• Radiocarbon, Volume 28, Number 3 (1986)

      American Journal of Science, 1986-01-01
    • Radiocarbon, Volume 28, Number 1 (1986)

      American Journal of Science, 1986-01-01
    • Foreword

      Stuiver, Minze (American Journal of Science, 1986-01-01)
    • Editorial Comment

      Stuiver, Minze (American Journal of Science, 1986-01-01)
    • University of Wisconsin Radiocarbon Dates XXIII

      Steventon, Raymond L.; Kutzbach, John E. (American Journal of Science, 1986-01-01)
    • University of Texas at Austin Radiocarbon Dates XV

      Valastro, S.; Mott Davis, E.; Varela, Alejandra G.; Lisk, Susan V. (American Journal of Science, 1986-01-01)
    • University of Granada Radiocarbon Dates III

      Gonzalez-Gomez, Celilio; Sanchez-Sanchez, Purificacion; Villafranca-Sanchez, Elena (American Journal of Science, 1986-01-01)
    • Laboratories

      American Journal of Science, 1986-01-01
    • Index

      American Journal of Science, 1986-01-01
    • A Discussion of an Alternate Approach to the Evaluation of Sample Contamination

      Gurfinkel, D. M. (American Journal of Science, 1986-01-01)
      An approach to the evaluation of sample contamination based on the monitoring of contaminant removal during pretreatment is described. Spot tests and colorimetric reactions which could be adapted for this purpose are suggested.
    • Validity of 14C Ages of Carbonates in Sediments

      Chen, Yijian; Polach, Henry (American Journal of Science, 1986-01-01)
      This review is based on geologic surveys carried out in Australia and China as well as on more than 300 14C dates published in Radiocarbon. Evaluated are the origins and pathways of carbonate formation, stable isotopic composition, carbonate nodule growth rates and paleo-climatic effects. The three identified delta-13C abundance peaks are unrelated to environment and carbon source whilst 14C ages group themselves into periods corresponding to past humid warm climate. It is concluded that the major error in caliche dating is due to incorporation of old limestone whilst error on nodule dating is related to their slow growth rate. Thus, caliche antedates and nodules postdate the times of their deposition. delta-13C values cannot be used to correct for limestone or atmospheric contamination effects
    • Using dBASE II for Retrieval of Radiocarbon Data

      Selsing, Lotte; Simonsen, Aud (American Journal of Science, 1986-01-01)
      A "C14" data base has been created for internal use of 14C dates with an Osborne-1 system. It uses a CP/M operating system, Z-80 CPU, and dBASE II software program. The structure meets the users' requirements of information and easy retrieval. The video display is quite compact, as a record of 32 fields is edited to fill a screen of 22 lines. A standard printout is edited to make room for two records per page and contains all information from these records. Searching may take place in all fields or parts of fields, in interval(s) in one or more fields and in various combinations of the prescribed methods of searching. A field called KEYWORDS is established to ease search operations. "C14" may be adapted to individual requirements and equipment with small adjustments
    • Use of AMS 14C Analysis in the Study of Problems in Aspartic Acid Racemization-Deduced Age Estimates on Bone

      Ennis, Paul; Noltmann, E. A.; Hare, P. E.; Slota, P.; Payen, L. A.; Prior, C. A.; Taylor, R. E. (American Journal of Science, 1986-01-01)
      Major discordances between AMS 14C- and aspartic acid racemization (AAR)deduced age estimates on bone samples have led to an examination of factors other than time and temperature that can fundamentally influence the degree of racemization observed in fossil bone. Our studies support previous suggestions that for many bone samples the chemical state of amino acids must be routinely considered if AAR-deduced age estimates are to be used to make meaningful chronologic inferences.
    • 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.
    • Uptake of Anthropogenic CO2 by Lateral Transport Models of the Ocean Based on the Distribution of Bomb-Produced 14C

      Peng, Tsung Hung (American Journal of Science, 1986-01-01)
      The pattern of global water column inventories of bomb-produced 14C suggests that a sizeable portion of bomb 14C that entered the Antarctic, northern Pacific, and tropical oceans has been transported to adjacent temperate regions. Models of lateral transport of surface water in the Atlantic, Indian, and Pacific Oceans are based on this distribution pattern. Upwelling of bomb-14C-free water from below takes place in the Antarctic, northern Pacific, and tropical regions; downwelling of surface water occurs in the temperate oceans and northern Atlantic. Uptake of excess CO2 by these models is calculated using the observed Mauna Loa pCO2 record as an input function. Results indicate that 35% of fossil fuel CO2 is taken up by these model oceans during the period 1.958-1980. Considering the observed airborne fraction of 0.55, it appears that ca 10% of the global fossil fuel CO2 is still missing.
    • University of Lund Radiocarbon Dates XVIII

      Håkansson, Sören (American Journal of Science, 1986-01-01)
    • University of Lund Radiocarbon Dates XIX

      Håkansson, Sören (American Journal of Science, 1986-01-01)