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284 results on '"Boutron, C."'

9. One-to-one coupling of glacial climate variability in Greenland and Antarctica

Author

Barbante, C., Barnola, J.-M., Becagli, S., Beer, J., Bigler, M., Boutron, C., Blunier, T., Castellano, E., Cattani, O., Chappellaz, J., Dahl-Jensen, D., Debret, M., Delmonte, B., Dick, D., Falourd, S., Faria, S., Federer, U., Fischer, H., Freitag, J., Frenzel, A., Fritzsche, D., Fundel, F., Gabrielli, P., Gaspari, V., Gersonde, R., Graf, W., Grigoriev, D., Hamann, I., Hansson, M., Hoffmann, G., Hutterli, M. A., Huybrechts, P., Isaksson, E., Johnsen, S., Jouzel, J., Kaczmarska, M., Karlin, T., Kaufmann, P., Kipfstuhl, S., Kohno, M., Lambert, F., Lambrecht, Anja, Lambrecht, Astrid, Landais, A., Lawer, G., Leuenberger, M., Littot, G., Loulergue, L., Luthi, D., Maggi, V., Marino, F., Masson-Delmotte, V., Meyer, H., Miller, H., Mulvaney, R., Narcisi, B., Oerlemans, J., Oerter, H., Parrenin, F., Petit, J.-R., Raisbeck, G., Raynaud, D., Rothlisberger, R., Ruth, U., Rybak, O., Severi, M., Schmitt, J., Schwander, J., Siegenthaler, U., Siggaard-Andersen, M.-L., Spahni, R., Steffensen, J. P., Stenni, B., Stocker, T. F., Tison, J.-L., Traversi, R., Udisti, R., Valero-Delgado, F., van den Broeke, M. R., van de Wal, R. S. W., Wagenbach, D., Wegner, A., Weiler, K., Wilhelms, F., Winther, J.-G., and Wolff, E.

Abstract

Author(s): EPICA Community Members; EPICA Community Members; C. Barbante [1, 2]; J.-M. Barnola [3]; S. Becagli [4]; J. Beer [5]; M. Bigler [6, 7]; C. Boutron [3]; T. Blunier [6]; [...]

Published
2006
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10. Southern Ocean sea-ice extent, productivity and iron flux over the past eight glacial cycles

Author

Wolff, E. W., Fischer, H., Fundel, F., Ruth, U., Twarloh, B., Littot, G. C., Mulvaney, R., Rothlisberger, R., de Angelis, M., Boutron, C. F., Hansson, M., Jonsell, U., Hutterli, M. A., Lambert, F., Kaufmann, P., Stauffer, B., Stocker, T. F., Steffensen, J. P., Bigler, M., Siggaard-Andersen, M. L., Udisti, R., Becagli, S., Castellano, E., Severi, M., Wagenbach, D., Barbante, C., Gabrielli, P., and Gaspari, V.

Subjects
Environmental issues, Science and technology, Zoology and wildlife conservation
Abstract

Author(s): E. W. Wolff (corresponding author) [1]; H. Fischer [2]; F. Fundel [2]; U. Ruth [2]; B. Twarloh [2]; G. C. Littot [1]; R. Mulvaney [1]; R. Rothlisberger [1]; M. [...]

Published
2006
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14. Historical reconstruction of Plutonium contamination in the Swiss-Italian Alps

Author

Gabrieli J., Cozzi G., Vallelonga P., Schwikowski M., Sigl M., Boutron C., and Barbante C.

Subjects
Plutonium, Alps, ice, snow, ICP-SFMS, nuclear tests, Environmental sciences, GE1-350
Abstract

Plutonium is present in the environment as a consequence of atmospheric nuclear tests carried out in the 1960s, nuclear weapons production and releases by the nuclear industry over the past 50 years. Approximately 6 tons of 239Pu have been released into the environment as a result of 541 atmospheric weapon tests Nuclear Pu fallout has been studied in various environmental archives, such as sediments, soil and herbarium grass. Mid-latitude ice cores have been studied as well, on Mont Blanc, the Western Alps and on Belukha Glacier, Siberian Altai. We present a Pu record obtained by analyzing 52 discrete samples of an alpine firn/ice core from Colle Gnifetti (M. Rosa, 4450 m a.s.l.), dating from 1945 to 1991. The 239Pu signal was recorded directly, without preliminary cleaning or preconcentration steps, using an high resolution inductively plasma mass spectrometer equipped with a desolvation system. The 239Pu profile reflects the three main periods of atmospheric nuclear weapons testing: the earliest peak lasted from 1954/55 to 1958 and was caused by the first testing period reaching a maximum in 1958. Despite a temporary halt of testing in 1959/60, the Pu concentration decreased only by half with respect to the 1958 peak due to long atmospheric residence times. In 1961/62 Pu concentrations rapidly increased reaching a maximum in 1963. After the signing of the “Limited Test Ban Treaty” between USA and USSR in 1964, Pu deposition decreased very sharply reaching a minimum in 1967. The third period (1967-1975) is characterized by irregular Pu concentrations with smaller peaks which might be related to the deposition of Saharan dust contaminated by the French nuclear tests of the 1960s.

Published
2013
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15. Trace elements and Pb isotope records in Dome C (East Antarctica) ice over the past 800,000 years

Author

Hong S., Han C. H., Hwang H. J., Soyol-Erdene T-O., Kang J. H., Hur S. D., Burn-Nunes L. J., Gabrielli P., Barbante C., and Boutron C. F.

Subjects
Trace elements, Pb isotopes, Antarctic ice, Climate change, Mid-Brunhes Event, Environmental sciences, GE1-350
Abstract

Trace elements (V, Cr, Mn, Fe, Co, Cu, Zn, As, Rb, Sr, Mo, Cd, Sb, Ba, Tl, Pb, Bi, Th and U) and Pb isotopic compositions from the EPICA (European Project for Ice Coring in Antarctica) Dome C ice core have been determined using inductively coupled plasma sector field mass spectrometry (ICP-SFMS) and thermal ionization mass spectrometry (TIMS), covering the period from ~533 kyr BP to ~800 kyr BP, respectively. Our data have enabled us to extend the previous EDC records of trace elements and Pb isotopes from the Holocene back to the Marine Isotopic Stage 20.2, ~800 kyr BP. We here discuss the EDC records of Ba, Rb, Mo, Sb, Cd, Tl, Bi and Pb isotopes. Crustal elements such as Ba and Rb show well defined variations in concentrations in relation to climatic conditions with lower values during the interglacial periods and much higher values during the coldest periods of the last eight climatic cycles. Volcanogenic Cd, Tl and Bi show a less pronounced relationship between concentrations and climatic conditions. The isotopic signatures of Pb suggest that changes in the provenance of dust reaching the East Antarctic Plateau from Potential Source Areas occurred during the interglacial periods before the MBE. Our data suggest that the main factors affecting deposition fluxes and sources of natural trace elements over Antarctica are most likely linked to a progressive coupling of the climates of Antarctica and lower latitudes over the past 800 kyr.

Published
2013
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20. Trace and Ultra-trace Elements in the Deepest Part of the Vostok Ice Core, Antarctica: Geochemical Characterization of the Sub-glacial Lake Environment

Author

Turetta C., Planchon F., Gabrielli P., Cozzi G., Cairns W., Barbaro E., Petit J.R., Bulat S., Boutron C., and Barbante C.

Subjects
Lake Vostok, trace elements, Antarctica
Abstract

We present in this study comprehensive data on the occurrence of 25 trace and ultra-trace elements in the deepest part of the Vostok ice core. The determination of Li, Na, Mg, Al, K, Ca, V, Cr, Mn, Fe, Co, Cu, Zn, As, Se, Rb, Sr, Mo, Ag, Cd, Sb, Ba, Pb, Bi and U has been performed in the different types of ice encountered from 3271 m to 3609 m of depth, corresponding to atmospheric ice, glacial flour and to accreted ice originating from the freezing of Lake Vostok waters. From atmospheric ice and glacial flour, the relative contributions of primary aerosols were evaluated for each element using a chemical mass balance approach in order to provide a first order evaluation of their partition between soluble (sea-salt) and insoluble (wind-blown dust) fractions in the ice. Sea-salt spray aerosols are the main source of impurities to the ice for certain elements (Na, Mg and K levels, and in a lesser extent to Ca, Sr, Rb, Li and U) while for other elements (Al, V, Cr, Mn, Fe, Co, Cu, Zn, Mo, Sb, Ba and Pb as well as the non sea salt fractions of Mg, K, Ca, Sr, Rb, Li and U) dust inputs appear to primarily control their depositional variability. For the glacial flour, the comparable levels of elements with the overlying atmospheric ice suggest that incorporation of abrasion debris at the glacier is quite limited in the sections considered. For the accreted ice originating from the subglacial waters of Lake Vostok, we observed a major chemical shift in the composition of the ice showing two distinct trends that we assumed to be derived from the chemical speciation of elements. The study of the glacier ice and the glacial flour has allowed us to perform a detailed characterisation of elemental abundances related to the aerosol sources variability and also to illustrate the interaction between the ice-sheet and the bedrock.

Published
2016

22. Distribution of Ca, Fe, K, and S between soluble and insoluble material in the Greenland Ice Core Project ice core

Author

Laj, P, Ghermandi, G, Cecchi, R, Maggi, V, Riontino, C, Hong, S, Candelone, J, Boutron, C, MAGGI, VALTER, Boutron, C., Laj, P, Ghermandi, G, Cecchi, R, Maggi, V, Riontino, C, Hong, S, Candelone, J, Boutron, C, MAGGI, VALTER, and Boutron, C.

Abstract

We have developed an original method coupling particle induced X ray emission and scanning electron microscope/X ray dispersive analysis in order to characterize the partitioning of Fe, Ca, K, and S between the soluble and the insoluble phases in wind-blown deposits in the Greenland ice. We applied this technique to several sections of the Greenland Ice Core Project ice core. We found that the dominant fraction (from 25 to 100%) of Ca and S deposited in Greenland is soluble, while the proportion of soluble material is lower for K and Fe (between 10 and 80%). For all elements the distribution between soluble and insoluble material varies according to the ice-core depth. The distribution appears to be linked to either meteorological factors, such as temperature or pH of the precipitation (in the case of Ca or S), or the alterability of the mineral assemblages found in the ice (in the case of Fe and K). The fraction of soluble material is therefore linked to the characteristics of source origin (S is predominantly emitted in very soluble forms) and to the dissolution of certain minerals (such as calcium carbonate or Fe-oxides) during transport in the atmosphere. The dynamics of alteration processes is, however, still uncertain, especially for K-containing minerals

Published
1997

23. Observations, data accuracy and tools

Author

Arbetter T, Arthern R, Barbante C, Bargagli R, Bergstrom D, Bertler N, Bindschadler R, Bockheim J, Boutron C, Bromwich D, Chown S, Clarke A, Comiso J, Convey P, Cook A, di Prisco G, Fahrbach E, Fastook J, Fleming A, Gugliemin M, Gutt J, Hellmer H, and Hennion

Published
2009

26. The instrumental period

Author

Adams B, Arthern R, Atkinson A, Barbante C, Bargagli R, Bergstrom D, Bertler N, Bindschadler R, Bockheim J, Boutron C, Bromwich D, Chown S, Comiso J, Convey P, Cook A, di Prisco G, Fahrbach E, Fastook J, Forcarda J, Gili J-M, Gugliemin M, Gutt J, and Hellmer

Published
2009

27. Atmospheric depletion of mercury over Antarctica during glacial periods

Author

Jitaru, P, Gabrielli, P, Marteel, A, C. PLANE J. M., Planchon, F. A. M., Gauchard, P. A., Ferrari, C, Boutron, C. F., Adams, F. C., Hong, S, Cescon, Paolo, and Barbante, Carlo

Subjects
000 YEARS, METHYLATED MERCURY, ICE CORE, SNOW, NATURAL SOURCE, PAST 800, CYCLES, POLAR SUNRISE, SPRINGTIME DEPLETION, EQUATORIAL PACIFIC-OCEAN, TROPOSPHERE
Abstract

Mercury is a globally dispersed toxic metal that affects even remote polar areas. During seasonal atmospheric mercury depletion events in polar areas, mercury is removed from the atmosphere1,2 and subsequently deposited in the surface snows3. However, it is unknown whether these events, which have been documented for the past two decades, have occurred in the past. Here we show that over the past 670,000 years, atmospheric mercury deposition in surface snows was greater during the coldest climatic stages, coincident with the highest atmospheric dust loads. We suggest that this increased scavenging is caused by the low temperatures, which allowed the oxidation of gaseous mercury by sea-salt-derived halogens. The oxidized mercury compounds are then transferred onto the abundant mineral dust grains and deposited on the snowpack, leading to the depletion of gaseous mercury in the Antarctic atmosphere. We conclude that polar regions acted as a mercury sink during the coldest climatic stages, and that atmospheric deposition of Hg is therefore not an exclusively recent phenomenon.

Published
2009

28. Atmospheric mercury depletion event stuy in Ny-Alesund (Svalbard) in spring 2005. Deposition and transformation of Hg in surface snow during springtime

Author

Ferrari CP, Padova C., Fain X, Gauchard PA, Dommergue A., Aspmo K., Berg T., Cairns W., Barbante C., Cescon P., Kaleschke L., Richter A., Wittrock F., and Boutron C.

Subjects
chemical transformation, mercury, snow, human activities, deposition
Abstract

A field campaign was conducted in Ny-Alesund (78 degrees 54'N, 11 degrees 53'E), Svalbard (Norway) during April and May 2005. An Atmospheric Mercury (Hg) Depletion Event (AMDE) was observed from the morning of April 24 until the evening of April 27. Transport of already Hg and ozone (O-3) depleted air masses could explain this observed depletion. Due to a snowfall event during the AMDE, surface snow Hg concentrations increased two fold. Hg deposition took place over a short period of time corresponding to 3-4 days. More than 80% of the deposited Hg was estimated to be reemitted back to the atmosphere in the days following the event. During the campaign, we observed night and day variations in surface snow Hg concentrations, which may be the result of gaseous elemental mercury (GEM) oxidation to divalent Hg at the snow/air interface by daylight surface snow chemistry. Finally, a decrease in the reactive Hg (Hg-R) fraction of total Hg (Hg-T) in the surface snow was observed during spring. We postulate that the transformation of HgR to a more stable form may occur in Arctic snow during spring. (C) 2008 Elsevier B.V. All rights reserved

Published
2008

29. Bacterial characterization of the snow cover at Spitzberg, Svalbard

Author

Amato, Pierre, Hennebelle, R., Magand, O., Sancelme, Martine, Delort, A.M., Barbante, C., Boutron, C., Ferrari, C., Synthèse et étude de systèmes à intêret biologique (SEESIB), Université Blaise Pascal - Clermont-Ferrand 2 (UBP)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de glaciologie et géophysique de l'environnement (LGGE), Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Environmental Sciences Department, University of Ca’ Foscari [Venice, Italy], Polytech' Grenoble, Université Joseph Fourier - Grenoble 1 (UJF), Centre National de la Recherche Scientifique (CNRS)-Université Blaise Pascal - Clermont-Ferrand 2 (UBP), SEESIB, Université Blaise Pascal - Clermont-Ferrand 2 (UBP)-Centre National de la Recherche Scientifique (CNRS)-Université Blaise Pascal - Clermont-Ferrand 2 (UBP)-Centre National de la Recherche Scientifique (CNRS), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS), Université Blaise Pascal - Clermont-Ferrand 2 (UBP)-Centre National de la Recherche Scientifique (CNRS), Université Blaise Pascal - Clermont-Ferrand 2 (UBP)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), and Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])

Subjects
biodegradation, Arctic, cold environment, [SDU.STU.GL]Sciences of the Universe [physics]/Earth Sciences/Glaciology, snow, bacteria, human activities
Abstract

International audience; A sampling campaign was organized during spring 2004 in Spitzberg, Svalbard, in the area around the scientific base of Ny-Ålesund, to characterize the snow pack bacterial population. Total bacteria counts were established by 4',6-diamino-2-phenylindole (DAPI) in the seasonal snow pack bordering the sea. On the sea shore, bacterial concentration was about 6 × 104 cells mL−1, without any significant variation according to depth. In the accumulation snow layer of the glacier, concentrations were about 2 × 104 cells mL−1, except in the 2003 summer layer, where it reached 2 × 105 cells mL−1, as the result of cell multiplication allowed by higher temperature and snow melting. Strains isolated from the seasonal snow pack were identified from their 16S rRNA gene sequences, and lodged in GenBank. They belong to the Alphaproteobacteria, Betaproteobacteria and Gammaproteobacteria, Firmicutes and Actinobacteria. They are closely related to cold environment bacteria, as revealed by phylogenetic tree constructions, and two appear to be of unknown affiliation. Using 1H nuclear magnetic resonance, it was shown that these isolates have the capacity to degrade organic compounds found in Arctic snow (propionate, acetate and formate), and this can allow them to develop when snow melts, and thus to be actively involved in snow chemistry.

Published
2007

40. Halogen species record Antarctic sea ice extent over glacial-interglacial periods

Author

Spolaor, A., Vallelonga, Paul Travis, Plane, JMC, Kehrwald, N., Gabrieli, J., Varin, C., Turetta, C., Cozzi, G., Kumar, R., Boutron, C., Barbante, C., Spolaor, A., Vallelonga, Paul Travis, Plane, JMC, Kehrwald, N., Gabrieli, J., Varin, C., Turetta, C., Cozzi, G., Kumar, R., Boutron, C., and Barbante, C.

Published
2013

43. Heavy metals in ancient and tropical ice: initial results

Author

Ferrari, C. P., Clotteau, T., Thomson, L. G., Barbante, Carlo, Cozzi, G., Cescon, Paolo, Hong, S., MAURICE BOURGOIN, L., Francou, B., and Boutron, C.

Subjects
Bolivia, last glacial maximum, Holocene, tropical ice, heavy metals
Published
2001

46. Determination of Fe2+ and Fe3+ species by FIA-CRC-ICP-MS in Antarctic ice samples

Author

Spolaor, A, Vallelonga, Paul Travis, Gabrieli, J, Cozzi, G, Boutron, C, Barbante, C, Spolaor, A, Vallelonga, Paul Travis, Gabrieli, J, Cozzi, G, Boutron, C, and Barbante, C

Abstract

Iron is an element of great interest due to its role in primary production and in oceanic carbon cycle regulation, such that past changes in iron deposition may have influenced oceanic sequestration of atmospheric CO2 on millennial time scales. The behavior of iron in biological and environmental contexts depends strongly on its oxidation state. Solubility in water and the capacity to form complexes are just two important characteristics that are species dependent. Distinguishing between the two iron species, Fe(II) and Fe(III), is necessary to evaluate bioavailability, as Fe(II) is more soluble and therefore more readily available for phytoplankton uptake and growth. Here, we present a novel analytical method for iron speciation analysis using Collision Reaction Cell-Inductively Coupled Plasma-Mass Spectrometry (CRC-ICP-MS) and apply it to ice core samples from Talos Dome, Antarctica. The method detection limit is 0.01 ng g-1. A chelating resin, Ni-NTA Superflow, was used to separate the Fe species: At pH 2 the resin is capable of retaining Fe3+ with no retention of Fe2+. After the initial separation, we oxidized the Fe2+ using H2O2, and determined the Fe2+ concentration as the difference between the two measurements. Our preliminary results demonstrate higher Fe2+ concentrations during glacial periods than during interglacial periods. This elevated Fe2+ suggests that more iron was available for phytoplankton growth during the Last Glacial Maximum, than would be expected from measurements of proxies such as dust mass or total Fe.

Published
2012

47. Ice Core Record Variations of Atmospheric Cu, Zn, Cd, Pb, and Pb Isotopes During the Past 800 Years in Mount Everest

Author

Hong, S., Lee, K., Do Hur, S., Hou, S., Nunes, Laurie, Boutron, C., Barbante, C., Hong, S., Lee, K., Do Hur, S., Hou, S., Nunes, Laurie, Boutron, C., and Barbante, C.

Abstract

Cu, Zn, Cd, and Pb concentrations and Pb isotopic composition were measured in high-altitude Mount Everest ice cores, spanning an 800-year period from 1205 to 2002 ad in order to evaluate the extent to which human activities have affected the natural atmospheric cycles of these elements in Central Asia. The results show that concentrations of Cu, Zn, Cd, and Pb in the remote Himalayan atmosphere were primarily of natural origin until the mid-20th century. Significant increases in crustal enrichment factors (EFs) in comparison with the average preanthropogenic EF value are observed for the measured metals during the recent decades, with contrasting time trends for the different metals. Such recent enhancements in EFs are attributed to massive anthropogenic emissions of Cu, Zn, and Cd mainly from combustion of fossil fuel and production of nonferrous metals, while increased emissions of Pb are attributed to combustion of fossil fuels as well as leaded gasoline usage in South Asia. Significant variations in the Pb EFs and 206Pb/207Pb isotope ratios starting from the 1970s characterize the unambiguous atmospheric Pb pollution and the time-dependent evolution of industrial Pb inputs as a result of industrial developments in South Asia.

Published
2012

50. Isotopic signatures for natural versus anthropogenic Pb in high-altitude Mt. Everest ice cores during the past 800 years

Author

Lee, K., Hur, S., Hou, S., Nunes, Laurie, Hong, S., Barbante, C., Boutron, C., Rosman, Kevin, Lee, K., Hur, S., Hou, S., Nunes, Laurie, Hong, S., Barbante, C., Boutron, C., and Rosman, Kevin

Abstract

A long-term record, extending back 800 years (1205 to 2002 AD), of the Pb isotopic composition (206Pb/207Pb and 208Pb/207Pb) as well as Pb concentrations from high altitude Mt. Everest ice cores has the potential to identify sources and source regions affecting natural and anthropogenic Pb deposition in central Asia. The results show that the regional natural background Pb isotope signature (~1.20 for 206Pb/207Pb and ~2.50 for 208Pb/207Pb) in the central Himalayas was dominated by mineral dust over the last ~750 years from 1205 to 1960s,mostly originating from local sources with occasional contributions of long-range transported dust probably from Sahara desert and northwestern India. Since the 1970s, the Pb isotope ratios are characterized by a continuous decline toward less radiogenic ratioswith the leastmean ratios of 1.178 for 206Pb/207Pb and 2.471 for 208Pb/207Pb in the period 1990–1996. The depression of the 206Pb/207Pb and 208Pb/207Pb values during the rrespondingperiods ismost likely due to an increasing influence of less radiogenic Pb of anthropogenic originmainly from leaded gasoline used in South Asia (India aswell as possibly Bangladesh and Nepal). From1997 to 2002, isotopic composition tends to show a shift to slightly more radiogenic signature. This is likely attributed to reducing Pb emissions from leaded gasoline in source regions, coinciding with the nationwide reduction of Pb in gasoline and subsequent phase-out of leaded gasoline in South Asia since 1997. An interesting feature is the relatively high levels of Pb concentrations and enrichment factors (EF) between 1997 and 2002. Although the reason for this feature remains uncertain, it would be probably linked with an increasing influence of anthropogenic Pb emitted from other sources such as fossil fuel combustion and non-ferrous metal production.

Published
2011

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