• High-Precision 14C Measurement of Irish Oaks to Show the Natural 14C Variations from 200 BC to 4000 BC

      Pearson, G. W.; Pilcher, J. R.; Baillie, M. L. (American Journal of Science, 1983-01-01)
      Bi-decade samples of dendrochronologically matched Irish Oak, measured with a precision of ca +/20 years, covering the period 200 to 4000 BC are presented. The data are compared with the published data of Suess, de Jong, and Mook to provide a general calibration of the 14C time scale for this period. Although the dendrochronologic sequences presented are not absolutely tied to present, the best fit (based on 14C evidence) of the Belfast data to absolute chronologies, the error and evidence associated with such positioning is given. The intervals chosen for analysis were 20 years, reducing slightly the resolution of short-term variations when compared to 10-year intervals, which are sometimes measured. However, this calibration would suffice for most scientific purposes and certainly for the calendrical conversion of 14C dates derived from archaeologic samples.
    • High-Precision 14C Measurement of Irish Oaks to Show the Natural Atmospheric 14C Variations of the AD Time Period

      Pearson, G. W.; Baillie, M. G. L. (American Journal of Science, 1983-01-01)
      The high-precision 14C measurement of bi-decade and decade samples of Irish Oak for the time period AD 50 to 1830 is presented. The samples were taken from dendrochronologically dated Irish Oak providing an absolute chronology for this period. While the natural atmospheric 14C concentration shows cyclic deviations from a constant value, the amplitudes of such deviations vary considerably. Repeated measurement and interlaboratory checks justify a claim to accuracy in the data given. Comparison of a large number of data sets between Belfast and Seattle show that the different techniques of scintillation counting of 14C6H6 and gas counting of 14CO2 derived from different wood species grown in different continents give no significant bias. Thus, it is justifiable to use this data set as a high-precision calibration curve for the AD period. Over most of this period bi-decade samples were measured giving a slightly reduced resolution of shortterm variation when compared to the measurement of decade intervals; however, any difference is not apparent when such curves are compared. It is of much greater importance that a comparison of data sets is without bias if a combined calibration curve is to have sufficient integrity for general use. Averaging the data from Belfast and Seattle would improve the validity of such an AD 14C calibration curve since it would tend to smooth out slight local variations and become internationally more acceptable.
    • International Agreements and the Use of the New Oxalic Acid Standard

      Stuiver, Minze (American Journal of Science, 1983-01-01)
    • Long-Term Variability of Temperature and 14C in the Gulf Stream: Oceanographic Implications

      Druffel, Ellen M. (American Journal of Science, 1983-01-01)
      Variability in temperature and 14C levels are recorded in coralline aragonite that grew in the Gulf Stream during the past four centuries. In particular, 18O/16O ratios reflect a decrease of ca 1 degree C in surface water temperature during the latter part of the Little Ice age. 14C levels also rose in the surface waters of the Gulf Stream and in atmospheric CO2 during the Maunder minimum. These observations indicate that ocean circulation may have been significantly different in the North Atlantic around the beginning of the 18th century.
    • Mathematical Modeling of the Distribution of Natural 14C, 234U, and 238U in a Regional Ground-Water System

      Pearson, F. J.; Noronha, C. J.; Andrews, R. W. (American Journal of Science, 1983-01-01)
    • Measurement of Carbon Fixation and Allocation Using 11C-Labeled Carbon Dioxide

      Strain, B. R.; Goeschl, J. D.; Jaeger, C. H.; Fares, Youhanna; Magnuson, C. E.; Nelson, C. E. (American Journal of Science, 1983-01-01)
    • Mid-Wisconsinan Radiocarbon Dates from Mastodon- and Mammoth-Bearing Springs, Ozark Highland, Missouri

      Haynes, C. V.; Stuiver, Minze; Haas, Herbert; King, J. E.; King, F. B.; Saunders, J. J. (American Journal of Science, 1983-01-01)
    • Miniature Signals and Miniature Counters: Accuracy Assurance Via Microprocessors and Multiparameter Control Techniques

      Currie, L. A.; Gerlach, R. W.; Klouda, G. A.; Ruegg, F. C.; Tompkins, G. B. (American Journal of Science, 1983-01-01)
      When 14C signals approach background levels, the validity of assumptions concerning Poisson counting statistics and measurement system stability becomes crucial in interpreting the resultant low-level counting observations. This has been demonstrated in our previous work on detection limits for non-Poisson error and it is critical in our current studies of carbonaceous pollutants, where the 14C signal from just 5 mg C is comparable to that of the background for our miniature gas proportional counters. To assure data quality, our multi-detector system is designed for the on-line monitoring of critical parameters that reflect both the (statistical) nature of the non-Poisson errors and the underlying (physical) causes. It sends >60 bits of information/pulse to a microprocessor which automatically generates, for each counting period, two-dimensional spectra and multiparameter correlation and control charts. To evaluate the validity of long-term counting of 1–10 mg C we use robust (statistical) estimators, optimal counting interval subdivision, and time series analysis of the individual pulses. New opportunities for selective sampling and chemical fractionation which come with the small sample measurement capability have led us to give special attention also to higher control levels, involving e g, isotonic heterogeneity and representative standard materials.
    • Modeling of Atmospheric Radiocarbon Fluctuations for the Past Three Centuries

      Damon, P. E.; Sternberg, R. S.; Radnell, C. J. (American Journal of Science, 1983-01-01)
    • Non-Concordance of Radiocarbon and Amino Acid Racemization: Deduced Age Estimates on Human Bone: Implications for the Dating of the Earliest Homo Sapiens in the New World

      Taylor, R. E. (American Journal of Science, 1983-01-01)
      Radiocarbon determinations, employing both decay and direct counting, were obtained on various organic fractions of four human skeletal samples previously assigned ages ranging from 28,000 to 70,000 years on the basis of their D/L aspartic acid racemization values. In all four cases, the 14C values require an order of magnitude reduction in age.
    • Notice to Readers and Contributors

      American Journal of Science, 1983-01-01
    • On a 50-Year "Climate-Free" delta-13C Record from Juniper Tree Rings

      Leavitt, Steven W.; Long, Austin (American Journal of Science, 1983-01-01)
    • On the Origin of Carbonaceous Particles in American Cities: Results of Radiocarbon "Dating" and Chemical Characterization

      Currie, L. A.; Klouda, G. A.; Continetti, R. E.; Kaplan, I. R.; Wong, W. W. W.; Dubay, G. W.; Stevens, R. K. (American Journal of Science, 1983-01-01)
      During the past three years radiocarbon assay has emerged as a primary tool in the quantitative assignment of sources of urban and rural particulate pollution. Its use in several major field studies has come about because of its excellent (fossil/biogenic) discriminating power, because of advances in 14C measurements of small samples, and because of the increased significance of carbonaceous particles in the atmosphere. The problem is especially important in the cities, where increased concentrations of fine particles lead to pollution episodes characterized by poor visibility and changes in the radiation balance (absorption, scattering), and immediate and possibly long-term health effects. Efforts in source apportionment in such affected areas have been based on emissions inventories, dispersion modeling, and receptor modeling – ie, chemical and physical (and statistical) characterization of particles collected at designated receptor sites. It is in the last category that 14C has become quite effective in helping to resolve particle sources. Results are presented for studies carried out in Los Angeles, Denver, and Houston which incorporated 14C measurements, inorganic and organic chemical characterization, and receptor modeling. The 14C data indicated wide ranging contributions of biogenic and fossil carbon sources – eg, <10% to 60% contemporary (biogenic) in Houston – depending on meteorological, biological, and anthropological activity. The combined (chemical, isotopic, statistical) data point to sources such as vehicles, wood combustion, power plants, and vegetation.
    • Participants

      American Journal of Science, 1983-01-01
    • Possibilities in the Dating of Writing Materials and Textiles

      Burleigh, Richard; Baynes-Cope, A. D. (American Journal of Science, 1983-01-01)
    • Possible Depletion in 14C in Trees Growing in Calcareous Soils

      Tauber, Henrik (American Journal of Science, 1983-01-01)
      14C activities of decadal samples from beech trees growing under extreme calcareous conditions were compared to 14C activities of decadal samples of the same age from a beech tree growing in a normal mold soil in order to see whether part of the carbon assimilated during photosynthesis might originate from 14C-deficient carbonates in the soil. The calcareous soils contained from 18 to 52% calcium carbonate, and this carbonate had a mean 14C age of 10,200 to 17,600 years BP. A comparison was also made with the 14C activity of contemporaneous samples from Douglas Fir from the US North Pacific (Stuiver, 1982). No significant depletion in 14C activity in beech trees growing in the highly calcareous soils was detected. The measured mean difference in 14C activity in beech trees from calcareous and non-calcareous sites corresponds to an uptake of 0.12 +/- 0.3% carbon from soil carbonates in the calcareous sites.
    • Production of C- Directly from CO2 Using the ANIS Sputter Source

      Heinemeier, Jan; Andersen, Hans Henrik (American Journal of Science, 1983-01-01)
      Micro-ampere beams of C- have been produced with the Aarhus negative-ion source, operated on CO2 gas. The efficiency of the source and memory effects have been measured, using 13C-enriched CO2, in order to evaluate the applicability of the source to 14C dating by accelerator mass spectroscopy.
    • Radiocarbon Activity Variation in Dated Tree Rings Grown in Mackenzie Delta

      Fan, C. Y.; Tie-Mei, Chen; Si-Xun, Yun; Kai-Mei, Dai (American Journal of Science, 1983-01-01)
      Forty-five tree rings (1881-1925) were taken from a white spruce grown near Campbell River in Mackenzie Delta, Canada, for the measurement of 14C activity variation. Because of the narrowness of the rings, 2 and sometimes 3 rings were combined to yield a total of 21 specimens. The 14C content in these specimens was measured with a liquid scintillation-PM tube counter system of the History Department of Peking University. The data points exhibit a 10 per mil variation, anti-correlated with sunspot numbers. The physical implication is discussed.
    • Radiocarbon Database: A Pilot Project

      Gulliksen, Steinar (American Journal of Science, 1983-01-01)
      Computer storage and surveys of large sets of data should be an attractive technique for users of 14C dates. Our pilot project demonstrates the effectiveness of a text retrieval system, NOVA STATUS. A small database comprising ca 100 dates, selected from results of the Trondheim 14C laboratory, is generated. Data entry to the computer is made by feeding typewritten forms through a document reader capable of optical character recognition. A text retrieval system allows data input to be in a flexible format. Program systems for text retrieval are in common use and easily implemented for a 14C database.