated Hg in the downstream aquatic ecosystem. Instead, Hg isotopes are most consistent with the elevated Hg being from preferential migration of Hg from soil erosion, which is likely associated with land use change. Although soils are regarded as Hg sinks in the global Hg cycle, this work suggests that LCLUC can disrupt Hg stores with significant ecological consequences. In contrast in the Southwestern Andean region of Ecuador and Peru, analysis of Hg isotopes and other toxic metals (i.e., Pb, Zn, Cu), which are associated with the larger scale mining and cyanide used during SGM, demonstrate Hg used during gold mining is the predominant source of Hg downstream and can be traced far from the dominant mining area. Although it has been speculated that Hg from SGM in Ecuador was not that mobile or that Hg far downstream of SGM processing plants was from erosion due to LCLUC or from AGM taking place downstream, the isotopically heavy signature of Hg used during gold mining and elevated other metal concentrations were observed ~120 km downstream of Portovelo-Zaruma. Mercury isotopes appear

  5. Packed bed reactor for photochemical .sup.196 Hg isotope separation

    DOEpatents

    Grossman, Mark W.; Speer, Richard

    1992-01-01

    Straight tubes and randomly oriented pieces of tubing having been employed in a photochemical mercury enrichment reactor and have been found to improve the enrichment factor (E) and utilization (U) compared to a non-packed reactor. One preferred embodiment of this system uses a moving bed (via gravity) for random packing.

  6. Engineering topological surface states: HgS, HgSe, and HgTe.

    PubMed

    Virot, François; Hayn, Roland; Richter, Manuel; van den Brink, Jeroen

    2013-10-01

    Using density functional electronic structure calculations, we establish the consequences of surface termination and modification on protected surface states of metacinnabar (β-HgS). Whereas we find that the Dirac cone is isotropic and well separated from the valence band for the (110) surface, it is highly anisotropic at the pure (001) surface. We demonstrate that the anisotropy is modified by surface passivation because the topological surface states include contributions from dangling bonds. Such dangling bonds exist on all pure surfaces within the whole class HgX with X=S, Se, or Te and directly affect the properties of the Dirac cone. Surface modifications also alter the spatial location (depth and decay length) of the topologically protected edge states, which renders them essential for the interpretation of photoemission data. PMID:24138263

  7. Specific Pathways of Dietary Methylmercury and Inorganic Mercury Determined by Mercury Speciation and Isotopic Composition in Zebrafish (Danio rerio).

    PubMed

    Feng, Caiyan; Pedrero, Zoyne; Gentès, Sophie; Barre, Julien; Renedo, Marina; Tessier, Emmanuel; Berail, Sylvain; Maury-Brachet, Régine; Mesmer-Dudons, Nathalie; Baudrimont, Magalie; Legeay, Alexia; Maurice, Laurence; Gonzalez, Patrice; Amouroux, David

    2015-11-01

    An original approach is proposed to investigate inorganic (iHg) and methylmercury (MeHg) trophic transfer and fate in a model fish, Danio rerio, by combining natural isotopic fractionation and speciation. Animals were exposed to three different dietary conditions: (1) 50 ng Hg g(-1), 80% as MeHg; (2) diet enriched in MeHg 10,000 ng Hg g(-1), 95% as MeHg, and (3) diet enriched in iHg 10,000 ng Hg g(-1), 99% as iHg. Harvesting was carried out after 0, 7, 25, and 62 days. Time-dependent Hg species distribution and isotopic fractionation in fish organs (muscle, brain, liver) and feces, exhibited different patterns, as a consequence of their dissimilar metabolization. The rapid isotopic re-equilibration to the new MeHg-food source reflects its high bioaccumulation rate. Relevant aspects related to Hg excretion are also described. This study confirms Hg isotopic fractionation as a powerful tool to investigate biological processes, although its deconvolution and fully understanding is still a challenge. PMID:26398726

  8. Total Hg and methyl Hg distribution in sediments of selected Louisiana water bodies.

    PubMed

    Delaune, Ronald D; Gambrell, Robert P; Devai, Istvan; Jugsujinda, Aroon; Kongchum, Manoch

    2009-05-01

    Sediment samples (543) collected from selected Louisiana streams and lakes were analyzed for total Hg and methyl Hg content. The average total Hg content among 543 samples was 92.3 +/- 95.1 microg kg(-1). The average methyl Hg content in the samples was 0.68 +/- 0.80 microg kg(-1). Methyl Hg accounted for an average of 0.73% of the total Hg in sediment. Linear regression analysis of total Hg versus methyl Hg content of the sediment showed methyl Hg content was significantly correlated to total Hg content of sediment (P > 0.01, n = 537) and sediment organic matter content. (P > 0.01, n = 536) Methyl Hg was also positively correlated to clay (P > 0.01, n = 537) and inversely correlated to sand content of sediment (P > 0.01, n = 537). Total Hg and methyl Hg content in these sediments was within the normal range reported elsewhere indicating no significant industrial or municipal Hg contamination. A comparison of selected water bodies with fishing advisories showed no relationship to total Hg and methyl Hg in sediment. PMID:19337918

  9. Carbon Stable Isotope Analysis of Methylmercury Toxin in Biological Materials by Gas Chromatography Isotope Ratio Mass Spectrometry.

    PubMed

    Masbou, Jeremy; Point, David; Guillou, Gaël; Sonke, Jeroen E; Lebreton, Benoit; Richard, Pierre

    2015-12-01

    A critical component of the biogeochemical cycle of mercury (Hg) is the transformation of inorganic Hg to neurotoxic monomethylmercury (CH3Hg). Humans are exposed to CH3Hg by consuming marine fish, yet the origin of CH3Hg in fish is a topic of debate. The carbon stable isotopic composition (δ(13)C) embedded in the methyl group of CH3Hg remains unexplored. This new isotopic information at the molecular level is thought to represent a new proxy to trace the carbon source at the origin of CH3Hg. Here, we present a compound-specific stable isotope analysis (CSIA) technique for the determination of the δ(13)C value of CH3Hg in biological samples by gas chromatography combustion isotope ratio mass spectrometry analysis (GC-C-IRMS). The method consists first of calibrating a CH3Hg standard solution for δ(13)C CSIA. This was achieved by comparing three independent approaches consisting of the derivatization and halogenation of the CH3Hg standard solution. The determination of δ(13)C(CH3Hg) values on natural biological samples was performed by combining a CH3Hg selective extraction, purification, and halogenation followed by GC-C-IRMS analysis. Reference δ(13)C values were established for a tuna fish certified material (ERM-CE464) originating from the Adriatic Sea (δ(13)C(CH3Hg) = -22.1 ± 1.5‰, ± 2 SD). This value is similar to the δ(13)C value of marine algal-derived particulate organic carbon (δ(13)CPOC = -21‰). PMID:26511394

  10. Mercury stable isotopes in seabird eggs reflect a gradient from terrestrial geogenic to oceanic mercury reservoirs.

    PubMed

    Day, Rusty D; Roseneau, David G; Berail, Sylvain; Hobson, Keith A; Donard, Olivier F X; Vander Pol, Stacy S; Pugh, Rebecca S; Moors, Amanda J; Long, Stephen E; Becker, Paul R

    2012-05-15

    Elevated mercury concentrations ([Hg]) were found in Alaskan murre (Uria spp.) eggs from the coastal embayment of Norton Sound relative to insular colonies in the northern Bering Sea-Bering Strait region. Stable isotopes of Hg, carbon, and nitrogen were measured in the eggs to investigate the source of this enrichment. Lower δ(13)C values in Norton Sound eggs (-23.3‰ to -20.0‰) relative to eggs from more oceanic colonies (-20.9‰ to -18.7‰) indicated that a significant terrestrial carbon source was associated with the elevated [Hg] in Norton Sound, implicating the Yukon River and smaller Seward Peninsula watersheds as the likely Hg source. The increasing [Hg] gradient extending inshore was accompanied by strong decreasing gradients of δ(202)Hg and Δ(199)Hg in eggs, indicating lower degrees of mass-dependent (MDF) and mass-independent Hg fractionation (MIF) (respectively) in the Norton Sound food web. Negative or zero MDF and MIF signatures are typical of geological Hg sources, which suggests murres in Norton Sound integrated Hg from a more recent geological origin that has experienced a relatively limited extent of aquatic fractionation relative to more oceanic colonies. The association of low δ(202)Hg and Δ(199)Hg with elevated [Hg] and terrestrial δ(13)C values suggested that Hg stable isotopes in murre eggs effectively differentiated terrestrial/geogenic Hg sources from oceanic reservoirs. PMID:22519440

  11. A (201)Hg+ Comagnetometer for (199)Hg+ Trapped Ion Space Atomic Clocks

    NASA Technical Reports Server (NTRS)

    Burt, Eric A.; Taghavi, Shervin; Tjoelker, Robert L.

    2011-01-01

    A method has been developed for unambiguously measuring the exact magnetic field experienced by trapped mercury ions contained within an atomic clock intended for space applications. In general, atomic clocks are insensitive to external perturbations that would change the frequency at which the clocks operate. On a space platform, these perturbative effects can be much larger than they would be on the ground, especially in dealing with the magnetic field environment. The solution is to use a different isotope of mercury held within the same trap as the clock isotope. The magnetic field can be very accurately measured with a magnetic-field-sensitive atomic transition in the added isotope. Further, this measurement can be made simultaneously with normal clock operation, thereby not degrading clock performance. Instead of using a conventional magnetometer to measure ambient fields, which would necessarily be placed some distance away from the clock atoms, first order field-sensitive atomic transition frequency changes in the atoms themselves determine the variations in the magnetic field. As a result, all ambiguity over the exact field value experienced by the atoms is removed. Atoms used in atomic clocks always have an atomic transition (often referred to as the clock transition) that is sensitive to magnetic fields only in second order, and usually have one or more transitions that are first-order field sensitive. For operating parameters used in the (199)Hg(+) clock, the latter can be five orders of magnitude or more sensitive to field fluctuations than the clock transition, thereby providing an unambiguous probe of the magnetic field strength.

  12. Combined in-beam electron and {gamma}-ray spectroscopy of {sup 184,186}Hg

    SciTech Connect

    Scheck, M.; Butler, P. A.; Gaffney, L. P.; Carrol, R. J.; Cox, D.; Joss, D. T.; Herzberg, R.-D.; Page, R. D.; Papadakis, P.; Watkins, H. V.; Bree, N.; Huyse, M.; Van Duppen, P.; Grahn, T.; Greenlees, P. T.; Herzan, A.; Jakobsson, U.; Jones, P.; Julin, R.; Juutinen, S.

    2011-03-15

    By exploiting the SAGE spectrometer a simultaneous measurement of conversion electrons and {gamma} rays emitted in the de-excitation of excited levels in the neutron-deficient nuclei {sup 184,186}Hg was performed. The light Hg isotopes under investigation were produced using the 4n channels of the fusion-evaporation reactions of {sup 40}Ar and {sup 148,150}Sm. The measured K- and L-conversion electron ratios confirmed the stretched E2 nature of several transitions of the yrast bands in {sup 184,186}Hg. Additional information on the E0 component of the 2{sub 2}{sup +}{yields}2{sub 1}{sup +} transition in {sup 186}Hg was obtained.

  13. Shape coexistence in {sup 180}Hg studied through the {beta} decay of {sup 180}Tl

    SciTech Connect

    Elseviers, J.; Bree, N.; Diriken, J.; Huyse, M.; Ivanov, O.; Van den Bergh, P.; Van Duppen, P.; Andreyev, A. N.; Antalic, S.; Barzakh, A.; Fedorov, D.; Cocolios, T. E.; Seliverstov, M.; Comas, V. F.; Heredia, J. A.; Fedosseyev, V. N.; Marsh, B. A.; Franchoo, S.; Page, R. D.

    2011-09-15

    The {beta}{sup +}/EC decay of {sup 180}Tl and excited states in the daughter nucleus {sup 180}Hg have been investigated at the CERN On-Line Isotope Mass Separator (ISOLDE) facility. Many new low-lying energy levels were observed in {sup 180}Hg, of which the most significant are the 0{sub 2}{sup +} at 419.6 keV and the 2{sub 2}{sup +} at 601.3 keV. The former is the bandhead of an excited band in {sup 180}Hg assumed originally to be of prolate nature. From the {beta} feeding to the different states in {sup 180}Hg, the ground-state spin of {sup 180}Tl was deduced to be (4{sup -},5{sup -}).

  14. Detection Feasibility of Magnetic Fields and HG Abundances in HgMn Stars

    NASA Astrophysics Data System (ADS)

    Takada-Hidai, M.; Sakaue, A.; Kotake, J.

    We analyzed two Fe II lines at 6147.7 AA and 6149.2 AA observed in 14 HgMn stars with the purpose to examine the feasibility of detecting magnetic fields in HgMn stars based on Mathys' empirical relation between the strengths of the Fe II lines and magnetic fields (Mathys 1990, A&A 232, 151). Takada-Hidai & Jugaku (1992, PASP 104, 106) found that the Fe II 6149 AA is strongly blended with the Hg II 6149.5 AA line in the typical HgMn star mu Lep. To investigate the blending effect of the Hg II line, we measured the strengths of Fe II lines in the sample stars with the Hg abundances of 4 < log Hg < 7 and obtained Hg abundaces from the blending Hg II lines. Most of the resulting Hg abundances were found to agree with the previously determined values within about 0.6 dex. We also found, from a comparison between the strengths of Fe II lines with Hg abundances, that the blending effect of the Hg II line seems to be negligible for the Hg abundances of about < 5 dex, and therefore magnetic fields may possibly be detected with Mathys' empirical relation in case of HgMn stars with such Hg abundances as < 5 dex.

  15. Assessment of mercury exposure among small-scale gold miners using mercury stable isotopes.

    PubMed

    Sherman, Laura S; Blum, Joel D; Basu, Niladri; Rajaee, Mozhgon; Evers, David C; Buck, David G; Petrlik, Jindrich; DiGangi, Joseph

    2015-02-01

    Total mercury (Hg) concentrations in hair and urine are often used as biomarkers of exposure to fish-derived methylmercury (MeHg) and gaseous elemental Hg, respectively. We used Hg stable isotopes to assess the validity of these biomarkers among small-scale gold mining populations in Ghana and Indonesia. Urine from Ghanaian miners displayed similar Δ(199)Hg values to Hg derived from ore deposits (mean urine Δ(199)Hg=0.01‰, n=6). This suggests that urine total Hg concentrations accurately reflect exposure to inorganic Hg among this population. Hair samples from Ghanaian miners displayed low positive Δ(199)Hg values (0.23-0.55‰, n=6) and low percentages of total Hg as MeHg (7.6-29%, n=7). These data suggest that the majority of the Hg in these miners' hair samples is exogenously adsorbed inorganic Hg and not fish-derived MeHg. Hair samples from Indonesian gold miners who eat fish daily displayed a wider range of positive Δ(199)Hg values (0.21-1.32‰, n=5) and percentages of total Hg as MeHg (32-72%, n=4). This suggests that total Hg in the hair samples from Indonesian gold miners is likely a mixture of ingested fish MeHg and exogenously adsorbed inorganic Hg. Based on data from both populations, we suggest that total Hg concentrations in hair samples from small-scale gold miners likely overestimate exposure to MeHg from fish consumption. PMID:25577187

  16. Pushing back the frontiers of mercury speciation using a combination of biomolecular and isotopic signatures: challenge and perspectives.

    PubMed

    Pedrero, Zoyne; Donard, Olivier F X; Amouroux, David

    2016-04-01

    Mercury (Hg) pollution is considered a major environmental problem due to the extreme toxicity of Hg. However, Hg metabolic pathways in biota remain elusive. An understanding of these pathways is crucial to elucidating the (eco)toxic effects of Hg and its biogeochemical cycle. The development of a new analytical methodology based on both speciation and natural isotopic fractionation represents a promising approach for metabolic studies of Hg and other metal(loid)s. Speciation provides valuable information about the reactivity and potential toxicity of metabolites, while the use of natural isotopic signature analysis adds a complementary dynamic dimension that allows the life history of the target element to be probed, the source of the target element (i.e., the source of pollution) to be identified, and reactions to be tracked. The resulting combined (bio)molecular and isotopic signature affords precious insight into the behavior of Hg in biota and Hg detoxification mechanisms. In the long term, this highly innovative methodology could be used in life and environmental science studies of metal(loid)s to push back the frontiers of our knowledge in this field. This paper summarizes the current status of the application of Hg speciation and the isotopic signature of Hg at the biomolecular level in living organisms, and discusses potential future uses of this combination of techniques. Graphical Abstract Application of Hg speciation and the isotopic signature of Hg to enhance our understanding of the roles of Hg in metabolic, toxicological, and environmental processes. PMID:26753975

  17. Reporting and measurement of mass-dependent and mass-independent fractionation of mercury isotopes

    NASA Astrophysics Data System (ADS)

    Bergquist, B. A.; Blum, J. D.

    2007-12-01

    Hg isotope analysis by MC-ICP-MS is an important new approach for fingerprinting Hg sources and monitoring Hg redox reactions and bioaccumulation, especially with the recent discovery of mass independent Hg isotope fractionation. Unfortunately research groups have adopted different standards, definitions of delta values, and methods of isotopic measurement. We suggest that a single standard, NIST SRM 3133, be adopted for reporting the isotopic variability of Hg isotopes. Isotope ratios should be determined by sample-standard bracketing (SSB) during analysis and reported as permil (‰) deviation from SRM 3133. For the highest precision and accuracy, a Tl internal standard along with SSB should be used to correct instrumental mass bias. Measurement routines should also include on-peak zero corrections and matching of concentration and matrix between the samples and bracketing standard. For samples that display mass-dependent fractionation (MDF), only one delta value needs to be reported (δ202/198Hg). Mass-independent fractionation (MIF) (Jackson et al., 2006; Bergquist et al., 2006; Bergquist and Blum, submitted) requires additional nomenclature, and we suggest reporting MIF as the deviation in isotope ratios from the theoretical mass dependent kinetic isotope fractionation (Δxxx/198Hg)¬. External reproducibility should be monitored by analysis of secondary standards. For studies of MDF, we use an in-house secondary standard solution made from metallic Hg mined from Almaden Spain and obtain a δ202Hg of -0.55 ±0.06‰ (2SD). For studies of MIF, we use NRCC CRM DORM-2 (dogfish muscle) and obtain a mean value of δ202Hg of +0.19 ±0.13‰ (2SD), Δ201Hg of +0.89 ±0.07‰ (2SD) , and Δ199Hg of +1.07 ±0.08‰ (2SD).

  18. The mercury isotope composition of Arctic coastal seawater

    NASA Astrophysics Data System (ADS)

    Štrok, Marko; Baya, Pascale Anabelle; Hintelmann, Holger

    2015-11-01

    For the first time, Hg isotope composition of seawater in the Canadian Arctic Archipelago is reported. Hg was pre-concentrated from large volumes of seawater sampling using anion exchange resins onboard the research vessel immediately after collection. Elution of Hg was performed in laboratory followed by isotope composition determination by multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS). For comparison, seawater from two stations was shipped to the laboratory and processed within it. Results showed negative mass-dependent fractionation in the range from -2.85 to -1.10‰ for δ202Hg, as well as slightly positive mass-independent fractionation of odd Hg isotopes. Positive mass-independent fractionation of 200Hg was also observed. Samples that were pre-concentrated in the laboratory showed different Hg isotope signatures and this is most probably due to the abiotic reduction of Hg in the dark by organic matter during storage and shipment after sampling. This emphasizes the need for immediate onboard pre-concentration.

  19. Mercury isotopic composition of hydrothermal systems in the Yellowstone Plateau volcanic field and Guaymas Basin sea-floor rift

    USGS Publications Warehouse

    Sherman, L.S.; Blum, J.D.; Nordstrom, D.K.; McCleskey, R.B.; Barkay, T.; Vetriani, C.

    2009-01-01

    To characterize mercury (Hg) isotopes and isotopic fractionation in hydrothermal systems we analyzed fluid and precipitate samples from hot springs in the Yellowstone Plateau volcanic field and vent chimney samples from the Guaymas Basin sea-floor rift. These samples provide an initial indication of the variability in Hg isotopic composition among marine and continental hydrothermal systems that are controlled predominantly by mantle-derived magmas. Fluid samples from Ojo Caliente hot spring in Yellowstone range in δ202Hg from - 1.02‰ to 0.58‰ (± 0.11‰, 2SD) and solid precipitate samples from Guaymas Basin range in δ202Hg from - 0.37‰ to - 0.01‰ (± 0.14‰, 2SD). Fluid samples from Ojo Caliente display mass-dependent fractionation (MDF) of Hg from the vent (δ202Hg = 0.10‰ ± 0.11‰, 2SD) to the end of the outflow channel (&delta202Hg = 0.58‰ ± 0.11‰, 2SD) in conjunction with a decrease in Hg concentration from 46.6pg/g to 20.0pg/g. Although a small amount of Hg is lost from the fluids due to co-precipitation with siliceous sinter, we infer that the majority of the observed MDF and Hg loss from waters in Ojo Caliente is due to volatilization of Hg0(aq) to Hg0(g) and the preferential loss of Hg with a lower δ202Hg value to the atmosphere. A small amount of mass-independent fractionation (MIF) was observed in all samples from Ojo Caliente (Δ199Hg = 0.13‰ ±1 0.06‰, 2SD) but no significant MIF was measured in the sea-floor rift samples from Guaymas Basin. This study demonstrates that several different hydrothermal processes fractionate Hg isotopes and that Hg isotopes may be used to better understand these processes.

  20. Mercury Isotopes as Proxies to Identify Sources and Environmental Impacts of Mercury in Sphalerites.

    PubMed

    Yin, Runsheng; Feng, Xinbin; Hurley, James P; Krabbenhoft, David P; Lepak, Ryan F; Hu, Ruizhong; Zhang, Qian; Li, Zhonggen; Bi, Xianwu

    2016-01-01

    During the past few years, evidence of mass independent fractionation (MIF) for mercury (Hg) isotopes have been reported in the Earth's surface reservoirs, mainly assumed to be formed during photochemical processes. However, the magnitude of Hg-MIF in interior pools of the crust is largely unknown. Here, we reported significant variation in Hg-MIF signature (Δ(199)Hg: -0.24 ~ + 0.18‰) in sphalerites collected from 102 zinc (Zn) deposits in China, indicating that Hg-MIF can be recorded into the Earth's crust during geological recycling of crustal material. Changing magnitudes of Hg-MIF signals were observed in Zn deposits with different formations, evidence that Hg isotopes (especially Hg-MIF) can be a useful tracer to identify sources (syngenetic and epigenetic) of Hg in mineral deposits. The average isotopic composition in studied sphalerites (δ(202)Hg average: -0.58‰; Δ(199)Hg average: +0.03‰) may be used to fingerprint Zn smelting activities, one of the largest global Hg emission sources. PMID:26728705

  1. Shedding light on the mercury mass discrepancy by weighing Hg 52+ ions in a Penning trap

    NASA Astrophysics Data System (ADS)

    Fritioff, T.; Bluhme, H.; Schuch, R.; Bergström, I.; Björkhage, M.

    2003-07-01

    In their nuclear tables Audi and Wapstra have pointed out a serious mass discrepancy between their extrapolated values for the mercury isotopes and those from a direct measurement by the Manitoba group. The values deviate by as much as 85 ppb from each other with claimed uncertainties of about 16 and 7 ppb, respectively. In order to decide which values are correct the masses of the 198Hg and 204Hg isotopes have been measured in the Stockholm Penning trap mass spectrometer SMILETRAP using 52+ ions. This charge state corresponds to a filled Ni electron configuration for which the electron binding energy can be accurately calculated. The mass values obtained are 197.966 768 44(43) u for 198Hg and 203.973 494 10(39) u for 204Hg. These values agree with those measured by the Manitoba group, with a 3 times lower uncertainty. This measurement was made possible through the implementation of a cooling technique of the highly charged mercury ions during charge breeding in the electron beam ion source used for producing the Hg 52+ ions.

  2. Hg196 and the ``magical quartet'' of the extended Uν(6/12)⊗Uπ(6/4) supersymmetry

    NASA Astrophysics Data System (ADS)

    Bernards, C.; Heinze, S.; Jolie, J.; Albers, M.; Fransen, C.; Radeck, D.

    2010-02-01

    We present the results of a γγ angular correlation experiment investigating the nucleus Hg196 and compare these with a theoretical description of Hg196 within the Uν(6/12)⊗Uπ(6/4) extended supersymmetry. To populate excited Hg196 states, we used the Cologne FN Tandem accelerator inducing the reaction Pt194(α,2n)Hg196 and analyzed the γ decays of levels up to an excitation energy of 2.4 MeV with the HORUS cube spectrometer. The new results on this mercury isotope allow a comparison between the experimental data and the supersymmetrical predictions and show good agreement. This way we can add Hg196 as a fifth supermultiplet member to the so-called magical quartet consisting of Pt194,195 and Au195,196.

  3. Historical Records of Mercury Stable Isotopes in Sediments of Tibetan Lakes

    PubMed Central

    Yin, Runsheng; Feng, Xinbin; Hurley, James P.; Krabbenhoft, David P.; Lepak, Ryan F.; Kang, Shichang; Yang, Handong; Li, Xiangdong

    2016-01-01

    The Tibetan Plateau (TP), known as the “Third Pole”, is a critical zone for atmospheric mercury (Hg) deposition. Increasing anthropogenic activities in the globe leads to environmental changes, which may affect the loading, transport and deposition of Hg in the environment. However, the deposition history and geochemical cycling of Hg in the TP is still uncertain. Our records of Hg and Hg isotopes in sediment profiles of the two largest lakes in the TP, Lake Qinghai and Nam Co, show increased Hg influx since last century, with the maximum Hg influx enrichment ratios of 5.4 and 3.5 in Lake Qinghai and Nam Co, respectively. Shifts in negative δ 202Hg in Lake Qinghai (−4.55 to −3.15‰) and Nam Co (−5.04 to −2.16‰) indicate increased atmospheric Hg deposition through rainfall, vegetation and runoff of soils. Mass independent fractionation of both even-Hg (∆ 200Hg: +0.05 to +0.10‰) and odd-Hg (∆ 199Hg: +0.12 to +0.31‰) isotopes were observed. Positive Δ 200Hg suggest high proportion of precipitation-derived Hg in the TP, whereas the positive Δ 199Hg results from Hg(II) photo-reduction. Both lakes show increasing Δ 199Hg since the 1900 s, and we conclude that with the decrease of ice duration, Hg(II) photo-reduction may have been accelerated in these TP lakes. PMID:26996936

  4. Historical Records of Mercury Stable Isotopes in Sediments of Tibetan Lakes

    NASA Astrophysics Data System (ADS)

    Yin, Runsheng; Feng, Xinbin; Hurley, James P.; Krabbenhoft, David P.; Lepak, Ryan F.; Kang, Shichang; Yang, Handong; Li, Xiangdong

    2016-03-01

    The Tibetan Plateau (TP), known as the “Third Pole”, is a critical zone for atmospheric mercury (Hg) deposition. Increasing anthropogenic activities in the globe leads to environmental changes, which may affect the loading, transport and deposition of Hg in the environment. However, the deposition history and geochemical cycling of Hg in the TP is still uncertain. Our records of Hg and Hg isotopes in sediment profiles of the two largest lakes in the TP, Lake Qinghai and Nam Co, show increased Hg influx since last century, with the maximum Hg influx enrichment ratios of 5.4 and 3.5 in Lake Qinghai and Nam Co, respectively. Shifts in negative δ 202Hg in Lake Qinghai (‑4.55 to ‑3.15‰) and Nam Co (‑5.04 to ‑2.16‰) indicate increased atmospheric Hg deposition through rainfall, vegetation and runoff of soils. Mass independent fractionation of both even-Hg (∆ 200Hg: +0.05 to +0.10‰) and odd-Hg (∆ 199Hg: +0.12 to +0.31‰) isotopes were observed. Positive Δ 200Hg suggest high proportion of precipitation-derived Hg in the TP, whereas the positive Δ 199Hg results from Hg(II) photo-reduction. Both lakes show increasing Δ 199Hg since the 1900 s, and we conclude that with the decrease of ice duration, Hg(II) photo-reduction may have been accelerated in these TP lakes.

  5. Assessing the potential for re-emission of mercury deposited in precipitation from arid soils using a stable isotope

    USGS Publications Warehouse

    Ericksen, J.A.; Gustin, M.S.; Lindberg, S.E.; Olund, S.D.; Krabbenhoft, D.P.

    2005-01-01

    A solution containing 198Hg in the form of HgCl2 was added to a 4 m2 area of desert soils in Nevada, and soil Hg fluxes were measured using three dynamic flux chambers. There was an immediate release of 198Hg after it was applied, and then emissions decreased exponentially. Within the first 6 h after the isotope was added to the soil, ???12 ng m-2 of 198Hg was emitted to the atmosphere, followed by a relatively steady flux of the isotope at 0.2 ?? 0.2 ng m-2 h-1 for the remainder of the experiment (62 days). Over this time, -200 ng m-2 or 2% of the 198Hg isotope was emitted from the soil, and we estimate that ???6% of the isotope would be re-emitted in a year's time. During the experiment, dry deposition of elemental Hg from the atmosphere was measured with an average deposition rate of 0.2 ?? 0.1 ng m-2 h-1. Emission of ambient Hg from the soil was observed after soil wetting with the isotope solution and after a storm event. However, the added moisture from the storm event did not affect 198Hg flux. Results suggest that in this desert environment, where there is limited precipitation, Hg deposited by wet processes is not readily re-emitted and that dry deposition of elemental Hg may be an important process. ?? 2005 American Chemical Society.

  6. Updated measurement of the permanent electric dipole moment (EDM) of 199Hg

    NASA Astrophysics Data System (ADS)

    Graner, Brent; Chen, Yi; Lindahl, Eric; Heckel, Blayne

    2016-03-01

    A permanent electric dipole moment (EDM) in an atom or particle would prove that time reversal symmetry is broken. In addition, an atomic EDM may provide evidence of new physics or CP symmetry violation in the strong sector. We have recently completed an improved measurement of the EDM of 199Hg utilizing a set of vapor cells containing isotopically-enriched 199Hg optically pumped and probed with UV laser light. I will discuss the most recent iteration of the experiment, and present unblinded results. This work was supported by NSF Grant 1306743 and DOE Award No. DE-FG02-97ER41020.

  7. Updated measurement of the permanent electric dipole moment (EDM) of 199 Hg

    NASA Astrophysics Data System (ADS)

    Graner, Brent; Chen, Yi; Lindahl, Eric; Heckel, Blayne

    2016-05-01

    A permanent electric dipole moment (EDM) in an atom or particle would prove that time reversal symmetry is broken. In addition, an atomic EDM may provide evidence of new physics or CP symmetry violation in the strong sector. We have recently completed an improved measurement of the EDM of 199 Hg utilizing a set of vapor cells containing isotopically-enriched 199 Hg optically pumped and probed with UV laser light. I will discuss the most recent iteration of the experiment, and present unblinded results. This work was supported by NSF Grant 1306743 and DOE Award No. DE-FG02-97ER41020.

  8. Mercury concentration correlates with the nitrogen stable isotope ratio in the animal food of Papuans.

    PubMed

    Yoshinaga, J; Suzuki, T; Hongo, T; Minagawa, M; Ohtsuka, R; Kawabe, T; Inaoka, T; Akimichi, T

    1992-08-01

    The relationships among element concentrations (Na, Mg, Al, P, K, Ca, Cr, Fe, Mn, Cu, Zn, Sr, total Hg, organic Hg, inorganic Hg, Pb) and stable carbon and nitrogen isotope ratios (13C/12C and 15N/14N) in animals consumed by the people called Gidra, who inhabit the lowland of Papua New Guinea, were examined. Animals analyzed included mammal, bird, fish, shellfish, reptile, crustacean, and insect. Highly significantly positive correlations were observed between total Hg concentrations and 15N/14N (r = 0.796), between organic Hg concentrations and 15N/14N (r = 0.781), and between inorganic Hg concentrations and 15N/14N (r = 0.739). This was interpreted to indicate that Hg was an element which accumulates in animals along the food chain. Based on the regression function of Hg on delta 15N, the bioconcentration factor for total, organic, and inorganic Hg was estimated to be 5. PMID:1385077

  9. The stable isotope compositions of mercury in atmospheric particles (PM10) from Paris (France) and vicinity

    NASA Astrophysics Data System (ADS)

    Widory, D.; Petelet-Giraud, E.; Johnson, T.; Quétel, C.; Snell, J.; van Bocxstaele, M.; Bullen, T. D.

    2010-12-01

    Solid mercury (Hg) in atmospheric particles in the environment can be derived from a variety of primary sources and cycled through numerous secondary processes, complicating identification of its origin. Using the PM10 fraction of aerosols from Paris and vicinity, we investigated the possibility that Hg stable isotope compositions could help identify the origins of atmospheric Hg and processes affecting the atmospheric Hg budget. Characterization of Hg isotope compositions of emissions from the different potential sources (e.g. waste incinerators, coal-fired power plants, metal refining plants, road traffic, heating sources and volcanic gases) shows that those containing Hg are clearly discriminated by specific Hg isotope signatures. PM10 were sampled in three different locations: A) downtown Paris, characterized by diffuse pollution, B) nearby suburb of the city, close to suspected Hg emitters, and C) in distant suburb of the city, having only a few industrial activities in the area. Results indicate that Hg in most of the PM10 samples is explained by binary mixings. The mixing end-members include at least two distinct sources at low Hg concentrations in the aerosols, compatible with industrial activity. At high Hg concentration in the aerosols, the isotopes may likewise indicate two distinct sources with δ202Hg compositions of -4.1 and -11.4 ‰. This range is significantly less than that measured on the potential sources of Hg pollution, and may indicate secondary processes, such as gas to solid phase transfers. The occurrence of post-emission processes is reinforced by the strong correlations existing between these low δ202Hg and MIF Δ201Hg values.

  10. Investigations of the g{sub K}-factors in the {sup 175,177,179}Hf Isotopes

    SciTech Connect

    Yakut, Hakan; Kuliev, Ali; Guliyev, Ekber

    2008-11-11

    In this paper the intrinsic g{sub K} and effective spin g{sub s} factors of the odd-mass {sup 175-179}Hf isotopes have been investigated within the Tamm-Dancoff approximation by using the realistic Saxon-Woods potential. The theoretically calculated g{sub K} and g{sub s}{sup eff} values are compared with experimental data. The comparison of the measured and calculated values of the effective g{sub s} factor shows that the spin polarization explains quite well the observed reduction of g{sub s} from its free-nucleon value.

  11. Element spots in HgMn stars

    NASA Astrophysics Data System (ADS)

    Korhonen, H.

    2014-11-01

    A fraction of late B-type stars, the so-called HgMn stars, exhibit enhanced absorption lines of certain chemical elements, notably Hg and Mn, combined with an underabundance of He. For about a decade it has been known that the elements with anomalously high abundances in HgMn stars are distributed inhomogeneously over the stellar surface. Observation of the temporal evolution of those spots has been reported in a few HgMn stars, first of a secular evolution of the mercury spots in α And, and more recently of a fast evolution of yttrium and strontium spots in HD 11753. The fast evolution of spots in HD 11753 is combined with a slower change in the overall abundance of the elements affected. In this paper I review what is known about these ``elemental spots'' in HgMn stars and their secular and fast temporal evolution.

  12. Atmospheric mercury inputs in montane soils increase with elevation: evidence from mercury isotope signatures

    PubMed Central

    Zhang, Hua; Yin, Run-sheng; Feng, Xin-bin; Sommar, Jonas; Anderson, Christopher W. N.; Sapkota, Atindra; Fu, Xue-wu; Larssen, Thorjørn

    2013-01-01

    The influence of topography on the biogeochemical cycle of mercury (Hg) has received relatively little attention. Here, we report the measurement of Hg species and their corresponding isotope composition in soil sampled along an elevational gradient transect on Mt. Leigong in subtropical southwestern China. The data are used to explain orography-related effects on the fate and behaviour of Hg species in montane environments. The total- and methyl-Hg concentrations in topsoil samples show a positive correlation with elevation. However, a negative elevation dependence was observed in the mass-dependent fractionation (MDF) and mass-independent fractionation (MIF) signatures of Hg isotopes. Both a MIF (Δ199Hg) binary mixing approach and the traditional inert element method indicate that the content of Hg derived from the atmosphere distinctly increases with altitude. PMID:24270081

  13. Laser induced fluorescence (LIF) of Hg2 and Hg3 via dissociation of HgBr2 at 157 nm

    NASA Astrophysics Data System (ADS)

    Skordoulis, C.; Sarantopoulou, E.; Spyrou, S. M.; Kosmidis, C.; Cefalas, A. C.

    1991-06-01

    Laser induced fluorescence of the mercury clusters Hg2 and Hg3 in the spectral range between 300 nm to 510 nm has been obtained from the dissociation of HgBr2 at 7.88 eV (157.5 nm) with an F2 molecular laser, together with fluorescence from mercury atomic transitions from highly excited states. The excitation process involves two photon absorption which dissociates the molecule at 15.76 eV total photon energy with the subsequent formation of the metallic clusters.

  14. 40 CFR 60.4160 - Submission of Hg allowance transfers.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 6 2010-07-01 2010-07-01 false Submission of Hg allowance transfers... Times for Coal-Fired Electric Steam Generating Units Hg Allowance Transfers § 60.4160 Submission of Hg allowance transfers. An Hg authorized account representative seeking recordation of a Hg allowance...

  15. Isotopic Biogeochemistry

    NASA Technical Reports Server (NTRS)

    Hayes, J. M.

    1985-01-01

    An overview is provided of the biogeochemical research. The funding, productivity, personnel and facilities are reviewed. Some of the technical areas covered are: carbon isotopic records; isotopic studies of banded iron formations; isotope effects in microbial systems; studies of organic compounds in ancient sediments; and development in isotopic geochemistry and analysis.

  16. Isotopic Variability of Mercury in Ore, Mine-Waste Calcine, and Leachates of Mine-Waste Calcine from Areas Mined for Mercury

    PubMed Central

    2009-01-01

    The isotopic composition of mercury (Hg) was determined in cinnabar ore, mine-waste calcine (retorted ore), and leachates obtained from water leaching experiments of calcine from two large Hg mining districts in the U.S. This study is the first to report significant mass-dependent Hg isotopic fractionation between cinnabar ore and resultant calcine. Data indicate that δ202Hg values relative to NIST 3133 of calcine (up to 1.52‰) in the Terlingua district, Texas, are as much as 3.24‰ heavier than cinnabar (−1.72‰) prior to retorting. In addition, δ202Hg values obtained from leachates of Terlingua district calcines are isotopically similar to, or as much as 1.17‰ heavier than associated calcines, most likely due to leaching of soluble, byproduct Hg compounds formed during ore retorting that are a minor component in the calcines. As a result of the large fractionation found between cinnabar and calcine, and because calcine is the dominant source of Hg contamination from the mines studied, δ202Hg values of calcine may be more environmentally important in these mined areas than the primary cinnabar ore. Measurement of the Hg isotopic composition of calcine is necessary when using Hg isotopes for tracing Hg sources from areas mined for Hg, especially mine water runoff. PMID:19848142

  17. Isotopic variability of mercury in ore, mine-waste calcine, and leachates of mine-waste calcine from areas mined for mercury

    USGS Publications Warehouse

    Stetson, S.J.; Gray, J.E.; Wanty, R.B.; Macalady, D.L.

    2009-01-01

    The isotopic composition of mercury (Hg) was determined in cinnabar ore, mine-waste calcine (retorted ore), and leachates obtained from water leaching experiments of calcine from two large Hg mining districts in the U.S. This study is the first to report significant mass-dependent Hg isotopic fractionation between cinnabar ore and resultant calcine. Data indicate that ??202Hg values relative to NIST 3133 of calcine (up to 1.52???) in the Terlingua district, Texas, are as much as 3.24??? heavier than cinnabar (-1.72???) prior to retorting. In addition, ??202Hg values obtained from leachates of Terlingua district calcines are isotopically similar to, or as much as 1.17??? heavier than associated calcines, most likely due to leaching of soluble, byproduct Hg compounds formed during ore retorting that are a minor component in the calcines. As a result of the large fractionation found between cinnabar and calcine, and because calcine is the dominant source of Hg contamination from the mines studied, ??202Hg values of calcine may be more environmentally important in these mined areas than the primary cinnabar ore. Measurement of the Hg isotopic composition of calcine is necessary when using Hg isotopes for tracing Hg sources from areas mined for Hg, especially mine water runoff. ?? 2009 American Chemical Society.

  18. Spatial-temporal dynamics and sources of total Hg in a hydroelectric reservoir in the Western Amazon, Brazil.

    PubMed

    Pestana, I A; Bastos, W R; Almeida, M G; de Carvalho, D P; Rezende, C E; Souza, C M M

    2016-05-01

    Damming rivers to construct hydroelectric reservoirs results in a series of impacts on the biogeochemical Hg cycle. For example, modifying the hydrodynamics of a natural watercourse can result in the suspension and transport of Hg deposits in the water column, which represents an exposure risk for biota. The objective of this study was to evaluate the influences of seasonality on the dispersion of total Hg in the Hydroelectric Power Plant (HPP)-Samuel Reservoir (Porto Velho/Brazil). Sampling campaigns were performed during the three following hydrological periods characteristic of the region: low (Oct/2011), ebbing (May/2012), and high (Feb/2013) water. Sediment profiles, suspended particulate matter (SPM), and aquatic macrophytes (Eicchornia crassipes and Oryza spp.) were collected, and their Hg concentrations and isotopic and elemental C and N signatures were determined. The drainage basin significantly influenced the SPM compositions during all the periods, with a small autochthonous influence from the reservoir during the low water. The highest SPM Hg concentrations inside the reservoir were observed during the high water period, suggesting that the hydrodynamics of this environment favor the suspension of fine SPM, which has a higher Hg adsorption capacity. The Hg concentrations in the sediment profiles were ten times lower than those in the SPM, indicating that large particles with low Hg concentrations were deposited to form the bottom sediment. Hg concentrations were higher in aquatic macrophyte roots than in their leaves and appeared to contribute to the formation of SPM during the low water period. In this environment, Hg transport mainly occurs in SPM from the Jamari River drainage basin, which is the primary source of Hg in this environment. PMID:26846239

  19. Mercury Stable Isotopes in Ornithogenic Deposits As Tracers of Historical Cycling of Mercury in Ross Sea, Antarctica.

    PubMed

    Zheng, Wang; Xie, Zhouqing; Bergquist, Bridget A

    2015-07-01

    Production of methylmercury (MeHg) in ocean waters and its bioaccumulation in marine organisms are critical processes controlling the fate and toxicity of mercury (Hg). However, these processes are not well understood in the Antarctic, where high levels of MeHg are observed in the subsurface ocean (100-1000 m). We explored the use of Hg stable isotope compositions in historical and modern biological deposits as a new approach for discerning Hg sources and tracing MeHg cycling in the ocean and bioaccumulation in marine biota. We found similar mass independent isotope fractionation (MIF) of Hg between a sediment profile containing historical penguin and seal feces deposits from coastal Antarctica and modern penguin and seal feces, suggesting that penguin and seal feces were the dominant sources of Hg to the sediments at different time periods. Furthermore, sediments dominated by seal feces displayed a significantly lower MIF slope (Δ(199)Hg/Δ(201)Hg) than those dominated by penguin feces despite similar extents of MIF. Since seals forage at greater depths (>400 m) than penguins (<100 m), the high MIF values and lower Δ(199)Hg/Δ(201)Hg in seal feces suggest that a significant fraction of MeHg accumulated by seals was produced in situ in the subsurface ocean from residual inorganic Hg(II) that sank from the euphotic zone after partial photoreduction. Our results suggest that in situ Hg methylation can be an important source of MeHg for marine biota, and Hg isotope compositions in biological archives can be valuable tracers of MeHg cycling. PMID:26020587

  20. Mass-dependent and mass-independent fractionation of mercury isotopes in precipitation from Guiyang, SW China

    NASA Astrophysics Data System (ADS)

    Wang, Zhuhong; Chen, Jiubin; Feng, Xinbin; Hintelmann, Holger; Yuan, Shengliu; Cai, Hongming; Huang, Qiang; Wang, Shuxiao; Wang, Fengyang

    2015-11-01

    The isotopic composition of mercury (Hg) is increasingly used to constrain the sources and pathways of this metal in the atmosphere. Though China has the highest Hg production, consumption and emission in the world, Hg isotope ratios are rarely reported for Chinese wet deposition. In this study, we examined, for the first time outside North America, both mass-dependent fractionation (MDF, expressed as δ202Hg) and mass-independent fractionation of odd (odd-MIF, Δ199Hg) and even (even-MIF, Δ200Hg) Hg isotopes in 15 precipitation samples collected from September 2012 to August 2013 in Guiyang (SW China). All samples displayed significant negative δ202Hg (-0.44 ∼ -4.27‰), positive Δ199Hg (+0.19 to +1.16‰) and slightly positive Δ200Hg (-0.01‰ to +0.20‰). Potential sources of Hg in precipitation were identified by coupling both MDF and MIF of Hg isotopes with a back-trajectory model. The results showed that local emission from coal-fired power plants and cement plants and western long-range transportation are two main contributing sources, while the contribution of Hg from south wind events would be very limited on an annual basis. The relatively lower Δ200Hg values in Guiyang precipitation may indicate a dilution effect by local sources and/or insignificant even-MIF in the tropopause contribution of this subtropical region. Our study demonstrates the usefulness of isotope fractionation, especially MIF for tracing sources and pathways of Hg in the atmosphere.

  1. Quasiparticle band structure of HgSe

    SciTech Connect

    Rohlfing, M.; Louie, S.G.

    1998-04-01

    Motivated by a recent discussion about the existence of a fundamental gap in HgSe [Phys. Rev. Lett. {bold 78}, 3165 (1997)], we calculate the quasiparticle band structure of HgSe within the GW approximation for the electron self-energy. The band-structure results show that HgSe is a semimetal, which is in agreement with most experimental data. We observe a strong wave-vector dependence of the self-energy of the lowest conduction band, leading to an increased dispersion and a small effective mass. This may help to interpret recent photoemission spectroscopy measurements. {copyright} {ital 1998} {ital The American Physical Society}

  2. Mercury Abundances and Isotopic Compositions in the Murchison (CM) and Allende (CV)Carbonaceous Chondrites

    NASA Technical Reports Server (NTRS)

    Lauretta, D. S.; Klaue, B.; Blum, J. D.; Buseck, P. R.

    2001-01-01

    The abundance and isotopic composition of Hg was determined in bulk samples of both the Murchison (CM) and Allende (CV) carbonaceous chondrites using single- and multi-collector inductively coupled plasma mass spectrometry (ICP-MS). The bulk abundances of Hg are 294 6 15 ng/g in Murchison and 30.0 6 1.5 ng/g in Allende. These values are within the range of previous measurements of bulk Hg abundances by neutron activation analysis (NAA). Prior studies suggested that both meteorites contain isotopically anomalous Hg, with d l 96/202Hg values for the anomalous, thermal-release components from bulk samples ranging from 2260 %o to 1440 9/00 in Murchison and from 2620 9/00 to 1540 9/00 in Allende (Jovanovic and Reed, 1976a; 1976b; Kumar and Goel, 1992). Our multi-collector ICP-MS measurements suggest that the relative abundances of all seven stable Hg isotopes in both meteorites are identical to terrestrial values within 0.2 to 0.5 9/00m. On-line thermal-release experiments were performed by coupling a programmable oven with the singlecollector ICP-MS. Powdered aliquots of each meteorite were linearly heated from room temperature to 900 C over twenty-five minutes under an Ar atmosphere to measure the isotopic composition of Hg released fiom the meteorites as a h c t i o n of temperature. In separate experiments, the release profiles of S and Se were determined simultaneously with Hg to constrain the Hg distribution within the meteorites and to evaluate the possibility of Se interferences in previous NAA studies. The Hg-release patterns differ between Allende and Murchison. The Hg-release profile for Allende contains two distinct peaks, at 225" and 343"C, whereas the profile for Murchison has only one peak, at 344 C. No isotopically anomalous Hg was detected in the thermal-release experiments at a precision level of 5 to 30 9/00, depending on the isotope ratio. In both meteorites the Hg peak at ;340"C correlates with a peak in the S-release profile. This correlation

  3. In Vivo Mass-independent Fractionation of Mercury Isotopes in Fish

    NASA Astrophysics Data System (ADS)

    Das, R.; Odom, L. A.

    2008-12-01

    Recent experimental work and analyses of natural samples have revealed both mass-dependent and mass- independent isotope fractionation effects in mercury. These findings portend new avenues toward understanding the global mercury cycle. It has been shown experimentally that photo reduction of Hg+2 and methylmercury in water with concomitant release of the reduced, gaseous species Hg° results in the residual methylmercury possessing a mass-independent isotope effect. This effect is a relative enrichment of isotopes 199Hg and 201Hg over the even mass number isotopes when compared to the mercury standard NIST SRM3133. Large mass independent fractionation (MIF) effects (Δ199Hg values of a few ‰) have been found in mercury in fish and interpreted as isotope effects inherited from the water. To evaluate the possibility that MIF might be produced within the fish, we have analyzed 38 samples that include zooplankton and twelve different species of fish from a single lake collected over a 2-month time period for mercury isotopic compositions. Trophic levels of the same fish specimens had previously been determined from stomach contents and nitrogen isotopes. Zooplankton in the lake contain mercury with Δ199Hg and Δ201Hg values of +0.43 (±0.07) and +0.44 (±0.07) respectively. Among the fish species there is a striking correspondence between trophic level and Δ199Hg and Δ201Hg values for primary, secondary, and tertiary consumers. The Δ199Hg values ranges over ~1‰ from ~+0.4 in zooplankton, juvenile bluegill and several other small fishes to Δ199Hg = + 1.36 for the Florida gar that is the top predator fish in the lake. These observations indicate that the MIF effect, rather than being an artifact of the water column is produced in vivo. Partial separation of 199Hg and 201Hg from isotopes of even neutron number can be achieved by the magnetic isotope effect in reactions involving sufficiently long-lived intermediate free radicals, where nuclear - electron

  4. Probing the Collective Degrees of Freedom at the Proton Drip Line in the Extremely Neutron Deficient {sup 172}Hg

    SciTech Connect

    Sandzelius, M.; Cederwall, B.; Hadinia, B.; Andgren, K.; Baeck, T.; Johnson, A.; Khaplanov, A.; Wyss, R.; Ganioglu, E.; Grahn, T.; Greenlees, P. T.; Jakobsson, U.; Jones, P. M.; Julin, R.; Juutinen, S.; Ketelhut, S.; Leino, M.; Nyman, M.; Peura, P.; Rahkila, P.; and others

    2011-11-30

    Excited states in the extremely neutron-deficient isotope {sup 172}Hg have been established for the first time. The {sup 96}Ru({sup 78}Kr,2n) reaction was employed to populate excited states in {sup 172}Hg with a cross section {sigma}{approx_equal} 15 nb. The highly selective Recoil-Decay Tagging (RDT) technique was used to obtain clean in-beam {gamma}-ray spectra for {sup 172}Hg. The yrast ground-state band has tentatively been established up to I = 6h-bar. The data have been interpreted within the framework of total Routhian surface and quasiparticle random phase approximation calculations. In addition to the well-known features of shape coexistence previously observed in light Hg isotopes, the systematic trends in the energy of the yrast 2{sup +} and 4{sup +} states in the chain of Hg isotopes indicate a pronounced vibrational collectivity which is reduced in strength, but at the same time shows a higher degree of harmonicity, as the neutron number decreases below the neutron midshell.

  5. Axi-symmetrical flow reactor for [sup 196]Hg photochemical enrichment

    DOEpatents

    Grossman, M.W.

    1991-04-30

    The present invention is directed to an improved photochemical reactor useful for the isotopic enrichment of a predetermined isotope of mercury, especially, [sup 196]Hg. Specifically, two axi-symmetrical flow reactors were constructed according to the teachings of the present invention. These reactors improve the mixing of the reactants during the photochemical enrichment process, affording higher yields of the desired [sup 196]Hg product. Measurements of the variation of yield (Y) and enrichment factor (E) along the flow axis of these reactors indicates very substantial improvement in process uniformity compared to previously used photochemical reactor systems. In one preferred embodiment of the present invention, the photoreactor system was built such that the reactor chamber was removable from the system without disturbing the location of either the photochemical lamp or the filter employed therewith. 10 figures.

  6. Identification of in-beam gamma rays in {sup 181}Hg

    SciTech Connect

    Davids, C.N.; Janssens, R.V.F.; Penttila, H.

    1995-08-01

    The interest in studying the neutron-deficient Hg isotopes stems from the fact that they are located in a region of the nuclear landscape where shape changes occur and where very large deformations were predicted. More specifically, the investigation of odd-A nuclei enables one to identify the orbitals located in the vicinity of the Fermi surface which play a crucial role in determining global properties such as nuclear shapes. Prior to this experiment, the {sup 183}Hg nucleus studied by this collaboration was the lightest odd-A Hg isotope known. From a recent experiment performed at the FMA in conjunction with 10 Compton-suppressed Ge detectors from the Argonne Notre Dame gamma-ray facility, it was possible to identify transitions in {sup 181}Hg following the {sup 144}Sm({sup 40}Ar,3n) reaction at a beam energy of 175 MeV. A level scheme was constructed and the transitions were regrouped into three rotational bands. One of these is proposed to be built on the [521]1/2{sup -} groundstate and the two others are interpreted as signature partner bands built on the [624]9/2{sup +} configuration. The statistics in this experiments were not sufficient to obtain multipolarity information and an additional measurement was proposed.

  7. The Hg region: Superdeformation and other shapes

    SciTech Connect

    Janssens, R.V.F.; Carpenter, M.P.; Fernandez, P.B.; Moore, E.F.; Ahmad, I.; Khoo, T.L.; Wolfs, F.L.H. ); Drigert, M.W. ); Ye, D.; Beard, K.B.; Reviol, W. ); Bearden, I.; Benet, P.; Daly, P.J.; Grabowski, Z.W. )

    1990-01-01

    We shall first summarize the present experimental situation concerning {sup 192}Hg, the nucleus regarded as the analog of {sup 152}Dy{sup 8} for this SD region in that shell gaps are calculated {sup 5} to occur at large deformation for Z=80 and N=112. Proton and neutron excitations out of te {sup 192}Hg core will then be reviewed with particular emphasis on {sup 191}Hg and {sup 193}Tl. The implications of the results for pairing at large deformations and the need to consider other degrees of freedom (such as octupole correlations) will be addressed. The presentation will conclude with a brief discussion on other shapes seen in this region, with a particular emphasis on {sup 191}Hg.

  8. Hg0 absorption in potassium persulfate solution*

    PubMed Central

    Ye, Qun-feng; Wang, Cheng-yun; Wang, Da-hui; Sun, Guan; Xu, Xin-hua

    2006-01-01

    The aqueous phase oxidation of gaseous elemental mercury (Hg0) by potassium persulfate (KPS) catalyzed by Ag+ was investigated using a glass bubble column reactor. Concentration of gaseous mercury and potassium persulfate were measured by cold vapor atom absorption (CVAA) and ion chromatograph (IC), respectively. The effects of pH value, concentration of potassium persulfate and silver nitrate (SN), temperature, Hg0 concentration in the reactor inlet and tertiary butanol (TBA), free radical scavenger, on the removal efficiency of Hg0 were studied. The results showed that the removal efficiency of Hg0 increased with increasing concentration of potassium persulfate and silver nitrate, while temperature and TBA were negatively effective. Furthermore, the removal efficiency of Hg0 was much better in neutral solution than in both acidic and alkaline solution. But the influence of pH was almost eliminated by adding AgNO3. High Hg0 concentration has positive effect. The possible reaction mechanism of gaseous mercury was also discussed. PMID:16615172

  9. Modeling atmospheric concentrations and deposition of Hg

    SciTech Connect

    Shannon, J.D.

    1994-06-01

    The deleterious effects on ecosystems of mercury pollution are well established and fish advisories are in effect for many lakes in North America. Because methylation and other transformation processes in ecosystems can alter the original speciation of deposited Hg, a decrease in atmospheric loading of Hg in all forms is highly desirable. The contribution to Hg deposition by emissions from current anthropogenic activities relative to the deposition contribution by emissions from natural processes must be estimated to establish what fraction of atmospheric loading to watersheds and ecosystems is at least potentially amenable to control actions. Additional modeling questions concern source-receptor relationships (SRR) for major point sources and for emissions aggregated over geopolitical regions or emission sectors, because of the usefulness of SRR in comparing effectiveness of alternate control strategies. Modeling of atmospheric Hg is less advanced than that of some other widespread air pollution problems such as acid deposition. Nonetheless, several promising studies have been made for northern Europe and North America. For this study of Hg deposition in eastern North America we extend modeling techniques used extensively and successfully during the last 15 years for concentrations and deposition of SO{sub x} and NO{sub x} over regional scales, with parameterization rates adjusted to suitable values for Hg transformation and removal.

  10. Hg(0) absorption in potassium persulfate solution.

    PubMed

    Ye, Qun-feng; Wang, Cheng-yun; Wang, Da-hui; Sun, Guan; Xu, Xin-hua

    2006-05-01

    The aqueous phase oxidation of gaseous elemental mercury (Hg(0)) by potassium persulfate (KPS) catalyzed by Ag(+) was investigated using a glass bubble column reactor. Concentration of gaseous mercury and potassium persulfate were measured by cold vapor atom absorption (CVAA) and ion chromatograph (IC), respectively. The effects of pH value, concentration of potassium persulfate and silver nitrate (SN), temperature, Hg(0) concentration in the reactor inlet and tertiary butanol (TBA), free radical scavenger, on the removal efficiency of Hg(0) were studied. The results showed that the removal efficiency of Hg(0) increased with increasing concentration of potassium persulfate and silver nitrate, while temperature and TBA were negatively effective. Furthermore, the removal efficiency of Hg(0) was much better in neutral solution than in both acidic and alkaline solution. But the influence of pH was almost eliminated by adding AgNO(3). High Hg(0) concentration has positive effect. The possible reaction mechanism of gaseous mercury was also discussed. PMID:16615172

  11. Hg(II) Coordination Studies in Penicillamine Enantiomers by 199mHg-TDPAC

    NASA Astrophysics Data System (ADS)

    Tröger, W.; ISOLDE Collaboration

    2001-11-01

    In order to study the binding of the toxic heavy metal ion Hg2+ to penicillamine, complexes with the D- and L-enantiomers of penicillamine were investigated by the nuclear quadrupole interaction of 199Hg monitored by time differential perturbed angular correlation spectroscopy. It was found that bound Hg(II) occurs in two-fold, three-fold and four-fold coordinations.

  12. Determination of Hg and Pb in fuels by inductively coupled plasma mass spectrometry using flow injection chemical vapor generation.

    PubMed

    Chen, Feng-yi; Jiang, Shiuh-Jen

    2009-12-01

    An isotope dilution inductively coupled plasma mass spectrometry (ICP-MS) method has been developed for the determination of Hg and Pb in fuels using flow injection vapor generation (VG) as the sample introduction system. A simple and inexpensive in-situ nebulizer/vapor generator was employed in this study. An emulsion containing 10% v/v fuel, 2% m/v Triton X-100 and 1.0% m/v tartaric acid was injected into VG-ICP-MS system for the determination of Hg and Pb. Sodium borohydride was used for vapor generation. Since the sensitivities of Hg and Pb in emulsion and those in aqueous solution are quite different, isotope dilution and standard addition methods were used for the determination of Hg and Pb in selected fuel samples. The influences of vapor generation conditions and emulsion preparation on the ion signals are reported. This method has been applied for the determination of Hg and Pb in various fuel samples such as diesel, gasoline and engine oil obtained locally. The analytical results obtained by isotope dilution and standard addition methods were in good agreement with each other and also with those of digested samples analyzed by pneumatic nebulization ICP-MS. Under the optimum operating conditions, the detection limits obtained were 0.02 and 0.03 ng mL(-1) for Hg and Pb, respectively, in prepared emulsified solutions, corresponding to 0.2 and 0.3 ng mL(-1) of Hg and Pb, respectively, in the original fuel samples. PMID:20009337

  13. Helium Pressure Shift of the Hyperfine Clock Transition in Hg-201(+)

    NASA Technical Reports Server (NTRS)

    Larigani, S. Taghavi; Burt, E. A.; Tjoelker, R. L.

    2010-01-01

    There are two stable odd isotopes of mercury with singly ionized hyperfine structure suitable for a microwave atomic clock: Hg-199(+) and Hg-201(+). We are investigating the viability of a trapped ion clock based on Hg-201(+) in a configuration that uses a buffer gas to increase ion loading efficiency and counter ion heating from rf trapping fields. Traditionally, either helium or neon is used as the buffer gas at approx. 10(exp -5) torr to confine mercury ions near room temperature. In addition to the buffer gas, other residual background gasses such as H2O, N2, O2, CO, CO2, and CH2 may be present in trace quantities. Collisions between trapped ions and buffer gas or background gas atoms/molecules produce a momentary shift of the ion clock transition frequency and constitute one of the largest systematic effects in this type of clock. Here we report an initial measurement of the He pressure shift in Hg-201(+) and compare this to Hg-199(+).

  14. Mercury Isotopes as Proxies to Identify Sources and Environmental Impacts of Mercury in Sphalerites

    PubMed Central

    Yin, Runsheng; Feng, Xinbin; Hurley, James P.; Krabbenhoft, David P.; Lepak, Ryan F.; Hu, Ruizhong; Zhang, Qian; Li, Zhonggen; Bi, Xianwu

    2016-01-01

    During the past few years, evidence of mass independent fractionation (MIF) for mercury (Hg) isotopes have been reported in the Earth’s surface reservoirs, mainly assumed to be formed during photochemical processes. However, the magnitude of Hg-MIF in interior pools of the crust is largely unknown. Here, we reported significant variation in Hg-MIF signature (Δ199Hg: −0.24 ~ + 0.18‰) in sphalerites collected from 102 zinc (Zn) deposits in China, indicating that Hg-MIF can be recorded into the Earth’s crust during geological recycling of crustal material. Changing magnitudes of Hg-MIF signals were observed in Zn deposits with different formations, evidence that Hg isotopes (especially Hg-MIF) can be a useful tracer to identify sources (syngenetic and epigenetic) of Hg in mineral deposits. The average isotopic composition in studied sphalerites (δ202Hgaverage: −0.58‰; Δ199Hgaverage: +0.03‰) may be used to fingerprint Zn smelting activities, one of the largest global Hg emission sources. PMID:26728705

  15. Mercury Isotopes as Proxies to Identify Sources and Environmental Impacts of Mercury in Sphalerites

    NASA Astrophysics Data System (ADS)

    Yin, Runsheng; Feng, Xinbin; Hurley, James P.; Krabbenhoft, David P.; Lepak, Ryan F.; Hu, Ruizhong; Zhang, Qian; Li, Zhonggen; Bi, Xianwu

    2016-01-01

    During the past few years, evidence of mass independent fractionation (MIF) for mercury (Hg) isotopes have been reported in the Earth’s surface reservoirs, mainly assumed to be formed during photochemical processes. However, the magnitude of Hg-MIF in interior pools of the crust is largely unknown. Here, we reported significant variation in Hg-MIF signature (Δ199Hg: -0.24 ~ + 0.18‰) in sphalerites collected from 102 zinc (Zn) deposits in China, indicating that Hg-MIF can be recorded into the Earth’s crust during geological recycling of crustal material. Changing magnitudes of Hg-MIF signals were observed in Zn deposits with different formations, evidence that Hg isotopes (especially Hg-MIF) can be a useful tracer to identify sources (syngenetic and epigenetic) of Hg in mineral deposits. The average isotopic composition in studied sphalerites (δ202Hgaverage: -0.58‰ Δ199Hgaverage: +0.03‰) may be used to fingerprint Zn smelting activities, one of the largest global Hg emission sources.

  16. A millennial-scale record of Pb and Hg contamination in peatlands of the Sacramento-San Joaquin Delta of California, USA

    USGS Publications Warehouse

    Drexler, Judith; Alpers, Charles N.; Neymark, Leonid; Paces, James B.; Taylor, Howard E.; Fuller, Christopher C.

    2016-01-01

    In this paper, we provide the first record of millennial patterns of Pb and Hg concentrations on the west coast of the United States. Peat cores were collected from two micro-tidal marshes in the Sacramento-San Joaquin Delta of California. Core samples were analyzed for Pb, Hg, and Ti concentrations and dated using radiocarbon, 210Pb, and 137Cs. Pre-anthropogenic concentrations of Pb and Hg in peat ranged from 0.60 to 13.0 µg g-1and from 6.9 to 71 ng g-1, respectively. For much of the past 6000+ years, the Delta was free from anthropogenic pollution, however, beginning in ~1425 CE, Hg and Pb concentrations, Pb/Ti ratios, Pb enrichment factors (EFs), and HgEFs all increased. Pb isotope compositions of the peat suggest that this uptick was likely caused by smelting activities originating in Asia. The next increases in Pb and Hg contamination occurred during the California Gold Rush (beginning ~1850 CE), when concentrations reached their highest levels (74 µg g-1 Pb, 990 ng g-1 Hg; PbEF = 12 and HgEF = 28). Lead concentrations increased again beginning in the ~1920s with the incorporation of Pb additives in gasoline. The phase-out of lead additives in the late 1980s was reflected in Pb isotope ratios and reductions in Pb concentrations in the surface layers of the peat. The rise and fall of Hg contamination was also tracked by the peat archive, with the highest Hg concentrations occurring just before 1963 CE and then decreasing during the post-1963 period. Overall, the results show that the Delta was a pristine region for most of its ~6700-year existence; however, since ~1425 CE, it has received Pb and Hg contamination from both global and regional sources.

  17. A millennial-scale record of Pb and Hg contamination in peatlands of the Sacramento-San Joaquin Delta of California, USA.

    PubMed

    Drexler, Judith Z; Alpers, Charles N; Neymark, Leonid A; Paces, James B; Taylor, Howard E; Fuller, Christopher C

    2016-05-01

    In this paper, we provide the first record of millennial patterns of Pb and Hg concentrations on the west coast of the United States. Peat cores were collected from two micro-tidal marshes in the Sacramento-San Joaquin Delta of California. Core samples were analyzed for Pb, Hg, and Ti concentrations and dated using radiocarbon and (210)Pb. Pre-anthropogenic concentrations of Pb and Hg in peat ranged from 0.60 to 13.0μgg(-1)and from 6.9 to 71ngg(-1), respectively. For much of the past 6000+ years, the Delta was free from anthropogenic pollution, however, beginning in ~1425CE, Hg and Pb concentrations, Pb/Ti ratios, Pb enrichment factors (EFs), and HgEFs all increased. Pb isotope compositions of the peat suggest that this uptick was likely caused by smelting activities originating in Asia. The next increases in Pb and Hg contamination occurred during the California Gold Rush (beginning ~1850CE), when concentrations reached their highest levels (74μgg(-1) Pb, 990ngg(-1) Hg; PbEF=12 and HgEF=28). Lead concentrations increased again beginning in the ~1920s with the incorporation of Pb additives in gasoline. The phase-out of lead additives in the late 1980s was reflected in changes in Pb isotope ratios and reductions in Pb concentrations in the surface layers of the peat. The rise and subsequent fall of Hg contamination was also tracked by the peat archive, with the highest Hg concentrations occurring just before 1963CE and then decreasing during the post-1963 period. Overall, the results show that the Delta was a pristine region for most of its ~6700-year existence; however, since ~1425CE, it has received Pb and Hg contamination from both global and regional sources. PMID:26918488

  18. Transport coefficients for electrons in Hg vapor

    NASA Astrophysics Data System (ADS)

    Dujko, Sasa; White, Ron; Petrovic, Zoran

    2012-06-01

    Transport coefficients and distribution functions are calculated for electrons in Hg vapor under swarm conditions using a multi term theory for solving the Boltzmann equation, over a range of E/N values and temperatures relevant to lamp discharges. It is shown that for higher E/N the electron distribution is non-thermal for all Hg vapor temperatures considered, and that the speed distribution function significantly deviates from a Maxwellian under these conditions. Our work has been motivated, in part, by recent suggestions that highly accurate data for transport coefficients required as input in fluid models of Hg vapor lamp discharges may significantly improve the existing models. Current models of such lamps require a knowledge of the plasma electrical conductivity, which can be calculated from the cross sections for electron scattering in Hg vapor and mobility coefficients presented in this work. The effect of metastable atoms on the swarm parameters is also discussed. The influence of a magnetic field on electron transport coefficients in Hg vapor is investigated over a range of B/N values and angles between the fields.

  19. HgCdTe barrier infrared detectors

    NASA Astrophysics Data System (ADS)

    Kopytko, M.; Rogalski, A.

    2016-05-01

    In the last decade, new strategies to achieve high-operating temperature (HOT) detectors have been proposed, including barrier structures such as nBn devices, unipolar barrier photodiodes, and multistage (cascade) infrared detectors. The ability to tune the positions of the conduction and valence band edges independently in a broken-gap type-II superlattices is especially helpful in the design of unipolar barriers. This idea has been also implemented in HgCdTe ternary material system. However, the implementation of this detector structure in HgCdTe material system is not straightforward due to the existence of a valence band discontinuity (barrier) at the absorber-barrier interface. In this paper we present status of HgCdTe barrier detectors with emphasis on technological progress in fabrication of MOCVD-grown HgCdTe barrier detectors achieved recently at the Institute of Applied Physics, Military University of Technology. Their performance is comparable with state-of-the-art of HgCdTe photodiodes. From the perspective of device fabrication their important technological advantage results from less stringent surface passivation requirements and tolerance to threading dislocations.

  20. 40 CFR 60.4153 - Recordation of Hg allowance allocations.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 6 2010-07-01 2010-07-01 false Recordation of Hg allowance allocations... Times for Coal-Fired Electric Steam Generating Units Hg Allowance Tracking System § 60.4153 Recordation of Hg allowance allocations. (a) By December 1, 2006, the Administrator will record in the Hg...

  1. 40 CFR 60.4114 - Objections concerning Hg designated representative.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 6 2010-07-01 2010-07-01 false Objections concerning Hg designated... Times for Coal-Fired Electric Steam Generating Units Hg Designated Representative for Hg Budget Sources § 60.4114 Objections concerning Hg designated representative. (a) Once a complete certificate...

  2. 40 CFR 60.4111 - Alternate Hg designated representative.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 6 2010-07-01 2010-07-01 false Alternate Hg designated representative... Times for Coal-Fired Electric Steam Generating Units Hg Designated Representative for Hg Budget Sources § 60.4111 Alternate Hg designated representative. (a) A certificate of representation under §...

  3. 40 CFR 60.45Da - Standard for mercury (Hg).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 6 2010-07-01 2010-07-01 false Standard for mercury (Hg). 60.45Da... for mercury (Hg). (a) For each coal-fired electric utility steam generating unit other than an IGCC... gases that contain mercury (Hg) emissions in excess of each Hg emissions limit in paragraphs...

  4. 46 CFR 53.12-1 - General (modifies HG-600 through HG-640).

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... reference; see 46 CFR 53.01-1) except as noted otherwise in this section. (b) For control systems for... HEATING BOILERS Instruments, Fittings, and Controls (Article 6) § 53.12-1 General (modifies HG-600 through HG-640). (a) The instruments, fittings and controls for heating boilers shall be as indicated in...

  5. 46 CFR 53.12-1 - General (modifies HG-600 through HG-640).

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... reference; see 46 CFR 53.01-1) except as noted otherwise in this section. (b) For control systems for... HEATING BOILERS Instruments, Fittings, and Controls (Article 6) § 53.12-1 General (modifies HG-600 through HG-640). (a) The instruments, fittings and controls for heating boilers shall be as indicated in...

  6. 46 CFR 53.12-1 - General (modifies HG-600 through HG-640).

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... reference; see 46 CFR 53.01-1) except as noted otherwise in this section. (b) For control systems for... HEATING BOILERS Instruments, Fittings, and Controls (Article 6) § 53.12-1 General (modifies HG-600 through HG-640). (a) The instruments, fittings and controls for heating boilers shall be as indicated in...

  7. 46 CFR 53.12-1 - General (modifies HG-600 through HG-640).

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... reference; see 46 CFR 53.01-1) except as noted otherwise in this section. (b) For control systems for... HEATING BOILERS Instruments, Fittings, and Controls (Article 6) § 53.12-1 General (modifies HG-600 through HG-640). (a) The instruments, fittings and controls for heating boilers shall be as indicated in...

  8. 46 CFR 53.12-1 - General (modifies HG-600 through HG-640).

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... reference; see 46 CFR 53.01-1) except as noted otherwise in this section. (b) For control systems for... HEATING BOILERS Instruments, Fittings, and Controls (Article 6) § 53.12-1 General (modifies HG-600 through HG-640). (a) The instruments, fittings and controls for heating boilers shall be as indicated in...

  9. Isotopic Fractionation of Mercury in Great Lakes Precipitation

    NASA Astrophysics Data System (ADS)

    Gratz, L. E.; Keeler, G. J.; Blum, J. D.; Sherman, L. S.

    2009-12-01

    Mercury (Hg) is a hazardous bioaccumulative neurotoxin, and atmospheric deposition is a primary way in which mercury enters terrestrial and aquatic ecosystems. However, the chemical processes and transport regimes that mercury undergoes from emission to deposition are not well understood. Thus the use of mercury isotopes to characterize the biogeochemical cycling of mercury is a rapidly growing area of study. Precipitation samples were collected in Chicago, IL, Holland, MI, and Dexter, MI from April 2007 - October 2007 to begin examining the isotopic fractionation of atmospheric mercury in the Great Lakes region. Results show that mass-dependent fractionation relative to NIST-3133 (MDF - δ202Hg) ranged from -0.8‰ to 0.2‰ (±0.2‰) in precipitation samples, while mass-independent fractionation (MIF - Δ199Hg) varied from 0.1‰ to 0.6‰ (±0.1‰). Although clear urban-rural differences were not observed, this may be due to the weekly collection of precipitation samples rather than collection of individual events, making it difficult to truly characterize the meteorology and source influences associated with each sample and suggesting that event-based collection is necessary during future sampling campaigns. Additionally, total vapor phase mercury samples were collected in Dexter, MI in 2009 to examine isotopic fractionation of mercury in ambient air. In ambient samples δ202Hg ranged from 0.3‰ to 0.5‰ (±0.1‰), however Δ199Hg was not significant. Because mercury in precipitation is predominantly Hg2+, while ambient vapor phase mercury is primarily Hg0, these results may suggest the occurrence of MIF during the oxidation of Hg0 to Hg2+ prior to deposition. Furthermore, although it has not been previously reported or predicted, MIF of 200Hg was also detected. Δ200Hg ranged from 0.0‰ to 0.2‰ in precipitation and from -0.1‰ to 0.0‰ in ambient samples. This work resulted in methodological developments in the collection and processing of

  10. Mass-Dependent and -Independent Fractionation of Mercury Isotopes in Aquatic Systems

    NASA Astrophysics Data System (ADS)

    Bergquist, B. A.; Joel, B. D.; Jude, D. J.

    2008-12-01

    Mercury is a globally distributed and highly toxic pollutant. Although Hg is a proven health risk, much of the natural cycle of Hg is not well understood and new approaches are needed to track Hg and the chemical transformations it undergoes in the environment. Recently, we demonstrated that Hg isotopes exhibit two types of isotope fractionation: (1) mass dependent fractionation (MDF) and (2) mass independent fractionation (MIF) of only the odd isotopes (Bergquist and Blum, 2007). The observation of large MIF of Hg isotopes (up to 5 permil) is exciting because only a few other isotopic systems have been documented to display large MIF, the most notable of which are oxygen and sulfur. In both cases, the application of MIF has proven very useful in a variety of fields including cosmochemistry, paleoclimatology, physical chemistry, atmospheric chemistry, and biogeochemistry. Both MDF and MIF isotopic signatures are observed in natural samples, and together they open the door to a new method for tracing Hg pollution and for investigating Hg behavior in the environment. For example, fish record MDF that appears to be related to size and age. Additionally, fish display MIF signatures that are consistent with the photo-reduction of methylmercury (Bergquist and Blum, 2007). If the MDF and MIF in ecosystems can be understood, the signatures in fish could inform us about the sources and processes transforming Hg and why there are differences in the bioaccumulation of Hg in differing ecosystems and populations of fish. This requires sampling of a variety of ecosystems, the sampling of many components of the ecosystems, and the use of other tracers such as carbon and nitrogen isotopes. We have expanded our studies of aquatic ecosystems to include several lakes in North America. Similar to other isotopic systems used to study food web dynamics and structure (i.e., C and N), the MDF of Hg in fish appears to be related to size and age. The MDF recorded in fish likely reflects

  11. Thermodynamics limits the reactivity of BrHg

    NASA Astrophysics Data System (ADS)

    Dibble, Theodore S.; Schwid, Abraham C.

    2016-08-01

    Mercury emissions to the atmosphere primarily consist of Hg(0), which tends not to enter ecosystems until it is oxidized. Atomic bromine initiates oxidation of Hg(0) via the BrHg intermediate, but the further reactions of BrHg are just beginning to be explored. Here we use quantum chemistry to determine that hydrogen abstraction from hydrocarbons by BrHg is so endothermic as to be irrelevant. Bonds between BrHg and carbon atoms are so weak that BrHg addition to carbon-carbon double bonds atoms will be somewhat ineffective in leading to further reactions.

  12. {alpha} decay studies of very neutron-deficient francium and radium isotopes

    SciTech Connect

    Uusitalo, J.; Leino, M.; Enqvist, T.; Grahn, T.; Greenlees, P.T.; Jones, P.; Julin, R.; Juutinen, S.; Keenan, A.; Kettunen, H.; Koivisto, H.; Kuusiniemi, P.; Leppaenen, A.-P.; Nieminen, P.; Pakarinen, J.; Rahkila, P.; Scholey, C.; Eskola, K.

    2005-02-01

    Very neutron-deficient francium and radium isotopes have been produced in fusion evaporation reactions using {sup 63}Cu and {sup 65}Cu ions on {sup 141}Pr targets and {sup 36}Ar ions on {sup 170}Yb targets. The gas-filled recoil separator RITU was employed to collect the fusion products and to separate them from the scattered beam. The activities were implanted into a position-sensitive silicon detector after passing through a gas-counter system. The isotopes were identified using spatial and time correlations between the implants and decays. Two new {alpha} decaying radium isotopes, {sup 201}Ra and {sup 202}Ra, were identified. The {alpha} decay energy and half-life of {sup 203}Ra were measured with improved precision. The {alpha} decay properties measured for the francium isotopes {sup 201}Fr,{sup 202}Fr,{sup 203}Fr, and {sup 204}Fr were confirmed, in many cases with improved precision. For the first time, a ({pi}s{sub 1/2}{sup -1})1/2{sup +} proton intruder state was identified in francium isotopes, namely in {sup 201}Fr and tentatively in {sup 203}Fr. The measured decay properties for the neutron-deficient odd-mass Fr isotopes suggest an onset of substantial deformation at N=112.

  13. Quasiparticle excitations in superdeformed {sup 192}Hg

    SciTech Connect

    Lauritsen, T.; Carpenter, M.P.; Janssens, R.V.F.

    1995-08-01

    The nucleus {sup 192}Hg plays a pivotal role for superdeformation in the mass 190 region, since calculations of single-particle levels show large shell-gaps for the superdeformed (SD) shape at N = 112 and Z = 80. As a result, {sup 192}Hg is referred to as the doubly magic SD nucleus for the A = 190 region. In previous studies, only one superdeformed band was observed in this nucleus, and this fact was cited as indirect evidence that large shell gaps do indeed exist at the proposed particle numbers.

  14. Adsorption of Hg on lunar samples

    SciTech Connect

    Reed, G.W. Jr.; Jovanovic, S.

    1985-01-01

    Understanding the presence, migration mechanisms and trapping of indigneous gases and volatiles on the moon is the objective of this study. The rare gases Ar and Xe and highly volatile Hg/sup 0/ and Br/sup 0/ (and/or their compounds) have been determined to be present in the lunar regolith. Evidence for these elements in the moon was recently reviewed. Studies of the sorption behavior of Xe on lunar material have been carried out. We report here preliminary results of a study designed to rationalize the behavior of Hg in lunar material.

  15. Hg-201 (+) CO-Magnetometer for HG-199(+) Trapped Ion Space Atomic Clocks

    NASA Technical Reports Server (NTRS)

    Burt, Eric A. (Inventor); Taghavi, Shervin (Inventor); Tjoelker, Robert L. (Inventor)

    2011-01-01

    Local magnetic field strength in a trapped ion atomic clock is measured in real time, with high accuracy and without degrading clock performance, and the measurement is used to compensate for ambient magnetic field perturbations. First and second isotopes of an element are co-located within the linear ion trap. The first isotope has a resonant microwave transition between two hyperfine energy states, and the second isotope has a resonant Zeeman transition. Optical sources emit ultraviolet light that optically pump both isotopes. A microwave radiation source simultaneously emits microwave fields resonant with the first isotope's clock transition and the second isotope's Zeeman transition, and an optical detector measures the fluorescence from optically pumping both isotopes. The second isotope's Zeeman transition provides the measure of magnetic field strength, and the measurement is used to compensate the first isotope's clock transition or to adjust the applied C-field to reduce the effects of ambient magnetic field perturbations.

  16. {sup 196}Hg and the 'magical quartet' of the extended U{sub {nu}}(6/12) x U{sub {pi}}(6/4) supersymmetry

    SciTech Connect

    Bernards, C.; Heinze, S.; Jolie, J.; Albers, M.; Fransen, C.; Radeck, D.

    2010-02-15

    We present the results of a {gamma}{gamma} angular correlation experiment investigating the nucleus {sup 196}Hg and compare these with a theoretical description of {sup 196}Hg within the U{sub {nu}}(6/12) x U{sub {pi}}(6/4) extended supersymmetry. To populate excited {sup 196}Hg states, we used the Cologne FN Tandem accelerator inducing the reaction {sup 194}Pt({alpha},2n){sup 196}Hg and analyzed the {gamma} decays of levels up to an excitation energy of 2.4 MeV with the HORUS cube spectrometer. The new results on this mercury isotope allow a comparison between the experimental data and the supersymmetrical predictions and show good agreement. This way we can add {sup 196}Hg as a fifth supermultiplet member to the so-called magical quartet consisting of {sup 194,195}Pt and {sup 195,196}Au.

  17. Modeling nuclear volume isotope effects in crystals

    PubMed Central

    Schauble, Edwin A.

    2013-01-01

    Mass-independent isotope fractionations driven by differences in volumes and shapes of nuclei (the field shift effect) are known in several elements and are likely to be found in more. All-electron relativistic electronic structure calculations can predict this effect but at present are computationally intensive and limited to modeling small gas phase molecules and clusters. Density functional theory, using the projector augmented wave method (DFT-PAW), has advantages in greater speed and compatibility with a three-dimensional periodic boundary condition while preserving information about the effects of chemistry on electron densities within nuclei. These electron density variations determine the volume component of the field shift effect. In this study, DFT-PAW calculations are calibrated against all-electron, relativistic Dirac–Hartree–Fock, and coupled-cluster with single, double (triple) excitation methods for estimating nuclear volume isotope effects. DFT-PAW calculations accurately reproduce changes in electron densities within nuclei in typical molecules, when PAW datasets constructed with finite nuclei are used. Nuclear volume contributions to vapor–crystal isotope fractionation are calculated for elemental cadmium and mercury, showing good agreement with experiments. The nuclear-volume component of mercury and cadmium isotope fractionations between atomic vapor and montroydite (HgO), cinnabar (HgS), calomel (Hg2Cl2), monteponite (CdO), and the CdS polymorphs hawleyite and greenockite are calculated, indicating preferential incorporation of neutron-rich isotopes in more oxidized, ionically bonded phases. Finally, field shift energies are related to Mössbauer isomer shifts, and equilibrium mass-independent fractionations for several tin-bearing crystals are calculated from 119Sn spectra. Isomer shift data should simplify calculations of mass-independent isotope fractionations in other elements with Mössbauer isotopes, such as platinum and uranium

  18. Modeling nuclear volume isotope effects in crystals.

    PubMed

    Schauble, Edwin A

    2013-10-29

    Mass-independent isotope fractionations driven by differences in volumes and shapes of nuclei (the field shift effect) are known in several elements and are likely to be found in more. All-electron relativistic electronic structure calculations can predict this effect but at present are computationally intensive and limited to modeling small gas phase molecules and clusters. Density functional theory, using the projector augmented wave method (DFT-PAW), has advantages in greater speed and compatibility with a three-dimensional periodic boundary condition while preserving information about the effects of chemistry on electron densities within nuclei. These electron density variations determine the volume component of the field shift effect. In this study, DFT-PAW calculations are calibrated against all-electron, relativistic Dirac-Hartree-Fock, and coupled-cluster with single, double (triple) excitation methods for estimating nuclear volume isotope effects. DFT-PAW calculations accurately reproduce changes in electron densities within nuclei in typical molecules, when PAW datasets constructed with finite nuclei are used. Nuclear volume contributions to vapor-crystal isotope fractionation are calculated for elemental cadmium and mercury, showing good agreement with experiments. The nuclear-volume component of mercury and cadmium isotope fractionations between atomic vapor and montroydite (HgO), cinnabar (HgS), calomel (Hg2Cl2), monteponite (CdO), and the CdS polymorphs hawleyite and greenockite are calculated, indicating preferential incorporation of neutron-rich isotopes in more oxidized, ionically bonded phases. Finally, field shift energies are related to Mössbauer isomer shifts, and equilibrium mass-independent fractionations for several tin-bearing crystals are calculated from (119)Sn spectra. Isomer shift data should simplify calculations of mass-independent isotope fractionations in other elements with Mössbauer isotopes, such as platinum and uranium. PMID

  19. Modeling nuclear volume isotope effects in crystals

    NASA Astrophysics Data System (ADS)

    Schauble, Edwin A.

    2013-10-01

    Mass-independent isotope fractionations driven by differences in volumes and shapes of nuclei (the field shift effect) are known in several elements and are likely to be found in more. All-electron relativistic electronic structure calculations can predict this effect but at present are computationally intensive and limited to modeling small gas phase molecules and clusters. Density functional theory, using the projector augmented wave method (DFT-PAW), has advantages in greater speed and compatibility with a three-dimensional periodic boundary condition while preserving information about the effects of chemistry on electron densities within nuclei. These electron density variations determine the volume component of the field shift effect. In this study, DFT-PAW calculations are calibrated against all-electron, relativistic Dirac-Hartree-Fock, and coupled-cluster with single, double (triple) excitation methods for estimating nuclear volume isotope effects. DFT-PAW calculations accurately reproduce changes in electron densities within nuclei in typical molecules, when PAW datasets constructed with finite nuclei are used. Nuclear volume contributions to vapor-crystal isotope fractionation are calculated for elemental cadmium and mercury, showing good agreement with experiments. The nuclear-volume component of mercury and cadmium isotope fractionations between atomic vapor and montroydite (HgO), cinnabar (HgS), calomel (Hg2Cl2), monteponite (CdO), and the CdS polymorphs hawleyite and greenockite are calculated, indicating preferential incorporation of neutron-rich isotopes in more oxidized, ionically bonded phases. Finally, field shift energies are related to Mössbauer isomer shifts, and equilibrium mass-independent fractionations for several tin-bearing crystals are calculated from 119Sn spectra. Isomer shift data should simplify calculations of mass-independent isotope fractionations in other elements with Mössbauer isotopes, such as platinum and uranium.

  20. SEQUESTRATION OF SUBSURFACE ELEMENTAL MERCURY (HG0)

    EPA Science Inventory

    Elemental mercury (Hg0) is a metal with a number of atypical properties, which has resulted in its use in myriad anthropogenic processes. However, these same properties have also led to severe local subsurface contamination at many places where it has been used. As...

  1. Mercuric chloride (HgCl2)

    Integrated Risk Information System (IRIS)

    Mercuric chloride ( HgCl2 ) ; CASRN 7487 - 94 - 7 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Nonc

  2. Beryllium abundances in Hg-Mn stars

    SciTech Connect

    Boesgaard, A.M.; Heacox, W.D.; Wolff, S.C.; Borsenberger, J.; Praderie, F.

    1982-08-15

    The Hg-Mn stars show anomalous line strengths of many chemical elements including Be. We have observed the Be ii resonance doublet at lambdalambda 3130, 3131 at 6.7 A mm/sup -1/ in 43 Hg-Mn stars and 10 normal stars in the same temperature range with the coude spectrograph of the 2.24 m University of Hawaii telescope at Mauna Kea. Measured equivalent widths of the two lines and/or the blend of the doublet have been compared with predictions from (1) LTE model atmospheres and (2) non-LTE line formation on non-LTE model atmospheres. (For strong Be ii lines, the LTE calculations result in more Be by factors of 2 to 4 than do the non-LTE calculations.) Overabundances of factors of 20--2 x 10/sup 4/ relative to solar have been found for 75% of the Hg-Mn stars. The 25% with little or no Be are typically among the cooler Hg-Mn stars, but for the stars with Be excesses, there is only marginal evidence for a correlationi of the size of the overabundance and temperature. It is suggested that diffusion driven by radiation pressure is responsible for the observed Be abundance anomalies.

  3. Isotope separation

    DOEpatents

    Bartlett, Rodney J.; Morrey, John R.

    1978-01-01

    A method and apparatus is described for separating gas molecules containing one isotope of an element from gas molecules containing other isotopes of the same element in which all of the molecules of the gas are at the same electronic state in their ground state. Gas molecules in a gas stream containing one of the isotopes are selectively excited to a different electronic state while leaving the other gas molecules in their original ground state. Gas molecules containing one of the isotopes are then deflected from the other gas molecules in the stream and thus physically separated.

  4. Investigating uptake and translocation of mercury species by sawgrass ( Cladium jamaicense ) using a stable isotope tracer technique.

    PubMed

    Mao, Yuxiang; Li, Yanbin; Richards, Jennifer; Cai, Yong

    2013-09-01

    The role of macrophytes in mercury (Hg) cycling in the Florida Everglades ecosystem has not been fully understood. In this study, a stable isotope ((199)Hg(2+)) addition technique was used to trace the methylation, uptake, and translocation of Hg by sawgrass ( Cladium jamaicense ) and quantitatively evaluate the contribution of atmospheric and soil Hg to Hg in sawgrass leaves and below-ground biomass. The results showed that spiked (199)Hg(2+) could be rapidly methylated to monomethylmercury (Me(199)Hg) in the soil of the sawgrass pots. Only small portions of total Hg (THg) and monomethylmercury (MeHg) in the soil could be taken up by sawgrass, indicated by the ratios of T(199)Hg and Me(199)Hg (tracer) concentrations in the sawgrass below-ground biomass (BGBM) over that in the soil (6.50 ± 1.9% and 12.8 ± 3.6% for THg and MeHg, respectively). Concentrations of T(199)Hg (tracer) and Me(199)Hg (tracer) in sawgrass leaves only accounted for 5.50 ± 2.8% and 15.6 ± 4.0%, respectively, of that in the BGBM, implying that the fractions of mercury species transported upward by sawgrass were also small. Statistical analysis (t test) showed that sawgrass preferred MeHg over THg in both uptake and upward translocation. The majority (>90%) of THg in sawgrass leaves were estimated to be obtained from atmospheric Hg, rather than from soil, suggesting that assimilation of atmospheric Hg could increase the overall Hg stock in the Florida Everglades ecosystem. The finding about foliar uptake of Hg is especially important for a better understanding of mercury cycling in the Everglades, given the large amount of sawgrass biomass in this ecosystem. PMID:23885899

  5. Single particle signatures in high-spin, quasicontinuum, states in {sup 193,194}Hg from g-factor measurements.

    SciTech Connect

    Weissman, L.; Mayer, R. H.; Kumbartzki, G.; Benczer-Koller, N.; Broude, C.; Cizewski, J. A.; Hass, M.; Holden, J.; Janssens, R. V. F.; Lauritsen, T.; Lee, I. Y.; Macchiavelli, A. O.; McNabb, D. P.; Satteson, M.; Physics; Weizmann Inst. of Science; Rutgers Univ.; LBNL

    1999-01-14

    The average g factors of high spin, high-excitation energy, quasicontinuum structures in {sup 194,193}Hg were measured by observing the precessions of the angular distributions of {gamma}-ray transitions in several normal-deformation bands that coalesce in the decay of the entry distribution of states. The average g factors of the states leading to the three main bands in the {sup 193,194}Hg isotopes were: {l_angle}g({sup 193}Hg){r_angle}=+0.19(1) and {l_angle}g({sup 194}Hg){r_angle}=+0.26(1), respectively. These average g factors are smaller than the average of the g factors of the high energy states in the three superdeformed bands of {sup 194}Hg, {l_angle}g(SD; {sup 194}Hg){r_angle}=+0.41(8). While the nucleus in the superdeformed well behaves like a rigid rotor, the present results demonstrate the important role played by multiple, quasiparticle neutron configurations in the structure of normal-deformation, highly-excited nuclear states.

  6. Isotopic fractionation during the uptake and elimination of inorganic mercury by a marine fish.

    PubMed

    Xu, Xiaoyu; Wang, Wen-Xiong

    2015-11-01

    This study investigated the mass dependent (MDF) and independent fractionation (MIF) of stable mercury isotopes in fish during the uptake and elimination of inorganic species. Mercury accumulation during the exposure led to re-equilibration of organ isotopic compositions with the external sources, and elimination terminated the equilibrating with isotope ratios moving back to the original values. Generally, the isotopic behaviors corresponded to the changes of Hg accumulation in the muscle and liver, causing by the internal transportation, organ redistribution, and mixing of different sources. A small degree of MDF caused by biotransformation of Hg in the liver was documented during the elimination, whereas MIF was not observed. The absence of MIF during geochemical and metabolic processes suggested that mercury isotopes can be used as source tracers. Additionally, fish liver is a more responsive organ than muscle to track Hg source when it is mainly composed of inorganic species. PMID:26184584

  7. Sources and fate of mercury pollution in Almadén mining district (Spain): Evidences from mercury isotopic compositions in sediments and lichens.

    PubMed

    Jiménez-Moreno, María; Barre, Julien P G; Perrot, Vincent; Bérail, Sylvain; Rodríguez Martín-Doimeadios, Rosa C; Amouroux, David

    2016-03-01

    Variations in mercury (Hg) isotopic compositions have been scarcely investigated until now in the Almadén mining district (Spain), which is one of the most impacted Hg areas worldwide. In this work, we explore and compare Hg isotopic signatures in sediments and lichens from Almadén mining district and its surroundings in order to identify and trace Hg aquatic and atmospheric contamination sources. No statistically significant mass independent fractionation was observed in sediments, while negative Δ(201)Hg values from -0.12 to -0.21‰ (2SD = 0.06‰) were found in lichens. A large range of δ(202)Hg values were reported in sediments, from -1.86 ± 0.21‰ in La Serena Reservoir sites far away from the pollution sources to δ(202)Hg values close to zero in sediments directly influenced by Almadén mining district, whereas lichens presented δ(202)Hg values from -1.95 to -0.40‰ (2SD = 0.15‰). A dilution or mixing trend in Hg isotope signatures versus the distance to the mine was found in sediments along the Valdeazogues River-La Serena Reservoir system and in lichens. This suggests that Hg isotope fingerprints in these samples are providing a direct assessment of Hg inputs and exposure from the mining district, and potential information on diffuse atmospheric contamination and/or geochemical alteration processes in less contaminated sites over the entire hydrosystem. This study confirms the applicability of Hg isotope signatures in lichens and sediments as an effective and complementary tool for tracing aquatic and atmospheric Hg contamination sources and a better constraint of the spatial and temporal fate of Hg released by recent or ancient mining activities. PMID:26774309

  8. Analysis of RFSA Campaign No.2 Dissolver Solution for Hg(I) and Hg(II)

    SciTech Connect

    Holcomb, H.P.

    2001-05-17

    TA 2-1083, under which RFSA processing is conducted, calls for a nominal mercuric ion concentration in the dissolver solution of 0.006M with a maximum of 0.01 M. The second RFSA campaign operated according to these guidelines with the initial Hg(II) concentration being 0.0068 M. Part of this study is to ascertain optimum excess Hg(I) for chloride removal.

  9. Isotopic yield in cold binary fission of even-even 244-258Cf isotopes

    NASA Astrophysics Data System (ADS)

    Santhosh, K. P.; Cyriac, Annu; Krishnan, Sreejith

    2016-05-01

    The cold binary fission of even-even 244-258Cf isotopes has been studied by taking the interacting barrier as the sum of Coulomb and proximity potential. The favorable fragment combinations are obtained from the cold valley plot (plot of driving potential vs. mass number of fragments) and by calculating the yield for charge minimized fragments. It is found that for 244,246,248Cf isotopes highest yield is for the fragments with isotope of Pb (Z = 82) as one fragment, whereas for 250Cf and 252Cf isotopes the highest yield is for the fragments with isotope of Hg (Z = 80) as one fragment. In the case of 254,256,258Cf isotopes the highest yield is for the fragments with Sn (Z = 50) as one fragment. Thus, the fragment combinations with maximum yield reveal the role of doubly magic and near doubly magic nuclei in binary fission. It is found that asymmetric splitting is favored for Cf isotopes with mass number A ≤ 250 and symmetric splitting is favored for Cf isotopes with A > 252. In the case of Cf isotope with A = 252, there is an equal probability for asymmetric and symmetric splitting. The individual yields obtained for the cold fission of 252Cf isotope are compared with the experimental data taken from the γ- γ- γ coincidences technique using Gammasphere.

  10. A physiological role for HgII during phototrophic growth

    NASA Astrophysics Data System (ADS)

    Grégoire, D. S.; Poulain, A. J.

    2016-02-01

    The bioaccumulation of toxic monomethylmercury is influenced by the redox reactions that determine the amount of mercury (Hg) substrate--HgII or Hg0 (refs ,)--that is available for methylation. Phototrophic microorganisms can reduce HgII to Hg0 (ref. ). This reduction has been linked to a mixotrophic lifestyle, in which microbes gain energy photosynthetically but acquire diverse carbon compounds for biosynthesis from the environment. Photomixotrophs must maintain redox homeostasis to disperse excess reducing power due to the accumulation of reduced enzyme cofactors. Here we report laboratory experiments in which we exposed purple bacteria growing in a bioreactor to HgII and monitored Hg0 concentrations. We show that phototrophs use HgII as an electron sink to maintain redox homeostasis. Hg0 concentrations increased only when bacteria grew phototrophically, and when bacterial enzyme cofactor ratios indicated the presence of an intracellular redox imbalance. Under such conditions, bacterial growth rates increased with increasing HgII concentrations; when alternative electron sinks were added, Hg0 production decreased. We conclude that Hg can fulfil a physiological function in bacteria, and that photomixotrophs can modify the availability of Hg to methylation sites.

  11. Magnetic fields of HgMn stars⋆

    NASA Astrophysics Data System (ADS)

    Hubrig, S.; González, J. F.; Ilyin, I.; Korhonen, H.; Schöller, M.; Savanov, I.; Arlt, R.; Castelli, F.; Lo Curto, G.; Briquet, M.; Dall, T. H.

    2012-11-01

    Context. The frequent presence of weak magnetic fields on the surface of spotted late-B stars with HgMn peculiarity in binary systems has been controversial during the two last decades. Recent studies of magnetic fields in these stars using the least-squares deconvolution (LSD) technique have failed to detect magnetic fields, indicating an upper limit on the longitudinal field between 8 and 15 G. In these LSD studies, assumptions were made that all spectral lines are identical in shape and can be described by a scaled mean profile. Aims: We re-analyse the available spectropolarimetric material by applying the moment technique on spectral lines of inhomogeneously distributed elements separately. Furthermore, we present new determinations of the mean longitudinal magnetic field for the HgMn star HD 65949 and the hotter analog of HgMn stars, the PGa star HD 19400, using FORS 2 installed at the VLT. We also give new measurements of the eclipsing system AR Aur with a primary star of HgMn peculiarity, which were obtained with the SOFIN spectropolarimeter installed at the Nordic Optical Telescope. Methods: We downloaded from the European Southern Observatory (ESO) archive the publically available HARPS spectra for eight HgMn stars and one normal and one superficially normal B-type star obtained in 2010. Out of this sample, three HgMn stars belong to spectroscopic double-lined systems. The application of the moment technique to the HARPS and SOFIN spectra allowed us to study the presence of the longitudinal magnetic field, the crossover effect, and quadratic magnetic fields. Results for the HgMn star HD 65949 and the PGa star HD 19400 are based on a linear regression analysis of low-resolution spectra obtained with FORS 2 in spectropolarimetric mode. Results: Our measurements of the magnetic field with the moment technique using spectral lines of several elements separately reveal the presence of a weak longitudinal magnetic field, a quadratic magnetic field, and the

  12. Mass-independent fractionation of mercury isotopes during photochemical reduction in freshwater systems

    NASA Astrophysics Data System (ADS)

    Rose, C. H.; Bergquist, B. A.; Blum, J. D.

    2009-12-01

    Mercury is a globally distributed environmental toxin. Both inorganic and methylated species have severe detrimental effects on humans and animals, but it is methyl mercury (MeHg) that bioaccumulates in food webs and results in significant human exposure via fish consumption. Photochemical reduction of aqueous Hg species to dissolved gaseous Hg(0) can result in a net transfer of Hg from aquatic systems to the atmosphere, making it unavailable for methylation. In addition, photo-reduction of MeHg is an alternative fate to bioaccumulation for this powerful neurotoxin. Both mass-dependent isotope fractionation (MDF) and mass-independent fractionation (MIF) are observed in natural samples. MIF is the deviation in isotope ratios from those predicted by MDF based on 202Hg/198Hg. Bergquist and Blum 2007 showed that aqueous photo-reduction of Hg2+ and MeHg in the presence of dissolved natural organic matter results not only in Rayleigh-type MDF but also significant MIF, with the odd isotopes 199Hg and 201Hg being preferentially retained in the reactant (soluble) phase. Berquist and Blum 2007 also observed that the ratio of the MIF for the odd isotopes was different for each of the photo-reduction pathways (MeHg versus Hg2+) and suggested this ratio could be unique to certain pathways, which might allow identification of photo-reduction among other pathways in natural samples. They also suggested that the magnitude of MIF might relate quantitatively to the amount of photo-reduction Hg undergoes in aqueous systems. To better understand the causes of MIF and its capacity along with MDF as a tool for tracing photo-reduction of Hg, further experiments mimicking the freshwater photo-reduction of Hg2+ and MeHg were carried out. Each species was photo-reduced in the presence of Suwannee River Fulvic Acid with different portions of the electromagnetic spectrum blocked by filters. Bergquist and Blum 2007 suggested the magnetic isotope effect (MIE) as the cause of the MIF they

  13. Dipole Bands in {sup 196}Hg

    SciTech Connect

    Lawrie, J. J.; Lawrie, E. A.; Newman, R. T.; Sharpey-Schafer, J. F.; Smit, F. D.; Msezane, B.; Benatar, M.; Mabala, G. K.; Mutshena, K. P.; Federke, M.; Mullins, S. M.; Ncapayi, N. J.; Vymers, P.

    2011-10-28

    High spin states in {sup 196}Hg have been populated in the {sup 198}Pt({alpha},6n) reaction at 65 MeV and the level scheme has been extended. A new dipole band has been observed and a previously observed dipole has been confirmed. Excitation energies, spins and parities of these bands were determined from DCO ratio and linear polarization measurements. Possible quasiparticle excitations responsible for these structures are discussed.

  14. MBE HgCdTe heterostructure detectors

    NASA Technical Reports Server (NTRS)

    Schulman, Joel N.; Wu, Owen K.

    1990-01-01

    HgCdTe has been the mainstay for medium (3 to 5 micron) and long (10 to 14 micron) wavelength infrared detectors in recent years. Conventional growth and processing techniques are continuing to improve the material. However, the additional ability to tailor composition and placement of doped layers on the tens of angstroms scale using molecular beam epitaxy (MBE) provides the opportunity for new device physics and concepts to be utilized. MBE-based device structures to be discussed here can be grouped into two categories: tailored conventional structures and quantum structures. The tailored conventional structures are improvements on familiar devices, but make use of the ability to create layers of varying composition, and thus band gap, at will. The heterostructure junction can be positioned independently of doping p-n junctions. This allows the small band gap region in which the absorption occurs to be separated from a larger band gap region in which the electric field is large and where unwanted tunneling can occur. Data from hybrid MBE/liquid phase epitaxy (LPE)/bulk structures are given. Quantum structures include the HgTe-CdTe superlattice, in which the band gap and transport can be controlled by alternating thin layers (tens of angstroms thick) of HgTe and CdTe. The superlattice has been shown to exhibit behavior which is non-alloy like, including very high hole mobilities, two-dimensional structure in the absorption coefficient, resonant tunneling, and anisotropic transport.

  15. Reconstructing historical Pb and Hg pollution in NW Spain using multiple cores from the Chao de Lamoso bog (Xistral Mountains)

    NASA Astrophysics Data System (ADS)

    Martínez Cortizas, A.; Peiteado Varela, E.; Bindler, R.; Biester, H.; Cheburkin, A.

    2012-04-01

    We have applied a single-bog multi-core approach to reconstruct historical Pb and Hg accumulation in an ombrotrophic bog from NW Spain, Chao de Lamoso (Xistral Mountains). Mercury was determined using a LECO-ALTEC AMA-254 analyzer, Pb with an EMMA-XRF analyzer and stable lead isotopes (four cores) by Quadrupole ICP-MS. Maximum concentrations were 74-122 μg g-1 for Pb and 142-300 ng g-1 for Hg. Higher variability was found for Hg than for Pb (2-3 times and 1.5 times, respectively). The slopes of the relationship between Hg and Pb cumulative inventories also suggested differences in relative accumulation of both elements. This substantial spatial variability indicates that, compared with Pb, a more extended sampling may be needed for an accurate estimation of Hg accumulation in mires. The isotopic records showed higher and almost constant 206Pb/207Pb ratios (average 1.174 ± 0.004) in the lower sections and a continuous decrease to the surface (minimum 1.141). By using the change in the isotopic composition of Pb we estimated a chronology for the last ˜200 years which enabled and approximation of the temporal trends in metal pollution. Based on the average isotopic composition of the studied cores and the application of a simple binary mixing model, six periods with increasing proportions of pollution Pb were identified: prior to ˜1875 AD, with an average proportion lower than 16%; ˜1875-1910 AD, increasing up to 24%; ˜1910-1950 AD, up to 35%; ˜1950-1970, up to 54%; ˜1970-1980 AD, up to 74%; and after ˜1980 AD, increasing up to 80%. The period with the highest rate of increase in recent (since ˜1900 AD) pollution Pb (equivalent to 2% year-1) seems to have started at the maximum in Pb accumulation around the early 1970s. The Hg records showed a more simple evolution with four main phases: prior to ˜1875 AD with enrichments around 1.5-fold the background, ˜1875-1955 AD with increasing enrichments; from ˜1955 AD to ˜1980 AD with maximum values (up to 4

  16. Hg+Br-->HgBr recombination and collision-induced dissociation dynamics.

    PubMed

    Shepler, Benjamin C; Balabanov, Nikolai B; Peterson, Kirk A

    2007-10-28

    A global potential energy surface has been constructed for the system HgBr+Ar-->Hg+Br+Ar to determine temperature dependent rate constants for the collision-induced dissociation (CID) and recombination of Hg and Br atoms. The surface was decomposed using a many-body expansion. Accurate two-body potentials for HgBr, HgAr, and ArBr were calculated using coupled cluster theory with single and double excitations and a perturbative treatment of triple excitations [CCSD(T)], as well as the multireference averaged coupled pair functional method. Correlation consistent basis sets were used to extrapolate to the complete basis set limit and corrections were included to account for scalar and spin-orbit relativistic effects, core-valence correlation, and the Lamb shift. The three-body potential was computed with the CCSD(T) method and triple-zeta quality basis sets. Quasiclassical trajectories using the final analytical potential surface were directly carried out on the CID of HgBr by Ar for a large sampling of initial rotational, vibrational, and collision energies. The recombination rate of Hg and Br atoms is a likely first step in mercury depletion events that have been observed in the Arctic troposphere during polar sunrise. The effective second order rate constant for this process was determined in this work from the calculated CID rate as a function of temperature using the principle of detailed balance, which resulted in k(T) = 1.2 x 10(-12) cm(3) molecule(-1) s(-1) at 260 K and 1 bar pressure. PMID:17979335

  17. 40 CFR Appendix A to Subpart Uuuuu - Hg Monitoring Provisions

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 15 2012-07-01 2012-07-01 false Hg Monitoring Provisions A Appendix A... Generating Units Pt. 63, Subpt. UUUUU, App. A Appendix A to Subpart UUUUU—Hg Monitoring Provisions 1. General... mercury (Hg) in emissions from electric utility steam generating units, using either a mercury...

  18. 40 CFR 60.4124 - Hg budget permit revisions.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 6 2010-07-01 2010-07-01 false Hg budget permit revisions. 60.4124... Coal-Fired Electric Steam Generating Units Permits § 60.4124 Hg budget permit revisions. Except as provided in § 60.4123(b), the permitting authority will revise the Hg Budget permit, as necessary,...

  19. 40 CFR 60.4124 - Hg budget permit revisions.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 6 2011-07-01 2011-07-01 false Hg budget permit revisions. 60.4124... Coal-Fired Electric Steam Generating Units Permits § 60.4124 Hg budget permit revisions. Except as provided in § 60.4123(b), the permitting authority will revise the Hg Budget permit, as necessary,...

  20. Equilibrium stable-isotope fractionation of thallium and mercury

    NASA Astrophysics Data System (ADS)

    Schauble, E. A.

    2005-12-01

    In this study first-principles quantum mechanical and empirical force-field models are used to estimate equilibrium mass-dependent isotopic fractionations among a variety of thallium and mercury compounds. High-precision MC-ICP-MS measurements have recently uncovered evidence of stable isotope fractionation for many elements, including 2-4‰ variability in the isotopic compositions of thallium[1] (atomic no. 81) and mercury[2] (atomic no. 80). The observed thallium- and mercury-isotope fractionations are remarkable, given that the magnitude of isotopic fractionation typically decreases as atomic number increases[3]. Stable isotope measurements could improve our understanding of geochemical and biogeochemical cycling of both elements, but little is known about the mechanisms driving these fractionations. A better understanding of the chemical processes controlling stable isotope compositions could help maximize the utility of these new geochemical tracers. Standard equilibrium stable isotope fractionation theory holds that the energy driving fractionation comes from isotopic effects on vibrational frequencies, which have generally not been measured. In the present study both quantum-mechanical and empirical force fields are used to estimate unknown frequencies. Results suggest that thallium and mercury fractionations of ≥ 0.5‰ are likely during the relevant redox reactions Tl+ ↔ Tl3+ and HgO ↔ Hg2+. Methyl-mercury and mercury-halide compounds like CH3HgCl will have ~ 1‰ higher 202Hg/198Hg than atomic vapor at room temperature. Fractionations between coexisting Hg2+ species appear to be much smaller, however. 205Tl/203Tl in Tl(H2O)_63+ is predicted to be ~0.5‰ higher than in coexisting Tl+-bearing substances. This result is in qualitative agreement with data from ferromanganese crusts [1], suggesting that Tl3+ in manganese-oxides will have higher 205Tl/203Tl than aqueous Tl+. Equilibrium fractionations for both elements are much smaller than the observed

  1. Electromagnetic moments of odd-A Po193-203,211 isotopes

    NASA Astrophysics Data System (ADS)

    Seliverstov, M. D.; Cocolios, T. E.; Dexters, W.; Andreyev, A. N.; Antalic, S.; Barzakh, A. E.; Bastin, B.; Büscher, J.; Darby, I. G.; Fedorov, D. V.; Fedosseev, V. N.; Flanagan, K. T.; Franchoo, S.; Huber, G.; Huyse, M.; Keupers, M.; Köster, U.; Kudryavtsev, Yu.; Marsh, B. A.; Molkanov, P. L.; Page, R. D.; Sjödin, A. M.; Stefan, I.; Van Duppen, P.; Venhart, M.; Zemlyanoy, S. G.

    2014-03-01

    Hyperfine splitting parameters have been measured for the neutron-deficient odd-mass polonium isotopes and isomers Po193-203g,m, Po209,211. The measurement was performed at the ISOLDE (CERN) online mass separator using the in-source resonance ionization spectroscopy technique. The magnetic dipole moments μ and spectroscopic electric quadrupole moments QS have been deduced. Their implication for the understanding of nuclear structure in the vicinity of the closed proton shell at Z =82 and the neutron mid-shell at N =104 is discussed. For the most neutron-deficient nuclei (A =193,195,197), a deviation of μ and QS from the nearly constant values for heavier polonium nuclei was observed. Particle-plus-rotor calculations with static oblate deformation describe the electromagnetic moments for these nuclei well, provided a gradual increase of a mean deformation when going to lighter masses is assumed for the polonium nuclei with A <198.

  2. Hg and Pt-metals in meteorite carbon-rich residues - Suggestions for possible host phase for Hg

    NASA Technical Reports Server (NTRS)

    Jovanovic, S.; Reed, G. W., Jr.

    1980-01-01

    Carbon-rich and oxide residual phases have been isolated from Allende and Murchison by acid demineralization for the determination of their Hg, Pt-metal, Cr, Sc, Co, and Fe contents. Experimental procedures used eliminated the possibility of exogenous and endogenous contaminant trace elements from coprecipitating with the residues. Large enrichments of Hg and Pt-metals were found in Allende but not in Murchison residues. Hg-release profiles from stepwise heating experiments suggest a sulfide as the host for Hg. Diffusion calculations for Hg based on these experiments indicate an activation energy of 7-8 kcal/mol, the same as that for Hg in troilite from an iron meteorite. This is further support for a sulfide host phase for Hg. Equilibration of Hg with this phase at approximately 900 K is indicated. Reasons for the presence of Pt-metals in noncosmic relative abundances are explored.

  3. First Observations of Laser-Excited Hg3 and Hg2RG Spectra in a Supersonic Expansion Beam

    PubMed

    Koperski; Atkinson; Krause

    1998-02-01

    Triatomic van der Waals complexes of mercury have been observed in a supersonic expansion beam crossed with a laser beam to produce excitation and fluorescence spectra. The expansion beam consisting of mercury and a (noble) carrier gas (RG) was excited in three separate spectral regions: in the vicinity of the Hg 2537 A intercombination line, near the (forbidden) Hg 6(3)P2 <-- 6(1)S0 atomic transition (2200-2290 A), and in the region of the Hg2 G0(+)u <-- X0(+)g transition (1975-2080 A). The resulting spectra, which were recorded in the spectral range 1900-6000 A, contained, in addition to the known Hg, Hg2, and HgRG components, new absorption and fluorescence bands that are ascribed to Hg2RG and Hg3 complexes. Copyright 1998 Academic Press. Copyright 1998Academic Press PMID:9473437

  4. Sediment transport and Hg recovery in Lavaca Bay, as evaluated from radionuclide and Hg distributions

    SciTech Connect

    Santschi, P.H.; Allison, M.A.; Asbill, S.; Perlet, A.B.; Cappellino, S.; Dobbs, C.; McShea, L.

    1999-02-01

    Mercury was released in the late 1960s from a chloralkali facility managed by ALCOA and deposited into sediments of Lavaca Bay, TX. Sediments have recorded this event as a well-defined subsurface concentration maximum. Radionuclide, mercury, X-radiography, and grain size data from sediment cores taken in 1997 at 15 stations in Lavaca bay were used to assess sediment and Hg movements in the bay. Sediment accumulation rates were calculated from bomb fallout nuclide ({sup 137}Cs, {sup 239,240}Pu) peaks in 1963 and from the steady-state delivery of {sup 210}Pb from the atmosphere. Sedimentation rates are highest at near-shore sites near the ALCOA facility and generally decrease away from shore. Sedimentation rates in some areas are likely influenced by anthropogenic activities such as dredging. Particle reworking, as assessed from {sup 7}Be measurements, is generally restricted to the upper 2--7 cm of sediments. Numerical simulations of Hg profiles using measured sedimentation and mixing parameters indicate that at most sites high remnant mercury concentrations at 15--60 cm depth cannot supply substantial amounts of Hg to surface sediments. Assuming no future Hg supplies, Hg concentrations in surface sediments are predicted to decrease exponentially with a recovery half-time of 4 {+-} 2 years.

  5. HgZnTe-based detectors for LWIR NASA applications

    NASA Technical Reports Server (NTRS)

    Patten, Elizabeth A.; Kalisher, Murray H.

    1990-01-01

    The initial goal was to grow and characterize HgZnTe and determine if it indeed had the advantageous properties that were predicted. Researchers grew both bulk and liquid phase epitaxial HgZnTe. It was determined that HgZnTe had the following properties: (1) microhardness at least 50 percent greater than HgCdTe of equivalent bandgap; (2) Hg annealing rates of at least 2 to 4 times longer than HgCdTe; and (3) higher Hg vacancy formation energies. This early work did not focus on one specific composition (x-value) of HgZnTe since NASA was interested in HgZnTe's potential for a variety of applications. Since the beginning of 1989, researchers have been concentrating, however, on the liquid phase growth of very long wavelength infrared (VLWIR) HgZnTe (cutoff approx. equals 17 microns at 65K) to address the requirements of the Earth Observing System (EOS). Since there are no device models to predict the advantages in reliability one can gain with increased microhardness, surface stability, etc., one must fabricate HgZnTe detectors and assess their relative bake stability (accelerated life test behavior) compared with HgCdTe devices fabricated in the same manner. Researchers chose to fabricate HIT detectors as a development vehicle for this program because high performance in the VLWIR has been demonstrated with HgCdTe HIT detectors and the HgCdTe HIT process should be applicable to HgZnTe. HIT detectors have a significant advantage for satellite applications since these devices dissipate much less power than conventional photoconductors to achieve the same responsivity.

  6. The Chevrel phase HgMo6S8

    PubMed Central

    Salloum, Diala; Gougeon, Patrick; Potel, Michel

    2009-01-01

    The crystal structure of HgMo6S8, mercury(II) hexa­molybdenum octa­sulfide, is based on (Mo6S8)S6 cluster units ( symmetry) inter­connected through inter­unit Mo—S bonds. The Hg2+ cations occupy large voids between the different cluster units and are covalently bonded to two S atoms. The Hg atoms and one S atom lie on sites with crystallographic and 3 symmetry, respectively. Refinement of the occupancy factor of the Hg atom led to the composition Hg0.973 (3)Mo6S8. PMID:21583726

  7. Isotopic chirality

    SciTech Connect

    Floss, H.G.

    1994-12-01

    This paper deals with compounds that are chiral-at least in part, due to isotope substitution-and their use in tracing the steric course of enzyme reaction in vitro and in vivo. There are other applications of isotopically chiral compounds (for example, in analyzing the steric course of nonenzymatic reactions and in probing the conformation of biomolecules) that are important but they will not be discussed in this context.

  8. Transuranium isotopes

    SciTech Connect

    Hoffman, D.C.

    1985-12-01

    The needs of the research community for the production of transuranium isotopes, the quantities required, the continuity of production desired, and what a new steady state neutron source would have to provide to satisfy these needs are discussed. Examples of past frontier research which need these isotopes as well as an outline of the proposed Large Einsteinium Activation Program, LEAP, which requires roughly ten times the current production of /sup 254/Es are given. 15 refs., 5 figs., 4 tabs.

  9. Atmospheric mercury (Hg) in the Adirondacks: Concentrations and sources

    SciTech Connect

    Hyun-Deok Choi; Thomas M. Holsen; Philip K. Hopke

    2008-08-15

    Hourly averaged gaseous elemental Hg (GEM) concentrations and hourly integrated reactive gaseous Hg (RGM), and particulate Hg (HgP) concentrations in the ambient air were measured at Huntington Forest in the Adirondacks, New York from June 2006 to May 2007. The average concentrations of GEM, RGM, and HgP were 1.4 {+-} 0.4 ng m{sup -3}, 1.8 {+-} 2.2 pg m{sup -3}, and 3.2 {+-} 3.7 pg m{sup -3}, respectively. RGM represents <3.5% of total atmospheric Hg or total gaseous Hg (TGM: GEM + RGM) and HgP represents <3.0% of the total atmospheric Hg. The highest mean concentrations of GEM, RGM, and HgP were measured during winter and summer whereas the lowest mean concentrations were measured during spring and fall. Significant diurnal patterns were apparent in warm seasons for all species whereas diurnal patterns were weak in cold seasons. RGM was better correlated with ozone concentration and temperature in both warm than the other species. Potential source contribution function (PSCF) analysis was applied to identify possible Hg sources. This method identified areas in Pennsylvania, West Virginia, Ohio, Kentucky, Texas, Indiana, and Missouri, which coincided well with sources reported in a 2002 U.S. mercury emissions inventory. 51 refs., 7 figs., 1 tab.

  10. Bioindication of volcanic mercury (Hg) deposition around Mt Etna (Sicily)

    NASA Astrophysics Data System (ADS)

    Martin, R.; Witt, M. L.; Sawyer, G. M.; Watt, S.; Bagnato, E.; Calabrese, S.; Aiuppa, A.; Delmelle, P.; Pyle, D. M.; Mather, T. A.

    2012-12-01

    Mt. Etna is a major natural source of Hg to the Mediterranean region. Total mercury concentrations, [Hg]tot, in Castanea sativa (sweet chestnut) leaves sampled 7-13 km from Etna's vents (during six campaigns in 2005-2011) were determined using atomic absorption spectroscopy. [Hg]tot in C. sativa was greatest on Etna's SE flank reflecting Hg deposition from the typically overhead volcanic plume. When adjusted for leaf age, [Hg]tot in C. sativa also increased with recent eruptive activity. [Hg]tot in C. sativa was not controlled by [Hg]tot in soils, which instead was greatest on the (upwind) NW flank and correlated strongly with soil organic matter (% Org). Our results suggest that at least ~1% of Hg emitted from Etna is deposited proximally, supporting recent measurement and model results which indicate that GEM (Hg0; the dominant form of Hg in high temperature magmatic gases) is oxidised rapidly to RGM and Hgp in ambient temperature volcanic plumes. Samples of C. sativa and soils were also collected in July and September 2012 alongside SO2 and acid gas diffusion tube samples. These new samples will enable us to investigate Hg accumulation over a single growth season with reference to the exposure of vegetation to volcanic gases and particles.

  11. Mass spectrometric study of the mercury isotopes in the Allende meteorite

    NASA Technical Reports Server (NTRS)

    Nier, A. O.; Schlutter, D. J.

    1986-01-01

    Isotopic abundance ratios for mercury were determined by mass spectrometry in six samples of bulk material and in one sample of chondrules from the Allende meteorite. A primary purpose of the work was to attempt to verify the anomalous ratios reported for Hg-196/Hg-202 by neutron activation. Measurements were made on the mercury released at temperatures of 250, 450, 600 C, and in some cases, higher temperatures. The precision of the measurements was such that if an anomaly of the magnitude reported exists, it should have been seen. The isotopic abundance ratios for the other mercury isotopes were also measured. Within the errors of measurement these agreed with normal terrestrial values.

  12. Process of .sup.196 Hg enrichment

    DOEpatents

    Grossman, Mark W.; Mellor, Charles E.

    1993-01-01

    A simple rate equation model shows that by increasing the length of the photochemical reactor and/or by increasing the photon intensity in said reactor, the feedstock utilization of .sup.196 Hg will be increased. Two preferred embodiments of the present invention are described, namely (1) long reactors using long photochemical lamps and vapor filters; and (2) quartz reactors with external UV reflecting films. These embodiments have each been constructed and operated, demonstrating the enhanced utilization process dictated by the mathematical model (also provided).

  13. Process of [sup 196]Hg enrichment

    DOEpatents

    Grossman, M.W.; Mellor, C.E.

    1993-04-27

    A simple rate equation model shows that by increasing the length of the photochemical reactor and/or by increasing the photon intensity in said reactor, the feedstock utilization of [sup 196]Hg will be increased. Two preferred embodiments of the present invention are described, namely (1) long reactors using long photochemical lamps and vapor filters; and (2) quartz reactors with external UV reflecting films. These embodiments have each been constructed and operated, demonstrating the enhanced utilization process dictated by the mathematical model (also provided).

  14. Growth of HgTe nanowires

    NASA Astrophysics Data System (ADS)

    Selvig, E.; Hadzialic, S.; Skauli, T.; Steen, H.; Hansen, V.; Trosdahl-Iversen, L.; van Rheenen, A. D.; Lorentzen, T.; Haakenaasen, R.

    2006-09-01

    HgTe nanowires nucleated by Au particles have been grown on Si and GaAs substrates by molecular beam epitaxy. The wires are polycrystalline. They evolve from crooked to straight during growth and have rounded to rectangular cross-sections. The widths are in the range 20-500 nm, with lengths up to 4 μm. The height of the nanowires is typically less than the width. The nanowires have been characterized by scanning electron microscopy, x-ray photoelectron spectroscopy, transmission electron microscopy and atomic force microscopy. The effects of substrate material, substrate preparation and growth conditions have been investigated.

  15. Dopants in HgCdTe

    SciTech Connect

    Berding, M.A.; Sher, A.

    1998-12-31

    In this paper the authors discuss the ab initio calculations of native point defect and impurity densities in HgCdTe. Their calculations have explained the experimental finding in general, and in particular have explained the in-active incorporation of the group 7 elements under mercury-deficient conditions; have shown that the group 1 elements have a large fraction of interstitial incorporation, thereby explaining their fast diffusion; and have described a microscopic mechanism for the amphoteric behavior of the group 5 elements. They discuss the trends found among the compounds in terms of the underlying bond strengths to understand why the various elements behave the way they do.

  16. Allyl- iso-propyltelluride, a new MOVPE precursor for CdTe, HgTe and (Hg,Cd)Te

    NASA Astrophysics Data System (ADS)

    Hails, Janet E.; Cole-Hamilton, David J.; Stevenson, John; Bell, William

    2000-06-01

    The use of allyl- iso-propyltelluride as the tellurium precursor for the growth of CdTe, HgTe and (Hg,Cd)Te by metal organic vapour-phase epitaxy has been investigated. It has proved to be an efficient source of tellurium with growth rates for HgTe and (Hg,Cd)Te of up to 10 μm h -1 at 300°C. The best CdTe was grown at 4.5 μm h -1 under Me 2Cd-rich conditions at 300°C in the presence of Hg vapour.

  17. β-delayed γ-ray spectroscopy of ^196Hg and its description within the extended supersymmetry

    NASA Astrophysics Data System (ADS)

    Bernards, C.; Ahmed, T.; Ahn, T.; Deng, C.; Elvers, M.; Heinz, A.; Heinze, S.; Ilie, G.; Jiang, E.; Jolie, J.; Lee, R.; Safran, D.; Shenkov, N.; Thomas, T.; Werner, V.

    2012-10-01

    The concept of nuclear structure SUSY has been observed and investigated in the Au-Pt mass region. It allows the simultaneous description of different nuclei forming so-called supermultiplets. All members of a supermultiplet are distinguished by a constant number of IBFM ν- and π-bosons and -fermions. The most popular example is the `magic square' consisting of ^194,195Pt and ^195,196Au. Recently, efforts were made to investigate the expansion of the Au-Pt supermultiplets by a fifth member: the neighboring even-even Hg isotopes. For the square around ^194Pt, this corresponds the 2-fermion--5-boson supermultiplet member ^196Hg. We report on a γγ angular-correlation experiment to complete the data on low-spin states in ^196Hg. It was performed at WSNL of Yale University using a 28-MeV proton beam activating an enriched ^198HgS target. The γ-rays following the decay of the β-unstable ^196Tl were observed off-beam with the YRAST-Ball Clover array. We present our results and discuss the description of ^196Hg within the extended supersymmetry model.

  18. Tracing mercury pathways in Augusta Bay (southern Italy) by total concentration and isotope determination.

    PubMed

    Bonsignore, M; Tamburrino, S; Oliveri, E; Marchetti, A; Durante, C; Berni, A; Quinci, E; Sprovieri, M

    2015-10-01

    The mercury (Hg) pollution of sediments is the main carrier of Hg for the biota and, subsequently, for the local fish consumers in Augusta Bay area (SE Sicily, Italy), a coastal marine system affected by relevant sewage from an important chlor-alkali factory. This relationship was revealed by the determination of Mass Dependent (MDF) and Mass Independent Fractionation (MIF) of Hg isotopes in sediment, fish and human hair samples. Sediments showed MDF but no MIF, while fish showed MIF, possibly due to photochemical reduction in the water column and depending on the feeding habitat of the species. Benthic and demersal fish exhibited MDF similar to that of sediments in which anthropogenic Hg was deposited, while pelagic organisms evidenced higher MDF and MIF due to photoreduction. Human hair showed high values of δ(202)Hg (offset of +2.2‰ with respect to the consumed fish) and Δ(199)Hg, both associated to fish consumption. PMID:26074159

  19. Quantification of Labile Soil Mercury by Stable Isotope Dilution Techniques

    NASA Astrophysics Data System (ADS)

    Shetaya, Waleed; Huang, Jen-How; Osterwalder, Stefan; Alewell, Christine

    2016-04-01

    Mercury (Hg) is a toxic element that can cause severe health problems to humans. Mercury is emitted to the atmosphere from both natural and anthropogenic sources and can be transported over long distances before it is deposited to aquatic and terrestrial environments. Aside from accumulation in soil solid phases, Hg deposited in soils may migrate to surface- and ground-water or enter the food chain, depending on its lability. There are many operationally-defined extraction methods proposed to quantify soil labile metals. However, these methods are by definition prone to inaccuracies such as non-selectivity, underestimation or overestimation of the labile metal pool. The isotopic dilution technique (ID) is currently the most promising method for discrimination between labile and non-labile metal fractions in soil with a minimum disturbance to soil-solid phases. ID assesses the reactive metal pool in soil by defining the fraction of metal both in solid and solution phases that is isotopically-exchangeable known as the 'E-value'. The 'E-value' represents the metal fraction in a dynamic equilibrium with the solution phase and is potentially accessible to plants. This is carried out by addition of an enriched metal isotope to soil suspensions and quantifying the fraction of metal that is able to freely exchange with the added isotope by measuring the equilibrium isotopic ratio by ICP-MS. E-value (mg kg‑1) is then calculated as follows: E-Value = (Msoil/ W) (CspikeVspike/ Mspike) (Iso1IAspike ‑Iso2IAspikeRss / Iso2IAsoil Rss - Iso1IAsoil) where M is the average atomic mass of the metal in the soil or the spike, W is the mass of soil (kg), Cspike is the concentration of the metal in the spike (mg L‑1), Vspike is the volume of spike (L), IA is isotopic abundance, and Rss is the equilibrium ratio of isotopic abundances (Iso1:Iso2). Isotopic dilution has been successfully applied to determine E-values for several elements. However, to our knowledge, this method has not

  20. 40 CFR 60.4123 - Hg budget permit contents and term.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... from the compliance account of the Hg Budget source covered by the permit. (c) The term of the Hg... renewal of the Hg Budget permit with issuance, revision, or renewal of the Hg Budget source's title...

  1. Electromagnetic Properties of the I π = 11/2‑ isomers in the cadmium isotopes: What can we learn from them?

    NASA Astrophysics Data System (ADS)

    Lei, Y.; Pittel, S.; Jiang, H.

    2016-07-01

    The electromagnetic features of the 11/2‑ isomers in the odd-mass Cd isotopes are shown to exhibit an an anomaly near N = 70. We report shell-model calculations of these isotopes aimed at describing these properties. We find a sudden phase change in the hexadecapole component of the wave functions precisely at N = 70, which gives rise to different linear relations between the Q and μ values before and after N = 70, as needed to reproduce the experimental data. The particle-hole transformation properties associated with a strong subshell closure at N = 70 followed by fairly close-lying neutron orbitals from N = 70 ‑ 82 is suggested as a possible explanation for this phase change.

  2. AQUEOUS REDUCTION OF HG2+ TO HG0 BY HO2 IN THE CMAQ-MODEL

    EPA Science Inventory

    Numerical models of atmospheric mercury are formulated based on the current understanding of mercury chemistry in air and in atmospheric water. Recent evidence that significant reduction of Hg2+ by reaction with HO2 may not actually occur in natural atmospheric water has obviou...

  3. Identification of γ Transitions in ^176-179Hg Using the Recoil Decay Tagging Method.

    NASA Astrophysics Data System (ADS)

    Carpenter, M. P.; Ackermann, D.; Blumenthal, D.; Davids, C.; Fischer, S. M.; Hackman, G.; Janssens, R. V. F.; Khoo, T. L.; Lauritsen, T.; Lister, C. J.; Nisius, D.; Seweryniak, D.; Woods, P. J.; Amro, H.; Brown, T.; Hamilton, J. H.; Ramayya, A. V.; Reviol, W.; Schwartz, J.; Simpson, J.

    1996-05-01

    In light Hg isotopes (100<= N <= 108), shape co-existence has been established close to the ground state where rotational bands built on collective oblate and prolate shapes are observed. While this shape co-existence feature is predicted to be sustained in lighter Hg nuclei, such measurements become increasingly difficult due to the fact that the cross-sections for making these nuclei become very small (<1mb) and fission dominates (σ_fiss > 100 mb). In order to study this shape-coexistence phenomenon all the way to the proton-drip line, we have identified for the first time γ-ray transitions in ^176-179Hg using the Ayeball Ge array coupled to the Fragment Mass Analyzer. In order to assign γ transitions to a particular nuclide, the recoil decay tagging method was utilized, a technique which correlates γ-rays emitted from excited residues with the charged particle radioactivity of their decay. This work is supported by the DOE under contract W-31-109-ENG-38.

  4. Cavity-enhanced parity-nonconserving optical rotation in metastable Xe and Hg.

    PubMed

    Bougas, L; Katsoprinakis, G E; von Klitzing, W; Sapirstein, J; Rakitzis, T P

    2012-05-25

    We propose the measurement of cavity-enhanced parity-nonconserving (PNC) optical rotation in several transitions of metastable Xe and Hg, including Xe (2P(3/2)(o))6s(2)[3/2](2)(o)→(2P(1/2)(o))6s(2)[1/2](1)(o) and Hg 6s6p (3)P(2)(o)→6s6p (1)P(1)(o), with calculated amplitude ratios of E(1)(PNC)/M1=11×10(-8) and 10×10(-8), respectively. We demonstrate the use of a high-finesse bow-tie cavity with counterpropagating beams and a longitudinal magnetic field, which allows the absolute measurement of chiral optical rotation, with a path length enhancement of about 10(4), necessary for PNC measurement from available column densities of 10(14) cm(-2) for metastable Xe or Hg. Rapid PNC-signal reversal, allowing robust background subtraction, is achieved by shifting the cavity resonance to an opposite polarization mode or by inverting the magnetic field. The precise measurement of isotope and nuclear-spin dependent E(1)(PNC) amplitudes provides a sensitive low-energy test of the standard model. PMID:23003234

  5. ISOTOPE SEPARATORS

    DOEpatents

    Bacon, C.G.

    1958-08-26

    An improvement is presented in the structure of an isotope separation apparatus and, in particular, is concerned with a magnetically operated shutter associated with a window which is provided for the purpose of enabling the operator to view the processes going on within the interior of the apparatus. The shutier is mounted to close under the force of gravity in the absence of any other force. By closing an electrical circuit to a coil mouated on the shutter the magnetic field of the isotope separating apparatus coacts with the magnetic field of the coil to force the shutter to the open position.

  6. Chronologically matched toenail-Hg to hair-Hg ratio: temporal analysis within the Japanese community (U.S.)

    PubMed Central

    2012-01-01

    Background Toenail-Hg levels are being used as a marker of methylmercury (MeHg) exposure in efforts to associate exposure with effects such as cardiovascular disease. There is a need to correlate this marker with more established biomarkers that presently underlie existing dose–response relationships in order to compare these relationships across studies. Methods As part of the Arsenic Mercury Intake Biometric Study, toenail clippings were collected at three time points over a period of one year amongst females from within the population of Japanese living near Puget Sound in Washington State (US). Variability in temporal intra-individual toenail-Hg levels was examined and chronologically matched hair and toenail samples were compared to more accurately define the toxicokinetic variability of Hg levels observed between the two compartments. Results Mean toenail-Hg values (n=43) for the 1st, 2nd and 3rd visits were 0.60, 0.60 and 0.56 ng/mg. Correlations were as follows: r=0.92 between 1st and 2nd clinic visits, r=0.75 between 1st and 3rd visits and r=0.87 between 2nd and 3rd visits. With few exceptions, toenail-Hg values from any visit were within 50-150% of the individual’s mean toenail-Hg level. Nearly all participants had less than a two-fold change in toenail-Hg levels across the study period. A regression model of the relationship between toenail-Hg and hair-Hg (n = 41) levels representing the same time period of exposure, gave a slope (Hg ng/mg) of 2.79 for hair relative to toenail (r=0.954). Conclusions A chronologically matched hair-Hg to toenail-Hg ratio has been identified within a population that consumes fish regularly and in quantity. Intra-individual variation in toenail-Hg levels was less than two-fold and may represent dietary-based fluctuations in body burden for individuals consuming various fish species with different contaminant levels. The chronologically matched ratio will be useful for relating MeHg exposure and dose–response derived

  7. Distribution and excretion of Cd, Hg, methyl-Hg and ZS in the predatory beetle Pterostichus niger (Coleoptera: Carabidae)

    SciTech Connect

    Lindqvist, L.; Block, M.; Tjaelve, H.

    1995-07-01

    Excretion and distribution of cadmium (Cd), and mercury (Hg), methylmercury (methyl-Hg), and zinc (Zn) were studied in the predatory beetle, Pterostichus niger. Specimens of P. niger were fed with insect larvae containing {sup 109}Cd, {sup 203}Hg, methyl-{sup 203}Hg, or {sup 65}Zn. After ingestion of the larvae, the metal contents in the beetles were measured daily for 30 d by {gamma}-spectrometry. Additional beetles were used for autoradiography 5, 15, and 19 d after ingestion of the metals. Excretion of the metals was fast during an initial interval but occurred thereafter at a slow rate. After 2 weeks, the contents of Cd and inorganic Hg had decreased to approximately 1% of the ingested amounts. For Zn and methyl-Hg, higher levels were retained in the beetles. Thus after 30 d, Zn content was 20% of the ingested amount, whereas for methyl-Hg 60% was retained in the body. Autoradiography showed high levels of all metals in the gut. For methyl-Hg, in contrast to inorganic Hg, there was also an evenly distributed labelling in most body tissues. This labelling was also seen for Zn, although at a lower lever than for methyl-Hg. Cadmium showed a localization in the integument, which was not seen for the other metals. The results show that patterns of uptake and excretion of the examined metals in P. niger vary considerably and that the distribution picture show specific features for the individual metals.

  8. Shock-induced changes in HgO powder

    SciTech Connect

    Venturini, E.L.; Newcomer, P.P.; Morosin, B.; Holman, G.T.; Dunn, R.G.; Graham, R.A.

    1995-10-01

    Powder compacts of HgO were subjected to explosively-generated shock-wave loading in Sandia Bear fixtures and recovered for analysis. Although XRD powder spectra show only the orthorhombic form of HgO in both the as-received and recovered samples, XRD line profiles and TEM indicate up to an order of magnitude increase in crystallite size. Magnetic data reveal a superconducting transition below 4.2 K that is attributed to metallic {alpha}-Hg formed by a partial, shock-induced decomposition of the HgO, consistent with TEM identification of {alpha}-Hg particles using a cold stage. In addition, paramagnetic impurities present in the as-received HgO powder appear to be partially converted to a ferromagnetic or ferrimagnetic phase that dominates the magnetic properties of the recovered powder. The amounts of both the superconducting and ferromagnetic phases vary strongly with position within the shock recovery capsules.

  9. Microtubes and corrugations fabricated from strained ZnTe/CdHgTe/HgTe/CdHgTe heterofilms with 2D electron-hole gas in the HgTe quantum well

    NASA Astrophysics Data System (ADS)

    Mutilin, S. V.; Soots, R. A.; Vorob'ev, A. B.; Ikusov, D. G.; Mikhailov, N. N.; Prinz, V. Ya

    2014-07-01

    Variously shaped shells were fabricated from strained ZnTe/CdTe/CdHgTe/HgTe/CdHgTe heterofilms that contained a HgTe quantum well populated simultaneously with electrons and holes. The radius of curvature of formed tubes proved to be 12 µm and the period of corrugations about 20 µm. Such a curvature induces a 1.2% deformation in the HgTe layer sufficient for the occurrence of notable band-edge shifts in this layer and causes a transition of the band structure from a semiconductor to a semi-metal state. Curved HgTe-based films offer potential in studying surfaces where topological insulating states are interfaced with semiconductor states.

  10. Status of LWIR HgCdTe infrared detector technology

    NASA Technical Reports Server (NTRS)

    Reine, M. B.

    1990-01-01

    The performance requirements that today's advanced Long Wavelength Infrared (LWIR) focal plane arrays place on the HgCdTe photovoltaic detector array are summarized. The theoretical performance limits for intrinsic LWIR HgCdTe detectors are reviewed as functions of cutoff wavelength and operating temperature. The status of LWIR HgCdTe photovoltaic detectors is reviewed and compared to the focal plane array (FPA) requirements and to the theoretical limits. Emphasis is placed on recent data for two-layer HgCdTe PLE heterojunction photodiodes grown at Loral with cutoff wavelengths ranging between 10 and 19 microns at temperatures of 70 to 80 K. Development trends in LWIR HgCdTe detector technology are outlined, and conclusions are drawn about the ability for photovoltaic HgCdTe detector arrays to satisfy a wide variety of advanced FPA array applications.

  11. Oxidative stress in MeHg-induced neurotoxicity

    SciTech Connect

    Farina, Marcelo; Aschner, Michael; Rocha, Joao B.T.

    2011-11-15

    Methylmercury (MeHg) is an environmental toxicant that leads to long-lasting neurological and developmental deficits in animals and humans. Although the molecular mechanisms mediating MeHg-induced neurotoxicity are not completely understood, several lines of evidence indicate that oxidative stress represents a critical event related to the neurotoxic effects elicited by this toxicant. The objective of this review is to summarize and discuss data from experimental and epidemiological studies that have been important in clarifying the molecular events which mediate MeHg-induced oxidative damage and, consequently, toxicity. Although unanswered questions remain, the electrophilic properties of MeHg and its ability to oxidize thiols have been reported to play decisive roles to the oxidative consequences observed after MeHg exposure. However, a close examination of the relationship between low levels of MeHg necessary to induce oxidative stress and the high amounts of sulfhydryl-containing antioxidants in mammalian cells (e.g., glutathione) have led to the hypothesis that nucleophilic groups with extremely high affinities for MeHg (e.g., selenols) might represent primary targets in MeHg-induced oxidative stress. Indeed, the inhibition of antioxidant selenoproteins during MeHg poisoning in experimental animals has corroborated this hypothesis. The levels of different reactive species (superoxide anion, hydrogen peroxide and nitric oxide) have been reported to be increased in MeHg-exposed systems, and the mechanisms concerning these increments seem to involve a complex sequence of cascading molecular events, such as mitochondrial dysfunction, excitotoxicity, intracellular calcium dyshomeostasis and decreased antioxidant capacity. This review also discusses potential therapeutic strategies to counteract MeHg-induced toxicity and oxidative stress, emphasizing the use of organic selenocompounds, which generally present higher affinity for MeHg when compared to the classically

  12. Lithography process for patterning HgI2 photonic devices

    DOEpatents

    Mescher, Mark J.; James, Ralph B.; Hermon, Haim

    2004-11-23

    A photolithographic process forms patterns on HgI.sub.2 surfaces and defines metal sublimation masks and electrodes to substantially improve device performance by increasing the realizable design space. Techniques for smoothing HgI.sub.2 surfaces and for producing trenches in HgI.sub.2 are provided. A sublimation process is described which produces etched-trench devices with enhanced electron-transport-only behavior.

  13. Ruditapes philippinarum and Ruditapes decussatus under Hg environmental contamination.

    PubMed

    Velez, Cátia; Galvão, Petrus; Longo, Renan; Malm, Olaf; Soares, Amadeu M V M; Figueira, Etelvina; Freitas, Rosa

    2015-08-01

    The native species Ruditapes decussatus and the invasive species Ruditapes philippinarum have an important ecological role and socio-economic value, from the Atlantic and Mediterranean to the Indo-Pacific region. In the aquatic environment, they are subjected to the presence of different contaminants, such as mercury (Hg) and its methylated form, methylmercury (MeHg). However, few studies have assessed the impacts of Hg on bivalves under environmental conditions, and little is known on bivalve oxidative stress patterns due to Hg contamination. Therefore, this study aims to assess the Hg contamination in sediments as well as the concentration of Hg and MeHg in R. decussatus and R. philippinarum, and to identify the detoxification strategies of both species living in sympatry, in an aquatic system with historical Hg contamination. The risk to human health due to the consumption of clams was also evaluated. The results obtained demonstrated that total Hg concentration found in sediments from the most contaminated area was higher than the maximum levels established by Sediment Quality Guidelines. This study further revealed that the total Hg and MeHg accumulation in both species was strongly correlated with the total Hg contamination of the sediments. Nonetheless, the THg concentration in both species was lower than maximum permissible limits (MPLs) of THg defined by international organizations. R. decussatus and R. philippinarum showed an increase in lipid peroxidation levels along with the increase of THg accumulation by clams. Nevertheless, for both species, no clear trend was obtained regarding the activity of antioxidant (superoxide dismutase, catalase) and biotransformation (glutathione S-transferase) enzymes and metallothioneins with the increase of THg in clams. Overall, the present work demonstrated that both species can be used as sentinel species of contamination and that the consumption of these clams does not constitute a risk for human health. PMID

  14. Superdeformation studies in {sup 191}Hg

    SciTech Connect

    Carpenter, M.P.; Janssens, R.V.F.; Crowell, B.

    1995-08-01

    Superdeformation in the A {approximately} 190 region was first observed in {sup 191}Hg from an experiment performed at ATLAS using the Argonne Notre Dame {gamma}-ray facility. We recently revisited the study of superdeformation in this nucleus using Gammasphere and the {sup 160}Gd({sup 36}S,5n) and {sup 174}Yb({sup 22}Ne,5n) reactions at 172 and 120 MeV in order to populate and measure states in the second well. The goal of the experiment was to identify new bands in the data, and thus allow us to gain understanding on the relative placement of single particle orbitals near the N = 112 SD shell gap. From an analysis of the data, the three previously identified SD bands were extended, and their feeding into the yrast states delineated. Two new SD bands were observed and preliminary evidence for a third new band was obtained as well.

  15. Multilayered (Hg,Cd)Te infrared detector

    NASA Technical Reports Server (NTRS)

    Rae, W. G.

    1977-01-01

    Multilayered mercury-cadmium telluride photoconductive detectors were developed which are capable of providing individual coverage of three separate spectral wavelength bands without the use of beam splitters. The multilayered "three-color" detector on a single dewar takes the place of three separate detector/filter/dewar units and enables simpler and more reliable mechanical and optical designs for multispectral scanners and radiometers. Wavelength channel design goals (in micrometers) were: 10.1 to 11.0, 11.0 to 12.0, and 13.0. Detectivity for all channels was 1 x 10 to the 10th power cm-Hz 1/2/Watt. A problem occurred in finding an epoxy layer which had good infrared transmission properties and which also was chemically and mechanically compatible with HgCdTe processing techniques. Data on 6 candidate bonding materials are surveyed and discussed.

  16. Observation of superdeformation in sup 191 Hg

    SciTech Connect

    Moore, E.F.; Janssens, R.V.F.; Chasman, R.R.; Ahmad, I.; Khoo, T.L.; Wolfs, F.L.H.; Ye, D.; Beard, K.B.; Benet, Ph.; Grabowski, Z.W.; Cizewski, J.A.; Drigert, M.W.; Notre Dame Univ., IN; Purdue Univ., Lafayette, IN; Rutgers--the State Univ., New Brunswick, NJ; Idaho National Engineering Lab., Idaho Falls, ID )

    1989-01-01

    The first observation of superdeformation in the A {approx equal} 190 mass region is reported. A rotational band of 12 transitions with an average energy spacing of 37 keV, an average moment of inertia of 110 {Dirac h}{sup 2} MeV{sup {minus}1}, and an average quadrupole moment of 18 {plus minus} 3 eb has been observed in {sup 191}Hg. These results are in excellent agreement with a calculation that predicts an ellipsoidal axis ratio of 1.65:1 for the superdeformed shape in this nucleus. Evidence for another discrete superdeformed band and superdeformed structures in the quasi-continuum was also found in the data. 19 refs., 6 figs.

  17. Density of liquid Hg(1-x)Cd(x)Te

    NASA Technical Reports Server (NTRS)

    Chandra, D.; Holland, L. R.

    1983-01-01

    Negative thermal expansion has been established in liquid Hg(1-x)Cd(x)Te for x less than 0.2 employing a pycnometric method. Pure HgTe increases in density from its melting point at 670 C to a maximum value at 750 C, where normal thermal expansion progressively resumes. The dependence of density on temperature for liquid Hg(1-x)Cd(x)Te arises almost exclusively from the HgTe portion of the melt, while CdTe acts as a diluent. The temperature corresponding to the maximum density changes slightly with composition, increasing by about 5 C for x = 0.1.

  18. Shock-induced defects in HgO

    SciTech Connect

    Morosin, B.; Venturini, E.L.; Holman, G.T.; Newcomer, P.N.; Dunn, R.G.; Graham, R.A.

    1995-09-01

    Powder compacts of HgO have been subjected to shock-loading and preserved for postshock analysis to understand its reactivity and stability under transient temperature-pressure excursions. Recovered samples indicate several solid state reactions which are dependent on shock conditions. Metallic Hg is recovered in small amounts in the HgO compact as well as an as-yet unidentified ferromagnetic impurity not present in the as-received HgO powder. Further, there is evidence of reaction with the Cu capsule, forming an intermetallic alloy.

  19. First results from the Goddard High-Resolution spectrograph - High-resolution observations of the 1942 A resonance line of HG II in the chemically peculiar B star, Chi Lupi

    NASA Technical Reports Server (NTRS)

    Leckrone, David S.; Wahlgren, Glenn M.; Johansson, Sveneric G.

    1991-01-01

    The Goddard High-Resolution Spectrograph on the HST has been used to obtain high S/N observations of the sharp-lined, Hg- and Pt-rich B-type star, Chi Lupi, with a resolving power of 87,000. The observations reveal a level of spectroscopic detail never before observed at ultraviolet wavelengths for any star other than the sun. Concentrating on the region around the resonance line of Hg II at 1942 A, the profile and central position of this line confirm beyond doubt that the Hg isotope anomaly in Chi Lupi is real and extreme, with Hg being heavily concentrated in the form of Hg-204. The problems in atomic physics which impair the accurate analysis of spectra of this quality are emphasized.

  20. Anadromous char as an alternate food choice to marine animals: a synthesis of Hg concentrations, population features and other influencing factors.

    PubMed

    Evans, Marlene S; Muir, Derek C G; Keating, Jonathan; Wang, Xiaowa

    2015-03-15

    This study was conducted to confirm sporadic measurements made over the late 1970s to the early 1990 s which determined that mercury (Hg) concentrations were low in anadromous char across Arctic and subarctic Canada including northern Québec and Labrador. Over 2004-2013, anadromous char populations across northern Canada were investigated at 20 sites for Hg concentrations and life history characteristics. Hg concentrations were extremely low in anadromous char muscle, typically <0.05 μg/g (wet weight) and, at each location, generally increased with fish length, age and nitrogen isotope (δ(15)N) ratio and decreased with condition factor and %lipid; correlations with carbon isotope (δ(13)C) ratio were inconsistent. Location and year were significant variables influencing Hg concentrations over the study area; longitude and latitude also were significant influencing variables. Char length, weight, age, condition factor and lipid content explained additional variance. A tendency towards higher Hg concentrations with increasing latitude may be partially related to decreasing growth of char towards the north. However, Hg concentrations in char were positively correlated with growth rates suggesting that Hg concentrations in char also were higher in the more productive study areas, including to the west where mainland riverine inputs of terrestrial carbon, nutrients, and Hg were greater. The data base for assessing time trends in char was limited by the small number of years investigated at most locations, variable fish size across years, small sample size, etc. Where temporal trends were detected, they were of increase on the long term (1970s, 1980s or early 1990 s to the present) but of decrease on the short term (early 2000s to present) with Nain (Labrador) showing the converse pattern. Higher Hg concentrations were also related to lower condition factor and cooler springs. Hg concentrations in anadromous char are compared with other terrestrial, aquatic and marine

  1. Seasonal and Diurnal Variations of Hg(0) Over New England

    NASA Astrophysics Data System (ADS)

    Mao, H.; Talbot, R.; Sigler, J.; Sive, B.; Hegarty, J.

    2007-12-01

    Diurnal to interannual variability of Hg° over New England was investigated using multiple years of Hg° measurements at two inland sites, Thompson Farm (TF, 43.11° N, 70.95° W, 24 m, 25 km inland) and Pac Monadnock (PM, 42.86° N, 71.88° W, 700 m, 180 km inland), and one summer of measurements from a marine site, Appledore Island (AI, 42.97° N, 70.62° W, sea level), from the University of New Hampshire AIRMAP observing network. Possible sources were identified via a thorough examination of relationships between Hg° and a number of trace gases, e.g., CO, CO2, CH4, NOy, NO, SO2, and VOCs. The measurements of Hg at TF showed distinct seasonality with an annual maxima in late winter - early spring and a minima in early fall, with large day-to-day variation. A decreasing trend in the mixing ratio of Hg over the time period of March - September occurred at a rate of 0.5 - 0.6 ppqv d-1 for all years except 2004 (0.3 ppqv d-1). Measurements of Hg° at the elevated site PM exhibited much smaller daily and annual variation, particularly reflected in the slower warm season decline (relative to TF) of 0.2 and 0.3 ppqv d-1 in 2005 and 2006 respectively. The AI data appeared to track the variation observed at TF albeit with much higher minima. Hg° was correlated most strongly with CO and NOy in winter suggesting that anthropogenic emissions were the primary source of Hg° . Applying the Hg° - CO relationship, we found that the seasonally averaged Hg° mixing ratio of ~160 ppqv at PM can be considered the regional background level. The positive Hg° -NOy correlation along the lower boundary of all data points indicated dry deposition as a stronger sink for Hg° than suggested by previous studies. We estimated a dry deposition velocity for Hg° of 0.17 - 0.20 cm s-1, and a lifetime of ~11 days in the local PBL at TF. Correlation between Hg° and CHBr3 at both TF and AI suggested a role of the oceanic source influencing the ambient levels of Hg° in the marine and coastal

  2. Knight Shift vs Hole Concentration in Hg1201 and Hg1212

    NASA Astrophysics Data System (ADS)

    Itoh, Yutaka

    We studied the hole concentration dependences of 63Cu Knight shifts in single-CuO2-layer high-Tc cuprate superconductors HgBa2CuO4+δ and double-layer HgBa2CaCu2O6+δ. We found that the spin Knight shift at room temperature as a function of the hole concentration in the single-layer superconductor is different from that in the double-layer superconductor. Two type relations between the spin Knight shift and the hole doping level serve to estimate the individual hole concentrations of the non-equivalent CuO2 planes in a unit cell.

  3. Atmospheric mercury (Hg) in the Adirondacks: concentrations and sources.

    PubMed

    Choi, Hyun-Deok; Holsen, Thomas M; Hopke, Philip K

    2008-08-01

    Hourly averaged gaseous elemental Hg (GEM) concentrations and hourly integrated reactive gaseous Hg (RGM), and particulate Hg (Hg(p)) concentrations in the ambient air were measured at Huntington Forest in the Adirondacks, New York from June 2006 to May 2007. The average concentrations of GEM, RGM, and Hg(p) were 1.4 +/- 0.4 ng m(-3), 1.8 +/- 2.2 pg m(-3), and 3.2 +/- 3.7 pg m(-3), respectively. RGM represents < 3.5% of total atmospheric Hg or total gaseous Hg (TGM: GEM + RGM) and Hg(p) represents < 3.0% of the total atmospheric Hg. The highest mean concentrations of GEM, RGM, and Hg(p) were measured during winter and summer whereas the lowest mean concentrations were measured during spring and fall. Significant diurnal patterns were apparent in warm seasons for all species whereas diurnal patterns were weak in cold seasons. RGM was better correlated with ozone concentration and temperature in both warm (rho (RGM - ozone) = 0.57, p < 0.001; rho (RGM - temperature) = 0.62, p < 0.001) and cold seasons (rho (RGM - ozone) = 0.48, p = 0.002; rho (RGM - temperature) = 0.54, p = 0.011) than the other species. Potential source contribution function (PSCF) analysis was applied to identify possible Hg sources. This method identified areas in Pennsylvania, West Virginia, Ohio, Kentucky, Texas, Indiana, and Missouri, which coincided well with sources reported in a 2002 U.S. mercury emissions inventory. PMID:18754488

  4. Cd and Hg ions stimulate cell membrane potassium conductance

    SciTech Connect

    Jungwirth, A.; Paulmichl, M.; Lang, F. )

    1989-02-09

    Intracellular microelectrodes have been applied to study the effect of cadmium (Cd) and mercury (Hg) ions on cultured renal epitheloid Madin Darby Canine Kidney (MDCK) cells. Within 10 seconds Cd and within 50 seconds Hg hyperpolarize the cell membrane from - 53 {plus minus} 1 mV to - 68 {plus minus} 1 mV and - 67 {plus minus} 1 mV, resp., increase the potassium selectivity of the cell membrane (tk) from 0.33 {plus minus} 0.02 to 0.64 {plus minus} 0.03 and 0.77 {plus minus} 0.02, resp., and reduce the apparent cell membrane resistance from 40 {plus minus} 2 MOhm to 27 {plus minus} 2 MOhm and 22 {plus minus} 2 MOhm, resp.. Thus, both, Cd and Hg hyperpolarize the cell membrane by enhancement of the potassium conductance. The concentration required to elicit half maximal hyperpolarization is some 400 nmol/1 for either, Cd or Hg. Barium (1 mmol/1) depolarizes the cell membrane to - 34 {plus minus} 1 mV and virtually abolishes tk in the absence of Cd and Hg. In the presence of barium Cd leads to a transient, Hg to a sustained reappearance of tk and hyperpolarization. Thus, the Cd induced potassium conductance is blocked by barium with delay, the Hg induced potassium conductance is insensitive to barium. Quinidine (1 mmol/1) depolarizes the cell membrane to - 3 {plus minus}1 mV and abolishes the effect of both, Cd and Hg. In the nominal absence of extracellular calcium Cd leads to transient, Hg to sustained increase of tk and hyperpolarization of the cell membrane. In conclusion, both, CD and Hg at the low concentrations encountered during Cd and Hg intoxication enhance potassium conductance of MDCK cell membranes. However, the channels activated apparently differ.

  5. Partitioning and kinetics of methylmercury among organs in captive mink (Neovison vison): A stable isotope tracer study.

    PubMed

    Evans, R Douglas; Hickie, Brendan; Rouvinen-Watt, Kirsti; Wang, Wei

    2016-03-01

    Despite the importance of methylmercury (MeHg) as a neurotoxin, we have relatively few good data on partitioning and kinetics of MeHg among organs, particularly across the blood-brain barrier, for mammals that consume large quantities of fish. The objective of this study was to determine the partition coefficients between blood and brain, liver and kidney and fur for MeHg under steady-state conditions and to measure the half-lives for MeHg in these organs. Captive mink (Neovison vison) were fed a diet enriched with two stable isotopes of Hg, Me(199)Hg and Me(201)Hg for a period of 60 days. After a period of 10 days the diet was changed to contain only Me(201)Hg so that, between days 10 and 60, we were able to measure both uptake and elimination rates from blood, brain, liver kidney and fur. Liver and kidney response was very rapid, closely following changes in blood concentrations but there was a small lag time between peak blood concentrations and peak brain concentrations. Half-lives for MeHg were 15.4, 10.2 and 13.4 days for brain, liver and kidney, respectively. There was no measurable conversion of the MeHg to inorganic Hg (IHg) in the brain over the 60 day period, unlike in liver and kidney. PMID:26855415

  6. Calculation of the energetics for the oligomerization of gas phase HgO and HgS and for the solvolysis of crystalline HgO and HgS.

    PubMed

    Tossell, J A

    2006-02-23

    Recent experimental studies indicate that gaseous elemental Hg (GEM) is rapidly oxidized to Hg(II) compounds, known collectively as reactive gaseous Hg (RGM), in Arctic and Antarctic regions after polar sunrise. The reduction in GEM is correlated with a reduction in surface O(3) concentration, which is thought to be caused by photochemically initiated catalytic reactions involving halogen species, particularly Br and BrO. Initially, the reaction of Hg(0) and BrO to produce HgO and Br was thought to be the dominant reaction, but recent theoretical studies have decisively shown that this reaction is highly endoergic due to the low stability of monomeric gas-phase HgO. This result is in conflict with experimental data on the energetics of the species existing in the vapor over heated HgO (s). One possible explanation for this discrepancy is the existence of highly stable oligomers formed from HgO. Recent high-level quantum calculations on the dimers of HgO and HgS support this concept. In the present work, we systematically examine the structures, stabilities, and other properties of closed (HgX)(n)() ring-type oligomers, n = 2, 3, 4, and 6, X = O, S, as well as infinite one-dimensional (1D) polymers of HgX (studied by using the periodic boundary condition DFT implementation in GAUSSIAN03). We find that the HgX ring oligomers become systematically more stable (per HgX unit) as n increases but that this stability levels off around n = 4-6. We also find that the 1D chain polymers are only marginally more stable than the n = 6 oligomers. To estimate the energies of interaction between the chains in the 3-dimensional (3D) crystal structures of HgX (s), we adopt a cluster model and use the MP2 method to describe the interchain dispersion interactions. We have also obtained optimized geometries for open chain triplets for the dimers, finding them to be substantially more stable than the closed ringlike dimeric species previously described. Trends in relative energies and

  7. Tracking the fate of mercury in the fish and bottom sediments of Minamata Bay, Japan, using stable mercury isotopes.

    PubMed

    Balogh, Steven J; Tsui, Martin Tsz-Ki; Blum, Joel D; Matsuyama, Akito; Woerndle, Glenn E; Yano, Shinichiro; Tada, Akihide

    2015-05-01

    Between 1932 and 1968, industrial wastewater containing methylmercury (MeHg) and other mercury (Hg) compounds was discharged directly into Minamata Bay, Japan, seriously contaminating the fishery. Thousands of people who consumed tainted fish and shellfish developed a neurological disorder now known as Minamata disease. Concentrations of total mercury (THg) in recent fish and sediment samples from Minamata Bay remain higher than those in other Japanese coastal waters, and elevated concentrations of THg in sediments in the greater Yatsushiro Sea suggest that Hg has moved beyond the bay. We measured stable Hg isotope ratios in sediment cores from Minamata Bay and the southern Yatsushiro Sea and in archived fish from Minamata Bay dating from 1978 to 2013. Values of δ(202)Hg and Δ(199)Hg in Yatsushiro Sea surface sediments were indistinguishable from those in highly contaminated Minamata Bay sediments but distinct from and nonoverlapping with values in background (noncontaminated) sediments. We conclude that stable Hg isotope data can be used to track Minamata Bay Hg as it moves into the greater Yatsushiro Sea. In addition, our data suggest that MeHg is produced in bottom sediments and enters the food web without substantial prior photodegradation, possibly in sediment porewaters or near the sediment-water interface. PMID:25877383

  8. ADAPTATION OF AQUATIC MICROBIAL COMMUNITIES TO HG(2+) STRESS

    EPA Science Inventory

    The mechanism of adaptation to Hg(2+) in four aquatic habitats was studied by correlating microbially mediated Hg(2+) volatilization with the adaptive state of the exposed communities. Structural and functional parameters indicated that adaptation of all four communities was stim...

  9. Diel variations in photoinduced oxidation of Hg0 in freshwater.

    PubMed

    Garcia, Edenise; Poulain, Alexandre J; Amyot, Marc; Ariya, Parisa A

    2005-05-01

    Experiments have been conducted to determine diel variations in photoinduced Hg0 oxidation in lake water under natural Hg0(aq) concentrations. Pseudo-first-order rates of photooxidation (k') were calculated for water freshly collected in a Canadian Shield lake, Lake Croche (45 degrees 56' N, 74 degrees 00' W), at different periods of the day and subsequently incubated in the dark. Hg0 oxidation rates ranged from 0.02 to 0.07 h(-1), increasing from sunrise to noon and then decreasing throughout the remainder of the day. These changes paralleled those in sunlight intensity integrated over 1 h preceding water collection, and suggested that the water freshly collected in daylight was rich in photochemically produced Hg0 oxidants. It was also estimated that under intense solar radiation, even if oxidation rates reached a peak, reduction of Hg(II) was the prevalent redox process. Inversely, Hg0 oxidation overcame DGM production during the night or at periods of weaker light intensity. Overall, these findings explain the decreases in the DGM pool generally observed overnight. They also support previous reports that, during summer days, volatilization of Hg0 from water represent an important step in the Hg cycle in freshwater systems. PMID:15823331

  10. Hg localisation in Tillandsia usneoides L. (Bromeliaceae), an atmospheric biomonitor

    NASA Astrophysics Data System (ADS)

    Amado Filho, G. M.; Andrade, L. R.; Farina, M.; Malm, O.

    The Spanish moss, Tillandsia usneoides, has been applied as an atmospheric biomonitor of Hg contamination, although the mechanism of metal plant accumulation has not been understood until now. In the present work, analytical scanning electron microscopy (SEM) was used to localize Hg in T. usneoides exposed to a Hg-air-contaminated area during 15 days. After this period, Hg was determined by the flow injection mercury system, and plants were prepared for SEM observation and energy-dispersive X-ray analysis. A concentration of 2702±318 μg Hg g -1 was determined in exposed plants. The presented microanalytical results demonstrated that Hg was partly associated with atmospheric particles deposited upon the plant surface, but it was highly absorbed by the scales, stem and leaves surfaces and less absorbed by epidermal cells of T. usneoides. No Hg was detected in mesophyll parenchyma or in vascular system cells. The great surface adsorption area provided by the scales, in addition to the characteristics of T. usneoides morphology, especially of the node region, are suggested to confer the great capability of T. usneoides in Hg holding.

  11. 40 CFR Appendix A to Subpart Uuuuu... - Hg Monitoring Provisions

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... sample gas, and any equipment needed to heat the probe or sample line to avoid condensation prior to the...-Based Emission Limits. For a heat input-based Hg emission limit (i.e., in lb/TBtu), data from a... appropriate units of the emission standard. 6.2.1Heat Input-Based Hg Emission Rates. Calculate hourly...

  12. 40 CFR 60.45Da - Standard for mercury (Hg).

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... to the provisions of this subpart shall cause to be discharged into the atmosphere from any affected... must not discharge into the atmosphere any gases from a new affected source that contain Hg in excess... discharge into the atmosphere any gases from a new affected source that contain Hg in excess of 66 × 10−...

  13. 40 CFR Appendix A to Subpart Uuuuu... - Hg Monitoring Provisions

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... concentrations of elemental Hg, which have been prepared according to the “EPA Traceability Protocol for Assay... Traceability Protocol for Qualification and Certification of Elemental Mercury Gas Generators” or an interim version of that protocol. 3.1.5NIST-Traceable Source of Oxidized Hg means a generator that is capable...

  14. 46 CFR 53.01-5 - Scope (modifies HG-100).

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 2 2010-10-01 2010-10-01 false Scope (modifies HG-100). 53.01-5 Section 53.01-5... IV of the ASME Boiler and Pressure Vessel Code (incorporated by reference; see 46 CFR 53.01-1). Table... General Requirements § 53.01-5 Scope (modifies HG-100). (a) The regulations in this part apply to...

  15. Linking mercury, carbon, and nitrogen stable isotopes in Tibetan biota: Implications for using mercury stable isotopes as source tracers

    NASA Astrophysics Data System (ADS)

    Xu, Xiaoyu; Zhang, Qianggong; Wang, Wen-Xiong

    2016-05-01

    Tibetan Plateau is located at a mountain region isolated from direct anthropogenic sources. Mercury concentrations and stable isotopes of carbon, nitrogen, and mercury were analyzed in sediment and biota for Nam Co and Yamdrok Lake. Biotic mercury concentrations and high food web magnification factors suggested that Tibetan Plateau is no longer a pristine site. The primary source of methylmercury was microbial production in local sediment despite the lack of direct methylmercury input. Strong ultraviolet intensity led to extensive photochemical reactions and up to 65% of methylmercury in water was photo-demethylated before entering the food webs. Biota displayed very high Δ199Hg signatures, with some highest value (8.6%) ever in living organisms. The δ202Hg and Δ199Hg in sediment and biotic samples increased with trophic positions (δ15N) and %methylmercury. Fish total length closely correlated to δ13C and Δ199Hg values due to dissimilar carbon sources and methylmercury pools in different living waters. This is the first mercury isotope study on high altitude lake ecosystems that demonstrated specific isotope fractionations of mercury under extreme environmental conditions.

  16. Linking mercury, carbon, and nitrogen stable isotopes in Tibetan biota: Implications for using mercury stable isotopes as source tracers.

    PubMed

    Xu, Xiaoyu; Zhang, Qianggong; Wang, Wen-Xiong

    2016-01-01

    Tibetan Plateau is located at a mountain region isolated from direct anthropogenic sources. Mercury concentrations and stable isotopes of carbon, nitrogen, and mercury were analyzed in sediment and biota for Nam Co and Yamdrok Lake. Biotic mercury concentrations and high food web magnification factors suggested that Tibetan Plateau is no longer a pristine site. The primary source of methylmercury was microbial production in local sediment despite the lack of direct methylmercury input. Strong ultraviolet intensity led to extensive photochemical reactions and up to 65% of methylmercury in water was photo-demethylated before entering the food webs. Biota displayed very high Δ(199)Hg signatures, with some highest value (8.6%) ever in living organisms. The δ(202)Hg and Δ(199)Hg in sediment and biotic samples increased with trophic positions (δ(15)N) and %methylmercury. Fish total length closely correlated to δ(13)C and Δ(199)Hg values due to dissimilar carbon sources and methylmercury pools in different living waters. This is the first mercury isotope study on high altitude lake ecosystems that demonstrated specific isotope fractionations of mercury under extreme environmental conditions. PMID:27151563

  17. Linking mercury, carbon, and nitrogen stable isotopes in Tibetan biota: Implications for using mercury stable isotopes as source tracers

    PubMed Central

    Xu, Xiaoyu; Zhang, Qianggong; Wang, Wen-Xiong

    2016-01-01

    Tibetan Plateau is located at a mountain region isolated from direct anthropogenic sources. Mercury concentrations and stable isotopes of carbon, nitrogen, and mercury were analyzed in sediment and biota for Nam Co and Yamdrok Lake. Biotic mercury concentrations and high food web magnification factors suggested that Tibetan Plateau is no longer a pristine site. The primary source of methylmercury was microbial production in local sediment despite the lack of direct methylmercury input. Strong ultraviolet intensity led to extensive photochemical reactions and up to 65% of methylmercury in water was photo-demethylated before entering the food webs. Biota displayed very high Δ199Hg signatures, with some highest value (8.6%) ever in living organisms. The δ202Hg and Δ199Hg in sediment and biotic samples increased with trophic positions (δ15N) and %methylmercury. Fish total length closely correlated to δ13C and Δ199Hg values due to dissimilar carbon sources and methylmercury pools in different living waters. This is the first mercury isotope study on high altitude lake ecosystems that demonstrated specific isotope fractionations of mercury under extreme environmental conditions. PMID:27151563

  18. Synthesis and crystal structures of HgFAsF6, Hg(HF)2(AsF6)2, Hg(HF)(AsF6)2 and Hg(AsF6)(SO3F)

    NASA Astrophysics Data System (ADS)

    Mazej, Zoran; Goreshnik, Evgeny A.

    2015-08-01

    The colourless HgFAsF6 was synthesized by oxidation of Hg2(AsF6)2 with elemental fluorine in anhydrous hydrogen fluoride. It crystallizes in the monoclinic space group P21/c with a=7.0645(3) Å, b=9.9023(3) Å, c=7.8686(3) Å, β=102.960(4)° V=536.43(3) Å3, and Z=4 at 150 K. The structure of HgFAsF6 consists of infinite zig-zag -[Hg-F-Hg]- chains oriented parallel to each other along the b axis and interconected by AsF6 groups. Hg(HF)2(AsF6)2 crystallizes in the triclinic space group P 1 bar with a=5.0781(3) Å, b=6.6907(5) Å, c=7.7135(5) Å, α=84.045(5), β=79.277(5)°, γ=80.612(6), V=253.32(3) Å3, and Z=1 at 150 K. The crystal structure is composed of infinite columns of Hg atoms linked by AsF6 groups. Each pair of adjacent Hg atoms is bridged by two AsF6 groups. The coordination of Hg is completed by two F atoms provided by HF molecules. Hg(HF)(AsF6)2 crystallizes in the monoclinic space group P21/c with a=9.4921(8) Å, b=9.2834(6) Å, c=10.5448(7) Å, β=103.795(7)°, V=902.53(12) Å3, and Z=4 at 150 K and it is isotypic to Cd(HF)(AsF6)2. The new mixed-anion compound Hg(AsF6)(SO3F) crystallizes in the monoclinic space group P21/c with a=5.1975(8) Å, b=18.046(3) Å, c=15.873(5) Å, β=93.614(13)°, V=1485.9(6) Å3, and Z=4 at 200 K. All three oxygen atoms from each SO3F group utilize for bonding with three Hg atoms. The Hg1 (Hg2) atoms are coordinated by two (four) oxygen atoms from two (four) SO3F groups and by six (three) fluorine atoms from AsF6 groups forming on that way tridimensional framework.

  19. Long-distance transport of Hg, Sb, and As from a mined area, conversion of Hg to methyl-Hg, and uptake of Hg by fish on the Tiber River basin, west-central Italy

    USGS Publications Warehouse

    Gray, John E.; Rimondi, Valentina; Costagliola, Pilario; Vaselli, Orlando; Lattanzi, Pierfranco

    2014-01-01

    Stream sediment, stream water, and fish were collected from a broad region to evaluate downstream transport and dispersion of mercury (Hg) from inactive mines in the Monte Amiata Hg District (MAMD), Tuscany, Italy. Stream sediment samples ranged in Hg concentration from 20 to 1,900 ng/g, and only 5 of the 17 collected samples exceeded the probable effect concentration for Hg of 1,060 ng/g, above which harmful effects are likely to be observed in sediment-dwelling organisms. Concentrations of methyl-Hg in Tiber River sediment varied from 0.12 to 0.52 ng/g, and although there is no established guideline for sediment methyl-Hg, these concentrations exceeded methyl-Hg in a regional baseline site (<0.02 ng/g). Concentrations of Hg in stream water varied from 1.2 to 320 ng/L, all of which were below the 1,000 ng/L Italian drinking water Hg guideline and the 770 ng/L U.S. Environmental Protection Agency (USEPA) guideline recommended to protect against chronic effects to aquatic wildlife. Methyl-Hg concentrations in stream water varied from <0.02 to 0.53 ng/L and were generally elevated compared to the baseline site (<0.02 ng/L). All stream water samples contained concentrations of As (<1.0–6.2 μg/L) and Sb (<0.20–0.37 μg/L) below international drinking water guidelines to protect human health (10 μg/L for As and 20 μg/L for Sb) and for protection against chronic effects to aquatic wildlife (150 μg/L for As and 5.6 μg/L for Sb). Concentrations of Hg in freshwater fish muscle ranged from 0.052–0.56 μg/g (wet weight), mean of 0.17 μg/g, but only 17 % (9 of 54) exceeded the 0.30 μg/g (wet weight) USEPA fish muscle guideline recommended to protect human health. Concentrations of Hg in freshwater fish in this region generally decreased with increasing distance from the MAMD, where fish with the highest Hg concentrations were collected more proximal to the MAMD, whereas all fish collected most distal from Hg mines contained Hg below the 0.30 μg/g fish muscle

  20. Isotopic compositions of bismuth, lead, thallium, and mercury from mini r-processing

    NASA Technical Reports Server (NTRS)

    Heymann, D.; Liffman, K.

    1986-01-01

    The yields of stable isotopes of Bi, Pb, Tl and Hg as well as yields of Pb-205 are calculated with a parametrized model for 'mini r-processing' in the Ne, O, C-rich zones of explosive burning in massive stars. The Pb isotopic compositions stand out by their comparatively low Pb-207 yields and by the fact that this r-process variant yields Pb-204 quite abundantly. The average Pb-205/Pb-204 yield ratio of 6.1 is the same order of magnitude as yield ratios deduced for s-processing. The Hg from this mini r-process looks like normal solar-system mercury, but with Hg-196 missing and the light s-isotopes A = 198, 199, 200 and 201 depleted (especially the odd-A species).

  1. Isotopic composition of inorganic mercury and methylmercury downstream of a historical gold mining region

    USGS Publications Warehouse

    Donovan, Patrick M.; Blum, Joel D.; Singer, Michael B.; Marvin-DiPasquale, Mark C.; Tsui, Martin T.K.

    2016-01-01

    We measured total mercury (THg) and monomethyl mercury (MMHg) concentrations and mercury (Hg) isotopic compositions in sediment and aquatic organisms from the Yuba River (California, USA) to identify Hg sources and biogeochemical transformations downstream of a historical gold mining region. Sediment THg concentrations and δ202Hg decreased from the upper Yuba Fan to the lower Yuba Fan and the Feather River. These results are consistent with the release of Hg during gold mining followed by downstream mixing and dilution. The Hg isotopic composition of Yuba Fan sediment (δ202Hg = −0.38 ± 0.17‰ and Δ199Hg = 0.04 ± 0.03‰; mean ± 1 SD, n = 7) provides a fingerprint of inorganic Hg (IHg) that could be methylated locally or after transport downstream. The isotopic composition of MMHg in the Yuba River food web was estimated using biota with a range of %MMHg (the percent of THg present as MMHg) and compared to IHg in sediment, algae, and the food web. The estimated δ202Hg of MMHg prior to photodegradation (−1.29 to −1.07‰) was lower than that of IHg and we suggest this is due to mass-dependent fractionation (MDF) of up to −0.9‰ between IHg and MMHg. This result is in contrast to net positive MDF (+0.4 to +0.8‰) previously observed in lakes, estuaries, coastal oceans, and forests. We hypothesize that this unique relationship could be due to differences in the extent or pathway of biotic MMHg degradation in stream environments.

  2. Isotopic Composition of Inorganic Mercury and Methylmercury Downstream of a Historical Gold Mining Region.

    PubMed

    Donovan, Patrick M; Blum, Joel D; Singer, Michael Bliss; Marvin-DiPasquale, Mark; Tsui, Martin T K

    2016-02-16

    We measured total mercury (THg) and monomethyl mercury (MMHg) concentrations and mercury (Hg) isotopic compositions in sediment and aquatic organisms from the Yuba River (California, USA) to identify Hg sources and biogeochemical transformations downstream of a historical gold mining region. Sediment THg concentrations and δ(202)Hg decreased from the upper Yuba Fan to the lower Yuba Fan and the Feather River. These results are consistent with the release of Hg during gold mining followed by downstream mixing and dilution. The Hg isotopic composition of Yuba Fan sediment (δ(202)Hg = -0.38 ± 0.17‰ and Δ(199)Hg = 0.04 ± 0.03‰; mean ± 1 SD, n = 7) provides a fingerprint of inorganic Hg (IHg) that could be methylated locally or after transport downstream. The isotopic composition of MMHg in the Yuba River food web was estimated using biota with a range of %MMHg (the percent of THg present as MMHg) and compared to IHg in sediment, algae, and the food web. The estimated δ(202)Hg of MMHg prior to photodegradation (-1.29 to -1.07‰) was lower than that of IHg and we suggest this is due to mass-dependent fractionation (MDF) of up to -0.9‰ between IHg and MMHg. This result is in contrast to net positive MDF (+0.4 to +0.8‰) previously observed in lakes, estuaries, coastal oceans, and forests. We hypothesize that this unique relationship could be due to differences in the extent or pathway of biotic MMHg degradation in stream environments. PMID:26789018

  3. Characterization of CdTe, HgTe, and Hg1-xCdxTe grown by chemical beam epitaxy

    NASA Astrophysics Data System (ADS)

    Wagner, B. K.; Rajavel, D.; Benz, R. G.; Summers, C. J.

    1991-10-01

    Detailed characterization of chemical beam epitaxially (CBE) grown CdTe and Hg1-xCdxTe layers are reported. These characterizations include photoluminescence, infrared transmission, energy dispersive x-ray analysis, and variable temperature (10-300 K) Hall effect and resistivity measurements. The results indicate that high quality HgCdTe layers can be grown by CBE.

  4. Reduced leakage currents of CdZnTe radiation detectors with HgTe/HgCdTe superlattice contacts

    NASA Astrophysics Data System (ADS)

    Chang, Y.; Grein, C. H.; Becker, C. R.; Huang, J.; Ghosh, S.; Aqariden, F.; Sivananthan, S.

    2012-10-01

    Room-temperature-operating CdZnTe radiation detectors have high energy resolution, linear energy response and are capable of operating in normal counting and spectroscopic modes, hence are highly desirable for medical diagnosis, nondestructive industrial evaluations, homeland security, counterterrorism inspections and nuclear proliferation detection to ensure national and international nuclear safety. HgTe/HgCdTe superlattices can be designed to selectively transport one carrier species while hindering transport of the other. Specifically, one designs a large carrier effective mass for undesired carriers in the electric field direction, which results in low carrier velocities, and yet a density of states for undesired carrier that is lower than that of a comparable bulk semiconductor, which results in low carrier concentrations, hence a low current density under an electric field. The opposite carrier species can be designed to have a large velocity and high density of states, hence producing a large current density. By employing HgTe/HgCdTe superlattices as contact layers intermediate between CdZnTe absorbers and metal contacts, leakage currents under high electric fields are reduced and improved x-ray and γ-ray detector performance is anticipated. Pixilated CdZnTe radiation detectors arrays were fabricated and characterized to evaluate the effectiveness of HgTe/HgCdTe superlattices in reducing leakage currents. Current-voltage characteristics show that HgTe/HgCdTe superlattice contact layers consistently result in significantly reduced leakage currents relative to detectors with only metal contacts.

  5. Mass dependent stable isotope fractionation of mercury during mer mediated microbial degradation of monomethylmercury

    NASA Astrophysics Data System (ADS)

    Kritee, K.; Barkay, Tamar; Blum, Joel D.

    2009-03-01

    Controlling bioaccumulation of toxic monomethylmercury (MMHg) in aquatic food chains requires differentiation between biotic and abiotic pathways that lead to its production and degradation. Recent mercury (Hg) stable isotope measurements of natural samples suggest that Hg isotope ratios can be a powerful proxy for tracing dominant Hg transforming pathways in aquatic ecosystems. Specifically, it has been shown that photo-degradation of MMHg causes both mass dependent (MDF) and mass independent fractionation (MIF) of Hg isotopes. Because the extent of MDF and MIF observed in natural samples (e.g., fish, soil and sediments) can potentially be used to determine the relative importance of pathways leading to MMHg accumulation, it is important to determine the potential role of microbial pathways in contributing to the fractionation, especially MIF, observed in these samples. This study reports the extent of fractionation of Hg stable isotopes during degradation of MMHg to volatile elemental Hg and methane via the microbial Hg resistance ( mer) pathway in Escherichia coli carrying a mercury resistance ( mer) genetic system on a multi-copy plasmid. During experimental microbial degradation of MMHg, MMHg remaining in reactors became progressively heavier (increasing δ202Hg) with time and underwent mass dependent Rayleigh fractionation with a fractionation factor α202/198 = 1.0004 ± 0.0002 (2SD). However, MIF was not observed in any of the microbial MMHg degradation experiments indicating that the isotopic signature left by mer mediated MMHg degradation is significantly different from fractionation observed during DOC mediated photo-degradation of MMHg. Additionally, a clear suppression of Hg isotope fractionation, both during reduction of Hg(II) and degradation of MMHg, was observed when the cell densities increased, possibly due to a reduction in substrate bioavailability. We propose a multi-step framework for understanding the extent of fractionation seen in our MMHg

  6. The influence of intruder states in even-even Po isotopes

    SciTech Connect

    García-Ramos, J. E.; Heyde, K.

    2015-10-15

    We study the role of intruder states and shape coexistence in the even-even {sup 190–206}Po isotopes, through an interacting boson model with configuration mixing calculation. We analyzed the results in the light of known systematics on various observable in the Pb region, paying special attention to the unperturbed energy systematics and quadrupole deformation. We find that shape coexistence in the Po isotopes behaves in very much the same way as in the Pt isotopes, i.e., it is somehow hidden, contrary to the situation in the Pb and the Hg isotopes.

  7. Hg and Se Speciation in Liver Tissue of Marine Birds

    NASA Astrophysics Data System (ADS)

    Karanfil, Cahit; Bischoff, Karyn; Bunker, Grant

    2013-04-01

    X-ray fluorescence microprobe maps of Hg and Se distribution were made on liver tissue slices from marine birds (Cormorants) from Florida's Everglades. The birds bio-concentrate these toxic pollutants that are ingested from their diet of fish. The fluorescence maps show strong localization of Mercury and Selenium into "hot spots" less than 100 microns in size. XAFS measurements were made on hot spots to demonstrate that the Hg and Se are indeed are chemically bound, supporting the idea that moderate levels of Se may have a protective effect against Hg through its complexation.

  8. High speed, high performance /Hg,Cd/Te photodiode detectors.

    NASA Technical Reports Server (NTRS)

    Soderman, D. A.; Pinkston, W. H.

    1972-01-01

    The current performance of high speed photodiode detectors for the 1 to 10 micron spectral region is discussed. The (Hg,Cd)Te photodiode configuration, detector properties, integration in laser receiver modules, and frequency response are considered for near infrared and far infrared wavelengths. The recent advances in (Hg,Cd)Te material and device development are indicated by the realization not only of exceptionally high speed detectors but of detectors that exhibit excellent detectivities. The performance improves substantially when the detector is cooled. This detector junction technology has been extended to other compositions of (Hg,Cd)Te for peak spectral responses at 5 and 10 micron.

  9. High-lying bound Rydberg states of excited Hg(6s6p {sup 3}P{sub 1}) atoms from two-color resonance ionization mass spectroscopy

    SciTech Connect

    Bisling, Peter; Dederichs, Jan; Neidhart, Bernd; Weitkamp, Claus

    1998-12-16

    Mercury isotopes are investigated with two-color resonance ionization mass spectroscopy (RIMS). Isotope shifts, hyperfine structure splittings, and the lifetime of the intermediate 6s6p {sup 3}P{sub 1} state are determined by RIMS. Ion yields at the threshold region in various static electric fields are measured in order to determine an extrapolated ionization energy value at zero field strength. New energy values for high-lying bound 6s nd {sup 3}D (21Hg isotopes are found under field-free conditions and with delayed, pulsed electric field ionization. To the author's knowledge this is the first time that isotopic effects on the ionization energy are deduced from the convergence limit of the Rydberg series.

  10. Apparatus for isotopic alteration of mercury vapor

    DOEpatents

    Grossman, Mark W.; George, William A.; Marcucci, Rudolph V.

    1988-01-01

    An apparatus for enriching the isotopic Hg content of mercury is provided. The apparatus includes a reactor, a low pressure electric discharge lamp containing a fill including mercury and an inert gas. A filter is arranged concentrically around the lamp. In a preferred embodiment, constant mercury pressure is maintained in the filter by means of a water-cooled tube that depends from it, the tube having a drop of mercury disposed in it. The reactor is arranged around the filter, whereby radiation from said lamp passes through the filter and into said reactor. The lamp, the filter and the reactor are formed of a material which is transparent to ultraviolet light.

  11. Trace elements (Cu, Zn, and Hg) and δ(13)C/δ(15)N in seabird subfossils from three islands of the South China Sea and its implications.

    PubMed

    Xu, Liqiang; Liu, Xiaodong; Nie, Yaguang

    2016-05-01

    Seabird subfossils were collected on three islands of the Xisha Archipelago, South China Sea. Via elemental analysis, we identified that bird guano was a significant source for heavy metals Cu, Zn, and Hg. Cu and Zn levels in these guano samples are comparable to their levels in wildbird feces, but guano Hg was lower than previously reported. Trophic positions significantly impacted transfer efficiency of heavy metals by seabirds. Despite of a common source, trace elements, as well as stable isotopes (i.e., guano δ(13)C and collagen δ(15)N), showed island-specific characteristics. Bird subfossils on larger island had relatively greater metal concentrations and revealed higher trophic positions. Partition of element and isotope levels among the islands suggested that transfer efficacy of seabirds on different islands was different, and bird species were probably unevenly distributed among the islets. Island area is possibly a driving factor for distributions of seabird species. PMID:27056479

  12. New μs isomers in the neutron-rich 210Hg nucleus

    NASA Astrophysics Data System (ADS)

    Gottardo, A.; Valiente-Dobón, J. J.; Benzoni, G.; Gadea, A.; Lunardi, S.; Boutachkov, P.; Bruce, A. M.; Górska, M.; Grebosz, J.; Pietri, S.; Podolyák, Zs.; Pfützner, M.; Regan, P. H.; Weick, H.; Alcántara Núñez, J.; Algora, A.; Al-Dahan, N.; de Angelis, G.; Ayyad, Y.; Alkhomashi, N.; Allegro, P. R. P.; Bazzacco, D.; Benlliure, J.; Bowry, M.; Bracco, A.; Bunce, M.; Camera, F.; Casarejos, E.; Cortes, M. L.; Crespi, F. C. L.; Corsi, A.; Denis Bacelar, A. M.; Deo, A. Y.; Domingo-Pardo, C.; Doncel, M.; Dombradi, Zs.; Engert, T.; Eppinger, K.; Farrelly, G. F.; Farinon, F.; Farnea, E.; Geissel, H.; Gerl, J.; Goel, N.; Gregor, E.; Habermann, T.; Hoischen, R.; Janik, R.; John, P. R.; Klupp, S.; Kojouharov, I.; Kurz, N.; Lenzi, S. M.; Leoni, S.; Mandal, S.; Menegazzo, R.; Mengoni, D.; Million, B.; Modamio, V.; Morales, A. I.; Napoli, D. R.; Naqvi, F.; Nicolini, R.; Nociforo, C.; Prochazka, A.; Prokopowicz, W.; Recchia, F.; Ribas, R. V.; Reed, M. W.; Rudolph, D.; Sahin, E.; Schaffner, H.; Sharma, A.; Sitar, B.; Siwal, D.; Steiger, K.; Strmen, P.; Swan, T. P. D.; Szarka, I.; Ur, C. A.; Walker, P. M.; Wieland, O.; Wollersheim, H.-J.

    2013-10-01

    Neutron-rich nuclei in the lead region, beyond N = 126, have been studied at the FRS-RISING setup at GSI, exploiting the fragmentation of a primary uranium beam. Two isomeric states have been identified in 210Hg: the 8+ isomer expected from the seniority scheme in the νg9/2 shell and a second one at low spin and low excitation energy. The decay strength of the 8+ isomer confirms the need of effective three-body forces in the case of neutron-rich lead isotopes. The other unexpected low-lying isomer has been tentatively assigned as a 3- state, although this is in contrast with theoretical expectations.

  13. Using X-ray microscopy and Hg L3 XANES to study Hg binding in the rhizosphere of Spartina cordgrass.

    PubMed

    Patty, Cynthia; Barnett, Brandy; Mooney, Bridget; Kahn, Amanda; Levy, Silvio; Liu, Yijin; Pianetta, Piero; Andrews, Joy C

    2009-10-01

    San Francisco Bay has been contaminated historically by mercury from mine tailings as well as contemporary industrial sources. Native Spartina foliosa and non-native S. alterniflora-hybrid cordgrasses are dominant florae within the SF Bay estuary environment. Understanding mercury uptake and transformations in these plants will help to characterize the significance of their roles in mercury biogeochemical cycling in the estuarine environment. Methylated mercury can be biomagnified up the food web, resulting in levels in sport fish up to 1 million times greater than in surrounding waters and resulting in advisories to limit fish intake. Understanding the uptake and methylation of mercury in the plant rhizosphere can yield insight into ways to manage mercury contamination. The transmission X-ray microscope on beamline 6-2 at the Stanford Synchrotron Radiation Lightsource (SSRL) was used to obtain absorption contrast images and 3D tomography of Spartina foliosa roots that were exposed to 1 ppm Hg (as HgCl2) hydroponically for 1 week. Absorption contrast images of micrometer-sized roots from S. foliosa revealed dark particles, and dark channels within the root, due to Hg absorption. 3D tomography showed that the particles are on the root surface, and slices from the tomographic reconstruction revealed that the particles are hollow, consistent with microorganisms with a thin layer of Hg on the surface. Hg L3 XANES of ground-up plant roots and Hg L3 micro-XANES from microprobe analysis of micrometer-sized roots (60-120 microm in size) revealed three main types of speciation in both Spartina species: Hg-S ligation in a form similar to Hg(II) cysteine, Hg-S bonding as in cinnabar and metacinnabar, and methylmercury-carboxyl bonding in a form similar to methylmercury acetate. These results are interpreted within the context of obtaining a "snapshot" of mercury methylation in progress. PMID:19848152

  14. Persistent Hg contamination and occurrence of Hg-methylating transcript (hgcA) downstream of a chlor-alkali plant in the Olt River (Romania).

    PubMed

    Bravo, Andrea G; Loizeau, Jean-Luc; Dranguet, Perrine; Makri, Stamatina; Björn, Erik; Ungureanu, Viorel Gh; Slaveykova, Vera I; Cosio, Claudia

    2016-06-01

    Chlor-alkali plants using mercury (Hg) cell technology are acute point sources of Hg pollution in the aquatic environment. While there have been recent efforts to reduce the use of Hg cells, some of the emitted Hg can be transformed to neurotoxic methylmercury (MeHg). Here, we aimed (i) to study the dispersion of Hg in four reservoirs located downstream of a chlor-alkali plant along the Olt River (Romania) and (ii) to track the activity of bacterial functional genes involved in Hg methylation. Total Hg (THg) concentrations in water and sediments decreased successively from the initial reservoir to downstream reservoirs. Suspended fine size particles and seston appeared to be responsible for the transport of THg into downstream reservoirs, while macrophytes reflected the local bioavailability of Hg. The concentration and proportion of MeHg were correlated with THg, but were not correlated with bacterial activity in sediments, while the abundance of hgcA transcript correlated with organic matter and Cl(-) concentration, indicating the importance of Hg bioavailability in sediments for Hg methylation. Our data clearly highlights the importance of considering Hg contamination as a legacy pollutant since there is a high risk of continued Hg accumulation in food webs long after Hg-cell phase out. PMID:26662302

  15. Radioactivity in HgCdTe devices: potential source of "snowballs"

    NASA Astrophysics Data System (ADS)

    McCullough, P.

    2009-12-01

    We hypothesize that the "snowballs" observed in HgCdTe infrared detectors are caused by natural radioactivity in the devices themselves. As characterized by Hilbert (2009) in the WFC3 flight IR array (FPA165), "snowballs" are transient events that instantaneously saturate a few pixels and deposit a few hundred thousand electrons over a ~5-pixel (~100-um) diameter region. In 2008, prior to flight of detector FPA165, Hilbert (2009) detected 21 snowballs during thermal vaccum test three (TV3) and inferred a rate of ~1100 ± 200 snowballs per year per cm2 of the HgCdTe detector. Alpha particles emitted from either (or both) naturally radioactive thorium and/or uranium, at ~1 ppm concentrations within the device, can explain the observed characteristics of the "snowballs." If thorium is present, up to four distinctly observable snowballs should appear at the same location on the pixel array over the course of many years. While the indium in the bump bonds is almost entirely the radioactive isotope In-115, and 12% of the cadmium is naturally radioactive Cd-113, both of those emit only betas, which are too penetrating and not energetic enough to match the observed characteristics of "snowballs." Also, the Cd-113 emission rate is much less than that of the observed snowballs.

  16. Transient and diffusion analysis of HgCdTe

    NASA Technical Reports Server (NTRS)

    Clayton, J. C.

    1982-01-01

    Solute redistribution during directional solidification of HgCdTe is addressed. Both one-dimensional and two-dimensional models for solute redistribution are treated and model results compared to experiment. The central problem studied is the cause of radial inhomogeneities found in directionally solidified HgCdTe. A large scale gravity-driven interface instability, termed shape instability, is postulated to be the cause of radial inhomogeneities. Recommendations for future work, along with appropriate computer programs, are included.

  17. Mercury stable isotope fractionation in a tropical ecosystem including human hair: New insights for an isotope balance

    NASA Astrophysics Data System (ADS)

    Laffont, Laure; Sonke, Jeroen; Maurice, Laurence; Behra, Philippe

    2010-05-01

    Mercury contamination is an environmental problem in the Amazon basin still relevant today as impacts on human health are poorly studied. In Bolivia, indigenous people have elevated methylmercury concentrations (between 2719 and 23701 ng.g-1) in their hair. This highly toxic molecule is formed after methylation of inorganic Hg released by chemical and physical weathering and from human activities. The aim of our study is to propose a first isotope balance in a Bolivian Amazon ecosystem, through variations in Hg isotopic compositions. The discovery of mass-independent fracionation (MIF) of odd-isotopes in our organic samples (fish and human hair) opened a new way of research in tracing the sources and the processes involved in the cycle of Hg. Four types of samples are studied: liquid Hg0 from gold mining, sediment samples, fish coming from the Beni River basin (from the main channel and an associated floodplain lake) and hair from gold miners and fish-eating native populations. Hg isotopic compositions were analyzed on a Thermo-Finnigan Neptune MC-ICP-MS at the LMTG after sample digestion by HCl/HNO3 or by H2O2/HNO3 for fish samples, at 120°C. The δ202Hg values (relative to NIST 3133) are signicantly different with respect to the external precision on UM-Almaden#2 of 0.18 ‰ (2σ, n = 42): -0.34 ± 0.02 ‰ for liquid mercury, between -1.33 and -0.81 ‰ for bottom and floodplain sediments (n=18), between -0.87 and 2.22 ‰ for miners hair (n=26), +1.29 ± 0.41 ‰ for native hair (n=13) and between -0.91 and -0.21 ‰ for fish samples (n=53). A large mass-independent isotope fractionation (MIF) was observed for odd isotope ratios in all hair samples and fish samples whereas weak anomalies were measured for sediment samples: - ∆199Hg anomaly: -0.12 to -0.04 ‰ for sediment, -0.22 to +0.63 ‰ for fish samples and +0.13 to +1.63 ‰ for hair - ∆201Hg anomaly: -0.12 to -0.02 ‰ for sediment, -0.21 to +0.43 ‰ for fish samples and +0.06 to +1.25 ‰ for hair

  18. Magnetotransport in double quantum well with inverted energy spectrum: HgTe/CdHgTe

    NASA Astrophysics Data System (ADS)

    Yakunin, M. V.; Suslov, A. V.; Popov, M. R.; Novik, E. G.; Dvoretsky, S. A.; Mikhailov, N. N.

    2016-02-01

    We present an experimental study of the double-quantum-well (DQW) system made of two-dimensional layers with inverted energy band spectrum: HgTe. The magnetotransport reveals a considerably larger overlap of the conduction and valence subbands than in known HgTe single quantum wells (QW), which may be regulated here by an applied gate voltage Vg. This large overlap manifests itself in a much higher critical field Bc separating the range above it with a plain behavior of the Hall magnetoresistance ρx y(B ) , where the quantum peculiarities shift linearly with Vg, and the range below with a complicated behavior. In the latter case, specific structures in ρx y(B ) are formed like a double-N -shaped ρx y(B ) , reentrant sign-alternating quantum Hall effect with transitions into a zero-filling-factor state, etc., which are clearly manifested here due to better magnetic quantization at high fields, as compared to the features seen earlier in a single HgTe QW. The coexisting electrons and holes were found in the whole investigated range of positive and negative Vg as revealed (i) from fits to the low-field N -shaped ρx y(B ) , (ii) from the Fourier analysis of oscillations in ρx x(B ) , and (iii) from a specific behavior of ρx y(B ) at high positive Vg. A peculiar feature here is that the found electron density n remains almost constant in the whole range of investigated Vg while the hole density p drops down from the value a factor of 6 larger than n at extreme negative Vg to almost zero at extreme positive Vg passing through the charge-neutrality point. We show that this difference between n and p stems from an order of magnitude larger density of states for holes in the lateral valence subband maxima than for electrons in the conduction subband minimum. We analyze our observations on the basis of a calculated picture of magnetic levels in a DQW and suggest that their specificity is due to (i) a nonmonotonic course of the valence subband magnetic levels and an

  19. Anaerobic oxidation of Hg(0) and methylmercury formation by Desulfovibrio desulfuricans ND132

    NASA Astrophysics Data System (ADS)

    Colombo, Matthew J.; Ha, Juyoung; Reinfelder, John R.; Barkay, Tamar; Yee, Nathan

    2013-07-01

    The transformation of inorganic mercury (Hg) to methylmercury (MeHg) plays a key role in determining the amount of Hg that is bioaccumulated in aquatic food chains. An accurate knowledge of Hg methylation mechanisms is required to predict the conditions that promote MeHg production in aquatic environments. In this study, we conducted experiments to examine the oxidation and methylation of dissolved elemental mercury [Hg(0)] by the anaerobic bacterium Desulfovibrio desulfuricans ND132. Anoxic cultures of D. desulfuricans ND132 were exposed to Hg(0) in the dark, and samples were collected and analyzed for the loss of Hg(0), formation of non-purgeable Hg, and formation of MeHg over time. We found that D. desulfuricans ND132 rapidly transformed dissolved gaseous mercury into non-purgeable Hg, with bacterial cultures producing approximately 40 μg/L of non-purgeable Hg within 30 min, and as much as 800 μg/L of non-purgeable Hg after 36 h. Derivatization of the non-purgeable Hg in the cell suspensions to diethylmercury and analysis of Hg(0)-reacted D. desulfuricans ND132 cells using X-ray absorption near edge structure (XANES) spectroscopy demonstrated that cell-associated Hg was dominantly in the oxidized Hg(II) form. Spectral comparisons and linear combination fitting of the XANES spectra indicated that the oxidized Hg(II) was covalently bonded to cellular thiol functional groups. MeHg analyses revealed that D. desulfuricans ND132 produced up to 118 μg/L of methylmercury after 36 h of incubation. We found that a significant fraction of the methylated Hg was exported out of the cell and released into the culture medium. The results of this work demonstrate a previously unrecognized pathway in the mercury cycle, whereby anaerobic bacteria produce MeHg when provided with dissolved Hg(0) as their sole Hg source.

  20. Understanding associations between nitrogen and carbon isotopes and mercury in three Ammodramus sparrows.

    PubMed

    Winder, Virginia L; Michaelis, Adriane K; Emslie, Steven D

    2012-03-01

    We analyzed nitrogen and carbon stable isotope ratios and mercury (Hg) in breast feathers from three species of closely related sparrows, Saltmarsh, Seaside, and Nelson's Sparrows (Ammodramus caudacutus, A. maritimus, and A. nelsoni, respectively), to assess if trophic position and food web structure influence Hg exposure in these species. Sparrows were captured during the non-breeding season from 2006 to 2008 in North Carolina salt marshes near Wrightsville Beach, New Hanover County. Generalized linear models were used to test for the influence of species, δ(15)N, and δ(13)C on breast feather Hg. The most parsimonious model included species, δ(15)N, and their interaction term and explained 36% of the variation in breast feather Hg. Each species exhibited a different association between breast feather δ(15)N and Hg with Seaside Sparrows showing a positive correlation (r=0.27, P=0.03), Nelson's Sparrows a negative correlation (r=-0.28, P=0.01), and Saltmarsh Sparrows with no significant association. For Saltmarsh Sparrows, δ(15)N and Hg revealed decoupling between breast feather Hg and trophic position. Our results demonstrate that the influence of δ(15)N on breast feather Hg is likely indicative of geographic variation in δ(15)N baselines rather than trophic position. PMID:22285218

  1. Beer Law Constants and Vapor Pressures of HgI2 over HgI2(s,l)

    NASA Technical Reports Server (NTRS)

    Su, Ching-Hua; Zhu, Shen; Ramachandran, N.; Burger, A.; Whitaker, Ann F. (Technical Monitor)

    2001-01-01

    The optical absorption spectra of the vapor phase over HgI2(s,l) were measured for wavelengths between 200 and 600 nm. The spectra show that the sample sublimed congruently into HgI2 with no Hg or I2 absorption spectrum observed. The Beer's Law constants for 15 wavelengths between 200 and 440 nm were determined. From these constants the vapor pressure of H912, P, was established as a function of temperatures for the liquid and the solid Beta-phases. The expressions correspond to the enthalpies of vaporization and sublimation of 15.30 and 20.17 Kcal/mole, respectively, for the liquid and the Beta-phase HgI2. The difference in the enthalpies gives an enthalpy of fusion of 4.87 Kcal/mole and the intersection of the two expressions gives a melting point of 537 K.

  2. Isotope geochemistry of mercury in source rocks, mineral deposits and spring deposits of the California Coast Ranges, USA

    USGS Publications Warehouse

    Smith, C.N.; Kesler, S.E.; Blum, J.D.; Rytuba, J.J.

    2008-01-01

    We present here the first study of the isotopic composition of mercury in rocks, ore deposits, and active spring deposits from the California Coast Ranges, a part of Earth's crust with unusually extensive evidence of mercury mobility and enrichment. The Franciscan Complex and Great Valley Sequence, which form the bedrock in the California Coast Ranges, are intruded and overlain by Tertiary volcanic rocks including the Clear Lake Volcanic Sequence. These rocks contain two types of mercury deposits, hot-spring deposits that form at shallow depths (< 300??m) and silica-carbonate deposits that extend to depths of 1000??m. Active springs and geothermal areas continue to precipitate Hg and Au and are modern analogues to the fossil hydrothermal systems preserved in the ore deposits. The Franciscan Complex and Great Valley Sequence contain clastic sedimentary rocks with higher concentrations of mercury than volcanic rocks of the Clear Lake Volcanic Field. Mean mercury isotopic compositions (??202Hg) for all three rock units are similar, although the range of values in Franciscan Complex rocks is greater than in either Great Valley or Clear Lake rocks. Hot spring and silica-carbonate mercury deposits have similar average mercury isotopic compositions that are indistinguishable from averages for the three rock units, although ??202Hg values for the mercury deposits have a greater variance than the country rocks. Precipitates from spring and geothermal waters in the area have similarly large variance and a mean ??202Hg value that is significantly lower than the ore deposits and rocks. These observations indicate that there is little or no isotopic fractionation (< ?? 0.5???) during release of mercury from its source rocks into hydrothermal solutions. Isotopic fractionation does appear to take place during transport and concentration of mercury in deposits, however, especially in their uppermost parts. Boiling of hydrothermal fluids, separation of a mercury-bearing CO2 vapor

  3. A ratiometric electrochemical biosensor for sensitive detection of Hg2+ based on thymine-Hg2+-thymine structure.

    PubMed

    Xiong, Erhu; Wu, Liang; Zhou, Jiawan; Yu, Peng; Zhang, Xiaohua; Chen, Jinhua

    2015-01-01

    In this paper, a simple, selective and reusable electrochemical biosensor for the sensitive detection of mercury ions (Hg(2+)) has been developed based on thymine (T)-rich stem-loop (hairpin) DNA probe and a dual-signaling electrochemical ratiometric strategy. The assay strategy includes both "signal-on" and "signal-off" elements. The thiolated methylene blue (MB)-modified T-rich hairpin DNA capture probe (MB-P) firstly self-assembled on the gold electrode surface via Au-S bond. In the presence of Hg(2+), the ferrocene (Fc)-labeled T-rich DNA probe (Fc-P) hybridized with MB-P via the Hg(2+)-mediated coordination of T-Hg(2+)-T base pairs. As a result, the hairpin MB-P was opened, the MB tags were away from the gold electrode surface and the Fc tags closed to the gold electrode surface. These conformation changes led to the decrease of the oxidation peak current of MB (IMB), accompanied with the increase of that of Fc (IFc). The logarithmic value of IFc/IMB is linear with the logarithm of Hg(2+) concentration in the range from 0.5 nM to 5000 nM, and the detection limit of 0.08 nM is much lower than 10nM (the US Environmental Protection Agency (EPA) limit of Hg(2+) in drinking water). What is more, the developed DNA-based electrochemical biosensor could be regenerated by adding cysteine and Mg(2+). This strategy provides a simple and rapid approach for the detection of Hg(2+), and has promising application in the detection of Hg(2+) in real environmental samples. PMID:25467465

  4. Determination of As, Hg and Pb in herbs using slurry sampling flow injection chemical vapor generation inductively coupled plasma mass spectrometry.

    PubMed

    Tai, Chia-Yi; Jiang, Shiuh-Jen; Sahayam, A C

    2016-02-01

    Analysis of herbs for As, Hg and Pb has been carried out using slurry sampling inductively coupled plasma mass spectrometry (ICP-MS) with flow injection vapor generation. Slurry containing 0.5% m/v herbal powder, 0.1% m/v citric acid and 2% v/v HCl was injected into the VG-ICP-MS system for the determination of As, Hg and Pb that obviate dissolution and mineralization. Standard addition and isotope dilution methods were used for quantifications in selected herbal powders. This method has been validated by the determination of As, Hg and Pb in NIST standard reference materials SRM 1547 Peach Leaves and SRM 1573a Tomato Leaves. The As, Hg and Pb analysis results of the reference materials agreed with the certified values. The precision obtained by the reported procedure was better than 7% for all determinations. The detection limit estimated from standard addition curve was 0.008, 0.003, and 0.007 ng mL(-1) for As, Hg and Pb, respectively. PMID:26304347

  5. Electronic properties of liquid Hg-In alloys : Ab-initio molecular dynamics study

    NASA Astrophysics Data System (ADS)

    Sharma, Nalini; Thakur, Anil; Ahluwalia, P. K.

    2016-05-01

    Ab-initio molecular dynamics simulations are performed to study the structural properties of liquid Hg-In alloys. The interatomic interactions are described by ab-initio pseudopotentials given by Troullier and Martins. Three liquid Hg-In alloys (Hg10In90, Hg30In70,. Hg50In50, Hg70In30, and Hg90Pb10) at 299 K are considered. The calculated results for liquid Hg (l-Hg) and lead (l-In) are also drawn. Along with the calculated results of considered five liquid alloys of Hg-In alloy. The results obtained from electronic properties namely total density of state and partial density of states help to find the local arrangement of Hg and In atoms and the presence of liquid state in the considered five alloys.

  6. Method for separating isotopes

    DOEpatents

    Jepson, B.E.

    1975-10-21

    Isotopes are separated by contacting a feed solution containing the isotopes with a cyclic polyether wherein a complex of one isotope is formed with the cyclic polyether, the cyclic polyether complex is extracted from the feed solution, and the isotope is thereafter separated from the cyclic polyether.

  7. Stable isotope studies

    SciTech Connect

    Ishida, T.

    1992-01-01

    The research has been in four general areas: (1) correlation of isotope effects with molecular forces and molecular structures, (2) correlation of zero-point energy and its isotope effects with molecular structure and molecular forces, (3) vapor pressure isotope effects, and (4) fractionation of stable isotopes. 73 refs, 38 figs, 29 tabs.

  8. Algebraic approach to the structure of the low-lying states in A ≈100 Ru isotopes

    NASA Astrophysics Data System (ADS)

    Kisyov, S.; Bucurescu, D.; Jolie, J.; Lalkovski, S.

    2016-04-01

    The structure of the low-lying states in the odd- and even-mass A ≈100 Ru isotopes is studied in the framework of two algebraic models. The even-mass Ru nuclei are first described within the interacting boson model 1 (IBM-1). The output of these calculations was then used to calculate the odd-A isotopes within the interacting boson-fermion model 1 (IBFM-1), where a coupling of the odd neutron to the even-even core is considered. The level energies and transition probabilities calculated in the present work are tested against the experimental data. One-nucleon transfer spectroscopic factors as well as electromagnetic moments were also calculated for the odd-A Ru and compared to the experimental values. The transitional character of the isotopes is studied. Most of the low-lying positive-parity states in the odd-A Ru nuclei below 2 MeV are interpreted on the basis of ν d5 /2 and ν g7 /2 configurations. The role of the ν s1 /2 orbital in the nuclear structure of the odd-mass Ru nuclei at low energies is also studied. The negative-parity states are interpreted as ν h11 /2 excitations coupled to the core. The evolution of the IBM-1 and IBFM-1 parameters is discussed.

  9. Low-lying dipole excitations in vibrational nuclei: The Cd isotopic chain studied in photon scattering experiments

    SciTech Connect

    Kohstall, C.; Belic, D.; Kneissl, U.; Nord, A.; Pitz, H.H.; Scheck, M.; Stedile, F.; Brentano, P. von; Fransen, C.; Gade, A.; Herzberg, R.-D.; Jolie, J.; Linnemann, A.; Pietralla, N.; Werner, V.; Yates, S.W.

    2005-09-01

    High-resolution nuclear resonance fluorescence experiments (NRF) were performed on {sup 110,111,112,114,116}Cd at the bremsstrahlung facility of the 4.3-MV Dynamitron accelerator in Stuttgart to study the low-lying dipole strength distributions in these vibrational nuclei. Numerous excited states, most of them previously unknown, were observed in the excitation energy range up to 4 MeV. Detailed spectroscopic information has been obtained on excitation energies, spins, decay widths, decay branchings, and transition probabilities. For states in the even-even isotopes {sup 110,112,114,116}Cd, parities could be assigned from linear polarization measurements. Together with our previous results for {sup 108,112,113,114}Cd from NRF studies without polarization measurements, systematics was established for the dipole strength distributions of the stable nuclei within the Cd isotopic chain. The results are discussed with respect to the systematics of E1 two-phonon excitations and mixed-symmetry states in even-even nuclei near the Z=50 shell closure and the fragmentation of these excitation modes in the odd-mass Cd isotopes.

  10. Two-dimensional topological insulators with tunable band gaps: Single-layer HgTe and HgSe

    PubMed Central

    Li, Jin; He, Chaoyu; Meng, Lijun; Xiao, Huaping; Tang, Chao; Wei, Xiaolin; Kim, Jinwoong; Kioussis, Nicholas; Malcolm Stocks, G.; Zhong, Jianxin

    2015-01-01

    Two-dimensional (2D) topological insulators (TIs) with large band gaps are of great importance for the future applications of quantum spin Hall (QSH) effect. Employing ab initio electronic calculations we propose a novel type of 2D topological insulators, the monolayer (ML) low-buckled (LB) mercury telluride (HgTe) and mercury selenide (HgSe), with tunable band gap. We demonstrate that LB HgTe (HgSe) monolayers undergo a trivial insulator to topological insulator transition under in-plane tensile strain of 2.6% (3.1%) due to the combination of the strain and the spin orbital coupling (SOC) effects. Furthermore, the band gaps can be tuned up to large values (0.2 eV for HgTe and 0.05 eV for HgSe) by tensile strain, which far exceed those of current experimentally realized 2D quantum spin Hall insulators. Our results suggest a new type of material suitable for practical applications of 2D TI at room-temperature. PMID:26365502

  11. Two-dimensional topological insulators with tunable band gaps: Single-layer HgTe and HgSe.

    PubMed

    Li, Jin; He, Chaoyu; Meng, Lijun; Xiao, Huaping; Tang, Chao; Wei, Xiaolin; Kim, Jinwoong; Kioussis, Nicholas; Stocks, G Malcolm; Zhong, Jianxin

    2015-01-01

    Two-dimensional (2D) topological insulators (TIs) with large band gaps are of great importance for the future applications of quantum spin Hall (QSH) effect. Employing ab initio electronic calculations we propose a novel type of 2D topological insulators, the monolayer (ML) low-buckled (LB) mercury telluride (HgTe) and mercury selenide (HgSe), with tunable band gap. We demonstrate that LB HgTe (HgSe) monolayers undergo a trivial insulator to topological insulator transition under in-plane tensile strain of 2.6% (3.1%) due to the combination of the strain and the spin orbital coupling (SOC) effects. Furthermore, the band gaps can be tuned up to large values (0.2 eV for HgTe and 0.05 eV for HgSe) by tensile strain, which far exceed those of current experimentally realized 2D quantum spin Hall insulators. Our results suggest a new type of material suitable for practical applications of 2D TI at room-temperature. PMID:26365502

  12. Two-dimensional topological insulators with tunable band gaps: Single-layer HgTe and HgSe

    SciTech Connect

    Li, Jin; He, Chaoyu; Meng, Lijun; Xiao, Huaping; Tang, Chao; Wei, Xiaolin; Kim, Jinwoong; Kioussis, Nicholas; Stocks, G. Malcolm; Zhong, Jianxin

    2015-09-14

    Here, we report that two-dimensional (2D) topological insulators (TIs) with large band gaps are of great importance for the future applications of quantum spin Hall (QSH) effect. Employing ab initio electronic calculations we propose a novel type of 2D topological insulators, the monolayer (ML) low-buckled (LB) mercury telluride (HgTe) and mercury selenide (HgSe), with tunable band gap. We demonstrate that LB HgTe (HgSe) monolayers undergo a trivial insulator to topological insulator transition under in-plane tensile strain of 2.6% (3.1%) due to the combination of the strain and the spin orbital coupling (SOC) effects. Furthermore, the band gaps can be tuned up to large values (0.2 eV for HgTe and 0.05 eV for HgSe) by tensile strain, which far exceed those of current experimentally realized 2D quantum spin Hall insulators. Our results suggest a new type of material suitable for practical applications of 2D TI at room-temperature.

  13. Two-dimensional topological insulators with tunable band gaps: Single-layer HgTe and HgSe

    DOE PAGESBeta

    Li, Jin; He, Chaoyu; Meng, Lijun; Xiao, Huaping; Tang, Chao; Wei, Xiaolin; Kim, Jinwoong; Kioussis, Nicholas; Stocks, G. Malcolm; Zhong, Jianxin

    2015-09-14

    Here, we report that two-dimensional (2D) topological insulators (TIs) with large band gaps are of great importance for the future applications of quantum spin Hall (QSH) effect. Employing ab initio electronic calculations we propose a novel type of 2D topological insulators, the monolayer (ML) low-buckled (LB) mercury telluride (HgTe) and mercury selenide (HgSe), with tunable band gap. We demonstrate that LB HgTe (HgSe) monolayers undergo a trivial insulator to topological insulator transition under in-plane tensile strain of 2.6% (3.1%) due to the combination of the strain and the spin orbital coupling (SOC) effects. Furthermore, the band gaps can be tunedmore » up to large values (0.2 eV for HgTe and 0.05 eV for HgSe) by tensile strain, which far exceed those of current experimentally realized 2D quantum spin Hall insulators. Our results suggest a new type of material suitable for practical applications of 2D TI at room-temperature.« less

  14. Two-dimensional topological insulators with tunable band gaps: Single-layer HgTe and HgSe

    NASA Astrophysics Data System (ADS)

    Li, Jin; He, Chaoyu; Meng, Lijun; Xiao, Huaping; Tang, Chao; Wei, Xiaolin; Kim, Jinwoong; Kioussis, Nicholas; Malcolm Stocks, G.; Zhong, Jianxin

    2015-09-01

    Two-dimensional (2D) topological insulators (TIs) with large band gaps are of great importance for the future applications of quantum spin Hall (QSH) effect. Employing ab initio electronic calculations we propose a novel type of 2D topological insulators, the monolayer (ML) low-buckled (LB) mercury telluride (HgTe) and mercury selenide (HgSe), with tunable band gap. We demonstrate that LB HgTe (HgSe) monolayers undergo a trivial insulator to topological insulator transition under in-plane tensile strain of 2.6% (3.1%) due to the combination of the strain and the spin orbital coupling (SOC) effects. Furthermore, the band gaps can be tuned up to large values (0.2 eV for HgTe and 0.05 eV for HgSe) by tensile strain, which far exceed those of current experimentally realized 2D quantum spin Hall insulators. Our results suggest a new type of material suitable for practical applications of 2D TI at room-temperature.

  15. Intense charge transfer surface based on graphene and thymine-Hg(II)-thymine base pairs for detection of Hg(2.).

    PubMed

    Li, Jiao; Lu, Liping; Kang, Tianfang; Cheng, Shuiyuan

    2016-03-15

    In this article, we developed an electrochemiluminescence (ECL) sensor with a high-intensity charge transfer interface for Hg(2+) detection based on Hg(II)-induced DNA hybridization. The sensor was fabricated by the following simple method. First, graphene oxide (GO) was electrochemically reduced onto a glassy carbon electrode through cyclic voltammetry. Then, amino-labeled double-stranded (ds)DNA was assembled on the electrode surface using 1-pyrenebutyric acid N-hydroxysuccinimide as a linker between GO and DNA. The other terminal of dsDNA, which was labeled with biotin, was linked to CdSe quantum dots via biotin-avidin interactions. Reduced graphene oxide has excellent electrical conductivity. dsDNA with T-Hg(II)-T base pairs exhibited more facile charge transfer. They both accelerate the electron transfer performance and sensitivity of the sensor. The increased ECL signals were logarithmically linear with the concentration of Hg(II) when Hg(2+) was present in the detection solution. The linear range of the sensor was 10(-11) to 10(-8)mol/L (R=0.9819) with a detection limit of 10(-11)mol/L. This biosensor exhibited satisfactory results when it was used to detect Hg(II) in real water samples. The biosensor with high-intense charge transfer performance is a prospect avenue to pursue more and more sensitive detection method. PMID:26499870

  16. Fractionation of mercury isotopes by photo-oxidation in aquatic systems

    NASA Astrophysics Data System (ADS)

    Ghosh, S.; Bergquist, B. A.; Blum, J. D.

    2009-12-01

    Mercury is a globally distributed pollutant that bioaccumulates in aquatic food webs, even in remote locations. The recent discovery of both large mass-dependent fractionation (MDF) and mass-independent fractionation (MIF) has made the promise of tracing this neurotoxin through the environment by using its isotopes very exciting. So far, the only process demonstrated experimentally to produce large MIF for Hg (similar in magnitude to the MIF observed in natural samples such as fish) is photochemical reduction (Bergquist and Blum, 2007). During photo-reduction, MIF of the odd isotopes was observed with the odd isotopes (199Hg, 201Hg) being preferentially enriched in the aqueous phase. Bergquist and Blum, 2007, suggested that the cause of MIF was the magnetic isotope effect (MIE), which is purely a kinetic phenomenon involving radical pair intermediates. Radical pairs with odd isotopes, which have non-zero nuclear spin and magnetic moments, can undergo spin conversion faster than radical pairs with non-magnetic even isotopes. This allows the odd and even isotopes to be preferentially enriched in different reaction products. MIE is a complex phenomenon that is dependent on several factors including hyperfine coupling, life-time of the radical pair, coupling strength of the radical pair, spin-orbital coupling, diffusion factors, and the solvent cage (space) in which the reaction occurs. Only under rare circumstances will all the factors be suitable for the expression of MIE in natural reactions. The goal of this study was to conduct aqueous photo-oxidation reactions to investigate whether this redox pathway expresses MIF (in the form of MIE) similar to the photo-reduction pathway. In natural systems, net photo-reduction of Hg (II) species results in the release of Hg(0) vapor to the atmosphere. However this net photo-reduction is a combination of both photo-reduction and photo-oxidation. In their experiments, Bergquist and Blum 2007, only investigated the aqueous photo

  17. Immobilization of Hg(II) by coprecipitation in sulfate-cement systems.

    PubMed

    Serrano, Susana; Vlassopoulos, Dimitri; Bessinger, Brad; O'Day, Peggy A

    2012-06-19

    Uptake and molecular speciation of dissolved Hg during formation of Al- or Fe-ettringite-type and high-pH phases were investigated in coprecipitation and sorption experiments of sulfate-cement treatments used for soil and sediment remediation. Ettringite and minor gypsum were identified by XRD as primary phases in Al systems, whereas gypsum and ferrihydrite were the main products in Hg-Fe precipitates. Characterization of Hg-Al solids by bulk Hg EXAFS, electron microprobe, and microfocused-XRF mapping indicated coordination of Hg by Cl ligands, multiple Hg and Cl backscattering atoms, and concentration of Hg as small particles. Thermodynamic predictions agreed with experimental observations for bulk phases, but Hg speciation indicated lack of equilibration with the final solution. Results suggest physical encapsulation of Hg as a polynuclear chloromercury(II) salt in ettringite as the primary immobilization mechanism. In Hg-Fe solids, structural characterization indicated Hg coordination by O atoms only and Fe backscattering atoms that is consistent with inner-sphere complexation of Hg(OH)(2)(0) coprecipitated with ferrihydrite. Precipitation of ferrihydrite removed Hg from solution, but the resulting solid was sufficiently hydrated to allow equilibration of sorbed Hg species with the aqueous solution. Electron microprobe XRF characterization of sorption samples with low Hg concentration reacted with cement and FeSO(4) amendment indicated correlation of Hg and Fe, supporting the interpretation of Hg removal by precipitation of an Fe(III) oxide phase. PMID:22594782

  18. Isotope separation by photochromatography

    DOEpatents

    Suslick, Kenneth S.

    1977-01-01

    An isotope separation method which comprises physically adsorbing an isotopically mixed molecular species on an adsorptive surface and irradiating the adsorbed molecules with radiation of a predetermined wavelength which will selectively excite a desired isotopic species. Sufficient energy is transferred to the excited molecules to desorb them from the surface and thereby separate them from the unexcited undesired isotopic species. The method is particularly applicable to the separation of hydrogen isotopes.

  19. Isotope separation by photochromatography

    DOEpatents

    Suslick, K.S.

    1975-10-03

    A photochromatographic method for isotope separation is described. An isotopically mixed molecular species is adsorbed on an adsorptive surface, and the adsorbed molecules are irradiated with radiation of a predetermined wavelength which will selectively excite desired isotopic species. Sufficient energy is transferred to the excited molecules to desorb them from the surface and thus separate them from the undesired isotopic species. The method is particularly applicable to the separation of hydrogen isotopes. (BLM)

  20. DoE optimization of a mercury isotope ratio determination method for environmental studies.

    PubMed

    Berni, Alex; Baschieri, Carlo; Covelli, Stefano; Emili, Andrea; Marchetti, Andrea; Manzini, Daniela; Berto, Daniela; Rampazzo, Federico

    2016-05-15

    By using the experimental design (DoE) technique, we optimized an analytical method for the determination of mercury isotope ratios by means of cold-vapor multicollector ICP-MS (CV-MC-ICP-MS) to provide absolute Hg isotopic ratio measurements with a suitable internal precision. By running 32 experiments, the influence of mercury and thallium internal standard concentrations, total measuring time and sample flow rate was evaluated. Method was optimized varying Hg concentration between 2 and 20ngg(-1). The model finds out some correlations within the parameters affect the measurements precision and predicts suitable sample measurement precisions for Hg concentrations from 5ngg(-1) Hg upwards. The method was successfully applied to samples of Manila clams (Ruditapes philippinarum) coming from the Marano and Grado lagoon (NE Italy), a coastal environment affected by long term mercury contamination mainly due to mining activity. Results show different extents of both mass dependent fractionation (MDF) and mass independent fractionation (MIF) phenomena in clams according to their size and sampling sites in the lagoon. The method is fit for determinations on real samples, allowing for the use of Hg isotopic ratios to study mercury biogeochemical cycles in complex ecosystems. PMID:26992509

  1. Mercury isotope signatures of seawater discharged from a coal-fired power plant equipped with a seawater flue gas desulfurization system.

    PubMed

    Lin, Haiying; Peng, Jingji; Yuan, Dongxing; Lu, Bingyan; Lin, Kunning; Huang, Shuyuan

    2016-07-01

    Seawater flue gas desulfurization (SFGD) systems are commonly used to remove acidic SO2 from the flue gas with alkaline seawater in many coastal coal-fired power plants in China. However, large amount of mercury (Hg) originated from coal is also transferred into seawater during the desulfurization (De-SO2) process. This research investigated Hg isotopes in seawater discharged from a coastal plant equipped with a SFGD system for the first time. Suspended particles of inorganic minerals, carbon residuals and sulfides are enriched in heavy Hg isotopes during the De-SO2 process. δ(202)Hg of particulate mercury (PHg) gradually decreased from -0.30‰ to -1.53‰ in study sea area as the distance from the point of discharge increased. The results revealed that physical mixing of contaminated De-SO2 seawater and uncontaminated fresh seawater caused a change in isotopic composition of PHg isotopes in the discharging area; and suggested that both De-SO2 seawater and local background contributed to PHg. The impacted sea area predicted with isotopic tracing technique was much larger than that resulted from a simple comparison of pollutant concentration. It was the first attempt to apply mercury isotopic composition signatures with two-component mixing model to trace the mercury pollution and its influence in seawater. The results could be beneficial to the coal-fired plants with SFGD systems to assess and control Hg pollution in sea area. PMID:27155100

  2. Overcoming phytoremediation limitations. A case study of Hg contaminated soil

    NASA Astrophysics Data System (ADS)

    Barbafieri, Meri

    2013-04-01

    Phytoremediation is a broad term that comprises several technologies to clean up water and soil. Despite the numerous articles appearing in scientific journals, very few field applications of phytoextraction have been successfully realized. The research here reported on Phytoextraction, the use the plant to "extract" metals from contaminated soil, is focused on implementations to overcome two main drawbacks: the survival of plants in unfavorable environmental conditions (contaminant toxicity, low fertility, etc.) and the often lengthy time it takes to reduce contaminants to the requested level. Moreover, to overcome the imbalance between the technology's potential and its drawbacks, there is growing interest in the use of plants to reduce only the fraction that is the most hazardous to the environment and human health, that is to target the bioavailable fractions of metals in soil. Bioavailable Contaminant Stripping (BCS) would be a remediation approach focused to remove the bioavailable metal fractions. BCS have been used in a mercury contaminated soil from Italian industrial site. Bioavailable fractions were determined by sequential extraction with H2O and NH4Cl.Combined treatments of plant hormone and thioligand to strength Hg uptake by crop plants (Brassica juncea and Helianthus annuus) were tested. Plant biomass, evapotranspiration, Hg uptake and distribution following treatments were compared. Results indicate the plant hormone, cytokinine (CK) foliar treatment, increased evapotranspiration rate in both tested plants. The Hg uptake and translocation in both tested plants increased with simultaneous addition of CK and TS treatments. B. juncea was the most effective in Hg uptake. Application of CK to plants grown in TS-treated soil lead to an increase in Hg concentration of 232% in shoots and 39% in roots with respect to control. While H. annuus gave a better response in plant biomass production, the application of CK to plants grown in TS-treated soil lead to

  3. Bioaccumulation of Hg in the mushroom Pleurotus ostreatus

    SciTech Connect

    Bressa, G.; Cima, L.; Costa, P.

    1988-10-01

    The possibility of utilizing industrial, urban, and other wastes for the growth of a product which is directly edible by humans is fascinating. However, it is possible that many wastes containing toxic substances, for example, heavy metals, could reach the food chain and produce adverse effects on human health. To this end, we studied the possibility of bioaccumulation of Hg by a mushroom, Pleurotus ostreatus, grown on an artificial compost containing this element. Concentrations of 0.05, 0.1, and 0.2 mg/kg of Hg as Hg(NO/sub 3/)/sub 2/.H/sub 2/O were added to three groups of the same compost, successively inoculated with the mycelia of the mushroom. Higher concentrations strongly reduced the growth of the mycelia and therefore were not utilized. The concentrations of Hg in the substrate and in the mushroom were evaluated by AAS. The range of the accumulation factor was found to be 65-140, i.e., very marked. This finding suggests that the cultivation of P. ostreatus on substrates containing Hg from industrial and urban wastes could involve possible risks to human health.

  4. Defect chemistry and characterization of (Hg, Cd)Te

    NASA Technical Reports Server (NTRS)

    Vydyanath, H. R.

    1981-01-01

    Single crystal samples of phosphorus doped Hg sub 0.8 Cd sub 0.2 Te were anneald at temperatures varying from 450 C to 600 C in various Hg atmospheres. The samples were quenched to room temperature from the annealing temperatures. Hall effect and mobility measurements were performed at 77 K on all these samples. The results indicate the crystals to be p type for a total phosphorus concentration of 10 to the 19th power/cu cm in all the samples. The hole concentration at 77 K increases with increasing Hg pressures at 450 C and 500 C contrary to the observation in undoped crystals. Also, at low Hg pressures the concentration of holes in the phosphorus doped crystals is lower than in the undoped crystals. The hole concentration in all the samples is lower than the intrinsic carrier concentration at the annealing temperatures. The hole mobility in the doped crystals is similar to that in the undoped crystals. A defect model according to which phosphorus behaves as a single acceptor interstitially, occupying Te lattice sites while it acts as a single donor occupying Hg lattice sites was established. Equilibrum constants established for the incorporation of all the phosphorus species explain the experimental results

  5. 40 CFR 60.4120 - General Hg budget trading program permit requirements.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 6 2010-07-01 2010-07-01 false General Hg budget trading program... budget trading program permit requirements. (a) For each Hg Budget source required to have a title V... source covered by the Hg Budget permit, all applicable Hg Budget Trading Program requirements and...

  6. 40 CFR 60.4122 - Information requirements for Hg budget permit applications.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... following elements concerning the Hg Budget source for which the application is submitted, in a format prescribed by the permitting authority: (a) Identification of the Hg Budget source; (b) Identification of each Hg Budget unit at the Hg Budget source; and (c) The standard requirements under § 60.4106....

  7. 40 CFR 60.4154 - Compliance with Hg budget emissions limitation.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 6 2010-07-01 2010-07-01 false Compliance with Hg budget emissions... Times for Coal-Fired Electric Steam Generating Units Hg Allowance Tracking System § 60.4154 Compliance with Hg budget emissions limitation. (a) Allowance transfer deadline. The Hg allowances are...

  8. 40 CFR 60.4110 - Authorization and Responsibilities of Hg designated representative.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... Hg designated representative. 60.4110 Section 60.4110 Protection of Environment ENVIRONMENTAL... Emission Guidelines and Compliance Times for Coal-Fired Electric Steam Generating Units Hg Designated Representative for Hg Budget Sources § 60.4110 Authorization and Responsibilities of Hg designated...

  9. 40 CFR 75.83 - Calculation of Hg mass emissions and heat input rate.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 16 2010-07-01 2010-07-01 false Calculation of Hg mass emissions and... (CONTINUED) AIR PROGRAMS (CONTINUED) CONTINUOUS EMISSION MONITORING Hg Mass Emission Provisions § 75.83 Calculation of Hg mass emissions and heat input rate. The owner or operator shall calculate Hg mass...

  10. 40 CFR 60.4122 - Information requirements for Hg budget permit applications.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 6 2010-07-01 2010-07-01 false Information requirements for Hg budget... requirements for Hg budget permit applications. A complete Hg Budget permit application shall include the following elements concerning the Hg Budget source for which the application is submitted, in a...

  11. 40 CFR 60.4121 - Submission of Hg budget permit applications.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 6 2010-07-01 2010-07-01 false Submission of Hg budget permit... Times for Coal-Fired Electric Steam Generating Units Permits § 60.4121 Submission of Hg budget permit applications. (a) Duty to apply. The Hg designated representative of any Hg Budget source required to have...

  12. Purification of HgI.sub.2 for nuclear detector fabrication

    DOEpatents

    Schieber, Michael M.

    1978-01-01

    A process for purification of mercuric iodide (HgI.sub.2) to be used as a source material for the growth of detector quality crystals. The high purity HgI.sub.2 raw material is produced by a combination of three stages: synthesis of HgI.sub.2 from Hg and I.sub.2, repeated sublimation, and zone refining.

  13. 40 CFR 60.4123 - Hg budget permit contents and term.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... from the compliance account of the Hg Budget source covered by the permit. (c) The term of the Hg... 40 Protection of Environment 6 2010-07-01 2010-07-01 false Hg budget permit contents and term. 60... Coal-Fired Electric Steam Generating Units Permits § 60.4123 Hg budget permit contents and term....

  14. Thermodynamics limits the reactivity of BrHg radical with volatile organic compounds

    NASA Astrophysics Data System (ADS)

    Dibble, Theodore S.; Schwid, Abraham C.

    2016-08-01

    Mercury emissions to the atmosphere primarily consist of Hg(0), which tends not to enter ecosystems until it is oxidized. Atomic bromine initiates oxidation of Hg(0) via the BrHg intermediate, but the further reactions of BrHg are just beginning to be explored. Here we use quantum chemistry to determine that hydrogen abstraction from hydrocarbons by BrHg is so endothermic as to be irrelevant. Bonds between BrHg and carbon atoms are so weak that BrHg addition to carbon-carbon double bonds atoms will be somewhat ineffective in leading to further reactions.

  15. Effects of fulvic substances on the distribution and migration of Hg in landfill leachate.

    PubMed

    Xiaoli, Chai; Guixiang, Liu; Jun, Wu; Huanhuan, Tong; Rong, Ji; Youcai, Zhao

    2011-05-01

    Mercury (Hg) distribution and migration in different landfill stabilization processes were evaluated in this study. Wide ranges of Hg concentrations were observed because of the heterogeneity and variability of landfill refuse. In addition, temporally variable conditions, including pH, organic matter, and vegetation cover, which influence Hg migration in landfills, may also affect the temporal distribution of Hg in landfill refuse. The main fraction of Hg, elemental Hg, decreased with time, while the stable fractions of Hg increased. The fulvic acid (FA) extracted from the landfill leachate had much lower overall Hg-complexation stability constants, which suggests that organic S groups might have been rapidly saturated by small amounts of Hg while leaving oxygen functional groups, such as carboxylic functional or phenolic groups, acting as the primary binding sites for Hg. PMID:21468428

  16. Metal stable isotope signatures as tracers in environmental geochemistry.

    PubMed

    Wiederhold, Jan G

    2015-03-01

    The biogeochemical cycling of metals in natural systems is often accompanied by stable isotope fractionation which can now be measured due to recent analytical advances. In consequence, a new research field has emerged over the last two decades, complementing the traditional stable isotope systems (H, C, O, N, S) with many more elements across the periodic table (Li, B, Mg, Si, Cl, Ca, Ti, V, Cr, Fe, Ni, Cu, Zn, Ge, Se, Br, Sr, Mo, Ag, Cd, Sn, Sb, Te, Ba, W, Pt, Hg, Tl, U) which are being explored and potentially applicable as novel geochemical tracers. This review presents the application of metal stable isotopes as source and process tracers in environmental studies, in particular by using mixing and Rayleigh model approaches. The most important concepts of mass-dependent and mass-independent metal stable isotope fractionation are introduced, and the extent of natural isotopic variations for different elements is compared. A particular focus lies on a discussion of processes (redox transformations, complexation, sorption, precipitation, dissolution, evaporation, diffusion, biological cycling) which are able to induce metal stable isotope fractionation in environmental systems. Additionally, the usefulness and limitations of metal stable isotope signatures as tracers in environmental geochemistry are discussed and future perspectives presented. PMID:25640608

  17. Effect of doping on electronic properties of HgSe

    NASA Astrophysics Data System (ADS)

    Nag, Abhinav; Sastri, O. S. K. S.; Kumar, Jagdish

    2016-05-01

    First principle study of electronic properties of pure and doped HgSe have been performed using all electron Full Potential Linearized Augmented Plane Wave (FP-LAPW) method using ELK code. The electronic exchange and co-relations are considered using Generalized Gradient Approach (GGA). Lattice parameter, Density of States (DOS) and Band structure calculations have been performed. The total energy curve (Energy vs Lattice parameter), DOS and band structure calculations are in good agreement with the experimental values and those obtained using other DFT codes. The doped material is studied within the Virtual Crystal Approximation (VCA) with doping levels of 10% to 25% of electrons (hole) per unit cell. Results predict zero band gap in undopedHgSe and bands meet at Fermi level near the symmetry point D. For doped HgSe, we found that by electron (hole) doping, the point where conduction and valence bands meet can be shifted below (above) the fermi level.

  18. [Experimental Research of Hg (II) Removal from Aqueous Solutions of HgCl2 with Nano-TiO2].

    PubMed

    Zhou, Xiong; Zhang, Jin-yang; Wang, Ding-yong; Qin, Cai-qing; Xu, Feng; Luo Cheng-zhong; Yang, Xi

    2016-01-15

    Mercury removal from aqueous solutions of HgCl2 was studied by indoor simulation experiments, and the effects of three different diameter of particles of Nano-TiO2 ( Nano-Titanium Dioxide) at different dosage, pH, adsorption time and the initial concentration of Hg2+ on the mercury adsorption from simulated wastewater were investigated. The single factor experiments showed that the optimal conditions were: 7.5 g x L(-1) of 5 nm TiO2 or 2.0 g x L(-1) of 100 nm TiO2, pH 8.0, initial concentration of Hg2+ 15 x mg x L(-1) adsorption time 5 min, and under these conditions the adsorption rates reached 99.5% and 99.3%, relatively. When the content of 25 nm TiO2 was 10 g x L(-1), and the other conditions were pH 8.0, initial concentration of Hg2+ 15 mg x L(-1), adsorption time 60 min, the adsorption rate was 62.8%. The Hg(II) removal effects of the TiO2 particles with different diameters followed the order of 100 nm TiO2 > 5 nm TiO2 > 25 nm TiO2. Component adsorption results showed that the 5 nm TiO2 component adsorption effect was superior to its single adsorption effect, while there was little difference between 100 nm TiO2 component adsorption effect and its single adsorption effect. The results of orthogonal experiments indicated that the influencing factors of the adsorption rate followed the order of pH > the initial concentration of Hg2+ > time > dosage. The optimal experiment scheme was: pH 8.0, a dosage of 100 nm Nano-TiO2 of 2.0 g x L(-1) an initial Hg2+ concentration of 25 mg x L(-1) and adsorption time of 10 min. Under the experimental conditions, the maximum adsorption rate reached 99.9%, at the same time, the equilibrium concentration of Hg(II) was 0.033 mg x L(-1) < 0.05 mg x L(-1), below the current enterprise rules of water pollutants in mercury emissions limits. In addition, the maximum adsorptive capacity was 26.95 mg x g(-1). The adsorption isotherm was in line with the Langmuir isotherm equation, indicating that the Hg(II) uptake by 100 nm Nano-TiO2

  19. 13C and 199Hg nuclear magnetic resonance spectroscopic study of alkenemercurinium ions: Effect of methyl substituents on 199Hg chemical shifts

    PubMed Central

    Olah, George A.; Garcia-Luna, Armando

    1980-01-01

    The long-lived ethylene, cyclohexene, and norbornenemercurinium ions prepared in superacidic, low-nucleophilic media have been studied by 13C and 199Hg NMR spectroscopy. The norbornenemercurinium ion shows temperature-dependent 13C and 199Hg NMR spectra, consistent with equilibration via rapid hydride and Wagner-Meerwin shifts. The 199Hg NMR shifts of a series of alkylmercury bromides were also obtained in order to elucidate the effect of methyl substituents on 199Hg NMR chemical shifts. PMID:16592870

  20. Raman spectroscopic investigations of Hg-Cd-Te melts

    NASA Technical Reports Server (NTRS)

    Morrobel-Sosa, Anny

    1987-01-01

    Raman scattering measurements are reported for a series of Hg sub1-xCd subxTe (with x less than or =0.2) materials from 295 K (room temperature) to 1126K (up to and above their liquidus temperatures), and for Hg sub1-xCd subxTe (x=0.3) at 285K. The samples were contained in high-temperature optically-flat fused silica cell. Variable temperature measurements were effected in a three-zone, high-temperature furnace equipped with optical windows, and monitored externally by three independently programmable temperature controllers. All studies were made in the backscattering geometry using the 5145 A line of an Ar+ ion laser, with incident power less than 250 mW, as the excitiation source. An intensity enhancement is observed for a mode in each of the compositions studied. The frequency of this mode varies with composition, 142/cm for HgTe, and 128/cm for both the Hg sub1-xCd subxTe (x=0.053 and 0.204) samples. In addition, a shift to lower frequency as a function of temperature is observed in all samples. This shift is most prominent for the x=0.053 sample. The temperature dependence of these modes as the liquidus temperatures are achieved and surpassed for these samples is presented as being associated with a structural transition in the Hg-rich compositions of the Hg sub1-xCd subxTe series. To our knowledge, this is the first reported study of Raman scattering by phonons in the melts of these materials.

  1. Highly luminescent Ag+ nanoclusters for Hg2+ ion detection

    NASA Astrophysics Data System (ADS)

    Yuan, Xun; Yeow, Teik Jin; Zhang, Qingbo; Lee, Jim Yang; Xie, Jianping

    2012-03-01

    A simple, low-cost and label-free Hg2+ ion sensor has been developed by using novel luminescent Ag+ nanoclusters (NCs) with an excellent optical property (quantum yield = 15%), an ultra-high ratio of active Ag+ species in the NC surface (~100%), and an ultra-short diffusion path length of Hg2+ ions to access the NC surface (~0.5 nm).A simple, low-cost and label-free Hg2+ ion sensor has been developed by using novel luminescent Ag+ nanoclusters (NCs) with an excellent optical property (quantum yield = 15%), an ultra-high ratio of active Ag+ species in the NC surface (~100%), and an ultra-short diffusion path length of Hg2+ ions to access the NC surface (~0.5 nm). Electronic supplementary information (ESI) available: Experimental details of the synthesis of b-Ag NCs; time-resolved evolution of photoemission spectra of the b-Ag NCs in toluene; photoexcitation spectrum of the b-Ag NCs in toluene; comparison of the luminescence of b-Ag NCs at different temperatures (4 and 25 °C) TEM image of the b-Ag NCs in toluene; optical properties of r-Ag NCs obtained by the reduction of b-Ag NCs in toluene; XPS spectra of b-Ag NCs, thiolate-Ag+ complexes, r-Ag NCs, and large Ag nanoparticles; TEM image of the Hg2+-Ag NCs; photostability of the b-Ag NCs; tolerance studies of the b-Ag NCs over other metal ions; tolerance studies of the b-Ag NCs over common thiol ligands (e.g., GSH) and anions; relative luminescence of the b-Ag NCs in different real water samples in the presence of Hg2+ ions; and relative luminescence of the b-Ag NCs in NaCl solution with different concentrations. See DOI: 10.1039/c2nr11999d

  2. The Hg isoelectronic defect in ZnO

    NASA Astrophysics Data System (ADS)

    Cullen, J.; Johnston, K.; Dunker, D.; McGlynn, E.; Yakovlev, D. R.; Bayer, M.; Henry, M. O.

    2013-11-01

    We report a study of the luminescence due to Hg in ZnO, concentrating on the main zero phonon line (ZPL) at 3.2766(1) eV and its associated phonon sidebands. For a sample implanted with radioactive 192Hg, the ZPL intensity, normalised to that of shallow bound exciton emission, is observed to decrease with an equivalent half-life of 4.5(1) h, very close to the 4.85(20) h half-life of 192Hg. ZnO implanted with stable Hg impurities produces the same luminescence spectrum. Temperature dependent measurements confirm that the zero phonon line is a thermalizing doublet involving one allowed and one largely forbidden transition from excited states separated by 0.91(1) meV to a common ground state. Uniaxial stress measurements show that the allowed transition takes place from an orbitally degenerate excited state to a non-degenerate ground state in a centre of trigonal (C3v) symmetry while the magneto-optical properties are characteristic of electron-hole pair recombination at an isoelectronic defect. The doublet luminescence is assigned to bound exciton recombination involving exchange-split Γ5 and Γ1,2 excited states (using C6v symmetry labels; Γ3 and Γ1,2 using C3v labels) at isoelectronic Hg impurities substituting for Zn in the crystal. The electron and hole g values deduced from the magneto-optical data indicate that this Hg impurity centre in ZnO is hole-attractive.

  3. The Hg isoelectronic defect in ZnO

    SciTech Connect

    Cullen, J.; McGlynn, E. Henry, M. O.; Johnston, K.; Dunker, D.; Bayer, M.; Yakovlev, D. R.

    2013-11-21

    We report a study of the luminescence due to Hg in ZnO, concentrating on the main zero phonon line (ZPL) at 3.2766(1) eV and its associated phonon sidebands. For a sample implanted with radioactive {sup 192}Hg, the ZPL intensity, normalised to that of shallow bound exciton emission, is observed to decrease with an equivalent half-life of 4.5(1) h, very close to the 4.85(20) h half-life of {sup 192}Hg. ZnO implanted with stable Hg impurities produces the same luminescence spectrum. Temperature dependent measurements confirm that the zero phonon line is a thermalizing doublet involving one allowed and one largely forbidden transition from excited states separated by 0.91(1) meV to a common ground state. Uniaxial stress measurements show that the allowed transition takes place from an orbitally degenerate excited state to a non-degenerate ground state in a centre of trigonal (C{sub 3v}) symmetry while the magneto-optical properties are characteristic of electron-hole pair recombination at an isoelectronic defect. The doublet luminescence is assigned to bound exciton recombination involving exchange-split Γ{sub 5} and Γ{sub 1,2} excited states (using C{sub 6v} symmetry labels; Γ{sub 3} and Γ{sub 1,2} using C{sub 3v} labels) at isoelectronic Hg impurities substituting for Zn in the crystal. The electron and hole g values deduced from the magneto-optical data indicate that this Hg impurity centre in ZnO is hole-attractive.

  4. Fermionic-Bosonic Couplings in a Weakly Deformed Odd-Mass Nucleus ^{93}_{41}Nb

    SciTech Connect

    Orce, J. N.; Holt, J. D.; Linnemann, A.; McKay, C. J.; Fransen, C.; Jolie, J.; Kuo, T.T.S.; Lesher, S. R.; McEllistrem, M. T.; Pietralla, N.; Warr, N.; Werner, V.; Yates, S. W.

    2010-01-01

    A comprehensive level scheme of {sup 93}Nb below 2 MeV has been constructed from information obtained with the {sup 93}Nb(n,n{prime}{gamma}) and the {sup 94}Zr(p,2n{gamma}{gamma}){sup 93}Nb reactions. Branching ratios, lifetimes, transition multipolarities, and spin assignments have been determined. From M1 and E2 strengths, fermionic-bosonic excitations of isoscalar and isovector characters have been identified from the weak couplings of the {pi}1g{sub 9/2} {circle_times} {sub 40}{sup 92}Zr and {pi}2p{sub 1/2}{sup -1} {circle_times} {sub 42}{sup 94}Mo configurations. A microscopic interpretation of such excitations is obtained from shell-model calculations, which use low-momentum effective interactions.

  5. Identification of Mixed-Symmetry States in an Odd-Mass Nearly Spherical Nucleus

    SciTech Connect

    Orce, J. N.; McKay, C. J.; Lesher, S. R.; Kumar, A.; McEllistrem, M. T.; Holt, J. D.; Holt, J. W.; Kuo, T. T. S.; Linnemann, A.; Fransen, C.; Warr, N.; Werner, V.; Jolie, J.; Pietralla, N.; Yates, S. W.

    2006-08-11

    The low-spin structure of {sup 93}Nb has been studied using the (n,n{sup '}{gamma}) reaction at neutron energies ranging from 1.5 to 3 MeV and the {sup 94}Zr(p,2n{gamma}){sup 93}Nb reaction at bombarding energies from 11.5 to 19 MeV. States at 1779.7 and 1840.6 keV, respectively, are proposed as mixed-symmetry states associated with the {pi}2p{sub 1/2}{sup -1}x(2{sub 1,MS}{sup +},{sup 94}Mo) coupling. These assignments are derived from the observed M1 and E2 transition strengths to the 2p{sub 1/2}{sup -1}x(2{sub 1}{sup +},{sup 94}Mo) symmetric one-phonon states, energy systematics, spins and parities, and comparison with shell model calculations.

  6. Cluster interpretation of parity doublet rotational bands in odd-mass nuclei

    SciTech Connect

    Adamian, G.G.; Antonenko, N.V.; Jolos, R.V.; Shneidman, T.M.

    2004-12-01

    The structure of parity doublet rotational bands in odd actinides and medium mass nuclei is described in a cluster model. The model is based on the assumption that cluster-type shapes are produced by the motion of the nuclear system in the mass-asymmetry coordinate. The calculated rotational bands and the electric dipole transitions between the members of the parity doublet are in good agreement with the experimental data.

  7. HgI2 low energy beta particle detector

    NASA Technical Reports Server (NTRS)

    Shah, K. S.; Squillante, M. R.; Entine, G.

    1990-01-01

    An HgI2 device structure was designed and tested which allows HgI2 to be used to make low-energy beta-particle detectors. The devices detected tritium beta particles with an efficiency of about 25 percent. A protective encapsulant has been developed which should protect the devices for up to 20 years and will attenuate only a small fraction of the beta particles. It is noted that the devices hold significant promise to provide a practical alternative to liquid scintillation counters and gas flow-through proportional counters.

  8. HgTe colloidal quantum dot LWIR infrared photodetectors

    NASA Astrophysics Data System (ADS)

    Pimpinella, R. E.; Ciani, A.; Guyot-Sionnest, P.; Grein, C.

    2015-08-01

    The majority of modern infrared photon imaging devices are based on epitaxially grown bulk semiconductor materials. Colloidal quantum dot (CQD)-based infrared devices provide great promise for significantly reducing cost as well as significantly increased operating temperatures of infrared imaging systems. In addition, CQD-based infrared devices greatly benefit from band gap tuning by controlling the CQD size rather than the composition. In this work, we investigate the absorption coefficient of HgTe CQD films as a function of temperature and cutoff wavelength. The optical absorption properties are predicted for defect-free HgTe films as well as films which vary from ideal.

  9. Crystal Growth of Solid Solution HgCdTe Alloys

    NASA Technical Reports Server (NTRS)

    Lehoczky, Sandor L.

    1997-01-01

    The growth of homogenous crystals of HgCdTe alloys is complicated by the large separation between their liquidus and solidus temperatures. Hg(1-x)Cd(x)Te is representative of several alloys which have electrical and optical properties that can be compositionally tuned for a number of applications. Limitations imposed by gravity during growth and results from growth under reduced conditions are described. The importance of residual accelerations was demonstrated by dramatic differences in compositional distribution observed for different attitudes of the space shuttle that resulted in different steady acceleration components.

  10. Active transport, substrate specificity, and methylation of Hg(II) in anaerobic bacteria

    SciTech Connect

    Schasfer, Jeffra; Rocks, Sara; Zheng, Wang; Liang, Liyuan; Gu, Baohua; Morel, Francois M

    2011-01-01

    The formation of methylmercury (MeHg), which is biomagnified in aquatic food chains and poses a risk to human health, is effected by some iron- and sulfate-reducing bacteria (FeRB and SRB) in anaerobic environments. However, very little is known regarding the mechanism of uptake of inorganic Hg by these organisms, in part because of the inherent difficulty in measuring the intracellular Hg concentration. By using the FeRB Geobacter sulfurreducens and the SRB Desulfovibrio desulfuricans ND132 as model organisms, we demonstrate that Hg(II) uptake occurs by active transport. We also establish that Hg(II) uptake by G. sulfurreducens is highly dependent on the characteristics of the thiols that bind Hg(II) in the external medium, with some thiols promoting uptake and methylation and others inhibiting both. The Hg(II) uptake system of D. desulfuricans has a higher affinity than that of G. sulfurreducens and promotes Hg methylation in the presence of stronger complexing thiols. We observed a tight coupling between Hg methylation and MeHg export from the cell, suggesting that these two processes may serve to avoid the build up and toxicity of cellular Hg. Our results bring up the question of whether cellular Hg uptake is specific for Hg(II) or accidental, occurring via some essential metal importer. Our data also point at Hg(II) complexation by thiols as an important factor controlling Hg methylation in anaerobic environments.

  11. Comparison of the characteristics and mechanisms of Hg(II) sorption by biochars and activated carbon.

    PubMed

    Xu, Xiaoyun; Schierz, Ariette; Xu, Nan; Cao, Xinde

    2016-02-01

    Two biochars were produced from bagasse and hickory chips (referred to as BB and HCB, respectively) and evaluated for their sorption ability of Hg(II) in aqueous solution. A commercial activated carbon (AC) which is commonly used for Hg(II) removal was included for comparison. Both biochars showed higher sorption capacities than AC, following the trend of BB>HCB>AC. The sorption of Hg(II) by BB and AC was mainly attributed to the formation of (COO)2Hg(II) and (O)2Hg(II). As a result, the adsorption capacity of Hg(II) by BB decreased 17.6% and 37.6% after COOH and OH were blocked, respectively and that of Hg(II) by AC decreased 6.63% and 62.2% for COOH and OH hindered, respectively. However, blocking the function groups had little effect on the Hg removal by HCB since sorption of Hg(II) by HCB was mainly resulted from the π electrons of CC and CO induced Hg-π binding. Further X-ray photoelectron spectroscopy analysis indicated the possibility of reduction of the Hg(II) to Hg(I) by phenol groups or π electrons during the removal of Hg(II) by both biochars. In conclusion, biochar is more effective than activated carbon in removing Hg(II) and there exists a high potential that biochar can be a substitute of activated carbon for removal of Hg(II) from wastewater. PMID:26520810

  12. Electronic structures of HgTe and CdTe surfaces and HgTe/CdTe interfaces

    NASA Technical Reports Server (NTRS)

    Schick, J. T.; Bose, S. M.; Chen, A.-B.

    1989-01-01

    A Green's-function method has been used to study the surface and interface electronic structures of the II-VI compounds HgTe and CdTe. Localized surface and resonance states near the cation-terminated (100) surface of CdTe and the anion-terminated surface of HgTe have been found for the ideal surfaces. The energies and strengths of these surface states are altered by surface perturbations. The bulk states near the surface are drastically modified by the creation of the surface, but the band gaps remain unchanged. Numerical evaluation of the local densities of states at the Gamma and J points shows that, at the (100) interface of HgTe/CdTe, the previously observed surface states are no longer present. However, in the interface region, bulk states of one material penetrate some distance into the other material.

  13. Determination of acute Hg emissions from solidified/stabilized cement waste forms

    SciTech Connect

    Hamilton, W.P.; Bowers, A.R.

    1997-12-31

    The chemical form of mercury in wastes to be solidified/stabilized may lead to volatile losses from the finished solidified/stabilized monolith. Elemental mercury vapor (Hg vapor) was detected in the headspace of batch reactors that contained solidified/stabilized ordinary Portland cement doped with mercuric oxide (HgO) or liquid elemental mercury [Hg{degree}(1)]. Vapor concentrations increased as a function of time and temperature; the headspace over the HgO samples was saturated in about one hour, while the samples containing Hg{degree}(1) reached approx. 20% of saturation in about two hours. Increased temperatures due to cement hydrolysis lead to increased Hg vapor evolution. Mercury solidified/stabilized as mercuric sulfide (HgS, black) emitted no Hg vapor. Data for the HgO and Hg{degree}(1) experiments were fit to a reversible first-order rate expression. Samples containing HgO displayed the greatest volatility as a result of the rapid dissolution of HgO and the subsequent formation of a strong driving force across the air-water interface. The evolution of Hg vapor from samples solidified/stabilized as Hg{degree}(1) is limited by mass transfer resistances that kinetically limit the dissolution of Hg{degree}(1) into the aqueous phase. The inert character of HgS prevents the evolution of detectable Hg in wastes solidified/stabilized as HgS. The findings of these studies may be important when considering treatment and disposal scenarios for Hg-containing wastes.

  14. Energy loss rate of a charged particle in HgTe/(HgTe, CdTe) quantum wells

    SciTech Connect

    Chen, Qinjun; Sin Ang, Yee; Wang, Xiaolin; Lewis, R. A.; Zhang, Chao

    2013-11-04

    The energy loss rate (ELR) of a charged particle in a HgTe/(HgTe, CdTe) quantum well is investigated. We consider scattering of a charged particle by the bulk insulating states in this type of topological insulator. It is found that the ELR characteristics due to the intraband excitation have a linear energy dependence while those due to interband excitation depend on the energy exponentially. An interesting quantitative result is that for a large range of the incident energy, the mean inelastic scattering rate is around a few terahertz.

  15. Slurry sampling flow injection chemical vapor generation inductively coupled plasma mass spectrometry for the determination of As, Cd, and Hg in cereals.

    PubMed

    Chen, Feng-Yi; Jiang, Shiuh-Jen

    2009-08-12

    A slurry sampling inductively coupled plasma mass spectrometry (ICP-MS) method has been developed for the determination of As, Cd, and Hg in cereals using flow injection chemical vapor generation (VG) as the sample introduction system. A slurry containing 6% m/v flour, 0.7% m/v thiourea, 0.4 microg mL(-1) Co(II), and 2.5% v/v HCl was injected into a VG-ICP-MS system for the determination of As, Cd, and Hg without dissolution and mineralization. Because the sensitivities of the elements studied in the slurry and that of aqueous solution were quite different, a standard addition method and an isotope dilution method were used for the determination of As, Cd, and Hg in selected cereal samples. The influences of vapor generation conditions and slurry preparation on the ion signals were reported. The effectiveness of the vapor generation sample introduction technique in alleviating various spectral interferences in ICP-MS analysis has been demonstrated. This method has been applied for the determination of As, Cd, and Hg in NIST SRM 1567a Wheat Flour reference material, NIST SRM 1568a Rice Flour reference material, and cereal samples obtained from local market. The As, Cd, and Hg analysis results of the reference materials agreed with the certified values. The method detection limits estimated from standard addition curves were about 0.10, 0.16, and 0.07 ng g(-1) for As, Cd, and Hg, respectively, in the original cereal samples. PMID:19606866

  16. METHOD OF ISOTOPE CONCENTRATION

    DOEpatents

    Spevack, J.S.

    1957-04-01

    An isotope concentration process is described which consists of exchanging, at two or more different temperature stages, two isotopes of an element between substances that are physically separate from each other and each of which is capable of containing either of the isotopes, and withdrawing from a point between at least two of the temperatare stages one of the substances containing an increased concentration of the desired isotope.

  17. Decay from the superdeformed bands in {sup 194}Hg

    SciTech Connect

    Henry, R.G.; Khoo, T.L.; Carpenter, M.P.

    1995-08-01

    Superdeformed bands in {sup 194}H g were studied using the early implementation of Gammasphere. The response functions for the Ge detectors were measured for the first time as part of this experiment. Experiments were performed with both a backed target (where the residue stopped in the Au backing) and a thin target (where the residue recoiled into vacuum). This will permit measurements of the decay times of the quasicontinuum {gamma}rays. The spectrum in coincidence with the yrast SD band in {sup 194}Hg reveals the same features as found in the quasicontinuum structure in {sup 192}Hg. These features include: statistical {gamma}rays feeding the SD band, a pronounced E2 peak from transitions feeding the SD band, a Ml/E2 bump at low energies that is associated with the last stages of feeding of the superdeformed band, and a quasicontinuous distribution from {gamma}rays linking SD and normal states, including a sizable clustering of strength around 1.7 MeV. The remarkable similarity of the spectra coincident with SD bands in {sup 192,194}Hg provides additional support for a statistical process for decay out of the SD states. This similarity contrasts with differences observed in the spectrum coincident with the SD band in the odd-even {sup 191}Hg, confirming the predictions about the role of pairing (in normal states) in influencing the shape of the decay-out spectrum.

  18. 40 CFR 60.4160 - Submission of Hg allowance transfers.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 6 2011-07-01 2011-07-01 false Submission of Hg allowance transfers. 60.4160 Section 60.4160 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) STANDARDS OF PERFORMANCE FOR NEW STATIONARY SOURCES Emission Guidelines and Compliance Times for Coal-Fired Electric...

  19. Cosmic ray isotopes

    NASA Technical Reports Server (NTRS)

    Stone, E. C.

    1973-01-01

    The isotopic composition of cosmic rays is studied in order to develop the relationship between cosmic rays and stellar processes. Cross section and model calculations are reported on isotopes of H, He, Be, Al and Fe. Satellite instrument measuring techniques separate only the isotopes of the lighter elements.

  20. Statistical clumped isotope signatures

    PubMed Central

    Röckmann, T.; Popa, M. E.; Krol, M. C.; Hofmann, M. E. G.

    2016-01-01

    High precision measurements of molecules containing more than one heavy isotope may provide novel constraints on element cycles in nature. These so-called clumped isotope signatures are reported relative to the random (stochastic) distribution of heavy isotopes over all available isotopocules of a molecule, which is the conventional reference. When multiple indistinguishable atoms of the same element are present in a molecule, this reference is calculated from the bulk (≈average) isotopic composition of the involved atoms. We show here that this referencing convention leads to apparent negative clumped isotope anomalies (anti-clumping) when the indistinguishable atoms originate from isotopically different populations. Such statistical clumped isotope anomalies must occur in any system where two or more indistinguishable atoms of the same element, but with different isotopic composition, combine in a molecule. The size of the anti-clumping signal is closely related to the difference of the initial isotope ratios of the indistinguishable atoms that have combined. Therefore, a measured statistical clumped isotope anomaly, relative to an expected (e.g. thermodynamical) clumped isotope composition, may allow assessment of the heterogeneity of the isotopic pools of atoms that are the substrate for formation of molecules. PMID:27535168

  1. Zirconium isotope separation

    SciTech Connect

    Siddall, M.B.

    1984-12-11

    A method of separating zirconium isotopes by converting the zirconium to its iodide salt prior to separation by usual isotope methods is disclosed. After separation the desired isotopes are converted from the salt to the metal by the van Arkel-de Boer iodide process.

  2. Statistical clumped isotope signatures.

    PubMed

    Röckmann, T; Popa, M E; Krol, M C; Hofmann, M E G

    2016-01-01

    High precision measurements of molecules containing more than one heavy isotope may provide novel constraints on element cycles in nature. These so-called clumped isotope signatures are reported relative to the random (stochastic) distribution of heavy isotopes over all available isotopocules of a molecule, which is the conventional reference. When multiple indistinguishable atoms of the same element are present in a molecule, this reference is calculated from the bulk (≈average) isotopic composition of the involved atoms. We show here that this referencing convention leads to apparent negative clumped isotope anomalies (anti-clumping) when the indistinguishable atoms originate from isotopically different populations. Such statistical clumped isotope anomalies must occur in any system where two or more indistinguishable atoms of the same element, but with different isotopic composition, combine in a molecule. The size of the anti-clumping signal is closely related to the difference of the initial isotope ratios of the indistinguishable atoms that have combined. Therefore, a measured statistical clumped isotope anomaly, relative to an expected (e.g. thermodynamical) clumped isotope composition, may allow assessment of the heterogeneity of the isotopic pools of atoms that are the substrate for formation of molecules. PMID:27535168

  3. Study of atomic structure of liquid Hg-In alloys using ab-initio molecular dynamics

    SciTech Connect

    Sharma, Nalini; Ahluwalia, P. K.; Thakur, Anil

    2015-05-15

    Ab-initio molecular dynamics simulations are performed to study the structural properties of liquid Hg-In alloys. The interatomic interactions are described by ab-initio pseudopotentials given by Troullier and Martins. Five liquid Hg-In mixtures (Hg{sub 10}In{sub 90}, Hg{sub 30}In{sub 70}, Hg{sub 50}In{sub 50}, Hg{sub 70}In{sub 30} and Hg{sub 90}In{sub 10}) at 299K are considered. The radial distribution function g(r) and structure factor S(q) of considered alloys are compared with respective experimental results for liquid Hg (l-Hg) and (l-In). The radial distribution function g(r) shows the presence of short range order in the systems considered. Smooth curves of Bhatia-Thornton partial structure factors factor shows the presence of liquid state in the considered alloys.

  4. Immobilization of Hg(II) by Coprecipitation in Sulfate-Cement Systems

    PubMed Central

    2012-01-01

    Uptake and molecular speciation of dissolved Hg during formation of Al- or Fe-ettringite-type and high-pH phases were investigated in coprecipitation and sorption experiments of sulfate-cement treatments used for soil and sediment remediation. Ettringite and minor gypsum were identified by XRD as primary phases in Al systems, whereas gypsum and ferrihydrite were the main products in Hg–Fe precipitates. Characterization of Hg–Al solids by bulk Hg EXAFS, electron microprobe, and microfocused-XRF mapping indicated coordination of Hg by Cl ligands, multiple Hg and Cl backscattering atoms, and concentration of Hg as small particles. Thermodynamic predictions agreed with experimental observations for bulk phases, but Hg speciation indicated lack of equilibration with the final solution. Results suggest physical encapsulation of Hg as a polynuclear chloromercury(II) salt in ettringite as the primary immobilization mechanism. In Hg–Fe solids, structural characterization indicated Hg coordination by O atoms only and Fe backscattering atoms that is consistent with inner-sphere complexation of Hg(OH)20 coprecipitated with ferrihydrite. Precipitation of ferrihydrite removed Hg from solution, but the resulting solid was sufficiently hydrated to allow equilibration of sorbed Hg species with the aqueous solution. Electron microprobe XRF characterization of sorption samples with low Hg concentration reacted with cement and FeSO4 amendment indicated correlation of Hg and Fe, supporting the interpretation of Hg removal by precipitation of an Fe(III) oxide phase. PMID:22594782

  5. Complexes with Hg(II) and macrocyclic ligands

    SciTech Connect

    Luis, S.V.; Frias, J.C.; Salvador, R.V.; Bolte, M.

    1999-04-01

    The crystal structures of 1,4,7,10,13,16-hexaoxa-cyclooctadecane dicyano mercury(II) monohydrate, C{sub 14}H{sub 24}HgN{sub 2}O{sub 6}{center{underscore}dot}H{sub 2}O, 1, and 2,5,8,11,18,21,24,27-octaoxa-tricyclo[26.4.0.0{sub 12,17}]-dotriconta-1(28),12,14,16,29,31-hexaene dicyano mercury(II) monohydrate, C{sub 26}H{sub 32}HgN{sub 2}O{sub 8}{center{underscore}dot}H{sub 2}O, 2, were determined: 1 crystallizes in the trigonal space group R{bar 3} with cell dimensions a = 11.7842(1) and c = 12.0316(1) {angstrom}. 2 crystallizes in the monoclinic space group P2{sub 1}/c with cell dimensions a = 11.156(3) {angstrom}, b = 8.417(2), c = 30.901(8) {angstrom}, and {beta} = 93.279{degree}. In spite of the different cyclic systems, similar complexes are formed where the Hg atom is coordinated by two CN groups and six oxygen atoms of the crown ether. The structure of 1 is isostructural with the crystal structures of 18C6-HgCl{sub 2}, 18C6-CdBr{sub 2}, 18C6-Sr(BH{sub 4}){sub 2}, and 18C6-Ba(BH{sub 4}){sub 2}. Furthermore, 1 is very similar to other 18C6-HgX{sub 2} complexes.

  6. Mercury Isotope Constraints on Depth of Methylation and Degree of Photo-Degradation of Methylmercury in the Central Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Blum, J. D.; Popp, B. N.; Johnson, M. W.; Drazen, J. C.; Choy, C. A.

    2012-12-01

    Mercury emissions from coal combustion are increasing globally and research is needed to better understand the consequences of increased deposition on Hg levels in fish caught in the open oceans. Central to this issue is understanding how and where Hg in the ocean is transformed from inorganic Hg(II) deposited from the atmosphere to monomethylmercury (MMHg), which is biomagnified in marine food webs. We measured Hg stable isotope values in nine species of pelagic fish caught in the Hawaiian Islands and we use Δ199Hg and δ202Hg as a monitor of the chemical pathways of MMHg prior to incorporation into the marine food web. We observe a decrease in Δ199Hg and δ202Hg and an increase in total Hg concentration of fish with mean depth of occurrence from the surface to 650 m. MMHg concentrations in the ocean are thought to largely represent a balance between rates of MMHg production by bacteria and degradation by photochemical reactions. Photochemical degradation of MMHg imparts a distinct Hg isotopic composition on the remaining MMHg and thus the isotopic composition of MMHg in fish can be used to estimate the proportion of MMHg that has been degraded. We interpret decreasing Δ199Hg values (5.3 permil to 1.3 permil) with increasing depth (25 m to 650 m) to indicate that MMHg in deep-feeding fish is formed at depth in the oxygen minimum zone. We suggest that MMHg advected upward into the photic zone undergoes extensive (~80%) photodegradation prior to entering the surface ocean food web. Although the Δ199Hg values at depth are much lower than at the surface, they are not zero. This suggests that some MMHg that was previously in the photic zone was transferred to depth and incorporated in the deeper ocean food web. The Δ199Hg value of 1.3 permil at 650 m depth could be explained by about 25% MMHg transported from the photic zone (Δ199Hg=5.3 permil) with 75% MMHg produced at depth (Δ199Hg=0 permil). At 100 m depth fish have Δ199Hg=2.8 permil, which is consistent

  7. Neurobehavioral effects, c-Fos/Jun expression and tissue distribution in rat offspring prenatally co-exposed to MeHg and PFOA: PFOA impairs Hg retention.

    PubMed

    Cheng, Jinping; Fujimura, Masatake; Zhao, Wenchang; Wang, Wenhua

    2013-05-01

    Exposure to methylmercury (MeHg) and perfluorooctanoic acid (PFOA) can occur simultaneously as both contaminants are found in the same food sources, especially fish, seafood, marine mammals and milk. The aim of this study was to assess the effects of exposure to MeHg (10 μg mL(-1) in drinking water) and PFOA (10 μg mL(-1) in drinking water) from gestational day 1 to postnatal day (PND) 21, alone and in combination, on neurobehavioral development and the expression of c-Fos/Jun in different brain regions in the offspring. Our findings showed that exposure to MeHg alone, and exposure to MeHg combined with PFOA significantly induced cliff avoidance reflexes and negative geotaxis reflexes. And these effects appeared to be greater following exposure to MeHg alone. MeHg and/or PFOA exposure did not significantly impair motor coordination functions, or cause significant changes in c-Fos expression in the hippocampus and cerebellum, and spatial learning tests were similar to those in the controls, thus it was impossible to determine whether combined exposure to MeHg and PFOA had any additional effects on both hippocampus and cerebellum regions. However, a significant increase in the frequency of line crossing was observed in rats treated with MeHg or PFOA alone, and there were no significant differences between the MeHg+PFOA-treated group and the controls, suggesting that PFOA was antagonistic to MeHg toxicity in the locomotor activity test. Co-exposure to MeHg and PFOA decreased all tissue Hg concentrations in pups compared to the group exposed to MeHg only, suggesting that PFOA impaired Hg retention in different tissues. PMID:23490179

  8. Beer Law Constants and Vapor Pressures of HgI2 over HgI2(s,l)

    NASA Technical Reports Server (NTRS)

    Su, Ching-Hua; Zhu, Shen; Ramachandran, N.; Burger, A.

    2002-01-01

    Optical absorption spectra of the vapor phase over HgI2(s,l) were measured at sample temperatures between 349 and 610 K for wavelengths between 200 and 600 nm. The spectra show the samples sublimed congruently into HGI2 without any observed Hg or I2 absorption spectra. The Beer's Law constants for 15 wavelengths between 200 and 440 nm were derived. From these constants the vapor pressure of HgI2, P, was found to be a function of temperature for the liquid and the solid beta-phases: ln P(atm) = -7700/T(K) + 12.462 (liquid phase) and ln P(atm) = -10150/T(K) + 17.026 (beta-phase). The expressions match the enthalpies of vaporization and sublimation of 15.30 and 20.17 kcal/mole respectively, for the liquid and the beta-phase HgI2. The difference in the enthalpies gives an enthalpy of fusion of 4.87 kcal/mole, and the intersection of the two expressions gives a melting point of 537 K.

  9. 46 CFR 53.05-1 - Safety valve requirements for steam boilers (modifies HG-400 and HG-401).

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... the ASME Boiler and Pressure Vessel Code (incorporated by reference; see 46 CFR 53.01-1) except as... 46 Shipping 2 2010-10-01 2010-10-01 false Safety valve requirements for steam boilers (modifies HG... (CONTINUED) MARINE ENGINEERING HEATING BOILERS Pressure Relieving Devices (Article 4) § 53.05-1 Safety...

  10. 46 CFR 53.05-1 - Safety valve requirements for steam boilers (modifies HG-400 and HG-401).

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... the ASME Boiler and Pressure Vessel Code (incorporated by reference; see 46 CFR 53.01-1) except as... 46 Shipping 2 2014-10-01 2014-10-01 false Safety valve requirements for steam boilers (modifies HG... (CONTINUED) MARINE ENGINEERING HEATING BOILERS Pressure Relieving Devices (Article 4) § 53.05-1 Safety...

  11. 46 CFR 53.05-1 - Safety valve requirements for steam boilers (modifies HG-400 and HG-401).

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... the ASME Boiler and Pressure Vessel Code (incorporated by reference; see 46 CFR 53.01-1) except as... 46 Shipping 2 2013-10-01 2013-10-01 false Safety valve requirements for steam boilers (modifies HG... (CONTINUED) MARINE ENGINEERING HEATING BOILERS Pressure Relieving Devices (Article 4) § 53.05-1 Safety...

  12. 46 CFR 53.05-1 - Safety valve requirements for steam boilers (modifies HG-400 and HG-401).

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... the ASME Boiler and Pressure Vessel Code (incorporated by reference; see 46 CFR 53.01-1) except as... 46 Shipping 2 2012-10-01 2012-10-01 false Safety valve requirements for steam boilers (modifies HG... (CONTINUED) MARINE ENGINEERING HEATING BOILERS Pressure Relieving Devices (Article 4) § 53.05-1 Safety...

  13. 46 CFR 53.05-1 - Safety valve requirements for steam boilers (modifies HG-400 and HG-401).

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... the ASME Boiler and Pressure Vessel Code (incorporated by reference; see 46 CFR 53.01-1) except as... 46 Shipping 2 2011-10-01 2011-10-01 false Safety valve requirements for steam boilers (modifies HG... (CONTINUED) MARINE ENGINEERING HEATING BOILERS Pressure Relieving Devices (Article 4) § 53.05-1 Safety...

  14. Synthesis and Crystal Structures of Hg 6Sb 5Br 7, Hg 6As 4BiCl 7, and Hg 6Sb 4BiBr 7, Built of a Polycationic Mercury-Pnictide Framework with Trapped Anions

    NASA Astrophysics Data System (ADS)

    Beck, Johannes; Hedderich, Sylvia; Neisel, Udo

    2000-11-01

    Hg6Sb5Br7, Hg6As4BiCl7, and Hg6Sb4BiBr7 were prepared from stoichiometric mixtures of Hg2X2, HgX2 (X=Cl, Br), As, Sb, and Bi in sealed, evacuated glass ampoules in temperature gradients 260→240°C for Hg6Sb5Br7, 340→320°C for Hg6As4BiCl7, and 290→270°C for Hg6Sb4BiBr7. All compounds crystallize in the cubic space group Paoverline3 with Z=4 and the lattice constants a=13.003(1) Å for Hg6Sb5Br7, a=12.178(2) Å for Hg6As4BiCl7, and a=12.998(4) Å for Hg6Sb4BiBr7. The structures have been solved based on single-crystal X-ray diffraction data and refined to R(F)=0.0431, 666 Fo for Hg6Sb5Br7, R(F)=0.0478, 690 Fo for Hg6As4BiCl7, and R(F)=0.0444, 840 Fo for Hg6Sb4BiBr7 with 30 parameters for each refinement. The structures are characterized by a three-dimensional polycationic framework of pnictide dumb-bells (As-As distance 2.43 Å, Sb-Sb distance 2.78 Å), each connected by six mercury atoms to six neighbored As2/Sb2 groups. There are two different cages in the framework; one type is occupied by nearly regular MX6 octahedra (M=Sb,Bi; X=Cl, Br), the other by halide ions. The three compounds crystallize closely related to Cd7P4Cl6, which contains a similar polycationic framework of P2 dumb-bells connected by Cd, but with only one type of cage occupied by octahedral [CdCl6]4- ions. The interactions between the atoms of the polycationic framework and the anions are very weak. The observed diamagnetism of all three compounds is in agreement with the ionic formulas (Hg6Sb4)4+[SbBr6]3-Br-, (Hg6As4)4+[BiCl6]3-Cl-, and (Hg6Sb4)4+[BiBr6]3-Br-.

  15. ISOTOPE CONVERSION DEVICE

    DOEpatents

    Wigner, E.P.; Young, G.J.; Ohlinger, L.A.

    1957-12-01

    This patent relates to nuclear reactors of tbe type utilizing a liquid fuel and designed to convert a non-thermally fissionable isotope to a thermally fissionable isotope by neutron absorption. A tank containing a reactive composition of a thermally fissionable isotope dispersed in a liquid moderator is disposed within an outer tank containing a slurry of a non-thermally fissionable isotope convertible to a thermally fissionable isotope by neutron absorption. A control rod is used to control the chain reaction in the reactive composition and means are provided for circulating and cooling the reactive composition and slurry in separate circuits.

  16. Isotopically controlled semiconductors

    SciTech Connect

    Haller, Eugene E.

    2001-12-21

    Semiconductor bulk crystals and multilayer structures with controlled isotopic composition have attracted much scientific and technical interest in the past few years. Isotopic composition affects a large number of physical properties, including phonon energies and lifetimes, bandgaps, the thermal conductivity and expansion coefficient and spin-related effects. Isotope superlattices are ideal media for self-diffusion studies. In combination with neutron transmutation doping, isotope control offers a novel approach to metal-insulator transition studies. Spintronics, quantum computing and nanoparticle science are emerging fields using isotope control.

  17. Hg bioavailability and impact on bacterial communities in a long-term polluted soil.

    PubMed

    Ruggiero, P; Terzano, R; Spagnuolo, M; Cavalca, L; Colombo, M; Andreoni, V; Rao, M A; Perucci, P; Monaci, E

    2011-01-01

    Different soil samples characterised by a long-term Hg-pollution were studied for Hg total content, fractionation, phytotoxicity and influence on the bacterial community. Hg pollution ranged from 1 to 50 mg kg(-1) and most of it was speciated in scarcely soluble forms. In agreement with this, the biochemical quality indexes were investigated (biomass, enzyme activities) and the bacterial community (viable heterotrophic (VH) bacteria, functional diversity) apparently was not influenced by the degree of Hg pollution. In particular, the investigated soils exhibited a low percentage of Hg-resistant (Hg(R)) bacteria ranging from less than 0.001% to 0.25% of the VH and the addition of available Hg in the form of HgCl(2) induced an enrichment of resistant Hg(R) populations. The general biodiversity of the bacterial community was evaluated by denaturing gradient gel electrophoresis of DNA of Hg spiked soil microcosms and of control soils. Hg(R) bacteria capable to grow in a minimal medium containing HgCl(2) were also isolated and identified. MerA and merB gene PCR fragments were obtained from different Hg(R) strains and the range of similarities at the DNA level and at the deduced amino acid level showed that they carried mercuric reductase and lyase. Differently from bacteria, some influence of soil Hg content on seeds' germination and root elongation was observed for Lepidium sativum L. and Solanum lycopersicum L. In conclusion, most of the Hg in these long-term polluted soils was scarcely mobile and available and did not significantly influence the soil bacterial community. The risk of potential Hg remobilization over time, that could be naturally favoured by the activity of plant roots or other inorganic processes occurring in soil, can be extenuated since bacterial community was resistant and resilient to subsequent Hg stress. PMID:21060931

  18. Determination of Mercury Content in a Shallow Firn Core from Summit, Greenland by Isotope Dilution Inductively Coupled Plasma Mass Spectrometry

    NASA Technical Reports Server (NTRS)

    Mann, Jacqueline L.; Long, Stephen E.; Shuman, Christopher A.; Kelly, W. Robert

    2003-01-01

    The total mercury Hg content was determined in 6 cm sections of a near-surface 7 m firn core and in surrounding surface snow from Summit, Greenland (elevation: 3238 m, 72.58 N, 38.53 W) in May 2001 by isotope dilution cold-vapor inductively coupled plasma mass spectrometry (ID-CV-ICP-MS). The focus of this research was to evaluate the capability of the ID-CV-ICPMS technique for measuring trace levels of Hg typical of polar snow and firn. Highly enriched Hg-201 isotopic spike is added to approximately 10 ml melted core and thoroughly mixed. The Hg(+2) in the sample is reduced on line with tin (II) chloride (SnCl2) and the elemental Hg (Hg(0)) vapor pre-concentrated on to gold gauze using a commercial amalgam system. The Hg is then thermally desorbed and introduced into a quadrupole ICP-MS. The blank corrected Hg concentrations determined for all samples ranged from 0.25 ng/L to 1.74 ng/L (ppt) (average 0.59 ng/L plus or minus 0.28 ng/L) and fall within the range of those previously determined by Boutron et al., 1998 (less than or equal to 0.05 ng/L to 2.0 ng/L) for the Summit site. The average blank value was 0.19 ng/L plus or minus 0.045 ng/L (n=6). The Hg values specifically for the firn core range from 0.25 ng/L to 0.87 ng/L (average 0.51 ng/L plus or minus 0.13 ng/L) and show both values declining with time and larger variability in concentration in the top 1.8 m.

  19. Hg2+ reduction and re-emission from simulated wet flue gas desulfurization liquors.

    PubMed

    Wo, Jingjing; Zhang, Meng; Cheng, Xiaoya; Zhong, Xiaohang; Xu, Jiang; Xu, Xinhua

    2009-12-30

    In this study, considering that Hg(2+) in wet flue gas desulfurization (FGD) systems can easily be reduced and then released into atmosphere, causing secondary pollution, the researches about Hg(2+) reduction and Hg(0) re-emission mechanism were carried out. The effects of several experimental parameters on the reduction were studied, including initial pH, temperature, and concentrations of Cl(-) and S(IV). Our experimental results indicated that Cl(-) had a restraining effect on the Hg(2+) reduction and Hg(0) re-emission, after 24h reaction, only 20.5% of Hg(2+) was reduced with 100mM Cl(-) in simulated desulfurization solution. Cl(-) can slow Hg(2+) reduction and Hg(0) re-emissions dramatically through changing reaction mechanism, with formation of new intermediate: ClHgSO(3)(-), which can decompose to Hg(0), but much more slowly than Hg(SO(3))(2)(2-) or HgSO(3). Simulating the conditions of the practical application (initial pH 5, T=50 degrees C, S(IV)=5 mM, Cl(-)=100 mM), we also found that Ca(2+), NO(3)(-), F(-), etc. all had obvious effects on reduction rates. Based on the material balance and characteristic of the reactants, the reduction emission mechanism of Hg(2+) has been established, providing theoretical basis for industrial application of mercury control in wet FGD systems. PMID:19699584

  20. Maternal-fetal distribution of mercury ( sup 203 Hg) released from dental amalgam fillings

    SciTech Connect

    Vimy, M.J.; Takahashi, Y.; Lorscheider, F.L. )

    1990-04-01

    In humans, the continuous release of Hg vapor from dental amalgam tooth restorations is markedly increased for prolonged periods after chewing. The present study establishes a time-course distribution for amalgam Hg in body tissues of adult and fetal sheep. Under general anesthesia, five pregnant ewes had twelve occlusal amalgam fillings containing radioactive 203Hg placed in teeth at 112 days gestation. Blood, amniotic fluid, feces, and urine specimens were collected at 1- to 3-day intervals for 16 days. From days 16-140 after amalgam placement (16-41 days for fetal lambs), tissue specimens were analyzed for radioactivity, and total Hg concentrations were calculated. Results demonstrate that Hg from dental amalgam will appear in maternal and fetal blood and amniotic fluid within 2 days after placement of amalgam tooth restorations. Excretion of some of this Hg will also commence within 2 days. All tissues examined displayed Hg accumulation. Highest concentrations of Hg from amalgam in the adult occurred in kidney and liver, whereas in the fetus the highest amalgam Hg concentrations appeared in liver and pituitary gland. The placenta progressively concentrated Hg as gestation advanced to term, and milk concentration of amalgam Hg postpartum provides a potential source of Hg exposure to the newborn. It is concluded that accumulation of amalgam Hg progresses in maternal and fetal tissues to a steady state with advancing gestation and is maintained. Dental amalgam usage as a tooth restorative material in pregnant women and children should be reconsidered.

  1. Mercury and stable isotope signatures in caged marine fish and fish feeds.

    PubMed

    Onsanit, Sarayut; Chen, Min; Ke, Caihuan; Wang, Wen-Xiong

    2012-02-15

    Total mercury (THg) and methylmercury (MeHg) concentrations were determined in four species of marine caged carnivorous fish, one species of herbivorous fish and three types of fish feeds (dried pellet feed, forage fish and fish viscera), collected from five cage sites in the rural areas along Fujian coastline, China. For the carnivorous fish, the concentrations of THg and MeHg ranged from 0.03 to 0.31 μg/g and from 0.02 to 0.30 μg/g on wet weight basis, respectively. The concentrations were lower for the herbivorous fish with both within the range of 0.01-0.03 μg/g. Out of the three tested fish feeds, tuna viscera contained the highest level of mercury (0.20 μg/g THg and 0.13 μg/g MeHg), with pellet feed containing the lowest level (0.05 μg/g THg and 0.01 μg/g MeHg). The calculated trophic transfer factor of MeHg was the highest (12-64) for fish fed on pellet feeds, and was the lowest for fish fed on tuna viscera. A significant relationship was found between Hg concentrations in caged fish and in fish feeds, thus Hg was primarily accumulated from the diet. Furthermore, the stable isotope δ(15)N was positively correlated with the Hg concentration in two caged sites, indicating that δ(15)N may be a suitable tool for tracking mercury in caged fish. We conclude that fish farming may be a good way of reducing the human exposure to Hg because mercury levels can be carefully controlled in such farming systems. PMID:22195524

  2. Design and synthesis of BODIPY-clickate based Hg(2+) sensors: the effect of triazole binding mode with Hg(2+) on signal transduction.

    PubMed

    Vedamalai, Mani; Kedaria, Dhaval; Vasita, Rajesh; Mori, Shigeki; Gupta, Iti

    2016-02-14

    BODIPY-clickates, F1 and F2, for the detection of Hg(2+) have been designed, synthesized and characterized. Both F1 and F2 showed hyperchromic shifts in the UV-visible spectra in response to increasing Hg(2+) concentrations. Hg(2+) ion binding caused perturbation of the emission quenching process and chelation induced enhanced bathochromic emission of F1 and F2 to 620 nm and 660 nm, respectively. Job's plot clearly indicated that the binding ratio of F1 and F2 with Hg(2+) was 1 : 1. The NMR titration of BODIPY-clickates with Hg(2+) confirmed that aromatic amines and triazoles were involved in the binding event. Furthermore, HRMS data of F1-Hg(2+) and F2-Hg(2+) supported the formation of mercury complexes of BODIPY-clickates. The dissociation constant for the interaction between fluorescent probes F1 and F2 with Hg(2+) was found to be 24.4 ± 5.1 μM and 22.0 ± 3.9 μM, respectively. The Hg(2+) ion induced fluorescence enhancement was almost stable in a pH range of 5 to 8. Having less toxicity to live cells, both the probes were successfully used to map the Hg(2+) ions in live A549 cells. PMID:26743311

  3. A high-performance Hg(+) trapped ion frequency standard

    NASA Technical Reports Server (NTRS)

    Prestage, J. D.; Tjoelker, R. L.; Dick, G. J.; Maleki, L.

    1992-01-01

    A high-performance frequency standard based on (199)Hg(+) ions confined in a hybrid radio frequency (RF)/dc linear ion trap is demonstrated. This trap permits storage of large numbers of ions with reduced susceptibility to the second-order Doppler effect caused by the RF confining fields. A 160-mHz-wide atomic resonance line for the 40.5-GHz clock transition is used to steer the output of a 5-mHz crystal oscillator to obtain a stability of 2 x 10(exp -15) for 24,000-second averaging times. Measurements with a 37-mHz line width for the Hg(+) clock transition demonstrate that the inherent stability for this frequency standard is better than 1 x 10(exp -15) at 10,000-second averaging times.

  4. Ultra-stable Hg(+) trapped ion frequency standard

    NASA Technical Reports Server (NTRS)

    Prestage, J. D.; Tjoelker, R. L.; Dick, G. J.; Maleki, L.

    1992-01-01

    We report the development of a fieldable frequency standard based on Hg-199(+) ions confined in a hybrid r.f./dc linear ion trap. This trap permits storage of large numbers of ions with reduced susceptibility to the second-order Doppler effect caused by the r.f. confining fields. A 160 mHz wide atomic resonance line for the 40.5 GHz clock transition is used to steer the output of a 5 MHz crystal oscillator to obtain a stability of 2 x 10 exp -15 for 24,000 s averaging times. For longer averaging intervals, measurements are limited by instabilities in available hydrogen maser frequency standards. Measurements with 37 mHz linewidth for the Hg(+) clock transition demonstrate that the inherent stability for this frequency standard is at least as good as 1 x 10 exp -15.

  5. Electrical Conductivity of HgTe at High Temperatures

    NASA Technical Reports Server (NTRS)

    Li, C.; Lehoczky, S. L.; Su, C.-H.; Scripa, R. N.

    2004-01-01

    The electrical conductivity of HgTe was measured using a rotating magnetic field method from 300 K to the melting point (943 K). A microscopic theory for electrical conduction was used to calculate the expected temperature dependence of the HgTe conductivity. A comparison between the measured and calculated conductivities was used to obtain the estimates of the temperature dependence of Gamma(sub 6)-Gamma(sub 8) energy gap from 300 K to 943 K. The estimated temperature coefficient for the energy gap was comparable to the previous results at lower temperatures (less than or equal to 300 K). A rapid increase in the conductivity just above 300 K and a subsequent decrease at 500 K is attributed to band crossover effects. This paper describes the experimental approach and some of the theoretical calculation details.

  6. Measurement of Linear Stark Interference in {sup 199}Hg

    SciTech Connect

    Loftus, T. H.; Swallows, M. D.; Griffith, W. C.; Romalis, M. V.; Heckel, B. R.; Fortson, E. N.

    2011-06-24

    We present measurements of Stark interference in the 6{sup 1}S{sub 0}{yields}6{sup 3}P{sub 1} transition in {sup 199}Hg, a process whereby a static electric field E mixes magnetic dipole and electric quadrupole couplings into an electric dipole transition, leading to E-linear energy shifts similar to those produced by a permanent atomic electric dipole moment (EDM). The measured interference amplitude, a{sub SI}=(a{sub M1}+a{sub E2})=(5.8{+-}1.5)x10{sup -9} (kV/cm){sup -1}, agrees with relativistic, many-body predictions and confirms that earlier central-field estimates are a factor of 10 too large. More importantly, this study validates the capability of the {sup 199}Hg EDM search apparatus to resolve nontrivial, controlled, and sub-nHz Larmor frequency shifts with EDM-like characteristics.

  7. Measurement of linear stark interference in 199Hg.

    PubMed

    Loftus, T H; Swallows, M D; Griffith, W C; Romalis, M V; Heckel, B R; Fortson, E N

    2011-06-24

    We present measurements of Stark interference in the (61)S(0)→6(3)P(1) transition in (199)Hg, a process whereby a static electric field E mixes magnetic dipole and electric quadrupole couplings into an electric dipole transition, leading to E-linear energy shifts similar to those produced by a permanent atomic electric dipole moment (EDM). The measured interference amplitude, a(SI) = (a(M1) + a(E2)) = (5.8 ± 1.5) × 10(-9) (kV / cm)(-1), agrees with relativistic, many-body predictions and confirms that earlier central-field estimates are a factor of 10 too large. More importantly, this study validates the capability of the (199)Hg EDM search apparatus to resolve nontrivial, controlled, and sub-nHz Larmor frequency shifts with EDM-like characteristics. PMID:21770639

  8. Measurement of Linear Stark Interference in Hg199

    NASA Astrophysics Data System (ADS)

    Loftus, T. H.; Swallows, M. D.; Griffith, W. C.; Romalis, M. V.; Heckel, B. R.; Fortson, E. N.

    2011-06-01

    We present measurements of Stark interference in the 6S01→6P13 transition in Hg199, a process whereby a static electric field E mixes magnetic dipole and electric quadrupole couplings into an electric dipole transition, leading to E-linear energy shifts similar to those produced by a permanent atomic electric dipole moment (EDM). The measured interference amplitude, aSI=(aM1+aE2)=(5.8±1.5)×10-9(kV/cm)-1, agrees with relativistic, many-body predictions and confirms that earlier central-field estimates are a factor of 10 too large. More importantly, this study validates the capability of the Hg199 EDM search apparatus to resolve nontrivial, controlled, and sub-nHz Larmor frequency shifts with EDM-like characteristics.

  9. Frequency Measurements of Al+ and Hg+ Optical Standards

    NASA Astrophysics Data System (ADS)

    Itano, W. M.; Bergquist, J. C.; Rosenband, T.; Wineland, D. J.; Hume, D.; Chou, C.-W.; Jefferts, S. R.; Heavner, T. P.; Parker, T. E.; Diddams, S. A.; Fortier, T. M.

    2010-02-01

    Frequency standards based on narrow optical transitions in 27Al+ and 199Hg+ ions have been developed at NIST. Both standards have absolute reproducibilities of a few parts in 1017. This is about an order of magnitude better than the fractional uncertainty of the SI second, which is based on the 133Cs hyperfine frequency. Use of femtosecond laser frequency combs makes it possible to compare the optical frequency standards to microwave frequency standards or to each other. The ratio of the Al+ and Hg+ frequencies can be measured more accurately than the reproducibility of the primary cesium frequency standards. Frequency measurements made over time can be used to set limits on the time variation of fundamental constants, such as the fine structure constant α or the quark masses.

  10. 40 CFR 75.38 - Standard missing data procedures for Hg CEMS.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... report the greater of the maximum expected Hg concentration (MEC) or 1.25 times the maximum controlled Hg concentration recorded in the previous 720 quality-assured monitor operating hours. The MEC shall be...

  11. On-line method of determining utilization factor in Hg-196 photochemical separation process

    DOEpatents

    Grossman, Mark W.; Moskowitz, Philip E.

    1992-01-01

    The present invention is directed to a method for determining the utilization factor [U] in a photochemical mercury enrichment process (.sup.196 Hg) by measuring relative .sup.196 Hg densities using absorption spectroscopy.

  12. Probing changes in Hg(II) coordination during its bacterial uptake

    NASA Astrophysics Data System (ADS)

    Thomas, Sara Anne; Ma, Qing; Gaillard, Jean-François

    2016-05-01

    We present XAFS data collected at the Hg LIII-edge for bacterial cells of Escherichia coli that have been exposed to 500 and 50 nano-molar Hg2+ in aqueous solution, which corresponds to ∼30 and ∼3μg Hg per g cells (wet weight). These concentrations are respectively 1 and 2 orders of magnitude lower than what has been previously reported for Hg-bacteria XAFS experiments. The cells were metabolically active while exposed to Hg(II), providing coordination information that can be directly compared to Hg(II) biouptake experiments. At these amounts of total dissolved metal, Hg(II) binds primarily to thiol moieties that are either present at the cell membrane or localized in the cytoplasm. We show that in this case the Hg binding environment is a mixture of 2- and 4-fold coordination to thiols. This information can be inferred from XANES spectra but the EXAFS provides a more quantitative answer.

  13. Measurement of mercury species in whole blood using speciated isotope dilution methodology integrated with microwave-enhanced solubilization and spike equilibration, headspace-solid-phase microextraction, and GC-ICP-MS analysis.

    PubMed

    Rahman, G M Mizanur; Wolle, Mesay Mulugeta; Fahrenholz, Timothy; Kingston, H M Skip; Pamuku, Matt

    2014-06-17

    A biomonitoring method was developed for the determination of inorganic-, methyl-, and ethylmercury (Hg(2+), CH3Hg(+), and C2H5Hg(+), respectively) in whole blood by triple-spiking speciated isotope dilution mass spectrometry (SIDMS) using headspace (HS) solid-phase microextraction (SPME) in combination with gas chromatographic (GC) separation and inductively coupled plasma mass spectrometric (ICP-MS) detection. After spiking the blood sample with isotopically enriched analogues of the analytes ((199)Hg(2+), CH3(200)Hg(+) and C2H5(201)Hg(+)), the endogenous Hg species were solubilized in 2.0 mol L(-1) HNO3 and equilibrated with the spikes using a microwave-enhanced protocol. The microwaved sample was treated with a 1% (w/v) aqueous solution of sodium tetrapropylborate (buffered to pH 5.2), and the propylated Hg species were sampled in the HS using a Carboxen/polydimethylsiloxane-coated SPME fiber. The extracted species were thermally desorbed from the fiber in the GC injection port and determined by GC-ICP-MS. The analytes were quantified, with simultaneous correction for their method-induced transformation, on the basis of the mathematical relationship in triple-spiking SIDMS. The method was validated using a bovine blood standard reference material (SRM 966, Level 2). Analysis of human blood samples demonstrated the accuracy and reproducibility of the method, which can detect the Hg species down to 30 pg g(-1) in blood. The validity of the analytical results found for the blood samples was demonstrated using mass balance by comparing the sum of the concentrations of the individual Hg species with the total Hg in the corresponding samples; the latter was determined by isotope dilution mass spectrometry (IDMS) after decomposing the blood using EPA Method 3052 with single-spiking. PMID:24845130

  14. Nuclear quadrupole interaction of 199mHg mercaptides

    NASA Astrophysics Data System (ADS)

    Butz, T.; Völkel, Th.; Nuyken, O.

    1991-01-01

    The strength and symmetry of the nuclear quadrupole interaction of the following 199mHg mercaptides were measured at room temperature by-γ-γ-perturbed angular correlations: dithiotreitol (DTT), benzylmercaptan (BEM), 1,3-dimercaptobenzene (DMB), glycoldimercaptoacetate (GDMA), and an oligomer synthesized from 1,3-dimercaptobenzene and norbornadiene, having an average number of repeating units of seven and mercapto end groups (dimercaptotelechel:TEL7). The data suggest an almost linear SHgS bond in all cases.

  15. Two-photon absorption in Hg 2Cl 2 crystals

    NASA Astrophysics Data System (ADS)

    Pelant, I.; Ambrož, M.; Hála, J.; Kohlová, V.; Barta, Č.

    1985-01-01

    Violet luminescence (396 nm) of Hg 2Cl 2 single crystals was observed under excitation of green light (∼ 500 nm) of a pulsed dye laser at liquid helium temperature. The effect is interpreted as due to the two-photon absorption process. The two-photon excitation spectrum of the luminescence was measured in the wavelength range 475-530 nm. Possible mechanisms of the two-photon transition are outlined.

  16. Lifetime measurements in the superdeformed band of sup 192 Hg

    SciTech Connect

    Moore, E.F.; Janssens, R.V.F.; Ahmad, I.; Carpenter, M.P.; Fernandez, P.B.; Khoo, T.L.; Ridley, S.L.; Wolfs, F.L.H. ); Ye, D.; Beard, K.B.; Garg, U. ); Drigert, M.W. ); Benet, P.; Daly, P.J. ); Wyss, R. Royal Institute of Technology, S-10444 Stockholm ); Nazarewicz, W. )

    1990-06-25

    Lifetimes were measured for transitions in the superdeformed band of {sup 192}Hg with the Doppler-shift attenuation method. The results yield an essentially constant quadrupole moment of 20{plus minus}2 {ital e} b and indicate that the sidefeeding lifetimes are of the same order as the state lifetimes. The data are consistent with calculations using the cranked Woods-Saxon Strutinsky method with pairing.

  17. A vareity of Hg capture solutions are available

    SciTech Connect

    Blankinship, S.

    2009-06-15

    While vacating the Clean Air Mercury Rule (CAMR) has postponed implementation of capturing mercury emitted by coal-fired power plants improvements in ways to capture and monitor mercury have continued. One method of enhancing Hg capture from FGD and SCR is to treat the coal by adding a halogen, such as calcium bromide in Alstom's KNX process prior to combustion. Power plants without FGD usually use sorbent injection, mostly an activated carbon, upstream of a particulate control device. 1 fig.

  18. Optical properties of Hg(1-x)Cd(x)Te

    NASA Astrophysics Data System (ADS)

    Tong, Fei-Ming; Ravindra, N. M.

    1993-04-01

    Optical properties of Hg(1-x)Cd(x)Te are summarized. Based on Penn-type (1962) models, the Moss (1950) relation, and the Wemple and DiDomenico (1971) approach, calculations of energy gap, plasmon energy, Fermi energy, oscillator strength and electronic polarizability have been made. Comparisons are made with the data available in the literature. Details of the dependency of the properties on composition are presented.

  19. An aqueous fluorescent probe for Hg(2+) detection with high selectivity and sensitivity.

    PubMed

    Fang, Qian; Liu, Qian; Song, Xiangzhi; Kang, Jian

    2015-12-01

    An aqueous fluorescent probe, 1, was developed for the rapid detection of Hg(2+) with high sensitivity and excellent selectivity. Upon the addition of Hg(2+) in pure aqueous media, the Hg(2+)-mediated hydrolysis of vinyl ether and subsequent cyclization reactions converted probe 1 into the corresponding iminocoumarin dye, which is strongly fluorescent when excited. The application of this probe for the detection of intracellular Hg(2+) was successfully demonstrated in living cells. PMID:25761896

  20. HgCdTe APDs for free space optical communications

    NASA Astrophysics Data System (ADS)

    Rothman, J.; Lasfargues, G.; Abergel, J.

    2015-10-01

    HgCdTe avalanche photodiode single element detectors have been developed for a large scope of photon starved applications. The present communication is dedicated to use of these detectors for free space optical communications. In this perspective we present and discuss the sensitivity and bandwidth that has been measured directly on HgCdTe APDs and on detector modules. In particular, we report on the performance of TEC cooled large area detectors with sensitive diameters ranging from 30- 200 μm, characterised by detector gains of 2- 20 V/μW and noise equivalent input power of 0.1-1 nW for bandwidths ranging from 20 to 400 MHz. One of these detectors has been used during the lunar laser communication demonstration (LLCD) and the results The perspectives for high data rate transmission is estimated from the results of impulse response measurements on HgCdTe APDs. These results indicate that bandwidths close to 10 GHz can be achieved in these devices. The associated sensitivity at an APD gain of 100 is estimated to be below 4 photons rms (NEP<10 nW) for APDs operated at 300 K.

  1. HgCdTe 256x256 NWIR FPA

    NASA Technical Reports Server (NTRS)

    Vural, Kadri; Blessinger, Michael; Chen, Jenkon; Kleinhans, William

    1989-01-01

    Researchers developed a HgCdTe 256x256 focal plane array (FPA) which operates in the 1 to 5 micron band. This is presently the largest demonstrated HgCdTe FPA. The detector material is HgCdTe on sapphire (PACE-1 technology) which has a low thermal expansion mismatch with silicon. The multiplexer is a CMOS FET-switch device processed through a commercial silicon foundry. The multiplexer input is direct injection and the charge capacity is about 2 times 10 to the 7th power electrons. The kTC limited read noise is 400 electrons. Researchers demonstrated high background imaging using the device. The broadband quantum efficiency is measured to be 59 percent. Dark currents less than 0.1 pA were measured at 77 K for detectors processed on PACE-1 material with 4.9 microns cutoff. The dark currents decrease as the temperature is lowered, and researchers are presently studying the T less than 77 K characteristics. The interconnect yield is greater than 95 percent. The devices are available for astronomical applications.

  2. First Measurement of Several β-Delayed Neutron Emitting Isotopes Beyond N=126.

    PubMed

    Caballero-Folch, R; Domingo-Pardo, C; Agramunt, J; Algora, A; Ameil, F; Arcones, A; Ayyad, Y; Benlliure, J; Borzov, I N; Bowry, M; Calviño, F; Cano-Ott, D; Cortés, G; Davinson, T; Dillmann, I; Estrade, A; Evdokimov, A; Faestermann, T; Farinon, F; Galaviz, D; García, A R; Geissel, H; Gelletly, W; Gernhäuser, R; Gómez-Hornillos, M B; Guerrero, C; Heil, M; Hinke, C; Knöbel, R; Kojouharov, I; Kurcewicz, J; Kurz, N; Litvinov, Yu A; Maier, L; Marganiec, J; Marketin, T; Marta, M; Martínez, T; Martínez-Pinedo, G; Montes, F; Mukha, I; Napoli, D R; Nociforo, C; Paradela, C; Pietri, S; Podolyák, Zs; Prochazka, A; Rice, S; Riego, A; Rubio, B; Schaffner, H; Scheidenberger, Ch; Smith, K; Sokol, E; Steiger, K; Sun, B; Taín, J L; Takechi, M; Testov, D; Weick, H; Wilson, E; Winfield, J S; Wood, R; Woods, P; Yeremin, A

    2016-07-01

    The β-delayed neutron emission probabilities of neutron rich Hg and Tl nuclei have been measured together with β-decay half-lives for 20 isotopes of Au, Hg, Tl, Pb, and Bi in the mass region N≳126. These are the heaviest species where neutron emission has been observed so far. These measurements provide key information to evaluate the performance of nuclear microscopic and phenomenological models in reproducing the high-energy part of the β-decay strength distribution. This provides important constraints on global theoretical models currently used in r-process nucleosynthesis. PMID:27419564

  3. First Measurement of Several β -Delayed Neutron Emitting Isotopes Beyond N =126

    NASA Astrophysics Data System (ADS)

    Caballero-Folch, R.; Domingo-Pardo, C.; Agramunt, J.; Algora, A.; Ameil, F.; Arcones, A.; Ayyad, Y.; Benlliure, J.; Borzov, I. N.; Bowry, M.; Calviño, F.; Cano-Ott, D.; Cortés, G.; Davinson, T.; Dillmann, I.; Estrade, A.; Evdokimov, A.; Faestermann, T.; Farinon, F.; Galaviz, D.; García, A. R.; Geissel, H.; Gelletly, W.; Gernhäuser, R.; Gómez-Hornillos, M. B.; Guerrero, C.; Heil, M.; Hinke, C.; Knöbel, R.; Kojouharov, I.; Kurcewicz, J.; Kurz, N.; Litvinov, Yu. A.; Maier, L.; Marganiec, J.; Marketin, T.; Marta, M.; Martínez, T.; Martínez-Pinedo, G.; Montes, F.; Mukha, I.; Napoli, D. R.; Nociforo, C.; Paradela, C.; Pietri, S.; Podolyák, Zs.; Prochazka, A.; Rice, S.; Riego, A.; Rubio, B.; Schaffner, H.; Scheidenberger, Ch.; Smith, K.; Sokol, E.; Steiger, K.; Sun, B.; Taín, J. L.; Takechi, M.; Testov, D.; Weick, H.; Wilson, E.; Winfield, J. S.; Wood, R.; Woods, P.; Yeremin, A.

    2016-07-01

    The β -delayed neutron emission probabilities of neutron rich Hg and Tl nuclei have been measured together with β -decay half-lives for 20 isotopes of Au, Hg, Tl, Pb, and Bi in the mass region N ≳126 . These are the heaviest species where neutron emission has been observed so far. These measurements provide key information to evaluate the performance of nuclear microscopic and phenomenological models in reproducing the high-energy part of the β -decay strength distribution. This provides important constraints on global theoretical models currently used in r -process nucleosynthesis.

  4. Hg-loss compensation and wiping-off of source liquid on slider liquid phase epitaxy of Hg 1- xCd xTe

    NASA Astrophysics Data System (ADS)

    Shinohara, Motoya; Nugraha; Noda, Yasutoshi; Furukawa, Yoshitaka

    1994-08-01

    Hg loss measurement and wiping the liquid source on Hg 1- xCd xTe (MCT) layer growth were performed using a slider liquid phase epitaxy (LPE) boat with a HgTe reservoir. The optimum conditions to compensate Hg loss were revealed, where an increased amount of HgTe in the reservoir was effective to stabilize the weight change of source liquid due to Hg evaporation. The wiping was effectively made on equilibrium cooling from the melting point, where thin MCT layers (2-4 μm) resulted and the surface was slightly terraced. Thick layers (30-40 μm) resulted from the supercooling and step cooling with a supercooling of 15 K. The composition of the grown layers was x = 0.25-0.42.

  5. New data on cross-sections of deuteron induced nuclear reactions on gold up to 50 MeV and comparison of production routes of medically relevant Au and Hg radioisotopes

    NASA Astrophysics Data System (ADS)

    Tárkányi, F.; Hermanne, A.; Ditrói, F.; Takács, S.; Adam Rebeles, R.; Ignatyuk, A. V.

    2015-11-01

    Investigations of cross-sections of deuteron induced nuclear reactions on gold were extended up to 50 MeV by using the standard stacked foil irradiation technique and high resolution gamma-ray spectrometry. New cross-sections are reported for the 197Au(d,xn)197m,197g,195m,195g,193m,193gHg and 197Au(d,x)198m,198g,196m,196g,195,194Au nuclear reactions. The application for production of the medically relevant isotopes 198Au and 195m,195g,197m,197gHg is discussed, including the comparison with other charged particle induced production routes. The possible use of the 197Au(d,x)197m,197g,195m,193mHg and 196m,196gAu reactions for monitoring deuteron beam parameters is also investigated.

  6. IUPAC Project: Terminology and definition of quantities related to the isotope distribution in elements with more than two stable isotopes

    NASA Astrophysics Data System (ADS)

    Kaiser, J.; Angert, A.; Bergquist, B.; Brand, W.; Ono, S.; Röckmann, T.; Savarino, J.

    2012-04-01

    The objective of IUPAC Project 2009-046-2-200 (http://www.iupac.org/web/ins/2009-046-2-200) is to define terminology and to identify the most suitable definitions of quantities that characterise the isotope distribution in elements with more than two stable isotopes, including so-called mass-independent fractionation, non-mass dependent fractionation, isotope anomaly, 17O excess, etc. Most atmospheric oxygen-bearing species show deviations in their triple oxygen isotope ratios from mass-dependent fractionation (MDF) relationships predicted by the theories of Urey, Bigeleisen and Mayer. Similar deviations have also been found in sulphur and other elements with more than two stables isotopes (e.g. Hg, Cd, Zn), often preserved in non-atmospheric reservoirs, including rocks, minerals, soils, ice and waters. Despite the ubiquity of this type of isotope anomaly, there has never been an attempt to clearly define the terminology and physical quantities used to measure these anomalies and the processes that lead to their formation. Terms like mass-independent fractionation, non-mass dependent fractionation, isotope anomaly, isotope excess etc. have been used in the historic and recent literature, but are often not carefully distinguished. The realisation that MDF comprises a range of possible relationships between the isotopes of one element led to further complications because it meant that apparent isotope anomalies could be created by a combination of different MDF processes. At the moment, at least four different definitions to quantify isotope anomalies are being used. Furthermore, coefficients used in these definitions vary, which makes the comparison of data from different sources very difficult, even for experts. A consistent set of recommendations on how to express and quantify the isotope distribution in elements with more than two stable isotopes is highly warranted. From our experience as academic teachers, we are woefully aware how impenetrable the field is for

  7. Characteristics of Hg-resistant bacteria isolated from Minamata Bay sediment

    SciTech Connect

    Nakamura, K.; Fujisaki, T.; Tamashiro, H.

    1986-06-01

    Seventy-two strains of Hg-resistant bacteria (Pseudomonas) were isolated on agar plates containing 40 micrograms/ml of HgCl2 from Minamata Bay sediment, which was heavily polluted with mercury (45.8 micrograms/g). The minimal inhibitory concentrations (MICs) of mercurial compounds were determined for the Hg-resistant pseudomonads and 65 strains (Pseudomonas sp., Bacillus sp., Vibrio sp., and Corynebacterium sp.) isolated from Sendai Bay sediment (1 microgram/g of mercury) as control. The MICs to HgCl/sub 2/, CH/sub 3/HgCl, C/sub 2/H/sub 5/HgCl, C/sub 3/H/sub 7/HgCl, and C/sub 6/H/sub 5/HgOCOCH/sub 3/ for the Hg-resistant pseudomonads from Minamata Bay were significantly higher than those of strains from Sendai Bay. The volatilization from liquid culture containing 20 micrograms/ml of HgCl2 was observed in all of the Hg-resistant pseudomonads from Minamata Bay (70 strains). The mean loss of mercury from liquid culture was 60.4 +/- 17.3%. Further study is warranted to determine what role the Hg-resistant bacteria, particularly the Pseudomonas species, play in the mercury cycle in Minamata Bay.

  8. 48 CFR 752.231-71 - Salary supplements for HG employees.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 48 Federal Acquisition Regulations System 5 2010-10-01 2010-10-01 false Salary supplements for HG....231-71 Salary supplements for HG employees. As prescribed in 731.205-71, for use in all contracts with a possible need or services of a HG employee. The clause should also be inserted in all...

  9. Solving mercury (Hg) speciation in soil samples by synchrotron X-ray microspectroscopic techniques.

    PubMed

    Terzano, Roberto; Santoro, Anna; Spagnuolo, Matteo; Vekemans, Bart; Medici, Luca; Janssens, Koen; Göttlicher, Jörg; Denecke, Melissa A; Mangold, Stefan; Ruggiero, Pacifico

    2010-08-01

    Direct mercury (Hg) speciation was assessed for soil samples with a Hg concentration ranging from 7 up to 240 mg kg(-1). Hg chemical forms were identified and quantified by sequential extractions and bulk- and micro-analytical techniques exploiting synchrotron generated X-rays. In particular, microspectroscopic techniques such as mu-XRF, mu-XRD and mu-XANES were necessary to solve bulk Hg speciation, in both soil fractions <2 mm and <2 microm. The main Hg-species found in the soil samples were metacinnabar (beta-HgS), cinnabar (alpha-HgS), corderoite (Hg(3)S(2)Cl(2)), and an amorphous phase containing Hg bound to chlorine and sulfur. The amount of metacinnabar and amorphous phases increased in the fraction <2 microm. No interaction among Hg-species and soil components was observed. All the observed Hg-species originated from the slow weathering of an inert Hg-containing waste material (K106, U.S. EPA) dumped in the area several years ago, which is changing into a relatively more dangerous source of pollution. PMID:20605298

  10. A Hg 2+-selective chemodosimeter based on desulfurization of coumarin thiosemicarbazide in aqueous media

    NASA Astrophysics Data System (ADS)

    Ma, Wenhui; Xu, Qun; Du, Jianjun; Song, Bo; Peng, Xiaojun; Wang, Zhuo; Li, Guodong; Wang, Xifang

    2010-07-01

    A fluorescence-enhanced chemodosimeter 1 based on coumarin thiosemicarbazide for Hg 2+ was developed via a Hg 2+-induced desulfurization reaction. Spectroscopic results reveal that chemodosimeter 1 exhibits high sensitivity and selectivity for Hg 2+ in comparison to common interfering metal ions in aqueous media at room temperature.

  11. STATUS OF EPA/DOE MOU TECHNICAL WORKGROUP ACTIVITIES: HG WASTE TREATMENT

    EPA Science Inventory

    EPA's Land Disposal Restrictions program currently has technology-specific treatment standards for hazardous wastes containing greater than or equal to 260ppm total mercury (Hg) (i.e., high Hg subcategory wastes). The treatment standards specify RMERC for high Hg subcategory wast...

  12. Phytoextraction of HG by parsley (Petroselinum crispum) and its growth responses.

    PubMed

    Bibi, Asma; Farooq, Umar; Naz, Sadia; Khan, Afsar; Khan, Sara; Sarwar, Rizwana; Mahmood, Qaisar; Alam, Arif; Mirza, Nosheen

    2016-01-01

    The effect of mercury (Hg) on the growth and survival of parsley (Petroselinum crispum) was explored at various treatments. The plants were grown in pots having Hoagland's solution to which various Hg treatments were applied and placed under greenhouse conditions. The treatments were: no metal applied (control) and six doses of Hg as mercuric chloride for 15 days. Linear trend of Hg accumulation was noted in roots, stems, and leaves with increasing Hg treatments. The maximum Hg concentration in root, stem and leaf was 8.92, 8.27, and 7.88 at Hg treatments of 25 mg l(-1), respectively. On the whole, Hg accumulation in different plant parts was in the following order: leaves > stem > roots. Linear trend was also observed for Bioaccumulation Factor (BF) and Translocation Factor (TF) with increasing Hg concentrations in the growth medium. The highest respective BFHg and TFHg values were 9.32 and 2.02 for the Hg treatments of 25 and 50 mg l(-1). In spite of the reduced growth in the presence of Hg, the plant has phytoremediation potential. It is recommended that parsley should not be cultivated in Hg contaminated sites in order to avoid dietary toxicity. PMID:26514060

  13. Impacts of forest harvesting on mobilization of Hg and MeHg in drained peatland forests on black schist or felsic bedrock.

    PubMed

    Ukonmaanaho, Liisa; Starr, Mike; Kantola, Marjatta; Laurén, Ari; Piispanen, Juha; Pietilä, Heidi; Perämäki, Paavo; Merilä, Päivi; Fritze, Hannu; Tuomivirta, Tero; Heikkinen, Juha; Mäkinen, Jari; Nieminen, Tiina M

    2016-04-01

    Forest harvesting, especially when intensified harvesting method as whole-tree harvesting with stump lifting (WTHs) are used, may increase mercury (Hg) and methylmercury (MeHg) leaching to recipient water courses. The effect can be enhanced if the underlying bedrock and overburden soil contain Hg. The impact of stem-only harvesting (SOH) and WTHs on the concentrations of Hg and MeHg as well as several other variables in the ditch water was studied using a paired catchment approach in eight drained peatland-dominated catchments in Finland (2008-2012). Four of the catchments were on felsic bedrock and four on black schist bedrock containing heavy metals. Although both Hg and MeHg concentrations increased after harvesting in all treated sites according to the randomized intervention analyses (RIAs), there was only a weak indication of a harvest-induced mobilization of Hg and MeHg into the ditches. Furthermore, no clear differences between WTHs and SOH were found, although MeHg showed a nearly significant difference (p = 0.06) between the harvesting regimes. However, there was a clear bedrock effect, since the MeHg concentrations in the ditch water were higher at catchments on black schist than at those on felsic bedrock. The pH, suspended solid matter (SSM), dissolved organic carbon (DOC), and iron (Fe) concentrations increased after harvest while the sulfate (SO4-S) concentration decreased. The highest abundances of sulfate-reducing bacteria (SRB) were found on the sites with high MeHg concentrations. The biggest changes in ditch water concentrations occurred first 2 years after harvesting. PMID:26979172

  14. Experimental evidence for the third level (А+) of Hg vacancy in Hg1-xCdxTe

    NASA Astrophysics Data System (ADS)

    Shepelskii, G. A.; Strikha, M. V.; Gassan-zade, S. G.

    2012-11-01

    Mercury vacancy in Hg1-xCdxTe is not a two-level (as it was supposed until now), but a three-level acceptor. A third, most shallow (1-1.5 meV) level (А+ state) appears due to a capture of a third hole by a neutral acceptor, after the two deeper vacancy levels (A- and А0 states) are already occupied by holes. Due to a capture of nonequilibrium holes by neutral mercury vacancies (under radiation) a positive space charge region arises near an irradiated surface. This causes the anomalies of photoelectromagnetic effect, observed in р-Hg1-xCdxTe at T < 10-12 K.

  15. Hybrid isotope separation scheme

    DOEpatents

    Maya, Jakob

    1991-01-01

    A method of yielding selectively a desired enrichment in a specific isotope including the steps of inputting into a spinning chamber a gas from which a scavenger, radiating the gas with a wave length or frequency characteristic of the absorption of a particular isotope of the atomic or molecular gas, thereby inducing a photochemical reaction between the scavenger, and collecting the specific isotope-containing chemical by using a recombination surface or by a scooping apparatus.

  16. HYDROGEN ISOTOPE TARGETS

    DOEpatents

    Ashley, R.W.

    1958-08-12

    The design of targets for use in the investigation of nuclear reactions of hydrogen isotopes by bombardment with accelerated particles is described. The target con struction eomprises a backing disc of a metal selected from the group consisting of molybdenunn and tungsten, a eoating of condensed titaniunn on the dise, and a hydrogen isotope selected from the group consisting of deuterium and tritium absorbed in the coatiag. The proeess for preparing these hydrogen isotope targets is described.

  17. Hybrid isotope separation scheme

    DOEpatents

    Maya, J.

    1991-06-18

    A method is described for yielding selectively a desired enrichment in a specific isotope including the steps of inputting into a spinning chamber a gas from which a scavenger, radiating the gas with a wave length or frequency characteristic of the absorption of a particular isotope of the atomic or molecular gas, thereby inducing a photochemical reaction between the scavenger, and collecting the specific isotope-containing chemical by using a recombination surface or by a scooping apparatus. 2 figures.

  18. Mercury methylation and demethylation in Hg-contaminated lagoon sediments (Marano and Grado Lagoon, Italy)

    NASA Astrophysics Data System (ADS)

    Hines, Mark E.; Poitras, Erin N.; Covelli, Stefano; Faganeli, Jadran; Emili, Andrea; Žižek, Suzana; Horvat, Milena

    2012-11-01

    Mercury (Hg) transformation activities and sulfate (SO42-) reduction were studied in sediments of the Marano and Grado Lagoons in the Northern Adriatic Sea region as part of the "MIRACLE" project. The lagoons, which are sites of clam (Tapes philippinarum) farming, have been receiving excess Hg from the Isonzo River for centuries. Marano Lagoon is also contaminated from a chlor-alkali plant. Radiotracer methods were used to measure mercury methylation (230Hg, 197Hg), methylmercury (MeHg) demethylation (14C-MeHg) and SO42- reduction (35S) in sediment cores collected in autumn, winter and summer. Mercury methylation rate constants ranged from near zero to 0.054 day-1, generally decreased with depth, and were highest in summer. Demethylation rate constants were much higher than methylation reaching values of ˜0.6 day-1 in summer. Demethylation occurred via the oxidative pathway, except in winter when the reductive pathway increased in importance in surficial sediments. Sulfate reduction was also most active in summer (up to 1600 nmol mL-1 day-1) and depth profiles reflected seasonally changing redox conditions near the surface. Methylation and demethylation rate constants correlated positively with SO42- reduction and pore-water Hg concentrations, and inversely with Hg sediment-water partition coefficients indicating the importance of SO42- reduction and Hg dissolution on Hg cycling. Hg transformation rates were calculated using rate constants and concentrations of Hg species. In laboratory experiments, methylation was inhibited by amendments of the SO42--reduction inhibitor molybdate and by nitrate. Lagoon sediments displayed a dynamic seasonal cycle in which Hg dissolution in spring/summer stimulated Hg methylation, which was followed by a net loss of MeHg in autumn from demethylation. Sulfate-reducing bacteria (SRB) tended to be responsible for methylation of Hg and the oxidative demethylation of MeHg. However, during winter in surficial sediments, iron

  19. Dimercaptopropane Sulfonate Chelation Affects In Vivo Hg and MeHg Distribution in Tissues and Urine of Prairie Voles (Microtus ochrogaster).

    PubMed

    Cobb, G P; Moore, A W; Rummel, K T; McMurry, S T

    2015-12-01

    Methyl mercury cation (MeHg(+)) and divalent mercury (Hg(2+)) were quantified in urine, liver, kidney, and brain of prairie voles (Microtus ochrogaster) during a 12 week exposure to aqueous MeHg(+) at concentrations of 10, 100, and 1000 ng MeHg(+)/mL. Aqueous MeHg(+) exposures increased mercury accumulation in tissues of voles from each exposure group. Accumulation was greater within the higher two exposure groups. Similar [Hg(2+)] and [MeHg(+)] were determined within a given organ type before and after 2,3-dimercapto-1-propane sulfonate (DMPS) chelation. Similar correlations were seen for Hg(2+) and MeHg(+) concentrations in pre and post chelation urine. Post chelation urine more reliably predicted mercury species concentrations in tissues than did urine collected before chelation. These data demonstrate the utility of DMPS in noninvasive assessment of wildlife exposure to mercury, which may have utility in evaluating meta-population level exposure to hazardous wastes. PMID:26412077

  20. Phase transitions involving vacancy ordering in two metal mercuric iodides, Ag2HgI4 and Cu2HgI4

    NASA Astrophysics Data System (ADS)

    Lumsden, Mark; Steinitz, Michael; McAlduff, E. J.

    1995-06-01

    We have investigated the thermochromic order-disorder phase transitions in two superionic conducting compounds, Ag2HgI4 and Cu2HgI4, using capacitance dilatometry to determine the relative volume change, ΔV/V, at the transitions. We find an average ΔV/V of 9.6×10-3 for Ag2HgI4 at a transition temperature of 48.75 °C and an average ΔV/V of 4.0×10-3 for Cu2HgI4 at a transition temperature of 63 °C.

  1. Supramolecular aggregation of Ni(salen) with (C6F5)2Hg and [o-C6F4Hg]3.

    PubMed

    Tsunoda, Mitsukimi; Fleischmann, Martin; Jones, J Stuart; Bhuvanesh, Nattamai; Scheer, Manfred; Gabbaï, François P

    2016-03-15

    As part of our ongoing interest in the supramolecular chemistry of fluorinated organomercurials, we have investigated the interaction of bis(pentafluorophenyl)mercury ((C6F5)2Hg), and trimeric (perfluoro-o-phenylene)mercury ([o-C6F4Hg]3), with nickel(ii) N,N'-bis(salicylidene)ethylenediamine) (Ni(salen)). While solution studies monitored by UV-VIS spectroscopy suggest that Ni(salen) interacts with the trinuclear mercury complex in solution, the 1 : 1 adduct (Ni(salen)-(C6F5)2Hg) and the 1 : 1 adducts Ni(salen)-[o-C6F4Hg]3 and [Ni(salen)-[o-C6F4Hg]3-THF-H2O] can be obtained by slow evaporation of solutions containing the two building blocks. While arene-fluoroarene and hydrogen bonding interactions, as well as interactions between mercury and the salen ligand are the predominant forces responsible for the formation of these adducts, Ni(salen)-[o-C6F4Hg]3 and [Ni(salen)-[o-C6F4Hg]3-THF-H2O] also display short Ni-Hg separations consistent with the presence of metallophilic interactions. Quantum theory of atoms in molecules (QTAIM) analyses of the Ni-Hg interactions in these adducts finds that these interactions are dominated by electrostatic and dispersion forces, despite featuring non-negligible covalent contributions. PMID:26865181

  2. Hydrogen-Te antisite complex impurity (H-TeHg) in Hg0.75Cd0.25Te: First-principles study

    NASA Astrophysics Data System (ADS)

    Xue, L.; Zhou, P.; Zhang, C. X.; Sun, L. Z.; Zhong, Jianxin

    2013-08-01

    Using first-principles method within the framework of the density functional theory, we study the formation energies and the binding energies of hydrogen-telluride antisite complex impurities (n H-TeHg, n=1,2) in Hg0.75Cd0.25Te. We find that telluride antisite impurity (TeHg) in Hg0.75Cd0.25Te is a double donor. When Te antisite and an interstitial hydrogen move close to each other, the interaction between them leads to the creation of a stable 1H-TeHg complex with a binding energy of 0.33 eV. In this case, the donor effects induced by Te antisite are partially passivated. As the hydrogen concentration increases, the binding energy of the 2H-TeHg forming from combining H-TeHg with interstitial hydrogen is only 0.005 eV. Namely, 2H-TeHg is unstable in Hg0.75Cd0.25Te and hydrogenation cannot fully neutralize Te antisite defects.

  3. Evidence for Multiple Export Pathways of Mercury from the Inoperative New Idria Hg Mine, CA

    NASA Astrophysics Data System (ADS)

    Jew, A. D.; Luong, P. N.; Kim, C. S.; Rytuba, J. J.; Gustin, M. S.; Brown, G. E.

    2009-12-01

    Understanding mercury transport from inoperative Hg mines is important for California because of the presence of nearly 2,000 abandoned Hg mines in the California Coast Range. Since its closure in 1972, the New Idria Hg mine has developed an extensive acid mine drainage (AMD) system (pH 3) that drains into the San Carlos Creek (pH 9) about 100m downstream of a mine tailings pile. Sediment samples along the AMD system were analyzed using synchrotron radiation-based X-ray fluorescence (XRF), μ-X-ray absorption near edge structure (μ-XANES) spectroscopy, extended X-ray absorption fine structure (EXAFS) spectroscopy, and sequential chemical extractions (SCE). It was determined by XRF mapping that Hg within the AMD settling pond sediments occurs mostly as colloids ranging in size from 1-10 μm. Hg speciation of the colloids, determined by μ-XANES and EXAFS, consisted of 80% α-HgS and 20% β-HgS. SCE analysis of sediments along the entire AMD system resulted in the HgS fraction comprising >95% of the total Hg, suggesting minor Hg adsorption. Even though liquid Hg(0) can be panned in the stream it was not detected by SCE, suggesting that liquid Hg(0) settles into deeper portions of the sediments than were sampled. Mercury volatilization to the atmosphere is the other main pathway for Hg release from the New Idria mine site. Analysis of three size fractions of calcine waste material exhibited an increase in Hg volatilization when exposed to light (>500 nm) over dark controls. Calcine size fractions of 500-2000 μm, 75-125 μm, and <45 μm exhibited light:dark ratios of 1.7 ± 0.05, 3.7 ± 0.05, and 4.3 ± 0.1, respectively. A new low-temperature EXAFS technique to directly detect liquid Hg(0) within Hg-contaminated soils was used to determine that mercury speciation in the three size fractions consisted of α-HgS, β-HgS, Eglestonite, Montroydite, and liquid Hg(0). The samples with light:dark ratios of 3.7 and 4.3 contained 10% and 9% Hg(0), respectively, while the

  4. Isotopic Variations of Mercury Emitted by Coal Fired Power Plant Gases

    NASA Astrophysics Data System (ADS)

    Khawaja, S. N.; Odom, L.; Landing, W.

    2010-12-01

    Emission of mercury from the burning of coal is considered one of the important anthropogenic sources of atmospheric mercury. Along with current measurements of the isotopic composition of atmospheric mercury being conducted in our laboratory, we have analyzed mercury emitted from a coal fired power plant. Previously Biswas and others (2008) had reported variations in the isotopic composition of mercury in a number of samples of coal deposits. Since the combustion of coal is expected to release virtually all of its mercury, we anticipated comparable isotopc patterns in coal and total emmited mercury. The emitted mercury exists in various physical and chemical forms, each possessing distinct properties that affect atmospheric transport, and sampling methods. Flue gas has been sampled in the stack of a coal fired electric power plant. The Ontario Hydro method was used to trap mercury in flue gases. The method uses oxidant solutions (KCl, H2O2-HNO3 and KMnO4-H2SO4) in its sampling train. This method is the modification of EPA method 29 with the use of KCl in the sampling train. Hg (II) is captured in the KCl impingers, while Hg (0) is captured in H2O2-HNO3 and KMnO4-H2SO4 impingers that oxidize elemental to Hg (ll) (EPA Draft, 1999). In addition gaseous reactive mercury was sampled downwind in large volume rain samples. Mercury (Hg+2) in sample solutions was reduced with SnCl2, and the generated Hg(0) vapor carried by Ar gas into the source of a NEPTUNE ICPMS-MC. Isotope ratios were measured by standard-sample bracketing and reported as permil deviations from the SRM NIST-3133 values. The measurement shows a small range of values of odd isotopes for mass independent fractionation which is negligible, However it displays the wide range of mass dependent fractionation (δ198 Hg -1.239 to 2.294). We found that samples in KCl impingers are light isotope enriched and depleted in heavy isotopes, while in KMnO4 impingers these are reverse.

  5. The DOE Isotopes Program

    NASA Astrophysics Data System (ADS)

    Gillo, Jehannes

    2015-10-01

    The DOE Isotope Program is a small federal program with a great deal of impact and is managed by the DOE Office of Nuclear Physics. The Isotope Program has been managed by the Office of Nuclear Physics since 2009, and since that time, has been re-defined in terms of mission, scope and operations. The program produces critical isotopes that are in short supply or simply unavailable from elsewhere to facilitate research and applications. Research is also supported to develop or improve production techniques that will increase availability of isotopes in high demand, such as alpha emitters for cancer therapy.

  6. Slurry sampling flow injection chemical vapor generation inductively coupled plasma mass spectrometry for the determination of trace Ge, As, Cd, Sb, Hg and Bi in cosmetic lotions.

    PubMed

    Chen, Wei-Ni; Jiang, Shiuh-Jen; Chen, Yen-Ling; Sahayam, A C

    2015-02-20

    A slurry sampling inductively coupled plasma mass spectrometry (ICP-MS) method has been developed for the determination of Ge, As, Cd, Sb, Hg and Bi in cosmetic lotions using flow injection (FI) vapor generation (VG) as the sample introduction system. A slurry containing 2% m/v lotion, 2% m/v thiourea, 0.05% m/v L-cysteine, 0.5 μg mL(-1) Co(II), 0.1% m/v Triton X-100 and 1.2% v/v HCl was injected into a VG-ICP-MS system for the determination of Ge, As, Cd, Sb, Hg and Bi without dissolution and mineralization. Because the sensitivities of the analytes in the slurry and that of aqueous solution were quite different, an isotope dilution method and a standard addition method were used for the determination. This method has been validated by the determination of Ge, As, Cd, Sb, Hg and Bi in GBW09305 Cosmetic (Cream) reference material. The method was also applied for the determination of Ge, As, Cd, Sb, Hg and Bi in three cosmetic lotion samples obtained locally. The analysis results of the reference material agreed with the certified value and/or ETV-ICP-MS results. The detection limit estimated from the standard addition curve was 0.025, 0.1, 0.2, 0.1, 0.15, and 0.03 ng g(-1) for Ge, As, Cd, Sb, Hg and Bi, respectively, in original cosmetic lotion sample. PMID:25682241

  7. Method of controlling the mercury vapor pressure in a photo-chemical lamp or vapor filter used for Hg.sup.196 enrichment

    DOEpatents

    Grossman, Mark W.

    1993-01-01

    The present invention is directed to a method of eliminating the cold spot zones presently used on Hg.sup.196 isotope separation lamps and filters by the use of a mercury amalgams, preferably mercury - indium amalgams. The use of an amalgam affords optimization of the mercury density in the lamp and filter of a mercury enrichment reactor, particularly multilamp enrichment reactors. Moreover, the use of an amalgam in such lamps and/or filters affords the ability to control the spectral line width of radiation emitted from lamps, a requirement for mercury enrichment.

  8. Method of controlling the mercury vapor pressure in a photo-chemical lamp or vapor filter used for Hg[sup 196] enrichment

    DOEpatents

    Grossman, M.W.

    1993-02-16

    The present invention is directed to a method of eliminating the cold spot zones presently used on Hg[sup 196] isotope separation lamps and filters by the use of a mercury amalgams, preferably mercury - indium amalgams. The use of an amalgam affords optimization of the mercury density in the lamp and filter of a mercury enrichment reactor, particularly multilamp enrichment reactors. Moreover, the use of an amalgam in such lamps and/or filters affords the ability to control the spectral line width of radiation emitted from lamps, a requirement for mercury enrichment.

  9. HCN Producing Bacteria Enable Sensing Of Non-Bioavailable Hg Species by the Whole Cell Biosensor

    NASA Astrophysics Data System (ADS)

    Horvat, M.; Rijavec, T.; Koron, N.; Lapanje, A.

    2015-12-01

    Bacteria play an important role in Hg transformation reactions. The production of cyanide (HCN) and other secondary metabolites seems to be key elements involved in these transformations. Current hypotheses link the role of HCN production to growth inhibition of nonHCN producing competitor organisms (role of an antimicrobial agent). Our past investigations showed that HCN production did not correlate with antimicrobial activity and since pK value of HCN is very high (pK = 9,21), it can be expected that most of the produced HCN is removed from the microenvironment. This way, the expected inhibitory concentrations can hardly be reached. Accordingly, we proposed a new concept, where the ability of complexation of transient metals by HCN served as a regulation process for the accessibility of micro-elements. In our study, we focused on the presence of HCN producing bacteria and carried it out in the Hg contaminated environment connected to the Idrija Mercury Mine, Slovenia. We characterised the isolates according to the presence of Hg resistance (HgR), level of HCN production and genetic similarities. In laboratory setups, using our merR whole cell based biosensor, we determined the transformation of low bioavailable Hg0 and HgS forms into bioavailable Hg by these HCN producing bacteria. We observed that HgR strains producing HCN had the highest impact on increased Hg bioavailability. In the proposed ecological strategy HgR HCN producing bacteria increase their competitive edge over non-HgR competitors through the increase of Hg toxicity. Due to their activity, Hg is made available to other organisms as well and thus enters into the ecosystem. Finally, using some of the characteristics of bacteria (e.g. Hg resistance genetic elements), we developed a fully automated sensing approach, combining biosensorics and mechatronics, to measure the bioavailability of Hg in situ.

  10. Multicollector ICPMS and TIMS as tools for isotopic fingerprinting

    NASA Astrophysics Data System (ADS)

    Bouman, C.; Schwieters, J. B.; Lloyd, N. S.; Trinquier, A.

    2012-04-01

    Elements such as C, N, O and S are essential for chemical and biological processes in nature and very small shifts in the isotopic composition of these elements are important tracers to explore complex processes in nature. During the last few years, stable isotopes of elements as Cl, Ca, Fe, Cu, Zn, Sr, Hg and Pb are getting more and more attention as tracer to study biomedical and environmental processes, as well as forensics and archaeometry. Multi-collector ICPMS and TIMS enable high-precision isotopic analysis of these so-called non-traditional stable isotope systems. MC-ICPMS is a powerful technique for the isotopic analysis of most elements, with the exception of light elements such as H, C, N and O and the noble gases. Various inlet systems can be used to introduce samples into the mass spectrometer, for instance gas chromatography (GC), liquid chromatography (LC) ) for compound-specific isotope analysis, laser ablation for direct analysis of solids, or conventional liquid nebulization for liquid samples. The aerosol is transported by an Ar and/or He gas flow into the ICP source where it is effectively ionized and introduced into the mass analyzer through a differential pumping system. Molecular interferences as carbides, nitrides, oxides, argides or doubly-charged species can show up in the mass spectrum and interfere with the elemental isotope peaks. High mass resolution is needed to effectively discriminate against these interferences. The NEPTUNE Plus is specially designed to meet this requirement and expand the power of isotope ratio measurements even to elements where previously isobaric interferences were the limit. For some specific isotope systems, such as Ca, Sr and Pb, the thermal ionization technique may have advantages, due to the potentially lower backgrounds and higher sensitivity. Prior to the TIMS analysis, the sample is chemically purified, loaded on a filament and introduced into the mass spectrometer. With the introduction of the TRITON

  11. Trophic dynamics of U, Ni, Hg and other contaminants of potential concern on the Department of Energy's Savannah River Site.

    PubMed

    Edwards, Paul G; Gaines, Karen F; Bryan, A Lawrence; Novak, James M; Blas, Susan A

    2014-01-01

    The Department of Energy's Savannah River Site is a former nuclear weapon material production and current research facility located in South Carolina, USA. Wastewater discharges from a fuel and nuclear reactor target manufacturing facility released depleted and natural U, as well as other metals into the Tims Branch-Steed Pond water system. We investigated the current dynamics of this system for the purposes of environmental monitoring and assessment by examining metal concentrations, bioavailability, and trophic transfer of contaminants in seven ponds. Biofilm, detritus, and Anuran and Anisopteran larvae were collected and analyzed for stable isotopes (δ (15)N, δ (13)C) and contaminants of potential concern (COPC) with a focus on Ni, U, and Hg, to examine metal mobility. Highest levels of Ni and U were found in biofilms U (147 and 332 mg kg(-1) DW, respectively), while highest Hg levels were found in tadpoles (1.1 mg kg(-1) DW). We found intraspecific biomagnification of COPCs as expressed through stable isotope analysis. Biofilms were the best indicators for contamination and Anuran larvae with the digestive tract removed were the best indicators of the specific bioavailability of the focal metals. Monitoring data showed that baseline δ (15)N values differed between ponds, but within a pond, values were stable throughout tadpole Gosner stage, strengthening the case to use this species for monitoring purposes. It is likely that there still is risk to ecosystem integrity as COPC metals are being assimilated into lower trophic organisms and even low levels of this mixture has shown to produce deleterious effects to some wildlife species. PMID:23979676

  12. Evaluating mercury biomagnification in fish from a tropical marine environment using stable isotopes (delta13C and delta15N).

    PubMed

    Al-Reasi, Hassan A; Ababneh, Fuad A; Lean, David R

    2007-08-01

    Concentrations of total mercury (T-Hg) and methylmercury (MeHg) were measured in zooplankton and 13 fish species from a coastal food web of the Gulf of Oman, an arm of the Arabian Sea between Oman and Iran. Stable isotope ratios (delta13C and delta15N) also were determined to track mercury biomagnification. The average concentration of T-Hg in zooplankton was 21 +/- 8.0 ng g(-1) with MeHg accounting 10% of T-Hg. Total mercury levels in fish species ranged from 3.0 ng g(-1) (Sardinella longiceps) to 760 ng g(-1) (Rhizoprionodon acutus) with relatively lower fraction of MeHg (72%) than that found in other studies. The average trophic difference (Deltadelta13C) between zooplankton and planktivorous fish (Selar crumenopthalmus, Rastrelliger kanagurta, and S. longiceps) was higher (3.4 per thousandth) than expected, suggesting that zooplankton may not be the main diet or direct carbon source for these fish species. However, further sampling would be required to compensate for temporal changes in zooplankton and the influence of their lipid content. Trophic position inferred by delta15N and and slopes of the regression equations (log10[T-Hg] = 0.13[delta15N] - 3.57 and log10[MeHg] = 0.14[delta15N] - 3.90) as estimates of biomagnification indicate that biomagnification of T-Hg and MeHg was lower in this tropical ocean compared to what has been observed in arctic and temperate ecosystems and tropical African lakes. The calculated daily intake of methylmercury in the diet of local people through fish consumption was well below the established World Health Organization (WHO) tolerable daily intake threshold for most of the fish species except Euthynnus affinis, Epinephelus epistictus, R. acutus, and Thunnus tonggol, illustrating safe consumption of the commonly consumed fish species. PMID:17702328

  13. Isotopically engineered semiconductors

    NASA Astrophysics Data System (ADS)

    Haller, E. E.

    1995-04-01

    Scientific interest, technological promise, and increased availability of highly enriched isotopes have led to a sharp rise in the number of experimental and theoretical studies with isotopically controlled semiconductor crystals. This review of mostly recent activities begins with an introduction to some past classical experiments which have been performed on isotopically controlled semiconductors. A review of the natural isotopic composition of the relevant elements follows. Some materials aspects resulting in part from the high costs of enriched isotopes are discussed next. Raman spectroscopy studies with a number of isotopically pure and deliberately mixed Ge bulk crystals show that the Brillouin-zone-center optical phonons are not localized. Their lifetime is almost independent of isotopic disorder, leading to homogeneous Raman line broadening. Studies with short period isotope superlattices consisting of alternating layers of n atomic planes of 70Ge and 74Ge reveal a host of zone-center phonons due to Brillouin-zone folding. At n≳40 one observes two phonon lines at frequencies corresponding to the bulk values of the two isotopes. In natural diamond, isotope scattering of the low-energy phonons, which are responsible for the thermal conductivity, is very strongly affected by small isotope disorder. Isotopically pure 12C diamond crystals exhibit thermal conductivities as high as 410 W cm-1 K-1 at 104 K, leading to projected values of over 2000 W cm-1 K-1 near 80 K. The changes in phonon properties with isotopic composition also weakly affect the electronic band structures and the lattice constants. The latter isotope dependence is most relevant for future standards of length based on crystal lattice constants. Capture of thermal neutrons by isotope nuclei followed by nuclear decay produces new elements, resulting in a very large number of possibilities for isotope selective doping of semiconductors. This neutron transmutation of isotope nuclei, already used

  14. Manila clams from Hg polluted sediments of Marano and Grado lagoons (Italy) harbor detoxifying Hg resistant bacteria in soft tissues

    SciTech Connect

    Baldi, Franco; Gallo, Michele; Marchetto, Davide; Faleri, Claudia; Maida, Isabel; Fani, Renato

    2013-08-15

    A mechanism of mercury detoxification has been suggested by a previous study on Hg bioaccumulation in Manila clams (Ruditapes philippinarum) in the polluted Marano and Grado lagoons and in this study we demonstrate that this event could be partly related to the detoxifying activities of Hg-resistant bacteria (MRB) harbored in clam soft tissues. Therefore, natural clams were collected in six stations during two different periods (winter and spring) from Marano and Grado Lagoons. Siphons, gills and hepatopancreas from acclimatized clams were sterile dissected to isolate MRB. These anatomical parts were glass homogenized or used for whole, and they were lying on a solid medium containing 5 mg l{sup −1} HgCl{sub 2} and incubated at 30 °C. A total of fourteen bacterial strains were isolated and were identified by 16S rDNA sequencing and analysis, revealing that strains were representative of eight bacterial genera, four of which were Gram-positive (Enterococcus, Bacillus, Jeotgalicoccus and Staphylococcus) and other four were Gram-negative (Stenotrophomonas, Vibrio, Raoultella and Enterobacter). Plasmids and merA genes were found and their sequences determined. Fluorescence in situ hybridization (FISH) technique shows the presence of Firmicutes, Actinobacteria and Gammaproteobacteria by using different molecular probes in siphon and gills. Bacterial clumps inside clam flesh were observed and even a Gram-negative endosymbiont was disclosed by transmission electronic microscope inside clam cells. Bacteria harbored in cavities of soft tissue have mercury detoxifying activity. This feature was confirmed by the determination of mercuric reductase in glass-homogenized siphons and gills. -- Highlights: ► We isolated Gram-positive and Gram-negative Hg resistant strains from soft tissues of Ruditapes philippinarum. ► We identify 14 mercury resistant strains by 16S rRNA gene sequences. ► Bacteria in siphon and gill tissues of clams were observed by TEM and identified

  15. Two new reversible naphthalimide-based fluorescent chemosensors for Hg(2.).

    PubMed

    Li, Gongchun; Gao, Guangqin; Cheng, Junye; Chen, Xiaopo; Zhao, Yufen; Ye, Yong

    2016-06-01

    Naphthalimide-based fluorescent probes 1 and 2 were synthesized, and were designed to form probe-Hg complexes through Hg(2+) ions coordinated to the amide group and imidazole group. They showed high sensitivity and were selective 'naked-eye' chemosensors for Hg(2+) in phosphate buffer. The fluorescence of compounds 1 and 2 could be quenched up to 90% by the addition of Hg(2+) . Reversible probes can detect Hg(2+) ions over a wide pH range (7.0-10.0). Copyright © 2015 John Wiley & Sons, Ltd. PMID:26592959

  16. Reversible "off-on" fluorescent chemosensor for Hg 2+ based on rhodamine derivative

    NASA Astrophysics Data System (ADS)

    Liu, Weimin; Chen, Jianhong; Xu, Liwei; Wu, Jiasheng; Xu, Haitao; Zhang, Hongyan; Wang, Pengfei

    2012-01-01

    A novel and simple fluorescent chemosensor based on rhodamine was designed and synthesized to detect Hg 2+ with high selectivity. The structure of chemosensor 1 was characterized by IR, 1H NMR, and HRMS spectroscopies. Chemosensor 1 exhibited distinct fluorescent and colorimetric changes toward Hg 2+ in an ethanol/water (80/20, v/v) solution, which resulted in the formation of 1/Hg 2+ complex with the Hg 2+-induced ring opening of the spirolactam ring in rhodamine. The reversibility of chemosensor 1 was verified through its spectral response toward Hg 2+ ions and TBAI (tetrabutylammonium iodide) titration experiments.

  17. Intracellular Cadmium Isotope Fractionation

    NASA Astrophysics Data System (ADS)

    Horner, T. J.; Lee, R. B.; Henderson, G. M.; Rickaby, R. E.

    2011-12-01

    Recent stable isotope studies into the biological utilization of transition metals (e.g. Cu, Fe, Zn, Cd) suggest several stepwise cellular processes can fractionate isotopes in both culture and nature. However, the determination of fractionation factors is often unsatisfactory, as significant variability can exist - even between different organisms with the same cellular functions. Thus, it has not been possible to adequately understand the source and mechanisms of metal isotopic fractionation. In order to address this problem, we investigated the biological fractionation of Cd isotopes within genetically-modified bacteria (E. coli). There is currently only one known biological use or requirement of Cd, a Cd/Zn carbonic anhydrase (CdCA, from the marine diatom T. weissfloggii), which we introduce into the E. coli genome. We have also developed a cleaning procedure that allows for the treating of bacteria so as to study the isotopic composition of different cellular components. We find that whole cells always exhibit a preference for uptake of the lighter isotopes of Cd. Notably, whole cells appear to have a similar Cd isotopic composition regardless of the expression of CdCA within the E. coli. However, isotopic fractionation can occur within the genetically modified E. coli during Cd use, such that Cd bound in CdCA can display a distinct isotopic composition compared to the cell as a whole. Thus, the externally observed fractionation is independent of the internal uses of Cd, with the largest Cd isotope fractionation occurring during cross-membrane transport. A general implication of these experiments is that trace metal isotopic fractionation most likely reflects metal transport into biological cells (either actively or passively), rather than relating to expression of specific physiological function and genetic expression of different metalloenzymes.

  18. Discovery of the krypton isotopes

    SciTech Connect

    Heim, M.; Fritsch, A.; Schuh, A.; Shore, A.; Thoennessen, M.

    2010-07-15

    Thirty-two krypton isotopes have been observed so far and the discovery of these isotopes is discussed here. For each isotope a brief summary of the first refereed publication, including the production and identification method, is presented.

  19. Contrasting Food Web Factor and Body Size Relationships with Hg and Se Concentrations in Marine Biota

    PubMed Central

    Karimi, Roxanne; Frisk, Michael; Fisher, Nicholas S.

    2013-01-01

    Marine fish and shellfish are primary sources of human exposure to mercury, a potentially toxic metal, and selenium, an essential element that may protect against mercury bioaccumulation and toxicity. Yet we lack a thorough understanding of Hg and Se patterns in common marine taxa, particularly those that are commercially important, and how food web and body size factors differ in their influence on Hg and Se patterns. We compared Hg and Se content among marine fish and invertebrate taxa collected from Long Island, NY, and examined associations between Hg, Se, body length, trophic level (measured by δ15N) and degree of pelagic feeding (measured by δ13C). Finfish, particularly shark, had high Hg content whereas bivalves generally had high Se content. Both taxonomic differences and variability were larger for Hg than Se, and Hg content explained most of the variation in Hg:Se molar ratios among taxa. Finally, Hg was more strongly associated with length and trophic level across taxa than Se, consistent with a greater degree of Hg bioaccumulation in the body over time, and biomagnification through the food web, respectively. Overall, our findings indicate distinct taxonomic and ecological Hg and Se patterns in commercially important marine biota, and these patterns have nutritional and toxicological implications for seafood-consuming wildlife and humans. PMID:24019976

  20. Contrasting food web factor and body size relationships with Hg and Se concentrations in marine biota.

    PubMed

    Karimi, Roxanne; Frisk, Michael; Fisher, Nicholas S

    2013-01-01

    Marine fish and shellfish are primary sources of human exposure to mercury, a potentially toxic metal, and selenium, an essential element that may protect against mercury bioaccumulation and toxicity. Yet we lack a thorough understanding of Hg and Se patterns in common marine taxa, particularly those that are commercially important, and how food web and body size factors differ in their influence on Hg and Se patterns. We compared Hg and Se content among marine fish and invertebrate taxa collected from Long Island, NY, and examined associations between Hg, Se, body length, trophic level (measured by δ(15)N) and degree of pelagic feeding (measured by δ(13)C). Finfish, particularly shark, had high Hg content whereas bivalves generally had high Se content. Both taxonomic differences and variability were larger for Hg than Se, and Hg content explained most of the variation in Hg:Se molar ratios among taxa. Finally, Hg was more strongly associated with length and trophic level across taxa than Se, consistent with a greater degree of Hg bioaccumulation in the body over time, and biomagnification through the food web, respectively. Overall, our findings indicate distinct taxonomic and ecological Hg and Se patterns in commercially important marine biota, and these patterns have nutritional and toxicological implications for seafood-consuming wildlife and humans. PMID:24019976

  1. Mercury methylation in paddy soil: source and distribution of mercury species at a Hg mining area, Guizhou Province, China

    NASA Astrophysics Data System (ADS)

    Zhao, Lei; Anderson, Christopher W. N.; Qiu, Guangle; Meng, Bo; Wang, Dingyong; Feng, Xinbin

    2016-04-01

    Rice paddy plantation is the dominant agricultural land use throughout Asia. Rice paddy fields have been identified as important sites for methylmercury (MeHg) production in the terrestrial ecosystem and a primary pathway of MeHg exposure to humans in mercury (Hg) mining areas. We compared the source and distribution of Hg species in different compartments of the rice paddy during a complete rice-growing season at two different typical Hg-contaminated mining sites in Guizhou province, China: an abandoned site with a high Hg concentration in soil but a low concentration in the atmosphere and a current-day artisanal site with a low concentration in soil but a high concentration in the atmosphere. Our results showed that the flux of new Hg to the ecosystem from irrigation and atmospheric deposition was insignificant relative to the pool of old Hg in soil; the dominant source of MeHg to paddy soil is in situ methylation of inorganic Hg (IHg). Elevated MeHg concentrations and the high proportion of Hg as MeHg in paddy water and the surface soil layer at the artisanal site demonstrated active Hg methylation at this site only. We propose that the in situ production of MeHg in paddy water and surface soil is dependent on elevated Hg in the atmosphere and the consequential deposition of new Hg into a low-pH anoxic geochemical system. The absence of depth-dependent variability in the MeHg concentration in soil cores collected from the abandoned Hg mining site, consistent with the low concentration of Hg in the atmosphere and high pH of the paddy water and irrigation water, suggested that net production of MeHg at this site was limited. We propose that the concentration of Hg in ambient air is an indicator for the risk of MeHg accumulation in paddy rice.

  2. Au(n)Hg(m) clusters: mercury aurides, gold amalgams, or van der Waals aggregates?

    PubMed

    Zaleski-Ejgierd, Patryk; Pyykkö, Pekka

    2009-11-12

    The class of bimetallic clusters, Au(n)M(m) (M = Zn, Cd, Hg), is calculated at the ab initio level using the DFT, RI-MP2, and CCSD(T) methods. For the triatomic Au2M (M = Zn, Cd), the auride-type linear Au-M-Au structures are preferred; for Au2Hg, the linear Au-Au-Hg "amalgam" is preferred. The mixed cation [HgAuHg]+, an analog of the known solid-state species Hg32+, is predicted. For larger Au(n)Hg(m) clusters, the results are similar to the isoelectronic Au(n)M- anions. Several local minima and transition states are identified. All are found to be planar. PMID:19228004

  3. Environmental impacts of the Tennessee Valley Authority Kingston coal ash spill. 1. Source apportionment using mercury stable isotopes.

    PubMed

    Bartov, Gideon; Deonarine, Amrika; Johnson, Thomas M; Ruhl, Laura; Vengosh, Avner; Hsu-Kim, Heileen

    2013-02-19

    Mercury stable isotope abundances were used to trace transport of Hg-impacted river sediment near a coal ash spill at Harriman, Tennessee, USA. δ(202)Hg values for Kingston coal ash released into the Emory River in 2008 are significantly negative (-1.78 ± 0.35‰), whereas sediments of the Clinch River, into which the Emory River flows, are contaminated by an additional Hg source (potentially from the Y-12 complex near Oak Ridge, Tennessee) with near-zero values (-0.23 ± 0.16‰). Nominally uncontaminated Emory River sediments (12 miles upstream from the Emory-Clinch confluence) have intermediate values (-1.17 ± 0.13‰) and contain lower Hg concentrations. Emory River mile 10 sediments, possibly impacted by an old paper mill has δ(202)Hg values of -0.47 ± 0.04‰. A mixing model, using δ(202)Hg values and Hg concentrations, yielded estimates of the relative contributions of coal ash, Clinch River, and Emory River sediments for a suite of 71 sediment samples taken over a 30 month time period from 13 locations. Emory River samples, with two exceptions, are unaffected by Clinch River sediment, despite occasional upstream flow from the Clinch River. As expected, Clinch River sediment below its confluence with the Emory River are affected by Kingston coal ash; however, the relative contribution of the coal ash varies among sampling sites. PMID:23157719

  4. Mercury concentrations in fish from forest harvesting and fire-impacted Canadian Boreal lakes compared using stable isotopes of nitrogen.

    PubMed

    Garcia, Edenise; Carignan, Richard

    2005-03-01

    Total mercury (Hg) concentration was determined in several piscivorous and nonpiscivorous species of fish from 38 drainage lakes with clear-cut, burnt, or undisturbed catchments located in the Canadian Boreal Shield. Mercury concentrations increased with increasing fish trophic position as estimated using stable isotopes of nitrogen (N; r2 = 0.52, 0.49, and 0.30 for cut, reference, and burnt lakes, respectively; p < 0.01). Mercury biomagnification per thousand delta15N varied from 22 to 29% in the three groups of lakes. Mercury availability to organisms at the base of the food chain in lakes with cut catchments was higher than that in reference lakes. In cut lakes, Hg concentrations in fish were significantly related to ratio of the clear-cut area to lake area (or lake volume; r = +0.82 and +0.74, respectively, p < 0.01). Both impact ratios were, in turn, significantly correlated with dissolved organic carbon. These findings suggest that differential loading of organic matter-bound Hg to lakes can affect Hg cycling. In addition, Hg concentrations exceeded the advisory limit for human consumption (0.5 microg/g wet wt) from the World Health Organization in all top predatory species (northern pike, walleye, and burbot) found in cut and in two partially burnt lakes. Thus, high Hg concentrations in fish from forest-harvested and partially burnt lakes may reflect increased exposure to Hg relative to that in lakes not having these watershed disturbances. PMID:15779770

  5. (Carbon isotope fractionation inplants)

    SciTech Connect

    O'Leary, M.H.

    1990-01-01

    The objectives of this research are: To develop a theoretical and experimental framework for understanding isotope fractionations in plants; and to develop methods for using this isotope fractionation for understanding the dynamics of CO{sub 2} fixation in plants. Progress is described.

  6. Detecting isotopic ratio outliers

    SciTech Connect

    Bayne, C.K.; Smith, D.H.

    1985-01-01

    An alternative method is proposed for improving isotopic ratio estimates. This method mathematically models pulse-count data and uses iterative reweighted Poisson regression to estimate model parameters to calculate the isotopic ratios. This computer-oriented approach provides theoretically better methods than conventional techniques to establish error limits and to identify outliers. 6 refs., 3 figs., 3 tabs.

  7. Spatial distribution and accumulation of Hg in soil surrounding a Zn/Pb smelter.

    PubMed

    Wu, Qingru; Wang, Shuxiao; Wang, Long; Liu, Fang; Lin, Che-Jen; Zhang, Lei; Wang, Fengyang

    2014-10-15

    Nonferrous metal smelting is an important atmospheric mercury (Hg) emission source that has significant local and global impacts. To quantify the impact of Hg emission from non-ferrous metal smelter on the surrounding soil, an integrated model parameterizing the processes of smelter emission, air dispersion, atmospheric deposition and Hg accumulation in soil was developed. The concentrations of gaseous elemental Hg (GEM) around the smelter and the spatial distribution of Hg in the surrounding soil were measured and compared with the model results. Atmospheric deposition of Hg emitted from the smelter was identified as the main source of Hg accumulation in the surrounding soil. From 1960 to 2011, the smelter emitted approximately 105 t of Hg into the atmosphere, of which 15 t deposited locally and resulted in an increase of Hg concentration in soil from 0.12 to 1.77 mg kg(-1). A detailed examination of wind rose and model data suggested that the area within 1.0-1.5 km northwest and southeast of the smelter was most severely impacted. It was estimated that the smelter operation from 1969 to 1990, when large scale emission controls were not implemented, resulted in 6450 μg m(-2)yr(-1) of Hg net deposition and a model simulated increase of 0.40 mg kg(-1) of Hg accumulation in the soil. During the period from 1991 to 2011, atmospheric Hg emission from the smelter alone increased the average concentration in soil from 0.41 mg kg(-1) to 0.45 mg kg(-1). In the past 50 years, over 86% of Hg emitted from this smelter went into the global pool, indicating the importance of controlling Hg emissions from non-ferrous metal smelters. PMID:24612491

  8. Mercury in estuarine systems: Downcore trends of Hg in San Francisco and Tomales Bay, CA

    SciTech Connect

    Hornberger, M.I.; Luoma, S.N.

    1995-12-31

    Mining, both historic and current, is a source of concern with regard to inputs of Hg into the environment. Active Hg mine sites exist primarily in the Circumpacific and Mediterranean-Himalayan belts and Hg releases are associated with gold mining in the same areas. Sediment cores collected in San Francisco Bay (SFB) and Tomales Bay (TB) show contaminant profiles of Hg and provide a historical perspective on Hg contamination where both Hg mining and gold mining occurred in the watershed. Three sources of input of Hg contamination to SFB can be identified: hydraulic gold mining in the late 1800`s in the Sierra Nevada mountains; Hg mined in the watershed of the South Bay; and industry. Historical sources into TB are limited to inputs from local Hg mining. Pre-anthropogenic concentrations of Hg in both Bays were 0.05 ug/g. Maximum concentrations in TB reached 0.4 {micro}g/g in the upper 40 cm. Maximum concentrations in SFB were {approximately}0.5--1.0 {micro}g/g. The highest concentrations of Hg are buried at 1 m depth in the North Bay cores, suggesting inputs of Hg from mining in the Sierra Nevada mountains during the late 1800`s to early 1900`s. This suggests that modern industrial sources are small compared to the mass of Hg employed by mining. Enriched concentrations of Hg near the mouth of the estuary average about 0.5 {micro}g/g. The difference from upstream is consistent with dilution of contaminated riverine sediment, with clean, marine sediment, as indicated by geologic tracers (Cr and Al) in sediments from the Sierra Nevada Mountain ranges.

  9. Optical phase conjugation in Hg1 - xCdxTe.

    PubMed

    Khan, M A; Kruse, P W; Ready, J F

    1980-06-01

    We have observed phase-conjugate signals at 12, 77, and 295 K in n-type Hg1 - xCdxTe (x = 0.216-0.232) using degenerate four-wave mixing at 10.6 microm. The external power-reflection coefficient increases with the product of pump-power densities and saturates at 9%. The values of the third-order nonlinear susceptibility X(3) derived from these measurements agree with the theory of Wolff and Pearson [Phys. Rev. Lett. 17, 1015 (1966)] for X(3) that is due to conduction-band nonparabolicity. PMID:19693194

  10. Apparatus for growing HgI.sub.2 crystals

    DOEpatents

    Schieber, Michael M.; Beinglass, Israel; Dishon, Giora

    1978-01-01

    A method and horizontal furnace for vapor phase growth of HgI.sub.2 crystals which utilizes controlled axial and radial airflow to maintain the desired temperature gradients. The ampoule containing the source material is rotated while axial and radial air tubes are moved in opposite directions during crystal growth to maintain a desired distance and associated temperature gradient with respect to the growing crystal, whereby the crystal interface can advance in all directions, i.e., radial and axial according to the crystallographic structure of the crystal. Crystals grown by this method are particularly applicable for use as room-temperature nuclear radiation detectors.

  11. Ultra-stable Hg(+) trapped ion frequency standard

    NASA Technical Reports Server (NTRS)

    Prestage, John D.; Dick, G. John; Maleki, Lute

    1990-01-01

    A fieldable trapped ion frequency standard based on Hg-199(+) ions confined in a hybrid rf/dc linear ion trap is developed. This trap permits storage of large numbers of ions with reduced susceptibility to the second-order Doppler effect caused by the rf confining fields. In preliminary measurements a stability of 2 to 3 x 10(exp -15) was obtained for 10000 second averaging times. These measurements were carried out with a 120 mHz wide atomic resonance line for the 40.5 GHz clock transition with a second order Doppler shift from the rf trapping field of 6 x 10(exp -13).

  12. Complex band structure in neutron-deficient {sup 178}Hg

    SciTech Connect

    Kondev, F. G.; Carpenter, M. P.; Janssens, R. V. F.; Wiedenhoever, I.; Alcorta, M.; Bhattacharyya, P.; Brown, L. T.; Davids, C. N.; Fischer, S. M.; Khoo, T. L.

    2000-01-01

    Using the GAMMASPHERE array in conjunction with the Fragment Mass Analyzer, the level structure of the near drip-line nucleus {sup 178}Hg has been considerably expanded with the recoil-decay tagging technique. Of particular interest is a new rotational band which exhibits a complex decay towards the low spin states arising from both the prolate-deformed and the nearly spherical coexisting minima. It is proposed that this band is associated at low spin with an octupole vibration which is crossed at moderate frequency by a shape driving, two quasiproton excitation. (c) 1999 The American Physical Society.

  13. MOS structures based on epitaxial HgCdTe layers

    SciTech Connect

    Antonov, V.V.; Belashov, Y.G.; Kazak, E.P.; Mezentseva, M.P.; Voitsekhovskii, A.V.

    1985-08-01

    The authors present the results of a study of the dependence of the surface photoelectromotive force at wavelengths of 3.39 and 10.6 micrometers on the field electrode for MOS structures prepared from epitaxial Hg /SUB 1-x/ Cd /SUB x/ Te layers (x=0.20-0.25). They analyze the nature of the inhomogeneities in the region near the surface of semiconducting samples prepared under various heat treatment conditions and present their findings in a series of three charts.

  14. Laser isotope separation

    DOEpatents

    Robinson, C. Paul; Jensen, Reed J.; Cotter, Theodore P.; Boyer, Keith; Greiner, Norman R.

    1988-01-01

    A process and apparatus for separating isotopes by selective excitation of isotopic species of a volatile compound by tuned laser light. A highly cooled gas of the volatile compound is produced in which the isotopic shift is sharpened and defined. Before substantial condensation occurs, the cooled gas is irradiated with laser light precisely tuned to a desired wavelength to selectively excite a particular isotopic species in the cooled gas. The laser light may impart sufficient energy to the excited species to cause it to undergo photolysis, photochemical reaction or even to photoionize. Alternatively, a two-photon irradiation may be applied to the cooled gas to induce photolysis, photochemical reaction or photoionization. The process is particularly applicable to the separation of isotopes of uranium.

  15. Photochemical isotope separation

    DOEpatents

    Robinson, C. Paul; Jensen, Reed J.; Cotter, Theodore P.; Greiner, Norman R.; Boyer, Keith

    1987-01-01

    A process for separating isotopes by selective excitation of isotopic species of a volatile compound by tuned laser light. A highly cooled gas of the volatile compound is produced in which the isotopic shift is sharpened and defined. Before substantial condensation occurs, the cooled gas is irradiated with laser light precisely tuned to a desired wavelength to selectively excite a particular isotopic species in the cooled gas. The laser light may impart sufficient energy to the excited species to cause it to undergo photochemical reaction or even to photoionize. Alternatively, a two-photon irradiation may be applied to the cooled gas to induce photochemical reaction or photoionization. The process is particularly applicable to the separation of isotopes of uranium and plutonium.

  16. Discovery of Isotopes

    NASA Astrophysics Data System (ADS)

    May, Erin; Thoennessen, Michael

    2011-10-01

    To date, no comprehensive study has been undertaken regarding the initial detection and identification of isotopes. At NSCL, a project has been initiated to catalog and report the initial observation of every isotope. The conditions characterizing the successful discovery of an isotope include a clear and unambiguous mass and element identification through decay curves, mass spectroscopy, gamma-ray spectra, and/or relationships to other isotopes, as well as the publication of such findings in a refereed journal. I will present the documentation for eight elements: cesium, lanthanum, praseodymium, promethium, samarium, europium, gadolinium, and terbium. The year and author of each initial publication along with the location and methods of production and identification will be shown. A summary and overview of all ~3000 isotopes documented so far as a function of discovery year, method and place will also be presented.

  17. Photochemical isotope separation

    DOEpatents

    Robinson, C.P.; Jensen, R.J.; Cotter, T.P.; Greiner, N.R.; Boyer, K.

    1987-04-28

    A process is described for separating isotopes by selective excitation of isotopic species of a volatile compound by tuned laser light. A highly cooled gas of the volatile compound is produced in which the isotopic shift is sharpened and defined. Before substantial condensation occurs, the cooled gas is irradiated with laser light precisely tuned to a desired wavelength to selectively excite a particular isotopic species in the cooled gas. The laser light may impart sufficient energy to the excited species to cause it to undergo photochemical reaction or even to photoionize. Alternatively, a two-photon irradiation may be applied to the cooled gas to induce photochemical reaction or photoionization. The process is particularly applicable to the separation of isotopes of uranium and plutonium. 8 figs.

  18. Laser isotope separation

    DOEpatents

    Robinson, C.P.; Reed, J.J.; Cotter, T.P.; Boyer, K.; Greiner, N.R.

    1975-11-26

    A process and apparatus for separating isotopes by selective excitation of isotopic species of a volatile compound by tuned laser light is described. A highly cooled gas of the volatile compound is produced in which the isotopic shift is sharpened and defined. Before substantial condensation occurs, the cooled gas is irradiated with laser light precisely tuned to a desired wavelength to selectively excite a particular isotopic species in the cooled gas. The laser light may impart sufficient energy to the excited species to cause it to undergo photolysis, photochemical reaction or even to photoionize. Alternatively, a two-photon irradiation may be applied to the cooled gas to induce photolysis, photochemical reaction or photoionization. The process is particularly applicable to the separation of isotopes of uranium.

  19. Discovering Mercury Protein Modifications in Whole Proteomes Using Natural Isotope Distributions Observed in Liquid Chromatography-Tandem Mass Spectrometry

    SciTech Connect

    Polacco, Benjamin J.; Purvine, Samuel O.; Zink, Erika M.; LaVoie, Stephen P.; Lipton, Mary S.; Summers, Anne O.; Miller, Susan M.

    2011-08-01

    The identification of peptides that result from post-translational modifications is critical for understanding normal pathways of cellular regulation as well as identifying damage from, or exposures to xenobiotics, i.e. the exposome. However, because of their low abundance in proteomes, effective detection of modified peptides by mass spectrometry (MS) typically requires enrichment to eliminate false identifications. We present a new method for confidently identifying peptides with mercury (Hg)-containing adducts that is based on the influence of mercury’s seven stable isotopes on peptide isotope distributions detected by high-resolution MS. Using a pure protein and E. coli cultures exposed to phenyl mercuric acetate, we show the pattern of peak heights in isotope distributions from primary MS single scans efficiently identified Hg adducts in data from chromatographic separation coupled with tandem mass spectrometry with sensitivity and specificity greater than 90%. Isotope distributions are independent of peptide identifications based on peptide fragmentation (e.g. by SEQUEST), so both methods can be combined to eliminate false positives. Summing peptide isotope distributions across multiple scans improved specificity to 99.4% and sensitivity above 95%, affording identification of an unexpected Hg modification. We also illustrate the theoretical applicability of the method for detection of several less common elements including the essential element, selenium, as selenocysteine in peptides.

  20. Accelerated hydration reaction of an unsymmetrical tolan evidenced by a Hg(ii)-trapped macrocycle and its application as a Hg(ii)-selective indicator.

    PubMed

    Hong, Jung-Ho; Kurapati, Sathish; Jo, Yunhee; Shin, June-Ho; Cho, Dong-Gyu

    2016-09-14

    Hg(ii)-mediated hydration reactions of unsymmetrical quinoline type tolans were studied. The observed accelerated reactions of the tolans rely on the additional binding motifs of the tolan, as supported by the X-ray structure of the macrocycle (2b). The analyte-specific reaction allows us to detect Hg(ii) in buffered media. PMID:27510469

  1. International system of units traceable results of Hg mass concentration at saturation in air from a newly developed measurement procedure.

    PubMed

    Quétel, Christophe R; Zampella, Mariavittoria; Brown, Richard J C; Ent, Hugo; Horvat, Milena; Paredes, Eduardo; Tunc, Murat

    2014-08-01

    Data most commonly used at present to calibrate measurements of mercury vapor concentrations in air come from a relationship known as the "Dumarey equation". It uses a fitting relationship to experimental results obtained nearly 30 years ago. The way these results relate to the international system of units (SI) is not known. This has caused difficulties for the specification and enforcement of limit values for mercury concentrations in air and in emissions to air as part of national or international legislation. Furthermore, there is a significant discrepancy (around 7% at room temperature) between the Dumarey data and data calculated from results of mercury vapor pressure measurements in the presence of only liquid mercury. As an attempt to solve some of these problems, a new measurement procedure is described for SI traceable results of gaseous Hg concentrations at saturation in milliliter samples of air. The aim was to propose a scheme as immune as possible to analytical biases. It was based on isotope dilution (ID) in the liquid phase with the (202)Hg enriched certified reference material ERM-AE640 and measurements of the mercury isotope ratios in ID blends, subsequent to a cold vapor generation step, by inductively coupled plasma mass spectrometry. The process developed involved a combination of interconnected valves and syringes operated by computer controlled pumps and ensured continuity under closed circuit conditions from the air sampling stage onward. Quantitative trapping of the gaseous mercury in the liquid phase was achieved with 11.5 μM KMnO4 in 2% HNO3. Mass concentrations at saturation found from five measurements under room temperature conditions were significantly higher (5.8% on average) than data calculated from the Dumarey equation, but in agreement (-1.2% lower on average) with data based on mercury vapor pressure measurement results. Relative expanded combined uncertainties were estimated following a model based approach. They ranged from 2

  2. A new rhodamine-based "off-on" fluorescent chemosensor for Hg (II) ion and its application in imaging Hg (II) in living cells.

    PubMed

    Yan, Fanyong; Cao, Donglei; Wang, Meng; Yang, Ning; Yu, Qiuhua; Dai, Linfeng; Chen, Li

    2012-09-01

    A novel rhodamine derivative (Rh-C), synthesized by the reaction of rhodamine ethylenediamine and cinnamoyl chloride, was evaluated as a chemoselective Hg(2+) ion sensor. Addition of Hg(2+) to an ethanol aqueous solution of the Rh-C resulted in a color change from colorless to obvious pink color together with distinctive changes in UV-vis absorption spectrum and fluorescence spectrum. However, other common alkali-, alkaline earth-, transition- and rare earth metal ions induced no or minimal spectral changes. The interaction of Hg(2+) and sensor Rh-C was proven to adopt a 1:1 binding stoichiometry and the recognition process is reversible. The chemosensor displayed a linear response to Hg(2+) in the range of 0.4-5 μM with a detection limit of 7.4 × 10(-8) M. The sensor Rh-C was also successfully applied to the imaging of Hg(2+) in HL-7702 cells. PMID:22695925

  3. Characterization of Electronic Materials HgZnSe and HgZnTe Using Innovative and Conventional Techniques

    NASA Technical Reports Server (NTRS)

    Tanton, George; Kesmodel, Roy; Burden, Judy; Su, Ching-Hua; Cobb, Sharon D.; Lehoczky, S. L.

    2000-01-01

    HgZnSe and HgZnTe are electronic materials of interest for potential IR detector and focal plane array applications due to their improved strength and compositional stability over HgCdTe, but they are difficult to grow on Earth and to fully characterize. Conventional contact methods of characterization, such as Hall and van der Paw, although adequate for many situations are typically labor intensive and not entirely suitable where only very small samples are available. To adequately characterize and compare properties of electronic materials grown in low earth orbit with those grown on Earth, innovative techniques are needed that complement existing methods. This paper describes the implementation and test results of a unique non-contact method of characterizing uniformity, mobility, and carrier concentration together with results from conventional methods applied to HgZnSe and HgZnTe. The innovative method has advantages over conventional contact methods since it circumvents problems of possible contamination from alloying electrical contacts to a sample and also has the capability to map a sample. Non- destructive mapping, the determination of the carrier concentration and mobility at each place on a sample, provides a means to quantitatively compare, at high spatial resolution, effects of microgravity on electronic properties and uniformity of electronic materials grown in low-Earth orbit with Earth grown materials. The mapping technique described here uses a 1mm diameter polarized beam of radiation to probe the sample. Activation of a magnetic field, in which the sample is placed, causes the plane of polarization of the probe beam to rotate. This Faraday rotation is a function of the free carrier concentration and the band parameters of the material. Maps of carrier concentration, mobility, and transmission generated from measurements of the Faraday rotation angles over the temperature range from 300K to 77K will be presented. New information on band parameters

  4. KEY COMPARISON: CCQM-K43: As, Hg, Pb, Se and methylmercury in salmon

    NASA Astrophysics Data System (ADS)

    Aregbe, Y.; Taylor, P. D. P.

    2006-01-01

    CCQM-K43 was organized as a follow-up key comparison to the previous pilot study on tuna fish. CCQM-K43 was an activity of the Inorganic Analysis Working Group (IAWG) of CCQM and was coordinated by the Joint Research Centre-Institute for Reference Materials and Measurements (IRMM, Geel, Belgium) of the European Commission (EC). In CCQM-K43 the amount contents of As, Hg, Pb, Se and methylmercury (CH3Hg) in salmon (muscle and skin) were the measurands under investigation. Results were reported by 12 national metrology institutes (NMIs). During the CCQM-IAWG autumn meeting in Berlin, October 2005, it was agreed that in CCQM-K43 the KCRV is calculated as the mixture model median (MM-median) of all reported results. The reported results of the NMIs fall within a range of +/-5% for arsenic and of +/-2% for lead and mercury relative to the KCRV. For selenium the spread of all laboratories but one is +/-8%. Also, for methlymercury four of the five participating NMIs reported results within 4% deviation from the KCRV. The methods applied were isotope dilution mass spectrometry (IDMS) using sector field or quadrupole inductively coupled plasma-mass spectrometry (ICP-MS) or thermal ionization mass spectrometry (TIMS), external calibration using ICP-MS or atomic absorption spectrometry (AAS). Instrumental neutron activation analysis (INAA) and k0-neutron activation analysis (k0-NAA) were also used as analytical techniques. This report presents the participants' results in CCQM-K43 for all analytes under investigation. In Annex 1, the results with the KCRV, the equivalence statements and the results sorted according to analytical technique applied are presented. In Annex 2, the different approaches for methlymercury measurements are presented in more detail. In Annex 3, the questionnaire data are presented. Annex 4 compiles all the CCQM-K43 information documents. The pilot study CCQM-P39.1 was carried out in parallel to this key comparison for the same measurands in the same

  5. Xe isotopic fractionation in a cathodeless glow discharge

    NASA Astrophysics Data System (ADS)

    Bernatowicz, T. J.; Fahey, A. J.

    1986-03-01

    Results are reported on the isotopic composition of Xe processed in cathodeless glow discharges in rarefied air at pressures of 20-40 microns Hg, in the presence of activated charcoal and in empty pyrex containers. Residual gas phase Xe and trapped Xe were found to be fractionated, with the trapped Xe fractionated up to 1 percent per amu. A model is presented for the fractionating process in which Xe ions are simultaneously implanted and sputtered from substrate material, with a mass dependence favoring retention of the heavy isotopes in the substrate. Results of the investigation show that plasma synthesis of carbonaceous material is unnecessary for producing Xe fractionations, and that the fractionations observed in previous synthesis experiments are probably due to implantation of ions into the synthesized material.

  6. New features of superdeformed bands in {sup 194}Hg

    SciTech Connect

    Janssens, R.V.F.; Ahmad, I.; Carpenter, M.P.

    1995-08-01

    A striking difference between superdeformed (SD) nuclei near A = 190 and those in the other regions is the behavior of the dynamic moment of inertia (lm) with the rotational frequency h{omega}. While the (lm) patterns of the SD bands near A = 130 and A = 150 show pronounced variations, the majority of the SD bands near A = 190 display the same large, smooth increase of (lm) within the frequency range 0.15 < {h_bar}{omega} < 0.40 MeV. Current interpretations of this rise of (lm) within mean field theories invoke the gradual alignment of quasiparticles occupying high-N intruder orbitals in the presence of pair correlations. It is a direct consequence of these interpretations that, after the quasiparticle alignments take place, (lm) will exhibit a downturn with increasing {h_bar}{omega} toward the rigid-body value. Up to now, no downturn in (lm) for the SD bands in the A = 190 mass region was observed, raising some doubt as to our understanding of pair correlations and alignment effects at these large deformations. An experiment was carried out at the 88-Inch Cyclotron facility of the Lawrence Berkeley Laboratory where excited states in {sup 194}Hg were populated with the reaction {sup 150}Nd({sup 48}Ca,4n) {sup 194}Hg at a beam energy of 206 MeV. The gamma rays emitted in the reaction were detected with the Gammasphere detector array (32 detectors for this experiment).

  7. Thirty years of HgCdTe technology in Israel

    NASA Astrophysics Data System (ADS)

    Weiss, Eliezer

    2009-05-01

    The study of HgCdTe technology in Israel began in the mid 1970's under the leadership of the late Prof. Kidron and his group at the Technion, Israel Institute of Technology. The R&D efforts were continued by other groups at the Technion and other universities and research institutes in Israel, as well as by SCD. Many aspects of the technology of this material were studied, including both bulk crystal and epitaxial growths and microelectronic fabrication methods, with an emphasis on surface treatment and passivation. Various characterization methods were developed to study both the basic and applied material and device properties. The efforts, reviewed in this article, matured at SCD as it commercialized the HgCdTe technology, launching large-volume production lines of state-of-the-art linear and multi-linear TDI LWIR detector arrays of various sizes from 10×1 to 480×6 elements. Over the years, SCD has supplied its customers with thousands of both photoconductive (PC) and photovoltaic (PV) detectors, which are briefly presented in the paper.

  8. Mercury (Hg) emissions from domestic biomass combustion for space heating.

    PubMed

    Huang, Jiaoyan; Hopke, Philip K; Choi, Hyun-Deok; Laing, James R; Cui, Huailue; Zananski, Tiffany J; Chandrasekaran, Sriraam Ramanathan; Rattigan, Oliver V; Holsen, Thomas M

    2011-09-01

    Three mercury (Hg) species (gaseous elemental mercury (GEM), gaseous oxidized mercury (GOM), and fine particulate-bound mercury (PBM(2.5))) were measured in the stack of a small scale wood combustion chamber at 400°C, in the stack of an advanced wood boiler, and in two areas influenced by wood combustion. The low temperature process (lab-scale) emitted mostly GEM (∼99% when burning wood pellets and ∼95% when burning unprocessed wood). The high temperature wood boiler emitted a greater proportion of oxidized Hg (approximately 65%) than the low temperature system. In field measurements, mean PBM(2.5) concentrations at the rural and urban sites in winter were statistically significantly higher than in warmer seasons and were well correlated with Delta-C concentrations, a wood combustion indictor measured by an aethalometer (UV-absorbable carbon minus black carbon). Overall the results suggest that wood combustion may be an important source of oxidized mercury (mostly in the particulate phase) in northern climates in winter. PMID:21620435

  9. MBE (Molecular Beam Epitaxial) growth characterization and electronic device processing of HgCdTe, HgZnTe related heterojunctions and HgCdTe-CdTe superlattices

    NASA Astrophysics Data System (ADS)

    Faurie, Jean-Pierre

    1987-06-01

    As the MBE growth technique has continued to improve for Hg(1-x)Cd(x)Te films, the prospects for films of larger area have begun to be explored. These larger area films are important for imaging arrays and will be especially vital in the future for the efficient production of Hg(1-x)Cd(x)Te material. The growth of MBE of uniform Hg(1-x)Cd(x)Te epilayer on a large substrate is very difficult to achieve because of the non-uniform distribution of the fluxes and on the non-uniform temperature of the substrate.

  10. Body Burden of Hg in Different Bio-Samples of Mothers in Shenyang City, China

    PubMed Central

    Xu, Jian; Du, Juan; Yan, Chong-huai

    2014-01-01

    Hg is an accumulative and neuro-toxic heavy metal which has a wide range of adverse effects in human health. However, few studies are available on body burden of Hg level in different bio-samples of pregnant women in Chinese population. Therefore, this study evaluated Hg levels in different maternal bio-samples in Shenyang city, China and investigated the correlation of Hg levels in different bio-samples. From October to December 2008, 200 pregnant women about to deliver their babies at ShengJing Hospital (Shenyang city, northeast of China) participated in this study. The geometric mean (GM) of Hg levels in cord blood, maternal venous blood, breast milk, and maternal urine were 2.18 µg/L, 1.17 µg/L, 1.14 µg/L, and 0.73 µg/L, respectively, and the GM of maternal hair Hg level was 404.45 µg/kg. There was a strong correlation between cord blood and maternal blood total Hg level (r = 0.713, P<0.001). Frequency of fish consumption more than or equal to 3 times per week during pregnancy was suggested as a significant risk factor of prenatal Hg exposure (unadjusted OR 3.5, adjusted OR 2.94, P<0.05). This study provides evidence about Hg burden of mothers and the risk factors of prenatal Hg exposure in Shenyang city, China. PMID:24858815

  11. New thermodynamic data on the Hg-O-S system: With application to the thermal processing of mercury containing wastes

    SciTech Connect

    Fredrickson, G.L.; Hager, J.P.

    1996-12-31

    A modified transpiration reactor was used to measure the composition of the equilibrium gas phase formed above compounds in the Hg-O-S system at high temperatures (600 to 900K). A thermodynamic database ({Delta}G{degrees}{sub f}, {Delta}H{degrees}{sub f}, {Delta}S{degrees}{sub f}) for HgO, HgS, HgSO{sub 4}, Hg{sub 2}SO{sub 4}, HgSO{sub 4}-HgO, and HgSO{sub 4}{circ}2HgO was developed based on the experimental results. Prior to this study, only estimated data were available in the literature for the sulfates and oxysulfates at temperatures above 298K. A series of vapor pressure / stability diagrams were constructed from 473 to 973K with isobars of Hg(g), HgO(g), S{sub 2}(g), and SO{sub 3}(g). These diagrams were found to be significantly different than those available previously and do provide insight to the phase relations of importance during the thermal processing of Hg-containing wastes. The thermodynamic results were used to conduct a series of Gibbs energy minimization calculations for a thermal processor / afterburner system for the treatment of HgS-containing wastes. The retention of Hg in the discharge calcine was examined as a function of temperature and excess air. Hg was found to report to the calcine as HgSO{sub 4}, Hg{sub 2}SO{sub 4}, or HgSO{sub 4}-HgO depending on the process conditions, and Hg retention occurs at temperatures as high as 930K. The precipitation of Hg-containing phases from cooled afterburner discharge gas starts at approximately 900K and the cooling of the gas an additional 30K (to 870K) results in over 50% of the Hg being precipitated as HgSO{sub 4}-HgO. It was also determined that for small amounts of Hg present in sulfide concentrates during roasting, the Hg will be retained as HgSO{sub 4} or HgSO{sub 4}-HgO at temperatures as high as 870K. 8 refs., 30 figs., 3 tabs.

  12. Isotopically controlled semiconductors

    SciTech Connect

    Haller, Eugene E.

    2006-06-19

    The following article is an edited transcript based on the Turnbull Lecture given by Eugene E. Haller at the 2005 Materials Research Society Fall Meeting in Boston on November 29, 2005. The David Turnbull Lectureship is awarded to recognize the career of a scientist who has made outstanding contributions to understanding materials phenomena and properties through research, writing, and lecturing, as exemplified by the life work of David Turnbull. Haller was named the 2005 David Turnbull Lecturer for his 'pioneering achievements and leadership in establishing the field of isotopically engineered semiconductors; for outstanding contributions to materials growth, doping and diffusion; and for excellence in lecturing, writing, and fostering international collaborations'. The scientific interest, increased availability, and technological promise of highly enriched isotopes have led to a sharp rise in the number of experimental and theoretical studies with isotopically controlled semiconductor crystals. This article reviews results obtained with isotopically controlled semiconductor bulk and thin-film heterostructures. Isotopic composition affects several properties such as phonon energies, band structure, and lattice constant in subtle, but, for their physical understanding, significant ways. Large isotope-related effects are observed for thermal conductivity in local vibrational modes of impurities and after neutron transmutation doping. Spectacularly sharp photoluminescence lines have been observed in ultrapure, isotopically enriched silicon crystals. Isotope multilayer structures are especially well suited for simultaneous self- and dopant-diffusion studies. The absence of any chemical, mechanical, or electrical driving forces makes possible the study of an ideal random-walk problem. Isotopically controlled semiconductors may find applications in quantum computing, nanoscience, and spintronics.

  13. Optical and TDPAC spectroscopy of Hg(II)-rubredoxin: model for a mononuclear tetrahedral [Hg(CysS)4]2- center. ISOLDE Collaboration.

    PubMed

    Faller, P; Ctortecka, B; Tröger, W; Butz, T; Vasák, M

    2000-06-01

    Rubredoxins possess a well-defined mononuclear tetrahedral tetrathiolate metal binding site, a feature exploited by several investigations to study the spectroscopic characteristics and the coordination chemistry of different metal ions at this binding site. In the present work, Hg(II)-substituted rubredoxin (Rd) from Desulfovibrio gigas has been studied by electronic absorption, circular dichroism (CD), magnetic circular dichroism (MCD), and time differential perturbed angular correlation of gamma-rays (TDPAC) spectroscopies. The TDPAC spectrum of 199mHg-Rd at pH 8 exhibits a prevailing nuclear quadrupole interaction (NQI) with a precession frequency of omega1=0.09 Grad/s and an asymmetry parameter eta=0, features characteristic of a slightly distorted tetrahedral tetrathiolate metal coordination, i.e, a HgCysS4 center. In addition, three minor populated NQIs have also been detected. They may represent a trigonal HgS3 (omega1=1.13 Grad/s, eta=0.21), a digonal HgS2 (omega1= 1.34 Grad/s, eta =0.20), and a digonal Hg(II) coordination (omega = 1.58 Grad/s, eta =0.18) with unidentified ligands. Since similar studies at pH 2.5 revealed a time-dependent increase of the HgCysS4 population, the low populated sites may represent intermediate Hg(II) complexes formed prior to the generation of the thermodynamically stable structure. The metal-induced absorption envelope of Hg-Rd reveals three distinct transitions with Gaussian-resolved maxima located at 230, 257, and 284 nm, which are paralleled by dichroic features in the corresponding difference CD spectrum of Hg(II)-Rd versus apo-Rd. Based on the optical electronegativity theory of J*rgensen, the lowest energy transition has been attributed to a CysS-Hg(II) charge-transfer excitation. The Td type of metal coordination in Hg-Rd is supported by the presence of an unresolved A-term with a negative lobe at 295 nm in the difference MCD spectrum. These results point to the usefulness of optical and TDPAC spectroscopies for

  14. ISOTOPE SEPARATING APPARATUS

    DOEpatents

    Kudravetz, M.K.; Greene, H.B.

    1958-09-16

    This patent relates to control systems for a calutron and, in particular, describes an electro-mechanical system for interrupting the collection of charged particles when the ratio between the two isotopes being receivcd deviates from a predetermined value. One embodiment of the invention includes means responsive to the ratio between two isotopes being received for opening a normally closed shutter over the receiver entrance when the isotope ratio is the desired value. In another form of the invention the collection operation is interrupted by changing the beam accelerating voltage to deflect the ion beam away from the receiver.

  15. Carbon isotope techniques

    SciTech Connect

    Coleman, D.C. ); Fry, B. )

    1991-01-01

    This book is a hands-on introduction to using carbon isotope tracers in experimental biology and ecology. It is a bench-top reference with protocols for the study of plants, animals, and soils. The {sup 11}C, {sup 12}C, {sup 13}C, and {sup 14}C carbon isotopes are considered and standard techniques are described by established authors. The compilation includes the following features: specific, well-established, user-oriented techniques; carbon cycles in plants, animals, soils, air, and water; isotopes in ecological research; examples and sample calculations.

  16. A metal exchange method for thiolate-protected tri-metal M1AgxAu24-x(SR)180 (M = Cd/Hg) nanoclusters

    NASA Astrophysics Data System (ADS)

    Yang, Sha; Wang, Shuxin; Jin, Shan; Chen, Shuang; Sheng, Hongting; Zhu, Manzhou

    2015-05-01

    We herein reported the first synthesis of tri-metallic M1AgxAu24-x(SR)180 (M = Cd/Hg) nanoclusters by a two-step metal exchange method. Optical spectra suggested that the second and third foreign metals could largely change the electronic structure of homogold Au25(SR)18- nanoclusters. This work also provides a novel way to find the doping site of some special metals (such as Cd), which can be done using silver as the isotope of gold.We herein reported the first synthesis of tri-metallic M1AgxAu24-x(SR)180 (M = Cd/Hg) nanoclusters by a two-step metal exchange method. Optical spectra suggested that the second and third foreign metals could largely change the electronic structure of homogold Au25(SR)18- nanoclusters. This work also provides a novel way to find the doping site of some special metals (such as Cd), which can be done using silver as the isotope of gold. Electronic supplementary information (ESI) available: Synthesis details and addition figures. See DOI: 10.1039/c5nr01965f

  17. Directional solidification of HgCdTe and HgZnTe in a transverse magnetic field

    NASA Technical Reports Server (NTRS)

    Su, Ching-Hua; Lehoczky, S. L.; Szofran, F. R.

    1991-01-01

    Hg(0.80)Cd(0.20)Te crystals were grown vertically in a transverse magnetic field by directional solidification. The effect of a magnetic field on the nature of fluid flow in the melts was investigated by measuring compositional variations along the axial and radial directions of the grown ingots. Magnetic field effects were shown to be significant over the entire field range employed (i.e., 2 to 5 kG). The axial compositional profiles (determined by precision density measurements) showed an abrupt decrease in the mole fraction of CdTe when the field was applied. Radial compositional mapping by IR transmission and X-ray energy dispersion spectrometry indicated that the solid-liquid interface evolved through three stages when the field was applied (i.e., from a radially symmetric concave interface to an off-center concave shape when the field was initially applied, then to a tilted plane, and, finally, to an off-center concave interface). The axial compositional profile of an Hg(0.84)Zn(0.16)Te ingot showed similar field effects.

  18. Mercury in stream water at five Czech catchments across a Hg and S deposition gradient

    USGS Publications Warehouse

    Navrátil, Tomáš; Shanley, James B.; Rohovec, Jan; Oulehle, Filip; Krám, Pavel; Matoušková, Šárka; Tesař, Miroslav; Hojdová, Maria

    2015-01-01

    The Czech Republic was heavily industrialized in the second half of the 20th century but the associated emissions of Hg and S from coal burning were significantly reduced since the 1990s. We studied dissolved (filtered) stream water mercury (Hg) and dissolved organic carbon (DOC) concentrations at five catchments with contrasting Hg and S deposition histories in the Bohemian part of the Czech Republic. The median filtered Hg concentrations of stream water samples collected in hydrological years 2012 and 2013 from the five sites varied by an order of magnitude from 1.3 to 18.0 ng L− 1. The Hg concentrations at individual catchments were strongly correlated with DOC concentrations r from 0.64 to 0.93 and with discharge r from 0.48 to 0.75. Annual export fluxes of filtered Hg from individual catchments ranged from 0.11 to 13.3 μg m− 2 yr− 1 and were highest at sites with the highest DOC export fluxes. However, the amount of Hg exported per unit DOC varied widely; the mean Hg/DOC ratio in stream water at the individual sites ranged from 0.28 to 0.90 ng mg− 1. The highest stream Hg/DOC ratios occurred at sites Pluhův Bor and Jezeří which both are in the heavily polluted Black Triangle area. Stream Hg/DOC was inversely related to mineral and total soil pool Hg/C across the five sites. We explain this pattern by greater soil Hg retention due to inhibition of soil organic matter decomposition at the sites with low stream Hg/DOC and/or by precipitation of a metacinnabar (HgS) phase. Thus mobilization of Hg into streams from forest soils likely depends on combined effects of organic matter decomposition dynamics and HgS-like phase precipitation, which were both affected by Hg and S deposition histories.

  19. MicroCT vs. Hg porosimetry: microporosity in commercial stones

    NASA Astrophysics Data System (ADS)

    Fusi, N.; Martinez-Martinez, J.; Barberini, V.; Galimberti, L.

    2009-04-01

    Decay of rocks, due both to extrinsic and intrinsic factors, can show up in several different forms, such as neoformation of minerals, decohesion of grains and/or crystals, magnification of previous defects, new discontinuities, etc. Intrinsic factors include the type of material, its properties and microstructure, in particular porosity and microporosity. Extrinsic factors relate to atmosphere and usage of the material itself. Rock degradation has several heavy consequences for commercial stones, such as increase of permeability, loss of material, loss of mechanical strength; these consequences are of crucial importance for conservation of historical buildings. Aim of this study is to compare microporosity of some massive commercial stones by means of X ray microtomography, a non destructive technique, and Hg porosimetry. Nine of the most used Spanish limestones and dolostones have been analysed. The lithotypes have been chosen for their homogeneous mineralogical composition (calcitic or dolomitic) and for their low porosity; some of them have been widely used in Spain for historical buildings. Different lithotypes have been described in thin section: Ambarino (A) and Beige Serpiente (BS): brecciated dolostone, composed by microcrystalline dolomitic clasts, in a dolomitic and/or calcitic microcrystalline matrix. Amarillo Triana (AT): yellow dolomitic marble, with fissures filled up by calcite and Fe oxides. Blanco Alconera (BA): a white-pink homogeneous limestone, with veins. Blanco Tranco (BT): a homogeneous white calcitic marble, without any fissures and/or fractures. Crema Valencia (CV): a pinkish limestone, characterized by abundant stilolythes, filled mainly by quartz (80%) and kaolin (11%). Gris Macael (GM): a calcitic marble wiht darker and lighter beds, conferring a strong anisotropy. Rojo Cehegin (RC): a red fossiliferous limestone with white calcitic veins. Travertino Blanco (TB): a massive white calcitic travertine. Prismatic samples of about 2x1x1 cm

  20. Mercury (Hg) accumulation in terrestrial carbon (C) reservoirs: magnitude, spatial patterns, fate upon C losses, and implications of global change

    NASA Astrophysics Data System (ADS)

    Obrist, D.; Johnson, D. W.; Lindberg, S. E.; Luo, Y.

    2012-04-01

    Terrestrial ecosystems are strong natural reservoirs that retain the bulk of atmospheric Hg deposition. As a result, a long-term legacy of past and present Hg pollution is sequestered in surface litter and soil pools. Hg shows a particular affinity to—and hence tends to accumulate in—terrestrial organic C. We present a summary of a comprehensive five-year investigation where we quantified: (i) relationships between Hg and C across 14 forests sites to assess the affinity of Hg to C accumulation across spatial scales; (ii) the degree to which C determines net retention and spatial accumulation of Hg; (iii) the fate of Hg upon losses of C, including losses though wildfires and mineralization; (iv) the coupling of gaseous Hg losses to CO2 respiration; and (v) the potential sensitivity of climate-change induced changes in C on terrestrial Hg sequestration. Results show that continental-scale spatial distribution of Hg in soils and litter is strongly related to C, and that old terrestrial C pools (as determined by C/N ratios) are particularly prone to Hg enrichment. The correlation of Hg and C is likely responsible for increasing Hg levels (concentrations and pools of total Hg, as well as methylated Hg) with higher latitude, which we attribute to a legacy of Hg sequestration in C-rich layers of northern ecosystems. Experimental studies and field observations to address fate of Hg sequestered in organic C show that: (i) fires leads to up-to-complete Hg losses in either gaseous elemental or particulate-bound form; (ii) litter decomposition also leads to evasion losses of Hg in the range of 50% of initial Hg, but little Hg is subject to runoff as dissolved Hg; (iii) soils effectively retain Hg with only about 3% of Hg subject to volatilization upon C loss during respiration; (iv) no links between CO2 and gaseous Hg concentrations are observed in soil depth profiles in the field, indicating that fate and movement of gaseous Hg is decoupled from that of CO2. We calculate