• 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.
    • 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.
    • The Use of Natural and Anthropogenic 14C to Investigate the Dynamics of Soil Organic Carbon

      O'Brien, Bernard John (American Journal of Science, 1986-01-01)
      Radiocarbon has been measured in two soil profiles, one of which has been covered by a building since 1956. A comparison of the Delta-14C values in horizons of each profile gives an estimate of the total input of atom bomb 14C into the soil profile. From the Delta-14C and carbon density profile data, the carbon input rates, respiration rates, and diffusivity are calculated. The lack of vegetation on one soil affects the mobility and the respiration rate of the soil carbon in that soil. The data from this soil profile are also used to check the assumption, used in previous analyses, that there is a uniform distribution of "old" carbon down the soil profile. The input rate, turnover time, and diffusivity parameters determined from the Delta-14C profiles in these soils are compared with other published data on pasture and forest soils.
    • Thin Layer delta-13C and Delta-14C Monitoring of "Lessive" Soil Profiles

      Becker-Heidmann, Peter; Scharpenseel, Hans-Wilhelm (American Journal of Science, 1986-01-01)
      The natural 14C and 13C content of soil organic matter and their dependence on depth for two Alfisols are presented. This soil type which covers a large area of the earth's surface is characterized by clay migration processes ("Lessivé"). The samples were taken as successive horizontal layers of 2cm depth from an area of ca 1 m2 size as deep as the C content allows 14C analysis. The minima of the D14C distribution decrease with depth, while the maxima increase in the upper, leached horizon (A1) due to bomb 14C and decrease in the lower, clay illuviated (Bt). delta-13C indicates proceeding decomposition in Al and protection of carbon, probably due to the formation of clay humus complexes in Bt. delta-13C values were also used for age correction of the 14C data due to isotopic fractionation. The D14C and delta-3C depth distributions are characterized by sharp peaks at the boundaries of the horizons, probably caused by the influence of textural changes on the transport of C with percolating water.
    • Trends of 13C/12C Ratios in Pinyon Tree Rings of the American Southwest and the Global Carbon Cycle

      Leavitt, S. W.; Long, Austin (American Journal of Science, 1986-01-01)
      An accurate atmospheric 13C/12C chronology can provide important constraints to models of the global carbon cycle. Trees accumulate carbon from atmospheric CO2 into growth rings and offer potential for 13C/12C reconstructions, but results have not been reproducible. This paper presents 5 degree C curves from 5 sites, representing 20 pinyon (Pinus edulis) trees, where cores of 4 trees from each site have been pooled into a composite sample. Isotopic analysis of cellulose in 5-yr ring groups produces curves with a general trend of decreasing 5 degree C after 1800, but with pronounced short-term fluctuations superimposed upon the trend. Evidence indicates the fluctuations are strongly related to moisture availability (drought). A mean curve of the 5 delta-13C chronologies from which the fossil-fuel component is subtracted suggests a substantial biospheric CO2 contribution to the atmosphere since 1800.