Browsing by Author "Wacker, L"
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- ItemThe ANSTO – University of Wollongong in-situ 14C extraction laboratory(Elsevier, 2019-01-01) Fülöp, RH; Fink, D; Yang, B; Codilean, AY; Smith, AM; Wacker, L; Levchenko, VA; Dunai, TJWe present our first 14C in-situ results for calibration and system blanks from the recently completed Australian Nuclear Science and Technology Organisation (ANSTO) – University of Wollongong (UOW) in-situ 14C extraction system. System performance parameters and quality is evidenced by low 14C blanks and good reproducibility for multiple targets from different reference materials. The 14C extraction scheme exploits the high temperature phase transformation of quartz to cristobalite in order to quantitatively extract the carbon as CO2. The in-situ 14C extraction system comprises three independently operated and modular units that are used for initial in-vacuo removal of meteoric 14C, followed by offline high-temperature heating of quartz to release trapped cosmogenic in-situ 14C, and finally CO2 gas purification and mass measurement. The design allows for rapid sample throughput of about 6 samples per week with samples masses ranging between 0.5 and 4 g of clean quartz. Other features include single-pass catalytic oxidation using mixed copper (I,II) oxide as catalyst, use of UHV-compatible components and of vacuum annealed copper tubing. We present results for sets of purified quartz samples prepared from CRONUS-A, CRONUS-R and CRONUS-N inter-comparison materials, with final averages consistent with published values. Following extraction and cleaning, CO2 gas aliquots for some of the samples were analysed using the ETH Zürich CO2 gas ion source at the ETH MICADAS AMS facility in addition to CO2 being graphitised using the ANSTO laser-heated graphitisation micro-furnace and then analysed on ANSTO’s ANTARES AMS facility. System blanks using either CO2 or graphite ion-sources at both facilities are on the order of ∼1 × 104 atoms. © 2018 Elsevier B.V.
- ItemExploring sediment dynamics from source to sink in the Murray-Darling basin using cosmogenic 14C, 10Be, and 26Al(Australasian Quaternary Association Inc., 2018-12-10) Fülöp, RH; Codilean, AT; Marx, SK; Cohen, TJ; Fink, D; Yang, B; Smith, AM; Wilcken, KM; Fujioka, T; Wacker, L; Dunai, TJThe relatively short half-life of 14C, namely, 5730 years, means that, compared to the other cosmogenic nuclides, it is substantially more sensitive to short term variations in process rates. Both the erosion of steep mountains and the dynamics of sediment transport, storage and recycling occur over timescales that are too short to be detectable by the cosmogenic nuclides that are currently used routinely, namely 10Be and 26Al. In situ 14C on the other hand is ideally suited for these short timescales, and used in combination with 26Al and 10Be, it will allow for rapid fluctuations in process rates and/or the relatively short timescales that characterise sediment transfer and storage to be measured accurately. The above make in situ 14C an important addition to the cosmogenic radionuclide toolkit. We present results of in situ cosmogenic 14C system blank and calibration sample measurements obtained with the recently established ANSTO/UOW in situ 14C extraction system. The 14C extraction scheme follows the design of the University of Cologne, which exploits the phase transformation of quartz to crystobalite to quantitatively extract the carbon as CO2. Offline high-temperature furnace extraction allows a relative rapid sample throughput and can accommodate samples ranging between 0.5 to 4 grams of clean quartz. Following extraction and isolation, the CO2gas is graphitised using a micro-furnace and then measured using AMS similarly to routine small radiocarbon samples. We also present results of 14C, 26Al, and 10Be analyses from sediment samples collected from Australia’s largest river system, the Murray-Darling basin. We use the downstream changes in the ratios of the three radionuclides in samples collected at key locations along the rivers to quantify sediment mixing and sediment storage times in the river basin. Substantial 26Al/10Be ‘burial’ signal is observed in downstream Murray and Darling samples, while in situ 14C suggests complex burial-exposure histories in these samples. This could have implication of interpreting geochemical proxies at the outlet of Murray-Darling Basin for identification of paleoclimate driven sediment sources (i.e. Monsoon vs. Westerlies). © The Authors
- ItemMillion-year lag times in a post-orogenic sediment conveyor(American Association for the Advancement of Science, 2020-06-19) Fülöp, RH; Codilean, AT; Wilcken, KM; Cohen, TJ; Fink, D; Smith, AM; Yang, B; Levchenko, VA; Wacker, L; Marx, SK; Stomsoe, N; Fujioka, T; Dunai, TJUnderstanding how sediment transport and storage will delay, attenuate, and even erase the erosional signal of tectonic and climatic forcings has bearing on our ability to read and interpret the geologic record effectively. Here, we estimate sediment transit times in Australia’s largest river system, the Murray-Darling basin, by measuring downstream changes in cosmogenic 26Al/10Be/14C ratios in modern river sediment. Results show that the sediments have experienced multiple episodes of burial and reexposure, with cumulative lag times exceeding 1 Ma in the downstream reaches of the Murray and Darling rivers. Combined with low sediment supply rates and old sediment blanketing the landscape, we posit that sediment recycling in the Murray-Darling is an important and ongoing process that will substantially delay and alter signals of external environmental forcing transmitted from the sediment’s hinterland. Copyright © 2020 The Authors
- ItemNatural and anthropogenic 236U in environmental samples(Elsevier, 2008-03-06) Steier, P; Bichler, M; Fifield, LK; Golser, R; Kutschera, W; Priller, A; Quinto, F; Richter, S; Srncik, M; Terrasi, P; Wacker, L; Wallner, A; Wilcken, KM; Wild, EMThe interaction of thermal neutrons with 235U results in fission with a probability of ∼85% and in the formation of 236U (t1/2 = 2.3 × 107 yr) with a probability of ∼15%. While anthropogenic 236U is, therefore, present in spent nuclear fuel at levels of 236U/U up to 10−2, the expected natural ratios in the pre-anthropogenic environment range from 10−14 to 10−10. At VERA, systematic investigations suggest a detection limit below 236U/U = 5 × 10−12 for samples of 0.5 mg U, while chemistry blanks of ∼2 × 107 atoms 236U per sample limit the sensitivity for smaller samples. We have found natural isotopic ratios in uranium reagents separated before the onset of human nuclear activities, in uranium ores from various origins and in water from a subsurface well in Bad Gastein, Austria. Anthropogenic contamination was clearly visible in soil and rivulet samples from Salzburg, Austria, whereas river sediments from Garigliano river (Southern Italy) were close to the detection limit. Finally, our natural in-house standard Vienna-KkU was calibrated against a certified reference material (IRMM REIMEP-18 A). © 2008 Elsevier B.V.
- ItemThe new Chronos 14carbon-Cycle Facility, University of New South Wales, Sydney, Australia.(Australian Nuclear Science and Technology Organisation, 2021-11-17) Turney, CSM; Thomas, Z; Becerra-Valdivia, L; Palmer, JG; Haines, HA; Cadd, H; Wacker, L; Baker, AA; Andersen, MS; Jacobsen, GE; Meredith, KT; Chinu, K; Hiscock, W; Vohra, J; Marjo, CEThe Chronos 14Carbon-Cycle Facility is a new radiocarbon laboratory at the University of New South Wales, Australia. Built around an Ionplus 200 kV MIni-CArbon DAting System (MICADAS) Accelerator Mass Spectrometer (AMS) installed in October 2019, the facility was established to address major challenges in the Earth, Environmental and Archaeological sciences. Here we report an overview of the Chronos facility, the pretreatment methods currently employed (bones, carbonates, peat, pollen, charcoal, and wood) and results of radiocarbon and stable isotope measurements undertaken on a wide range of sample types. Our measurements on international standards, known-age and blank samples demonstrate that the facility is capable of measuring 14C samples from the Anthropocene back to nearly 50,000 years ago. Future work will focus on improving our understanding of the Earth system and managing resources in a future warmer world.
- ItemRadiocarbon protocols and first intercomparison results from the Chronos 14Carbon-Cycle Facility, University of New South Wales, Sydney, Australia(Cambridge University Press, 2021-05-11) Turney, CSM; Becerra-Valdivia, L; Sookdeo, A; Thomas, ZA; Palmer, JG; Haines, HA; Cadd, H; Wacker, L; Baker, AA; Andersen, MS; Jacobsen, GE; Meredith, KT; Chinu, K; Bollhalder, S; Marjo, CEThe Chronos 14Carbon-Cycle Facility is a new radiocarbon laboratory at the University of New South Wales, Australia. Built around an Ionplus 200 kV MIni-CArbon DAting System (MICADAS) Accelerator Mass Spectrometer (AMS) installed in October 2019, the facility was established to address major challenges in the Earth, Environmental and Archaeological sciences. Here we report an overview of the Chronos facility, the pretreatment methods currently employed (bones, carbonates, peat, pollen, charcoal, and wood) and results of radiocarbon and stable isotope measurements undertaken on a wide range of sample types. Measurements on international standards, known-age and blank samples demonstrate the facility is capable of measuring 14C samples from the Anthropocene back to nearly 50,000 years ago. Future work will focus on improving our understanding of the Earth system and managing resources in a future warmer world. © The Author(s) 2021. Published by Cambridge University Press for the Arizona Board of Regents on behalf of the University of Arizona.
- ItemSHCal20 Southern Hemisphere calibration, 0–55,000 years cal BP(Cambridge University Press, 2020-08-12) Hogg, AG; Heaton, TJ; Hua, Q; Palmer, JG; Turney, CSM; Southon, J; Bayliss, A; Blackwell, PG; Boswijk, G; Bronk Ramsey, C; Pearson, C; Petchey, F; Reimer, P; Wacker, LEarly researchers of radiocarbon levels in Southern Hemisphere tree rings identified a variable North-South hemispheric offset, necessitating construction of a separate radiocarbon calibration curve for the South. We present here SHCal20, a revised calibration curve from 0–55,000 cal BP, based upon SHCal13 and fortified by the addition of 14 new tree-ring data sets in the 2140–0, 3520–3453, 3608–3590 and 13,140–11,375 cal BP time intervals. We detail the statistical approaches used for curve construction and present recommendations for the use of the Northern Hemisphere curve (IntCal20), the Southern Hemisphere curve (SHCal20) and suggest where application of an equal mixture of the curves might be more appropriate. Using our Bayesian spline with errors-in-variables methodology, and based upon a comparison of Southern Hemisphere tree-ring data compared with contemporaneous Northern Hemisphere data, we estimate the mean Southern Hemisphere offset to be 36 ± 27 14C yrs older. © 2020 by the Arizona Board of Regents on behalf of the University of Arizona. This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted re-use, distribution, and reproduction in any medium, provided the original work is properly cited.