Suess effect



The Suess effect is dilution of the atmospheric concentrations of heavy isotopes of carbon (13C and 14C) by the admixture of large amounts of fossil-fuel derived CO2, which is depleted in 13CO2 and does not contain any 14CO2.[1] It is named for the Austrian chemist radiocarbon dating. More recently, the Suess effect has been used in studies of climate change. The term originally referred only to dilution of atmospheric 14CO2. The concept was later extended to dilution of 13CO2 and to other reservoirs of carbon such as the oceans and soils.[3]

Carbon isotopes

Carbon has three naturally occurring proton in 14N. Minuscule amounts of 14C are produced by other radioactive processes, and a significant amount was released into the atmosphere during nuclear testing before the Limited Test Ban Treaty. Natural 14C production and hence atmospheric concentration varies only slightly over time.

Plants take up 14C by fixing atmospheric carbon through radiocarbon dating.

CAM plants vary between the values observed for C3 and C4 plants. In addition, most fossil fuels originate from C3 biological material produced tens to hundreds of millions of years ago; C4 plants did not become common until about 6 to 8 million years ago, and although CAM photosynthesis is present in modern relatives of the Lepidodendrales of the Carboniferous lowland forests, even if these plants also had CAM photosynthesis, they were not a major component of the total biomass.

Fossil fuels such as coal and oil are made primarily of plant material that was deposited millions of years ago. This period of time equates to thousands of half-lives of 14C, so essentially all of the 14C in fossil fuels has decayed. Fossil fuels also are depleted in 13C relative to the atmosphere, because they were originally formed from living organisms. Therefore, the carbon from fossil fuels that is returned to the atmosphere through combustion is depleted in both 13C and 14C compared to atmospheric carbon dioxide.

See also

  • See articles about environmental isotopes.

and original studies of the Suess effect

  • in the Northern Hemisphere: Suess, H. E. Science 122, 415 (1955).
  • in the Southern Hemisphere: Lerman, J. C., Mook, W. G. & Vogel, J. C. in Radiocarbon Variations and Absolute Chronology (ed. Olsson, I. U.) 275−301 (Wiley, New York, 1970).

References

  1. ^ P.P. Tans, A.F.M. de Jong & W.G. Mook (30 August 1979). "Natural atmospheric 14C variation and the Suess effect". Nature 280: 826-828. doi:10.1038/280826a0. Retrieved on 2007-10-19.
  2. ^ CARD: What is the Suess effect?. Canadian Archaeological Radioactive Database. Retrieved on 2007-10-19.
  3. ^ Keeling, C.D. (1979). "The Suess effect: 13Carbon-14Carbon interrelations.". Environment International 2: 229-300.
 
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