Suess effect
Encyclopedia
The Suess effect is change in the ratio 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 contains no 14CO2. It is named for the Austrian chemist Hans Suess
, who noted the influence of this effect on the accuracy of 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.
-12 (12C
), about 1% is carbon-13 (13C
), and a trace amount is carbon-14 (14C
). The 12C and 13C isotopes are stable, while 14C decays radioactively to nitrogen
-14 (14N) with a half life of 5730 years. 14C on Earth is produced nearly exclusively by the interaction of cosmic radiation with the upper atmosphere. A 14C atom is created when a thermal neutron
displaces a 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 photosynthesis
. Animals then take 14C into their bodies when they consume plants (or consume other animals that consume plants). Thus, living plants and animals have the same ratio of 14C to 12C as the atmospheric CO2. Once organisms die they stop exchanging carbon with the atmosphere, and thus no longer take up new 14C. Radioactive decay then gradually depletes the 14C in the organism. This effect is the basis of radiocarbon dating
.
Photosynthetically
fixed carbon in terrestrial plants is depleted in 13C compared to atmospheric CO2. This depletion is slight in C4
plants but much greater in C3
plants which form the bulk of terrestrial biomass worldwide. Depletion in 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.
Hans Suess
Hans Eduard Suess was an Austrian physical chemist and nuclear physicist. He was a grandson of the Austrian geologist Eduard SuessSuess earned his Ph.D. in chemistry from the University of Vienna in 1935...
, who noted the influence of this effect on the accuracy of radiocarbon dating
Radiocarbon dating
Radiocarbon dating is a radiometric dating method that uses the naturally occurring radioisotope carbon-14 to estimate the age of carbon-bearing materials up to about 58,000 to 62,000 years. Raw, i.e. uncalibrated, radiocarbon ages are usually reported in radiocarbon years "Before Present" ,...
. More recently, the Suess effect has been used in studies of climate change
Climate change
Climate change is a significant and lasting change in the statistical distribution of weather patterns over periods ranging from decades to millions of years. It may be a change in average weather conditions or the distribution of events around that average...
. 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.
Carbon isotopes
Carbon has three naturally occurring isotopes. About 99% of carbon on Earth is carbonCarbon
Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...
-12 (12C
Carbon-12
Carbon-12 is the more abundant of the two stable isotopes of the element carbon, accounting for 98.89% of carbon; it contains 6 protons, 6 neutrons, and 6 electrons....
), about 1% is carbon-13 (13C
Carbon-13
Carbon-13 is a natural, stable isotope of carbon and one of the environmental isotopes. It makes up about 1.1% of all natural carbon on Earth.- Detection by mass spectrometry :...
), and a trace amount is carbon-14 (14C
Carbon-14
Carbon-14, 14C, or radiocarbon, is a radioactive isotope of carbon with a nucleus containing 6 protons and 8 neutrons. Its presence in organic materials is the basis of the radiocarbon dating method pioneered by Willard Libby and colleagues , to date archaeological, geological, and hydrogeological...
). The 12C and 13C isotopes are stable, while 14C decays radioactively to nitrogen
Nitrogen
Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...
-14 (14N) with a half life of 5730 years. 14C on Earth is produced nearly exclusively by the interaction of cosmic radiation with the upper atmosphere. A 14C atom is created when a thermal neutron
Neutron temperature
The neutron detection temperature, also called the neutron energy, indicates a free neutron's kinetic energy, usually given in electron volts. The term temperature is used, since hot, thermal and cold neutrons are moderated in a medium with a certain temperature. The neutron energy distribution is...
displaces a proton
Proton
The proton is a subatomic particle with the symbol or and a positive electric charge of 1 elementary charge. One or more protons are present in the nucleus of each atom, along with neutrons. The number of protons in each atom is its atomic number....
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 photosynthesis
Photosynthesis
Photosynthesis is a chemical process that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight. Photosynthesis occurs in plants, algae, and many species of bacteria, but not in archaea. Photosynthetic organisms are called photoautotrophs, since they can...
. Animals then take 14C into their bodies when they consume plants (or consume other animals that consume plants). Thus, living plants and animals have the same ratio of 14C to 12C as the atmospheric CO2. Once organisms die they stop exchanging carbon with the atmosphere, and thus no longer take up new 14C. Radioactive decay then gradually depletes the 14C in the organism. This effect is the basis of radiocarbon dating
Radiocarbon dating
Radiocarbon dating is a radiometric dating method that uses the naturally occurring radioisotope carbon-14 to estimate the age of carbon-bearing materials up to about 58,000 to 62,000 years. Raw, i.e. uncalibrated, radiocarbon ages are usually reported in radiocarbon years "Before Present" ,...
.
Photosynthetically
Photosynthesis
Photosynthesis is a chemical process that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight. Photosynthesis occurs in plants, algae, and many species of bacteria, but not in archaea. Photosynthetic organisms are called photoautotrophs, since they can...
fixed carbon in terrestrial plants is depleted in 13C compared to atmospheric CO2. This depletion is slight in C4
C4 carbon fixation
C4 carbon fixation is one of three biochemical mechanisms, along with and CAM photosynthesis, used in carbon fixation. It is named for the 4-carbon molecule present in the first product of carbon fixation in these plants, in contrast to the 3-carbon molecule products in plants. fixation is an...
plants but much greater in C3
C3 carbon fixation
carbon fixation is a metabolic pathway for carbon fixation in photosynthesis. This process converts carbon dioxide and ribulose bisphosphate into 3-phosphoglycerate through the following reaction:...
plants which form the bulk of terrestrial biomass worldwide. Depletion in CAM
Crassulacean acid metabolism
Crassulacean acid metabolism, also known as CAM photosynthesis, is a carbon fixation pathway that evolved in some plants as an adaptation to arid conditions. The stomata in the leaves remain shut during the day to reduce evapotranspiration, but open at night to collect carbon dioxide...
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
Lepidodendron
Lepidodendron is an extinct genus of primitive, vascular, arborescent plant related to the Lycopsids . It was part of the coal forest flora. They sometimes reached heights of over , and the trunks were often over in diameter, and thrived during the Carboniferous period...
of the Carboniferous
Carboniferous
The Carboniferous is a geologic period and system that extends from the end of the Devonian Period, about 359.2 ± 2.5 Mya , to the beginning of the Permian Period, about 299.0 ± 0.8 Mya . The name is derived from the Latin word for coal, carbo. Carboniferous means "coal-bearing"...
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
Coal
Coal is a combustible black or brownish-black sedimentary rock usually occurring in rock strata in layers or veins called coal beds or coal seams. The harder forms, such as anthracite coal, can be regarded as metamorphic rock because of later exposure to elevated temperature and pressure...
and oil
Petroleum
Petroleum or crude oil is a naturally occurring, flammable liquid consisting of a complex mixture of hydrocarbons of various molecular weights and other liquid organic compounds, that are found in geologic formations beneath the Earth's surface. Petroleum is recovered mostly through oil drilling...
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 isotopesEnvironmental isotopesThe environmental isotopes are a subset of the isotopes, both stable and radioactive, which are the object of Isotope geochemistry.The most used environmental isotopes are:* deuterium* tritium* carbon-13* carbon-14* nitrogen-15* oxygen-18...
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).
External links
Note: Some, if not all, of these are only temporary until they can become proper references.- An anomalous Suess effect above Europe
- Magnitude and Origin of the Anthropogenic CO2 Increase and 13C Suess Effect in the Nordic Seas Since 1981
- Are arable soils of urban areas influenced by the atmospheric Suess-Effect?
- The need to correct for the Suess effect in the application of δ13C in sediment of autotrophic Lake Tanganyika, as a productivity proxy in the Anthropocene