Artificial carbon-14, a tracer for carbon in the atmosphere and biosphere

Harkness, Douglas D. (1970) Artificial carbon-14, a tracer for carbon in the atmosphere and biosphere. PhD thesis, University of Glasgow.

Abstract

Variations in the steady-state concentrations of natural 14C in the atmosphere, biosphere, and oceans stimulated the application of this isotope as a tracer for the transport of carbon in these various reservoirs. Unfortunately the scope of these early studies was limited by the small differences in the concentrations of natural 14C in the geochemical carbon cycle. In recent years, however, the dispersion of artificial 14C, introduced into the atmosphere during nuclear weapons tests, has presented a unique opportunity for detailed studies of carbon transport. Further importance was attached to these investigations since artificial C constitutes a potential health hazard to mankind. In this research temporal variations in the distribution of artificial 'bomb' 14C in the atmosphere and biosphere have been studied through analysis of atmospheric CO2, food chain, and human tissue samples. The data have been used in an examination of the pathways for CO2 transport in the atmosphere and the rates at which CO2 is transferred to the biosphere and oceans. The temporal variations in the concentration of 14CO2 in air suggest that diffusion processes are predominant in atmospheric transport, particularly in the stratosphere. The mixing time for 14CO2 throughout the atmosphere is comparable with the mean life of a CO2 molecule in the atmosphere before transfer to the ocean viz., 10 to 15 years. During the past decade the concentrations of 14C in man have shown significant differences from those in the contemporary atmosphere. This is best explained by the finite times required for the passage of 14C through the food chain and the selective nature of the human diet. The results of this study suggest that approximately 100 years will pass before the present inventory of artificial C becomes uniformly distributed throughout the dynamic carbon cycle. Due to the release of 14C-free CO2 by the combustion of fossil fuels (the Suess effect) it seems likely, however, that 14C concentrations in the atmosphere and biosphere will attain pre-bomb levels by the end of this century.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Subjects: Q Science > QD Chemistry
• Colleges/Schools: College of Science and Engineering
• Date of Award: 1970
• Depositing User: Enlighten Team
• Unique ID: glathesis:1970-78539
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 28 Feb 2020 12:09
• Last Modified: 05 Oct 2023 13:01
• Thesis DOI: 10.5525/gla.thesis.78539
• URI: https://theses.gla.ac.uk/id/eprint/78539