• Carbon Exchange Between Atmosphere and Oceans in a Latitude-Dependent Advection-Diffusion Model

      Kratz, Gerhard; Kohlmaier, G. H.; Siré, E. O.; Fischbach, Ursula; Broehl, Horst (American Journal of Science, 1983-01-01)
      Marine transport of inorganic and organic carbon is simulated by means of a computer model in which the oceans are divided into a high and low latitude region. Water transport (and with it carbon transport) is reproduced 1) as downwelling of surface waters at low latitudes, and 2) in general, as different depth-dependent turbulent diffusion in both deep-sea regions. The model is calibrated with pre-bomb 14C and validated against perturbations of total carbon, 13C/C- and 14C/C-ratios; it is compatible with carbon release from fossil fuels and from biogenic sources.
    • Distribution of Gaseous 12CO2, 13CO2, and 14CO2 in the Sub-Soil Unsaturated Zone of the Western US Great Plains

      Thorstenson, D. C.; Weeks, E. P.; Haas, Herbert; Fisher, D. W. (American Journal of Science, 1983-01-01)
      Data on the depth distribution of the major atmospheric gases and the abundance of gaseous 12CO2, 13CO2, and 14CO2 in the subsoil unsaturated zone have been obtained from several sites in the western Great Plains of the United States. Sample profiles range from land surface to depths of 50m. Although each site must be considered on an individual basis, several general statements can be made regarding the profiles. 1) Diffusion of these gaseous molecules through the unsaturated zone is an important transport mechanism. 2) As predicted by diffusion theory, depth profiles of the various isotopic species of CO2 differ substantially from one another, depending on individual sources and sinks such as root respiration and oxidation of organic carbon at depth. 3) In general, post-bomb (> 100% modern) 14C activities are not observed in the deep unsaturated zone, in contrast to diffusion model predictions. 4) In spite of generally decreasing 14C activities with depth, absolute partial pressures of 14CO2 in the subsoil unsaturated zone are 1-2 orders of magnitude higher than the partial pressure of 14CO2 in the atmosphere.
    • 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)