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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. 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.

  3. 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

  4. 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.

  5. Equilibrium mercury isotope fractionation between dissolved Hg(II) species and thiol-bound Hg.

    PubMed

    Wiederhold, Jan G; Cramer, Christopher J; Daniel, Kelly; Infante, Ivan; Bourdon, Bernard; Kretzschmar, Ruben

    2010-06-01

    Stable Hg isotope ratios provide a new tool to trace environmental Hg cycling. Thiols (-SH) are the dominant Hg-binding groups in natural organic matter. Here, we report experimental and computational results on equilibrium Hg isotope fractionation between dissolved Hg(II) species and thiol-bound Hg. Hg(II) chloride and nitrate solutions were equilibrated in parallel batches with varying amounts of thiol resin resulting in different fractions of thiol-bound and free Hg. Mercury isotope ratios in both fractions were analyzed by multiple collector inductively coupled plasma mass spectrometry (MC-ICPMS). Theoretical equilibrium Hg isotope effects by mass-dependent fractionation (MDF) and nuclear volume fractionation (NVF) were calculated for 14 relevant Hg(II) species. The experimental data revealed that thiol-bound Hg was enriched in light Hg isotopes by 0.53 per thousand and 0.62 per thousand (delta(202)Hg) relative to HgCl(2) and Hg(OH)(2), respectively. The computational results were in excellent agreement with the experimental data indicating that a combination of MDF and NVF was responsible for the observed Hg isotope fractionation. Small mass-independent fractionation (MIF) effects (<0.1 per thousand) were observed representing one of the first experimental evidences for MIF of Hg isotopes by NVF. Our results indicate that significant equilibrium Hg isotope fractionation can occur without redox transition, and that NVF must be considered in addition to MDF to explain Hg isotope variations.

  6. Evolution of the E(1/2{sub 1}{sup +})-E(3/2{sub 1}{sup +}) energy spacing in odd-mass K, Cl, and P isotopes for N=20-28

    SciTech Connect

    Gade, A.; Brown, B. A.; Campbell, C. M.; Church, J. A.; Dinca, D. C.; Glasmacher, T.; Terry, J. R.; Yurkewicz, K. L.; Zwahlen, H.; Bazin, D.; Hu, Z.; Mueller, W. F.; Enders, J.; Horoi, M.; Kemper, K. W.; Roeder, B. T.; Otsuka, T.; Riley, L. A.; Suzuki, T.

    2006-09-15

    The energy of the first excited state in the neutron-rich N=28 nucleus {sup 45}Cl has been established via in-beam {gamma}-ray spectroscopy following proton removal. This energy value completes the systematics of the E(1/2{sub 1}{sup +})-E(3/2{sub 1}{sup +}) level spacing in odd-mass K, Cl, and P isotopes for N=20-28. The results are discussed in the framework of shell-model calculations in the sd-fp model space. The contribution of the central, spin-orbit, and tensor components is discussed from a calculation based on a proton single-hole spectrum from G-matrix and {pi}+{rho} meson exchange potentials. A composite model for the proton 0d{sub 3/2}-1s{sub 1/2} single-particle energy shift is presented.

  7. 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

  8. 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.

  9. Hg stable isotope analysis by the double-spike method.

    PubMed

    Mead, Chris; Johnson, Thomas M

    2010-06-01

    Recent publications suggest great potential for analysis of Hg stable isotope abundances to elucidate sources and/or chemical processes that control the environmental impact of mercury. We have developed a new MC-ICP-MS method for analysis of mercury isotope ratios using the double-spike approach, in which a solution containing enriched (196)Hg and (204)Hg is mixed with samples and provides a means to correct for instrumental mass bias and most isotopic fractionation that may occur during sample preparation and introduction into the instrument. Large amounts of isotopic fractionation induced by sample preparation and introduction into the instrument (e.g., by batch reactors) are corrected for. This may greatly enhance various Hg pre-concentration methods by correcting for minor fractionation that may occur during preparation and removing the need to demonstrate 100% recovery. Current precision, when ratios are normalized to the daily average, is 0.06 per thousand, 0.06 per thousand, 0.05 per thousand, and 0.05 per thousand (2sigma) for (202)Hg/(198)Hg, (201)Hg/(198)Hg, (200)Hg/(198)Hg, and (199)Hg/(198)Hg, respectively. This is slightly better than previously published methods. Additionally, this precision was attained despite the presence of large amounts of other Hg isotopes (e.g., 5.0% atom percent (198)Hg) in the spike solution; substantially better precision could be achieved if purer (196)Hg were used.

  10. 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

  11. Odd isotope deficits in atmospheric Hg measured in lichens.

    PubMed

    Carignan, Jean; Estrade, Nicolas; Sonke, Jeroen E; Donard, Olivier F X

    2009-08-01

    Redox reactions govern mercury (Hg) concentrations in the atmosphere because fluxes (emissions and deposition), and residence times, are largely controlled by Hg speciation. Recent work on aquatic Hg photoreduction suggested that this reaction produces non-mass dependent fractionation (NMF) and that residual aquatic Hg(II)is characterized by positive delta199Hg and delta201Hg anomalies. Here, we show that atmospheric Hg accumulated in lichens is characterized by NMF with negative delta199Hg and delta201Hg values (-0.3 to -1 per thousand), making the atmosphere and the aquatic environment complementary reservoirs regarding photoreduction and NMF of Hg isotopes. Because few other reactions than aquatic Hg photoreduction induce NMF, photochemical reduction appears to be a key pathway in the global Hg cycle. Based on a NMF isotope mass balance, direct anthropogenic emissions may account for only 50 +/- 10% of atmospheric Hg deposition in an urban area of NE France. Furthermore, isotopic anomalies found in several polluted soils and sediments strongly suggests that an important part of Hg in these samples was affected by photoreactions and has cycled through the atmosphere before being stored in the geological environment. Thus, mercury isotopic anomalies measured in environmental samples may be used to trace and quantify the contribution of source emissions.

  12. 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

  13. 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

  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. 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.

  16. 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.

  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. 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.

  19. Tracing historical trends of Hg in the Mississippi River using Hg concentrations and Hg isotopic compositions in a lake sediment core, Lake Whittington, Mississippi, USA

    USGS Publications Warehouse

    Gray, John E.; Van Metre, Peter C.; Pribil, Michael J.; Horowitz, Arthur J.

    2015-01-01

    Concentrations and isotopic compositions of mercury (Hg) in a sediment core collected from Lake Whittington, an oxbow lake on the Lower Mississippi River, were used to evaluate historical sources of Hg in the Mississippi River basin. Sediment Hg concentrations in the Lake Whittington core have a large 10-15 y peak centered on the 1960s, with a maximum enrichment factor relative to Hg in the core of 4.8 in 1966. The Hg concentration profile indicates a different Hg source history than seen in most historical reconstructions of Hg loading. The timing of the peak is consistent with large releases of Hg from Oak Ridge National Laboratory (ORNL), primarily in the late 1950s and 1960s. Mercury was used in a lithiumisotope separation process by ORNL and an estimated 128Mg (megagrams) of Hgwas discharged to a local stream that flows into the Tennessee River and, eventually, the Mississippi River. Mass balance analyses of Hg concentrations and isotopic compositions in the Lake Whittington core fit a binary mixing model with a Hg-rich upstream source contributing about 70% of the Hg to Lake Whittington at the height of the Hg peak in 1966. This upstream Hg source is isotopically similar to Hg isotope compositions of stream sediment collected downstream near ORNL. It is estimated that about one-half of the Hg released from the ORNL potentially reached the LowerMississippi River basin in the 1960s, suggesting considerable downstream transport of Hg. It is also possible that upstream urban and industrial sources contributed some proportion of Hg to Lake Whittington in the 1960s and 1970s.

  20. 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.

  1. Solution speciation controls mercury isotope fractionation of Hg(II) sorption to goethite.

    PubMed

    Jiskra, Martin; Wiederhold, Jan G; Bourdon, Bernard; Kretzschmar, Ruben

    2012-06-19

    The application of Hg isotope signatures as tracers for environmental Hg cycling requires the determination of isotope fractionation factors and mechanisms for individual processes. Here, we investigated Hg isotope fractionation of Hg(II) sorption to goethite in batch systems under different experimental conditions. We observed a mass-dependent enrichment of light Hg isotopes on the goethite surface relative to dissolved Hg (ε(202)Hg of -0.30‰ to -0.44‰) which was independent of the pH, chloride and sulfate concentration, type of surface complex, and equilibration time. Based on previous theoretical equilibrium fractionation factors, we propose that Hg isotope fractionation of Hg(II) sorption to goethite is controlled by an equilibrium isotope effect between Hg(II) solution species, expressed on the mineral surface by the adsorption of the cationic solution species. In contrast, the formation of outer-sphere complexes and subsequent conformation changes to different inner-sphere complexes appeared to have insignificant effects on the observed isotope fractionation. Our findings emphasize the importance of solution speciation in metal isotope sorption studies and suggest that the dissolved Hg(II) pool in soils and sediments, which is the most mobile and bioavailable, should be isotopically heavy, as light Hg isotopes are preferentially sequestered during binding to both mineral phases and natural organic matter.

  2. 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

  3. 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.

  4. 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.

  5. Absence of magnetic isotope fractionation for Hg during dark biological processes: experimental evidence and theoretical considerations

    NASA Astrophysics Data System (ADS)

    Kritee, K.; Barkay, T.; Blum, J. D.

    2008-12-01

    The complex biogeochemistry and toxicity of Hg compounds warrants the search for new strategies that could be used to decipher the relative importance of its multiple abiotic and microbial transformations in ecosystems. In this regard, the emerging mercury isotope systematics is showing tremendous potential. We have studied the extent of fractionation of Hg stable isotopes during 1) degradation of MMHg and 2) Hg(II) reduction by multiple Hg(II) reducing strains, and irrespective of the extent of mass dependent fractionation (MDF) we did not observe any mass independent fractionation (MIF) of Hg isotopes. On the other hand, photo-chemical degradation of MMHg and reduction of Hg(II) cause a very high extent of MIF (Bergquist and Blum, 2007). Because there are many more unexamined microbial processes that influence Hg cycling in addition to the microbial transformations examined experimentally, and because some of these (e.g., oxidative degradation of MMHg) are not amenable to pure culture studies, a crucial question facing Hg biogeochemists is "Can microbial/biological processes cause MIF or are MIF signatures unique to photo- chemical transformations?" Based on the high spin orbit coupling in Hg compounds, the low likelihood of suppression of spin orbit coupling during dark biological processes, and the nature of known enzyme-Hg and microbe-Hg interactions, we suggest that the nuclear spin dependent MIF is unlikely to occur during dark biological processes. Because of the important implications of the absence of MIF during biological processes on Hg isotope systematics, we will also discuss experimental strategies that could be used to confirm this suggestion (Kritee et al., 2008). Bergquist B. A. and Blum J. D. (2007) Mass-dependent and mass-independent fractionation of Hg isotopes by photo-reduction in aquatic systems. Science 318(5849), 417-420. Kritee K., Barkay T., and Blum J. D. (2008) Mass dependent mercury stable isotope fractionation during microbial

  6. 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.

  7. 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

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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

  13. 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.

  14. 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.

  15. 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

  16. 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.

  17. 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.

  18. 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.

  19. 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

  20. Photon scattering experiments on the quasistable, odd-odd mass nucleus Lu176

    NASA Astrophysics Data System (ADS)

    Walter, S.; Stedile, F.; Carroll, J. J.; Fransen, C.; Friessner, G.; Hollmann, N.; von Garrel, H.; Jolie, J.; Karg, O.; Käppeler, F.; Kneissl, U.; Kohstall, C.; von Neumann-Cosel, P.; Linnemann, A.; Mücher, D.; Pietralla, N.; Pitz, H. H.; Rusev, G.; Scheck, M.; Scholl, C.; Schwengner, R.; Werner, V.; Wisshak, K.

    2007-03-01

    The quasistable odd-odd-mass nucleus Lu176 is of special interest in nuclear structure physics and, above all, in nuclear astrophysics. Systematic photon scattering experiments have been performed at the bremsstrahlung facility of the 4.3-MV Stuttgart Dynamitron accelerator with bremsstrahlung end-point energies of 2.3 and 3.1 MeV to determine the low-energy dipole strength distribution in the s-only isotope Lu176. The main goal was to pin down possible intermediate states (IS) for the photoactivation of the short-lived 123-keV isomer, which is the key process determining the effective lifetime of Lu176 in a stellar photon bath and hence for the use of this isotope as a stellar chronometer. Using an enriched sample, 29 transitions ascribed to Lu176 were detected below 2.9-MeV excitation energy. The corresponding excitation strengths were determined. For the previously proposed lowest IS at 839 keV, an upper limit for the excitation strength corresponding to a lifetime of τ⩾ 1.5 ps can be given. Astrophysical consequences, also in view of new Stuttgart photoactivation experiments, are discussed. The fragmentation of the dipole strength is compared to those in neighboring even-even and odd-even nuclei.

  1. Identification of contamination in a lake sediment core using Hg and Pb isotopic compositions, Lake Ballinger, Washington, USA

    USGS Publications Warehouse

    Gray, John E.; Pribil, Michael J.; Van Metre, Peter C.; Borrok, David M.; Thapalia, Anita

    2013-01-01

    Concentrations and isotopic compositions of Hg and Pb were measured in a sediment core collected from Lake Ballinger, near Seattle, Washington, USA. Lake Ballinger has been affected by input of metal contaminants emitted from the Tacoma smelter, which operated from 1887 to 1986 and was located about 53 km south of the lake. Concentrations and loadings of Hg and Pb in Lake Ballinger increased by as much as three orders of magnitude during the period of smelting as compared to the pre-smelting period. Concentrations and loadings of Hg and Pb then decreased by about 55% and 75%, respectively, after smelting ended. Isotopic compositions of Hg changed considerably during the period of smelting (δ202Hg = −2.29‰ to −0.38‰, mean −1.23‰, n = 9) compared to the pre-smelting period (δ202Hg = −2.91‰ to −2.50‰, mean −2.75‰, n = 4). Variations were also observed in 206Pb/207Pb and 208Pb/207Pb isotopic compositions during these periods. Data for Δ199Hg and Δ201Hg indicate mass independent fractionation (MIF) of Hg isotopes in Lake Ballinger sediment during the smelting and post-smelting period and suggest MIF in the ore smelted, during the smelting process, or chemical modification at some point in the past. Negative values for Δ199Hg and Δ201Hg for the pre-smelting period are similar to those previously reported for soil, peat, and lichen, likely suggesting some component of atmospheric Hg. Variations in the concentrations and isotopic compositions of Hg and Pb were useful in tracing contaminant sources and the understanding of the depositional history of sedimentation in Lake Ballinger.

  2. COMPARISON OF SELF-CONSISTENT SKYRME AND GOGNY CALCULATIONS FOR LIGHT Hg ISOTOPES

    SciTech Connect

    Warda, Michal J; Prochniak, L.; Staszczak, Andrzej

    2010-01-01

    The ground-state properties of neutron-deficient Hg isotopes have been investigated by the constrained self-consistent Hartree-Fock-Bogoliubov approach with the Skyrme and Gogny effective forces. In the case of the Skyrme interaction we have also applied the Hartree-Fock+BCS model with the state-dependent {delta}-pairing interaction. Potential energy surfaces and pairing properties have been compared for the both types of forces.

  3. 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.

  4. 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

  5. Determination of compound-specific Hg isotope ratios from transient signals using gas chromatography coupled to multicollector inductively coupled plasma mass spectrometry (MC-ICP/MS).

    PubMed

    Dzurko, Mark; Foucher, Delphine; Hintelmann, Holger

    2009-01-01

    MeHg and inorganic Hg compounds were measured in aqueous media for isotope ratio analysis using aqueous phase derivatization, followed by purge-and-trap preconcentration. Compound-specific isotope ratio measurements were performed by gas chromatography interfaced to MC-ICP/MS. Several methods of calculating isotope ratios were evaluated for their precision and accuracy and compared with conventional continuous flow cold vapor measurements. An apparent fractionation of Hg isotopes was observed during the GC elution process for all isotope pairs, which necessitated integration of signals prior to the isotope ratio calculation. A newly developed average peak ratio method yielded the most accurate isotope ratio in relation to values obtained by a continuous flow technique and the best reproducibility. Compound-specific isotope ratios obtained after GC separation were statistically not different from ratios measured by continuous flow cold vapor measurements. Typical external uncertainties were 0.16 per thousand RSD (n = 8) for the (202)Hg(/198)Hg ratio of MeHg and 0.18 per thousand RSD for the same ratio in inorganic Hg using the optimized operating conditions. Using a newly developed reference standard addition method, the isotopic composition of inorganic Hg and MeHg synthesized from this inorganic Hg was measured in the same run, obtaining a value of delta (202)Hg = -1.49 +/- 0.47 (2SD; n = 10). For optimum performance a minimum mass of 2 ng per Hg species should be introduced onto the column. PMID:18488203

  6. 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.

  7. 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.

  8. 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

  9. Evaluating the role of re-adsorption of dissolved Hg2+ during cinnabar dissolution using isotope tracer technique

    DOE PAGES

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

    2016-06-02

    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-adsorbedmore » Hg on cinnabar surface via the reduction in spiked 202Hg2+. By adopting the developed method, it was found that the released Hg for trials purged with oxygen could reach several hundred g L–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. Lastly, 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.« less

  10. 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.

  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. The reaction of Hg(6 3P1)+H2, D2, and HD: Product rotational and vibrational distributions; isotope effects

    NASA Astrophysics Data System (ADS)

    Bras, N.; Jeannet, J. C.; Perrin, D.

    1987-07-01

    The initial vibrational and rotational state distributions of HgH and HgD products of Hg(6 3P1)+H2, D2, and HD have been determined. No isotope effect was observed for the vibrationless molecules or for HgH(v=1) but this effect appears for vibrationally excited HgD. The relative yields of the various reactions are reported for each vibrational level. In the reaction with HD, HgD is preferentially produced: [HgD]/[HgH]≂6.7.

  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. Using mercury isotopes to understand the bioaccumulation of Hg in the subtropical Pearl River Estuary, South China.

    PubMed

    Yin, Runsheng; Feng, Xinbin; Zhang, Junjun; Pan, Ke; Wang, Wenxiong; Li, Xiangdong

    2016-03-01

    Coastal and estuarine regions are important areas of mercury pollution. Therefore, it is important to properly characterize the sources and bioaccumulation processes of mercury in these regions. Here, we present mercury stable isotopic compositions in 18 species of wild marine fish collected from the Pearl River Estuary (PRE), south China. Our results showed variations in mass-independent fractionation (Δ(199)Hg: +0.05 ± 0.10‰ to +0.59 ± 0.30‰) with a Δ(199)Hg/Δ(201)Hg of ∼1.26, suggesting that aqueous MeHg underwent photo-degradation prior to incorporation into the food chain. For the results, we discovered small but significant differences of Δ(199)Hg values among herbivorous, demersal, and carnivorous fish, indicating that different feeding guilds of fish may have incorporated MeHg with various degrees of photo-demethylation. The consistent mercury isotope compositions between fish feeding habitat and mercury sources in the estuary provide potentially important findings on the transformation and bioaccumulation of this toxic metal in subtropical coastal environments. PMID:26766353

  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.

  16. Pb-Zn-Cd-Hg multi isotopic characterization of the Loire River Basin, France

    NASA Astrophysics Data System (ADS)

    Millot, R.; Widory, D.; Innocent, C.; Guerrot, C.; Bourrain, X.; Johnson, T. M.

    2012-12-01

    The contribution of human activities such as industries, agriculture and domestic inputs, becomes more and more significant in the chemical composition (major ions and pollutants such as metals) of the dissolved load of rivers. Furthermore, this influence can also be evidenced in the suspended solid matter known to play an important role in the transport of heavy metals through river systems. Human factors act as a supplementary key process. Therefore the mass-balance for the budget of catchments and river basins include anthropogenic disturbances. The Loire River in central France is approximately 1010 km long and drains an area of 117,800 km2. Initially, the Loire upstream flows in a south to north direction originating in the Massif Central, and continues up to the city of Orléans, 650 km from the source. In the upper basin, the bedrock is old plutonic rock overlain by much younger volcanic rocks. The Loire River then follows a general east to west direction to the Atlantic Ocean. The intermediate basin includes three major tributaries flowing into the Loire River from the left bank: the Cher, the Indre and the Vienne rivers; the main stream flows westward and its valley stretches toward the Atlantic Ocean. Here, the Loire River drains the sedimentary series of the Paris Basin, mainly carbonate deposits. The lower Loire basin drains pre-Mesozoic basement of the Armorican Massif and its overlying Mesozoic to Cenozoic sedimentary deposits. The Loire River is one of the main European riverine inputs to the Atlantic ocean. Here we are reporting concentration and isotope data for heavy metals Zn-Cd-Pb-Hg in river waters and suspended sediments from the Loire River Basin. In addition, we also report concentration and isotope data for these metals for the different industrial sources within the Loire Basin, as well as data for biota samples such as mussels and oysters from the Bay of Biscay and North Brittany. These organisms are known to be natural accumulators of

  17. 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.

  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. 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.

  20. Effect of core polarization on magnetic dipole moments in deformed odd-mass nuclei

    NASA Astrophysics Data System (ADS)

    Bonneau, L.; Minkov, N.; Duc, Dao Duy; Quentin, P.; Bartel, J.

    2015-05-01

    Magnetic properties of deformed odd-mass nuclei are studied within a nonrelativistic mean-field-plus-pairing approach, namely the Skyrme-Hartree-Fock-BCS approach with self-consistent blocking. For an odd number of nucleons these approaches lead to the breaking of the time-reversal invariance. The deviation from the Schmidt values of the isoscalar magnetic dipole moment is known to result from a subtle balance between core-polarization effects and meson-exchange current effects. However, the former are usually calculated in the random phase approximation without time-reversal symmetry breaking at the mean-field level. In this work we show that if one takes into account this symmetry breaking already in the mean-field solution, the correction from core polarization yields a significant contribution to the empirical quenching of the spin gyromagnetic ratios as compared to the free values in deformed odd-mass nuclei. Moreover, we calculate magnetic dipole moments in the Bohr and Mottelson unified-model description with self-consistent blocked mean-field intrinsic states. The obtained results in the A ˜100 and A ˜180 mass regions as well as for three actinide nuclei compare favorably with experimental data.

  1. Shape coexistence in the neutron-deficient even-even (182-188)Hg isotopes studied via coulomb excitation.

    PubMed

    Bree, N; Wrzosek-Lipska, K; Petts, A; Andreyev, A; Bastin, B; Bender, M; Blazhev, A; Bruyneel, B; Butler, P A; Butterworth, J; Carpenter, M P; Cederkäll, J; Clément, E; Cocolios, T E; Deacon, A; Diriken, J; Ekström, A; Fitzpatrick, C; Fraile, L M; Fransen, Ch; Freeman, S J; Gaffney, L P; García-Ramos, J E; Geibel, K; Gernhäuser, R; Grahn, T; Guttormsen, M; Hadinia, B; Hadyńska-Kle K, K; Hass, M; Heenen, P-H; Herzberg, R-D; Hess, H; Heyde, K; Huyse, M; Ivanov, O; Jenkins, D G; Julin, R; Kesteloot, N; Kröll, Th; Krücken, R; Larsen, A C; Lutter, R; Marley, P; Napiorkowski, P J; Orlandi, R; Page, R D; Pakarinen, J; Patronis, N; Peura, P J; Piselli, E; Rahkila, P; Rapisarda, E; Reiter, P; Robinson, A P; Scheck, M; Siem, S; Singh Chakkal, K; Smith, J F; Srebrny, J; Stefanescu, I; Tveten, G M; Van Duppen, P; Van de Walle, J; Voulot, D; Warr, N; Wenander, F; Wiens, A; Wood, J L; Zielińska, M

    2014-04-25

    Coulomb-excitation experiments to study electromagnetic properties of radioactive even-even Hg isotopes were performed with 2.85  MeV/nucleon mercury beams from REX-ISOLDE. Magnitudes and relative signs of the reduced E2 matrix elements that couple the ground state and low-lying excited states in Hg182-188 were extracted. Information on the deformation of the ground and the first excited 0+ states was deduced using the quadrupole sum rules approach. Results show that the ground state is slightly deformed and of oblate nature, while a larger deformation for the excited 0+ state was noted in Hg182,184. The results are compared to beyond mean field and interacting-boson based models and interpreted within a two-state mixing model. Partial agreement with the model calculations was obtained. The presence of two different structures in the light even-mass mercury isotopes that coexist at low excitation energy is firmly established.

  2. Shape Coexistence in the Neutron-Deficient Even-Even Hg182-188 Isotopes Studied via Coulomb Excitation

    NASA Astrophysics Data System (ADS)

    Bree, N.; Wrzosek-Lipska, K.; Petts, A.; Andreyev, A.; Bastin, B.; Bender, M.; Blazhev, A.; Bruyneel, B.; Butler, P. A.; Butterworth, J.; Carpenter, M. P.; Cederkäll, J.; Clément, E.; Cocolios, T. E.; Deacon, A.; Diriken, J.; Ekström, A.; Fitzpatrick, C.; Fraile, L. M.; Fransen, Ch.; Freeman, S. J.; Gaffney, L. P.; García-Ramos, J. E.; Geibel, K.; Gernhäuser, R.; Grahn, T.; Guttormsen, M.; Hadinia, B.; Hadyńska-KleÂķ, K.; Hass, M.; Heenen, P.-H.; Herzberg, R.-D.; Hess, H.; Heyde, K.; Huyse, M.; Ivanov, O.; Jenkins, D. G.; Julin, R.; Kesteloot, N.; Kröll, Th.; Krücken, R.; Larsen, A. C.; Lutter, R.; Marley, P.; Napiorkowski, P. J.; Orlandi, R.; Page, R. D.; Pakarinen, J.; Patronis, N.; Peura, P. J.; Piselli, E.; Rahkila, P.; Rapisarda, E.; Reiter, P.; Robinson, A. P.; Scheck, M.; Siem, S.; Singh Chakkal, K.; Smith, J. F.; Srebrny, J.; Stefanescu, I.; Tveten, G. M.; Van Duppen, P.; Van de Walle, J.; Voulot, D.; Warr, N.; Wenander, F.; Wiens, A.; Wood, J. L.; Zielińska, M.

    2014-04-01

    Coulomb-excitation experiments to study electromagnetic properties of radioactive even-even Hg isotopes were performed with 2.85 MeV/nucleon mercury beams from REX-ISOLDE. Magnitudes and relative signs of the reduced E2 matrix elements that couple the ground state and low-lying excited states in Hg182-188 were extracted. Information on the deformation of the ground and the first excited 0+ states was deduced using the quadrupole sum rules approach. Results show that the ground state is slightly deformed and of oblate nature, while a larger deformation for the excited 0+ state was noted in Hg182,184. The results are compared to beyond mean field and interacting-boson based models and interpreted within a two-state mixing model. Partial agreement with the model calculations was obtained. The presence of two different structures in the light even-mass mercury isotopes that coexist at low excitation energy is firmly established.

  3. Shape coexistence in the neutron-deficient even-even (182-188)Hg isotopes studied via coulomb excitation.

    PubMed

    Bree, N; Wrzosek-Lipska, K; Petts, A; Andreyev, A; Bastin, B; Bender, M; Blazhev, A; Bruyneel, B; Butler, P A; Butterworth, J; Carpenter, M P; Cederkäll, J; Clément, E; Cocolios, T E; Deacon, A; Diriken, J; Ekström, A; Fitzpatrick, C; Fraile, L M; Fransen, Ch; Freeman, S J; Gaffney, L P; García-Ramos, J E; Geibel, K; Gernhäuser, R; Grahn, T; Guttormsen, M; Hadinia, B; Hadyńska-Kle K, K; Hass, M; Heenen, P-H; Herzberg, R-D; Hess, H; Heyde, K; Huyse, M; Ivanov, O; Jenkins, D G; Julin, R; Kesteloot, N; Kröll, Th; Krücken, R; Larsen, A C; Lutter, R; Marley, P; Napiorkowski, P J; Orlandi, R; Page, R D; Pakarinen, J; Patronis, N; Peura, P J; Piselli, E; Rahkila, P; Rapisarda, E; Reiter, P; Robinson, A P; Scheck, M; Siem, S; Singh Chakkal, K; Smith, J F; Srebrny, J; Stefanescu, I; Tveten, G M; Van Duppen, P; Van de Walle, J; Voulot, D; Warr, N; Wenander, F; Wiens, A; Wood, J L; Zielińska, M

    2014-04-25

    Coulomb-excitation experiments to study electromagnetic properties of radioactive even-even Hg isotopes were performed with 2.85  MeV/nucleon mercury beams from REX-ISOLDE. Magnitudes and relative signs of the reduced E2 matrix elements that couple the ground state and low-lying excited states in Hg182-188 were extracted. Information on the deformation of the ground and the first excited 0+ states was deduced using the quadrupole sum rules approach. Results show that the ground state is slightly deformed and of oblate nature, while a larger deformation for the excited 0+ state was noted in Hg182,184. The results are compared to beyond mean field and interacting-boson based models and interpreted within a two-state mixing model. Partial agreement with the model calculations was obtained. The presence of two different structures in the light even-mass mercury isotopes that coexist at low excitation energy is firmly established. PMID:24815644

  4. Fragmentation of low-lying dipole strength in the odd-mass nucleus 133Cs

    NASA Astrophysics Data System (ADS)

    Besserer, J.; Beck, O.; von Brentano, P.; Eckert, T.; Herzberg, R.-D.; Jäger, D.; Kneissl, U.; Margraf, J.; Maser, H.; Nord, A.; Pietralla, N.; Pitz, H. H.; Zilges, A.

    1997-09-01

    The fragmentation of low-lying dipole strength in the odd-mass nucleus 133Cs has been investigated in nuclear resonance fluorescence (NRF) experiments performed at the bremsstrahlung beam of the Stuttgart Dynamitron accelerator at an end-point energy of 4.1 MeV. In the excitation energy range 2.3 - 3.7 MeV in total 22 new dipole excitations were observed. From the high-resolution γ-ray spectra measured by three high-efficiency Ge detectors the reduced excitation probabilities B(E1)↑ or B(M1)↑ were deduced. The fragmentation and absolute total strengths of the detected dipole excitations are compared with results for the neighboring even-even, γ-soft nucleus 134Ba, where both, rather strong scissors mode-like M1 and two-phonon E1 excitations are known from recent NRF experiments.

  5. A model for quasi-parity-doublet spectra in odd-mass nuclei

    NASA Astrophysics Data System (ADS)

    Minkov, Nikolay

    2013-05-01

    A model of a quadrupole-octupole vibrating and rotating core plus a particle is proposed to describe and classify the quasi-parity-doublet spectra in odd-mass nuclei. The yrast levels are described as low-energy rotation-vibration modes built on the ground state. The non-yrast split parity-doublet sequences are considered as higher-energy rotation-vibration modes coupled to one-quasi-particle states. The even-even core is considered within the model of a coherent quadrupole-octupole motion, while the odd nucleon is described within the reflection-asymmetric deformed shell model with pairing interaction. The Coriolis decoupling and K-mixing interactions are calculated microscopically through a parity projection of the single-particle wave function. The unified model scheme was tested on the yrast and non-yrast quasi-parity-doublet spectra in the nuclei 223Ra and 221Fr.

  6. Kinetics of Hg(II) exchange between organic ligands, goethite, and natural organic matter studied with an enriched stable isotope approach.

    PubMed

    Jiskra, Martin; Saile, Damian; Wiederhold, Jan G; Bourdon, Bernard; Björn, Erik; Kretzschmar, Ruben

    2014-11-18

    The mobility and bioavailability of toxic Hg(II) in the environment strongly depends on its interactions with natural organic matter (NOM) and mineral surfaces. Using an enriched stable isotope approach, we investigated the exchange of Hg(II) between dissolved species (inorganically complexed or cysteine-, EDTA-, or NOM-bound) and solid-bound Hg(II) (carboxyl-/thiol-resin or goethite) over 30 days under constant conditions (pH, Hg and ligand concentrations). The Hg(II)-exchange was initially fast, followed by a slower phase, and depended on the properties of the dissolved ligands and sorbents. The results were described by a kinetic model allowing the simultaneous determination of adsorption and desorption rate coefficients. The time scales required to reach equilibrium with the carboxyl-resin varied greatly from 1.2 days for Hg(OH)2 to 16 days for Hg(II)-cysteine complexes and approximately 250 days for EDTA-bound Hg(II). Other experiments could not be described by an equilibrium model, suggesting that a significant fraction of total-bound Hg was present in a non-exchangeable form (thiol-resin and NOM: 53-58%; goethite: 22-29%). Based on the slow and incomplete exchange of Hg(II) described in this study, we suggest that kinetic effects must be considered to a greater extent in the assessment of the fate of Hg in the environment and the design of experimental studies, for example, for stability constant determination or metal isotope fractionation during sorption.

  7. Low-lying dipole excitations in the heavy, odd-mass nucleus 181Ta

    NASA Astrophysics Data System (ADS)

    Wolpert, A.; Beck, O.; Belic, D.; Besserer, J.; von Brentano, P.; Eckert, T.; Fransen, C.; Herzberg, R.-D.; Kneissl, U.; Margraf, J.; Maser, H.; Nord, A.; Pietralla, N.; Pitz, H. H.

    1998-08-01

    The strength distribution of low-lying dipole excitations in the heavy odd-mass nucleus 181Ta was studied in nuclear resonance fluorescence experiments performed at the bremsstrahlung beam of the Stuttgart 4.3 MV Dynamitron accelerator. To increase the detection sensitivity in the whole range of excitation energies between 1.8 and 4 MeV two measurements were carried out at different bremsstrahlung end-point energies of 2.7 and 4.1 MeV using two large-volume HPGe detectors of a relative efficiency of 100%. Detailed information on excitation energies, decay widths, transition probabilities, and branching ratios of 37 new low-lying states in the energy range 1.8-3.5 MeV have been obtained. The observed dipole strength is rather fragmented, apart from a strong excitation at 2.297 MeV. The total strength in the investigated range of excitation energies (1.8-4 MeV) is reduced by a factor of ~3.5 as compared to the neighboring even-even nucleus 180Hf.

  8. 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.

  9. 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.

  10. 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.

  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. Dipole strength distributions in stable odd-mass nuclei in the vicinity of the N=82 isotones

    NASA Astrophysics Data System (ADS)

    Scheck, Marcus

    2006-10-01

    The low-lying dipole strength distributions in the odd-mass nuclei ^135Ba, ^137Ba, ^139La and ^141Pr were studied in nuclear resonance fluorescence (NRF) experiments performed at the Stuttgart Dynamitron facility. experiments used bremsstrahlung beams with endpoint energies of 4.1 MeV. The spin selective NRF reaction allowed the excitation of states through dipole transitions, up to 4 MeV. A special focus is the fragmented E1-strength of transitions connecting the ground state to states of the [2^+ 3^-] particle/hole coupling. The summed strength of the odd-mass nuclei is compared with the E1-strength of the [2^+ 3^-]1^- two-phonon states of the neighboring even-even core nuclei.

  13. 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

  14. 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

  15. 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.

  16. 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.

  17. 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.

  18. Hg Isotopes Reveal Importance of In-Stream Processing and Legacy Inputs in East Fork Poplar Creek, Oak Ridge, Tennessee, USA.

    NASA Astrophysics Data System (ADS)

    Demers, J. D.; Blum, J. D.; Brooks, S. C.; Donovan, P. M.; Gu, B.; Riscassi, A.

    2015-12-01

    Understanding how mercury (Hg) contaminated ecosystems will recover as atmospheric emissions and industrial point source discharges are controlled has become a driving motivation of mercury research. Key to predicting recovery of mercury contaminated ecosystems is an understanding of the mobilization of legacy Hg sources, and the subsequent bioavailability and biogeochemical cycling of mobilized Hg within aquatic ecosystems. Herein, we utilize natural abundance stable Hg isotope techniques to place new constraints on mercury sources, transport, and transformations along the flow path of East Fork Poplar Creek (EFPC), Oak Ridge, Tennessee. The isotopic composition of mercury in stream water and suspended sediment along the flow path suggest that: (1) physical processes such as dilution and sedimentation cannot fully explain decreases in total mercury concentrations along the flow path and that in-stream processes may be more important than previously realized; (2) in-stream processes include photochemical transformations (~20%), but microbial reduction is likely more dominant (~80%); and (3) additional sources of mercury inputs to EFPC at base-flow may predominantly arise from the hyporheic zone during the growing season, with adjacent riparian wetlands and non-point-source impacted tributaries increasing in importance during the dormant season when the stream channel is more hydrologically connected to the watershed.

  19. 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.

  20. 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

  1. 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

  2. Metal transfer to plants grown on a dredged sediment: use of radioactive isotope 203Hg and titanium.

    PubMed

    Caille, Nathalie; Vauleon, Clotilde; Leyval, Corinne; Morel, Jean-Louis

    2005-04-01

    Improperly disposed of dredged sediments contaminated with metals may induce long-term leaching and an increase of metal concentrations in ground waters and vegetal cover plants. The objective of the study was to quantify the sediment-to-plant transfer of Cu, Pb, Hg and Zn with a particular focus on the pathway of Hg and to determine whether the establishment of vegetal cover modifies the metal availability. A pot experiment with rape (Brassica napus), cabbage (Brassica oleraccea) and red fescue (Festuca rubra) was set up using a sediment first spiked with the radioisotope 203Hg. Zinc concentrations (197-543 mg kg(-1) DM) in leaves were higher than Cu concentration (197-543 mg kg(-1) DM), Pb concentration (2.3-2.6 mg kg(-1) DM) and Hg concentration (0.9-1.7 mg kg(-1) DM). Leaves-to-sediment ratios decreased as follows: Zn > Cu > Hg > Pb. According to Ti measurements, metal contamination by dry deposition was less than 1%. Mercury concentration in plant leaves was higher than European and French thresholds. Foliar absorption of volatile Hg was a major pathway for Hg contamination with a root absorption of Hg higher in rape than in cabbage and red fescue. Growth of each species increased Cu solubility. Zinc solubility was increased only in the presence of rape. The highest increase of Cu solubility was observed for red fescue whereas this species largely decreased Zn solubility. Dissolved organic carbon (DOC) measurements suggested that Cu solubilisation could result from organic matter or release of natural plant exudates. Dissolved inorganic carbon (DIC) measures suggested that the high Zn solubility in the presence of rape could originate from a generation of acidity in rape rhizosphere and a subsequent dissolution of calcium carbonates. Consequently, emission of volatile Hg from contaminated dredged sediments and also the potential increase of metal solubility by a vegetal cover of grass when used in phytostabilisation must be taken into account by decision

  3. Low-energy photon scattering experiments of 151,153Eu, 163Dy, and 165Ho and the systematics of the M1 scissors mode in odd-mass rare-earth nuclei

    NASA Astrophysics Data System (ADS)

    Nord, A.; Enders, J.; de Almeida Pinto, A. E.; Belic, D.; von Brentano, P.; Fransen, C.; Kneissl, U.; Kohstall, C.; Linnemann, A.; von Neumann-Cosel, P.; Pietralla, N.; Pitz, H. H.; Richter, A.; Stedile, F.; Werner, V.

    2003-03-01

    Nuclear resonance fluorescence experiments were performed on the rare-earth nuclei 151,153Eu, and with considerably increased sensitivity on 163Dy and 165Ho to study the fragmentation of the M1 scissors mode in odd-mass nuclei, and to clarify the puzzle of the missing total M1 strength observed for odd-mass nuclei so far. Using the bremsstrahlung photon beam of the Stuttgart Dynamitron (end point energy 4.05 MeV) and high-resolution Ge γ-ray spectrometers, detailed information was obtained on excitation energies, decay widths, transition probabilities, and branching ratios. Whereas in 151Eu only 11 weak excitations were observed, 161 and 138 excitations could be detected in the heavier nuclei 163Dy and 165Ho, respectively. The results are compared to those observed recently at the Stuttgart facility for the neighboring odd-mass nuclei 161Dy, 155,157Gd, and 159Tb. The measured total strengths increase with the mass number A. Ascribing the same portion of the dipole strength to M1 excitations as measured in the neighboring even-even nuclei, the total M1 strength deduced from the most sensitive experiment on 163Dy is comparable to those found in the neighboring even-even nuclei. The results for 163Dy and 165Ho are compared with a fluctuation analysis of the photon scattering spectra to estimate the amount of still unresolved strength eventually hidden in the background due to the extreme fragmentation of the M1 scissors mode in odd-mass rare-earth nuclei. For 165Ho, the total derived strength of B(M1)↑=2.9(5)μ2N agrees within error bars with an earlier analysis of a different measurement of the 165Ho(γ,γ') reaction. In 163Dy the method leads to an unphysical background shape, underlining the experimental observation of a significantly reduced fragmentation pattern of the dipole modes in this nucleus, which must be traced back to structure features of the Dy isotopes.

  4. 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.

  5. 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 ...

  6. 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

  7. EVALUATION OF A NON-LETHAL SAMPLING TECHNIQUE FOR THE MEASUREMENT OF MERCURY (HG) CONCENTRATIONS AND STABLE-NITROGEN (15N/14N) ISOTOPE RATIOS IN LARGE MOUTH BASS (MICROPTERUS SALMOIDES)

    EPA Science Inventory

    Contaminant bioaccumulation studies often rely on fish muscle filets as the tissue of choice for the measurement of nitrogen stable isotope ratios ( 15N) and mercury (Hg). Lethal sampling techniques may not be suitable for studies on limited populations from smaller sized aquati...

  8. 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.

  9. 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

  10. 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.

  11. Algebraic solutions for UB F(5 ) -OB F(6 ) quantum phase transition in odd-mass-number nuclei

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

    The spherical to γ -unstable nuclei shape-phase transition in odd-A nuclei is investigated by using the dual algebraic structures and the affine SU (1 ,1 ) ̂ Lie algebra within the framework of the interacting boson-fermion model. The new algebraic solution for odd-A nuclei is introduced. In this model, single j =1 /2 and 3/2 fermions are coupled with an even-even boson core. Energy spectra, quadrupole electromagnetic transitions, and an expectation value of the d -boson number operator are presented. Experimental evidence for the UB F(5 ) -OB F(6 ) transition in odd-A Ba and Rh isotopes is presented. The low-states energy spectra and B (E 2 ) values for these nuclei are also calculated and compared with the experimental data.

  12. Shape Coexistence in Odd-Mass Nuclei Near Z = 82 Closed Shell; a Study of the Excited States of Gold -185 in the BETA(+)/EC Decay of MERCURY-185.

    NASA Astrophysics Data System (ADS)

    Papanicolopoulos, Chrysanthos Dionisios

    1987-11-01

    The excited states of ^{185 }{rm Au} have been studied by the radioactive decay of {^ {185m,g}Hg.} Sources of {^{185m,g}Hg} were produced by the reaction ^{176 }Hf (^{16}O, 7n) ^{185}Hg using 140 MeV ^{16}O beams from the 25 MV folded tandem of the Holifield Heavy Ion Research Facility. Sources of ^{185}Hg were mass-separated on-line using the University Isotope Separator Oak Ridge (UNISOR) facility. Multiscaled spectra of rays, x rays and conversion electrons were obtained together with gamma- gamma - t, gamma- x - t, e ^{-} - gamma - t, and e^{-}- x - t coincidence data. A decay scheme consisting of 82 excited states and 182 transitions was constructed. Bands of states associated with the s_{1over 2}, d_{3over 2} , d_{5over 2}, h_{11over 2} proton -hole configurations and the h_{9over 2} and i_{13over 2} proton-particle (intruder) configurations were constructed. In addition, a number of EO transitions were located: these de-excite levels which are interpreted as resulting from shape coexistence in the ^ {184}Pt and ^{186 }Hg "particle" and "hole" cores. The h _{9over 2} band is compared with calculations made with the Lund model of Larsson et al.

  13. 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.

  14. 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

  15. 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.

  16. 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.

  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. Far-wing excitation study of the reactions in the Hg-H2 collisional quasimolecules. II. Rovibrational distributions of HgH, HgD (X 2Sigma + ) formed from Hg-H2, D2, HD

    NASA Astrophysics Data System (ADS)

    Ohmori, K.; Takahashi, T.; Chiba, H.; Saito, K.; Nakamura, T.; Okunishi, M.; Ueda, K.; Sato, Y.

    1996-11-01

    We have applied the laser-pump/probe and double-beam absorption/dispersion approaches to the far wings of the Hg 3P1-1S0 resonance line broadened by collisions with H2, D2, and HD. Absolute reduced absorption coefficients of the Hg-D2 quasimolecules have been determined as a function of the wave-number shift Δ from the resonance-line center both in the red and blue wings. The nascent rotational distributions have been determined for the v=0 and 1 levels of HgH (X 2Σ+) and the v=0 level of HgD (X 2Σ+) formed from the Hg*(3P1)-H2, D2, and HD collisional-quasimolecular states à and B˜ attained by the red- and blue-wing excitation, respectively. Both of the intermediate states à and B˜ give quite similar rotational distributions peaking around N≂18 for HgH and N≂25 for HgD insensitive to the excitation-wave-number shift Δ. However, a small difference is found: the red-wing excitation gives larger populations in the low-N levels than the blue-wing one. The departing atom isotope effect is observed in these low-N populations of HgD from Hg-D2 and Hg-HD. The absolute ratio of the nascent yields of v=1 to 0 has been measured to be 0.3, being nearly constant against Δ in both the red and blue wings. These observations indicate that HgH is formed predominantly from a bent H-Hg-H configuration on both the pathways via the à and B˜ states. The different type of transition state, however, may be encountered on the pathways producing the minor components in the low-N levels.

  19. 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.

  20. The rotational distribution in the mercury hydride molecules (X 2Sigma + 1/2;vscript=0) produced in the reactions Hg(6 3P1)+H2, HD, or D2

    NASA Astrophysics Data System (ADS)

    Bras, N.; Butaux, J.; Jeannet, J. C.; Perrin, D.

    1986-07-01

    Initial rotational distributions of the vibrationless HgH or HgD molecules produced in the exoergic reactions of Hg (3P1) with H2, D2, and HD have been determined. No isotope effects have been observed. In the case of the reaction with HD the ratio [HgH(v`=0)]/[HgD (v`=0)] as well as the summed over all v` ratio [HgH]/[HgD] have been measured.

  1. 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.

  2. 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.

  3. 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.

  4. Reduction of Hg(II) to Hg(0) by magnetite.

    PubMed

    Wiatrowski, Heather A; Das, Soumya; Kukkadapu, Ravi; Ilton, Eugene S; Barkay, Tamar; Yee, Nathan

    2009-07-15

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

  5. 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).

  6. 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...

  7. Mercury stable isotope signatures of world coal deposits and historical coal combustion emissions.

    PubMed

    Sun, Ruoyu; Sonke, Jeroen E; Heimbürger, Lars-Eric; Belkin, Harvey E; Liu, Guijian; Shome, Debasish; Cukrowska, Ewa; Liousse, Catherine; Pokrovsky, Oleg S; Streets, David G

    2014-07-01

    Mercury (Hg) emissions from coal combustion contribute approximately half of anthropogenic Hg emissions to the atmosphere. With the implementation of the first legally binding UNEP treaty aimed at reducing anthropogenic Hg emissions, the identification and traceability of Hg emissions from different countries/regions are critically important. Here, we present a comprehensive world coal Hg stable isotope database including 108 new coal samples from major coal-producing deposits in South Africa, China, Europe, India, Indonesia, Mongolia, former USSR, and the U.S. A 4.7‰ range in δ(202)Hg (-3.9 to 0.8‰) and a 1‰ range in Δ(199)Hg (-0.6 to 0.4‰) are observed. Fourteen (p < 0.05) to 17 (p < 0.1) of the 28 pairwise comparisons between eight global regions are statistically distinguishable on the basis of δ(202)Hg, Δ(199)Hg or both, highlighting the potential application of Hg isotope signatures to coal Hg emissions tracing. A revised coal combustion Hg isotope fractionation model is presented, and suggests that gaseous elemental coal Hg emissions are enriched in the heavier Hg isotopes relative to oxidized forms of emitted Hg. The model explains to first order the published δ(202)Hg observations on near-field Hg deposition from a power plant and global scale atmospheric gaseous Hg. Yet, model uncertainties appear too large at present to permit straightforward Hg isotope source identification of atmospheric forms of Hg. Finally, global historical (1850-2008) coal Hg isotope emission curves were modeled and indicate modern-day mean δ(202)Hg and Δ(199)Hg values for bulk coal emissions of -1.2 ± 0.5‰ (1SD) and 0.05 ± 0.06‰ (1SD).

  8. 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).

  9. 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.

  10. 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

  11. 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.

  12. 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.

  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.

  14. 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.

  15. Assessing Sources of Human Methylmercury Exposure Using Stable Mercury Isotopes

    PubMed Central

    2015-01-01

    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 δ202Hg values between pilot whale muscle tissue and Faroese whalers’ hair but no mass-independent fractionation. We found a similar offset in δ202Hg 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 Δ199Hg and δ202Hg 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

  16. 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.

  17. Mercury isotopic evidence for multiple mercury sources in coal from the Illinois basin.

    PubMed

    Lefticariu, Liliana; Blum, Joel D; Gleason, James D

    2011-02-15

    Coal combustion is the largest source of anthropogenic mercury (Hg) emissions to the atmosphere and, thus, has vast environmental implications. Recent developments in Hg stable isotope geochemistry offer a new tool for tracing sources and chemical transformations of anthropogenic Hg in the environment. We present here the first isotopic study of mercury in organic and inorganic constituents of four Pennsylvanian-age coal seams in the Illinois Basin, one of the main coal-producing areas in the USA. We report mass dependent isotopic variations relative to the NIST 3133 standard as δ(202)Hg and mass independent fractionation as Δ(199)Hg and Δ(201)Hg values. The data for Illinois coals show a wide range of δ(202)Hg (-0.75 to -2.68‰), Δ(201)Hg (0.04 to -0.22‰), and Δ(199)Hg (0.02 to -0.23‰). In contrast, vein pyrite from two coal seams is isotopically unfractionated relative to NIST 3133. Collectively, these data suggest that isotopically distinct Hg sources contributed to the organic and inorganic fractions of Illinois coals. The Δ(201)Hg/ Δ(199)Hg ratio of Illinois coals is 1:1, consistent with isotopic fractionation by photochemical reduction of Hg(2+) prior to deposition in coal-forming environments. The isotopic composition of Hg in pyrite is more likely derived from hydrothermal fluids that precipitated reduced sulfur in Illinois coal seams. These results demonstrate, for the first time, the potential of Hg isotopes to discriminate between syngenetic (depositional) and epigenetic (hydrothermal) sources of Hg in coal. Our findings may be useful in distinguishing among various geological processes controlling the distribution of Hg in coal and monitoring the fractions of Hg in emissions associated with organic versus inorganic components of coal.

  18. {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.

  19. 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

  20. Historical variations of mercury stable isotope ratios in Arctic glacier firn and ice cores

    NASA Astrophysics Data System (ADS)

    Zdanowicz, C. M.; Krümmel, E. M.; Poulain, A. J.; Yumvihoze, E.; Chen, J.; Å trok, M.; Scheer, M.; Hintelmann, H.

    2016-09-01

    The concentration and isotopic composition of mercury (Hg) were determined in glacier core samples from Canadian Arctic ice caps dating from preindustrial to recent time (early 21st century). Mean Hg levels increased from ≤ 0.2 ng L-1 in preindustrial time to ~0.8-1.2 ng L-1 in the modern industrial era (last ~200 years). Hg accumulated on Arctic ice caps has Δ199Hg and Δ201Hg that are higher (~ -1 to 2.9‰) than previously reported for Arctic snow impacted by atmospheric Hg depletion events (mostly < -1‰), suggesting that these events contribute little to Hg accumulation on ice caps. The range of δ202Hg, Δ199Hg, and Δ201Hg in glacier cores overlaps with that of Arctic Hg0(g) and of seawater in Baffin Bay and also with that of midlatitude precipitation and industrial Hg sources, including coal and Hg ores. A core from Agassiz ice cap (80.7°N) shows a ~ +1‰ shift in δ202Hg over the nineteenth to twentieth centuries that could reflect changes in the isotopic composition of the atmospheric Hg pool in the High Arctic in response to growing industrial emissions at lower latitudes. This study is the first ever to report on historical variations of Hg stable isotope ratios in Arctic ice cores. Results could help constrain future modeling efforts of the global Hg biogeochemical cycle and the atmosphere's response to changing Hg emissions, past and future.

  1. 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.

  2. 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

  3. 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

  4. Radiation trapping of the Hg 185 nm resonance line

    NASA Astrophysics Data System (ADS)

    Menningen, K. L.; Lawler, J. E.

    2000-09-01

    The decay rate of the Hg 61P1 level was measured as a function of cold spot temperature (Hg density) and buffer gas pressure in cylindrical, sealed fused silica cells. The decay rates were obtained using a time-resolved laser-induced 185 nm fluorescence experiment with multi-step excitation. Cold spot temperatures from 25 to 100 °C were studied. The Hg densities for this temperature range and with no buffer gas yield the lowest possible decay rates due to radiation trapping with partial frequency redistribution. Decay rates with argon buffer gas pressures of 3 and 30 Torr were also studied. The results are in agreement with published data from a discharge afterglow experiment. Monte Carlo simulations of radiation transport in the cells, including the effects of hyperfine and isotope structure, the effects of foreign gas broadening, and partial frequency redistribution are compared to the experimental data. Reasonably good agreement is obtained, however there is evidence of quenching of Hg 61P1 atoms in collisions with ground state Hg and Ar atoms. An analytic formula for the fundamental mode trapped decay rate of the 61P1 level, which is applicable over a substantial region of parameter space, was devised from the Monte Carlo results.

  5. Novel methodology for the study of mercury methylation and reduction in sediments and water using 197Hg radiotracer.

    PubMed

    Ribeiro Guevara, Sergio; Zizek, Suzana; Repinc, Urska; Pérez Catán, Soledad; Jaćimović, Radojko; Horvat, Milena

    2007-03-01

    Mercury tracers are powerful tools that can be used to study mercury transformations in environmental systems, particularly mercury methylation, demethylation and reduction in sediments and water. However, mercury transformation studies using tracers can be subject to error, especially when used to assess methylation potential. The organic mercury extracted can be as low as 0.01% of the endogenous labeled mercury, and artefacts and contamination present during methylmercury (MeHg) extraction processes can cause interference. Solvent extraction methods based on the use of either KBr/H2SO4 or HCl were evaluated in freshwater sediments using 197Hg radiotracer. Values obtained for the 197Hg tracer in the organic phase were up to 25-fold higher when HCl was used, which is due to the coextraction of 197Hg2+ into the organic phase during MeHg extraction. Evaluations of the production of MeHg gave similar results with both MeHg extraction procedures, but due to the higher Hg2+ contamination of the controls, the uncertainty in the determination was higher when HCl was used. The Hg2+ contamination of controls in the HCl extraction method showed a nonlinear correlation with the humic acid content of sediment pore water. Therefore, use of the KBr/H2SO4 method is recommended, since it is free from these interferences. 197Hg radiotracer (T1/2=2.673 d) has a production rate that is about 50 times higher than that of 203Hg (T1/2=46.595 d), the most frequently used mercury radiotracer. Hence it is possible to obtain a similar level of performance to 203Hg when it is used it in short-term experiments and produced by the irradiation of 196Hg with thermal neutrons, using mercury targets with the natural isotopic composition. However, if the 0.15% natural abundance of the 196Hg isotope is increased, the specific activity of the 197Hg tracer can be significantly improved. In the present work, 197Hg tracer was produced from mercury 51.58% enriched in the 196Hg isotope, and a 340-fold

  6. 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

  7. Isotopic composition for source identification of mercury in atmospheric fine particles

    NASA Astrophysics Data System (ADS)

    Huang, Qiang; Chen, Jiubin; Huang, Weilin; Fu, Pingqing; Guinot, Benjamin; Feng, Xinbin; Shang, Lihai; Wang, Zhuhong; Wang, Zhongwei; Yuan, Shengliu; Cai, Hongming; Wei, Lianfang; Yu, Ben

    2016-09-01

    The usefulness of mercury (Hg) isotopes for tracing the sources and pathways of Hg (and its vectors) in atmospheric fine particles (PM2.5) is uncertain. Here, we measured Hg isotopic compositions in 30 potential source materials and 23 PM2.5 samples collected in four seasons from the megacity Beijing (China) and combined the seasonal variation in both mass-dependent fractionation (represented by the ratio 202Hg / 198Hg, δ202Hg) and mass-independent fractionation of isotopes with odd and even mass numbers (represented by Δ199Hg and Δ200Hg, respectively) with geochemical parameters and meteorological data to identify the sources of PM2.5-Hg and possible atmospheric particulate Hg transformation. All PM2.5 samples were highly enriched in Hg and other heavy metals and displayed wide ranges of both δ202Hg (-2.18 to 0.51 ‰) and Δ199Hg (-0.53 to 0.57 ‰), as well as small positive Δ200Hg (0.02 to 0.17 ‰). The results indicated that the seasonal variation in Hg isotopic composition (and elemental concentrations) was likely derived from variable contributions from anthropogenic sources, with continuous input due to industrial activities (e.g., smelting, cement production and coal combustion) in all seasons, whereas coal combustion dominated in winter and biomass burning mainly found in autumn. The more positive Δ199Hg of PM2.5-Hg in spring and early summer was likely derived from long-range-transported Hg that had undergone extensive photochemical reduction. The study demonstrated that Hg isotopes may be potentially used for tracing the sources of particulate Hg and its vectors in the atmosphere.

  8. 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

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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

  14. 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.

  15. 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

  16. 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

  17. 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

  18. 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

  19. 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.

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

    USGS Publications Warehouse

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

    2011-01-01

    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 (HgT) 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 δ202Hg 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 δ202Hg 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 δ202Hg 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 δ202Hg source north of SF Bay. Tailings and thermally decomposed ore (calcine) from the New Idria Hg mine in the California Coast Range had average δ202Hg 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 δ202Hg 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.

  1. 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

  2. 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.

  3. 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.

  4. 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.

  5. 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

  6. 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.

  7. 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.

  8. Tracing mercury contamination sources in sediments using mercury isotope compositions.

    PubMed

    Feng, Xinbin; Foucher, Delphine; Hintelmann, Holger; Yan, Haiyu; He, Tianrong; Qiu, Guangle

    2010-05-01

    Mercury (Hg) isotope ratios were determined in two sediment cores collected from two adjacent reservoirs in Guizhou, China, including Hongfeng Reservoir and Baihua Reservoir. Hg isotope compositions were also analyzed in a soil sample collected from the catchment of Hongfeng Reservoir and three cinnabar samples collected from the Wanshan Hg mine. Baihua Reservoir was contaminated with runoff from Guizhou Organic Chemical Plant (GOCP) when metallic Hg was used as a catalyst to produce acetic acid. Hongfeng Reservoir, located upstream of Baihua, receives Hg from runoff and atmospheric deposition. We demonstrated that delta(202)Hg values relative to NIST 3133 of sediment in Baihua Reservoir ranging from -0.60 to -1.10 per thousand were distinctively different from those in Hongfeng Reservoir varying from -1.67 to -2.02 per thousand. While sediments from both Baihua and Hongfeng Reservoirs were characterized by mass dependent variation (MDF), only Hongfeng Reservoir sediments were characterized by mass independent variation (MIF). Moreover, by using a binary mixing model, we demonstrated the major source of Hg in sediment of Hongfeng Reservoir was from runoff due to soil erosion, which was consistent with the conclusion obtained from a previous Hg balance study. This study demonstrates Hg isotope data are valuable tracers for determining Hg contamination sources in sediments.

  9. 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

  10. 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.

  11. 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

  12. 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‰).

  13. 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

  14. 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

  15. Quantum Phase Transitions in Odd-Mass Nuclei

    NASA Astrophysics Data System (ADS)

    Leviatan, A.; Petrellis, D.; Iachello, F.

    2013-03-01

    Quantum shape-phase transitions in odd-even nuclei are investigated in the framework of the interacting boson-fermion model. Classical and quantum analysis show that the presence of the odd fermion strongly influences the location and nature of the phase transition, especially near the critical point. Experimental evidence for the occurrence of spherical to axially-deformed transitions in odd-proton nuclei Pm, Eu and Tb (Z=61, 63, 65) is presented.

  16. 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).

  17. 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.

  18. 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.

  19. Isotopic composition and fractionation of mercury in Great Lakes precipitation and ambient air.

    PubMed

    Gratz, Lynne E; Keeler, Gerald J; Blum, Joel D; Sherman, Laura S

    2010-10-15

    Atmospheric deposition is a primary pathway by which mercury (Hg) enters terrestrial and aquatic ecosystems; however, the chemical and meteorological processes that Hg undergoes from emission to deposition are not well understood. Hg stable isotope geochemistry is a growing field used to better understand Hg biogeochemical cycling. To examine the atmospheric Hg isotopic composition in the Great Lakes, precipitation and ambient vapor-phase Hg samples were collected in Chicago, IL, Holland, MI, and Dexter, MI, between April 2007 and September 2009. Precipitation samples were characterized by negative mass-dependent fractionation (MDF) (δ(202)Hg = -0.79‰ to 0.18‰), while most vapor-phase samples displayed positive MDF (δ(202)Hg = -0.59‰ to 0.43‰). Positive mass-independent fractionation (MIF) (Δ(199)Hg = 0.04‰ to 0.52‰) was observed in precipitation, whereas MIF was slightly negative in vapor-phase samples (Δ(199)Hg = -0.21‰ to 0.06‰). Significant positive MIF of (200)Hg up to 0.25‰ was also measured in precipitation. Such MIF of an even-mass Hg isotope has not been previously reported in natural samples. These results contrast with recent predictions of the isotopic composition of atmospheric Hg and suggest that, in addition to aqueous photoreduction, other atmospheric redox reactions and source-related processes may contribute to isotopic fractionation of atmospheric Hg.

  20. 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.

  1. 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.

  2. 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.

  3. Chemical abundances in Hg-Mn stars

    NASA Technical Reports Server (NTRS)

    Heacox, W. D.

    1979-01-01

    An abundance analysis has been conducted of 21 elements in 21 Hg-Mn, two Si-Cr, and six normal stars using model atmospheres and high-dispersion spectroscopy in the visible and UV. Manganese line strengths imply abundances that correlate well with stellar effective temperature. Within the studied sample of Hg-Mn stars there appears to be no correlation of abundances of any element with projected rotational velocity. Abundances in several Hg-Mn stars show patterns that are probably consistent with diffusion but difficult to reconcile with equilibrium nucleosynthesis. In general, no combination of gross stellar physical parameters is sufficient to characterize the patterns of line strengths observed in Hg-Mb Hg-Mn stars.

  4. Evasion of added isotopic mercury from a northern temperate lake

    USGS Publications Warehouse

    Southworth, G.; Lindberg, S.; Hintelmann, H.; Amyot, M.; Poulain, A.; Bogle, M.; Peterson, M.; Rudd, J.; Harris, R.; Sandilands, K.; Krabbenhoft, D.; Olsen, M.

    2007-01-01

    Isotopically enriched Hg (90% 202Hg) was added to a small lake in Ontario, Canada, at a rate equivalent to approximately threefold the annual direct atmospheric deposition rate that is typical of the northeastern United States. The Hg spike was thoroughly mixed into the epilimnion in nine separate events at two-week intervals throughout the summer growing season for three consecutive years. We measured concentrations of spike and ambient dissolved gaseous Hg (DGM) concentrations in surface water and the rate of volatilization of Hg from the lake on four separate, week-long sampling periods using floating dynamic flux chambers. The relationship between empirically measured rates of spike-Hg evasion were evaluated as functions of DGM concentration, wind velocity, and solar illumination. No individual environmental variable proved to be a strong predictor of the evasion flux. The DGM-normalized flux (expressed as the mass transfer coefficient, k) varied with wind velocity in a manner consistent with existing models of evasion of volatile solutes from natural waters but was higher than model estimates at low wind velocity. The empirical data were used to construct a description of evasion flux as a function of total dissolved Hg, wind, and solar illumination. That model was then applied to data for three summers for the experiment to generate estimates of Hg re-emission from the lake surface to the atmosphere. Based on ratios of spike Hg to ambient Hg in DGM and dissolved total Hg pools, ratios of DGM to total Hg in spike and ambient Hg pools, and flux estimates of spike and ambient Hg, we concluded that the added Hg spike was chemically indistinguishable from the ambient Hg in its behavior. Approximately 45% of Hg added to the lake over the summer was lost via volatilization. ?? 2007 SETAC.

  5. 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

  6. 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.

  7. 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

  8. 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.

  9. 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.

  10. Complexation of Hg with phytochelatins is important for plant Hg tolerance.

    PubMed

    Carrasco-Gil, Sandra; Alvarez-Fernández, Ana; Sobrino-Plata, Juan; Millán, Rocío; Carpena-Ruiz, Ramón O; Leduc, Danika L; Andrews, Joy C; Abadía, Javier; Hernández, Luís E

    2011-05-01

    Three-week-old alfalfa (Medicago sativa), barley (Hordeum vulgare) and maize (Zea mays) were exposed for 7 d to 30 µm of mercury (HgCl(2) ) to characterize the Hg speciation in root, with no symptoms of being poisoned. The largest pool (99%) was associated with the particulate fraction, whereas the soluble fraction (SF) accounted for a minor proportion (<1%). Liquid chromatography coupled with electro-spray/time of flight mass spectrometry showed that Hg was bound to an array of phytochelatins (PCs) in root SF, which was particularly varied in alfalfa (eight ligands and five stoichiometries), a species that also accumulated homophytochelatins. Spatial localization of Hg in alfalfa roots by microprobe synchrotron X-ray fluorescence spectroscopy showed that most of the Hg co-localized with sulphur in the vascular cylinder. Extended X-ray Absorption Fine Structure (EXAFS) fingerprint fitting revealed that Hg was bound in vivo to organic-S compounds, i.e. biomolecules containing cysteine. Albeit a minor proportion of total Hg, Hg-PCs complexes in the SF might be important for tolerance to Hg, as was found with Arabidopsis thaliana mutants cad2-1 (with low glutathione content) and cad1-3 (unable to synthesize PCs) in comparison with wild type plants. Interestingly, high-performance liquid chromatography-electrospray ionization-time of flight analysis showed that none of these mutants accumulated Hg-biothiol complexes.

  11. 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

    ... 46 Shipping 2 2012-10-01 2012-10-01 false Safety valve requirements for steam boilers (modifies HG... requirements for steam boilers (modifies HG-400 and HG-401). (a) The pressure relief valve requirements and the safety valve requirements for steam boilers must be as indicated in HG-400 and HG-401 of section IV...

  12. 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

    ... 46 Shipping 2 2013-10-01 2013-10-01 false Safety valve requirements for steam boilers (modifies HG... requirements for steam boilers (modifies HG-400 and HG-401). (a) The pressure relief valve requirements and the safety valve requirements for steam boilers must be as indicated in HG-400 and HG-401 of section IV...

  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

    ... 46 Shipping 2 2011-10-01 2011-10-01 false Safety valve requirements for steam boilers (modifies HG... requirements for steam boilers (modifies HG-400 and HG-401). (a) The pressure relief valve requirements and the safety valve requirements for steam boilers must be as indicated in HG-400 and HG-401 of section IV...

  14. 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

    ... 46 Shipping 2 2014-10-01 2014-10-01 false Safety valve requirements for steam boilers (modifies HG... requirements for steam boilers (modifies HG-400 and HG-401). (a) The pressure relief valve requirements and the safety valve requirements for steam boilers must be as indicated in HG-400 and HG-401 of section IV...

  15. 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

    ... 46 Shipping 2 2010-10-01 2010-10-01 false Safety valve requirements for steam boilers (modifies HG... requirements for steam boilers (modifies HG-400 and HG-401). (a) The pressure relief valve requirements and the safety valve requirements for steam boilers must be as indicated in HG-400 and HG-401 of section IV...

  16. Redetermination of Hg2I2

    PubMed Central

    Kars, Mohammed; Roisnel, Thierry; Dorcet, Vincent; Rebbah, Allaoua; L. Carlos, Otero-Diáz

    2012-01-01

    The crystal structure of mercurous iodide, Hg2I2, has been determined previously from X-ray powder diffraction data [Havighurst (1926 ▶). J. Am. Chem. Soc. 48, 2113–2125]. The results of the current redetermination based on single-crystal X-ray diffraction data provide more precise geometrical data and also anisotropic displacement parameters for the Hg and I atoms, which are both situated on positions with site-symmetry 4mm. The structure consists of linear dimers I—Hg—Hg—I extending along the c axis with an Hg—Hg distance of 2.5903 (13) Å. The overall coordination sphere of the Hg+ atom is a considerably distorted octa­hedron. The crystal specimen under investigation was twinned by non-merohedry with a refined twin domain fraction of 0.853 (14):0.147 (14). PMID:22346788

  17. 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.

  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. 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.

  20. Mercury stable isotopes in sediments and largemouth bass from Florida lakes, USA.

    PubMed

    Sherman, Laura S; Blum, Joel D

    2013-03-15

    Humans and wildlife can be exposed to mercury (Hg) through the consumption of fish with elevated concentrations of methylmercury (MeHg). Studies have shown that increased atmospheric deposition of Hg often leads to increased MeHg concentrations in aquatic organisms. However, depending on the ecosystem characteristics, reductions in Hg emissions may not always lead to immediate decreases in fish MeHg concentrations. Measurements of natural abundance Hg stable isotope ratios may enable a better understanding of these complex relationships. To gain insight into the sources of Hg to sport fish in central Florida, we measured the Hg isotopic compositions of surface sediments and largemouth bass from freshwater lakes. We found that fish collected from lakes located near the large Crystal River coal-fired power plant did not display evidence of anomalous negative δ(202)Hg values that were observed in nearby precipitation. This suggests that Hg recently deposited from the atmosphere is not preferentially methylated and bioaccumulated in these lakes relative to previously deposited Hg accumulated in the lake sediments. We also observed significant positive Δ(199)Hg values in the fish that were correlated with light penetration depth in the lakes from which they were collected. This indicates that a significant amount of photochemical degradation of MeHg (up to ~40%) occurred prior to uptake of the remaining MeHg into the food webs. These results suggest that depending on physical lake characteristics and biogeochemical factors, decreased atmospheric Hg deposition may not lead to immediate short-term reductions in fish MeHg concentrations. Instead, recovery of some freshwater fish populations to baseline MeHg concentrations may take decades to centuries. PMID:23062970

  1. 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

  2. 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

  3. 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.

  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. Long-term Hg pollution induced Hg tolerance in the terrestrial isopod Porcellio scaber (Isopoda, Crustacea).

    PubMed

    Lapanje, A; Drobne, D; Nolde, N; Valant, J; Muscet, B; Leser, V; Rupnik, M

    2008-06-01

    The aim of our work was to assess the pollution-induced community tolerance (PICT) of isopod gut microbiota and pollution-induced isopod population tolerance (PIPT). Animals collected from a chronically Hg polluted and an unpolluted location were exposed for 14 days to 10microg Hg/g dry food under laboratory conditions. The lysosomal membrane stability, hepatopancreas epithelium thickness, feeding activity and animal bacterial gut microbiota composition were determined. The results confirm the hypothesis that the response to short-term Hg exposure differs for animals from the Hg polluted and the unpolluted field locations. The animals and their gut microbiota from the Hg polluted location were less affected by Hg in a short-term feeding experiment than those from the unpolluted environment. We discuss the pollution-induced population tolerance of isopods and their gut microbiota as a measure of effects of long-term environmental pollution. The ecological consequences of such phenomena are also discussed.

  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. 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

  8. 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.

  9. 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.

  10. 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

  11. 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

  12. 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

  13. Application of an orthogonally polarized laser scheme for selective photoionization of palladium isotopes

    NASA Astrophysics Data System (ADS)

    Locke, Clayton R.; Kobayashi, Tohru; Nakajima, Takashi; Midorikawa, Katsumi

    2016-09-01

    We present a technique using two orthogonal linearly polarized lasers to improve practical implementation of the separation of odd- and even-mass-number palladium isotopes. Dye lasers are used for a three-step photoionization of vaporized palladium, where due to the transition selection rules only odd-mass-number isotopes are ionized and removed from the palladium beam via an electric field. Schemes presented in the literature use two counter-propagating circularly polarized beams, which are in practice difficult to implement perfectly. In contrast, two counter-propagating orthogonally polarized beams are technically less demanding to implement, yet the scheme retains the same high selectivity demonstrated in this work of >1200 (or 99.7 ± 0.3 %).

  14. 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(+).

  15. 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.

  16. 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.

  17. 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...

  18. 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...

  19. 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...

  20. 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...

  1. 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...

  2. 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...

  3. 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.

  4. 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.

  5. 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

  6. 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.

  7. 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.

  8. 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

  9. {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.

  10. 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

  11. 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

  12. 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.

  13. Total-Hg and organic-Hg in Cephalopholis fulva (Linnaeus, 1758) from inshore and offshore waters of NE Brazil.

    PubMed

    Lacerda, L D; Santos, J A; Campos, R C; Gonçalves, R A; Salles, R

    2007-08-01

    To investigate whether source proximity or bioavailability is the major factor controlling both Hg concentration and Hg speciation in marine fishes, total- and organic-Hg content in muscle and liver tissues from different populations of Cephalopholis fulva (piraúna) from inshore and offshore waters of the Brazilian northeastern coast were analyzed. Average total-Hg in muscle (104 ng x g(-1) w.w.) and liver (2,865 ng x g(-1) w.w.) tissues, as well as organic-Hg concentrations in muscle (169 ng x g(-1) w.w.) and liver (1,038 ng x g(-1) w.w.), were much higher in the offshore population of C. fulva than in the inshore ones. In the inshore population total-Hg and organic-Hg average concentrations in muscle tissue were similar and reached only 49 ng x g(-1) w.w., while in liver they reached 412 ng x g(-1) w.w. for total-Hg and 180 ng x g(-1) w.w., for organic-Hg. Concentrations of both Hg species in the two populations were higher in liver than in muscle. The average percentage contribution of organic-Hg to the total Hg content was higher in muscle (98-100%) than in liver (42-53%), but similar between the two populations. Total-Hg and organic-Hg concentrations in muscle and liver from the offshore population showed significant (P < 0.05) positive correlation with fish length. However, in the inshore population only the total-Hg and organic-Hg in muscle tissues correlate significantly with fish size. Although the coastal environments are enriched in total Hg relative to open waters, the significant higher Hg concentrations in the offshore population of C. fulva and the significant correlation found between organic-Hg in liver with fish size suggest higher bioavailability of Hg in offshore waters relative to inshore ones.

  14. 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.

  15. 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.

  16. 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

  17. 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.

  18. 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.

  19. Hg/HgO electrode and hydrogen evolution potentials in aqueous sodium hydroxide

    NASA Astrophysics Data System (ADS)

    Nickell, Ryan A.; Zhu, Wenhua H.; Payne, Robert U.; Cahela, Donald R.; Tatarchuk, Bruce J.

    The Hg/HgO electrode is usually utilized as a reference electrode in alkaline solution such as for development of an alkaline hydrogen electrode. The reference electrode provides a suitable reference point but is available from few commercial vendors and suffers from inadequate documentation on potential in varying electrolytes. A new numerical method uses activity, activity coefficients, and a few correlated empirical equations to determine the potential values in both dilute and concentrated sodium hydroxide solutions at temperatures of 0-90 °C and at concentrations of 0.100-12.8 mol k gH2O-1 . The computed potentials of the Hg/HgO electrodes versus a normal hydrogen electrode (NHE) at 25 °C and 1 atm are 0.1634 V for 0.100m, 0.1077 V for 1.00m, and 0.0976 V for 1.45m NaOH solutions. The Hg/HgO reduction potential further changes to -0.0751 V versus NHE and hydrogen evolution potential changes to -0.9916 V versus NHE in a solution of 30.0 wt.% NaOH at 80 °C. The calculated values are compared with the measured data at 25 and 75 °C. The experimental data agree well with the numerical values computed from the theoretical and empirical equations.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. Mercury in a thin layer in HgMn stars - A test of a diffusion model

    NASA Technical Reports Server (NTRS)

    Megessier, C.; Michaud, G.; Weiler, E. J.

    1980-01-01

    Lines of the first three states of ionization of mercury have been observed in Mu Leporis and Chi Lupi using the Copernicus satellite. Lines of Hg II and Hg III have been observed in Alpha Andromedae. There appears to be an absorption feature at every wavelength where there is expected to be a mercury line. The presence of all three states of ionization is likely in Mu Lep and Chi Lup. The relative equivalent widths of the lines of the various states of ionization do not depend on the effective temperature of the stars, in contradiction to what is expected if mercury were uniformly distributed in the atmosphere. It is, however, expected if mercury has been concentrated, by diffusion, in a thin layer, where the radiative forces just equal the gravitational forces on mercury. That mercury should be so concentrated is also required by the explanation of the mercury isotope anomaly proposed by Michaud, Reeves, and Charland.

  6. 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

  7. Crystal structure of Hg2SO4 - a redetermination.

    PubMed

    Weil, Matthias

    2014-09-01

    The crystal structure of mercury(I) sulfate (or mercurous sulfate), Hg2SO4, was re-determined based on modern CCD data. In comparison with the previous determination from Weissenberg film data [Dorm (1969 ▶). Acta Chem. Scand. 23, 1607-1615], all atoms were refined with anisotropic displacement parameters, leading to higher precision in terms of bond lengths and angles [e.g. Hg-Hg = 2.5031 (7) compared to 2.500 (3)Å]. The structure consists of alternating rows along [001] of Hg2 (2+) dumbbells (generated by inversion symmetry) and SO4 (2-) tetra-hedra (symmetry 2). The dumbbells are linked via short O-Hg-Hg-O bonds to the sulfate tetra-hedra into chains extending parallel to [20-1]. More remote O-Hg-Hg-O bonds connect these chains into a three-dimensional framework.

  8. 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.

  9. 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.

  10. Isotopic Paleoclimatology

    NASA Astrophysics Data System (ADS)

    Bowen, R.

    Paleotemperature scales were calculated by H. C. Urey and others in the 1950s to assess past temperatures, and later work using the stable isotopes of oxygen, hydrogen, and carbon employed standards such as Peedee belemnite (PDB) and Standard Mean Ocean Water (SMOW). Subsequently, subjects as diverse as ice volume and paleotemperatures, oceanic ice and sediment cores, Pleistocene/Holocene climatic changes, and isotope chronostratigraphy extending back to the Precambrian were investigated.

  11. 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.

  12. 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.

  13. 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

  14. 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.

  15. Anomalous mercury isotopic compositions of fish and human hair in the Bolivian Amazon.

    PubMed

    Laffont, Laure; Sonke, Jeroen E; Maurice, Laurence; Hintelmann, Holger; Pouilly, Marc; Sánchez Bacarreza, Yuba; Perez, Tamará; Behra, Philippe

    2009-12-01

    We report mercury (Hg) mass-dependent isotope fractionation (MDF) and mass-independent isotope fractionation (MIF) in hair samples of the Bolivian Esse Ejjas native people and in several tropical fish species that constitute their daily diet. MDF with delta(202)Hg ranging from -0.40 to -0.92 per thousand for fish and +1.04 to +1.42 per thousand for hair was observed. Hair samples of native people with a fish-dominated diet are enriched by +2.0 +/- 0.2 per thousand in delta(202)Hg relative to the fish consumed. Both odd Hg isotopes, (199)Hg and (201)Hg, display MIF in fish (from -0.14 to +0.38 per thousand for Delta(201)Hg and from -0.09 to +0.55 per thousand for Delta(199)Hg) and in hair (from +0.12 to +0.66 per thousand for Delta(201)Hg and from +0.14 to +0.81 per thousand for Delta(199)Hg). No significant difference in MIF anomalies is observed between Hg in fish and in human hair, suggesting that the anomalies act as conservative source tracers between upper trophic levels of the tropical food chain. Fish Hg MIF anomalies are 10-fold lower than those published for fish species from midlatitude lakes. Grouping all Amazonian fish species per location shows that Delta(199)Hg:Delta(201)Hg regression slopes for the clear water Itenez River basin (0.95 +/- 0.08) are significantly lower than those for the white water Beni River basin (1.28 +/- 0.12). Assuming that the observed MIF originates from aquatic photoreactions, we calculated limited photodemethylation of monomethylmercury (MMHg) in the Beni River floodplains and insignificant photodemethylation in the Itenez River floodplains. This is possibly related to lower residence times of MMHg in the Itenez compared to the Beni River floodplains. Finally, a significantly negative Delta(201)Hg of -0.14 per thousand in Beni River fish suggests that the inorganic Hg precursor to the MMHg that bioaccumulates up the food chain defines an ecosystem specific non-zero Delta(201)Hg baseline. Calculation of photodemethylation

  16. 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).

  17. 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).

  18. 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

  19. 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.

  20. 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...

  1. Mass-dependent and mass-independent variations in the isotope composition of mercury in a sediment core from a lake polluted by emissions from the combustion of coal.

    PubMed

    Jackson, Togwell A; Muir, Derek C G

    2012-02-15

    A dated sediment core from a lake polluted with mercury (Hg), other heavy metals, and arsenic (As) from coal-burning power plants was analysed to test the hypothesis that power plant emissions have distinctive Hg isotope signatures which may be preserved in sediments but are altered by natural processes. Coal and fly ash were also analysed. The research yielded evidence for mass-dependent and mass-independent fractionation of Hg isotopes (MDF and MIF, respectively) by combustion and flue gas reactions in the power plants and natural processes in the lake. Power plant pollution and earlier pollution attributable to domestic coal burning produced a characteristic isotope signature indicative of depletion in lighter isotopes by MDF and enrichment in (199)Hg and (201)Hg by MIF, suggesting loss of isotopically light gaseous Hg(0) and reactions of Hg with free radicals at the sources of pollution; but coal and fly ash data showed that combustion imparted a different signature to the ash, corroborating chemical evidence that reactive gaseous Hg(II), not particulate Hg(II), was the principal Hg fraction deposited in the lake. Moreover, the core data imply alteration of the anthropogenic isotope signature by microbially mediated MDF and MIF, with alteration of the microbial activities themselves by toxic effects of As and metals from the emissions. Effects of metals on isotope fractionation increased with the stability constants and ligand field stabilisation energies of metal complexes, suggesting inhibition of microbial enzymes and metal binding by microbial carrier molecules. The importance of fractionation by natural (possibly microbial) processes is also indicated by depletion in (199)Hg and (201)Hg owing to MIF in sediments predating local pollution. In brief, the isotope signature of the polluted sediment is probably the net result of abiotic reactions at the sources of pollution, microbial activities in the lake, and effects of toxic pollutants on the microflora.

  2. Higher mass-independent isotope fractionation of methylmercury in the pelagic food web of Lake Baikal (Russia).

    PubMed

    Perrot, Vincent; Pastukhov, Mikhail V; Epov, Vladimir N; Husted, Søren; Donard, Olivier F X; Amouroux, David

    2012-06-01

    Mercury undergoes several transformations that influence its stable isotope composition during a number of environmental and biological processes. Measurements of Hg isotopic mass-dependent (MDF) and mass-independent fractionation (MIF) in food webs may therefore help to identify major sources and processes leading to significant bioaccumulation of methylmercury (MeHg). In this work, δ(13)C, δ(15)N, concentration of Hg species (MeHg, inorganic Hg), and stable isotopic composition of Hg were determined at different trophic levels of the remote and pristine Lake Baikal ecosystem. Muscle of seals and different fish as well as amphipods, zooplankton, and phytoplankton were specifically investigated. MDF during trophic transfer of MeHg leading to enrichment of heavier isotopes in the predators was clearly established by δ(202)Hg measurements in the pelagic prey-predator system (carnivorous sculpins and top-predator seals). Despite the low concentrations of Hg in the ecosystem, the pelagic food web reveals very high MIF Δ(199)Hg (3.15-6.65‰) in comparison to coastal fish (0.26-1.65‰) and most previous studies in aquatic organisms. Trophic transfer does not influence MIF signature since similar Δ(199)Hg was observed in sculpins (4.59 ± 0.55‰) and seal muscles (4.62 ± 0.60‰). The MIF is suggested to be mainly controlled by specific physical and biogeochemical characteristics of the water column. The higher level of MIF in pelagic fish of Lake Baikal is mainly due to the bioaccumulation of residual MeHg that is efficiently turned over and photodemethylated in deep oligotrophic and stationary (i.e., long residence time) freshwater columns.

  3. 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.

  4. 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.

  5. 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

  6. 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 yet

  7. 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.

  8. 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.

  9. Determination of Cd, Cr, Hg and Pb in plastics from waste electrical and electronic equipment by inductively coupled plasma mass spectrometry with collision-reaction interface technology.

    PubMed

    Santos, Mirian C; Nóbrega, Joaquim A; Cadore, Solange

    2011-06-15

    A procedure based on the use of a quadrupole inductively coupled plasma-mass spectrometer equipped with a collision-reaction interface (CRI) for control of spectral overlap interferences was developed for simultaneous determination of Cd, Cr, Hg, and Pb in plastics from waste electrical and electronic equipment (WEEE). The injection of H(2) and He (80 and 60 mL min(-1), respectively) into the sampled plasma, colliding and reacting with potentially interfering polyatomic ions, allows interference-free determination of chromium via its isotopes (52)Cr and (53)Cr that are freed from overlap due to the occurrence of (40)Ar(12)C(+), (40)Ar(12)C(1)H(+), (36)S(16)O(+) or (1)H(36)S(16)O(+). Cadmium, Hg and Pb were directly determined via their isotopes (110)Cd, (111)Cd, (112)Cd, (199)Hg, (200)Hg, (201)Hg, (202)Hg, (206)Pb, (207)Pb, and (208)Pb, without using CRI. The CRI can be quickly activated or deactivated before each analyte measurement. Limits of detection for (52)Cr were 0.04 or 0.14 μg L(-1) with He or H(2) injected in CRI. Cadmium and Pb have LODs between 0.02 and 0.08 μg L(-1) and Hg had 0.93-0.98 μg L(-1), without using CRI. Analyte concentrations for samples varied from 16 to 43, 1 to 11, 4 to 12, and 5 to 13 mg kg(-1) for Cr, Cd, Hg and Pb, respectively.

  10. 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.

  11. 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.

  12. 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.

  13. 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

  14. 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

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. The role of terrestrial vegetation in mercury deposition: fate of stable mercury isotopes applied to upland and wetland forest canopies during the METAALICUS experiment (Invited)

    NASA Astrophysics Data System (ADS)

    Graydon, J. A.; St. Louis, V. L.; Lindberg, S. E.; Sandilands, K.; Krabbenhoft, D. P.; Tate, M. T.; Harris, R.; Emmerton, C. A.; Richardson, M.; Asmath, H.

    2009-12-01

    Methylmercury (MeHg) is an organic, neurotoxic form of mercury (Hg) that is responsible for fish consumption advisories in North American freshwaters. It is generally believed that increases in anthropogenic Hg emissions have resulted in high MeHg concentrations of fish. However, a direct relationship between deposition of inorganic Hg(II) and concentrations of MeHg in fish has been difficult to demonstrate because of our inability to distinguish newly-deposited Hg from Hg accumulated historically in ecosystems. The Mercury Experiment to Assess Atmospheric Loading In Canada and the US (METAALICUS) increased atmospheric inputs of mercury (Hg) to a small lake and its watershed to levels comparable to those in more industrialized regions. Between 2001 and 2006, three different enriched stable isotopes of Hg (spikes) were loaded to the watershed, one each to the surface of the lake (200Hg), the wetland (198Hg) and the forested upland (202Hg) areas of the catchment to determine the relative contribution of these sources to fish MeHg concentrations. Terrestrial vegetation often represents the first landscape compartment that new atmospheric Hg contacts upon deposition, and plants act as conduits of atmospheric Hg to the landscape. We will present pools and fluxes of spike Hg within upland and wetland canopy and ground vegetation compartments. Our Geographical Information Systems-based modeling approach to calculating spike pools used aircraft spray tracks, regressions between spike application rate and concentrations of spike in vegetation, a LiDAR-derived Leaf Area Index (LAI) map and relationships between LAI and canopy biomass. We observed that 30-50% of spike Hg applied to the upland and wetland was initially intercepted by the forest canopy. Average half lives of spike Hg on deciduous (110±30 days) and coniferous (180±40 days) forest canopy and ground vegetation (890±620 days) indicated that retention of new atmospheric Hg(II) on terrestrial vegetation delays

  20. 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

  1. 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

  2. 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.

  3. 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

  4. 40 CFR 60.4142 - Hg allowance allocations.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... produced by any associated heat recovery steam generator during the control period divided by 0.8, and with... Coal-Fired Electric Steam Generating Units Hg Allowance Allocations § 60.4142 Hg allowance allocations... gross electrical output of the generator or generators served by the unit multiplied by 7,900...

  5. 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.

  6. Temporal and spatial variation in Hg accumulation in zebra mussels (Dreissena polymorpha): possible influences of DOC and diet.

    PubMed

    Kraemer, Lisa D; Evans, Douglas; Dillon, Peter J

    2013-05-01

    Zebra mussels (Dreissena polymorpha) are filter feeders located near the base of the foodweb and these animals are able to utilize a variety of carbon sources that may also vary seasonally. We conducted both a spatial and a temporal study in order to test the hypotheses: (1) dissolved organic carbon (DOC) concentrations influence Hg accumulation in zebra mussels sampled from a series of lakes and (2) seasonal variations in diet influence Hg accumulation. In the spatial study, we found a significant negative relationship between Hg concentrations and DOC concentrations, suggesting an influence of DOC on Hg bioaccumulation. In the temporal study, we used stable isotope ratios of nitrogen (δ(15)N) and carbon (δ(13)C) as ecological tools to provide a temporally integrated description of the feeding ecology of zebra mussels. Both δ(15)N and δ(13)C varied seasonally in a similar manner: more depleted values occurred in the summer and more enriched values occurred in the fall. Mercury concentrations also varied significantly over the year, with highest concentrations occurring in the summer, followed by a progressive decrease in concentrations into the fall. The C/N ratio of zebra mussels also varied significantly over the year with the lowest values occurring mid-summer and then values increased in the fall and winter, suggesting that there was significant variation in lipid stores. These results indicate that in addition to any effect of seasonal dietary changes, seasonal variation in energy stores also appeared to be related to Hg levels in the zebra mussels. Collectively results from this study suggest that DOC concentrations, seasonal variation in diet and seasonal depletion of energy stores are all important variables to consider when understanding Hg accumulation in zebra mussels. PMID:23433835

  7. The reaction of Hg(6 3P1) with hydrogen molecules studied by electron spin resonance and laser induced fluorescence

    NASA Astrophysics Data System (ADS)

    Yi, Whikun; Satyapal, Sunita; Shafer, Neil; Bersohn, Richard

    1993-09-01

    Mercury atoms were excited to the 6 3P1 state with a pulsed laser and a lamp at 253.7 nm in the presence of H2, D2, HD, and mixtures of these gases. The hydrogen atom reaction products were detected by vacuum ultraviolet (VUV) laser induced fluorescence. The ratio of yields of the two body channel (mercury hydride and a hydrogen atom) and the three body channel [Hg(6 1S0) and two hydrogen atoms] were determined by combining the H/D atom ratios and a literature value of the HgD/HgH ratio from reaction with HD. Assuming that the sum of the two yields is unity, the yield of the two body channel is for H2 0.63±0.15, for D2 0.79±0.11, and for HD 0.10±0.02 (HgH+D) and 0.65±0.03 (HgD+H). The average kinetic energies calculated by combining these yields with the literature data on internal energy release in the mercury hydride molecules agree with the average kinetic energies measured from the Doppler broadened fluorescence excitation curves. When the E vector of the exciting polarized light was rotated there was no effect on the hydrogen atom spectrum proving that the hydrogen atom velocity distribution is isotropic. When the mercury atoms were excited with circularly polarized light to the J=1, MJ=1 state, the hydrogen atoms exhibited no spin polarization. Electron spin resonance (ESR) signals observed when irradiating a mixture of Hg and hydrogen molecules were shown by isotopic effects to be due to hydrogen atoms dissociated from mercury hydride molecules.

  8. Temporal and spatial variation in Hg accumulation in zebra mussels (Dreissena polymorpha): possible influences of DOC and diet.

    PubMed

    Kraemer, Lisa D; Evans, Douglas; Dillon, Peter J

    2013-05-01

    Zebra mussels (Dreissena polymorpha) are filter feeders located near the base of the foodweb and these animals are able to utilize a variety of carbon sources that may also vary seasonally. We conducted both a spatial and a temporal study in order to test the hypotheses: (1) dissolved organic carbon (DOC) concentrations influence Hg accumulation in zebra mussels sampled from a series of lakes and (2) seasonal variations in diet influence Hg accumulation. In the spatial study, we found a significant negative relationship between Hg concentrations and DOC concentrations, suggesting an influence of DOC on Hg bioaccumulation. In the temporal study, we used stable isotope ratios of nitrogen (δ(15)N) and carbon (δ(13)C) as ecological tools to provide a temporally integrated description of the feeding ecology of zebra mussels. Both δ(15)N and δ(13)C varied seasonally in a similar manner: more depleted values occurred in the summer and more enriched values occurred in the fall. Mercury concentrations also varied significantly over the year, with highest concentrations occurring in the summer, followed by a progressive decrease in concentrations into the fall. The C/N ratio of zebra mussels also varied significantly over the year with the lowest values occurring mid-summer and then values increased in the fall and winter, suggesting that there was significant variation in lipid stores. These results indicate that in addition to any effect of seasonal dietary changes, seasonal variation in energy stores also appeared to be related to Hg levels in the zebra mussels. Collectively results from this study suggest that DOC concentrations, seasonal variation in diet and seasonal depletion of energy stores are all important variables to consider when understanding Hg accumulation in zebra mussels.

  9. 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.

    PubMed

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

    2014-02-01

    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

  10. 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

  11. 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

  12. 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

  13. 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.

  14. 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

    2016-05-06

    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.

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

    SciTech Connect

    Heymann, D.; Liffman, K.

    1986-03-01

    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). 24 references

  16. 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).

  17. Binding of HgII to high-affinity sites on bacteria inhibits reduction to Hg0 by mixed FeII/III phases.

    PubMed

    Mishra, Bhoopesh; O'Loughlin, Edward J; Boyanov, Maxim I; Kemner, Kenneth M

    2011-11-15

    Magnetite and green rust have been shown to reduce aqueous Hg(II) to Hg(0). In this study, we tested the ability of magnetite and green rust to reduce Hg(II) sorbed to 2 g · L(-1) of biomass (Bacillus subtilis), at high (50 μM) and low (5 μM) Hg loadings and at pH 6.5 and 5.0. At high Hg:biomass loading, where Hg(II) binding to biomass is predominantly through carboxyl functional groups, Hg L(III)-edge X-ray absorption spectroscopy showed reduction of Hg(II) to Hg(0) by magnetite. Reduction occurred within 2 h and 2 d at pH 6.5 and 5.0, respectively. At low Hg:biomass loading, where Hg(II) binds to biomass via sulfhydryl functional groups, Hg(II) was not reduced by magnetite at pH 6.5 or 5.0 after 2 months of reaction. Green rust, which is generally a stronger reductant than magnetite, reduced about 20% of the total Hg(II) bound to biomass via sulfhydryl groups to Hg(0) in 2 d. These results suggest that Hg(II) binding to carboxyl groups does not significantly inhibit the reduction of Hg(II) by magnetite. However, the binding of Hg(II) to biomass via sulfhydryl groups severely inhibits the ability of mixed Fe(II/III) phases like magnetite and green rust to reduce Hg(II) to Hg(0). The mobility of heavy metal contaminants in aquatic and terrestrial environments is greatly influenced by their speciation, especially their oxidation state. In the case of Hg, reduction of Hg(II) to Hg(0) can increase Hg mobility because of the volatility of Hg(0). Since Hg is typically present in aquatic and terrestrial systems at low concentrations, binding of Hg(II) to high-affinity sites on bacteria could have important implications for the potential reduction of Hg(II) to Hg(0) and the overall mobility of Hg in biostimulated subsurface environments. PMID:21913727

  18. Binding of HgII to high-affinity sites on bacteria inhibits reduction to Hg0 by mixed FeII/III phases.

    PubMed

    Mishra, Bhoopesh; O'Loughlin, Edward J; Boyanov, Maxim I; Kemner, Kenneth M

    2011-11-15

    Magnetite and green rust have been shown to reduce aqueous Hg(II) to Hg(0). In this study, we tested the ability of magnetite and green rust to reduce Hg(II) sorbed to 2 g · L(-1) of biomass (Bacillus subtilis), at high (50 μM) and low (5 μM) Hg loadings and at pH 6.5 and 5.0. At high Hg:biomass loading, where Hg(II) binding to biomass is predominantly through carboxyl functional groups, Hg L(III)-edge X-ray absorption spectroscopy showed reduction of Hg(II) to Hg(0) by magnetite. Reduction occurred within 2 h and 2 d at pH 6.5 and 5.0, respectively. At low Hg:biomass loading, where Hg(II) binds to biomass via sulfhydryl functional groups, Hg(II) was not reduced by magnetite at pH 6.5 or 5.0 after 2 months of reaction. Green rust, which is generally a stronger reductant than magnetite, reduced about 20% of the total Hg(II) bound to biomass via sulfhydryl groups to Hg(0) in 2 d. These results suggest that Hg(II) binding to carboxyl groups does not significantly inhibit the reduction of Hg(II) by magnetite. However, the binding of Hg(II) to biomass via sulfhydryl groups severely inhibits the ability of mixed Fe(II/III) phases like magnetite and green rust to reduce Hg(II) to Hg(0). The mobility of heavy metal contaminants in aquatic and terrestrial environments is greatly influenced by their speciation, especially their oxidation state. In the case of Hg, reduction of Hg(II) to Hg(0) can increase Hg mobility because of the volatility of Hg(0). Since Hg is typically present in aquatic and terrestrial systems at low concentrations, binding of Hg(II) to high-affinity sites on bacteria could have important implications for the potential reduction of Hg(II) to Hg(0) and the overall mobility of Hg in biostimulated subsurface environments.

  19. 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.

  20. 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.

  1. 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

  2. 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.

  3. Competition among thiols and inorganic sulfides and polysulfides for Hg and MeHg in wetland soils and sediments under suboxic conditions: Illumination of controversies and implications for MeHg net production

    NASA Astrophysics Data System (ADS)

    Skyllberg, Ulf

    2008-12-01

    Current research focus in mercury biogeochemistry is on the net production and accumulation of methyl mercury (MeHg) in organisms. The activity of iron- and sulfate-reducing bacteria (FeRB and SRB) has been identified as important for MeHg production. There are indications of a passive uptake of neutral Hg-sulfides by SRB, as well as of a facilitated bacterial uptake of Hg complexed by small organic molecules. In order to understand these processes, the chemical speciation of Hg and MeHg, and most important, the competition among organic thiols and inorganic sulfides and polysulfides, needs to be clarified under suboxic conditions (nM to low μM range of total sulfide concentrations) in wetland soils and sediments. In this paper the chemical speciation of Hg and MeHg is modeled at pH 4.0 and 7.0 in a conceptual wetland soil/sediment with typical concentrations of thiols, sulfides, Hg, and MeHg. Effects of precipitated HgS(s), the formation of Hg-polysulfides, and the size of the controversial stability constant for the formation of HOHgSH0 (aq) are emphasized. The outcome of the modeling is discussed in light of chosen stability constants for Hg complexes with thiols, sulfides, and polysulfides. It is concluded that organic thiols are competitive with inorganic sulfides in the approximate total sulfide concentration range 0-1 μm. It is also concluded that increases in absolute aqueous concentrations of MeHg, or the molar ratio of dissolved MeHg/Hg, are not appropriate as indirect measures of MeHg net production, unless changes and differences in solubility of MeHg and Hg are corrected for.

  4. Tracing Fluxes Of Aquatic Production And Contaminants Into Terrestrial Food Webs With Nitrogen Stable Isotopes

    NASA Astrophysics Data System (ADS)

    Rivard, A.; Cabana, G.; Rainey, W.; Power, M.

    2005-05-01

    Biomagnifying contaminants such as mercury can be transported and redistributed across the watershed by streams and rivers. Their fate and effects on consumers depend on food web transfer both within and between aquatic and terrestrial ecosystems. The Truckee River (Ca/Ne) is heavily contaminated by Hg originating from century-old upstream mining operations. We used nitrogen stable isotope analysis to trace the incorporation of Hg transported by the Truckee and transferred by emerging aquatic insects into the riparian food web. N-isotope ratios and Hg of aquatic primary consumers were significantly elevated compared to that of terrestrial arthropods (13.3 vs 5.6 % and 110 vs 17 ngg-1). Estimates of dependence on aquatics in 16 riparian passerine bird species based on blood delta 15N ranged between 0.0 and 0.95 and were significantly related to Hg in blood. Similar correlations between Hg and delta 15N measured in tail tips of western fence lizard (Sceloporus occidentalis) collected at increasing distances from the river were observed. High inter-individual variation in bird Hg was highly correlated with delta 15N. These results show how stable isotopes and contaminant fluxes can reveal important food web linkages across aquatic/terrestrial ecotones.

  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. 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.

  7. 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.

  8. 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

  9. 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

  10. Trace elements (Cu, Zn, and Hg) and δ13C/δ15N 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.

  11. 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.

  12. 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.

  13. 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.

  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. Self-powered sensor for trace Hg2+ detection.

    PubMed

    Wen, Dan; Deng, Liu; Guo, Shaojun; Dong, Shaojun

    2011-05-15

    A self-powered electrochemical sensor has been facilely designed for sensitive detection of Hg(2+) based on the inhibition of biocatalysis process of enzymatic biofuel cell (BFC) for the first time. The as-prepared one-compartment BFC, which was consisted of alcohol dehydrogenase supported on single-walled carbon nanohorns-based mediator system as the anode and bilirubin oxidase as the cathodic biocatalyst, generated an open circuit potential (V(oc)) of 636 mV and a maximum power density of 137 μW cm(-2). It was interestingly found that the presence of Hg(2+) would affect the performance of the constructed BFC (e.g., V(oc)). Taking advantage of the inhibitive effect of Hg(2+), a novel self-powered Hg(2+) sensor has been developed, which showed a linear range of 1-500 nM (R(2) = 0.999) with a detection limit of 1 nM at room temperature. In addition, this BFC-type sensor exhibited good selectivity for Hg(2+) against other common environmental metal ions, and the feasibility of the method for Hg(2+) detection in actual water samples (i.e., tap, ground, and lake water) was demonstrated with satisfactory results.

  16. Crystal structure of K[Hg(SCN)3] - a redetermination.

    PubMed

    Weil, Matthias; Häusler, Thomas

    2014-09-01

    The crystal structure of the room-temperature modification of K[Hg(SCN)3], potassium tri-thio-cyanato-mercurate(II), was redetermined based on modern CCD data. In comparison with the previous report [Zhdanov & Sanadze (1952 ▶). Zh. Fiz. Khim. 26, 469-478], reliability factors, standard deviations of lattice parameters and atomic coordinates, as well as anisotropic displacement parameters, were revealed for all atoms. The higher precision and accuracy of the model is, for example, reflected by the Hg-S bond lengths of 2.3954 (11), 2.4481 (8) and 2.7653 (6) Å in comparison with values of 2.24, 2.43 and 2.77 Å. All atoms in the crystal structure are located on mirror planes. The Hg(2+) cation is surrounded by four S atoms in a seesaw shape [S-Hg-S angles range from 94.65 (2) to 154.06 (3)°]. The HgS4 polyhedra share a common S atom, building up chains extending parallel to [010]. All S atoms of the resulting (1) ∞[HgS2/1S2/2] chains are also part of SCN(-) anions that link these chains with the K(+) cations into a three-dimensional network. The K-N bond lengths of the distorted KN7 polyhedra lie between 2.926 (2) and 3.051 (3) Å.

  17. A 3500-year record of Hg and Pb contamination in a mediterranean sedimentary archive (the Pierre Blanche Lagoon, France).

    PubMed

    Elbaz-Poulichet, F; Dezileau, L; Freydier, R; Cossa, D; Sabatier, P

    2011-10-15

    A sediment core encompassing 3500 years of continuous sedimentation has been collected from a coastal lagoon located on the southwestern French Mediterranean coast. Lead concentrations and stable isotopes show that the sediments have recorded the three major periods of Pb pollution: the Etruscan-Greek-Roman period (650 BC to AD 50), the medieval period (AD 650 to AD 1450), and the modern period (from around AD 1850 to the present). These periods were separated by low pollution periods during the Dark Ages (between AD 50 and 650) and during the 16th century. From the end of the 19th century to the 1960s, Pb pollution increased exponentially. Coal combustion was the major source of Pb in the lagoon in the second half of the 20th century. Both the decrease in coal consumption and the ban on leaded gasoline resulted in a decrease in Pb pollution by a factor of 1.5 between 1973 and 1995. From 1991, sewage treatment plants and incinerators could be the major source of Pb. The average baseline Hg concentration from 1525 BC to AD 900 was 0.017 ± 0.003 μg g⁻¹ (n = 54). The Hg concentrations profile shows three major peaks: in AD 1150, AD 1660, and AD 1969, with the concentrations being respectively 8, 5, and 34 times higher than the baseline levels. The medieval peak (AD 1150) is attributed the medical use of Hg in the town of Montpellier and/or the burning of soil and vegetation. Noticeable Hg pollution was also detected during the 17th century in relation to gold and silver amalgamation in Europe. From the end of the 19th century, Hg concentrations increased exponentially until 1969. This modern pollution is attributed to the burning of coal. PMID:21879750

  18. 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.

  19. Methyl mercury and stable isotopes of nitrogen reveal that a terrestrial spider has a diet of emergent aquatic insects.

    PubMed

    Speir, Shannon L; Chumchal, Matthew M; Drenner, Ray W; Cocke, W Gary; Lewis, Megan E; Whitt, Holly J

    2014-11-01

    Terrestrial spiders transfer methyl mercury (MeHg) to terrestrial consumers such as birds, but how spiders become contaminated with MeHg is not well understood. In the present study, the authors used stable isotopes of nitrogen in combination with MeHg to determine the source of MeHg to terrestrial long-jawed orb weaver spiders (Tetragnatha sp). The authors collected spiders and a variety of other aquatic and terrestrial taxa from 10 shallow ponds in north Texas, USA. Based on MeHg concentrations and stable nitrogen isotope ratios, the authors identified distinct aquatic- and terrestrial-based food chains. Long-jawed orb weaver spiders belonged to the aquatic-based food chain, indicating that they are exposed to MeHg through their consumption of emergent aquatic insects. Additionally, the present study suggests that ecologists can use stable isotopes of nitrogen (δ(15) N) in conjunction with MeHg speciation analysis to distinguish between aquatic and terrestrial food chains.

  20. 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.

  1. 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.

  2. 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

    2015-09-14

    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.

  3. Two-dimensional topological insulators with tunable band gaps: Single-layer HgTe and HgSe

    DOE PAGES

    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

  4. 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.

  5. 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

  6. 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

  7. 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.

  8. Variation in terrestrial and aquatic sources of methylmercury in stream predators as revealed by stable mercury isotopes.

    PubMed

    Tsui, Martin Tsz-Ki; Blum, Joel D; Finlay, Jacques C; Balogh, Steven J; Nollet, Yabing H; Palen, Wendy J; Power, Mary E

    2014-09-01

    Mercury (Hg) is widely distributed in the environment, and its organic form, methylmercury (MeHg), can extensively bioaccumulate and biomagnify in aquatic and terrestrial food webs. Concentrations of MeHg in organisms are highly variable, and the sources in natural food webs are often not well understood. This study examined stable isotope ratios of MeHg (mass-dependent fractionation, as δ(202)HgMeHg; and mass-independent fractionation, as Δ(199)HgMeHg) in benthic invertebrates, juvenile steelhead trout (Oncorhynchus mykiss), and water striders (Gerris remigis) along a stream productivity gradient, as well as carnivorous terrestrial invertebrates, in a forested watershed at the headwater of South Fork Eel River in northern California. Throughout the sampling sites, δ(202)HgMeHg (after correction due to the effect of MeHg photodegradation) was significantly different between benthic (median = -1.40‰; range, -2.34 to -0.78‰; total number of samples = 29) and terrestrial invertebrates (median = +0.51‰; range, -0.37 to +1.40‰; total number of samples = 9), but no major difference between these two groups was found for Δ(199)HgMeHg. Steelhead trout (52 individual fishes) have MeHg of predominantly aquatic origins, with a few exceptions at the upstream locations (e.g., 1 fish collected in a tributary had a purely terrestrial MeHg source and 4 fishes had mixed aquatic and terrestrial MeHg sources). Water striders (seven pooled samples) derive MeHg largely from terrestrial sources throughout headwater sections. These data suggest that direct terrestrial subsidy (e.g., terrestrial invertebrates falling into water) can be important for some stream predators in headwater streams and could represent an important means of transfer of terrestrially derived MeHg (e.g., in situ methylation within forests, atmospheric sources) to aquatic ecosystems. Moreover, these findings show that terrestrial subsidies can enhance MeHg bioaccumulation of consumers in headwater

  9. 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

  10. 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)

  11. 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.

  12. Low-lying dipole excitations in vibrational nuclei: The Cd isotopic chain studied in photon scattering experiments

    NASA Astrophysics Data System (ADS)

    Kohstall, C.; Belic, D.; von Brentano, P.; Fransen, C.; Gade, A.; Herzberg, R.-D.; Jolie, J.; Kneissl, U.; Linnemann, A.; Nord, A.; Pietralla, N.; Pitz, H. H.; Scheck, M.; Stedile, F.; Werner, V.; Yates, S. W.

    2005-09-01

    High-resolution nuclear resonance fluorescence experiments (NRF) were performed on 110,111,112,114,116Cd 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 110,112,114,116Cd, parities could be assigned from linear polarization measurements. Together with our previous results for 108,112,113,114Cd 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.

  13. Straight line regression through data with correlated uncertainties in two or more dimensions, with an application to kinetic isotope fractionation

    NASA Astrophysics Data System (ADS)

    McLean, Noah M.

    2014-01-01

    Straight line regression algorithms are used frequently for measured data that contain non-negligible uncertainties in each variable. For the general case of correlated measurement uncertainties between two variables that differ from one analysis to the next, the popular algorithm of York, 1968 calculates the maximum likelihood estimate for the line parameters and their uncertainties. However, it considers only two-dimensional data and omits the uncertainty correlation between the slope and y-intercept, an important term for evaluating confidence intervals away from the origin. This contribution applies the maximum likelihood method to straight line regression through data in any number of dimensions to calculate a vector-valued slope and intercept as well as the covariance matrix that describes their uncertainties and uncertainty correlations. The algorithm is applied to Pb data measured by TIMS with a silica gel activator that define a fractionation line in a three dimensional log-ratio space. While the log-ratios of even mass number Pb isotopes follow the slope predicted by mass-dependent fractionation with a Rayleigh or exponential law within calculated uncertainties, the log-ratio containing the odd mass number isotope 207Pb diverges significantly, exhibiting mass-independent fractionation. The straight line regression algorithm is appropriate for fractionation lines that form linear trends in log-ratio space, but not for isochrons or mixing lines, which are predicted to be linear only when plotted as isotope or compositional ratios.

  14. 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.

  15. Hg species in the water column of Tyrrhenian Sea (Italy)

    NASA Astrophysics Data System (ADS)

    Kotnik, J.; Bratkic, A.; Vahcic, M.; Horvat, M.; Fajon, V.; Obu, K.

    2014-12-01

    Mercury (Hg) speciation in the water column was successfully performed on samples from the Tyrrhenian Sea during the cruise Fenice2011. Primary objective was to increase sampling's spatial resolution; thereby providing better insight into Hg biogeochemical cycling in environment with naturally higher Hg background. THg values ranged from 0.8 pM to 5.9 pM with an average of 2.5 ± 1.3 pM. Generally, the water column did not exhibit particular variation in THg values. The highest concentrations were measured in the coastal areas near Piombino industrial site and near geothermally active Ustica Island.DGM concentrations were on average 0.39 ± 0.23 pM and ranged from approximately 0.06 pM to 0.83 pM. DGM represented between 2 % and 96 % of THg, with higher proportions measured in deep sea water. This region is a source of Hg0 to the atmosphere, indicated by near depletion of DGM at surface. Waters became increasingly enriched in DGM below 250 m depth, with values ranging from 0.54 pM to 0.83 pM. The observed increase in deep waters was partly due to geothermal activity in the area. MeHg values ranged between 0.01 pM and 0.36 pM with an average of 0.097 ± 0.088 pM. The open sea stations had a slightly higher average value of 0.14 ± 0.10 pM. The surface was generally depleted in MeHg, which was enriched at depths showing oxygen consumption. That suggests spatial coupling with microbial carbon mineralization. Results with increased spatial resolution of sampling clearly show that besides transformations in the mixed layer, more attention should also be given to deeper water masses, particularly because of geothermal activity of the area. In light of global and regional changes of ocean and climate characteristics, minor variations in environmental conditions may change the ratios of Hg species. Toxic MeHg will accumulate and pose threat to human and wildlife populations, whereas DGM formation will only add Hg to the most effective global distribution system, the

  16. 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

  17. 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

  18. Density distribution in the liquid Hg-sapphire interface.

    PubMed

    Zhao, Meishan; Rice, Stuart A

    2011-04-28

    We present the results of a computer simulation study of the liquid density distribution normal to the interface between liquid Hg and the reconstructed (0001) face of sapphire. The simulations are based on an extension of the self-consistent quantum Monte Carlo scheme previously used to study the structure of the liquid metal-vapor interface. The calculated density distribution is in very good agreement with that inferred from the recent experimental data of Tamam et al. (J. Phys. Chem. Lett. 2010, 1, 1041-1045). We conclude that, to account for the difference in structure between the liquid Hg-vapor and liquid-Hg-reconstructed (0001) Al(2)O(3) interfaces, it is not necessary to assume there is charge transfer from the Hg to the Al(2)O(3). Rather, the available experimental data are adequately reproduced when the van der Waals interactions of the Al and O atoms with Hg atoms and the exclusion of electron density from Al(2)O(3) via repulsion of the electrons from the closed shells of the ions in the solid are accounted for.

  19. Electrodeposition and characterization of HgSe thin films

    SciTech Connect

    Mahalingam, T. . E-mail: maha51@rediffmail.com; Kathalingam, A.; Sanjeeviraja, C.; Chandramohan, R.; Chu, J.P.; Kim, Yong Deak; Velumani, S.

    2007-08-15

    In this article we present the results on the electrochemical synthesis of mercury selenide (HgSe), an interesting II-VI material. HgSe thin films were deposited potentiostatically on conducting glass substrates from an aqueous bath containing HgCl{sub 2} and SeO{sub 2}. The prepared films were characterized by X-ray diffraction (XRD), energy dispersive X-ray analysis (EDX), scanning electron microscope (SEM) and optical absorption techniques. Stoichiometric polycrystalline HgSe films were obtained at a deposition potential around - 0.7 V vs SCE, at a temperature 60 deg. C and a pH value of 3.5. The as-grown films exhibited a direct optical band gap of 0.78 eV. This report deals with the growth mechanism and a study related to the influence of electrolyte bath composition, deposition potential, temperature and pH on the properties of HgSe thin films.

  20. 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.

  1. 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

  2. Bioaccumulation of Hg in the mushroom Pleurotus ostreatus.

    PubMed

    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(NO3)2.H2O 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. PMID:3234295

  3. Isotope cisternography in patients with intracranial hypertension

    SciTech Connect

    Hayashi, M.; Kobayashi, H.; Kawano, H.; Handa, Y.; Kabuto, M.; Noguchi, Y.; Shirasaki, H.

    1986-04-01

    Cerebrospinal fluid flow (CSF) was studied using isotope cisternography in 52 patients with increased intracranial pressure (ICP), all of whom showed acute transient rises of ICP, i.e., plateau waves, in their continuous ICP recordings. The patients were assigned to two groups. Group I was comprised of 23 patients without hydrocephalus and high ICP resulting from brain tumors, benign intracranial hypertension, and superior sagittal sinus thrombosis. Group II included 29 patients with either communicating hydrocephalus or high ICP resulting from rupture of intracranial aneurysm. Plateau waves were frequently observed in patients with baseline pressures ranging from 21 to 40 mmHg in both groups. The isotope cisternographic pattern in the Group I patients showed a large accumulation of radioactivity over the cerebral convexities, while that in the Group II patients revealed a complete obstruction of the subarachnoid space over both cerebral convexities. The isotope clearance from the intracranial CSF showed a marked delay in both groups of patients with one exception. The results suggest that, in the limited range of increased ICP caused by delayed CSF absorption, plateau waves are most evident regardless of the isotope cisternographic pattern.

  4. Crystal structure of Hg2SO4 – a redetermination

    PubMed Central

    Weil, Matthias

    2014-01-01

    The crystal structure of mercury(I) sulfate (or mercurous sulfate), Hg2SO4, was re-determined based on modern CCD data. In comparison with the previous determination from Weissenberg film data [Dorm (1969 ▶). Acta Chem. Scand. 23, 1607–1615], all atoms were refined with anisotropic displacement parameters, leading to higher precision in terms of bond lengths and angles [e.g. Hg—Hg = 2.5031 (7) compared to 2.500 (3)Å]. The structure consists of alternating rows along [001] of Hg2 2+ dumbbells (generated by inversion symmetry) and SO4 2− tetra­hedra (symmetry 2). The dumbbells are linked via short O—Hg—Hg—O bonds to the sulfate tetra­hedra into chains extending parallel to [20-1]. More remote O—Hg—Hg—O bonds connect these chains into a three-dimensional framework. PMID:25309168

  5. 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.

  6. Hydrothermal single-crystal growth in the systems Ag/Hg/X/O (X = VV, AsV): crystal structures of (Ag3Hg)VO4, (Ag2Hg2)3(VO4)4, and (Ag2Hg2)2(HgO2)(AsO4)2 with the unusual tetrahedral cluster cations (Ag3Hg)3+ and (Ag2Hg2)4+ and crystal structure of AgHgVO4.

    PubMed

    Weil, Matthias; Tillmanns, Ekkehart; Pushcharovsky, Dmitry Yu

    2005-03-01

    Single crystals of (Ag3Hg)VO4 (I), (Ag2Hg2)3(VO4)4 (II), AgHgVO4 (III), and (Ag2Hg2)2(HgO2)(AsO4)2 (IV) were grown under hydrothermal conditions (250 degrees C, 5 d) from starting mixtures of elementary mercury, silver nitrate, ammonium vanadate, and disodium hydrogenarsenate, respectively. All crystal structures were determined from X-ray diffraction data, and their chemical compositions were confirmed by electron microprobe analysis. I crystallizes in the tillmannsite structure, whereas II-IV adopt new structure types: (I) I4, Z = 2, a = 7.7095(2) A, c = 4.6714(2) A, 730 structure factors, 24 parameters, R[F2 > 2sigma(F2)] = 0.0365; (II) I42d, Z = 4, a = 12.6295(13) A, c = 12.566(3) A, 1524 structure factors, 55 parameters, R[F2 > 2sigma(F2)] = 0.0508; (III) C2, Z = 4, a = 9.9407(18) A, b = 5.5730(8) A, c = 7.1210(19) A, beta = 94.561(10) degrees , 1129 structure factors, 48 parameters, R[F2 > 2sigma(F2)] = 0.0358; (IV) P31c, Z = 2, a = 6.0261(9) A, c = 21.577(4) A, 1362 structure factors, 52 parameters, R[F2 > 2sigma(F2)] = 0.0477. The most striking structural features of I, II, and IV are the formation of tetrahedral cluster cations (Ag3Hg)3+ and (Ag2Hg2)4+, respectively, built of statistically distributed Ag and Hg atoms with a metal-metal distance of about 2.72 A. The electronic structure of these clusters can formally be considered as two-electron-four-center bonding. The crystal structure of III differs from the protrusive structure types insofar as silver and mercury are located on distinct crystallographic sites without a notable metal-metal interaction >3.55 A. All crystal structures are completed by tetrahedral oxo anions XO4(3-) (X = VV, AsV) and for IV additionally by a mercurate group, HgO2(2-).

  7. [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

  8. 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.

  9. MBE HgCdTe for HDVIP Devices: Horizontal Integration in the US HgCdTe FPA Industry

    NASA Astrophysics Data System (ADS)

    Aqariden, F.; Elsworth, J.; Zhao, J.; Grein, C. H.; Sivananthan, S.

    2012-10-01

    Molecular beam epitaxy (MBE) growth of HgCdTe offers the possibility of fabricating multilayer device structures with an almost unlimited choice of infrared sensor designs for focal-plane array (FPA) fabrication. HgCdTe offers two major advantages that explain its dominance in the infrared photon detector marketplace. The thermal generation rate per unit volume of the material is lower and the quantum efficiency for photon absorption in the infrared is higher in HgCdTe than in any competing material—it yields devices with quantum efficiencies as high as 0.99. Recently, EPIR Technologies and DRS Infrared Technologies agreed to collaborate and examine: (i) the feasibility of employing MBE HgCdTe in the fabrication of high-density vertically interconnected photodiodes (HDVIPs), which are usually fabricated with liquid-phase epitaxy material, and (ii) the potential benefits of horizontal integration, with EPIR supplying the MBE materials to DRS for device and array fabrication. The team designed and developed passivation-absorber-passivation structures that are heavily used by DRS. This paper provides an overview of the characteristics of HDVIP devices and arrays fabricated from MBE HgCdTe and the anticipated advantages of horizontal integration in the industry. Material growth, device fabrication, and test results are presented.

  10. 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...

  11. 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.

  12. 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...

  13. 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

  14. 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 20 ng g(-1). The model finds out some correlations within the parameters affect the measurements precision and predicts suitable sample measurement precisions for Hg concentrations from 5 ng g(-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

  15. 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.

  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. Lifetime Measurements and Coulomb Excitation of Light Hg Nuclei

    NASA Astrophysics Data System (ADS)

    Petts, A.; Butler, P. A.; Grahn, T.; Blazhev, A.; Bree, N.; Bruyneel, B.; Cederkäll, J.; Clement, E.; Cocolios, T. E.; Dewald, A.; Eberth, J.; Fraile, L.; Fransen, C.; Hornillos, M. B. Gómez; Greenlees, P. T.; Görgen, A.; Guttormsen, M.; Hadynska, K.; Helariutta, K.; Herzberg, R.-D.; Huyse, M.; Jenkins, D. G.; Jolie, J.; Jones, P.; Julin, R.; Juutinen, S.; Ketelhut, S.; Knapen, S.; Kröll, T.; Krü; cken, R.; Larsen, A. C.; Leino, M.; Ljungvall, J.; Maierbeck, P.; Marley, P. L.; Melon, B.; Napiorkowski, P. J.; Nyman, M.; Page, R. D.; Pakarinen, J.; Pascovici, G.; Patronis, N.; Peura, P. J.; Piselli, E.; Pissulla, Th.; Rahkila, P.; Reiter, P.; Sarén, J.; Scheck, M.; Scholey, C.; Semchenkov, A.; Siem, S.; Stefanescu, I.; Sorri, J.; Uusitalo, J.; Van de Walle, J.; Van Duppen, P.; Voulot, D.; Wadsworth, R.; Warr, N.; Weisshaar, D.; Wenander, F.; Zielinska, M.

    2009-01-01

    Two complementary experimental programs have taken place to investigate the origin and evolution of shape coexistence in the light mercury region. Recoil Distance Doppler-shift measurements were performed at the University of Jyväskylä utilizing the Köln plunger device in conjunction with the JUROGAM+RITU+GREAT setup. In addition, Coulomb excitation measurements of 184,186,188Hg were performed at REX-ISOLDE using the MINIBALL Ge-detector array. The results of the lifetime measurements of the yrast states up to Iπ = 10+ in 182Hg are reported. Preliminary analysis of the Coulomb excitation data is also discussed.

  18. Mercury (Hg) burden in children: the impact of dental amalgam.

    PubMed

    Al-Saleh, Iman; Al-Sedairi, Al Anoud

    2011-07-15

    The risks and benefits of using mercury (Hg) in dental amalgam have long been debated. This study was designed to estimate Hg body burden and its association with dental amalgam fillings in 182 children (ages: 5-15 years) living in Taif City. Hg was measured in urine (UHg), hair (HHg) and toenails (NHg) by the Atomic Absorption Spectrophotometer with Vapor Generator Accessory system. Urinary Hg levels were calculated as both micrograms per gram creatinine (μg/g creatinine) and micrograms per liter (μg/L). We found that children with amalgam fillings (N=106) had significantly higher UHg-C levels than children without (N=76), with means of 3.763 μg/g creatinine versus 3.457 μg/g creatinine, respectively (P=0.019). The results were similar for UHg (P=0.01). A similar pattern was also seen for HHg, with means of 0.614 μg/g (N=97) for children with amalgam versus 0.242 μg/g (N=74) for those without amalgam fillings (P=0). Although the mean NHg was higher in children without amalgam (0.222 μg/g, N=61) versus those with (0.163 μg/g, N=101), the relationship was not significant (P=0.069). After adjusting for many confounders, the multiple logistic regression model revealed that the levels of UHg-C and HHg were 2.047 and 5.396 times higher, respectively, in children with dental amalgam compared to those without (P<0.01). In contrast, a significant inverse relationship was seen between NHg levels and dental amalgam fillings (P=0.003). Despite the controversy surrounding the health impact of dental amalgam, this study showed some evidence that amalgam-associated Hg exposure might be related with symptoms of oral health, such as aphthous ulcer, white patches, and a burning-mouth sensation. Further studies are needed to reproduce these findings. The present study showed that significant numbers of children with or without amalgam had Hg levels exceeding the acceptable reference limits. The detrimental neurobehavioral and/or nephrotoxic effects of such an increased Hg on

  19. 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.

  20. Lifetime Measurements and Coulomb Excitation of Light Hg Nuclei

    SciTech Connect

    Petts, A.; Butler, P. A.; Grahn, T.; Herzberg, R.-D.; Page, R. D.; Pakarinen, J.; Scheck, M.; Blazhev, A.; Bruyneel, B.; Dewald, A.; Eberth, J.; Fransen, C.; Jolie, J.; Melon, B.; Pascovici, G.; Pissulla, Th.; Reiter, P.; Warr, N.; Weisshaar, D.; Bree, N.

    2009-01-28

    Two complementary experimental programs have taken place to investigate the origin and evolution of shape coexistence in the light mercury region. Recoil Distance Doppler-shift measurements were performed at the University of Jyvaeskylae utilizing the Koeln plunger device in conjunction with the JUROGAM+RITU+GREAT setup. In addition, Coulomb excitation measurements of {sup 184,186,188}Hg were performed at REX-ISOLDE using the MINIBALL Ge-detector array. The results of the lifetime measurements of the yrast states up to I{sup {pi}} = 10{sup +} in {sup 182}Hg are reported. Preliminary analysis of the Coulomb excitation data is also discussed.

  1. 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.

  2. Electrochemical isotope effect and lithium isotope separation.

    PubMed

    Black, Jay R; Umeda, Grant; Dunn, Bruce; McDonough, William F; Kavner, Abby

    2009-07-29

    A large electrochemical isotopic effect is observed upon the electrodeposition of lithium from solutions of propylene carbonate producing isotopically light metal deposits. The magnitude of fractionation is controlled by the applied overpotential and is largest close to equilibrium. Calculated partition function ratios for tetrahedrally coordinated lithium complexes and metallic lithium predict an equilibrium fractionation close to that measured experimentally.

  3. 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.

  4. 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

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 40 CFR Appendix A to Subpart Uuuuu - Hg Monitoring Provisions

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... no later than the applicable date in § 63.10005(g). 4.1.1Hg CEMS. Table A-1, below, summarizes the... Table A-1. The CE on each day of the test must either meet the main performance specification or the alternative specification in Table A-1. 4.1.1.2Linearity Check. Perform the linearity check using low,...

  10. 40 CFR Appendix A to Subpart Uuuuu... - Hg Monitoring Provisions

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... of this appendix. 2.2Primary and Backup Monitoring Systems. In the electronic monitoring plan... a unique monitoring system in the electronic monitoring plan. Each redundant backup monitoring... monitoring system in the electronic monitoring plan. Non-redundant backup Hg CEMS must complete the...

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

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... of this appendix. 2.2Primary and Backup Monitoring Systems. In the electronic monitoring plan... a unique monitoring system in the electronic monitoring plan. Each redundant backup monitoring... monitoring system in the electronic monitoring plan. Non-redundant backup Hg CEMS must complete the...

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

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... (CONTINUED) STANDARDS OF PERFORMANCE FOR NEW STATIONARY SOURCES Standards of Performance for Electric Utility... must not discharge into the atmosphere any gases from a new affected source that contain Hg in excess.... The International System of Units (SI) equivalent is 0.0025 ng/J. (2) For each coal-fired...

  13. 46 CFR 53.01-5 - Scope (modifies HG-100).

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... IV of the ASME Boiler and Pressure Vessel Code (incorporated by reference; see 46 CFR 53.01-1). Table... Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING HEATING BOILERS General Requirements § 53.01-5 Scope (modifies HG-100). (a) The regulations in this part apply to...

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

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... IV of the ASME Boiler and Pressure Vessel Code (incorporated by reference; see 46 CFR 53.01-1). Table... Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING HEATING BOILERS General Requirements § 53.01-5 Scope (modifies HG-100). (a) The regulations in this part apply to...

  15. 46 CFR 53.01-5 - Scope (modifies HG-100).

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... IV of the ASME Boiler and Pressure Vessel Code (incorporated by reference; see 46 CFR 53.01-1). table... Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING HEATING BOILERS General Requirements § 53.01-5 Scope (modifies HG-100). (a) The regulations in this part apply to...

  16. 46 CFR 53.01-5 - Scope (modifies HG-100).

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... IV of the ASME Boiler and Pressure Vessel Code (incorporated by reference; see 46 CFR 53.01-1). Table... Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING HEATING BOILERS General Requirements § 53.01-5 Scope (modifies HG-100). (a) The regulations in this part apply to...

  17. 46 CFR 53.01-5 - Scope (modifies HG-100).

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... IV of the ASME Boiler and Pressure Vessel Code (incorporated by reference; see 46 CFR 53.01-1). table... Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING HEATING BOILERS General Requirements § 53.01-5 Scope (modifies HG-100). (a) The regulations in this part apply to...

  18. Isotope reference materials

    USGS Publications Warehouse

    Coplen, Tyler B.

    2010-01-01

    Measurement of the same isotopically homogeneous sample by any laboratory worldwide should yield the same isotopic composition within analytical uncertainty. International distribution of light element isotopic reference materials by the International Atomic Energy Agency and the U.S. National Institute of Standards and Technology enable laboratories to achieve this goal.

  19. Statistical clumped isotope signatures.

    PubMed

    Röckmann, T; Popa, M E; Krol, M C; Hofmann, M E G

    2016-08-18

    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.

  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. Statistical clumped isotope signatures

    NASA Astrophysics Data System (ADS)

    Röckmann, T.; Popa, M. E.; Krol, M. C.; Hofmann, M. E. G.

    2016-08-01

    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.

  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. 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.

  4. 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.

  5. 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.

  6. Photochemical formation of CH 3HgH in Hg/CH 4/Ar matrices studied by FTIR spectroscopy

    NASA Astrophysics Data System (ADS)

    Legay-Sommaire, N.; Legay, F.

    1994-01-01

    Mixed matrices of methane or deuterated methane and argon doped with mercury have been irradiated with a KrF laser at 249 nm. Methylmercury hydride is formed by reaction of Hg excited to the 3P 1 state with CH 4 or CD 4. The reaction products were identified by Fourier transform infrared spectrometry.

  7. 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.

  8. 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.

  9. 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.

  10. 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

  11. 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.

  12. 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.

  13. Geochemical assessment of Hg pollution in gold mining sites

    NASA Astrophysics Data System (ADS)

    Rodrigues-Filho, S.; Villas Bôas, R. C.

    2003-05-01

    The increasing societal demand for actions and strategies towards sustainability of small-scale gold mining in developing countries has led experts to face the challenge of managing the harzards associated with mercury pollution from active and abandoned mine sites. Mercury pollution in drainage systems and its health effects are the most frequent subjects on environmental researchs dealing with small-scale gold mining worldwide. Also, filling of river beds with mineral matter originated from runoff of abandoned mining waste piles and tailings generally causes both silting of waterways and elevation of Hg concentrations in the environment. This paper summarizes the main results concerning the assessment of Hg pollution in Amazon drainage systems accomplished by the authors in the last decade in Brazil.

  14. 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.

  15. 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.

  16. Mercury speciation analyses in HgCl(2)-contaminated soils and groundwater--implications for risk assessment and remediation strategies.

    PubMed

    Bollen, A; Wenke, A; Biester, H

    2008-01-01

    Since the 19th century, mercury(II)chloride (HgCl(2)) has been used on wood impregnation sites to prevent wooden poles from decay, leaving behind a legacy of highly contaminated soil/aquifer systems. Little is known about species transformation and mobility of HgCl(2) in contaminated soils and groundwater. At such a site the behaviour of HgCl(2) in soils and groundwater was investigated to assist in risk assessment and remediation. The soil is low in organic carbon and contains up to 11,000 mg Hg/kg. Mercury (Hg) concentrations in groundwater decrease from 230 to 0.5 microg/l within a distance of 1.3 km. Hg species transformations in soil and aqueous samples were analysed by means of solid-phase Hg pyrolysis and CV-AAS. In aqueous samples, Hg species were distinguished between ionic/reactive Hg and complex-bound Hg. Potential mobility of Hg in soils was studied through batch experiments. Most Hg in the soil is matrix-bound HgCl(2), whereas in the aquifer secondary formation to Hg(0) could be observed. Aqueous Hg speciation in groundwater and soil solutions shows that an average of 84% of soluble Hg exists as easily reducible, inorganic Hg species (mostly HgCl(2)). The proportion of complex-bound Hg increases with distance due to the transformation of inorganic HgCl(2). The frequent occurrence of Hg(0) in the aquifer suggests the formation and degassing of Hg(0), which is, in addition to dilution, an important process, lowering Hg concentrations in the groundwater. High percentage of mobile Hg (3-26%) and low seepage fluxes will result in continuous Hg release over centuries requiring long-term groundwater remediation. Results of soluble Hg speciation suggest that filtering materials should be adapted to ionic Hg species, e.g. specific resins or amalgamating metal alloys.

  17. 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

  18. 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.

  19. 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.

  20. Unusual speciation and retention of Hg at a coal-fired power plant.

    PubMed

    Córdoba, Patricia; Maroto-Valer, M; Ayora, Carlos; Perry, Ron; Rallo, Manuela; Font, Oriol; Izquierdo, Maria; Querol, Xavier

    2012-07-17

    An unusual and different speciation of Hg in the outgoing gaseous stream of the flue gas desulfurization (OUT-FGD) system was revealed at two Spanish power plants (PP1 and PP2) equipped with a forced oxidation wet FGD system with water recirculation to the scrubber. At PP1 and PP2, a high proportion of Hg escapes from the electrostatic precipitator in gaseous form, Hg(2+) (75-86%) being the species that enters the FGD. At PP1 Hg(0) (71%) was the prevalent Hg OUT-FGD species, whereas at PP2 Hg(2+) was the prevalent Hg OUT-FGD species in 2007 (66%) and 2008 (87%). The unusual speciation of gaseous Hg OUT-FGD and the different Hg retentions between 2007 and 2008 at PP2 were attributable to the evaporation of HgCl(2) particles from the aqueous phase of gypsum slurry in the OUT-FGD gas and the Al additive used at PP2, respectively. The Al additive induced the retention of Hg as HgS in the 2007 FGD gypsum, thus reducing gaseous emissions of Hg in the OUT-FGD gas.

  1. 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

  2. Dipole strength distributions in the stable Ba isotopes 134 138 Ba : A study in the mass region of a nuclear shape transition

    NASA Astrophysics Data System (ADS)

    Scheck, M.; von Garrel, H.; Tsoneva, N.; Belic, D.; von Brentano, P.; Fransen, C.; Gade, A.; Jolie, J.; Kneissl, U.; Kohstall, C.; Linnemann, A.; Nord, A.; Pietralla, N.; Pitz, H. H.; Stedile, F.; Stoyanov, C.; Werner, V.

    2004-10-01

    The low-lying dipole strength distributions in the odd-mass isotopes 135,137 Ba were studied in nuclear resonance fluorescence experiments (NRF) performed at the Stuttgart Dynamitron facility using bremsstrahlung beams with end point energies of 4.1, 3.1, and 2.5 MeV . Numerous excited states, most of them unknown so far, were observed in the excitation energy range up to 4 MeV . Detailed spectroscopic information has been obtained on excitation energies, decay widths, decay branching ratios, and transition probabilities. The results for 137Ba are compared with calculations in the framework of the Quasiparticle-Phonon Model. The new data for 135,137 Ba complete the systematics of low-lying dipole excitations as observed for the even Ba isotopes 134,136,138 Ba in previous NRF experiments in Stuttgart. The complete systematics within the Ba isotopic chain, exhibiting a nuclear shape transition, is discussed with respect to E1 two-phonon excitations, M1 scissors mode excitations, and in regard to the new critical point symmetries.

  3. 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.

  4. 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

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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

  11. PRINCIPAL ISOTOPE SELECTION REPORT

    SciTech Connect

    K. D. Wright

    1998-08-28

    Utilizing nuclear fuel to produce power in commercial reactors results in the production of hundreds of fission product and transuranic isotopes in the spent nuclear fuel (SNF). When the SNF is disposed of in a repository, the criticality analyses could consider all of the isotopes, some principal isotopes affecting criticality, or none of the isotopes, other than the initial loading. The selected set of principal isotopes will be the ones used in criticality analyses of the SNF to evaluate the reactivity of the fuel/waste package composition and configuration. This technical document discusses the process used to select the principal isotopes and the possible affect that these isotopes could have on criticality in the SNF. The objective of this technical document is to discuss the process used to select the principal isotopes for disposal criticality evaluations with commercial SNF. The principal isotopes will be used as supporting information in the ''Disposal Criticality Analysis Methodology Topical Report'' which will be presented to the United States Nuclear Regulatory Commission (NRC) when approved by the United States Department of Energy (DOE) Office of Civilian Radioactive Waste Management (OCRWM).

  12. Methylmercury accumulation and elimination in mink (Neovison vison) hair and blood: results of a controlled feeding experiment using stable isotope tracers.

    PubMed

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

    2014-12-01

    Concentrations of metals in hair are used often to develop pharmacokinetic models for both animals and humans. Although data on uptake are available, elimination kinetics are less well understood; stable isotope tracers provide an excellent tool for measuring uptake and elimination kinetics. In the present study, methylmercury concentrations through time were measured in the hair and blood of mink (Neovison vison) during a controlled 60-d feeding experiment. Thirty-four mink were fed a standard fish-based diet for 14 d, at the end of which (day 0), 4 mink were sacrificed to determine baseline methylmercury (MeHg) concentrations. From day 0 to day 10, the remaining mink were fed a diet consisting of the base diet supplemented with 0.513 ± 0.013 µg Me(199) Hg/g and 0.163 ± 0.003 µg Me(201) Hg/g. From day 10 to day 60, mink were fed the base diet supplemented with 0.175 ± 0.024 µg Me(201) Hg/g. Animals were sacrificed periodically to determine accumulation of Me(201) Hg in blood and hair over the entire 60-d period and the elimination of Me(199) Hg over the last 50 d. Hair samples, collected from each mink and cut into 2.0-mm lengths, indicate that both isotopes of MeHg appeared in the hair closest to the skin at approximately day 10, with concentrations in the hair reaching steady state from day 39 onward. The elimination rate of Me(199) Hg from the blood was 0.05/d, and the ratio of MeHg in the hair to blood was 119. A large fraction of MeHg (22% to >100%) was stored in the hair, suggesting that in fur-bearing mammals the hair is a major route of elimination of MeHg from the body.

  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.

  14. 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.

  15. 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

  16. 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...

  17. 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

  18. 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.

  19. 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.

  20. 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.

  1. 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

  2. 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

  3. 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

  4. 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

  5. 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.

  6. 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.

  7. 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.

  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. 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.

  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. 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.

  12. 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

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. (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.

  18. 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).

  19. 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.

  20. Synthesis and growth of HgI{sub 2} nanocrystals in a glass matrix: Heat treatment

    SciTech Connect

    Condeles, J. F. E-mail: ricssilva@yahoo.com.br; Silva, R. S. E-mail: ricssilva@yahoo.com.br; Silva, A. C. A.; Dantas, N. O.

    2014-08-14

    Mercury iodide (HgI{sub 2}) nanocrystals (NCs) were successfully grown in a barium phosphate glass matrix synthesized by fusion. Growth control of HgI{sub 2} NCs was investigated by Atomic Force Microscopy (AFM), Optical Absorption (OA), Fluorescence (FL), and X-ray diffraction (XRD). AFM images reveal the formation of HgI{sub 2} nanocrystals in host glass matrix. HgI{sub 2} NCs growth was evidenced by an OA and FL band red-shift with increasing annealing time. XRD measurements revealed the β crystalline phase of the HgI{sub 2} nanocrystals.

  1. Sorption kinetics of Hg and HgCl[sub 2] on Kirkwood-Cohansey aquifer sediments from the New Jersey Coastal Plain

    SciTech Connect

    MacLeod, C.; Peterson, J. . Dept. of Geological and Geophysical Sciences)

    1992-01-01

    Anomalously high Hg concentrations have been detected from domestic wells in the Kirkwood-Cohansey Aquifer System, New Jersey Coastal Plain. Mercury concentrations ranging from 0.2--83.0 [mu]g/l in relatively shallow wells ([lt] 100 feet) have been detected. Concentrations in excess of 2.0 [mu]g/l, (the USEPA Drinking Water Standard) have been detected in wells where the Cohansey Sand is overlain by the Bridgeton Formation; a fluvial iron-rich sand with some gravelly channel deposits containing goethite and gibbsite nodules. In this study, Bridgeton Fm. sediments were used to determine the sorption kinetics for solutions containing HgCl[sub 2] and for solutions containing dissolved elemental Hg in order to assess the potential for the Bridgeton sediments to act as a conduit for Hg mobilized from the surface. Results of batch equilibrium experiments suggest that dissolved elemental Hg sorbs to Bridgeton sediments by a risk-order kinetic process. Sorption of the Hg proceeded exponentially and equilibrium was reached within 14 hours. The sorption kinetics for the HgCl[sub 2] solutions, however, appear to be of a second or higher order. For this compound sorption to the sediments begins exponentially, but after 6 hours desorption into the water begins to predominate followed by a slower exponential sorption step that requires nearly 36 hours to reach equilibrium. These experiments illustrate the necessity of determining the distribution coefficients of possible source compounds when attempting to evaluate mobilization potential of a contaminant in the unsaturated zone. Moreover, these data also suggest that HgCl[sub 2], a seed dressing for corn, medial bacteriacide, and embalming fluid ingredient, is more mobile in the environment than dissolved elemental Hg. Consequently, the ground water contamination potential appears to be greater for HgCl[sub 2] than for elemental Hg.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. Thiourea catalysis of MeHg ligand exchange between natural dissolved organic matter and a thiol-functionalized resin: a novel method of matrix removal and MeHg preconcentration for ultratrace Hg speciation analysis in freshwaters.

    PubMed

    Vermillion, Brian R; Hudson, Robert J M

    2007-05-01

    Ultratrace analysis of dissolved MeHg in freshwaters requires both dissociation of MeHg from strong ligands in the sample matrix and preconcentration for detection. Existing solid phase extraction methods generally do not efficiently adsorb MeHg from samples containing high concentrations of natural dissolved organic matter. We demonstrate here that the addition of 10-60 mM thiourea (TU) quantitatively releases MeHg from the dissolved matrix of freshwater samples by forming a more labile complex (MeHgTU+) that quantitatively exchanges MeHg with thiol-functionalized resins at pH approximately 3.5 during column loading. The contents of these columns were efficiently eluted with acidified TU and MeHg was analyzed by Hg-TU complex ion chromatography with cold-vapor atomic fluorescence spectrometry detection. Routinely more than 90% of MeHg was recovered with good precision (average relative standard deviation of 6%) from natural waters-obtained from pools and saturated sediments of wetlands and from rivers-containing up to 68.7 mg C L-1 dissolved organic matter. With the preconcentration step, the method detection limit of 0.29 pg absolute or 0.007 ng L-1 in 40-mL samples is equivalent to that of the current state-of-the- art as practiced by skilled analysts. MeHg in 20-50-mL samples was completely trapped. On the basis of our knowledge of the chemistry of the process, breakthrough volume should depend on the concentrations of TU and H+. At a TU concentration of 12 mM breakthrough occurred between 50 and 100 mL, but overall adsorption efficiency was still 85% at 100 mL. Formation of artifactual MeHg is minimal; only about 0.7% of ambient MeHg is artifactual as estimated from samples spiked with 4 microg L-1 HgII. PMID:17342536

  8. 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

  9. 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

  10. Manila clams from Hg polluted sediments of Marano and Grado lagoons (Italy) harbor detoxifying Hg resistant bacteria in soft tissues.

    PubMed

    Baldi, Franco; Gallo, Michele; Marchetto, Davide; Faleri, Claudia; Maida, Isabel; Fani, Renato

    2013-08-01

    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 5mgl(-1) HgCl2 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.

  11. 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).

  12. 640 X 480 Pace HgCdTe FPA

    NASA Astrophysics Data System (ADS)

    Kozlowski, Lester J.; Bailey, Robert B.; Cabelli, Scott A.; Cooper, Donald E.; McComas, Gail D.; Vural, Kadri; Tennant, William E.

    1992-12-01

    A hybrid HgCdTe 640 X 480 infrared (IR) focal plane array (FPA) that meets the sensitivity, resolution, and field-of-view requirements of high-performance medium wavelength infrared (MWIR) imaging systems has been developed. The key technology making this large, high sensitivity device producible is the epitaxial growth of HgCdTe on a CdTe-buffered, sapphire substrate (referred to as PACE, for Producible Alternative to CdTe for Epitaxy; PACE-I refers to sapphire). The device offers TV resolution with excellent sensitivity at temperatures below 120 K. Mean NE(Delta) T as low as 13 mK has been achieved at operating temperatures < 130 K, which is about an order of magnitude better than has been achieved with PtSi 640 X 480 FPAs. In addition, the latter require cooling to

  13. 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.

  14. 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.

  15. 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.

  16. A State-of-the-Science Hg Redox Mechanism for Atmospheric Models: Constraints from Observations and Global Implications

    NASA Astrophysics Data System (ADS)

    Horowitz, H.; Jacob, D. J.; Amos, H. M.; Streets, D. G.; Zhang, Y.; Dibble, T. S.; Slemr, F.; Sunderland, E. M.

    2015-12-01

    Mercury (Hg) in the atmosphere cycles between two redox forms, Hg0 and HgII. Hg0 has a lifetime of ~1 year allowing near-global transport, while HgII is efficiently removed by deposition within weeks. Understanding atmospheric Hg redox chemistry is critical to determining the patterns of deposition to the surface, where Hg can be transformed to the bioaccumulative neurotoxin, methylmercury. We present a state-of-the-science redox mechanism for use in atmospheric models, with new theoretical data, which we implement in a global 3-D chemical transport model (GEOS-Chem). We evaluate our simulation against atmospheric observations and examine implications for Hg deposition. Modeled HgII wet deposition depends on the oxidation of anthropogenic, ocean, and soil Hg0 emissions and the reduction of emitted anthropogenic HgII. We present a new global anthropogenic atmospheric Hg emissions inventory for 1990 - 2010 with improved speciation of power plant emissions and regional commercial Hg emissions. The seasonal cycle of ocean evasion is also critical to atmospheric Hg variability. We present an advance in our ability to model atmosphere-ocean exchange of Hg, through more realistic ocean circulation from the 3-D MITgcm. Our results suggest Br is the dominant oxidant in the stratosphere, consistent with constraints from aircraft observations of the Hg gradient with depth into the stratosphere. The proposed redox mechanism leads to increased HgII deposition to the Tropics, with implications for tropical surface ocean enrichment, and decreased deposition to the Southern Ocean. Within the uncertainty of Hg0 oxidation rates, we find atmospheric HgII reduction is still needed. We find changes in speciated Hg emissions due to emissions controls can explain recent observed regional trends in atmospheric Hg. These have shifted power plant impacts to relatively more global than local Hg deposition. Coupling to the more realistic 3-D ocean model improves simulated atmospheric Hg

  17. 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

  18. Meteoritic Sulfur Isotopic Analysis

    NASA Technical Reports Server (NTRS)

    Thiemens, Mark H.

    1996-01-01

    Funds were requested to continue our program in meteoritic sulfur isotopic analysis. We have recently detected a potential nucleosynthetic sulfur isotopic anomaly. We will search for potential carriers. The documentation of bulk systematics and the possible relation to nebular chemistry and oxygen isotopes will be explored. Analytical techniques for delta(sup 33), delta(sup 34)S, delta(sup 36)S isotopic analysis were improved. Analysis of sub milligram samples is now possible. A possible relation between sulfur isotopes and oxygen was detected, with similar group systematics noted, particularly in the case of aubrites, ureilites and entstatite chondrites. A possible nucleosynthetic excess S-33 has been noted in bulk ureilites and an oldhamite separate from Norton County. High energy proton (approximately 1 GeV) bombardments of iron foils were done to experimentally determine S-33, S-36 spallogenic yields for quantitation of isotopic measurements in iron meteorites. Techniques for measurement of mineral separates were perfected and an analysis program initiated. The systematic behavior of bulk sulfur isotopes will continue to be explored.

  19. Sputter cleaning and dry oxidation of CdTe, HgTe, and Hg 0.8Cd 0.2Te surfaces

    NASA Astrophysics Data System (ADS)

    Solzbach, U.; Richter, H. J.

    1980-07-01

    The analyses of CdTe, HgTe, and Hg 0.8Cd 0.2Te surfaces by XPS and LEED after Ar + sputtering and after the subsequent onset of a dry oxidation are described, and a quantitative evaluation of the XPS spectra is attempted. The results are: Ar + sputtering yields a perfect unreconstructed CdTe surface of stoichiometric composition, whereas the composition of sputtered HgTe and Hg 0.8Cd 0.2Te surfaces generally deviates from the stoichiometry of the respective compound. This deviation is a function of the energy of the Ar ions (1 to 15 keV) and is characterized by an increasing deficit in Hg as the ion energy is raised. The Hg deficit of sputtered Hg 0.8Cd 0.2Te surfaces is substitutionally compensated by an equivalent increase in Cd, and due to this substitution the resulting surfaces are sufficiently ordered to display a distinct LEED pattern. The oxidation of sputtered CdTe, HgTe, and Hg 0.8Cd 0.2Te surfaces in an O 2 atmosphere is an extremely slow process. Therefore, the surfaces to be oxidized were additionally exposed to UV radiation (low pressure mercury lamp), and due to UV generated ozone as an oxidizing agent ultrathin native oxide layers of up to 15 Å thickness were readily obtained. The predominant constituents of these native oxide layers on Hg 0.8Cd 0.2Te are concluded to be CdTeO 3 and TeO 2.

  20. Bioaccumulation of As, Cd, Cr, Hg(II), and MeHg in killifish (Fundulus heteroclitus) from amphipod and worm prey.

    PubMed

    Dutton, Jessica; Fisher, Nicholas S

    2011-08-15

    Elevated metal levels in fish are a concern for the fish themselves, their predators, and possibly humans who consume contaminated seafood. Metal bioaccumulation models often rely on assimilation efficiencies (AEs) of ingested metals and loss rate constants after dietary exposure (k(ef)s). These models can be used to better understand processes regulating metal accumulation and can be used to make site-specific predictions of metal concentrations in animal tissues. Fish often consume a varied diet, and prey choice can influence these two parameters. We investigated the trophic transfer of As, Cd, Cr, Hg(II), and methylmercury (MeHg) from a benthic amphipod (Leptocheirus plumulosus) and an oligochaete (Lumbriculus variegatus) to killifish (Fundulus heteroclitus) using gamma-emitting radioisotopes. Except for MeHg, AEs varied between prey type. AEs were highest for MeHg (92%) and lowest for Cd (2.9-4.5%) and Cr (0.2-4%). Hg(II) showed the largest AE difference between prey type (14% amphipods, 24% worms). For Cd and Hg(II) k(ef)s were higher after consuming amphipods than consuming worms. Tissue distribution data shows that Cd and Hg(II) were mainly associated with the intestine, whereas As and MeHg were transported throughout the body. Calculated trophic transfer factors (TTFs) suggest that MeHg is likely to biomagnify at this trophic step at all ingestion rates, whereas As, Cd, Cr, and Hg(II) will not. Data collected in this study and others indicate that using one prey item to calculate AE and k(ef) could lead to an over- or underestimation of these parameters. PMID:21658746

  1. 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.

  2. Certification of methylmercury in cod fish tissue certified reference material by species-specific isotope dilution mass spectrometric analysis.

    PubMed

    Inagaki, Kazumi; Kuroiwa, Takayoshi; Narukawa, Tomohiro; Yarita, Takashi; Takatsu, Akiko; Okamoto, Kensaku; Chiba, Koichi

    2008-07-01

    A new cod fish tissue certified reference material, NMIJ CRM 7402-a, for methylmercury analysis was certified by the National Metrological Institute of Japan in the National Institute of Advanced Industrial Science and Technology (NMIJ/AIST). Cod fish was collected from the sea close to Japan. The cod muscle was powdered by freeze-pulverization and was placed into 600 glass bottles (10 g each), which were sterilized with gamma-ray irradiation. The certification was carried out using species-specific isotope dilution gas chromatography inductively coupled plasma mass spectrometry (SSID-GC-ICPMS), where (202)Hg-enriched methylmercury (MeHg) was used as the spike compound. In order to avoid any possible analytical biases caused by nonquantitative extraction, degradation and/or formation of MeHg in sample preparations, two different extraction methods (KOH/methanol and HCl/methanol extractions) were performed, and one of these extraction methods utilized two different derivatization methods (ethylation and phenylation). A double ID method was adopted to minimize the uncertainty arising from the analyses. In order to ensure not only the reliability of the analytical results but also traceability to SI units, the standard solution of MeHg used for the reverse-ID was prepared from high-purity MeHg chloride and was carefully assayed as follows: the total mercury was determined by ID-ICPMS following aqua regia digestion, and the ratio of Hg as MeHg to the total Hg content was estimated by GC-ICPMS. The certified value given for MeHg is 0.58 +/- 0.02 mg kg(-1) as Hg.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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

  8. 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

  9. 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

  10. 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.

  11. The effect of electrode process on properties of HgCdTe detectors

    NASA Astrophysics Data System (ADS)

    Wang, Nili; Liu, Xiang-yang; Lan, Tian-yi; Liu, Shi-jia; Zhao, Shui-ping; Zhou, Qing; Li, Xiangyang

    2014-11-01

    Performance of HgCdTe devices was limited by many factors such as materials and techniques, etc. And the electrical characteristics of electrode contacts on HgCdTe played important roles - Because Ar Ion Beam Etching could make the conductivity type conversion of p-type HgCdTe material, it was used to obtain n-type electrode area on the slight-p type HgCdTe material. Variable magnetic field Hall measurements were performed on n-type and slight p-type HgCdTe material before and after Ar Ion Beam Etching at 77 K. The mobility spectrum analysis (MSA) technique was employed in this paper to obtain the electrical parameter of HgCdTe. Comparing the electrical parameters of HgCdTe before and after etching, we knew that Ar Ion etching formed high doping concentration n-type area on slight p-type HgCdTe. The minority carrier lifetime of HgCdTe was studied using the photoconductive decay technique. By measuring the minority carrier lifetime of the same HgCdTe material with or without n-type electrode, it was found that the minority carrier lifetime of slight p-type HgCdTe with n-type electrode was higher than HgCdTe that was without n-type electrode at low temperature. The results showed that the n-type electrode could improve the minority carrier lifetime of slight p-type HgCdTe. In addition, by changing the distance of the n-type electrode area to the photosensitive area, it was researched that the impact of n-type electrode area on the device performance. With the decrease of distance, the device performance improved. It was proved that n-type electrode areas also could improve the performance by device fabrication.

  12. Plasma isotope separation methods

    SciTech Connect

    Grossman, M.W. ); Shepp, T.A. )

    1991-12-01

    Isotope separation has many important industrial, medical, and research applications. Large-scale processes have typically utilized complex cascade systems; for example, the gas centrifuge. Alternatively, high single-stage enrichment processes (as in the case of the calutron) are very energy intensive. Plasma-based methods being developed for the past 15 to 20 years have attempted to overcome these two drawbacks. In this review, six major types of isotope separation methods which involve plasma phenomena are discussed. These methods are: plasma centrifuge, AVLIS (atomic vapor laser isotope separation), ion wave, ICR (ion-cyclotron resonance), calutron, and gas discharge. The emphasis of this paper is to describe the plasma phenomena in these major categories. An attempt was made to include enough references so that more detailed study or evaluation of a particular method could readily be pursued. A brief discussion of isotope separation using mass balance concepts is also carried out.

  13. Stable isotopes in mineralogy

    USGS Publications Warehouse

    O'Neil, J.R.

    1977-01-01

    Stable isotope fractionations between minerals are functions of the fundamental vibrational frequencies of the minerals and therefore bear on several topics of mineralogical interest. Isotopic compositions of the elements H, C, O, Si, and S can now be determined routinely in almost any mineral. A summary has been made of both published and new results of laboratory investigations, analyses of natural materials, and theoretical considerations which bear on the importance of temperature, pressure, chemical composition and crystal structure to the isotopic properties of minerals. It is shown that stable isotope studies can sometimes provide evidence for elucidating details of crystal structure and can be a powerful tool for use in tracing the reaction paths of mineralogical reactions. ?? 1977 Springer-Verlag.

  14. Isotopically controlled semiconductors

    SciTech Connect

    Haller, E.E.

    2004-11-15

    A review of recent research involving isotopically controlled semiconductors is presented. Studies with isotopically enriched semiconductor structures experienced a dramatic expansion at the end of the Cold War when significant quantities of enriched isotopes of elements forming semiconductors became available for worldwide collaborations. Isotopes of an element differ in nuclear mass, may have different nuclear spins and undergo different nuclear reactions. Among the latter, the capture of thermal neutrons which can lead to neutron transmutation doping, can be considered the most important one for semiconductors. Experimental and theoretical research exploiting the differences in all the properties has been conducted and will be illustrated with selected examples. Manuel Cardona, the longtime editor-in-chief of Solid State Communications has been and continues to be one of the major contributors to this field of solid state physics and it is a great pleasure to dedicate this review to him.

  15. Perchlorate isotope forensics.

    PubMed

    Böhlke, John Karl; Sturchio, Neil C; Gu, Baohua; Horita, Juske; Brown, Gilbert M; Jackson, W Andrew; Batista, Jacimaria; Hatzinger, Paul B

    2005-12-01

    Perchlorate has been detected recently in a variety of soils, waters, plants, and food products at levels that may be detrimental to human health. These discoveries have generated considerable interest in perchlorate source identification. In this study, comprehensive stable isotope analyses (37Cl/35Cl and 18O/17O/16O) of perchlorate from known synthetic and natural sources reveal systematic differences in isotopic characteristics that are related to the formation mechanisms. In addition, isotopic analyses of perchlorate extracted from groundwater and surface water demonstrate the feasibility of identifying perchlorate sources in contaminated environments on the basis of this technique. Both natural and synthetic sources of perchlorate have been identified in water samples from some perchlorate occurrences in the United States by the isotopic method. PMID:16316196

  16. Rare Isotope Accelerators

    NASA Astrophysics Data System (ADS)

    Savard, Guy

    2002-04-01

    The next frontier for low-energy nuclear physics involves experimentation with accelerated beams of short-lived radioactive isotopes. A new facility, the Rare Isotope Accelerator (RIA), is proposed to produce large amount of these rare isotopes and post-accelerate them to energies relevant for studies in nuclear physics, astrophysics and the study of fundamental interactions at low energy. The basic science motivation for this facility will be introduced. The general facility layout, from the 400 kW heavy-ion superconducting linac used for production of the required isotopes to the novel production and extraction schemes and the highly efficient post-accelerator, will be presented. Special emphasis will be put on a number of technical breakthroughs and recent R&D results that enable this new facility.

  17. Perchlorate isotope forensics

    USGS Publications Warehouse

    Böhlke, J.K.; Sturchio, N.C.; Gu, B.; Horita, J.; Brown, G.M.; Jackson, W.A.; Batista, J.; Hatzinger, P.B.

    2005-01-01

    Perchlorate has been detected recently in a variety of soils, waters, plants, and food products at levels that may be detrimental to human health. These discoveries have generated considerable interest in perchlorate source identification. In this study, comprehensive stable isotope analyses ( 37Cl/35Cl and 18O/17O/ 16O) of perchlorate from known synthetic and natural sources reveal systematic differences in isotopic characteristics that are related to the formation mechanisms. In addition, isotopic analyses of perchlorate extracted from groundwater and surface water demonstrate the feasibility of identifying perchlorate sources in contaminated environments on the basis of this technique. Both natural and synthetic sources of perchlorate have been identified in water samples from some perchlorate occurrences in the United States by the isotopic method. ?? 2005 American Chemical Society.

  18. The Hg-H2 system: Potential energy surfaces of the low-lying states, reactivity of the 6s6p states of Hg on H2, classical dynamic study of Hg(3P1)+H2 half collision

    NASA Astrophysics Data System (ADS)

    Bernier, A.; Millie, P.

    1988-04-01

    Potential energy surfaces for HgH2 have been calculated using a nonempirical relativistic effective core )potential incorporating configuration interaction by means of the CIPSI algorithm (configuration interaction by perturbation with multiconfigurational zeroth-order wave function selected by iterative process). Core-valence polarization and correlation energy are included via a perturbative treatment. Spin-orbit coupling is introduced through an effective Hamiltonian. These theoretical results are used to discuss the experimental ones for the Hg(3P1)+H2→HgH(X 2Σ+)+H reaction. The different behaviors of the two van der Waals complexes are explained. Dynamical studies and classical trajectories calculations confirm that the dominant pathway is a direct dissociation on the first excited surface and is responsible for a highly peaked rotational distribution of the HgH product, in agreement with experiment.

  19. Lifetimes of an excited superdeformed band in {sup 192}Hg

    SciTech Connect

    Ahmad, I.; Blumenthal, D.; Carpenter, M.P.

    1995-08-01

    An excited superdeformed band was identified in {sup 192}Hg and the lifetimes of its levels measured with the Doppler-shift attenuation method from data taken with the Eurogam spectrometer. The band is proposed to be based on the two-quasineutron (v[642]3/2 [512]5/2) configuration, which after a band crossing, becomes the (v[642]3/2 [752]5/2) configuration. The transition quadrupole moment Q{sub t} of the excited band is the same as that of the yrast SD band, within experimental errors. This suggests that the deformation of the SD minimum is robust with respect to quasiparticle excitation, despite the occupation of the deformation-driving v[752]5/2 level (from the j{sub 15/2} shell) after the band crossing.

  20. Optical characteristics of a HgBr excilamp

    SciTech Connect

    Malinina, A A; Malinin, A N; Shuaibov, A K

    2013-08-31

    Optical characteristics of a coaxial HgBr excilamp on multicomponent mercury dibromide vapour mixtures with helium, nitrogen and sulfur hexafluoride are investigated under pumping by a pulse-periodic barrier discharge. Stable excilamp operation was demonstrated at a pump pulse repetition rate of 3 – 9 kHz. The component composition of the working system was determined, which provides a maximal average and pulsed specific radiation power of 48.8 mW cm{sup -3} and 40.6 W cm{sup -3}, respectively, at the efficiency of 7.3 % in the blue-green spectral range with the maximal radiation intensity at the wavelength of 502 nm. The reduction in the radiation power after 2.5 × 10{sup 6} shots is 5 %. Interpretation is given for the results of optimisation of excilamp characteristics. (optical radiation sources)

  1. Advances in HgCdTe APDs and LADAR Receivers

    NASA Technical Reports Server (NTRS)

    Bailey, Steven; McKeag, William; Wang, Jinxue; Jack, Michael; Amzajerdian, Farzin

    2010-01-01

    Raytheon is developing NIR sensor chip assemblies (SCAs) for scanning and staring 3D LADAR systems. High sensitivity is obtained by integrating high performance detectors with gain i.e. APDs with very low noise Readout Integrated Circuits. Unique aspects of these designs include: independent acquisition (non-gated) of pulse returns, multiple pulse returns with both time and intensity reported to enable full 3D reconstruction of the image. Recent breakthrough in device design has resulted in HgCdTe APDs operating at 300K with essentially no excess noise to gains in excess of 100, low NEP <1nW and GHz bandwidths and have demonstrated linear mode photon counting. SCAs utilizing these high performance APDs have been integrated and demonstrated excellent spatial and range resolution enabling detailed 3D imagery both at short range and long ranges. In this presentation we will review progress in high resolution scanning, staring and ultra-high sensitivity photon counting LADAR sensors.

  2. Can graphene make better HgCdTe infrared detectors?

    PubMed Central

    2011-01-01

    We develop a simple and low-cost technique based on chemical vapor deposition from which large-size graphene films with 5-10 graphene layers can be produced reliably and the graphene films can be transferred easily onto HgCdTe (MCT) thin wafers at room temperature. The proposed technique does not cause any thermal and mechanical damages to the MCT wafers. It is found that the averaged light transmittance of the graphene film on MCT thin wafer is about 80% in the mid-infrared bandwidth at room temperature and 77 K. Moreover, we find that the electrical conductance of the graphene film on the MCT substrate is about 25 times larger than that of the MCT substrate at room temperature and 77 K. These experimental findings suggest that, from a physics point of view, graphene can be utilized as transparent electrodes as a replacement for metal electrodes while producing better and cheaper MCT infrared detectors. PMID:21711816

  3. Properties of insulator interfaces with p-HgCdTe

    NASA Technical Reports Server (NTRS)

    Schacham, Samuel E.; Finkman, Eliezer

    1990-01-01

    Heat treatment at 70 C of low carrier concentration p-type HgCdTe samples (p sub o = 8 x 10 exp 14/cm) generates an inverted surface layer. A two day anneal process below 95 C did not affect the Hall coefficient, whereas an almost complete recovery was obtained by annealing at 120 C. While bulk electron mobility, obtained from PEM data, remained high (about 9 x 10 exp 4 sq cm/V s at 77 K), surface mobility is lower by more than an order of magnitude. Surface recombination velocity indicates a continuous improvement with increased temperature, and the activation energy remains equal to the vacancies energy level. The proposed mechanism is that of positive changes in the sulfide migrating towards the interface and generating an image inversion layer.

  4. [HG-AFS determination of selenium in Moringa oleifera].

    PubMed

    Huang, Guo-qing; Xiao, Zi-jun

    2007-02-01

    The Se content in Moringa oleifera was studied by hydride generation atom fluorescence spectrometry (HG-AFS) with wet digestion. The effects of the way of digestion, the work condition of apparatus, the reaction medium and acidity, and the reducing agent and masking agent on the determination of Se were investigated. And the operating condition of apparatus was optimized. The results showed that the detection limit of Se in this method was 0.42 ng x mL(-1) in the linear ranger of 0-120 ng x mL(-1), the relative standard deviation was 3.53% (n = 11), and the recovery of the method was 95.2%-104.6%. It was showed that the method was very sensitive, simple, rapid and accurate.

  5. Processes prevent detrimental effects from As and Hg in feedstocks

    SciTech Connect

    Sarrazin, P.; Cameron, C.J.; Barthel, Y. , 92 - Rueil-Malmaison ); Morrison, M.E. )

    1993-01-25

    The wide range of mercury and arsenic species sometimes present in raw condensates or crude oils can cause major problems such as corrosion and reduced catalyst life. This paper reports on simple, low-investment, feedstock treatment procedures which have been developed that eliminate both As and Hg impurities with very high efficiencies. During the past 20 years, refiners and petrochemical producers have experienced a serious increase in catalyst poisoning caused by mercury and arsenic. This phenomenon may be partically explained by the diversification of the feedstock supply resulting from the need to optimize the profitability of refining and petrochemical operations. The utilization of a more diverse feedstock supply containing metal impurities has led to operating problems such as corrosion of aluminum alloys in steam cracker cold boxes.

  6. High-Operating-Temperature HgCdTe Avalanche Photodiodes

    NASA Astrophysics Data System (ADS)

    Rothman, J.; Baier, N.; Ballet, P.; Mollard, L.; Fournier, M.; Gout, J. S.; Chamonal, J.-P.

    2009-08-01

    In this communication we report the first results of electro-optical characterization of planar heterostructure HgCdTe avalanche photodiodes (APDs), which enables the operation of APDs at high gain, at low bias, and with low dark current and/or at high operating temperature (HOT). The APD is based on a heterostructure in which the photons are detected in a wide-band-gap layer, and the photoelectrons are amplified in a vertical junction in a confined narrow-gap layer. The dark diffusion current and thermal background sensitivity of the device are limited by using a thin narrow-band-gap amplification layer. In addition, the defect-limited dark current is also expected to be reduced due to the reduced volume of the narrow-band-gap depletion layer. The electro-optical performance was characterized at T = 80 K and T = 200 K for two devices with a nominal thickness of the amplification layer of w = 100 nm and 500 nm, realized in x Cd = 0.3 Hg-vacancy-doped layers grown by molecular-beam epitaxy (MBE). The measurements show an average gain of < M< = 10 at a reverse bias of 5 V, which is slightly reduced compared with a conventional APD with x Cd = 0.3. The thermal diffusion current measured at low reverse bias, V b = 0.1 V, and at T = 200 K is about 0.1 mA/cm2 to 0.3 mA/cm2, which is a factor of 50 lower than standard x Cd = 0.3 n-on- p APDs. The quantum efficiency due to absorption in the gain layer is high (QEpeak > 30%), although no antireflecting coating was used, indicating that the device can also be used for high-operating-temperature thermal detection.

  7. Viscosity Relaxation in Molten HgZnTe

    NASA Technical Reports Server (NTRS)

    Su, Ching-Hua; Lehoczky, S. L.; Kim, Yeong Woo; Baird, James K.; Whitaker, Ann F. (Technical Monitor)

    2001-01-01

    Rotating cup measurements of the viscosity of the pseudo-binary melt, HgZnTe have shown that the isothermal liquid with zinc mole fraction 0.16 requires tens of hours of equilibration time before a steady viscous state can be achieved. Over this relaxation period, the viscosity at 790 C increases by a factor of two, while the viscosity at 810 C increases by 40%. Noting that the Group VI elements tend to polymerize when molten, we suggest that the viscosity of the melt is enhanced by the slow formation of Te atom chains. To explain the build-up of linear Te n-mers, we propose a scheme, which contains formation reactions with second order kinetics that increase the molecular weight, and decomposition reactions with first order kinetics that inactivate the chains. The resulting rate equations can be solved for the time dependence of each molecular weight fraction. Using these molecular weight fractions, we calculate the time dependence of the average molecular weight. Using the standard semi-empirical relation between polymer average molecular weight and viscosity, we then calculate the viscosity relaxation curve. By curve fitting, we find that the data imply that the rate constant for n-mer formation is much smaller than the rate constant for n-mer deactivation, suggesting that Te atoms only weakly polymerize in molten HgZnTe. The steady state toward which the melt relaxes occurs as the rate of formation of an n-mer becomes exactly balanced by the sum of the rate for its deactivation and the rate for its polymerization to form an (n+1)-mer.

  8. Methods of isotopic geochronology

    NASA Astrophysics Data System (ADS)

    Gorokhov, I. M.; Levchenkov, O. A.

    Papers are presented on such topics as the age of the chemical elements; the age of meteorites, the moon, and the earth; isotopic ages of the most ancient terrestrial formations; and the Archean evolution of Enderby Land in the Antarctic as evidenced by isotopic dating. Consideration is also given to a uranium-lead geochronology technique for investigating Precambrian ore deposits, a Pb-Pb technique of zircon dating, and the potentials and limitations of Sm-Nd geochronology.

  9. 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.

  10. Mass Fractionation Laws, Mass-Independent Effects, and Isotopic Anomalies

    NASA Astrophysics Data System (ADS)

    Dauphas, Nicolas; Schauble, Edwin A.

    2016-06-01

    Isotopic variations usually follow mass-dependent fractionation, meaning that the relative variations in isotopic ratios scale with the difference in mass of the isotopes involved (e.g., δ17O ≈ 0.5×δ18O). In detail, however, the mass dependence of isotopic variations is not always the same, and different natural processes can define distinct slopes in three-isotope diagrams. These variations are subtle, but improvements in analytical capabilities now allow precise measurement of these effects and make it possible to draw inferences about the natural processes that caused them (e.g., reaction kinetics versus equilibrium isotope exchange). Some elements, in some sample types, do not conform to the regularities of mass-dependent fractionation. Oxygen and sulfur display a rich phenomenology of mass-independent fractionation, documented in the laboratory, in the rock record, and in the modern atmosphere. Oxygen in meteorites shows isotopic variations that follow a slope-one line (δ17O ≈ δ18O) whose origin may be associated with CO photodissociation. Sulfur mass-independent fractionation in ancient sediments provides the tightest constraint on the oxygen partial pressure in the Archean and the timing of Earth's surface oxygenation. Heavier elements also show departures from mass fractionation that can be ascribed to exotic effects associated with chemical reactions such as magnetic effects (e.g., Hg) or the nuclear field shift effect (e.g., U or Tl). Some isotopic variations in meteorites and their constituents cannot be related to the terrestrial composition by any known process, including radiogenic, nucleogenic, and cosmogenic effects. Those variations have a nucleosynthetic origin, reflecting the fact that the products of stellar nucleosynthesis were not fully homogenized when the Solar System formed. Those anomalies are found at all scales, from nanometer-sized presolar grains to bulk terrestrial planets. They can be used to learn about stellar

  11. Admittance Investigation of MIS Structures with HgTe-Based Single Quantum Wells

    NASA Astrophysics Data System (ADS)

    Izhnin, Ihor I.; Nesmelov, Sergey N.; Dzyadukh, Stanislav M.; Voitsekhovskii, Alexander V.; Gorn, Dmitry I.; Dvoretsky, Sergey A.; Mikhailov, Nikolaj N.

    2016-02-01

    This work presents results of the investigation of admittance of metal-insulator-semiconductor structure based on Hg1 - x Cd x Te grown by molecular beam epitaxy. The structure contains a single quantum well Hg0.35Cd0.65Te/HgTe/Hg0.35Cd0.65Te with thickness of 5.6 nm in the sub-surface layer of the semiconductor. Both the conductance-voltage and capacitance-voltage characteristics show strong oscillations when the metal-insulator-semiconductor (MIS) structure with a single quantum well based on HgTe is biased into the strong inversion mode. Also, oscillations on the voltage dependencies of differential resistance of the space charge region were observed. These oscillations were related to the recharging of quantum levels in HgTe.

  12. Electro-physical characteristics of MIS structures with HgTe- based single quantum wells

    NASA Astrophysics Data System (ADS)

    Dzyadukh, S.; Nesmelov, S.; Voitsekhovskii, A.; Gorn, D.

    2015-12-01

    The paper presents brief research results of the admittance of metal-insulator- semiconductor (MIS) structures based on Hg1-xCdxTe grown by molecular-beam epitaxy (MBE) method including single HgCdTe/HgTe/HgCdTe quantum wells (QW) in the surface layer. The thickness of a quantum well was 5.6 nm, and the composition of barrier layers with the thickness of 35 nm was close to 0.65. Measurements were conducted in the range of temperatures from 8 to 200 K. It is shown that for structure with quantum well based on HgTe capacitance and conductance oscillations in the strong inversion are observed. Also it is assumed these oscillations are related with the recharging of quantum levels in HgTe.

  13. Sediment accumulation and mercury (Hg) flux in Avicennia marina forest of Deep Bay, China

    NASA Astrophysics Data System (ADS)

    Li, Ruili; Chai, Minwei; Guo, Meixian; Qiu, Guo Yu

    2016-08-01

    To investigate the rate of sediment accumulation and mercury (Hg) flux in Avicennia marina forest of Deep Bay, China, sediment cores were analyzed. The results showed that Hg concentrations were much higher at all depths compared to the background level. A high correlation between Hg and total organic carbon (TOC) indicated their similar anthropogenic origin. Sedimentation rate was estimated to be 1.38 cm a-1 by 210Pb geochronology. The increase in the mass sediment accumulation rates was rapid (range: 0.5-0.94 g cm-2 a-1), and the Hg fluxes ranged between 76 and 116 ng cm-2 a-1 during the last three decades. The reduction in both Hg concentrations and flux during the last decade may be due to the adoption of contamination control policies. Our results support the notion that the Hg fluxes determined from the sediment cores reveal the effects of anthropogenic influences from the areas around Deep Bay.

  14. Mercury contamination from historical mining territory at Malachov Hg-deposit (Central Slovakia).

    PubMed

    Dadová, Jana; Andráš, Peter; Kupka, Jiří; Krnáč, Jozef; Andráš, Peter; Hroncová, Emília; Midula, Pavol

    2016-02-01

    Environmental contamination caused by mercury is a serious problem worldwide. The study was conducted in order to identify Hg contamination in soil, technosoil from dumps, groundwater, and surface water in the surroundings of the abandoned Hg deposit of Malachov in Central Slovakia. Soil from the Malachovský brook valley was classified as cambi-soil (rendzina). The highest Hg concentrations (44.24 mg kg(-1)) were described in the soil from the mining area at the Vel'ká Studňa locality. In the groundwater, the maximal Hg content is 0.84 μg L(-1), and in the surface water it is 394 μg L(-1). The speciation study proved that in most samples, Hg occurs in the form of cinnabarite. The release of Hg into the environment as a consequence of weathering is limited.

  15. New concepts for HgI2 scintillator gamma ray spectroscopy

    NASA Technical Reports Server (NTRS)

    Iwanczyk, Jan S.

    1994-01-01

    The primary goals of this project are development of the technology for HgI2 photodetectors (PD's), development of a HgI2/scintillator gamma detector, development of electronics, and development of a prototype gamma spectrometer. Work on the HgI2 PD's involved HgI2 purification and crystal growth, detector surface and electrical contact studies, PD structure optimization, encapsulation and packaging, and testing. Work on the HgI2/scintillator gamma detector involved a study of the optical - mechanical coupling for the optimization of CsI(Tl)/HgI2 gamma ray detectors and determination of the relationship between resolution versus scintillator type and size. The development of the electronics focused on low noise amplification circuits using different preamp input FET's and the use of a coincidence technique to maximize the signal, minimize the noise contribution in the gamma spectra, and improve the overall system resolution.

  16. Biogeochemistry Science and Education Part One: Using Non-Traditional Stable Isotopes as Environmental Tracers Part Two: Identifying and Measuring Undergraduate Misconceptions in Biogeochemistry

    NASA Astrophysics Data System (ADS)

    Mead, Chris

    This dissertation is presented in two sections. First, I explore two methods of using stable isotope analysis to trace environmental and biogeochemical processes. Second, I present two related studies investigating student understanding of the biogeochemical concepts that underlie part one. Fe and Hg are each biogeochemically important elements in their own way. Fe is a critical nutrient for phytoplankton, while Hg is detrimental to nearly all forms of life. Fe is often a limiting factor in marine phytoplankton growth. The largest source, by mass, of Fe to the open ocean is windblown mineral dust, but other more soluble sources are more bioavailable. To look for evidence of these non-soil dust sources of Fe to the open ocean, I measured the isotopic composition of aerosol samples collected on Bermuda. I found clear evidence in the fine size fraction of a non-soil dust Fe source, which I conclude is most likely from biomass burning. Widespread adoption of compact fluorescent lamps (CFL) has increased their importance as a source of environmental Hg. Isotope analysis would be a useful tool in quantifying this impact if the isotopic composition of Hg from CFL were known. My measurements show that CFL-Hg is isotopically fractionated, in a unique pattern, during normal operation. This fractionation is large and has a distinctive, mass-independent signature, such that CFL Hg can be uniquely identified from other sources. Misconceptions research in geology has been a very active area of research, but student thinking regarding the related field of biogeochemistry has not yet been studied in detail. From interviews with 40 undergraduates, I identified over 150 specific misconceptions. I also designed a multiple-choice survey (concept inventory) to measure understanding of these same biogeochemistry concepts. I present statistical evidence, based on the Rasch model, for the reliability and validity of this instrument. This instrument will allow teachers and researchers to

  17. The isotopic distribution conundrum.

    PubMed

    Valkenborg, Dirk; Mertens, Inge; Lemière, Filip; Witters, Erwin; Burzykowski, Tomasz

    2012-01-01

    Although access to high-resolution mass spectrometry (MS), especially in the field of biomolecular MS, is becoming readily available due to recent advances in MS technology, the accompanied information on isotopic distribution in high-resolution spectra is not used at its full potential, mainly because of lack of knowledge and/or awareness. In this review, we give an insight into the practical problems related to calculating the isotopic distribution for large biomolecules, and present an overview of methods for the calculation of the isotopic distribution. We discuss the key events that triggered the development of various algorithms and explain the rationale of how and why the various isotopic-distribution calculations were performed. The review is focused around the developmental stages as briefly outlined below, starting with the first observation of an isotopic distribution. The observations of Beynon in the field of organic MS that chlorine appeared in a mass spectrum as two variants with odds 3:1 lie at the basis of the first wave of algorithms for the calculation of the isotopic distribution, based on the atomic composition of a molecule. From here on, we explain why more complex biomolecules such as peptides exhibit a highly complex isotope pattern when assayed by MS, and we discuss how combinatorial difficulties complicate the calculation of the isotopic distribution on computers. For this purpose, we highlight three methods, which were introduced in the 1980s. These are the stepwise procedure introduced by Kubinyi, the polynomial expansion from Brownawell and Fillippo, and the multinomial expansion from Yergey. The next development was instigated by Rockwood, who suggested to decompose the isotopic distribution in terms of their nucleon count instead of the exact mass. In this respect, we could claim that the term "aggregated" isotopic distribution is more appropriate. Due to the simplification of the isotopic distribution to its aggregated counterpart

  18. Lattice defects in semiconducting Hg/1-x/Cd/x/Te alloys. III - Defect structure of undoped Hg0.6Cd0.4Te

    NASA Technical Reports Server (NTRS)

    Vydyanath, H. R.; Donovan, J. D.; Nelson, D. A.

    1981-01-01

    Hall effect measurements were carried out on undoped Hg0.6Cd0.4Te crystals quenched to room temperature subsequent to equilibration at temperatures varying from 450 to 720 C under various partial pressures of Hg. The variation of the hole concentration as a function of the partial pressure of Hg indicates that the native acceptor defects are doubly ionized. Native donor defects are found to be negligible in concentration and the p-type to n-type conversion is shown to be due to residual donors and not due to native donor defects. Thermodynamic constant for the incorporation of the doubly ionized native acceptor defect has been established.

  19. Activation of Homolytic Si-Zn and Si-Hg Bond Cleavage, Mediated by a Pt(0) Complex, via Novel Pt-Zn and Pt-Hg Compounds.

    PubMed

    Kratish, Yosi; Molev, Gregory; Kostenko, Arseni; Sheberla, Dennis; Tumanskii, Boris; Botoshansky, Mark; Shimada, Shigeru; Bravo-Zhivotovskii, Dmitry; Apeloig, Yitzhak

    2015-09-28

    The thermally stable [(tBuMe2 Si)2 M] (M=Zn, Hg) generate R3 Si(.) radicals in the presence of [(dmpe)Pt(PEt3 )2 ] at 60-80 °C. The reaction proceeds via hexacoordinate Pt complexes, (M=Zn (2 a and 2 b), M=Hg (3 a and 3 b)) which were isolated and characterized. Mild warming or photolysis of 2 or 3 lead to homolytic dissociation of the Pt-MSiR3 bond generating silyl radicals and novel unstable pentacoordinate platinum paramagnetic complexes (M=Zn (5), Hg (6)) whose structures were determined by EPR spectroscopy and DFT calculations. PMID:26288342

  20. Investigation of vaporization and condensation processes of thin layers of CdHgTe from laser erosion plasma in Hg atmosphere

    NASA Astrophysics Data System (ADS)

    Kotlyarchuk, B. K.; Popovych, D. I.; Savchuk, V. K.; Savitsky, V. G.

    1996-04-01

    The article sets out to investigate spatial-time and spectral characteristics of laser erosive vapour-plasma torch (EVT), formed at the time of vaporization of mercury chalcogenides targets. Its influence on the synthesis processes and electrophysical properties of HgTe and CdHgTe layers, condensed in mercury vapour, is described. It is shown, that the laser radiation flux density and Hg vapour pressure in the reaction chamber are dominating factors, which determine the character of gas-dynamic spread, EVT composition and electrophysical characteristics of condensed mercury chalcogenides layers.

  1. Activation of Homolytic Si-Zn and Si-Hg Bond Cleavage, Mediated by a Pt(0) Complex, via Novel Pt-Zn and Pt-Hg Compounds.

    PubMed

    Kratish, Yosi; Molev, Gregory; Kostenko, Arseni; Sheberla, Dennis; Tumanskii, Boris; Botoshansky, Mark; Shimada, Shigeru; Bravo-Zhivotovskii, Dmitry; Apeloig, Yitzhak

    2015-09-28

    The thermally stable [(tBuMe2 Si)2 M] (M=Zn, Hg) generate R3 Si(.) radicals in the presence of [(dmpe)Pt(PEt3 )2 ] at 60-80 °C. The reaction proceeds via hexacoordinate Pt complexes, (M=Zn (2 a and 2 b), M=Hg (3 a and 3 b)) which were isolated and characterized. Mild warming or photolysis of 2 or 3 lead to homolytic dissociation of the Pt-MSiR3 bond generating silyl radicals and novel unstable pentacoordinate platinum paramagnetic complexes (M=Zn (5), Hg (6)) whose structures were determined by EPR spectroscopy and DFT calculations.

  2. Persisting impact of historical mining activity to metal (Pb, Zn, Cd, Tl, Hg) and metalloid (As, Sb) enrichment in sediments of the Gardon River, Southern France.

    PubMed

    Resongles, Eléonore; Casiot, Corinne; Freydier, Rémi; Dezileau, Laurent; Viers, Jérôme; Elbaz-Poulichet, Françoise

    2014-05-15

    In this study, we assessed past and present influence of ancient mining activity on metal(loid) enrichment in sediments of a former mining watershed (Gardon River, SE France), that is now industrialized and urbanized. A sedimentary archive and current sediments were characterized combining geochemical analyses, zinc isotopic analyses and sequential extractions. The archive was used to establish local geochemical background and recorded (i) increasing enrichment factors (EFs) for Pb, Zn, Cd, Tl, Hg, As and Sb throughout the industrial era, (ii) a contamination peak in 1976 attributed to a tailings dam failure, and (iii) current levels in 2002 and 2011 similar to those of 1969, except for Sb and Hg, reflecting a persisting contamination pattern. Inter-element relationships and spatial distribution of EF values of current sediments throughout the watershed suggested that both ancient and current contamination had a common origin for Pb, Zn, Cd, Tl and As related to the exploitation of Pb/Zn mineralization while old Sb mines and coal extraction area were the main sources for Sb and Hg respectively. This prevailing mining origin was reflected for Zn by a relatively uniform isotopic composition at δ(66)Zn=0.23 ± 0.03‰, although slight decrease from 0.23‰ to 0.18‰ was recorded from upstream to downstream sites along the river course in relation with the contribution of the lighter δ(66)Zn signature (~0.08‰) of acid mine drainage impacted tributaries. Results from sequential extractions revealed that the potential mobility of the studied metal(loid)s varied in the order Sb

  3. Fission Modes of Mercury Isotopes

    SciTech Connect

    Warda, M.; Staszczak, A.; Nazarewicz, Witold

    2012-01-01

    Background: Recent experiments on -delayed fission in the mercury-lead region and the discovery of asymmetric fission in 180Hg [A. N. Andreyev et al., Phys. Rev. Lett. 105, 252502 (2010)] have stimulated theoretical interest in the mechanism of fission in heavy nuclei.

    Purpose: We study fission modes and fusion valleys in 180Hg and 198Hg to reveal the role of shell effects in the prescission region and explain the experimentally observed fragment mass asymmetry and its variation with A.

    Methods: We use the self-consistent nuclear density functional theory employing Skyrme and Gogny energy density functionals.

    Results: The potential energy surfaces in multidimensional space of collective coordinates, including elongation, triaxiality, reflection-asymmetry, and necking, are calculated for 180Hg and 198Hg. The asymmetric fission valleys well separated from fusion valleys associated with nearly spherical fragments are found in both cases. The density distributions at scission configurations are studied and related to the experimentally observed mass splits.

    Conclusions: The energy density functionals SkM and D1S give a very consistent description of the fission process in 180Hg and 198Hg. We predict a transition from asymmetric fission in 180Hg toward a more symmetric distribution of fission fragments in 198Hg. For 180Hg, both models yield 100Ru/80Kr as the most probable split. For 198Hg, the most likely split is 108Ru/90Kr in HFB-D1S and 110Ru/88Kr in HFB-SkM .

  4. 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

  5. Some health physics aspects of working with 203Hg in university research.

    PubMed

    Belanger, M; Westin, A; Barfuss, D W

    2001-02-01

    The radioisotope 203Hg is used in university toxicology research experiments. When our commercial vendor ceased the production of the high specific activity 203Hg we required, an alternative source was sought. Other commercial sources were investigated without success leaving the synthesis of this radioisotope to us. This paper outlines the method we used to synthesize 203Hg and provides a summary of our results to date and a discussion of our experiences.

  6. Anthropogenic Hg in the ocean: Trajectories of change and implications for exposure in the United States

    NASA Astrophysics Data System (ADS)

    Amos, H. M.; Corbitt, E. S.; Bullard, K. T.; Sunderland, E. M.

    2014-12-01

    Humans have been releasing mercury (Hg) to the environment for millenia through activities such as mining and fuel combustion. The result has been an enrichment of the ocean, atmosphere, and terrestrial ecosystems. Consumption of marine fish contaminated with methylmercury (MeHg) is the primary route of exposure in many populations globally. We present an updated analysis of sources of MeHg exposures in the United States that shows the majority (>70%) is from oceanic fish rather than coastal species. Using a fully coupled biogeochemical box model we also estimate Hg accumulation across major ocean basins and show anthropogenic enrichment is highest in the North Atlantic Ocean and lowest in the deep Pacific Ocean. Our results for contemporary ocean concentrations are consistent with recent data from the Pacific, Atlantic, Indian and Southern Oceans measured as part of the CLIVAR repeat hydrography program. Our estimates of natural (i.e., pre-anthropogenic) seawater Hg concentrations are lower than suggested by other studies, implying a greater anthropogenic perturbation in the ocean. Our work suggests total accumulation of anthropogenic Hg in the global oceans is greater than recently derived based on anthropogenic CO2. We compare modeled seawater concentrations since 1980 to observations over this period to evaluate evidence for changes in recent decades and then investigate potential impacts of changing global emissions. To do this, we use a range of historical and future anthropogenic Hg emission inventories. Our previous work using the box model indicates burial of Hg at ocean margins is the single largest global sink of anthropogenic Hg. We will discuss how the magnitude and permanence of this sink affects estimates of enrichment and time scales of recovery in all geochemical Hg reservoirs. Governing time scales of response in each ocean basin are diagnosed using eigenanalysis and discussed in the context of changes in human MeHg exposure resulting from

  7. Landscape controls on total and methyl Hg in the upper Hudson