• 14C AMS Measurements of <100 Microgram Samples with a High-Current System

      von Reden, K. F.; McNichol, Ann P.; Pearson, Ann; Schneider, Robert J. (Department of Geosciences, The University of Arizona, 1998-01-01)
      The NOSAMS facility at Woods Hole Oceanographic Institution has started to develop and apply techniques for measuring very small samples on a standard Tandetron accelerator mass spectrometry (AMS) system with high-current hemispherical Cs sputter ion sources. Over the past year, results on samples ranging from 7 to 160 micrograms C showed both the feasibility of such analyses and the present limitations on reducing the size of solid carbon samples. One of the main factors affecting the AMS results is the dependence of a number of the beam optics parameters on the extracted ion beam current. The extracted currents range from 0.5 to 10 micro-A of 12Cfor the sample sizes given above. We here discuss the setup of the AMS system and methods for reliable small-sample measurements and give the AMS-related limits to sample size and the measurement uncertainties.
    • 14C Analysis of Annual Tree Rings from the Vicinity of the Chernobyl NPP

      Buzinny, Michael; Likhtarev, Ilja; Los', Ivan; Talerko, Nikolay; Tsigankov, Nikolay (Department of Geosciences, The University of Arizona, 1998-01-01)
      Samples of >40 pine trees were collected from around the Chernobyl NPP for radiocarbon measurement, to determine the spatial distribution of excessive 14C in tree rings from 1986 consequent upon accidental radiocarbon release. Tree samples were collected during 1995-1996 from sites situated at distances >2.5 km from the NPP and covering a variety of directions in relation to the NPP. To evaluate Delta-14C for 1986 annual rings, we compared 14C levels for separate 1985-1987 annual rings, taking into account the trend of operational releases. Early and late wood samples for 1986 annual tree rings were measured separately to increase the sensitivity and precision of measurements. The maximum value observed for excessive accidental radiocarbon levels (Delta-14C) was found to be 124 pMC (281.6 Bq kg-1 C). We present Delta-14C values for examined sites; their spatial distribution shows a high irregularity of atmospheric 14C depending on direction from the NPP. Using obtained data, we reconstruct the temporal behavior of 14C release during the Chernobyl accident with the aid of atmospheric transport modeling. The total amount of 14C released from 26 April to 5 May 1986 has been estimated as 44 TBq.
    • 14C Cycle in the Hot Zone Around Chernobyl

      Kovaliukh, Nikolai N.; Skripkin, Vadim V.; van der Plicht, Johannes (Department of Geosciences, The University of Arizona, 1998-01-01)
      Radiocarbon from the Chernobyl accident was released mainly in two forms: fine dispersed reactor graphite, and carbon dioxide from burning graphite. The CO2 was partly assimilated by annual and perennial vegetation. Reactor graphite dispersed over a wide territory was taken up biochemically by micromicetes, transforming non-organic carbon of the reactor graphite into organic matter. Organic matter of micromicetes is the main nutrition product for soil organisms such as bacteria, worms, larvae of insects, small beetles, etc. The following relatively independent trophic chains are considered: 1. Carbon dioxide —> leaves, grass —> insects; 2. Graphite —> micromicetes, protozoa, insects. The 14C content in beetles of different species sampled in the 30-km hot zone of the Chernobyl accident site in 1986-1988 agrees well with the contamination levels of insect habitats as well as with their biology.
    • 14C Database and Geographic Information System for Western Siberia

      Orlova, Lyobov A.; Kuzmin, Yaroslav V.; Zolnikov, Ivan D. (Department of Geosciences, The University of Arizona, 1998-01-01)
      We illustrate here the combined use of geographic information system (GIS) technology and a radiocarbon database for analysis of the environmental components and ancient sites in Western Siberia during the period 10-45 ka BP. In total, 230 14C dates from 75 Late Pleistocene outcrops and Paleolithic sites were used to generate paleolandscape maps and to establish the features of the spatiotemporal distribution of Paleolithic sites.
    • 14C Dating of Bone Using Gamma-Carboxyglutamic Acid and Alpha-Carboxyglycine (Aminomalonate)

      Burky, Richard R.; Kirner, Donna L.; Taylor, R. E.; Hare, P. E.; Southon, John R. (Department of Geosciences, The University of Arizona, 1998-01-01)
      Radiocarbon determinations have been obtained on gamma-carboxyglutamic acid [Gla] and alpha-carboxyglycine (aminomalonate) [Am] as well as acid-and base-hydrolyzed total amino acids isolated from a series of fossil bones. As far as we are aware, Am has not been reported previously in fossil bone and neither Gla nor Am 14C values have been measured previously. Interest in Gla, an amino acid found in the non-collagen proteins osteocalcin and matrix Gla-protein (MGP), proceeds from the suggestion that it may be preferentially retained and more resistant to diagenetic contamination affecting 14C values in bones exhibiting low and trace amounts of collagen. Our data do not support these suggestions. The suite of bones examined showed a general tendency for total amino acid and Gla concentrations to decrease in concert. Even for bones retaining significant amounts of collagen, Gla (and Am extracts) can yield 14C values discordant with their expected age and with 14C values obtained on total amino-acid fractions isolated from the same bone sample.
    • 14C Levels in the Vicinity of Two Swedish Nuclear Power Plants and at Two "Clean-Air" Sites in Southernmost Sweden

      Stenström, Kristina; Skog, Göran; Thornberg, Charlotte; Erlandsson, Bengt; Hellborg, Ragnar; Mattsson, Sören; Persson, Per (Department of Geosciences, The University of Arizona, 1998-01-01)
      14C is one of the radionuclides that are produced to different degrees by neutron-induced reactions in all types of nuclear reactors. Part of the 14C created is continuously released into the surrounding environment during normal operation as airborne effluents in various chemical forms (such as CO2, Co and hydrocarbons) through the ventilation system of the plant. Because of the biological importance of carbon and the long half-life of 14C, it is of interest to measure the releases and their incorporation into living material. We report here on the 14C activity concentrations in annual tree rings and the air around two Swedish nuclear power plants, as well as the background 14C activity levels from two reference sites in southern Sweden from 1973-1996. We used both accelerator mass spectrometry (AMS) and decay counting in the investigation.
    • 14C Measurements at PWR-Type Nuclear Power Plants in Three Middle European Countries

      Uchrin, György; Hertelendi, Ede; Volent, Gabor; Slavik, Ondrej; Moravek, Jozef; Kobal, Ivan; Vokal, Barbara (Department of Geosciences, The University of Arizona, 1998-01-01)
      Regular 14C sampling of discharged air began in 1988 at Paks Nuclear Power Plant (NPP), Hungary, and in 1991 at NPPs in Krsko, Slovenia and Bohunice, Slovakia. Monitoring of 14C discharges is carried out at all NPPs with similar differential samplers continuously collecting 14C in the form of 14CO2 and 14CnHm. The main results of airborne discharge monitoring are as follows: 14C activity concentration varied roughly within a factor of two around their mean values, 125 Bq m-3and 90 Bq m-3 for Paks and for Krsko NPP, respectively. The pattern of discharge for Bohunice NPP is slightly different from that at the other two stations. At Bohunice, there has been a continuous increase in the discharge rate at power unit V1, starting with 70 Bq m-3 in 1991 and reaching a value of 190 Bq m-3 in 1995. The values for power unit V2 are 50 Bq m-3 and 82 Bq m-3. The average normalized yearly discharge rates are 0.887 (TBqGWe-1 yr-1) for Paks, 0.815 (V1) and 0.500 (V2) for Bohunice, and 0.219 for Krsko. Most of the discharged 14C is in hydrocarbon form, 95% for Paks and Bohunice V2, but the CO2 fraction may reach 25% or 43% at Bohunice V1 and Krsko, respectively. At Bohunice V1, not only the discharge rate increased but the 14CO2 ratio to the total changed from 30% to 13%. The local radiological impact is estimated to be 1.5 mu Sv a-1 for Paks, 1.7 mu Sv a-1 for Bohunice, and 0.12 mu Sv a-1 for Krsko. The 14C excess in the environment has been measured at Paks NPP since 1989. Based on the monitoring data, the long-term average 14C excess from the Paks NPP was D-14C = 50 per mil for hydrocarbons. Tree-ring analysis has shown a slight excess around Krsko NPP: D-14C is equal to 199.9 per mil for a tree at 1 km from the NPP compared with a "reference" one for which D 14C was equal to 111.6 per mil (in 1994).
    • 14C Measurements of Sub-Milligram Carbon Samples from Aerosols

      Weissenbök, Roland; Biegalski, Steven R.; Currie, Lloyd A.; Klinedinst, Donna B.; Golser, Robin; Klouda, George A.; Kutschera, Walter; Priller, Alfred; Rom, Werner; Steier, Peter; et al. (Department of Geosciences, The University of Arizona, 1998-01-01)
      Accelerator mass spectrometry (AMS) at the milligram level is routinely performed, but it is difficult to go substantially below 100 micrograms of carbon. We discuss various approaches for sample preparation, machine operation and data evaluation, to meet the special requirements of 14C AMS measurements at the microgram-carbon level. Furthermore, we present first results obtained at the Vienna Environmental Research Accelerator (VERA) from 14C measurements of a snow sample from Gaithersburg, Maryland, USA, prepared at the National Institute of Standards and Technology (NIST).
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      Department of Geosciences, The University of Arizona, 1998-01-01
    • A 40,000-Year Varve Chronology from Lake Suigetsu, Japan: Extension of the 14C Calibration Curve

      Kitagawa, Hiroyuki; van der Plicht, Johannes (Department of Geosciences, The University of Arizona, 1998-01-01)
      A sequence of annually laminated sediments is a potential tool for calibrating the radiocarbon time scale beyond the range of the absolute tree-ring calibration (11 ka). We performed accelerator mass spectrometric (AMS) 14C measurements on >250 terrestrial macrofossil samples from a 40,000-yr varve sequence from Lake Suigetsu, Japan. The results yield the first calibration curve for the total range of the 14C dating method.
    • A New 14C Calibration Data Set for the Last Deglaciation Based on Marine Varves

      Hughen, Konrad A.; Overpeck, Jonathan T.; Lehman, Scott J.; Kashgarian, Michaele; Southon, John R.; Peterson, Larry C. (Department of Geosciences, The University of Arizona, 1998-01-01)
      Varved sediments of the tropical Cariaco Basin provide a new 14C calibration data set for the period of deglaciation (10,000 to 14,500 years before present: 10-14.5 cal ka BP). Independent evaluations of the Cariaco Basin calendar and 14C chronologies were based on the agreement of varve ages with the GISP2 ice core layer chronology for similar high-resolution paleoclimate records, in addition to 14C age agreement with terrestrial 14C dates, even during large climatic changes. These assessments indicate that the Cariaco Basin 14C reservoir age remained stable throughout the Younger Dryas and late Allerod climatic events and that the varve and 14C chronologies provide an accurate alternative to existing calibrations based on coral U/Th dates. The Cariaco Basin calibration generally agrees with coral-derived calibrations but is more continuous and resolves century-scale details of 14C change not seen in the coral records. 14C plateaus can be identified at 9.6, 11.4, and 11.7 14C ka BP, in addition to a large, sloping "plateau" during the Younger Dryas (approximately 10 to 11 14C ka BP). Accounting for features such as these is crucial to determining the relative timing and rates of change during abrupt global climate changes of the last deglaciation.
    • A Remotely Operated, Field-Deployable Tritium Analysis System for Surface and Ground Water Measurement

      Noakes, J. E.; Spaulding, J. D.; Neary, M. P. (Department of Geosciences, The University of Arizona, 1998-01-01)
      We have worked in collaboration with the Westinghouse Savannah River Company and Packard Instrument Company to develop a prototype instrument for remote, near real-time, in situ analysis of environmental levels of tritium in surface and ground water samples. The unit consists of a Packard Radiomatic(TM) 525TR liquid scintillation counter that has been modified to achieve lower detection levels through background reduction using Packard's After-Pulse Burst Discrimination electronics and an auxiliary Bi4Ge3O12 scintillation detector guard. The system is fully programmable to enable remote calibration, sample collection, sample analysis, reconfiguration of operational mode and interrogation for analytical results.
    • A Review of 14C Waste Arising from the Nuclear Industry in the United Kingdom

      McNamara, Niall; McCartney, Martin; Scott, E. M. (Department of Geosciences, The University of Arizona, 1998-01-01)
      We report on a review of 14C production and release from the nuclear industry in the United Kingdom (UK). Using earlier predictions (Bush, White and Smith 1984) it is estimated that a total of 1764 TBq of 14C would have been produced in UK graphite-moderated reactors up to the end of 1995, and 135 TBq of this total would have been released. Release rates, based on reported discharges, of 5.1 and 0.93 TBq GW(e)a-1 have been derived for Magnox reactors and Advanced Gas Cooled Reactors (AGRs), respectively. Using these new figures, cumulative discharges of 14C up to 1995 from reactors have been estimated at 531 TBq. The combination of these reactor discharges and the reported discharges from Sellafield (388 TBq) and Amersham (52 TBq) suggest a total cumulative release of 971 TBq of 14C up to the end of 1995.
    • A Tree-Ring and 14C Chronology of the Key Sayan-Altai Monuments

      Zaitseva, G. I.; Vasiliev, S. S.; Marsadolov, L. S.; van der Plicht, J.; Sementsov, Anatoly A.; Dergachev, Valentin A.; Lebedeva, L. M. (Department of Geosciences, The University of Arizona, 1998-01-01)
      We present a radiocarbon chronology of key Sayan-Altai monuments from the Scythian period, based on a statistical analysis of dates produced in the 1980s and now supplemented with new dates. These new 14C dates were produced for samples from the Tuekta-1 barrows (burial mounds) and were measured both in St. Petersburg and Groningen. These tree-ring samples were fitted to the calibration curve. Chronologies were established for the Arzhan, Tuekta-1 and Pazyryk-5 barrows. The time of the construction of the Arzhan and Pazyryk-5 barrows is the 9th and late 5th-4th centuries BC, respectively, and agrees with archaeology. According to new data obtained, the time of the Tuekta-1 barrow construction is some years older than has been accepted thus far by archaeologists.
    • AMS and Microprobe Analysis of Combused Particles in Ice and Snow

      Biegalski, Steven R.; Currie, L. A.; Fletcher, R. A.; Klouda, G. A.; Weissenbök, Roland (Department of Geosciences, The University of Arizona, 1998-01-01)
      Ice cores and snow pits of the cryosphere contain particles that detail the history of past atmospheric air compositions. Some of these particles result from combustion processes and have undergone long-range transport to arrive in the Arctic. Recent research has focused on the separation of particulate matter from ice and snow, as well as the subsequent analysis of the separated particles for 14C with accelerator mass spectrometry (AMS) and for individual particle compositions with laser microprobe mass analysis (LAMMA). The very low particulate concentrations in Arctic samples make these measurements a challenge. The first task is to separate the particles from the ice core. Two major options exist to accomplish this separation. One option is to melt the ice and then filter the meltwater. A second option is to sublimate the ice core directly, depositing the particles onto a surface. This work demonstrates that greater control is obtained through sublimation. A suite of analytical methods has been used for the measurement of the carbon in snow and ice. Total carbon was analyzed with a carbon/nitrogen/hydrogen (CHN) analyzer. AMS was used for the determination of carbon isotopes. Since source identification of the carbonaceous particles is of primary importance here, the use of LAMMA was incorporated to link individual particle molecular-structural patterns to the same group of particles that were measured by the other techniques. Prior to this study, neither AMS nor LAMMA had been applied to particles contained in snow. This paper discusses the development and limitations of the methodology required to make these measurements.
    • An Attempt at Absolute 14C Dating

      Szabo, Jacob; Carmi, Israel; Segal, Dror; Mintz, Eugenia (Department of Geosciences, The University of Arizona, 1998-01-01)
      The accepted state-of-the-art 14C dating method relies on calibration curves to determine initial 14C levels in a sample. The paper reconsiders the basis of 14C dating and offers a possible alternative that eliminates the need to employ calibration curves. The idea is to measure the level of radiogenic nitrogen atoms retained in the sample molecules after 14C beta-decay. The practicality of this alternative method still has to be proven.
    • An Experiment to Refute the Likelihood of Cellulose Carboxylation

      Hedges, R. E. M.; Bronk Ramsey, Christopher; Van Klinken, G. J. (Department of Geosciences, The University of Arizona, 1998-01-01)
      To test the hypothesis that cellulose in linen can be carboxylated at high temperatures in the presence of CO2, water and silver, we heated two aliquots of cellulose extracted from old wood in glass ampoules, adding Ag powder to one to test its potential action as a catalyst for the carboxylation reaction. AMS measurement of the heated aliquots showed no statistically significant difference in 14C content from the "uncarboxylated" cellulose. We conclude that carboxylation is not a systematic source of error in the dating of cellulose-containing materials such as the linen in the Shroud of Turin.
    • An Ion Source for the HVEE 14C Isotope Ratio Mass Spectrometer for Biomedical Applications

      Mous, Dirk W.; Fokker, Wim; Van Den Broek, Rein; Koopmans, Ron; Bronk Ramsey, Christopher; Hedges, R. E. M. (Department of Geosciences, The University of Arizona, 1998-01-01)
      During the past two decades, accelerator mass spectrometry (AMS) has allowed major developments in many areas of geosciences and archaeology. In the near future, AMS should realize a similar potential in the field of biomedical research, leading ultimately to clinical applications. For such applications, the required instrument differs significantly from that presently used in the field of 14C dating. Whereas the needed accuracy and sensitivity is more than an order of magnitude less demanding than that for present state-of-the-art 14C instrumentation, the widespread acceptance of 14C AMS in biomedical research will require AMS spectrometers that are small, simple to operate and capable of handling CO2 samples. In order to satisfy these demands, HVEE has developed a compact 14C AMS spectrometer dedicated to biomedical research. The instrument consists of a compact accelerator with a footprint of 2.25 x 1.25 m and an ion source that features direct CO2 acceptance and optimal user friendliness. Having previously described the layout and design of the accelerator, we here discuss progress on the accelerator and present the design and first results of the CO2 ion source.
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      Department of Geosciences, The University of Arizona, 1998-01-01
    • Attempt to Affect the Apparent 14C Age of Cotton by Scorching in a CO2 Environment

      Long, Austin (Department of Geosciences, The University of Arizona, 1998-01-01)
      One explanation for the radiocarbon dates on the Shroud of Turin being younger than the time of Christ is that the heat from a fire, which scorched a portion of the Shroud, may have affected the 14C content (dates) on the shroud by affecting molecular exchange between the fabric and atmospheric carbon. This report describes a laboratory test on the susceptibility of cellulose, in the form of cotton, to incorporate carbon from CO2 while it is heated in a closed tube with carbon dioxide until the cotton considerably darkened. To maximize the effect of this hypothetical process, we simulated the shroud material with cotton that had a 14C level of 0.55 modern (55 pMC, equivalent to 4800 yr), and the atmosphere with pure CO2, which had a 14C level of 1.3 modern (130 pMC). No measurable 14C transferred from the gas phase to the solid phase. The implication of this test is that scorching is an unlikely mechanism to affect the apparent age of cellulose-like material.