• 14C Dating of Plant Macrofossils in Lake Sediment

      Andree, Michael; Oeschger, Hans; Siegenthaler, Ulrich; Riesen, Trudi; Moell, Markus; Ammann, Brigitta; Tobolski, Kazimierz (American Journal of Science, 1986-01-01)
      Macrofossils of terrestrial plants have been picked from a sediment core taken in Lake Lobsigen, a small lake on the Western Swiss Plateau. The sediments were previously analyzed for pollen composition, plant and animal macrofossils, and stable isotopes. Plant macrofossils were selected near pollen zone boundaries in Late Glacial and early Postglacial sediment for 14C dating by AMS. In the same lake carbonate and gyttja (aquatic plant) samples were dated by decay counting. The dates on terrestrial material are generally younger than those on carbonate and gyttja, ie, material reflecting the 14C/C ratio of dissolved bicarbonate in lake water. This is probably due to a contribution of dissolved limestone carbonate and thus a somewhat reduced 14C/C, ratio in the lake's water (hard water effect).
    • A Study of Errors in 14C Dates of Peat and Sediment

      Olsson, Ingrid U. (American Journal of Science, 1986-01-01)
      It is a well-established fact that 14C dates from lake sediments are usually too old because of contamination with allochthonous material and/or due to discrete reservoir effects. The latter can occur in soft water lakes and may be examined by the 14C measurement of aqueous plants or the carbon dissolved and suspended in the water column. Some plants assimilate CO2 from the sediment. Their 14C activity is then dependent on the sediment accumulation rate and nutrients stored in the root system may also contribute misleading results. If water is filtered through ultra-fine membranes and then treated chemically, several fractions can be isolated for dating. The present study shows that the 14C activity of such fractions varies widely but with the weighted mean indicating an overall deficiency. Even the water from a raised bog evidences a 14C deficiency relative to contemporary atmospheric CO2. Charcoal from an archaeologic site and peat from corresponding layers in a nearby bog have yielded significantly different ages. The fact that the Cladium peat was from a very calcareous area is significant. The risk of contamination by younger root material is also documented.
    • Applications of the Use of Hawthorn Berries in Monitoring 14C Emissions from a UK Nuclear Establishment Over an Extended Period

      Walker, A. J.; Otlet, R. L.; Longley, Harry (American Journal of Science, 1986-01-01)
      The paper describes a study undertaken to examine the dispersion pattern of gaseous emissions, as indicated by 14C uptake in natural materials, around the nuclear reprocessing plant at Sellafield, Cumbria, UK. The extent and directional dispersion of the released 14C is established and its variability over an extended period assessed. Results of measurements taken during three sampling seasons (1981,1982,1983) of the 14C activity in hawthorn berries collected over a wide area are presented and the dispersion pattern contours constructed from them are examined. Only limited agreement of the results with the theoretical relationship 1/r is found and both meteorology and topography are seen to be important in determining the shape of the observed patterns.
    • Carbon Isotopes in Atmospheric CO2 of the Krakow Region: A Two-Year Record

      Kuc, Tadeusz (American Journal of Science, 1986-01-01)
      We have been measuring concentration of atmospheric CO2 and its carbon isotope composition in the Kraków region for about two years. Samples are continuously collected at two-week intervals at ca 20m above ground level, close to the center of the industrialized urban area. Sampled atmospheric CO2 is sorbed in a molecular sieve and, after recovery by heating, is converted to benzene. 14C is measured in a liquid scintillation spectrometer, and delta-13C of the CO2 is determined in a mass spectrometer. The annual record shows winter-summer variation of 14C, 13C, and CO2 concentration. A long-term trend for 1983 and 1984 indicates a slight decrease of 14C activity (122.0 in January 1983; -1.2% per year), a permanent decrease of delta-13CPDB (-9.3 per mil in January 1983; -0.3 per mil per year) and an increase of CO2 concentration (344ppm in January 1983; 1.4ppm per year).
    • delta-13C and Diet: Analysis of Norwegian Human Skeletons

      Johansen, Olav Sverre; Gulliksen, Steinar; Nydal, Reidar (American Journal of Science, 1986-01-01)
      The relationship between 13C content of human bone and the marine fraction in the individual diet is well established. In the present investigation human skeletons from inland and coastal areas in Norway were analyzed. Both regional and chronologic differences are revealed, and larger variability than expected at specific sites indicate more complex cultural adaptations than earlier recognized. Extremely high delta-13C values, comparable with those obtained from Eskimo sites, are found for material from Early Stone Age fishing/hunting communities.
    • Early Slavonic Settlements and Navigation at the Mouth of the Odra River

      Awsiuk, Romuald; Filipowiak, Władyslaw; Goslar, Tomasz; Pazdur, Anna; Pazdur, Mieczysław F. (American Journal of Science, 1986-01-01)
      An attempt is presented to establish an absolute chronology of early Slavonic habitation in the region of the mouth of the Odra River up to the Baltic and to find associations with a series of stave boats and dugouts of different levels of technology and navigation. The methodology of the research project is presented and some conclusions of a general nature are drawn from the results already obtained.
    • Environmental 14C Levels Around the 632 MWe Nuclear Power Plant Krško in Yugoslavia

      Obelić, Bogomil; Krajcar-Bronić, Ines; Srdoč, Dušan; Horvatinčić, Nada (American Journal of Science, 1986-01-01)
      Measurements of 14C activity of atmospheric CO2, vegetables, and tree rings in the area of the 632 MWe power plant Krško in Slovenia, NW Yugoslavia, have been in progress since January, 1984. Sampling stations are located in the area ca 400km2 and are distributed in the direction of the prevailing westerly winds. The closest sampling point is 1.5km NE of the plant exhaust stack, the farthest sampling point is 30km E of the plant. A sampling site at National Park Plitvice in central Croatia was chosen as the 14C reference point not affected by the power plant. An average excess of 2.2% above the reference point activity during normal periods of reactor operation was observed 1.5km from the plant smokestack. Calculations of the 14C release from the power plant was estimated at 0.1 TBq/a. The tree ring activity near the plant followed the 14C activity of the Northern Hemisphere in the past decade. No influence of the power plant release was observed on the tree ring activity.
    • Extension of the Holocene Dendrochronology by the Preboreal Pine Series, 8800 to 10,100 BP

      Becker, Bernd; Kromer, Bernd (American Journal of Science, 1986-01-01)
      Holocene tree-ring chronologies have been established for south-central Europe covering the past 11,000 years. The Hohenheim absolute oak chronology extends to 4089 BC. The 14C-calibrated mid-Holocene floating oak master covers a 3181-year period from ca 4045 to 7225 BC. The earliest well-replicated floating oak master (estimated calendar age 7215 to 7825 BC) extends the European oak dendrochronology back to Boreal times. Further extension of the Holocene dendrochronology has been achieved by subfossil oak and pine trees from the Rhine, Main, and Danube Rivers. A 774-year floating series of Preboreal pine has been established. 14C ages range (from younger to older end) from 9200 to 9800 BP. Within this series a major atmospheric 14C variation is indicated, resulting in nearly constant 14C ages (9600 BP) over a period of 370 tree-rings. The European oak and pine tree-ring chronologies cover without major gaps the entire Holocene epoch. Based on the length of the dendro-records, an approximate solar year age of 11,280 years is calculate for the Holocene/Pleistocene boundary. The Preboreal pine forests along the rivers were replaced by mixed oak forests between 9200 and 8800 BP. By linking the earliest oak masters and the Preboreal pine series, the European dendrochronology can be extended up to the end of Late Glacial times.
    • Gif Natural Radiocarbon Measurements X

      Delibrias, Georgette; Guillier, M.-T.; Labeyrie, Jacques (American Journal of Science, 1986-01-01)
    • Global and Local Effects of 14C Discharges from the Nuclear Fuel Cycle

      McCartney, Martin; Baxter, M. S.; McKay, Keith; Scott, E. Marian (American Journal of Science, 1986-01-01)
      The radiologic impact of 14C produced by the nuclear fuel cycle is assessed at both global and local levels. In the former context, it is predicted here that the specific activity of atmospheric CO2 in the year 2050 will be ca 7.6 pCig^(-1)C. Although this is similar to the present level, the subsequent collective dose commitment could be highly significant. The enhancement of 14C concentrations around the nuclear fuel-reprocessing plant at Sellafield (Windscale) in Cumbria, UK has been monitored over recent years. For example, maximum levels of 27.2 pCig^(-1)C (~350% above natural) during 1984 were observed <1 km from the plant, with enhanced activities detectable to at least 29km. Nevertheless, it is clear that the radiologic significance to the local population is low. The spatial distribution of the excess 14C allows atmospheric dispersion models to be tested in the context of continuous releases and the results thus far show that the Gaussian plume model performs successfully.
    • Groningen 14C Data Base

      Endelsman, F. M. R.; Taayke, E.; Mook, W. G. (American Journal of Science, 1986-01-01)
    • High-Precision 14C Measurement of Irish Oaks to Show the Natural 14C Variations from AD 1840-5210 BC

      Pearson, Gordon W.; Pilcher, J. R.; Baillie, M. G. L.; Corbett, D. M.; Qua, F. (American Journal of Science, 1986-01-01)
      High-precision measurement of dendrochronologically dated Irish oak at bidecade/decade intervals has continued in the Belfast laboratory, extending the 14C data base from ca AD 1840 to 5210 Bc. The dendrochronology is now considered absolute (see Belfast dendrochronology this conference) (Brown et al, 1986) and a continuous detailed curve is presented, showing the natural variations in the atmospheric concentration of 14C over >7000 years. Each data point has a precision of <2.50 per mil, and some 4500 years have now been compared with Seattle, giving excellent agreement. Discussion of this data base and the justification of the claimed accuracy is given together with a comparison of other chronologies. Some of the advantages and limitations of the above are discussed.
    • High-Precision Calibration of the Radiocarbon Time Scale, 3930-3230 Cal BC

      De Jong, A. F. M.; Becker, Bernd; Mook, W. G. (American Journal of Science, 1986-01-01)
    • Illinois State Geological Survey Radiocarbon Dates VIII

      Liu, Chao-Li; Riley, Kerry M.; Coleman, Dennis D. (American Journal of Science, 1986-01-01)
    • Increase of 14C Activity of Dissolved Inorganic Carbon Along a River Course

      Srdoč, Dušan; Krajcar-Bronić, Ines; Horvatinčić, Nada; Obelić, Bogomil (American Journal of Science, 1986-01-01)
      Results of measurements for 3 years (1981-1983) of 14C activity of dissolved inorganic carbon (DIC) in water samples from the Korana River, as well as that of recent tufa and aquatic plants, showed that 14C concentration increases from karst spring to the estuary. A model describing the increase of 14C activity was developed assuming that the increase is due to the exchange of the dissolved CO2 in stream water with atmospheric CO2 and to dissolution of CO2 from the decay of organic material and root respiration. It is possible to distinguish these two contributions by measuring the delta-13C values of DIC in water. As expected, our data show that the exchange process between atmospheric CO2 and DIC dominates at rapids and waterfalls, while biologic contribution is much higher in lakes and along the lowland flow of the Korana River. Agreement between the calculated and the measured activities supports the proposed mechanisms of chemical and isotopic exchanges in stream waters.
    • Institut Royal du Patrimoine Artistique Radiocarbon Dates XI

      Dauchot-Dehon, Michele; Van Strydonck, Mark; Heylen, Jon (American Journal of Science, 1986-01-01)
    • Köln Radiocarbon Dates III

      Schulte im Walde, T.; Freundlich, J. C.; Schwabedissen, Hermann; Taute, Wolfgang (American Journal of Science, 1986-01-01)
    • Lódź Radiocarbon Dates II

      Kanwiszer, Andrzej; Trzeciak, Pawel (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.
    • 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.