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144-681: There are three naturally occurring isotopes of carbon on Earth: carbon-12 (C), which makes up 99% of all carbon on Earth; carbon-13 (C), which makes up 1%; and carbon-14 (C), which occurs in trace amounts, making up about 1-1.5 atoms per 10 atoms of carbon in the atmosphere. C and C are both stable; C is unstable, with half-life 5700 ± 30 years. Carbon-14 has a specific activity of 62.4 mCi/mmol (2.31 GBq/mmol), or 164.9 GBq/g. Carbon-14 decays into nitrogen-14 ( N ) through beta decay . A gram of carbon containing 1 atom of carbon-14 per 10 atoms, emits ~0.2 beta (β) particles per second. The primary natural source of carbon-14 on Earth

288-455: A = m 1 x 1 + m 2 x 2 + . . . + m N x N {\displaystyle {\overline {m}}_{a}=m_{1}x_{1}+m_{2}x_{2}+...+m_{N}x_{N}} where m 1 , m 2 , ..., m N are the atomic masses of each individual isotope, and x 1 , ..., x N are the relative abundances of these isotopes. Several applications exist that capitalize on

432-511: A chemical symbol is used, e.g. "C" for carbon, standard notation (now known as "AZE notation" because A is the mass number , Z the atomic number , and E for element ) is to indicate the mass number (number of nucleons) with a superscript at the upper left of the chemical symbol and to indicate the atomic number with a subscript at the lower left (e.g. 2 He , 2 He , 6 C , 6 C , 92 U , and 92 U ). Because

576-505: A 1913 suggestion to the British chemist Frederick Soddy , who popularized the term. The number of protons within the atom's nucleus is called its atomic number and is equal to the number of electrons in the neutral (non-ionized) atom. Each atomic number identifies a specific element, but not the isotope; an atom of a given element may have a wide range in its number of neutrons . The number of nucleons (both protons and neutrons) in

720-481: A N(n,p)C reaction, direct uranium decay (though reported measured ratios of C/U in uranium-bearing ores would imply roughly 1 uranium atom for every two carbon atoms in order to cause the C/C ratio, measured to be on the order of 10), or other unknown secondary sources of C production. The presence of C in the isotopic signature of a sample of carbonaceous material possibly indicates its contamination by biogenic sources or

864-604: A consequence of changes in physical and chemical compositions. The change in soil strongly affects the sensitive vegetation and forest die-off is common. The short-term effect is a decrease in biodiversity but the long-term effect, since these encroachments are hard to reverse, is a loss of habitat. Poor knowledge about peatlands' sensitive hydrology and lack of nutrients often lead to failing plantations, resulting in increasing pressure on remaining peatlands. Tropical peatland vegetation varies with climate and location. Three different characterizations are mangrove woodlands present in

1008-522: A direct comparison of carbon-14 levels in a sample, with tree ring or cave-deposit C levels of a known age, then gives the wood or animal sample age-since-formation. Radiocarbon is also used to detect disturbance in natural ecosystems; for example, in peatland landscapes, radiocarbon can indicate that carbon which was previously stored in organic soils is being released due to land clearance or climate change. Cosmogenic nuclides are also used as proxy data to characterize cosmic particle and solar activity of

1152-505: A double pairing of 2 protons and 2 neutrons prevents any nuclides containing five ( 2 He , 3 Li ) or eight ( 4 Be ) nucleons from existing long enough to serve as platforms for the buildup of heavier elements via nuclear fusion in stars (see triple alpha process ). Only five stable nuclides contain both an odd number of protons and an odd number of neutrons. The first four "odd-odd" nuclides occur in low mass nuclides, for which changing

1296-419: A given element all have the same number of electrons and share a similar electronic structure. Because the chemical behaviour of an atom is largely determined by its electronic structure, different isotopes exhibit nearly identical chemical behaviour. The main exception to this is the kinetic isotope effect : due to their larger masses, heavier isotopes tend to react somewhat more slowly than lighter isotopes of

1440-486: A given element have similar chemical properties, they have different atomic masses and physical properties. The term isotope is derived from the Greek roots isos ( ἴσος "equal") and topos ( τόπος "place"), meaning "the same place"; thus, the meaning behind the name is that different isotopes of a single element occupy the same position on the periodic table . It was coined by Scottish doctor and writer Margaret Todd in

1584-407: A glowing patch on the plate at the point it struck. Thomson observed two separate parabolic patches of light on the photographic plate (see image), which suggested two species of nuclei with different mass-to-charge ratios. He wrote "There can, therefore, I think, be little doubt that what has been called neon is not a simple gas but a mixture of two gases, one of which has an atomic weight about 20 and

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1728-687: A greater carbon sequestration capacity. The carbon sequestration abilities of wetlands can be improved through restoration and protection strategies, but it takes several decades for these restored ecosystems to become comparable in carbon storage to peatlands and other forms of natural wetlands. Studies highlight the critical role of peatlands in biodiversity conservation and hydrological stability. These ecosystems are unique habitats for diverse species , including specific insects and amphibians , and act as natural water reservoirs , releasing water during dry periods to sustain nearby freshwater ecosystems and agriculture . The exchange of carbon between

1872-424: A net cooling effect on the atmosphere. The water table position of a peatland is the main control of its carbon release to the atmosphere. When the water table rises after a rainstorm, the peat and its microbes are submerged under water inhibiting access to oxygen, reducing CO 2 release via respiration. Carbon dioxide release increases when the water table falls lower, such as during a drought, as this increases

2016-468: A nonoptimal number of neutrons or protons decay by beta decay (including positron emission ), electron capture , or other less common decay modes such as spontaneous fission and cluster decay . Most stable nuclides are even-proton-even-neutron, where all numbers Z , N , and A are even. The odd- A stable nuclides are divided (roughly evenly) into odd-proton-even-neutron, and even-proton-odd-neutron nuclides. Stable odd-proton-odd-neutron nuclides are

2160-439: A nuclear reactor) are summarized in the table. Another source of carbon-14 is cluster decay branches from traces of naturally occurring isotopes of radium , though this decay mode has a branching ratio on the order of 10 relative to alpha decay , so radiogenic carbon-14 is extremely rare. The above-ground nuclear tests that occurred in several countries in 1955-1980 (see List of nuclear tests ) dramatically increased

2304-427: A nucleus. As the number of protons increases, so does the ratio of neutrons to protons necessary to ensure a stable nucleus (see graph at right). For example, although the neutron:proton ratio of 2 He is 1:2, the neutron:proton ratio of 92 U is greater than 3:2. A number of lighter elements have stable nuclides with the ratio 1:1 ( Z = N ). The nuclide 20 Ca (calcium-40)

2448-450: A peatland can be dry). A peatland that is still capable of forming new peat is called a mire , while drained and converted peatlands might still have a peat layer but are not considered mires as the formation of new peat has ceased. There are two types of mire: bog and fen . A bog is a mire that, due to its raised location relative to the surrounding landscape, obtains all its water solely from precipitation ( ombrotrophic ). A fen

2592-405: A product of stellar nucleosynthesis or another type of nucleosynthesis such as cosmic ray spallation , and have persisted down to the present because their rate of decay is very slow (e.g. uranium-238 and potassium-40 ). Post-primordial isotopes were created by cosmic ray bombardment as cosmogenic nuclides (e.g., tritium , carbon-14 ), or by the decay of a radioactive primordial isotope to

2736-506: A proton to a neutron or vice versa would lead to a very lopsided proton-neutron ratio ( 1 H , 3 Li , 5 B , and 7 N ; spins 1, 1, 3, 1). The only other entirely "stable" odd-odd nuclide, 73 Ta (spin 9), is thought to be the rarest of the 251 stable nuclides, and is the only primordial nuclear isomer , which has not yet been observed to decay despite experimental attempts. Many odd-odd radionuclides (such as

2880-419: A quarter of global peatland area. This involves cutting drainage ditches to lower the water table with the intended purpose of enhancing the productivity of forest cover or for use as pasture or cropland. Agricultural uses for mires include the use of natural vegetation for hay crop or grazing, or the cultivation of crops on a modified surface. In addition, the commercial extraction of peat for energy production

3024-478: A radioactive radiogenic nuclide daughter (e.g. uranium to radium ). A few isotopes are naturally synthesized as nucleogenic nuclides, by some other natural nuclear reaction , such as when neutrons from natural nuclear fission are absorbed by another atom. As discussed above, only 80 elements have any stable isotopes, and 26 of these have only one stable isotope. Thus, about two-thirds of stable elements occur naturally on Earth in multiple stable isotopes, with

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3168-649: A result of developing land use and agriculture. During the El Niño -event in 1997–1998 more than 24,400 km of peatland was lost to fires in Indonesia alone from which 10,000 km was burnt in Kalimantan and Sumatra. The output of CO 2 was estimated to 0.81–2.57 Gt, equal to 13–40% of that year's global output from fossil fuel burning. Indonesia is now considered the third-biggest contributor to global CO 2 emissions, caused primarily by these fires. With

3312-561: A severe fire can release up to 4,000 t of CO 2 /ha. Burning events in tropical peatlands are becoming more frequent due to large-scale drainage and land clearance and in the past ten years, more than 2 million hectares was burnt in Southeast Asia alone. These fires last typically for 1–3 months and release large amounts of CO 2 . Indonesia is one of the countries suffering from peatland fires, especially during years with ENSO -related drought, an increasing problem since 1982 as

3456-424: A single stable isotope (of these, 19 are so-called mononuclidic elements , having a single primordial stable isotope that dominates and fixes the atomic weight of the natural element to high precision; 3 radioactive mononuclidic elements occur as well). In total, there are 251 nuclides that have not been observed to decay. For the 80 elements that have one or more stable isotopes, the average number of stable isotopes

3600-402: A slower rate to form CO 2 , radioactive carbon dioxide . The gas mixes rapidly and becomes evenly distributed throughout the atmosphere (the mixing timescale on the order of weeks). Carbon dioxide also dissolves in water and thus permeates the oceans , but at a slower rate. The atmospheric half-life for removal of CO 2 has been estimated at roughly 12 to 16 years in

3744-464: A small atmospheric carbon dioxide sink through the photosynthesis of peat vegetation, which outweighs their release of greenhouse gases. On the other hand, most mires are generally net emitters of methane and nitrous oxide. Due to the continued CO 2 sequestration over millennia, and because of the longer atmospheric lifespan of the CO 2 molecules compared with methane and nitrous oxide, peatlands have had

3888-497: A stable (non-radioactive) element was found by J. J. Thomson in 1912 as part of his exploration into the composition of canal rays (positive ions). Thomson channelled streams of neon ions through parallel magnetic and electric fields, measured their deflection by placing a photographic plate in their path, and computed their mass to charge ratio using a method that became known as the Thomson's parabola method. Each stream created

4032-477: A substantial amount of organic matter, where humic acid dominates. Humic materials are able to store very large amounts of water, making them an essential component in the peat environment, contributing to an increased amount of carbon storage due to the resulting anaerobic condition. If the peatland is dried from long-term cultivation and agricultural use, it will lower the water table and the increased aeration will subsequently release carbon. Upon extreme drying,

4176-622: A total 30 + 2(9) = 48 stable odd-even isotopes. There are also five primordial long-lived radioactive odd-even isotopes, 37 Rb , 49 In , 75 Re , 63 Eu , and 83 Bi . The last two were only recently found to decay, with half-lives greater than 10 years. Actinides with odd neutron number are generally fissile (with thermal neutrons ), whereas those with even neutron number are generally not, though they are fissionable with fast neutrons . All observationally stable odd-odd nuclides have nonzero integer spin. This

4320-490: A warming climate these burnings are expected to increase in intensity and number. This is a result of a dry climate together with an extensive rice farming project, called the Mega Rice Project , started in the 1990s, which converted 1 Mha of peatlands to rice paddies . Forest and land was cleared by burning and 4000 km of channels drained the area. Drought and acidification of the lands led to bad harvest and

4464-433: A way that preserves the hydrological state of a mire, the anthropogenic use of mires' resources can avoid significant greenhouse gas emissions . However, continued drainage will result in increased release of carbon, contributing to global warming. As of 2016, it was estimated that drained peatlands account for around 10% of all greenhouse gas emissions from agriculture and forestry. Palm oil has increasingly become one of

Carbon-14 - Misplaced Pages Continue

4608-681: Is aluminium-26 , which is not naturally found on Earth but is found in abundance on an astronomical scale. The tabulated atomic masses of elements are averages that account for the presence of multiple isotopes with different masses. Before the discovery of isotopes, empirically determined noninteger values of atomic mass confounded scientists. For example, a sample of chlorine contains 75.8% chlorine-35 and 24.2% chlorine-37 , giving an average atomic mass of 35.5 atomic mass units . According to generally accepted cosmology theory , only isotopes of hydrogen and helium, traces of some isotopes of lithium and beryllium, and perhaps some boron, were created at

4752-545: Is blanket bog where precipitation is very high i.e., in maritime climates inland near the coasts of the north-east and south Pacific, and the north-west and north-east Atlantic. In the sub-tropics, mires are rare and restricted to the wettest areas. Mires can be extensive in the tropics, typically underlying tropical rainforest (for example, in Kalimantan , the Congo Basin and Amazon basin ). Tropical peat formation

4896-649: Is cosmic ray action on nitrogen in the atmosphere, and it is therefore a cosmogenic nuclide . However, open-air nuclear testing between 1955 and 1980 contributed to this pool. The different isotopes of carbon do not differ appreciably in their chemical properties. This resemblance is used in chemical and biological research, in a technique called carbon labeling : carbon-14 atoms can be used to replace nonradioactive carbon, in order to trace chemical and biochemical reactions involving carbon atoms from any given organic compound. Carbon-14 undergoes beta decay : By emitting an electron and an electron antineutrino , one of

5040-486: Is 0.05 mm. Radiocarbon dating is a radiometric dating method that uses C to determine the age of carbonaceous materials up to about 60,000 years old. The technique was developed by Willard Libby and his colleagues in 1949 during his tenure as a professor at the University of Chicago . Libby estimated that the radioactivity of exchangeable C would be about 14 decays per minute (dpm) per gram of carbon, and this

5184-547: Is 251/80 ≈ 3.14 isotopes per element. The proton:neutron ratio is not the only factor affecting nuclear stability. It depends also on evenness or oddness of its atomic number Z , neutron number N and, consequently, of their sum, the mass number A . Oddness of both Z and N tends to lower the nuclear binding energy , making odd nuclei, generally, less stable. This remarkable difference of nuclear binding energy between neighbouring nuclei, especially of odd- A isobars , has important consequences: unstable isotopes with

5328-641: Is a radioactive form of carbon, whereas C and C are stable isotopes. There are about 339 naturally occurring nuclides on Earth, of which 286 are primordial nuclides , meaning that they have existed since the Solar System 's formation. Primordial nuclides include 35 nuclides with very long half-lives (over 100 million years) and 251 that are formally considered as " stable nuclides ", because they have not been observed to decay. In most cases, for obvious reasons, if an element has stable isotopes, those isotopes predominate in

5472-456: Is a species of an atom with a specific number of protons and neutrons in the nucleus, for example, carbon-13 with 6 protons and 7 neutrons. The nuclide concept (referring to individual nuclear species) emphasizes nuclear properties over chemical properties, whereas the isotope concept (grouping all atoms of each element) emphasizes chemical over nuclear. The neutron number greatly affects nuclear properties, but its effect on chemical properties

5616-435: Is actively forming peat is called a mire . All types of mires share the common characteristic of being saturated with water, at least seasonally with actively forming peat , while having their own ecosystem. Peatlands are the largest natural carbon store on land. Covering around 3 million km globally, they sequester 0.37 gigatons (Gt) of carbon dioxide (CO 2 ) a year. Peat soils store over 600 Gt of carbon, more than

5760-443: Is also generated inside nuclear fuels (some due to transmutation of oxygen in the uranium oxide , but most significantly from transmutation of nitrogen-14 impurities), and if the spent fuel is sent to nuclear reprocessing then the C is released, for example as CO 2 during PUREX . After production in the upper atmosphere, the carbon-14 reacts rapidly to form mostly (about 93%) CO ( carbon monoxide ), which subsequently oxidizes at

5904-663: Is because the single unpaired neutron and unpaired proton have a larger nuclear force attraction to each other if their spins are aligned (producing a total spin of at least 1 unit), instead of anti-aligned. See deuterium for the simplest case of this nuclear behavior. Only 78 Pt , 4 Be , and 7 N have odd neutron number and are the most naturally abundant isotope of their element. Elements are composed either of one nuclide ( mononuclidic elements ), or of more than one naturally occurring isotopes. The unstable (radioactive) isotopes are either primordial or postprimordial. Primordial isotopes were

Carbon-14 - Misplaced Pages Continue

6048-421: Is better known than nuclide and is still sometimes used in contexts in which nuclide might be more appropriate, such as nuclear technology and nuclear medicine . An isotope and/or nuclide is specified by the name of the particular element (this indicates the atomic number) followed by a hyphen and the mass number (e.g. helium-3 , helium-4 , carbon-12 , carbon-14 , uranium-235 and uranium-239 ). When

6192-435: Is denoted with symbols "u" (for unified atomic mass unit) or "Da" (for dalton ). The atomic masses of naturally occurring isotopes of an element determine the standard atomic weight of the element. When the element contains N isotopes, the expression below is applied for the average atomic mass m ¯ a {\displaystyle {\overline {m}}_{a}} : m ¯

6336-411: Is especially prevalent in the tropics. Peatlands release the greenhouse gas methane which has strong global warming potential . However, subtropical wetlands have shown high CO 2 binding per mol of released methane, which is a function that counteracts global warming. Tropical peatlands are suggested to contain about 100 Gt carbon, corresponding to more than 50% of the carbon present as CO 2 in

6480-496: Is estimated to be between the equivalent of 12.4 (best case) to 76.6 t CO 2 /ha (worst case). Tropical peatland converted to palm oil plantation can remain a net source of carbon to the atmosphere after 12 years. In their natural state, peatlands are resistant to fire. Drainage of peatlands for palm oil plantations creates a dry layer of flammable peat. As peat is carbon dense, fires occurring in compromised peatlands release extreme amounts of both carbon dioxide and toxic smoke into

6624-892: Is evidence for an unusually high production rate in AD 774–775 , caused by an extreme solar energetic particle event, the strongest such event to have occurred within the last ten millennia. Another "extraordinarily large" C increase (2%) has been associated with a 5480 BC event, which is unlikely to be a solar energetic particle event. Carbon-14 may also be produced by lightning but in amounts negligible, globally, compared to cosmic ray production. Local effects of cloud-ground discharge through sample residues are unclear, but possibly significant. Carbon-14 can also be produced by other neutron reactions, including in particular C (n,γ)C and O (n,α)C with thermal neutrons , and N (n,d)C and O (n,He)C with fast neutrons . The most notable routes for C production by thermal neutron irradiation of targets (e.g., in

6768-544: Is found in the temperate, boreal and subarctic zones of the Northern Hemisphere. Mires are usually shallow in polar regions because of the slow rate of accumulation of dead organic matter, and often contain permafrost and palsas . Very large swathes of Canada, northern Europe and northern Russia are covered by boreal mires. In temperate zones mires are typically more scattered due to historical drainage and peat extraction, but can cover large areas. One example

6912-402: Is in the oceans. The following inventory of carbon-14 has been given: Many human-made chemicals are derived from fossil fuels (such as petroleum or coal ) in which C is greatly depleted because the age of fossils far exceeds the half-life of C. The relative absence of CO 2 is therefore used to determine the relative contribution (or mixing ratio ) of fossil fuel oxidation to

7056-404: Is intended to imply comparison (like synonyms or isomers ). For example, the nuclides 6 C , 6 C , 6 C are isotopes (nuclides with the same atomic number but different mass numbers ), but 18 Ar , 19 K , 20 Ca are isobars (nuclides with the same mass number ). However, isotope is the older term and so

7200-616: Is known to occur in coastal mangroves as well as in areas of high altitude. Tropical mires largely form where high precipitation is combined with poor conditions for drainage. Tropical mires account for around 11% of peatlands globally (more than half of which can be found in Southeast Asia), and are most commonly found at low altitudes, although they can also be found in mountainous regions, for example in South America, Africa and Papua New Guinea . Indonesia, particularly on

7344-427: Is located on a slope, flat, or in a depression and gets most of its water from the surrounding mineral soil or from groundwater ( minerotrophic ). Thus, while a bog is always acidic and nutrient-poor, a fen may be slightly acidic, neutral, or alkaline, and either nutrient-poor or nutrient-rich. All mires are initially fens when the peat starts to form, and may turn into bogs once the height of the peat layer reaches above

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7488-418: Is negligible for most elements. Even for the lightest elements, whose ratio of neutron number to atomic number varies the most between isotopes, it usually has only a small effect although it matters in some circumstances (for hydrogen, the lightest element, the isotope effect is large enough to affect biology strongly). The term isotopes (originally also isotopic elements , now sometimes isotopic nuclides )

7632-628: Is observationally the heaviest stable nuclide with the same number of neutrons and protons. All stable nuclides heavier than calcium-40 contain more neutrons than protons. Of the 80 elements with a stable isotope, the largest number of stable isotopes observed for any element is ten (for the element tin ). No element has nine or eight stable isotopes. Five elements have seven stable isotopes, eight have six stable isotopes, ten have five stable isotopes, nine have four stable isotopes, five have three stable isotopes, 16 have two stable isotopes (counting 73 Ta as stable), and 26 elements have only

7776-534: Is oxidised by methanotrophs above the water table level. Therefore, changes in water table level influence the size of these methane production and consumption zones. Increased soil temperatures also contribute to increased seasonal methane flux. A study in Alaska found that methane may vary by as much as 300% seasonally with wetter and warmer soil conditions due to climate change. Peatlands are important for studying past climate because they are sensitive to changes in

7920-527: Is oxidised quickly and removed from the atmosphere whereas atmospheric carbon dioxide is continuously absorbed. Throughout the Holocene (the past 12,000 years), peatlands have been persistent terrestrial carbon sinks and have had a net cooling effect, sequestering 5.6 to 38 grams of carbon per square metre per year. On average, it has been estimated that today northern peatlands sequester 20 to 30 grams of carbon per square metre per year. Peatlands insulate

8064-399: Is primarily controlled by climatic conditions such as precipitation and temperature, although terrain relief is a major factor as waterlogging occurs more easily on flatter ground and in basins. Peat formation typically initiates as a paludification of a mineral soil forests, terrestrialisation of lakes, or primary peat formation on bare soils on previously glaciated areas. A peatland that

8208-427: Is small compared to the doses from K (0.39 mSv/year) and radon (variable). C can be used as a radioactive tracer in medicine. In the initial variant of the urea breath test , a diagnostic test for Helicobacter pylori , urea labeled with about 37  kBq (1.0  μCi ) C is fed to a patient (i.e. 37,000 decays per second). In the event of a H. pylori infection, the bacterial urease enzyme breaks down

8352-520: Is still used as the activity of the modern radiocarbon standard . In 1960, Libby was awarded the Nobel Prize in chemistry for this work. One of the frequent uses of the technique is to date organic remains from archaeological sites. Plants fix atmospheric carbon during photosynthesis; so the level of C in plants and animals when they die, roughly equals the level of C in the atmosphere at that time. However, it thereafter decreases exponentially; so

8496-585: Is stored in living plants, dead plants and peat, as well as converted to carbon dioxide and methane. Three main factors give wetlands the ability to sequester and store carbon: high biological productivity, high water table and low decomposition rates. Suitable meteorological and hydrological conditions are necessary to provide an abundant water source for the wetland. Fully water-saturated wetland soils allow anaerobic conditions to manifest, storing carbon but releasing methane. Wetlands make up about 5-8% of Earth's terrestrial land surface but contain about 20-30% of

8640-435: Is the preferred method although more recently, accelerator mass spectrometry has become the method of choice; it counts all the carbon-14 atoms in the sample and not just the few that happen to decay during the measurements; it can therefore be used with much smaller samples (as small as individual plant seeds), and gives results much more quickly. The G-M counting efficiency is estimated to be 3%. The half-distance layer in water

8784-451: Is therefore vulnerable to changes in hydrology or vegetation cover. These peatlands are mostly located in developing regions with impoverished and rapidly growing populations. These lands have become targets for commercial logging , paper pulp production and conversion to plantations through clear-cutting , drainage and burning. Drainage of tropical peatlands alters the hydrology and increases their susceptibility to fire and soil erosion, as

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8928-584: Is widely practiced in Northern European countries, such as Russia, Sweden, Finland, Ireland and the Baltic states . Tropical peatlands comprise 0.25% of Earth's terrestrial land surface but store 3% of all soil and forest carbon stocks. The use of this land by humans, including draining and harvesting of tropical peat forests, results in the emission of large amounts of carbon dioxide into the atmosphere. In addition, fires occurring on peatland dried by

9072-474: The Big Bang , while all other nuclides were synthesized later, in stars and supernovae, and in interactions between energetic particles such as cosmic rays, and previously produced nuclides. (See nucleosynthesis for details of the various processes thought responsible for isotope production.) The respective abundances of isotopes on Earth result from the quantities formed by these processes, their spread through

9216-447: The CNO cycle . The nuclides 3 Li and 5 B are minority isotopes of elements that are themselves rare compared to other light elements, whereas the other six isotopes make up only a tiny percentage of the natural abundance of their elements. 53 stable nuclides have an even number of protons and an odd number of neutrons. They are a minority in comparison to

9360-825: The Girdler sulfide process . Uranium isotopes have been separated in bulk by gas diffusion, gas centrifugation, laser ionization separation, and (in the Manhattan Project ) by a type of production mass spectrometry . Peatland A peatland is a type of wetland whose soils consist of organic matter from decaying plants, forming layers of peat . Peatlands arise because of incomplete decomposition of organic matter, usually litter from vegetation, due to water-logging and subsequent anoxia . Peatlands are unusual landforms that derive mostly from biological rather than physical processes, and can take on characteristic shapes and surface patterning. The formation of peatlands

9504-410: The binding energy of the nucleus (see mass defect ), the slight difference in mass between proton and neutron, and the mass of the electrons associated with the atom, the latter because the electron:nucleon ratio differs among isotopes. The mass number is a dimensionless quantity . The atomic mass, on the other hand, is measured using the atomic mass unit based on the mass of the carbon-12 atom. It

9648-465: The fissile 92 U . Because of their odd neutron numbers, the even-odd nuclides tend to have large neutron capture cross-sections, due to the energy that results from neutron-pairing effects. These stable even-proton odd-neutron nuclides tend to be uncommon by abundance in nature, generally because, to form and enter into primordial abundance, they must have escaped capturing neutrons to form yet other stable even-even isotopes, during both

9792-565: The permafrost in subarctic regions, thus delaying thawing during summer, as well as inducing the formation of permafrost. As the global climate continues to warm, wetlands could become major carbon sources as higher temperatures cause higher carbon dioxide emissions. Compared with untilled cropland, wetlands can sequester around two times the carbon. Carbon sequestration can occur in constructed wetlands as well as natural ones. Estimates of greenhouse gas fluxes from wetlands indicate that natural wetlands have lower fluxes, but man-made wetlands have

9936-436: The residual strong force . Because protons are positively charged, they repel each other. Neutrons, which are electrically neutral, stabilize the nucleus in two ways. Their copresence pushes protons slightly apart, reducing the electrostatic repulsion between the protons, and they exert an attractive nuclear force on each other and on protons. For this reason, one or more neutrons are necessary for two or more protons to bind into

10080-421: The s-process and r-process of neutron capture, during nucleosynthesis in stars . For this reason, only 78 Pt and 4 Be are the most naturally abundant isotopes of their element. 48 stable odd-proton-even-neutron nuclides, stabilized by their paired neutrons, form most of the stable isotopes of the odd-numbered elements; the very few odd-proton-odd-neutron nuclides comprise

10224-541: The urea into ammonia and radioactively-labeled carbon dioxide , which can be detected by low-level counting of the patient's breath. Isotope Isotopes are distinct nuclear species (or nuclides ) of the same chemical element . They have the same atomic number (number of protons in their nuclei ) and position in the periodic table (and hence belong to the same chemical element), but different nucleon numbers ( mass numbers ) due to different numbers of neutrons in their nuclei. While all isotopes of

10368-690: The Central Congo Basin , covering 145,500 km and storing up to 10 kg of carbon. The total area of mires has declined globally due to drainage for agriculture, forestry and peat harvesting. For example, more than 50% of the original European mire area which is more than 300,000 km has been lost. Some of the largest losses have been in Russia, Finland, the Netherlands, the United Kingdom, Poland and Belarus. A catalog of

10512-635: The Northern Hemisphere. Peatlands are estimated to cover around 3% of the globe's surface, although estimating the extent of their cover worldwide is difficult due to the varying accuracy and methodologies of land surveys from many countries. Mires occur wherever conditions are right for peat accumulation: largely where organic matter is constantly waterlogged. Hence the distribution of mires is dependent on topography , climate, parent material, biota and time. The type of mire—bog, fen, marsh or swamp—depends also on each of these factors. The largest accumulation of mires constitutes around 64% of global peatlands and

10656-491: The Northern Hemisphere. The transfer between the ocean shallow layer and the large reservoir of bicarbonates in the ocean depths occurs at a limited rate. In 2009 the activity of C was 238 Bq per kg carbon of fresh terrestrial biomatter, close to the values before atmospheric nuclear testing (226 Bq/kg C; 1950). The inventory of carbon-14 in Earth's biosphere is about 300 megacuries (11  E Bq ), of which most

10800-628: The above-ground nuclear tests of the 1950s and 1960s. Though the extra C generated by those nuclear tests has not disappeared from the atmosphere, oceans and biosphere, it is diluted due to the Suess effect . Carbon-14 is produced in coolant at boiling water reactors (BWRs) and pressurized water reactors (PWRs). It is typically released into the air in the form of carbon dioxide at BWRs, and methane at PWRs. Best practice for nuclear power plant operator management of carbon-14 includes releasing it at night, when plants are not photosynthesizing . Carbon-14

10944-476: The air. These fires add to greenhouse gas emissions while also causing thousands of deaths every year. Decreased biodiversity due to deforestation and drainage makes these ecosystem more vulnerable and less resilient to change. Homogenous ecosystems are at an increased risk to extreme climate conditions and are less likely to recover from fires. Some peatlands are being dried out by climate change . Drainage of peatlands due to climatic factors may also increase

11088-429: The almost integral masses for the two isotopes Cl and Cl. After the discovery of the neutron by James Chadwick in 1932, the ultimate root cause for the existence of isotopes was clarified, that is, the nuclei of different isotopes for a given element have different numbers of neutrons, albeit having the same number of protons. A neutral atom has the same number of electrons as protons. Thus different isotopes of

11232-585: The amount of C in tooth enamel , or the carbon-14 concentration in the lens of the eye. In 2019, Scientific American reported that carbon-14 from nuclear testing has been found in animals from one of the most inaccessible regions on Earth, the Mariana Trench in the Pacific Ocean. The concentration of C in atmospheric CO 2 , reported as the C/C ratio with respect to a standard, has (since about 2022) declined to levels similar to those prior to

11376-422: The amount of C in the atmosphere and subsequently the biosphere; after the tests ended, the atmospheric concentration of the isotope began to decrease, as radioactive CO 2 was fixed into plant and animal tissue, and dissolved in the oceans. One side-effect of the change in atmospheric C is that this has enabled some options (e.g. bomb-pulse dating ) for determining the birth year of an individual, in particular,

11520-454: The atmosphere primarily through the exchange of carbon dioxide , methane and nitrous oxide , and can be damaged by excess nitrogen from agriculture or rainwater. The sequestration of carbon dioxide takes place at the surface via the process of photosynthesis , while losses of carbon dioxide occur through living plants via autotrophic respiration and from the litter and peat via heterotrophic respiration. In their natural state, mires are

11664-463: The atmosphere. Accumulation rates of carbon during the last millennium were close to 40 g C/m /yr. Northern peatlands are associated with boreal and subarctic climates. Northern peatlands were mostly built up during the Holocene after the retreat of Pleistocene glaciers, but in contrast tropical peatlands are much older. Total northern peat carbon stocks are estimated to be 1055 Gt of carbon. Of all northern circumpolar countries, Russia has

11808-463: The atomic number is given by the element symbol, it is common to state only the mass number in the superscript and leave out the atomic number subscript (e.g. He , He , C , C , U , and U ). The letter m (for metastable) is sometimes appended after the mass number to indicate a nuclear isomer , a metastable or energetically excited nuclear state (as opposed to

11952-444: The availability of oxygen to the aerobic microbes thus accelerating peat decomposition. Levels of methane emissions also vary with the water table position and temperature. A water table near the peat surface gives the opportunity for anaerobic microorganisms to flourish. Methanogens are strictly anaerobic organisms and produce methane from organic matter in anoxic conditions below the water table level, while some of that methane

12096-640: The beta decay of actinium-230 forms thorium-230. The term "isotope", Greek for "at the same place", was suggested to Soddy by Margaret Todd , a Scottish physician and family friend, during a conversation in which he explained his ideas to her. He received the 1921 Nobel Prize in Chemistry in part for his work on isotopes. In 1914 T. W. Richards found variations between the atomic weight of lead from different mineral sources, attributable to variations in isotopic composition due to different radioactive origins. The first evidence for multiple isotopes of

12240-505: The carbon stored in all other vegetation types, including forests. This substantial carbon storage represents about 30% of the world's soil carbon , underscoring their critical importance in the global carbon cycle . In their natural state, peatlands provide a range of ecosystem services , including minimising flood risk and erosion, purifying water and regulating climate. Peatlands are under threat by commercial peat harvesting, drainage and conversion for agriculture (notably palm oil in

12384-406: The conversion of organics to carbon dioxide to be released in the atmosphere. Records of past human behaviour and environments can be contained within peatlands. These may take the form of human artefacts, or palaeoecological and geochemical records. Peatlands are used by humans in modern times for a range of purposes, the most dominant being agriculture and forestry, which accounts for around

12528-420: The date of death or fixation can be estimated. The initial C level for the calculation can either be estimated, or else directly compared with known year-by-year data from tree-ring data ( dendrochronology ) up to 10,000 years ago (using overlapping data from live and dead trees in a given area), or else from cave deposits ( speleothems ), back to about 45,000 years before present. A calculation or (more accurately)

12672-548: The decay of radioactive material in surrounding geologic strata. In connection with building the Borexino solar neutrino observatory, petroleum feedstock (for synthesizing the primary scintillant) was obtained with low C content. In the Borexino Counting Test Facility, a C/C ratio of 1.94×10 was determined; probable reactions responsible for varied levels of C in different petroleum reservoirs , and

12816-669: The distant past. Carbon-14 is produced in the upper troposphere and the stratosphere by thermal neutrons absorbed by nitrogen atoms. When cosmic rays enter the atmosphere, they undergo various transformations, including the production of neutrons . The resulting neutrons (n) participate in the following n-p reaction (p is proton ): The highest rate of carbon-14 production takes place at altitudes of 9 to 15 kilometres (30,000 to 49,000 ft) and at high geomagnetic latitudes . The rate of C production can be modeled, yielding values of 16,400 or 18,800 atoms of C per second per square meter of Earth's surface, which agrees with

12960-484: The draining of peat bogs release even more carbon dioxide. The economic value of a tropical peatland was once derived from raw materials, such as wood, bark, resin and latex, the extraction of which did not contribute to large carbon emissions. In Southeast Asia, peatlands are drained and cleared for human use for a variety of reasons, including the production of palm oil and timber for export in primarily developing nations. This releases stored carbon dioxide and preventing

13104-406: The ecosystem can undergo a state shift, turning the mire into a barren land with lower biodiversity and richness. The formation of humic acid occurs during the biogeochemical degradation of vegetation debris, animal residue and degraded segments. The loads of organic matter in the form of humic acid is a source of precursors of coal. Prematurely exposing the organic matter to the atmosphere promotes

13248-500: The elemental abundance found on Earth and in the Solar System. However, in the cases of three elements ( tellurium , indium , and rhenium ) the most abundant isotope found in nature is actually one (or two) extremely long-lived radioisotope(s) of the element, despite these elements having one or more stable isotopes. Theory predicts that many apparently "stable" nuclides are radioactive, with extremely long half-lives (discounting

13392-426: The emission of methane, which is a strong greenhouse gas. However, given the short "lifetime" of methane (12 years), it is often said that methane emissions are unimportant within 300 years compared to carbon sequestration in wetlands. Within that time frame or less, most wetlands become both net carbon and radiative sinks. Hence, peatlands do result in cooling of the Earth's climate over a longer time period as methane

13536-628: The environment and can reveal levels of isotopes , pollutants, macrofossils , metals from the atmosphere and pollen. For example, carbon-14 dating can reveal the age of the peat. The dredging and destruction of a peatland will release the carbon dioxide that could reveal irreplaceable information about the past climatic conditions. Many kinds of microorganisms inhabit peatlands, due to the regular supply of water and abundance of peat forming vegetation. These microorganisms include but are not limited to methanogens , algae, bacteria, zoobenthos , of which Sphagnum species are most abundant. Peat contains

13680-410: The even-even isotopes, which are about 3 times as numerous. Among the 41 even- Z elements that have a stable nuclide, only two elements (argon and cerium) have no even-odd stable nuclides. One element (tin) has three. There are 24 elements that have one even-odd nuclide and 13 that have two odd-even nuclides. Of 35 primordial radionuclides there exist four even-odd nuclides (see table at right), including

13824-486: The galaxy, and the rates of decay for isotopes that are unstable. After the initial coalescence of the Solar System , isotopes were redistributed according to mass, and the isotopic composition of elements varies slightly from planet to planet. This sometimes makes it possible to trace the origin of meteorites . The atomic mass ( m r ) of an isotope (nuclide) is determined mainly by its mass number (i.e. number of nucleons in its nucleus). Small corrections are due to

13968-560: The global carbon budget that can be used to backtrack, but attempts to measure the production time directly in situ were not very successful. Production rates vary because of changes to the cosmic ray flux caused by the heliospheric modulation (solar wind and solar magnetic field), and, of great significance, due to variations in the Earth's magnetic field . Changes in the carbon cycle however can make such effects difficult to isolate and quantify. Occasional spikes may occur; for example, there

14112-401: The ground state of tantalum-180) with comparatively short half-lives are known. Usually, they beta-decay to their nearby even-even isobars that have paired protons and paired neutrons. Of the nine primordial odd-odd nuclides (five stable and four radioactive with long half-lives), only 7 N is the most common isotope of a common element. This is the case because it is a part of

14256-434: The ground surface above the original topography. Mires can reach considerable heights above the underlying mineral soil or bedrock : peat depths of above 10 m have been commonly recorded in temperate regions (many temperate and most boreal mires were removed by ice sheets in the last Ice Age), and above 25 m in tropical regions. When the absolute decay rate of peat in the catotelm (the lower, water-saturated zone of

14400-494: The inflow of groundwater (bringing in supplementary cations) is high. Generally, whenever the inputs of carbon into the soil from dead organic matter exceed the carbon outputs via organic matter decomposition , peat is formed. This occurs due to the anoxic state of water-logged peat, which slows down decomposition. Peat-forming vegetation is typically also recalcitrant (poorly decomposing) due to high lignin and low nutrient content. Topographically , accumulating peat elevates

14544-409: The integers 20 and 22 and that neither is equal to the known molar mass (20.2) of neon gas. This is an example of Aston's whole number rule for isotopic masses, which states that large deviations of elemental molar masses from integers are primarily due to the fact that the element is a mixture of isotopes. Aston similarly showed in 1920 that the molar mass of chlorine (35.45) is a weighted average of

14688-400: The islands of Sumatra, Kalimantan and Papua, has one of the largest peatlands in the world, with an area of about 24 million hectares. These peatlands play an important role in global carbon storage and have very high biodiversity. However, peatlands in Indonesia also face major threats from deforestation and forest fires. In the early 21st century, the world's largest tropical mire was found in

14832-448: The land selected for plantations are typically substantial carbon stores that promote biodiverse ecosystems. Palm oil plantations have replaced much of the forested peatlands in Southeast Asia. Estimates now state that 12.9 Mha or about 47% of peatlands in Southeast Asia were deforested by 2006. In their natural state, peatlands are waterlogged with high water tables making for an inefficient soil. To create viable soil for plantation,

14976-752: The largest area of peatlands, and contains the largest peatland in the world, The Great Vasyugan Mire . Nakaikemi Wetland in southwest Honshu, Japan is more than 50,000 years old and has a depth of 45 m. The Philippi Peatland in Greece has probably one of the deepest peat layers with a depth of 190 m. According to the IPCC Sixth Assessment Report , the conservation and restoration of wetlands and peatlands has large economic potential to mitigate greenhouse gas emissions, providing benefits for adaptation, mitigation and biodiversity. Wetlands provide an environment where organic carbon

15120-464: The largest number of stable isotopes for an element being ten, for tin ( 50 Sn ). There are about 94 elements found naturally on Earth (up to plutonium inclusive), though some are detected only in very tiny amounts, such as plutonium-244 . Scientists estimate that the elements that occur naturally on Earth (some only as radioisotopes) occur as 339 isotopes ( nuclides ) in total. Only 251 of these naturally occurring nuclides are stable, in

15264-482: The least common. The 146 even-proton, even-neutron (EE) nuclides comprise ~58% of all stable nuclides and all have spin 0 because of pairing. There are also 24 primordial long-lived even-even nuclides. As a result, each of the 41 even-numbered elements from 2 to 82 has at least one stable isotope , and most of these elements have several primordial isotopes. Half of these even-numbered elements have six or more stable isotopes. The extreme stability of helium-4 due to

15408-575: The littoral zones and deltas of salty water, followed inland by swamp forests . These forests occur on the margin of peatlands with a palm rich flora with trees 70 m tall and 8 m in girth accompanied by ferns and epiphytes. The third, padang , from the Malay and Indonesian word for forest, consists of shrubs and tall thin trees and appear in the center of large peatlands. The diversity of woody species, like trees and shrubs, are far greater in tropical peatlands than in peatlands of other types. Peat in

15552-402: The longest-lived isotope), and thorium X ( Ra) are impossible to separate. Attempts to place the radioelements in the periodic table led Soddy and Kazimierz Fajans independently to propose their radioactive displacement law in 1913, to the effect that alpha decay produced an element two places to the left in the periodic table, whereas beta decay emission produced an element one place to

15696-571: The lower C levels in methane, have been discussed by Bonvicini et al. Since many sources of human food are ultimately derived from terrestrial plants, the relative concentration of C in human bodies is nearly identical to the relative concentration in the atmosphere. The rates of disintegration of potassium-40 (K) and C in the normal adult body are comparable (a few thousand decays per second). The beta decays from external (environmental) radiocarbon contribute about 0.01  mSv /year (1 mrem/year) to each person's dose of ionizing radiation . This

15840-699: The lowest-energy ground state ), for example 73 Ta ( tantalum-180m ). The common pronunciation of the AZE notation is different from how it is written: 2 He is commonly pronounced as helium-four instead of four-two-helium, and 92 U as uranium two-thirty-five (American English) or uranium-two-three-five (British) instead of 235-92-uranium. Some isotopes/nuclides are radioactive , and are therefore referred to as radioisotopes or radionuclides , whereas others have never been observed to decay radioactively and are referred to as stable isotopes or stable nuclides . For example, C

15984-458: The maximum distance traveled is estimated to be 22 cm in air and 0.27 mm in body tissue. The fraction of the radiation transmitted through the dead skin layer is estimated to be 0.11. Small amounts of carbon-14 are not easily detected by typical Geiger–Müller (G-M) detectors ; it is estimated that G-M detectors will not normally detect contamination of less than about 100,000 decays per minute (0.05 μCi). Liquid scintillation counting

16128-470: The mires in tropical regions of Indonesia and Malaysia are drained and cleared. The peatland forests harvested for palm oil production serve as above- and below-ground carbon stores, containing at least 42,069 million metric tonnes (Mt) of soil carbon. Exploitation of this land raises many environmental concerns, namely increased greenhouse gas emissions , risk of fires and a decrease in biodiversity. Greenhouse gas emissions for palm oil planted on peatlands

16272-423: The neutrons in carbon-14 decays to a proton and the carbon-14 ( half-life of 5700 ± 30 years) decays into the stable (non-radioactive) isotope nitrogen-14 . As usual with beta decay, almost all the decay energy is carried away by the beta particle and the neutrino. The emitted beta particles have a maximum energy of about 156 keV, while their weighted mean energy is 49 keV. These are relatively low energies;

16416-425: The nucleus is the atom's mass number , and each isotope of a given element has a different mass number. For example, carbon-12 , carbon-13 , and carbon-14 are three isotopes of the element carbon with mass numbers 12, 13, and 14, respectively. The atomic number of carbon is 6, which means that every carbon atom has 6 protons so that the neutron numbers of these isotopes are 6, 7, and 8 respectively. A nuclide

16560-417: The other about 22. The parabola due to the heavier gas is always much fainter than that due to the lighter, so that probably the heavier gas forms only a small percentage of the mixture." F. W. Aston subsequently discovered multiple stable isotopes for numerous elements using a mass spectrograph . In 1919 Aston studied neon with sufficient resolution to show that the two isotopic masses are very close to

16704-402: The other hand, is linked to poverty and is so widespread that it also has negatively impacts these peatlands. The biotic and abiotic factors controlling Southeast Asian peatlands are interdependent. Its soil, hydrology and morphology are created by the present vegetation through the accumulation of its own organic matter, building a favorable environment for this specific vegetation. This system

16848-689: The other naturally occurring nuclides are radioactive but occur on Earth due to their relatively long half-lives, or else due to other means of ongoing natural production. These include the afore-mentioned cosmogenic nuclides , the nucleogenic nuclides, and any radiogenic nuclides formed by ongoing decay of a primordial radioactive nuclide, such as radon and radium from uranium. An additional ~3000 radioactive nuclides not found in nature have been created in nuclear reactors and in particle accelerators. Many short-lived nuclides not found naturally on Earth have also been observed by spectroscopic analysis, being naturally created in stars or supernovae . An example

16992-726: The others. There are 41 odd-numbered elements with Z = 1 through 81, of which 39 have stable isotopes ( technetium ( 43 Tc ) and promethium ( 61 Pm ) have no stable isotopes). Of these 39 odd Z elements, 30 elements (including hydrogen-1 where 0 neutrons is even ) have one stable odd-even isotope, and nine elements: chlorine ( 17 Cl ), potassium ( 19 K ), copper ( 29 Cu ), gallium ( 31 Ga ), bromine ( 35 Br ), silver ( 47 Ag ), antimony ( 51 Sb ), iridium ( 77 Ir ), and thallium ( 81 Tl ), have two odd-even stable isotopes each. This makes

17136-405: The peat layer) matches the rate of input of new peat into the catotelm, the mire will stop growing in height. Despite accounting for just 3% of Earth's land surfaces, peatlands are collectively a major carbon store containing between 500 and 700 billion tonnes of carbon. Carbon stored within peatlands equates to over half the amount of carbon found in the atmosphere . Peatlands interact with

17280-593: The peat research collection at the University of Minnesota Duluth provides references to research on worldwide peat and peatlands. Peatlands have unusual chemistry that influences, among other things, their biota and water outflow. Peat has very high cation-exchange capacity due to its high organic matter content: cations such as Ca are preferentially adsorbed onto the peat in exchange for H ions. Water passing through peat declines in nutrients and pH . Therefore, mires are typically nutrient-poor and acidic unless

17424-516: The peatland, and allowing natural vegetation to recover. Rehabilitation projects undertaken in North America and Europe usually focus on the rewetting of peatlands and revegetation of native species. This acts to mitigate carbon release in the short term before the new growth of vegetation provides a new source of organic litter to fuel the peat formation in the long term. UNEP is supporting peatland restoration in Indonesia. Peat extraction

17568-436: The peatlands and the atmosphere has been of current concern globally in the field of ecology and biogeochemical studies. The drainage of peatlands for agriculture and forestry has resulted in the emission of extensive greenhouse gases into the atmosphere, most notably carbon dioxide and methane. By allowing oxygen to enter the peat column within a mire, drainage disrupts the balance between peat accumulation and decomposition, and

17712-414: The planet's 2500 Gt soil carbon stores. Peatlands contain the highest amounts of soil organic carbon of all wetland types. Wetlands can become sources of carbon, rather than sinks, as the decomposition occurring within the ecosystem emits methane. Natural peatlands do not always have a measurable cooling effect on the climate in a short time span as the cooling effects of sequestering carbon are offset by

17856-415: The possibility of proton decay , which would make all nuclides ultimately unstable). Some stable nuclides are in theory energetically susceptible to other known forms of decay, such as alpha decay or double beta decay, but no decay products have yet been observed, and so these isotopes are said to be "observationally stable". The predicted half-lives for these nuclides often greatly exceed the estimated age of

18000-407: The presence of other tall and dense vegetation like papyrus . Like fens, swamps are typically of higher pH level and nutrient availability than bogs. Some bogs and fens can support limited shrub or tree growth on hummocks . A marsh is a type of wetland within which vegetation is rooted in mineral soil. Peatlands are found around the globe, although are at their greatest extent at high latitudes in

18144-432: The primary exceptions). The vibrational modes of a molecule are determined by its shape and by the masses of its constituent atoms; so different isotopologues have different sets of vibrational modes. Because vibrational modes allow a molecule to absorb photons of corresponding energies, isotopologues have different optical properties in the infrared range. Atomic nuclei consist of protons and neutrons bound together by

18288-463: The project was abandoned in 1999. Similar projects in China have led to immense loss of tropical marshes and fens due to rice production. Drainage, which also increases the risk of burning, can cause additional emissions of CO 2 by 30–100 t/ha/year if the water table is lowered by only 1 m. The draining of peatlands is likely the most important and long-lasting threat to peatlands globally, but

18432-457: The properties of the various isotopes of a given element. Isotope separation is a significant technological challenge, particularly with heavy elements such as uranium or plutonium. Lighter elements such as lithium, carbon, nitrogen, and oxygen are commonly separated by gas diffusion of their compounds such as CO and NO. The separation of hydrogen and deuterium is unusual because it is based on chemical rather than physical properties, for example in

18576-586: The relative mass difference between isotopes is much less so that the mass-difference effects on chemistry are usually negligible. (Heavy elements also have relatively more neutrons than lighter elements, so the ratio of the nuclear mass to the collective electronic mass is slightly greater.) There is also an equilibrium isotope effect . Similarly, two molecules that differ only in the isotopes of their atoms ( isotopologues ) have identical electronic structures, and therefore almost indistinguishable physical and chemical properties (again with deuterium and tritium being

18720-451: The right. Soddy recognized that emission of an alpha particle followed by two beta particles led to the formation of an element chemically identical to the initial element but with a mass four units lighter and with different radioactive properties. Soddy proposed that several types of atoms (differing in radioactive properties) could occupy the same place in the table. For example, the alpha-decay of uranium-235 forms thorium-231, whereas

18864-412: The risk of fires, presenting further risk of carbon and methane to release into the atmosphere. Due to their naturally high moisture content, pristine mires have a generally low risk of fire ignition. The drying of this waterlogged state means that the carbon-dense vegetation becomes vulnerable to fire. In addition, due to the oxygen deficient nature of the vegetation, the peat fires can smolder beneath

19008-441: The same element. This is most pronounced by far for protium ( H ), deuterium ( H ), and tritium ( H ), because deuterium has twice the mass of protium and tritium has three times the mass of protium. These mass differences also affect the behavior of their respective chemical bonds, by changing the center of gravity ( reduced mass ) of the atomic systems. However, for heavier elements,

19152-406: The sense of never having been observed to decay as of the present time. An additional 35 primordial nuclides (to a total of 286 primordial nuclides), are radioactive with known half-lives, but have half-lives longer than 100 million years, allowing them to exist from the beginning of the Solar System. See list of nuclides for details. All the known stable nuclides occur naturally on Earth;

19296-602: The subsequent oxidative degradation results in the release of carbon into the atmosphere. As such, drainage of mires for agriculture transforms them from net carbon sinks to net carbon emitters. Although the emission of methane from mires has been observed to decrease following drainage, the total magnitude of emissions from peatland drainage is often greater as rates of peat accumulation are low. Peatland carbon has been described as "irrecoverable" meaning that, if lost due to drainage, it could not be recovered within time scales relevant to climate mitigation. When undertaken in such

19440-596: The surface causing incomplete combustion of the organic matter and resulting in extreme emissions events. In recent years, the occurrence of wildfires in peatlands has increased significantly worldwide particularly in the tropical regions. This can be attributed to a combination of drier weather and changes in land use which involve the drainage of water from the landscape. This resulting loss of biomass through combustion has led to significant emissions of greenhouse gasses both in tropical and boreal/temperate peatlands. Fire events are predicted to become more frequent with

19584-514: The surrounding land. A quagmire is a floating (quaking) mire, bog, or any peatland being in a stage of hydrosere or hydrarch (hydroseral) succession, resulting in pond-filling yields underfoot. Ombrotrophic types of quagmire may be called quaking bog (quivering bog). Minerotrophic types can be named with the term quagfen. Some swamps can also be peatlands (e.g.: peat swamp forest ), while marshes are generally not considered to be peatlands. Swamps are characterized by their forest canopy or

19728-476: The system from sequestering carbon again. The global distribution of tropical peatlands is concentrated in Southeast Asia where agricultural use of peatlands has been increased in recent decades. Large areas of tropical peatland have been cleared and drained for the production of food and cash crops such as palm oil. Large-scale drainage of these plantations often results in subsidence , flooding, fire and deterioration of soil quality . Small scale encroachment on

19872-455: The total carbon dioxide in a given region of Earth's atmosphere . Dating a specific sample of fossilized carbonaceous material is more complicated. Such deposits often contain trace amounts of C. These amounts can vary significantly between samples, ranging up to 1% of the ratio found in living organisms (an apparent age of about 40,000 years). This may indicate contamination by small amounts of bacteria, underground sources of radiation causing

20016-842: The tropics is therefore dominated by woody material from trunks of trees and shrubs and contain little to none of the sphagnum moss that dominates in boreal peatlands. It's only partly decomposed and the surface consists of a thick layer of leaf litter. Forestry in peatlands leads to drainage and rapid carbon losses since it decreases inputs of organic matter and accelerate the decomposition. In contrast to temperate wetlands, tropical peatlands are home to several species of fish. Many new, often endemic, species has been discovered but many of them are considered threatened. The tropical peatlands in Southeast Asia only cover 0.2% of Earth's land area but CO 2 emissions are estimated to be 2 Gt per year, equal to 7% of global fossil fuel emissions. These emissions get bigger with drainage and burning of peatlands and

20160-421: The tropics) and fires, which are predicted to become more frequent with climate change . The destruction of peatlands results in release of stored greenhouse gases into the atmosphere, further exacerbating climate change. For botanists and ecologists, the term peatland is a general term for any terrain dominated by peat to a depth of at least 30 cm (12 in), even if it has been completely drained (i.e.,

20304-420: The universe, and in fact, there are also 31 known radionuclides (see primordial nuclide ) with half-lives longer than the age of the universe. Adding in the radioactive nuclides that have been created artificially, there are 3,339 currently known nuclides . These include 905 nuclides that are either stable or have half-lives longer than 60 minutes. See list of nuclides for details. The existence of isotopes

20448-436: The warming and drying of the global climate. The United Nations Convention on Biological Diversity highlights peatlands as key ecosystems to be conserved and protected. The convention requires governments at all levels to present action plans for the conservation and management of wetland environments. Wetlands are also protected under the 1971 Ramsar Convention . Often, restoration is done by blocking drainage channels in

20592-513: The world's largest crops. In comparison to alternatives, palm oil is considered to be among the most efficient sources of vegetable oil and biofuel , requiring only 0.26 hectares of land to produce 1 ton of oil. Palm oil has therefore become a popular cash crop in many low-income countries and has provided economic opportunities for communities. With palm oil as a leading export in countries such as Indonesia and Malaysia, many smallholders have found economic success in palm oil plantations. However,

20736-513: Was first suggested in 1913 by the radiochemist Frederick Soddy , based on studies of radioactive decay chains that indicated about 40 different species referred to as radioelements (i.e. radioactive elements) between uranium and lead, although the periodic table only allowed for 11 elements between lead and uranium inclusive. Several attempts to separate these new radioelements chemically had failed. For example, Soddy had shown in 1910 that mesothorium (later shown to be Ra), radium ( Ra,

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