• Lódź Radiocarbon Dates II

      Kanwiszer, Andrzej; Trzeciak, Pawel (American Journal of Science, 1986-01-01)
    • Urban Atmospheric 14CO and 14CH4 Measurements by Accelerator Mass Spectrometry

      Klouda, G. A.; Currie, L. A.; Donahue, D. J.; Jull, A. J. T.; Naylor, M. H. (American Journal of Science, 1986-01-01)
      Atmospheric gas samples (0.1 m3) were collected at ground level during January/February 1984 in Las Vegas, Nevada for 14C/13C accelerator mass spectrometry and total abundance measurements of CO and CH4. During winter months in this locale, CO concentrations can occur at 10 to 100 times background, occasionally exceeding the National Ambient Air Quality Standard (NAAQS). Methane concentrations show a slight enhancement (-24%) above the background (non-urban troposphere) level. A comparison of CO and CH4 concentrations shows a good linear correlation which may indicate a common source. Preliminary 14C/13C results of the two species suggest that fossil emissions are the predominant source of excess CO and CH4 in the samples taken. Estimates of anthropogemc CO and CH4 are important for source apportionment of combustion emissions. In addition, this information is valuable for understanding the global CO and CH4 cycles and, therefore, human impact on climate and the stratospheric ozone layer.
    • Laboratories

      American Journal of Science, 1986-01-01
    • Multiple Dating of a Long Flowstone Profile

      Geyh, Mebus A.; Hennig, G. J. (American Journal of Science, 1986-01-01)
      Dense speleothem samples are considered as closed systems and are, therefore, possibilities for any dating method. Four dating methods (14C, U/Th, paleomagnetism, and electron spin resonance = ESR) were used for samples up to 1,000,000 yr old and taken along a vertical flowstone profile in the Heggen cave in West Germany. Also delta-18O and delta-13C analyses were carried out. The reliability of the results of each method is dependent on the diagenetic processes that took place during the complex growth history of the flowstone. Speleothem growth was interrupted during glacial periods. During interglacial periods, at least the stalagmite growth rate was greater by one order of magnitude than during interstadial periods. During the periods of low interstadial growth rate various processes might have changed the 14C, 18O, and 13C concentrations, leaching might have removed uranium, recrystallization might have moved thorium several centimeters, and increased content of radon in the cave might have exaggerated the accumulated dose (AD) at the speleothem surface. As a result, 14C ages may be too small and U/Th as well as ESR data may be too large.
    • Operation of the NSF-Arizona Accelerator Facility for Radioisotope Analysis and Results from Selected Collaborative Research Projects

      Linick, T. W.; Jull, A. J. T.; Toolin, L. J.; Donahue, D. J. (American Journal of Science, 1986-01-01)
      Radiocarbon dating at the Arizona accelerator facility has improved substantially in the last three years. Since starting to use graphite targets (see Jull et al, 1986), we have been able to obtain routinely a precision of ca +/- 1 % (ca 80 yr) for relatively modern material. Our routine technique of tuning and operating the tandem accelerator mass spectrometer (TAMS) and our method of calculating 14C results are discussed in detail. Data on activity ratios of oxalic acid-II/oxalic-I are presented. Examples of the wide variety of projects on which we have collaborated are given. Brief discussions of three such projects are presented for our colleagues who were unable to attend this conference: an Arizona Indian archaeologic project, a study of megafaunal extinctions, and a study of the growth of phosphorite nodules on the sea floor off the Peruvian coast.
    • On the Initial 14C Activity of Karst Aquifers with Short Mean Residence Time

      Krajcar-Bronić, Ines; Horvatinčić, Nada; Srdoč, Dušan; Obelić, Bogomil (American Journal of Science, 1986-01-01)
      The 14C activity of total dissolved inorganic carbon (DIC) as well as tritium activity and stable isotope content (13C, 2H, 18O) of spring water were measured for 3 consecutive years at 3 karst springs that feed Plitvice Lakes, NW Yugoslavia. The constant chemical and stable isotope composition and temperature indicated well mixed aquifers. A very short mean residence time of underground water (2-5 yr) was determined by tritium activity measurements. Measured 14C activities of 3 karst springs varied from 60.0% to 82.5%. The measured 14C activities were compared with calculated 14C activities based on various models using measured values of 14C activity of soil at different depths and 13C content of limestone, plants, and soils from the recharge area. Our measurements indicate that recharge systems in karst aquifers are open to the atmosphere. The atmospheric CO2 contributes to the 13C content and the 14C activity of ground water to an estimated extent which varies between 10 and 40% of DIC.
    • Origins of Carbon in Potsherds

      Gabasio, Martine; Evin, Jacques; Arnal, Gaston Bernard; Andrieux, Philippe (American Journal of Science, 1986-01-01)
    • Production of Graphite Targets by Deposition from Co/H2 for Precision Accelerator 14C Measurements

      Jull, A. J. T.; Donahue, D. J.; Hatheway, A. L.; Linick, T. W.; Toolin, L. J. (American Journal of Science, 1986-01-01)
      A method has been developed at the Arizona AMS facility for production of graphite directly from CO2 by catalytic reduction of CO/H2 mixtures. The method is a modification of procedures discussed by Vogel et al (1984). Currents of 12C- from these targets vary considerably, but have a median value which is 70% of that achieved from spectroscopic graphite. Precisions of +/- 60 to 100 yr are routinely achieved for 14C ages of 5000-yr-old samples containing one milligram of carbon. The yield of 14C from "blank" targets is 0.6 +/- 0.1% of that from modern material.
    • Radiocarbon Activity Variation in Dated Tree Rings Grown in Mackenzie Delta

      Fan, C. Y.; Tie-Mei, Chen; Si-Xun, Y.; Kai-Mei, Dai (American Journal of Science, 1986-01-01)
      We measured the Delta-14C values in 57 rings (from AD 1824 to 1880) of a white spruce grown in Mackenzie Delta (68 degrees N, 130 degrees W), as part of our continuing study of the Delta-14C variation related to solar activities. The values exhibit a 10 per mil fluctuation with an 11-year periodicity anti-correlated with the solar activity cycle. We also measured the Delta-14C values in 6 rings (from AD 1940 to 1945). The abnormally high value in the 1943 ring may be due to two large solar flares occurring in 1942.
    • Radiocarbon, Volume 28, Number 3 (1986)

      American Journal of Science, 1986-01-01
    • Radiocarbon Age Calibration Back to 13,300 Years BP and the 14C Age Matching of the German Oak and US Bristlecone Pine Chronologies

      Stuiver, Minze; Kromer, Bernd; Becker, Bernd; Ferguson, C. W. (American Journal of Science, 1986-01-01)
    • Radiocarbon, Volume 28, Number 1 (1986)

      American Journal of Science, 1986-01-01
    • Radiocarbon Calibration Data for the 6th to the 8th Millennia BC

      Kromer, Bernd; Rhein, Monika; Bruns, Michael; Schoch-Fischer, Hildegard; Münnich, Karl Otto; Stuiver, Minze; Becker, Bernd (American Journal of Science, 1986-01-01)
      14C calibration curves derived from South German oak tree-ring series are presented. They cover the interval between 4400 and 7200 BC complementing existing data sets and extending them to older periods. The atmospheric 14C level before 6200 BC no longer follows the long-term sinusoidal trend fitted to the bristlecone data. This observation is supported by a tentative match of the Main 9 series.
    • Radiocarbon Dates from an Upland Site of the Kona Field System, Hawai'i Island, Hawaii

      Kawachi, C. T. (American Journal of Science, 1986-01-01)
      The following samples were excavated in July 1985 in an upland (elev 609 m) prehistoric agricultural site in the Kona Field System on the west coast of Hawai'i Island. 14C measurements were done by Beta Analytic Inc, Coral Gables, Florida. The samples were first carefully examined and picked for rootlets and any other non-contemporaneous carbonaceous materials. They were then subjected to an alternating series of hot acid and alkali solutions, interspersed with washings to neutrality with hot distilled water to eliminate carbonates and humic acids. After gentle drying the clean charcoal was benzene synthesized and counting of the 14C activity with a liquid scintillation spectrometer measured for 14C content. All steps in the analysis proceeded normally. Soil descriptions are based on information supplied by Patti Spears and Jeff Yamauchi. Hawaii Puaa, North Kona series Charcoal from 2 loci within project site (19 degrees 38'30"N, 155 degrees 56'30"E).
    • Radiocarbon Concentration of California Aerosols

      Berger, Rainer; McJunkin, David; Johnson, Roberta (American Journal of Science, 1986-01-01)
      In this study the origin of the carbonaceous fraction of total suspended particles (TSP) in air was analyzed. While the summer data show increasing carbon concentrations in the Los Angeles air basin from west to east, in the winter high levels of carbon particles can be found over the coast. The smallest and most dangerous particle fraction is principally composed of fossil carbon.
    • Radiocarbon Dating Blood Residues on Prehistoric Stone Tools

      Nelson, D. E.; Loy, T. H.; Vogel, J. S.; Southon, J. R. (American Journal of Science, 1986-01-01)
      We report here the first radiocarbon dating of blood residues on prehistoric stone tools. The residues found on two stone artifacts were subjected to various exploratory biochemical techniques to identify the species from which they were derived and to separate a suitable sample for dating by accelerator mass spectrometry. Although these techniques need much further development and detailed testing, the ages obtained in this first study were consistent with other data, indicating that the concept is viable. For the first time, the time of use of stone tools has been found directly, rather than by stratigraphic or other archaeologic inferential techniques.
    • A 14C Electronic Measurement System with a Microcomputer

      Walanus, Adam (American Journal of Science, 1986-01-01)
      Even though the reliability of equipment has improved, the quality of measurement should still be checked. This task may be performed by a microcomputer with the physicist's intervention only when an error in measurement is detected.