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103-632: Current research at Wayqecha includes a multidisciplinary project studying carbon cycling in soils and montane forests and their response to climate change , and studies of plant and animal diversity patterns along the Andean elevational gradient. Wayqecha hosted a field course of the Organization for Tropical Studies in 2007. Wayqecha is located along the Paucartambo-Shintuya road, approximately 1 hour east of Paucartambo and 4–5 hours east of Cusco ,

206-570: A coal deposit, while enhanced coal bed methane recovery is a method of recovering methane from non-mineable coal seams). It is associated with other hydrocarbon fuels, and sometimes accompanied by helium and nitrogen . Methane is produced at shallow levels (low pressure) by anaerobic decay of organic matter and reworked methane from deep under the Earth's surface. In general, the sediments that generate natural gas are buried deeper and at higher temperatures than those that contain oil . Methane

309-458: A hydrogen halide molecule and a methyl radical ( •CH 3 ). The methyl radical then reacts with a molecule of the halogen to form a molecule of the halomethane, with a new halogen atom as byproduct. Similar reactions can occur on the halogenated product, leading to replacement of additional hydrogen atoms by halogen atoms with dihalomethane , trihalomethane , and ultimately, tetrahalomethane structures, depending upon reaction conditions and

412-435: A current pH value of 8.1 to 8.2). The increase in atmospheric CO 2 shifts the pH of the ocean towards neutral in a process called ocean acidification . Oceanic absorption of CO 2 is one of the most important forms of carbon sequestering . The projected rate of pH reduction could slow the biological precipitation of calcium carbonates , thus decreasing the ocean's capacity to absorb CO 2 . The geologic component of

515-531: A given year between 10 and 100 million tonnes of carbon moves around this slow cycle. This includes volcanoes returning geologic carbon directly to the atmosphere in the form of carbon dioxide. However, this is less than one percent of the carbon dioxide put into the atmosphere by burning fossil fuels. The movement of terrestrial carbon in the water cycle is shown in the diagram on the right and explained below:  Terrestrial and marine ecosystems are chiefly connected through riverine transport, which acts as

618-487: A pressure of one atmosphere . As a gas, it is flammable over a range of concentrations (5.4%–17%) in air at standard pressure . Solid methane exists in several modifications . Presently nine are known. Cooling methane at normal pressure results in the formation of methane I. This substance crystallizes in the cubic system ( space group Fm 3 m). The positions of the hydrogen atoms are not fixed in methane I, i.e. methane molecules may rotate freely. Therefore, it

721-400: A requirement for pure methane can easily be fulfilled by steel gas bottle from standard gas suppliers. Methane is the major component of natural gas, about 87% by volume. The major source of methane is extraction from geological deposits known as natural gas fields , with coal seam gas extraction becoming a major source (see coal bed methane extraction , a method for extracting methane from

824-399: A resource that is otherwise difficult to transport for its weight, ash content, low calorific value and propensity to spontaneous combustion during storage and transport. A number of similar plants exist around the world, although mostly these plants are targeted towards the production of long chain alkanes for use as gasoline , diesel , or feedstock to other processes. Power to methane

927-415: Is a group-14 hydride , the simplest alkane , and the main constituent of natural gas . The abundance of methane on Earth makes it an economically attractive fuel , although capturing and storing it is difficult because it is a gas at standard temperature and pressure . In the Earth's atmosphere methane is transparent to visible light but absorbs infrared radiation, acting as a greenhouse gas . Methane

1030-406: Is a halogen : fluorine (F), chlorine (Cl), bromine (Br), or iodine (I). This mechanism for this process is called free radical halogenation . It is initiated when UV light or some other radical initiator (like peroxides ) produces a halogen atom . A two-step chain reaction ensues in which the halogen atom abstracts a hydrogen atom from a methane molecule, resulting in the formation of

1133-796: Is a plastic crystal . The primary chemical reactions of methane are combustion , steam reforming to syngas , and halogenation . In general, methane reactions are difficult to control. Partial oxidation of methane to methanol ( C H 3 O H ), a more convenient, liquid fuel, is challenging because the reaction typically progresses all the way to carbon dioxide and water even with an insufficient supply of oxygen . The enzyme methane monooxygenase produces methanol from methane, but cannot be used for industrial-scale reactions. Some homogeneously catalyzed systems and heterogeneous systems have been developed, but all have significant drawbacks. These generally operate by generating protected products which are shielded from overoxidation. Examples include

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1236-448: Is a tetrahedral molecule with four equivalent C–H bonds . Its electronic structure is described by four bonding molecular orbitals (MOs) resulting from the overlap of the valence orbitals on C and H . The lowest-energy MO is the result of the overlap of the 2s orbital on carbon with the in-phase combination of the 1s orbitals on the four hydrogen atoms. Above this energy level is a triply degenerate set of MOs that involve overlap of

1339-537: Is a technology that uses electrical power to produce hydrogen from water by electrolysis and uses the Sabatier reaction to combine hydrogen with carbon dioxide to produce methane. Methane can be produced by protonation of methyl lithium or a methyl Grignard reagent such as methylmagnesium chloride . It can also be made from anhydrous sodium acetate and dry sodium hydroxide , mixed and heated above 300 °C (with sodium carbonate as byproduct). In practice,

1442-553: Is abiotic. Abiotic means that methane is created from inorganic compounds, without biological activity, either through magmatic processes or via water-rock reactions that occur at low temperatures and pressures, like serpentinization . Most of Earth's methane is biogenic and is produced by methanogenesis , a form of anaerobic respiration only known to be conducted by some members of the domain Archaea . Methanogens occur in landfills and soils , ruminants (for example, cattle ),

1545-448: Is absorbed into the soil via the carbonate–silicate cycle will likely increase due to expected changes in the sun as it ages. The expected increased luminosity of the Sun will likely speed up the rate of surface weathering. This will eventually cause most of the carbon dioxide in the atmosphere to be squelched into the Earth's crust as carbonate. Once the concentration of carbon dioxide in

1648-532: Is actually the most stable carbonate phase in most part of the mantle. This is largely a result of its higher melting temperature. Consequently, scientists have concluded that carbonates undergo reduction as they descend into the mantle before being stabilised at depth by low oxygen fugacity environments. Magnesium, iron, and other metallic compounds act as buffers throughout the process. The presence of reduced, elemental forms of carbon like graphite would indicate that carbon compounds are reduced as they descend into

1751-474: Is amplifying and forcing further indirect human changes to the carbon cycle as a consequence of various positive and negative feedbacks . Current trends in climate change lead to higher ocean temperatures and acidity , thus modifying marine ecosystems. Also, acid rain and polluted runoff from agriculture and industry change the ocean's chemical composition. Such changes can have dramatic effects on highly sensitive ecosystems such as coral reefs , thus limiting

1854-400: Is an organic compound , and among the simplest of organic compounds. Methane is also a hydrocarbon . Naturally occurring methane is found both below ground and under the seafloor and is formed by both geological and biological processes. The largest reservoir of methane is under the seafloor in the form of methane clathrates . When methane reaches the surface and the atmosphere , it

1957-449: Is converted by organisms into organic carbon through photosynthesis and can either be exchanged throughout the food chain or precipitated into the oceans' deeper, more carbon-rich layers as dead soft tissue or in shells as calcium carbonate . It circulates in this layer for long periods of time before either being deposited as sediment or, eventually, returned to the surface waters through thermohaline circulation. Oceans are basic (with

2060-538: Is dependent on biotic factors, it follows a diurnal and seasonal cycle. In CO 2 measurements, this feature is apparent in the Keeling curve . It is strongest in the northern hemisphere because this hemisphere has more land mass than the southern hemisphere and thus more room for ecosystems to absorb and emit carbon. Carbon leaves the terrestrial biosphere in several ways and on different time scales. The combustion or respiration of organic carbon releases it rapidly into

2163-428: Is easier to store than hydrogen due to its higher boiling point and density, as well as its lack of hydrogen embrittlement . The lower molecular weight of the exhaust also increases the fraction of the heat energy which is in the form of kinetic energy available for propulsion, increasing the specific impulse of the rocket. Compared to liquid hydrogen , the specific energy of methane is lower but this disadvantage

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2266-426: Is evidently extremely difficult, as the lower mantle and core extend from 660 to 2,891 km and 2,891 to 6,371  km deep into the Earth respectively. Accordingly, not much is conclusively known regarding the role of carbon in the deep Earth. Nonetheless, several pieces of evidence—many of which come from laboratory simulations of deep Earth conditions—have indicated mechanisms for the element's movement down into

2369-425: Is exchanged among the biosphere , pedosphere , geosphere , hydrosphere , and atmosphere of Earth . Other major biogeochemical cycles include the nitrogen cycle and the water cycle . Carbon is the main component of biological compounds as well as a major component of many rocks such as limestone . The carbon cycle comprises a sequence of events that are key to making Earth capable of sustaining life. It describes

2472-473: Is formed at the sea surface where it can then start sinking to the ocean floor. The deep ocean gets most of its nutrients from the higher water column when they sink down in the form of marine snow . This is made up of dead or dying animals and microbes, fecal matter, sand and other inorganic material. The biological pump is responsible for transforming dissolved inorganic carbon (DIC) into organic biomass and pumping it in particulate or dissolved form into

2575-409: Is increasing the amount of methane released from wetlands due to increased temperatures and altered rainfall patterns. This phenomeon is called wetland methane feedback . Rice cultivation generates as much as 12% of total global methane emissions due to the long-term flooding of rice fields. Ruminants, such as cattle, belch methane, accounting for about 22% of the U.S. annual methane emissions to

2678-420: Is intimately connected to the movement of carbon in the Earth's surface and atmosphere. If the process did not exist, carbon would remain in the atmosphere, where it would accumulate to extremely high levels over long periods of time. Therefore, by allowing carbon to return to the Earth, the deep carbon cycle plays a critical role in maintaining the terrestrial conditions necessary for life to exist. Furthermore,

2781-470: Is known about carbon circulation in the mantle, especially in the deep Earth, but many studies have attempted to augment our understanding of the element's movement and forms within the region. For instance, a 2011 study demonstrated that carbon cycling extends all the way to the lower mantle . The study analyzed rare, super-deep diamonds at a site in Juina, Brazil , determining that the bulk composition of some of

2884-661: Is known as atmospheric methane . The Earth's atmospheric methane concentration has increased by about 160% since 1750, with the overwhelming percentage caused by human activity. It accounted for 20% of the total radiative forcing from all of the long-lived and globally mixed greenhouse gases , according to the 2021 Intergovernmental Panel on Climate Change report. Strong, rapid and sustained reductions in methane emissions could limit near-term warming and improve air quality by reducing global surface ozone. Methane has also been detected on other planets, including Mars , which has implications for astrobiology research. Methane

2987-446: Is lower than that of any other hydrocarbon, but the ratio of the heat of combustion (891 kJ/mol) to the molecular mass (16.0 g/mol, of which 12.0 g/mol is carbon) shows that methane, being the simplest hydrocarbon, produces more heat per mass unit (55.7 kJ/g) than other complex hydrocarbons. In many areas with a dense enough population, methane is piped into homes and businesses for heating , cooking, and industrial uses. In this context it

3090-460: Is mostly composed of methane, is used to produce hydrogen gas on an industrial scale. Steam methane reforming (SMR), or simply known as steam reforming, is the standard industrial method of producing commercial bulk hydrogen gas. More than 50 million metric tons are produced annually worldwide (2013), principally from the SMR of natural gas. Much of this hydrogen is used in petroleum refineries , in

3193-554: Is now usually divided into the following major reservoirs of carbon (also called carbon pools ) interconnected by pathways of exchange: The carbon exchanges between reservoirs occur as the result of various chemical, physical, geological, and biological processes. The ocean contains the largest active pool of carbon near the surface of the Earth. The natural flows of carbon between the atmosphere, ocean, terrestrial ecosystems, and sediments are fairly balanced; so carbon levels would be roughly stable without human influence. Carbon in

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3296-512: Is obtained by the reaction of CO with water via the water-gas shift reaction : This reaction is mildly exothermic (produces heat, Δ H r = −41 kJ/mol). Methane is also subjected to free-radical chlorination in the production of chloromethanes, although methanol is a more typical precursor. Hydrogen can also be produced via the direct decomposition of methane, also known as methane pyrolysis , which, unlike steam reforming, produces no greenhouse gases (GHG). The heat needed for

3399-433: Is offset by methane's greater density and temperature range, allowing for smaller and lighter tankage for a given fuel mass. Liquid methane has a temperature range (91–112 K) nearly compatible with liquid oxygen (54–90 K). The fuel currently sees use in operational launch vehicles such as Zhuque-2 and Vulcan as well as in-development launchers such as Starship , Neutron , and Terran R . Natural gas , which

3502-407: Is organic carbon, while about a third of soil carbon is stored in inorganic forms, such as calcium carbonate . Organic carbon is a major component of all organisms living on Earth. Autotrophs extract it from the air in the form of carbon dioxide, converting it to organic carbon, while heterotrophs receive carbon by consuming other organisms. Because carbon uptake in the terrestrial biosphere

3605-442: Is that more carbon stays in the atmosphere. However, the effects on the atmosphere and overall carbon cycle can be intentionally and/or naturally reversed with reforestation . Methane Methane ( US : / ˈ m ɛ θ eɪ n / METH -ayn , UK : / ˈ m iː θ eɪ n / MEE -thayn ) is a chemical compound with the chemical formula CH 4 (one carbon atom bonded to four hydrogen atoms). It

3708-439: Is to remove carbon in organic form from the surface and return it to DIC at greater depths, maintaining a surface-to-deep ocean gradient of DIC. Thermohaline circulation returns deep-ocean DIC to the atmosphere on millennial timescales. The carbon buried in the sediments can be subducted into the earth's mantle and stored for millions of years as part of the slow carbon cycle (see next section). Viruses act as "regulators" of

3811-403: Is usually known as natural gas , which is considered to have an energy content of 39 megajoules per cubic meter, or 1,000 BTU per standard cubic foot . Liquefied natural gas (LNG) is predominantly methane ( CH 4 ) converted into liquid form for ease of storage or transport. Refined liquid methane as well as LNG is used as a rocket fuel , when combined with liquid oxygen , as in

3914-401: Is very long. This is what gives Uranus and Neptune their blue or bluish-green colors, as light passes through their atmospheres containing methane and is then scattered back out. The familiar smell of natural gas as used in homes is achieved by the addition of an odorant , usually blends containing tert -butylthiol , as a safety measure. Methane has a boiling point of −161.5  °C at

4017-542: The Catalytica system , copper zeolites , and iron zeolites stabilizing the alpha-oxygen active site. One group of bacteria catalyze methane oxidation with nitrite as the oxidant in the absence of oxygen , giving rise to the so-called anaerobic oxidation of methane . Like other hydrocarbons , methane is an extremely weak acid . Its p K a in DMSO is estimated to be 56. It cannot be deprotonated in solution, but

4120-586: The Sabatier process . Methane is also a side product of the hydrogenation of carbon monoxide in the Fischer–Tropsch process , which is practiced on a large scale to produce longer-chain molecules than methane. An example of large-scale coal-to-methane gasification is the Great Plains Synfuels plant, started in 1984 in Beulah, North Dakota as a way to develop abundant local resources of low-grade lignite ,

4223-477: The TQ-12 , BE-4 , Raptor , and YF-215 engines. Due to the similarities between methane and LNG such engines are commonly grouped together under the term methalox . As a liquid rocket propellant, a methane/ liquid oxygen combination offers the advantage over kerosene / liquid oxygen combination, or kerolox, of producing small exhaust molecules, reducing coking or deposition of soot on engine components. Methane

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4326-634: The conjugate base is known in forms such as methyllithium . A variety of positive ions derived from methane have been observed, mostly as unstable species in low-pressure gas mixtures. These include methenium or methyl cation CH + 3 , methane cation CH + 4 , and methanium or protonated methane CH + 5 . Some of these have been detected in outer space . Methanium can also be produced as diluted solutions from methane with superacids . Cations with higher charge, such as CH 2+ 6 and CH 3+ 7 , have been studied theoretically and conjectured to be stable. Despite

4429-497: The strength of its C–H bonds, there is intense interest in catalysts that facilitate C–H bond activation in methane (and other lower numbered alkanes ). Methane's heat of combustion is 55.5 MJ/kg. Combustion of methane is a multiple step reaction summarized as follows: Peters four-step chemistry is a systematically reduced four-step chemistry that explains the burning of methane. Given appropriate conditions, methane reacts with halogen radicals as follows: where X

4532-406: The 2p orbitals on carbon with various linear combinations of the 1s orbitals on hydrogen. The resulting "three-over-one" bonding scheme is consistent with photoelectron spectroscopic measurements. Methane is an odorless, colourless and transparent gas. It does absorb visible light, especially at the red end of the spectrum, due to overtone bands , but the effect is only noticeable if the light path

4635-525: The Earth's crust between rocks, soil, ocean and atmosphere. The fast carbon cycle involves relatively short-term biogeochemical processes between the environment and living organisms in the biosphere (see diagram at start of article ). It includes movements of carbon between the atmosphere and terrestrial and marine ecosystems, as well as soils and seafloor sediments. The fast cycle includes annual cycles involving photosynthesis and decadal cycles involving vegetative growth and decomposition. The reactions of

4738-416: The Earth's atmosphere exists in two main forms: carbon dioxide and methane . Both of these gases absorb and retain heat in the atmosphere and are partially responsible for the greenhouse effect . Methane produces a larger greenhouse effect per volume as compared to carbon dioxide, but it exists in much lower concentrations and is more short-lived than carbon dioxide. Thus, carbon dioxide contributes more to

4841-430: The added carbon is projected to remain in the atmosphere for centuries to millennia. Halocarbons are less prolific compounds developed for diverse uses throughout industry; for example as solvents and refrigerants . Nevertheless, the buildup of relatively small concentrations (parts per trillion) of chlorofluorocarbon , hydrofluorocarbon , and perfluorocarbon gases in the atmosphere is responsible for about 10% of

4944-458: The atmosphere falls below approximately 50 parts per million (tolerances vary among species), C 3 photosynthesis will no longer be possible. This has been predicted to occur 600 million years from the present, though models vary. Once the oceans on the Earth evaporate in about 1.1 billion years from now, plate tectonics will very likely stop due to the lack of water to lubricate them. The lack of volcanoes pumping out carbon dioxide will cause

5047-435: The atmosphere has increased nearly 52% over pre-industrial levels by 2020, resulting in global warming . The increased carbon dioxide has also caused a reduction in the ocean's pH value and is fundamentally altering marine chemistry . Carbon dioxide is critical for photosynthesis. The carbon cycle was first described by Antoine Lavoisier and Joseph Priestley , and popularised by Humphry Davy . The global carbon cycle

5150-413: The atmosphere —but the timescale to reach equilibrium with the atmosphere is hundreds of years: the exchange of carbon between the two layers, driven by thermohaline circulation , is slow. Carbon enters the ocean mainly through the dissolution of atmospheric carbon dioxide, a small fraction of which is converted into carbonate . It can also enter the ocean through rivers as dissolved organic carbon . It

5253-426: The atmosphere. One study reported that the livestock sector in general (primarily cattle, chickens, and pigs) produces 37% of all human-induced methane. A 2013 study estimated that livestock accounted for 44% of human-induced methane and about 15% of human-induced greenhouse gas emissions. Many efforts are underway to reduce livestock methane production, such as medical treatments and dietary adjustments, and to trap

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5356-443: The atmosphere. It can also be exported into the ocean through rivers or remain sequestered in soils in the form of inert carbon. Carbon stored in soil can remain there for up to thousands of years before being washed into rivers by erosion or released into the atmosphere through soil respiration . Between 1989 and 2008 soil respiration increased by about 0.1% per year. In 2008, the global total of CO 2 released by soil respiration

5459-405: The atmosphere. More directly, it often leads to the release of carbon from terrestrial ecosystems into the atmosphere. Deforestation for agricultural purposes removes forests, which hold large amounts of carbon, and replaces them, generally with agricultural or urban areas. Both of these replacement land cover types store comparatively small amounts of carbon so that the net result of the transition

5562-425: The atmosphere. Slow or geological cycles (also called deep carbon cycle ) can take millions of years to complete, moving substances through the Earth's crust between rocks, soil, ocean and atmosphere. Humans have disturbed the carbon cycle for many centuries. They have done so by modifying land use and by mining and burning carbon from ancient organic remains ( coal , petroleum and gas ). Carbon dioxide in

5665-679: The breakup of organic matter at elevated temperatures and pressures in deep sedimentary strata . Most methane in sedimentary basins is thermogenic; therefore, thermogenic methane is the most important source of natural gas. Thermogenic methane components are typically considered to be relic (from an earlier time). Generally, formation of thermogenic methane (at depth) can occur through organic matter breakup, or organic synthesis. Both ways can involve microorganisms ( methanogenesis ), but may also occur inorganically. The processes involved can also consume methane, with and without microorganisms. The more important source of methane at depth (crystalline bedrock)

5768-455: The carbon contained in all of Earth's living terrestrial biomass. Recent rates of global emissions directly into the atmosphere have exceeded the uptake by vegetation and the oceans. These sinks have been expected and observed to remove about half of the added atmospheric carbon within about a century. Nevertheless, sinks like the ocean have evolving saturation properties , and a substantial fraction (20–35%, based on coupled models ) of

5871-529: The carbon cycle and contribute to further warming. The largest and one of the fastest growing human impacts on the carbon cycle and biosphere is the extraction and burning of fossil fuels , which directly transfer carbon from the geosphere into the atmosphere. Carbon dioxide is also produced and released during the calcination of limestone for clinker production. Clinker is an industrial precursor of cement . As of 2020 , about 450 gigatons of fossil carbon have been extracted in total; an amount approaching

5974-410: The carbon cycle operates slowly in comparison to the other parts of the global carbon cycle. It is one of the most important determinants of the amount of carbon in the atmosphere, and thus of global temperatures. Most of the Earth's carbon is stored inertly in the Earth's lithosphere . Much of the carbon stored in the Earth's mantle was stored there when the Earth formed. Some of it was deposited in

6077-414: The carbon cycle to end between 1 billion and 2 billion years into the future. The terrestrial biosphere includes the organic carbon in all land-living organisms, both alive and dead, as well as carbon stored in soils . About 500 gigatons of carbon are stored above ground in plants and other living organisms, while soil holds approximately 1,500 gigatons of carbon. Most carbon in the terrestrial biosphere

6180-424: The carbon they store into the atmosphere. There is a fast and a slow carbon cycle. The fast cycle operates in the biosphere and the slow cycle operates in rocks . The fast or biological cycle can complete within years, moving carbon from atmosphere to biosphere, then back to the atmosphere. The slow or geological cycle may extend deep into the mantle and can take millions of years to complete, moving carbon through

6283-608: The chosen catalyst. Dozens of catalysts have been tested, including unsupported and supported metal catalysts, carbonaceous and metal-carbon catalysts. The reaction is moderately endothermic as shown in the reaction equation below. As a refrigerant , methane has the ASHRAE designation R-50 . Methane can be generated through geological, biological or industrial routes. The two main routes for geological methane generation are (i) organic (thermally generated, or thermogenic) and (ii) inorganic ( abiotic ). Thermogenic methane occurs due to

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6386-588: The cold gas, the gas at ambient temperature is lighter than air. Gas pipelines distribute large amounts of natural gas, of which methane is the principal component. Methane is used as a fuel for ovens, homes, water heaters, kilns, automobiles, turbines, etc. As the major constituent of natural gas , methane is important for electricity generation by burning it as a fuel in a gas turbine or steam generator . Compared to other hydrocarbon fuels , methane produces less carbon dioxide for each unit of heat released. At about 891 kJ/mol, methane's heat of combustion

6489-439: The deep ocean. Inorganic nutrients and carbon dioxide are fixed during photosynthesis by phytoplankton, which both release dissolved organic matter (DOM) and are consumed by herbivorous zooplankton. Larger zooplankton - such as copepods , egest fecal pellets - which can be reingested, and sink or collect with other organic detritus into larger, more-rapidly-sinking aggregates. DOM is partially consumed by bacteria and respired;

6592-421: The diamonds' inclusions matched the expected result of basalt melting and crystallisation under lower mantle temperatures and pressures. Thus, the investigation's findings indicate that pieces of basaltic oceanic lithosphere act as the principle transport mechanism for carbon to Earth's deep interior. These subducted carbonates can interact with lower mantle silicates , eventually forming super-deep diamonds like

6695-435: The fast carbon cycle because they impact the material cycles and energy flows of food webs and the microbial loop . The average contribution of viruses to the Earth ecosystem carbon cycle is 8.6%, of which its contribution to marine ecosystems (1.4%) is less than its contribution to terrestrial (6.7%) and freshwater (17.8%) ecosystems. Over the past 2,000 years, anthropogenic activities and climate change have gradually altered

6798-418: The fast carbon cycle to human activities will determine many of the more immediate impacts of climate change. The slow (or deep) carbon cycle involves medium to long-term geochemical processes belonging to the rock cycle (see diagram on the right). The exchange between the ocean and atmosphere can take centuries, and the weathering of rocks can take millions of years. Carbon in the ocean precipitates to

6901-403: The flow of CO 2 . The length of carbon sequestering in soil is dependent on local climatic conditions and thus changes in the course of climate change . The ocean can be conceptually divided into a surface layer within which water makes frequent (daily to annual) contact with the atmosphere, and a deep layer below the typical mixed layer depth of a few hundred meters or less, within which

7004-535: The form of dissolved organic carbon (DOC) and particulate organic carbon (POC)) from terrestrial to oceanic systems. During transport, part of DOC will rapidly return to the atmosphere through redox reactions , causing "carbon degassing" to occur between land-atmosphere storage layers. The remaining DOC and dissolved inorganic carbon (DIC) are also exported to the ocean. In 2015, inorganic and organic carbon export fluxes from global rivers were assessed as 0.50–0.70 Pg C y and 0.15–0.35 Pg C y respectively. On

7107-471: The form of organic carbon from the biosphere. Of the carbon stored in the geosphere, about 80% is limestone and its derivatives, which form from the sedimentation of calcium carbonate stored in the shells of marine organisms. The remaining 20% is stored as kerogens formed through the sedimentation and burial of terrestrial organisms under high heat and pressure. Organic carbon stored in the geosphere can remain there for millions of years. Carbon can leave

7210-434: The gas to use its combustion energy. Most of the subseafloor is anoxic because oxygen is removed by aerobic microorganisms within the first few centimeters of the sediment . Below the oxygen-replete seafloor, methanogens produce methane that is either used by other organisms or becomes trapped in gas hydrates . These other organisms that utilize methane for energy are known as methanotrophs ('methane-eating'), and are

7313-636: The geophysical observations. Since the Industrial Revolution , and especially since the end of WWII , human activity has substantially disturbed the global carbon cycle by redistributing massive amounts of carbon from the geosphere. Humans have also continued to shift the natural component functions of the terrestrial biosphere with changes to vegetation and other land use. Man-made (synthetic) carbon compounds have been designed and mass-manufactured that will persist for decades to millennia in air, water, and sediments as pollutants. Climate change

7416-431: The geosphere in several ways. Carbon dioxide is released during the metamorphism of carbonate rocks when they are subducted into the Earth's mantle. This carbon dioxide can be released into the atmosphere and ocean through volcanoes and hotspots . It can also be removed by humans through the direct extraction of kerogens in the form of fossil fuels . After extraction, fossil fuels are burned to release energy and emit

7519-608: The global greenhouse effect than methane. Carbon dioxide is removed from the atmosphere primarily through photosynthesis and enters the terrestrial and oceanic biospheres. Carbon dioxide also dissolves directly from the atmosphere into bodies of water (ocean, lakes, etc.), as well as dissolving in precipitation as raindrops fall through the atmosphere. When dissolved in water, carbon dioxide reacts with water molecules and forms carbonic acid , which contributes to ocean acidity. It can then be absorbed by rocks through weathering. It also can acidify other surfaces it touches or be washed into

7622-449: The guts of termites, and the anoxic sediments below the seafloor and the bottom of lakes. This multistep process is used by these microorganisms for energy. The net reaction of methanogenesis is: The final step in the process is catalyzed by the enzyme methyl coenzyme M reductase (MCR). Wetlands are the largest natural sources of methane to the atmosphere, accounting for approximately 20 - 30% of atmospheric methane. Climate change

7725-401: The halogen-to-methane ratio. This reaction is commonly used with chlorine to produce dichloromethane and chloroform via chloromethane . Carbon tetrachloride can be made with excess chlorine. Methane may be transported as a refrigerated liquid (liquefied natural gas, or LNG ). While leaks from a refrigerated liquid container are initially heavier than air due to the increased density of

7828-448: The invention of agriculture, humans have directly and gradually influenced the carbon cycle over century-long timescales by modifying the mixture of vegetation in the terrestrial biosphere. Over the past several centuries, direct and indirect human-caused land use and land cover change (LUCC) has led to the loss of biodiversity , which lowers ecosystems' resilience to environmental stresses and decreases their ability to remove carbon from

7931-416: The lithosphere. This process, called carbon outgassing, is the result of carbonated mantle undergoing decompression melting, as well as mantle plumes carrying carbon compounds up towards the crust. Carbon is oxidised upon its ascent towards volcanic hotspots, where it is then released as CO 2 . This occurs so that the carbon atom matches the oxidation state of the basalts erupting in such areas. Although

8034-443: The lower mantle, as well as the forms that carbon takes at the extreme temperatures and pressures of said layer. Furthermore, techniques like seismology have led to a greater understanding of the potential presence of carbon in the Earth's core. Carbon principally enters the mantle in the form of carbonate -rich sediments on tectonic plates of ocean crust, which pull the carbon into the mantle upon undergoing subduction . Not much

8137-404: The lower mantle. As an example, preliminary theoretical studies suggest that high pressure causes carbonate melt viscosity to increase; the melts' lower mobility as a result of its increased viscosity causes large deposits of carbon deep into the mantle. Accordingly, carbon can remain in the lower mantle for long periods of time, but large concentrations of carbon frequently find their way back to

8240-450: The main channel through which erosive terrestrially derived substances enter into oceanic systems. Material and energy exchanges between the terrestrial biosphere and the lithosphere as well as organic carbon fixation and oxidation processes together regulate ecosystem carbon and dioxygen (O 2 ) pools. Riverine transport, being the main connective channel of these pools, will act to transport net primary productivity (primarily in

8343-482: The main reason why little methane generated at depth reaches the sea surface. Consortia of Archaea and Bacteria have been found to oxidize methane via anaerobic oxidation of methane (AOM); the organisms responsible for this are anaerobic methanotrophic Archaea (ANME) and sulfate-reducing bacteria (SRB). Given its cheap abundance in natural gas, there is little incentive to produce methane industrially. Methane can be produced by hydrogenating carbon dioxide through

8446-720: The mantle. Polymorphism alters carbonate compounds' stability at different depths within the Earth. To illustrate, laboratory simulations and density functional theory calculations suggest that tetrahedrally coordinated carbonates are most stable at depths approaching the core–mantle boundary . A 2015 study indicates that the lower mantle's high pressure causes carbon bonds to transition from sp 2 to sp 3 hybridised orbitals , resulting in carbon tetrahedrally bonding to oxygen. CO 3 trigonal groups cannot form polymerisable networks, while tetrahedral CO 4 can, signifying an increase in carbon's coordination number , and therefore drastic changes in carbonate compounds' properties in

8549-468: The movement of carbon as it is recycled and reused throughout the biosphere, as well as long-term processes of carbon sequestration (storage) to and release from carbon sinks . To describe the dynamics of the carbon cycle, a distinction can be made between the fast and slow carbon cycle. The fast cycle is also referred to as the biological carbon cycle . Fast cycles can complete within years, moving substances from atmosphere to biosphere, then back to

8652-468: The nearest city. This article about a biology organization is a stub . You can help Misplaced Pages by expanding it . This ecology -related article is a stub . You can help Misplaced Pages by expanding it . This article about an organisation in Peru is a stub . You can help Misplaced Pages by expanding it . Carbon cycle The carbon cycle is that part of the biogeochemical cycle by which carbon

8755-541: The ocean each currently take up about one-quarter of anthropogenic carbon emissions each year. These feedbacks are expected to weaken in the future, amplifying the effect of anthropogenic carbon emissions on climate change. The degree to which they will weaken, however, is highly uncertain, with Earth system models predicting a wide range of land and ocean carbon uptakes even under identical atmospheric concentration or emission scenarios. Arctic methane emissions indirectly caused by anthropogenic global warming also affect

8858-457: The ocean floor where it can form sedimentary rock and be subducted into the Earth's mantle . Mountain building processes result in the return of this geologic carbon to the Earth's surface. There the rocks are weathered and carbon is returned to the atmosphere by degassing and to the ocean by rivers. Other geologic carbon returns to the ocean through the hydrothermal emission of calcium ions. In

8961-441: The ocean floor. However, through processes such as coagulation and expulsion in predator fecal pellets, these cells form aggregates. These aggregates have sinking rates orders of magnitude greater than individual cells and complete their journey to the deep in a matter of days. About 1% of the particles leaving the surface ocean reach the seabed and are consumed, respired, or buried in the sediments. The net effect of these processes

9064-409: The ocean's ability to absorb carbon from the atmosphere on a regional scale and reducing oceanic biodiversity globally. The exchanges of carbon between the atmosphere and other components of the Earth system, collectively known as the carbon cycle, currently constitute important negative (dampening) feedbacks on the effect of anthropogenic carbon emissions on climate change. Carbon sinks in the land and

9167-431: The ocean. Human activities over the past two centuries have increased the amount of carbon in the atmosphere by nearly 50% as of year 2020, mainly in the form of carbon dioxide, both by modifying ecosystems' ability to extract carbon dioxide from the atmosphere and by emitting it directly, e.g., by burning fossil fuels and manufacturing concrete. In the far future (2 to 3 billion years), the rate at which carbon dioxide

9270-463: The one found. However, carbonates descending to the lower mantle encounter other fates in addition to forming diamonds. In 2011, carbonates were subjected to an environment similar to that of 1800 km deep into the Earth, well within the lower mantle. Doing so resulted in the formations of magnesite , siderite , and numerous varieties of graphite . Other experiments—as well as petrologic observations—support this claim, indicating that magnesite

9373-402: The other hand, POC can remain buried in sediment over an extensive period, and the annual global terrestrial to oceanic POC flux has been estimated at 0.20 (+0.13,-0.07) Gg C y . The ocean biological pump is the ocean's biologically driven sequestration of carbon from the atmosphere and land runoff to the deep ocean interior and seafloor sediments . The biological pump is not so much

9476-417: The presence of carbon in the Earth's core is well-constrained, recent studies suggest large inventories of carbon could be stored in this region. Shear (S) waves moving through the inner core travel at about fifty percent of the velocity expected for most iron-rich alloys. Because the core's composition is believed to be an alloy of crystalline iron and a small amount of nickel, this seismic anomaly indicates

9579-410: The presence of light elements, including carbon, in the core. In fact, studies using diamond anvil cells to replicate the conditions in the Earth's core indicate that iron carbide (Fe 7 C 3 ) matches the inner core's wave speed and density. Therefore, the iron carbide model could serve as an evidence that the core holds as much as 67% of the Earth's carbon. Furthermore, another study found that in

9682-400: The pressure and temperature condition of the Earth's inner core, carbon dissolved in iron and formed a stable phase with the same Fe 7 C 3 composition—albeit with a different structure from the one previously mentioned. In summary, although the amount of carbon potentially stored in the Earth's core is not known, recent studies indicate that the presence of iron carbides can explain some of

9785-417: The process is also significant simply due to the massive quantities of carbon it transports through the planet. In fact, studying the composition of basaltic magma and measuring carbon dioxide flux out of volcanoes reveals that the amount of carbon in the mantle is actually greater than that on the Earth's surface by a factor of one thousand. Drilling down and physically observing deep-Earth carbon processes

9888-457: The production of chemicals and in food processing. Very large quantities of hydrogen are used in the industrial synthesis of ammonia . At high temperatures (700–1100 °C) and in the presence of a metal -based catalyst ( nickel ), steam reacts with methane to yield a mixture of CO and H 2 , known as "water gas" or " syngas ": This reaction is strongly endothermic (consumes heat, Δ H r = 206 kJ/mol). Additional hydrogen

9991-469: The reaction can also be GHG emission free, e.g. from concentrated sunlight, renewable electricity, or burning some of the produced hydrogen. If the methane is from biogas then the process can be a carbon sink . Temperatures in excess of 1200 °C are required to break the bonds of methane to produce hydrogen gas and solid carbon. However, through the use of a suitable catalyst the reaction temperature can be reduced to between 550-900 °C depending on

10094-425: The regulatory role of viruses in ecosystem carbon cycling processes. This has been particularly conspicuous over the past 200 years due to rapid industrialization and the attendant population growth. Slow or deep carbon cycling is an important process, though it is not as well-understood as the relatively fast carbon movement through the atmosphere, terrestrial biosphere, ocean, and geosphere. The deep carbon cycle

10197-421: The remaining refractory DOM is advected and mixed into the deep sea. DOM and aggregates exported into the deep water are consumed and respired, thus returning organic carbon into the enormous deep ocean reservoir of DIC. A single phytoplankton cell has a sinking rate around one metre per day. Given that the average depth of the ocean is about four kilometres, it can take over ten years for these cells to reach

10300-412: The result of a single process, but rather the sum of a number of processes each of which can influence biological pumping. The pump transfers about 11 billion tonnes of carbon every year into the ocean's interior. An ocean without the biological pump would result in atmospheric CO 2 levels about 400 ppm higher than the present day. Most carbon incorporated in organic and inorganic biological matter

10403-413: The time between consecutive contacts may be centuries. The dissolved inorganic carbon (DIC) in the surface layer is exchanged rapidly with the atmosphere, maintaining equilibrium. Partly because its concentration of DIC is about 15% higher but mainly due to its larger volume, the deep ocean contains far more carbon—it is the largest pool of actively cycled carbon in the world, containing 50 times more than

10506-630: The total direct radiative forcing from all long-lived greenhouse gases (year 2019); which includes forcing from the much larger concentrations of carbon dioxide and methane. Chlorofluorocarbons also cause stratospheric ozone depletion . International efforts are ongoing under the Montreal Protocol and Kyoto Protocol to control rapid growth in the industrial manufacturing and use of these environmentally potent gases. For some applications more benign alternatives such as hydrofluoroolefins have been developed and are being gradually introduced. Since

10609-481: Was roughly 98 billion tonnes , about 3 times more carbon than humans are now putting into the atmosphere each year by burning fossil fuel (this does not represent a net transfer of carbon from soil to atmosphere, as the respiration is largely offset by inputs to soil carbon). There are a few plausible explanations for this trend, but the most likely explanation is that increasing temperatures have increased rates of decomposition of soil organic matter , which has increased

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