chemistry

Suess effect

Suess effect is a chemistry topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Suess effect rather than just read about it. In short: The Suess effect is a 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 contains no 14CO2 and is depleted in 13CO2 relative to CO2 in the atmosphere and carbon in the upper ocean and the terrestrial biosphere. It was discovered by and is named for the Austrian chemist Hans Suess, who noted the influence…

Key takeaways

Suess effect belongs to chemistry; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Suess effect to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Suess effect from memory before moving on to harder problems.

Reference excerpt

The Suess effect is a 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 contains no 14CO2 and is depleted in 13CO2 relative to CO2 in the atmosphere and carbon in the upper ocean and the terrestrial biosphere. It was discovered by and 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 relative to 12CO2. The concept was later extended to dilution of 13CO2 and to other reservoirs of carbon such as the oceans and soils, again relative to 12C. Although the ratio of atmospheric 14CO2 to 12CO2 decreased over the industrial era (prior to atmospheric testing of nuclear weapons, commencing about 1950), because of the increase, due to fossil fuel emissions, in the amount of atmospheric CO2 over this period, roughly 1850 to 1950, the amount of atmospheric 14CO2 actually increased over this period.

Carbon isotopes Carbon has three naturally occurring isotopes. About 99% of carbon on Earth is carbon-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; a large amount was produced in 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 nearly 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. This effect is the basis of radiocarbon dating, with the provision that mass-dependent fractionation and the decrease in 14C due to radioactive decay are accounted for. Photosynthetically fixed carbon in terrestrial plants is depleted in 13C compared to atmospheric CO2. This fractionation of carbon isotopes is caused by kinetic isotope effects and mass dependence of CO2 diffusivity. The overall effect 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.

See also Environmental isotopes Bomb pulse

References

Further reading Cabaneiro, A.; Fernandez, I. (October 2015). "Disclosing biome sensitivity to atmospheric changes: Stable C isotope ecophysiological dependences during photosynthetic CO2 uptake in Maritime pine and Scots pine ecosystems from southwestern Europe". Environmental Technology & Innovation. 4: 52–61. Bibcode:2015EnvTI...4...52C. doi:10.1016/j.eti.2015.04.007. (a 25-year-long dendrochronological study (1978–2002) using stable C isotope ratio mass spectrometry in growth rings of perennial trees from the Southern Atlantic Europe that explores the Suess Effect-ecosystem relationships to examine the biome sensitivity to 13C-CO2 atmospheric changes) Suess, H. E. (September 1955). "Radiocarbon Concentration in Modern Wood". Science. 122 (3166): 415–417. Bibcode:1955Sci...122..415S. doi:10.1126/science.122.3166.415-a. S2CID 177102578. (in Northern hemisphere) Lerman, J. C.; Mook, Wim; Vogel, J. C. (1970). Olsson, Ingrid U. (ed.). Radiocarbon Variations and Absolute Chronology: Proceedings of the Twelfth Nobel Symposium held at the Institute of Physics at Uppsala University. New York: Wiley. pp. 275–301. LCCN 73115769. (in the Southern Hemisphere)

External links 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

Worked examples

Example 1 — a first encounter with Suess effect

Start with the simplest possible case. Write down what Suess effect claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In chemistry, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Suess effect before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Suess effect ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Suess effect

In research: Suess effect appears in chemistry research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Suess effect in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Suess effect is common in secondary-school and first-year university syllabi. It links to neighbouring topics Geochemistry, Greenhouse gas emissions, Radiocarbon dating, so understanding it makes those chapters shorter.
In everyday life: Look for Suess effect outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study Suess effect in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Suess effect means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Suess effect out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Suess effect in simple terms?

Why does Suess effect matter?

Because it connects several chemistry ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Suess effect?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Suess effect.