Browsing by Author "Vallelonga, P"

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    Characterizing black carbon in rain and ice cores using coupled tangential flow filtration and transmission electron microscopy
    (European Geosciences Union, 2015-01-01) Ellis, A; Edwards, R; Saunders, M; Chakrabarty, RK; Subramanian, R; van Riessen, A; Smith, AM; Lambrinidis, D; Nunes, LJ; Vallelonga, P; Goodwin, ID; Moy, AD; Curran, MAJ; van Ommen, TD
    Antarctic ice cores have been used to study the history of black carbon (BC), but little is known with regards to the physical and chemical characteristics of these particles in the remote atmosphere. Characterization remains limited by ultra-trace concentrations in ice core samples and the lack of adequate methods to isolate the particles unaltered from the melt water. To investigate the physical and chemical characteristics of these particles, we have developed a tangential flow filtration (TFF) method combined with transmission electron microscopy (TEM). Tests using ultrapure water and polystyrene latex particle standards resulted in excellent blanks and significant particle recovery. This approach has been applied to melt water from Antarctic ice cores as well as tropical rain from Darwin, Australia with successful results: TEM analysis revealed a variety of BC particle morphologies, insoluble coatings, and the attachment of BC to mineral dust particles. The TFF-based concentration of these particles has proven to give excellent results for TEM studies of BC particles in Antarctic ice cores and can be used for future studies of insoluble aerosols in rainwater and ice core samples. © Author(s)
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    Dating Antarctic ice cores using high-temporal resolution black carbon records
    (Antarctic Climate and Ecosystems Cooperative Research Centre, 2016-03-07) Edwards, R; Vallelonga, P; McConnell, JR; Bertler, NAN; Curran, MAJ; Sigil, M; Fudge, TJ; Anschuetz, H; Neff, PD; Emanuelsson, D; Bisiaux, M; Goodwin, D; Smith, AM; Taylor, KC; Moy, AD; Fetieng, W; Ellis, A
    Black carbon aerosols (BC) emitted by fires in the Southern Hemisphere (SH) are transported to Antarctica and preserved in the Antarctic ice sheet. Recent efforts to develop ice core records of BC deposition to Antarctica show variability in BC over a broad range of time scales. The ~ monthly-resolution BC record from the WAIS divide deep ice core displayed strong seasonal variability in modern sections of the record consistent with the timing of SH biomass burning. The record was subsequently used as an annual layer dating proxy in conjunction with other chemical species. If the emissions and transport of BC to Antarctica are stable over long periods of time it may be useful as an annual layer proxy at sites other than WAIS. To date, a rigorous comparison of Antarctic ice core BC seasonality from different locations have not been conducted. Here we present a comparison of BC ice core data from the top sections of the WAIS divide deep core, the Roosevelt Island RICE core, and the Law Dome DSS1213 core. The RICE and Law Dome sites are separated from WAIS by large distances and experience different atmospheric circulation and climate regimes. A detailed description of the data uncertainties and its use in annual layer counting will be discussed.
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    Individual particle morphology, coatings, and impurities of black carbon aerosols in Antarctic ice and tropical rainfall
    (John Wiley & Sons, Inc, 2016-11-04) Ellis, A; Edwards, R; Saunders, M; Chakrabarty, RK; Subramanian, R; Timms, NE; van Riessen, A; Smith, AM; Lambrindis, D; Nunes, LJ; Vallelonga, P; Goodwin, ID; Moy, AD; Curran, MAJ; van Ommen, TD
    Black carbon (BC) aerosols are a large source of climate warming, impact atmospheric chemistry, and are implicated in large-scale changes in atmospheric circulation. Inventories of BC emissions suggest significant changes in the global BC aerosol distribution due to human activity. However, little is known regarding BC's atmospheric distribution or aged particle characteristics before the twentieth century. Here we investigate the prevalence and structural properties of BC particles in Antarctic ice cores from 1759, 1838, and 1930 Common Era (C.E.) using transmission electron microscopy and energy-dispersive X-ray spectroscopy. The study revealed an unexpected diversity in particle morphology, insoluble coatings, and association with metals. In addition to conventionally occurring BC aggregates, we observed single BC monomers, complex aggregates with internally, and externally mixed metal and mineral impurities, tar balls, and organonitrogen coatings. The results of the study show BC particles in the remote Antarctic atmosphere exhibit complexity that is unaccounted for in atmospheric models of BC. ©2016. American Geophysical Union.
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    Measurement of Pb in ancient Antarctic ice: implications for source regions of aerosols and past environmental conditions
    (Elsevier; Cambridge Publications, 2010-06-16) Burn-Nunes, L; Rosman, KJR; Vallelonga, P; Loss, RD; Curran, MAJ; Smith, AM
    The isotopic compositions and concentrations of Pb in ancient Antarctic ice cores has provided invaluable information in the investigation of past global climatic and environmental conditions, providing a useful method of fingerprinting sources of Pb deposited into the Antarctic environment. Whilst these studies have proved useful, they typically cover decadal to millennial time periods and relatively few data are available on annual or seasonal time scales. Such high-resolution studies are critical for the investigation of links between short-term meteorological conditions and the transport of impurities into the Antarctic environment which, in turn, complement the interpretation of the deep ice core records. However, to date, such studies have been unable to identify any regular seasonal variability in Pb concentrations and isotopes. Consequently, an improved ice core lathe technique has been developed that allows ice cores to be to be sampled with low contamination and high spatial resolution; concurrently mass spectrometry techniques have been refined permitting Pb isotopic ratios and concentrations of Pb to be measured with accuracy and precision equivalent to much larger sample amounts. This technique has been applied to the sectioning of selected Law Dome, Eastern Antarctic ice cores dated to ~56 ky, ~16 ky and, the late 18th and 19th centuries, to gain a greater understanding of the deposition of Pb, in coastal Antarctica, on short-term and seasonal scales.
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    An ultra-clean technique for accurately analysing Pb isotopes and heavy metals at high spatial resolution in ice cores with sub-pg g(-1) Pb concentrations
    (Elsevier, 2009-02-23) Burn, LJ; Roseman, KJR; Candelone, JP; Vallelonga, P; Burton, GR; Smith, AM; Morgan, VI; Barbante, C; Hong, S; Boutron, CF
    Measurements of Pb isotope ratios in ice containing sub-pg g(-1) concentrations are easily compromised by contamination, particularly where limited sample is available. Improved techniques are essential if Antarctic ice cores are to be analysed with sufficient spatial resolution to reveal seasonal variations due to climate. This was achieved here by using stainless steel chisels and saws and strict protocols in an ultra-clean cold room to decontaminate and section ice cores. Artificial ice cores, prepared from high purity water were used to develop and refine the procedures and quantify blanks. Ba and In, two other important elements present at pg g-1 and fg g(-1) concentrations in Polar ice, were also measured. The final blank amounted to 0.2 +/- 0.2 pg of Pb with Pb-206/Pb-207 and Pb-208/Pb-207 ratios of 1.16 +/- 0.12 and 2.35 +/- 0.16, respectively, 1.5 +/- 0.4 pg of Ba and 0.6 +/- 2.0 fg of In, most of which probably originates from abrasion of the steel saws by the ice. The procedure was demonstrated on a Holocene Antarctic ice core section and was shown to contribute blanks of only similar to 5%, similar to 14% and similar to 0.8% to monthly resolved samples with respective Pb, Ba and In concentrations of 0.12 pg g(-1), 0.3 pg g(-1) and 2.3 fg g(-1). Uncertainties in the Pb isotopic ratio measurements were degraded by only similar to 0.2%. © 2009, Elsevier Ltd.