Nitrogen: chemical element that has the symbol N

Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere. The element nitrogen was discovered as a separable component of air, by Scottish physician Daniel Rutherford, in 1772.Sony VAIO VPCF116FGBI Battery

Many industrially important compounds, such as ammonia, nitric acid, organic nitrates (propellants and explosives), andcyanides, contain nitrogen. The extremely strong bond in elemental nitrogen dominates nitrogen chemistry, causing difficulty for both organisms and industry in breaking the bond to convert the N2 into useful compounds,Sony VAIO VPCF117FJ/W Battery

but at the same time causing release of large amounts of often useful energy when the compounds burn, explode, or decay back into nitrogen gas.

Nitrogen occurs in all living organisms, and the nitrogen cycle describes movement of the element from the air into thebiosphere and organic compounds, then back into the atmosphere. Sony VAIO VPCF117HG/BI Battery

Synthetically produced nitrates are key ingredients of industrial fertilizers, and also key pollutants in causing the eutrophication of water systems. Nitrogen is a constituent element of amino acids and thus of proteins and nucleic acids (DNA and RNA). It resides in the chemical structure of almost all neurotransmitters, and is a defining component of alkaloids, biological molecules produced by many organisms.Sony VAIO VPCF118FJ/W Battery

The human body contains about 3% by weight of nitrogen, a larger fraction than all elements save oxygen, carbon, and hydrogen.

History

Nitrogen is formally considered to have been discovered by Daniel Rutherford in 1772, who called it noxious air or fixed air.Sony VAIO VPCF119FC Battery

The fact that there was an element of air that does not support combustion was clear to Rutherford. Nitrogen was also studied at about the same time by Carl Wilhelm Scheele, Henry Cavendish, and Joseph Priestley, who referred to it as burnt airor phlogisticated air.Sony VAIO VPCF119FC/BI Battery

Nitrogen gas was inert enough that Antoine Lavoisier referred to it as "mephitic air" or azote, from the Greek word ?????? (azotos) meaning "lifeless". In it, animals died and flames were extinguished. Lavoisier's name for nitrogen is used in many languages (French, Polish, Russian, etc.) and still remains in English in the common names of many compounds, such as hydrazine and compounds of the azide ion.Sony VAIO VPCF119FJ/BI Battery

The English word nitrogen (1794) entered the language from the French nitrogène, coined in 1790 by French chemist Jean Antoine Chaptal (1756–1832), from "nitre" + Fr. gène "producing" (from Gk. -????? means "forming" or "giving birth to."). The gas had been found in nitric acid.Sony VAIO VPCF11AFJ Battery

Chaptal's meaning was that nitrogen gas is the essential part of nitric acid, in turn formed from saltpetre (potassium nitrate), then known as nitre. However, this word in the more ancient world originally described sodium salts that did not contain nitrate, and is a cognate of natron and nitron.Sony VAIO VPCF11AGJ Battery

Nitrogen compounds were well known during the Middle Ages. Alchemists knew nitric acid as aqua fortis (strong water). The mixture of nitric and hydrochloric acids was known as aqua regia (royal water), celebrated for its ability to dissolve gold(the king of metals).Sony VAIO VPCF11AHJ Battery

The earliest military, industrial, and agricultural applications of nitrogen compounds involved uses saltpetre (sodium nitrate or potassium nitrate), the most notable in gunpowder, and later as fertilizer. In 1910, Lord Rayleigh discovered that an electrical discharge in nitrogen gas produced "active nitrogen", an allotrope considered to bemonatomic.Sony VAIO VPCF11JFX/B Battery

The "whirling cloud of brilliant yellow light" produced by his apparatus reacted with quicksilver to produce explosive mercury nitride.

Properties

Nitrogen is a nonmetal, with an electronegativity of 3.04. It has five electrons in its outer shell and is, therefore,trivalent in most compounds. Sony VAIO VPCF11M1E Battery

The triple bond in molecular nitrogen (N2) is one of the strongest. The resulting difficulty of converting N2 into other compounds, and the ease (and associated high energy release) of converting nitrogen compounds into elemental N2, have dominated the role of nitrogen in both nature and human economic activities.Sony VAIO VPCF11M1E/H Battery

At atmospheric pressure molecular nitrogen condenses (liquefies) at 77 K (?195.79 °C) and freezes at 63 K (?210.01 °C)[1]into the beta hexagonal close-packed crystal allotropic form. Below 35.4 K (?237.6 °C) nitrogen assumes the cubic crystal allotropic form (called the alpha-phase).Sony VAIO VPCF11MFX/B Battery

Liquid nitrogen, a fluid resembling water in appearance, but with 80.8% of the density (the density of liquid nitrogen at its boiling point is 0.808 g/mL), is a common cryogen.

Unstable allotropes of nitrogen consisting of more than two nitrogen atoms have been produced in the laboratory, like N3andN4.Sony VAIO VPCF11S1E Battery

Under extremely high pressures (1.1 million atm) and high temperatures (2000 K), as produced using a diamond anvil cell, nitrogen polymerizes into the single-bonded cubic gauche crystal structure. This structure is similar to that ofdiamond, and both have extremely strong covalent bonds. N4 is nicknamed "nitrogen diamond." Sony VAIO VPCF11S1E/B Battery

Other (as yet unsynthesized) allotropes include hexazine (N6, a benzene analog) and octaazacubane (N8, a cubane analog).The former is predicted to be highly unstable, while the latter is predicted to be stable, for reasons of orbital symmetry.

Isotopes

There are two stable isotopes of nitrogen: 14N and 15N. By far the most common is 14N (99.634%), which is produced in the CNO cycle in stars. Sony VAIO VPCF11Z1E Battery

Of the ten isotopes produced synthetically, 13N has a half-life of ten minutes and the remaining isotopes have half-lives on the order of seconds or less. Biologically mediated reactions (e.g., assimilation, nitrification, anddenitrification) strongly control nitrogen dynamics in the soil. These reactions typically result in 15N enrichment of thesubstrate and depletion of the product.Sony VAIO VPCF11Z1E/BI Battery

A small part (0.73%) of the molecular nitrogen in Earth's atmosphere is the isotopologue 14N15N, and almost all the rest is14N2.

Radioisotope 16N is the dominant radionuclide in the coolant of pressurized water reactors or boiling water reactors during normal operation. It is produced from 16O (in water) via (n,p) reaction. It has a short half-life of about 7.1 s, but during its decay back to 16O produces high-energy gamma radiation (5 to 7 MeV).Sony VAIO VPCF11ZHJ Battery

Because of this, the access to the primary coolant piping in a pressurized water reactor must be restricted during reactor power operation.16N is one of the main means used to immediately detect even small leaks from the primary coolant to the secondary steam cycle.Sony VAIO VPCF127HGBI Battery

In similar fashion, access to any of the steam cycle components in a boiling water reactor nuclear power plant must be restricted during operation. Condensate from the condenser is typically retained for 10 minutes to allow for decay of the 16N. This eliminates the need to shield and restrict access to any of the feed water piping or pumps.Sony VAIO VPCF137HG/BI Battery

Electromagnetic spectrum

Molecular nitrogen (14N2) is largely transparent to infrared and visible radiation because it is a homonuclear molecule and, thus, has no dipole moment to couple to electromagnetic radiation at these wavelengths. Significant absorption occurs at extreme ultraviolet wavelengths, beginning around 100 nanometers.Sony VAIO VPCS111FM/S Battery

This is associated with electronic transitions in the molecule to states in which charge is not distributed evenly between nitrogen atoms. Nitrogen absorption leads to significant absorption of ultraviolet radiation in the Earth's upper atmosphere and the atmospheres of other planetary bodies. Sony VAIO VPCS115EC Battery

For similar reasons, pure molecular nitrogen lasers typically emit light in the ultraviolet range.

Nitrogen also makes a contribution to visible air glow from the Earth's upper atmosphere, through electron impact excitation followed by emission. This visible blue air glow (seen in the polar aurora and in the re-entry glow of returning spacecraft) typically results not from molecular nitrogen but rather from free nitrogen atoms combining with oxygen to form nitric oxide (NO).Sony VAIO VPCS115FG Battery

Nitrogen gas also exhibits scintillation.

Reactions

In general, nitrogen is unreactive at standard temperature and pressure. N2 reacts spontaneously with few reagents, being resilient to acids andbases as well as oxidants and most reductants. Sony VAIO VPCS117GG Battery

When nitrogen reacts spontaneously with a reagent, the net transformation is often callednitrogen fixation.

Nitrogen reacts with elemental lithium. Lithium burns in an atmosphere of N2 to give lithium nitride:

6 Li + N2 ? 2 Li3N

Magnesium also burns in nitrogen, forming magnesium nitride.Sony VAIO VPCS117GGB Battery

3 Mg + N2 ? Mg3N2

N2 forms a variety of adducts with transition metals. The first example of a dinitrogen complex is [Ru(NH3)5(N2)]2+ (see figure at right). Such compounds are now numerous, other examples include IrCl(N2)(PPh3)2, W(N2)2(Ph2PCH2CH2PPh2)2, and [(?5-C5Me4H)2Zr]2(?2, ?2,?2-N2).Sony VAIO VPCS118EC Battery

These complexes illustrate how N2 might bind to the metal(s) in nitrogenase and the catalyst for theHaber process.[13] A catalytic process to reduce N2 to ammonia with the use of a molybdenum complex in the presence of a proton source was published in 2005.Sony VAIO VPCS119FJ/B Battery

The starting point for industrial production of nitrogen compounds is the Haber process, in which nitrogen is fixed by reacting N2and H2 over an iron(III) oxide (Fe3O4) catalyst at about 500 °C and 200 atmospheres pressure. Biological nitrogen fixation in free-living cyanobacteria and in the root nodules of plants also produces ammonia from molecular nitrogen.Sony VAIO VPCS119GC Battery

The reaction, which is the source of the bulk of nitrogen in the biosphere, is catalyzed by the nitrogenase enzyme complex that contains Fe and Mo atoms, using energy derived from hydrolysis of adenosine triphosphate (ATP) into adenosine diphosphate and inorganic phosphate (?20.5 kJ/mol).Sony VAIO VPCS11AFJ Battery

Occurrence

Nitrogen is the largest single constituent of the Earth's atmosphere (78.082% by volume of dry air, 75.3% by weight in dry air). It is created by fusion processes in stars, and is estimated to be the seventh most abundant chemical element by mass in the universe.Sony VAIO VPCS11AGJ Battery

Molecular nitrogen and nitrogen compounds have been detected in interstellar space by astronomers using the Far Ultraviolet Spectroscopic Explorer. Molecular nitrogen is a major constituent of the Saturnian moon Titan's thick atmosphere, and occurs in slightly appreciable to trace amounts in other planetary atmospheres.Sony VAIO VPCS11AHJ Battery

Nitrogen is present in all living organisms, in proteins, nucleic acids, and other molecules. It typically makes up around 4% of the dry weight of plant matter, and around 3% of the weight of the human body. It is a large component of animal waste (for example, guano), usually in the form of urea, uric acid, ammonium compounds, and derivatives of these nitrogenous products, which are essential nutrients for all plants that cannot fix atmospheric nitrogen.Sony VAIO VPCS11AVJ Battery

Nitrogen occurs naturally in many minerals, such as saltpetre (potassium nitrate), Chile saltpetre (sodium nitrate) and sal ammoniac (ammonium chloride). Most of these are uncommon, partly because of the minerals' ready solubility in water. See also Nitrate minerals and Ammonium minerals.Sony VAIO VPCS11J7E/B Battery

Compounds

The main neutral hydride of nitrogen is ammonia (NH3), although hydrazine (N2H4) is also commonly used. Ammonia is more basic than water by 6 orders of magnitude. Insolution ammonia forms the ammonium ion (NH+
4). Sony VAIO VPCS11M1E/W Battery

Liquid ammonia (boiling point 240 K) is amphiprotic (displaying either Brønsted-Lowry acidic or basic character) and forms ammonium and the less common amide ions (NH?
2); both amides and nitride (N3?) salts are known, but decompose in water. Singly, doubly, triply and quadruply substituted alkyl compounds of ammonia are called amines Sony VAIO VPCS11V9E Battery

(four substitutions, to form commercially and biologically important quaternary amines, results in a positively charged nitrogen, and thus a water-soluble, or at least amphiphilic, compound). Larger chains, rings and structures of nitrogen hydrides are also known, but are generally unstable.Sony VAIO VPCS11V9E/B Battery

Other classes of nitrogen anions (negatively charged ions) are the poisonous azides (N?
3), which are linear and isoelectronic to carbon dioxide, but which bind to important iron-containing enzymes in the body in a manner more resembling cyanide.Sony VAIO VPCS11X9E/B Battery

Another molecule of the same structure is the colorless and relatively inert anesthetic gas Nitrous oxide (dinitrogen monoxide, N2O), also known as laughing gas. This is one of a variety of nitrogen oxides that form a family often abbreviated as NOx.Sony VAIO VPCS123FGB Battery

Nitric oxide (nitrogen monoxide, NO), is a natural free radical used in signal transduction in both plants and animals, for example, in vasodilation by causing the smooth muscle of blood vessels to relax. The reddish and poisonous nitrogen dioxide NO2 contains an unpaired electron and is an important component ofsmog. Sony VAIO VPCS125EC Battery

Nitrogen molecules containing unpaired electrons show a tendency to dimerize (thus pairing the electrons), and are, in general, highly reactive. The corresponding acids are nitrous HNO2 and nitric acid HNO3, with the corresponding salts called nitrites and nitrates.Sony VAIO VPCS128EC Battery

The higher oxides dinitrogen trioxide N2O3, dinitrogen tetroxide N2O4 and dinitrogen pentoxide N2O5, are unstable and explosive, a consequence of the chemical stability of N2. Nearly every hypergolic rocket engine uses N2O4 as the oxidizer; their fuels, various forms of hydrazine, are also nitrogen compounds. Sony VAIO VPCS129GC Battery

These engines are extensively used on spacecraft such as the space shuttle and those of the Apollo Program because their propellants are liquids at room temperature and ignition occurs on contact without an ignition system, allowing many precisely controlled burns. Sony VAIO VPCS12C7E/B Battery

Some launch vehicles such as the Titan II and Ariane 1 through 4 also use hypergolic fuels, although the trend is away from such engines for cost and safety reasons. N2O4 is an intermediate in the manufacture of nitric acid HNO3, one of the few acids stronger than hydronium and a fairly strong oxidizing agent.Sony VAIO VPCS12L9E/B Battery

Nitrogen is notable for the range of explosively unstable compounds that it can produce. Nitrogen triiodide NI3 is an extremely sensitive contact explosive.Nitrocellulose, produced by nitration of cellulose with nitric acid, is also known as guncotton.Sony VAIO VPCS12V9E/B Battery

Nitroglycerin, made by nitration of glycerin, is the dangerously unstable explosive ingredient of dynamite. The comparatively stable, but more powerful explosive trinitrotoluene (TNT) is the standard explosive against which the power of nuclear explosions are measured.Sony VAIO VPCY115FGS Battery

Nitrogen can also be found in organic compounds. Common nitrogen functional groups include: amines, amides, nitro groups, imines, and enamines. The amount of nitrogen in a chemical substance can be determined by the Kjeldahl method.Sony VAIO VPCY115FX/BI Battery

Production and applications

Nitrogen gas is an industrial gas produced by the fractional distillation of liquid air, or by mechanical means using gaseous air (i.e., pressurized reverse osmosis membrane or Pressure swing adsorption). Commercial nitrogen is often a byproduct of air-processing for industrial concentration of oxygen for steelmaking and other purposes.Sony VAIO VPCY115FXBI Battery

When supplied compressed in cylinders it is often called OFN (oxygen-free nitrogen).

Nitrogen gas has a variety of applications, including serving as an inert replacement for air where oxidation is undesirable;

• As a modified atmosphere, pure or mixed with carbon dioxide, to preserve the freshness of packaged or bulk foods (by delaying rancidityand other forms of oxidative damage)Sony VAIO VPCY118EC Battery
• In ordinary incandescent light bulbs as an inexpensive alternative to argon.
• The production of electronic parts such as transistors, diodes, and integrated circuits
• Dried and pressurized, as a dielectric gas for high-voltage equipment
• The manufacturing of stainless steel
• Used in military aircraft fuel systems to reduce fire hazard, (see inerting system)
• On top of liquid explosives as a safety measure Sony VAIO VPCY118GX/BI Battery
• Filling automotive and aircraft tires due to its inertness and lack of moisture or oxidative qualities, as opposed to air. Growing in popularity for consumer vehicles due to ability to enhance fuel efficiency, increase tire longevity, and provide more safety and stability. Sony VAIO VPCY119FJ/S Battery
• This has not yet been independently verified in the case of consumer vehicles which don't have such high loads on their tires. The difference in N2 content between air and pure N2 is 20%
• Used as a propellant for draught wine, and as an alternative to or together with carbon dioxide for other beverages.Sony VAIO VPCY11AFJ Battery

Nitrogen is commonly used during sample preparation procedures for chemical analysis. To be specific, it is used to concentrate and reduce the volume of liquid samples. Directing a pressurized stream of nitrogen gas perpendicular to the surface of the liquid allows the solvent to evaporate while leaving the solute(s) and un-evaporated solvent behind.Sony VAIO VPCY11AGJ Battery

Nitrogen tanks are also replacing carbon dioxide as the main power source for paintball guns. The downside is that nitrogen must be kept at higher pressure than CO2, making N2 tanks heavier and more expensive.

Nitrogenated beer

A further example of its versatility is its use as a preferred alternative to carbon dioxide to pressurize kegs of some beers, Sony VAIO VPCY11AHJ Battery

in particular, stouts and Britishales, due to the smaller bubbles it produces, which make the dispensed beer smoother and headier. A modern application of a pressure sensitive nitrogen capsule known commonly as a "widget" now allows nitrogen charged beers to be packaged in cans and bottles.Sony VAIO VPCY11AVJ Battery

A mixture of nitrogen and carbon dioxide can be used for this purpose as well, to maintain the saturation of beer with carbon dioxide.

Liquid nitrogen

Liquid nitrogen is a cryogenic liquid. At atmospheric pressure, it boils at ?195.8 °C. When insulated in proper containers such as Dewar flasks, it can be transported without much evaporative loss.Sony VAIO VPCY11M1E/S Battery

Like dry ice, the main use of liquid nitrogen is as a refrigerant. Among other things, it is used in the cryopreservation of blood, reproductive cells (sperm and egg), and other biological samples and materials. It is used in the clinical setting incryotherapy to remove cysts and warts on the skin.Sony VAIO VPCY11S1E Battery

It is used in cold traps for certain laboratory equipment and to cool X-ray detectors. It has also been used to cool central processing units and other devices in computers that are overclocked, and that produce more heat than during normal operation.Sony VAIO VPCY11V9E/S Battery

Applications of nitrogen compounds

Molecular nitrogen (N2) in the atmosphere is relatively non-reactive due to its strong bond, and N2 plays an inert role in the human body, being neither produced nor destroyed. In nature, nitrogen is converted into biologically (and industrially) useful compounds by lightning, Sony VAIO VPCY218EC/BI Battery

and by some living organisms, notably certain bacteria (i.e. nitrogen fixing bacteria – see Biological role below). Molecular nitrogen is released into the atmosphere in the process of decay, in dead plant and animal tissues.

The ability to combine, or fix, molecular nitrogen is a key feature of modern industrial chemistry, where nitrogen and natural gas are converted into ammonia via theHaber process. Sony VAIO VPCY218EC/G Battery

Ammonia, in turn, can be used directly (primarily as a fertilizer, and in the synthesis of nitrated fertilizers), or as a precursor of many other important materials including explosives, largely via the production of nitric acid by the Ostwald process.

The organic and inorganic salts of nitric acid have been important historically as convenient stores of chemical energy.Sony VAIO VPCY218EC/L Battery

They include important compounds such aspotassium nitrate (or saltpeter used in gunpowder) and ammonium nitrate, an important fertilizer and explosive (see ANFO). Various other nitrated organic compounds, such as nitroglycerin, trinitrotoluene, and nitrocellulose, are used as explosives and propellants for modern firearms.Sony VAIO VPCY218EC/P Battery

Nitric acid is used as an oxidizing agent in liquid fueled rockets. Hydrazine and hydrazine derivatives find use as rocket fuels and monopropellants. In most of these compounds, the basic instability and tendency to burn or explode is derived from the fact that nitrogen is present as an oxide, and not as the far more stable nitrogen molecule (N2), which is a product of the compounds' thermal decomposition.Sony VAIO VPCY21S1E/L Battery

When nitrates burn or explode, the formation of the powerful triple bond in the N2 produces most of the energy of the reaction.

Nitrogen is a constituent of molecules in every major drug class in pharmacology and medicine. Nitrous oxide (N2O) was discovered early in the 19th century to be a partial anesthetic, though it was not used as a surgical anesthetic until later.Sony VAIO VPCY21S1E/P Battery

Called "laughing gas", it was found capable of inducing a state of social disinhibition resembling drunkenness. Other notable nitrogen-containing drugs are drugs derived from plant alkaloids, such as morphine (there exist many alkaloids known to have pharmacological effects; in some cases, they appear natural chemical defenses of plants against predation). Sony VAIO VPCY21S1E/SI Battery

Drugs that contain nitrogen include all major classes of antibiotics and organic nitrate drugs like nitroglycerin and nitroprusside that regulate blood pressure and heart action by mimicking the action ofnitric oxide.

Biological role

Nitrogen is an essential building block of amino and nucleic acids, essential to life on Earth.Sony VAIO VPCCW2S5C CN1 Battery

Elemental nitrogen in the atmosphere cannot be used directly by either plants or animals, and must be converted to a reduced (or 'fixed') state in order to be useful for higher plants and animals. Precipitation often contains substantial quantities of ammonium and nitrate, thought to result from nitrogen fixation by lightning and other atmospheric electric phenomena.Sony VAIO VPCEA20 Battery

This was first proposed by Liebig in 1827 and later confirmed. However, because ammonium is preferentially retained by the forest canopy relative to atmospheric nitrate, most fixed nitrogen reaches the soil surface under trees as nitrate. Soil nitrate is preferentially assimilated by tree roots relative to soil ammonium .Sony VAIO VPCEB10 Battery

Specific bacteria (e.g., Rhizobium trifolium) possess nitrogenase enzymes that can fix atmospheric nitrogen (see nitrogen fixation) into a form (ammonium ion) that is chemically useful to higher organisms. This process requires a large amount of energy and anoxic conditions. Sony VAIO VPCEB11FM Battery

Such bacteria may live freely in soil (e.g.,Azotobacter) but normally exist in a symbiotic relationship in the root nodules of leguminous plants (e.g. clover, Trifolium, or soybean plant, Glycine max). Nitrogen-fixing bacteria are also symbiotic with a number of unrelated plant species such as alders (Alnus) spp., lichens, Casuarina, Myrica, liverworts, andGunnera.Sony VAIO VPCEB11FM/BI Battery

As part of the symbiotic relationship, the plant converts the 'fixed' ammonium ion to nitrogen oxides and amino acids to form proteins and other molecules, (e.g.,alkaloids). In return for the 'fixed' nitrogen, the plant secretes sugars to the symbiotic bacteria. Legumes maintain an anaerobic (oxygen free) environment for their nitrogen-fixing bacteria.Sony VAIO VPCEB11FM/T Battery

Plants are able to assimilate nitrogen directly in the form of nitrates that may be present in soil from natural mineral deposits, artificial fertilizers, animal waste, or organic decay (as the product of bacteria, but not bacteria specifically associated with the plant). Nitrates absorbed in this fashion are converted to nitrites by the enzyme nitrate reductase, and then converted to ammonia by another enzyme called nitrite reductase.Sony VAIO VPCEB11FM/WI Battery

Nitrogen compounds are basic building blocks in animal biology as well. Animals use nitrogen-containing amino acids from plant sources as starting materials for all nitrogen-compound animal biochemistry, including the manufacture of proteins and nucleic acids. Sony VAIO VPCEB11FX Battery

Plant-feeding insects are dependent on nitrogen in their diet, such that varying the amount of nitrogen fertilizer applied to a plant can affect the reproduction rate of insects feeding on fertilized plants.

Soluble nitrate is an important limiting factor in the growth of certain bacteria in ocean waters.Sony VAIO VPCEB11FX/BI Battery

In many places in the world, artificial fertilizers applied to crop-lands to increase yields result in run-off delivery of soluble nitrogen to oceans at river mouths. This process can result in eutrophication of the water, as nitrogen-driven bacterial growth depletes water oxygen to the point that all higher organisms die. Sony VAIO VPCEB11FX/T Battery

Well-known "dead zone" areas in the U.S. Gulf Coast and the Black Sea are due to this important polluting process.

Many saltwater fish manufacture large amounts of trimethylamine oxide to protect them from the high osmotic effects of their environment; conversion of this compound to dimethylamine is responsible for the early odor in unfresh saltwater fish.Sony VAIO VPCEB11FX/WI Battery

In animals, free radical nitric oxide (NO) (derived from an amino acid), serves as an important regulatory molecule for circulation.

Animal metabolism of NO results in production of nitrite. Animal metabolism of nitrogen in proteins, in general, results in excretion of urea, while animal metabolism of nucleic acids results in excretion of urea and uric acid. Sony VAIO VPCEB11GX Battery

The characteristic odor of animal flesh decay is caused by the creation of long-chain, nitrogen-containing amines, such as putrescine and cadaverine, which are breakdown products of the amino acids ornithine and lysine, respectively, in decaying proteins.

Decay of organisms and their waste products may produce small amounts of nitrate, but most decay eventually returns nitrogen content to the atmosphere, as molecular nitrogen.Sony VAIO VPCEB11GX/BI Battery

The circulation of nitrogen from atmosphere, to organic compounds, then back to the atmosphere, is referred to as the nitrogen cycle.

Safety

Rapid release of nitrogen gas into an enclosed space can displace oxygen, and therefore represents an asphyxiation hazard. Sony VAIO VPCEB11GX/T Battery

This may happen with few warning symptoms, since the human carotid body is a relatively slow and a poor low-oxygen (hypoxia) sensing system. An example occurred shortly before the launch of the first Space Shuttle mission in 1981, when two technicians lost consciousness (and one of them died) after they walked into a space located in the Shuttle's Mobile Launcher Platform that was pressurized with pure nitrogen as a precaution against fire. Sony VAIO VPCEB11GX/WI Battery

The technicians would have been able to exit the room if they had experienced early symptoms from nitrogen-breathing.

When inhaled at high partial pressures (more than about 4 bar, encountered at depths below about 30 m in scuba diving), nitrogen begins to act as an anesthetic agent. It can cause nitrogen narcosis, a temporary semi-anesthetized state of mental impairment similar to that caused by nitrous oxide.Sony VAIO VPCEB12FX Battery

Nitrogen also dissolves in the bloodstream and body fats. Rapid decompression (in particular, in the case of divers ascending too quickly, or astronauts decompressing too quickly from cabin pressure to spacesuit pressure) can lead to a potentially fatal condition called decompression sickness (formerly known as caisson sickness or the bends), Sony VAIO VPCEB12FX/BI Battery

when nitrogen bubbles form in the bloodstream, nerves, joints, and other sensitive or vital areas.Other "inert" gases (those gases other than carbon dioxide and oxygen) cause the same effects from bubbles composed of them, so replacement of nitrogen in breathing gases may prevent nitrogen narcosis, but does not prevent decompression sickness.Sony VAIO VPCEB12FX/BIC Battery

Direct skin contact with liquid nitrogen will cause severe frostbite (cryogenic "burns"). This may happen almost instantly on contact, or after a second or more, depending on the form of liquid nitrogen. Bulk liquid nitrogen causes less rapid freezing than a spray of nitrogen mist (such as is used to freeze certain skin growths in the practice of dermatology). Sony VAIO VPCEB12FX/T Battery

The extra surface area provided by nitrogen-soaked materials is also important, with soaked clothing or cotton causing far more rapid damage than a spill of direct liquid to skin. Full "contact" between naked skin and large collected-droplets or pools of liquid nitrogen may be prevented for a second or two, by a layer of insulating gas from the Leidenfrost effect. Sony VAIO VPCEB14FX Battery

This may give the skin a second of protection from nitrogen bulk liquid. However, liquid nitrogen applied to skin in mists, and on fabrics, bypasses this effect, and causes local frostbite immediately.

Nitrogen asphyxiation is an occasional cause of accidental death and a theoretical method of capital punishment advocated in a National Review article, "Killing with kindness – capital punishment by nitrogen asphyxiation" (Creque 1995). Sony VAIO VPCEB14FX/BI Battery

The painful experience of suffocation is not caused by lack of oxygen, but rather because of a buildup of carbon dioxide in the bloodstream which is exhaled under normal circumstances.

When humans breathe in pure nitrogen, they exhale carbon dioxide without resupplying oxygen. Nitrogen is a colorless, odorless and tasteless gas that constitutes approximately 78 percent of the Earth's atmosphere.Sony VAIO VPCEB14FX/T Battery

As such, the subject would detect no abnormal sensation. This leads to asphyxiation without the painful and traumatic feeling of suffocation. Because of this property, nitrogen in Hebrew is called ???? ("asphyxiator"),in German is called "Stickstoff", in Dutch "stikstof", ("suffocation matter") - Sony VAIO VPCEB14FX/WI Battery

the Scandinavian languages call it "kväve", "kvælstof" and "kvelstoff" from "kväva/kvele/kvæle" ("to asphyxiate"), in Russian "????" ("not life-friendly"), in Croatian "dušik" (from the now archaic word "dušiti", meaning "to asphyxiate").

For this reason, accidental nitrogen asphyxiation is a possible hazard where large quantities of nitrogen are used.Sony VAIO VPCEB15FM Battery

Also, deliberate nitrogen asphyxiation is viewed by some as a more humane way to end a human life in a controlled setting. As the principal component in air, nitrogen poses no significant risk upon discharge.

As an execution method

Although execution by nitrogen asphyxiation was discussed briefly in print in 1995 (Creque), it is not used by any nation.Sony VAIO VPCEB15FM/BI Battery

In a televised documentary in 2007, the UK political commentator (and former Member of Parliament United Kingdom), Michael Portillo examined execution techniques in use around the world and found them unsatisfactory; his conclusion was that nitrogen asphyxiation would be the best method.Sony VAIO VPCEB15FM/T Battery

Accidental deaths

Accidental nitrogen asphyxiation causes about 8 deaths per year in the United States, which is asserted to be more than from any other industrial gas. For example in 1981, shortly before the launch of the first Space Shuttle mission, two technicians lost consciousness and one of them died after they entered the Orbiter aft compartment which was pressurized with pure nitrogen as a precaution against fire. Sony VAIO VPCEB15FM/WI Battery

A laboratory assistant died in Scotland in 1999, apparently from asphyxiation, after liquid nitrogen spilled in a basement storage room.

Physiology

A typical human breathes between 12 and 20 times per minute at a rate primarily influenced by carbon dioxide concentration, and thus pH, in the blood. Sony VAIO VPCEB15FX Battery

With each breath, a volume of about 0.6 liters is exchanged from an active lung volume (tidal volume + functional residual capacity) of about 3 liters. Normal Earth atmosphereis about 78 percent nitrogen, 21 percent oxygen, and 1 percent argon, carbon dioxide, and other gases. Sony VAIO VPCEB15FX/BI Battery

After just two or three breaths of nitrogen, the oxygen concentration in the lungs would be low enough for some oxygen already in the bloodstream to exchange back to the lungs and be eliminated by exhalation. Crude simulation of oxygen transport through the lungs and blood stream suggests that the partial pressure of oxygen in arterial blood would be about 50 percent of saturation 1 minute after switching gases and would reach zero within 3 minutes.Sony VAIO VPCEB15FX/T Battery

Unconsciousness in cases of accidental asphyxia can occur within 1 minute. Loss of consciousness results from critical hypoxia, when arterial oxygen saturation is less than 60% (Fisher n.d.). “At oxygen concentrations [in air] of 4 to 6%, there is loss of consciousness in 40 seconds and death within a few minutes” (DiMaio & DiMaio 2001:231).Sony VAIO VPCEB15FX/WI Battery

As this procedure provides an atmosphere completely devoid of oxygen, the sequence of effects should be expected to occur even more quickly. At an altitude greater than 43,000 ft (13,000 m), where the ambient oxygen concentration is equivalent to 3.6% at sea level, an average individual is able to perform flying duties efficiently for only 9 to 12 seconds without oxygen supplementation (Fisher n.d.). Sony VAIO VPCEB16FX Battery

The US Air Force trains air crews to recognize their individual subjective signs of approaching hypoxia. Some individuals experience headache, dizziness, fatigue, nausea, or euphoria, but some become unconscious without warning (Fisher n.d.). Equivalent training is unlikely for a condemned individual, making unconsciousness without warning probable, although as much as a 30 second warning is possible.Sony VAIO VPCEB16FX/B Battery

Loss of consciousness may be accompanied by convulsions (Fisher n.d.) and is followed by cyanosis and cardiac arrest. About 7 minutes of oxygen deprivation causesdeath of the cerebral cortex and presumably the medulla oblongata, which controls breathing and heart action.Sony VAIO VPCEB16FX/G Battery

A nutrient is a chemical that an organism needs to live and grow or a substance used in an organism's metabolism which must be taken in from its environment. They are used to build and repair tissues, regulate body processes and are converted to and used as energy. Sony VAIO VPCEB16FX/L Battery

Methods for nutrient intake vary, with animals and protists consuming foods that are digested by an internal digestive system, but most plants ingest nutrients directly from the soil through their roots or from the atmosphere.

Organic nutrients include carbohydrates, fats, proteins (or their building blocks, amino acids), and vitamins. Sony VAIO VPCEB16FX/P Battery

Inorganic chemical compounds such as dietary minerals, water, and oxygen may also be considered nutrients. A nutrient is said to be "essential" if it must be obtained from an external source, either because the organism cannot synthesize it or produces insufficient quantities. Sony VAIO VPCEB16FX/W Battery

Nutrients needed in very small amounts are micronutrients and those that are needed in larger quantities are called macronutrients. The effects of nutrients are dose-dependent and shortages are called deficiencies.

See healthy diet for more information on the role of nutrients in human nutrition.Sony VAIO VPCEB17FX Battery

Macronutrients is defined in several different ways.

• The chemical elements humans consume in the largest quantities are carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulphur, or CHNOPS.Sony VAIO VPCEB17FX/B Battery
• The classes of chemical compounds humans consume in the largest quantities and which provide bulk energy are carbohydrates, proteins, and fats. Water and atmospheric oxygen also must be consumed in large quantities, but are not always considered "food" or "nutrients".Sony VAIO VPCEB17FX/G Battery
• Calcium, salt (sodium and chloride), magnesium, and potassium (along with phosphorus and sulfur) are sometimes added to the list of macronutrients because they are required in large quantities compared to other vitamins and minerals. They are sometimes referred to as the macrominerals.Sony VAIO VPCEB17FX/L Battery

Substances that provide energy

• Carbohydrates are compounds made up of types of sugars. Carbohydrates are classified by their number of sugar units: monosaccharides (such as glucose andfructose), disaccharides (such as sucrose and lactose), oligosaccharides, and polysaccharides (such as starch, glycogen, and cellulose).Sony VAIO VPCEB17FX/P Battery
• Proteins are organic compounds that consist of the amino acids joined by peptide bonds. The body cannot manufacture some of the amino acids (termed essential amino acids); the diet must supply these. In nutrition, proteins are broken down through digestion by proteases back into free amino acids.Sony VAIO VPCEB17FX/W Battery
• Fats consist of a glycerin molecule with three fatty acids attached. Fatty acids are unbranched hydrocarbon chains, connected by single bonds alone (saturated fatty acids) or by both double and single bonds (unsaturated fatty acids). Fats are needed to keep cell membranes functioning properly,Sony VAIO VPCEB190X Battery
• to insulate body organs against shock, to keep body temperature stable, and to maintain healthy skin and hair. The body does not manufacture certain fatty acids (termed essential fatty acids) and the diet must supply these.

Fat has an energy content of 9 kcal/g (~37.7 kJ/g); proteins and carbohydrates 4 kcal/g (~16.7 kJ/g). Ethanol (grain alcohol) has an energy content of 7 kcal/g (~29.3 kJ/g).Sony VAIO VPCEB19FX Battery

Substances that support metabolism

• Dietary minerals are generally trace elements, salts, or ions such as copper and iron. Some of these minerals are essential to human metabolism.
• Vitamins are organic compounds essential to the body. They usually act as coenzymes or cofactors for various proteins in the body.Sony VAIO VPCEB19GX Battery
• Water is an essential nutrient and is the solvent in which all the chemical reactions of life take place.

Plants absorb nutrients from the soil or the atmosphere, or from water (mainly aquatic plants) an exception are the carnivorous plants, which externally digest nutrients from animals, before ingesting them.Sony VAIO VPCEB1AFX Battery

The chemical elements consumed in the greatest quantities by plants are carbon, hydrogen, and oxygen. These are present in the environment in the form of water and carbon dioxide; energy is provided bysunlight. Nitrogen, phosphorus, and sulfur are also needed in relatively large quantities.Sony VAIO VPCEB1AFX/B Battery

Together, the "Big Six" are the elemental macronutrients for all organisms, often represented by the acronymCHNOPS. Usually they are sourced from inorganic (e.g. carbon dioxide, water, nitrate, phosphate,sulfate) or organic (e.g. carbohydrates, lipids, proteins) compounds, although elemental diatomic molecules of nitrogen and (especially) oxygen are often used.Sony VAIO VPCEB1AGX Battery

Other chemical elements are also necessary to carry out various life processes and build structures; seefertilizer and micronutrient for more information.

Some of these are considered macronutrients in certain organisms. Sony VAIO VPCEB1AGX/BI Battery

The mnemonic C. HOPKiN'S CaFe Mg (to be used as C. Hopkins coffee mug) is used by some students to remember the list as: carbon, hydrogen,oxygen, phosphorus, potassium, nitrogen, sulfur, calcium, iron, and magnesium. Silicon, chloride,sodium, copper, zinc, and molybdenum are sometimes also included, but are in other cases consideredmicronutrients.Sony VAIO VPCEB1BGX Battery

Essential and non-essential nutrients

Nutrients are frequently categorized as essential or nonessential. Essential nutrients are unable to be synthesized internally (either at all, or in sufficient quantities), and so must be consumed by an organism from its environment.Nonessential nutrients are those nutrients that can be made by the body, they may often also be absorbed from consumed food.Sony VAIO VPCEB1BGX/BI Battery

The majority of animals ultimately derive their essential nutrients from plants, though some animals may consume mineral-based soils to supplement their diet.

For humans, these include essential fatty acids, essential amino acids, vitamins, and certain dietary minerals. Oxygen and water are also essential for human survival, but are generally not considered "food" when consumed in isolation.Sony VAIO VPCEB1CGX Battery

Humans can derive energy from a wide variety of fats, carbohydrates, proteins, and ethanol, and can synthesize other needed amino acids from the essential nutrients.

Non-essential substances within foods can still have a significant impact on health, whether beneficial or toxic. Sony VAIO VPCEB1CGX/BI Battery

For example, most dietary fiber is not absorbed by the human digestive tract, but is important in digestion and absorption of otherwise harmful substances. Interest has recently increased in phytochemicals, which include many non-essential substances which may have health benefits.Sony VAIO VPCEB1DGX Battery

Deficiencies and toxicity

An inadequate amount of a nutrient is a deficiency. Deficiencies can be due to a number of causes including inadequacy in nutrient intake called dietary deficiency, or conditions that interfere with the utilization of a nutrient within an organism.Sony VAIO VPCEB1DGX/BI Battery

Some of the conditions that can interfere with nutrient utilization include problems with nutrient absorption, substances that cause a greater than normal need for a nutrient, conditions that cause nutrient destruction, and conditions that cause greater nutrient excretion.Sony VAIO VPCEB1EGX Battery

Nutrient toxicity occurs when an excess of a nutrient does harm to an organism.

In plants five types of deficiency or toxicity symptoms are common:

• Chlorosis - which is the yellowing of plant tissue caused by a shortage of chlorophyll synthesis.
• Necrosis - which is the death of plant tissue.Sony VAIO VPCEB1EGX/BI Battery
• Accumulation of anthocynanin - which produces a purple or reddish colorization of foliage and/or stems.
• Lack of new growth.
• Stunting or reduced growth - where new growth is stunted or reduced.Sony VAIO VPCEB1FGX Battery

Oversupply of plant nutrients in the environment can cause excessive plant and algae growth. Eutrophication, as this process is called, may cause imbalances in population numbers and other nutrients that can be harmful to certain species. For example, an algal bloom can deplete the oxygen available for fish to breathe. Causes include water pollution from sewage or runoff from farms (carrying excess agricultural fertilizer). Sony VAIO VPCEB1FGX/BI Battery

Nitrogen and phosphorus are most commonly the limiting factor in growth, and thus the most likely to trigger eutrophication when introduced artificially.

Reactive nitrogen species (RNS) are a family of antimicrobial molecules derived from nitric oxide Sony VAIO VPCEB1GGX Battery

(·NO) and superoxide (O2·?) produced via the enzymatic activity of inducible nitric oxide synthase 2 (NOS2) and NADPH oxidase respectively. NOS2 is expressed primarily in macrophages after induction bycytokines and microbial products, notably interferon-gamma (IFN-?) and lipopolysaccharide (LPS).Sony VAIO VPCEB1GGX/BI Battery

Reactive nitrogen species act together with reactive oxygen species (ROS) to damage cells, causingnitrosative stress. Therefore, these two species are often collectively referred to as ROS/RNS.

Reactive nitrogen species are also continuously produced in plants as by-products of aerobic metabolismor in response to stress.Sony VAIO VPCEB1HGX Battery

Types

RNS are produced in animals starting with the reaction of nitric oxide (·NO) with superoxide (O2·?) to form peroxynitrite (ONOO?):

• ·NO (nitric oxide) + O2·? (super oxide) ? ONOO? (peroxynitrite)

Superoxide anion (O2-) is a reactive oxygen species that reacts quickly with nitric oxide (NO) in the vasculature. Sony VAIO VPCEB1HGX/BI Battery

The reaction produces peroxynitrite and depletes the bioactivity of NO. This is important because NO is a key mediator in many important vascular functions including regulation of smooth muscle tone and blood pressure, platelet activation, and vascular cell signaling.Sony VAIO VPCEB1JFX Battery

Peroxynitrite itself is a highly reactive species which can directly react with various biological targets and components of the cell including lipids, thiols, amino acid residues, DNA bases, and low-molecular weight antioxidants. However, these reactions happen at a relatively slow rate. This slow reaction rate allows it to react more selectively throughout the cell. Sony VAIO VPCEB1JFX/B Battery

Peroxynitrite is able to get across cell membranes to some extent through anion channels. Additionally peroxynitrite can react with other molecules to form additional types of RNS including nitrogen dioxide (·NO2) and dinitrogen trioxide (N2O3) as well as other types of chemically reactivefree radicals. Important reactions involving RNS include:Sony VAIO VPCEB1JFX/G Battery

• ONOO? + H+ ? ONOOH (peroxynitrous acid) ? ·NO2 (nitrogen dioxide) + ·OH (hydroxyl radical)
• ONOO? + CO2 (carbon dioxide) ? ONOOCO2? (nitrosoperoxycarbonate)
• ONOOCO2? ? ·NO2 (nitrogen dioxide) + O=C(O·)O? (carbonate radical)
• ·NO + ·NO2 N2O3 (dinitrogen trioxide) Sony VAIO VPCEB1JFX/L Battery

Biological targets

Peroxynitrite can react directly with proteins that contain transition metal centers. Therefore, it can modify proteins such as hemoglobin, myoglobin, and cytochrone c by oxidizing ferrous heme into its corresponding ferric forms. Sony VAIO VPCEB1JFX/P Battery

Peroxynitrite may also be able to change protein structure through the reaction with various amino acids in the peptide chain. The most common reaction with amino acids is cysteine oxidation. Another reaction is tyrosine nitration; however peroxynitrite does not react directly with tyrosine.Sony VAIO VPCEB1JFX/W Battery

Tyrosine reacts with other RNS that are produced by peroxynitrite. All of these reactions affect protein structure and function and thus have the potential to cause changes in the catalytic activity of enzymes, altered cytoskeletal organization, and impaired cell signal transduction.Sony VAIO VPCEB1KGX Battery

Liquid nitrogen is nitrogen in a liquid state at a very low temperature. It is produced industrially by fractional distillationof liquid air. Liquid nitrogen is a colourless clear liquid with density of 0.807 g/mL at its boiling point and a dielectric constant of 1.4. Liquid nitrogen is often referred to by the abbreviation, LN2 or "LIN" or "LN" and has the UN number1977.Sony VAIO VPCEB1KGX/B Battery

At atmospheric pressure, liquid nitrogen boils at 77K (-196°C; -321°F) and is a cryogenic fluid which can cause rapid freezingon contact with living tissue, which may lead to frostbite. When appropriately insulated from ambient heat, liquid nitrogen can be stored and transported, for example in vacuum flasks. Sony VAIO VPCEB1KGX/W Battery

Here, the very low temperature is held constant at 77 K by slow boiling of the liquid, resulting in the evolution of nitrogen gas. Depending on the size and design, the holding time of vacuum flasks ranges from a few hours to a few weeks.

Liquid nitrogen can easily be converted to the solid by placing it in a vacuum chamber pumped by a rotary vacuum pump.Sony VAIO VPCEB1LFX Battery

Liquid nitrogen freezes at 63 K (?210 °C; ?346 °F). Despite its reputation, liquid nitrogen's efficiency as a coolant is limited by the fact that it boils immediately on contact with a warmer object, enveloping the object in insulating nitrogen gas. This effect, known as the Leidenfrost effect, applies to any liquid in contact with an object significantly hotter than its boiling point.Sony VAIO VPCEB1LFX/BI Battery

More rapid cooling may be obtained by plunging an object into a slush of liquid and solid nitrogen than into liquid nitrogen alone.

Nitrogen was first liquefied at the Jagiellonian University on 15 April 1883 by Polish physicists, Zygmunt Wróblewski and Karol Olszewski.Sony VAIO VPCEB1LFX/WI Battery

Liquid nitrogen is a compact and readily transported source of nitrogen gas without pressurization. Further, its ability to maintain temperatures far below the freezing point of water makes it extremely useful in a wide range of applications, primarily as an open-cycle refrigerant, including:Sony VAIO VPCEB1MFX Battery

• in cryotherapy for removing unsightly or potentially malignant skin lesions such as warts and actinic keratosis
• as a coolant for CCD cameras in astronomy
• to store cells at low temperature for laboratory work
• in cryogenics
• as a source of very dry nitrogen gas Sony VAIO VPCEB1MFX/BI Battery
• for the immersion freezing and transportation of food products
• for the cryopreservation of blood, reproductive cells (sperm and egg), and other biological samples and materials
• as a method of freezing water pipes in order to work on them in situations where a valve is not available to block water flow to the work area Sony VAIO VPCEB1NFX Battery
• in the process of promession, a way to dispose of the dead
• for cooling a high-temperature superconductor to a temperature sufficient to achieve superconductivity
• for the cryonic preservation in the hope of future reanimation.
• to preserve tissue samples from surgical excisions for future studies
• to shrink-weld machinery parts together Sony VAIO VPCEB1NFX/B Battery
• as a coolant for vacuum pump traps and in controlled-evaporation processes in chemistry.
• as a coolant to increase the sensitivity of infrared homing seeker heads of missiles such as the Strela 3
• as a coolant to temporarily shrink mechanical components during machine assembly and allow improved interference fits
• as a coolant for computers Sony VAIO VPCEB1NFX/L Battery
• in food preparation, such as for making ultra-smooth ice cream.

Safety

Since the liquid to gas expansion ratio of nitrogen is 1:694 at 20C, a tremendous amount of force can be generated if liquid nitrogen is rapidly vaporized. Sony VAIO VPCEB1NFX/P Battery

In an incident in 2006 at Texas A&M University, the pressure-relief devices of a tank of liquid nitrogen were malfunctioning and later sealed. As a result of the subsequent pressure buildup, the tank failed catastrophically and exploded. The force of the explosion was sufficient to propel the tank through the ceiling immediately above it.Sony VAIO VPCEB1NFX/W Battery

Because of its extremely low temperature, careless handling of liquid nitrogen may result in cold burns.

As liquid nitrogen evaporates it will reduce the oxygen concentration in the air and might act as an asphyxiant, especially in confined spaces. Nitrogen is odorless, colorless and tasteless, and may produce asphyxia without any sensation or prior warning.Sony VAIO VPCEB1PFX Battery

A laboratory assistant died in Scotland in 1999, apparently from asphyxiation, possibly caused by liquid nitrogen spilled in a basement storage room.

Vessels containing liquid nitrogen can condense oxygen from air. The liquid in such a vessel becomes increasingly enriched in oxygen (boiling point = 90 K) as the nitrogen evaporates, and can cause violent oxidation of organic material.Sony VAIO VPCEB1PFX/B Battery

The nitrogen cycle is the process by which nitrogen is converted between its various chemical forms. This transformation can be carried out by both biological and non-biological processes. Important processes in the nitrogen cycle include fixation, mineralization, nitrification, and denitrification. Sony VAIO VPCEB1QGX Battery

The majority of Earth's atmosphere (approximately 78%) is nitrogen, making it the largest pool of nitrogen. However, atmospheric nitrogen has limited availability for biological use, leading to a scarcity of usable nitrogen in many types of ecosystems. Sony VAIO VPCEB1QGX/BI Battery

The nitrogen cycle is of particular interest to ecologists because nitrogen availability can affect the rate of key ecosystem processes, including primary production and decomposition. Human activities such as fossil fuel combustion, use of artificial nitrogen fertilizers, and release of nitrogen in wastewater have dramatically altered the global nitrogen cycle.Sony VAIO VPCEB1RGX Battery

A 2011 study has cast doubt on the traditional model of the nitrogen cycle described below; nitrogen from rocks may also be a significant source not previously included.

Ecological function

Nitrogen is essential for many processes; it is crucial for any life on Earth. It is a component in all amino acids, as incorporated into proteins, and is present in the bases that make up nucleic acids, such as DNA and RNA. Sony VAIO VPCEB1RGX/BI Battery

In plants, much of the nitrogen is used in chlorophyll molecules, which are essential for photosynthesisand further growth. Although Earth’s atmosphere is an abundant source of nitrogen, most is relatively unusable by plants. Chemical processing, or naturalfixation (through processes such as bacterial conversion—see rhizobium), are necessary to convert gaseous nitrogen into forms usable by living organisms, which makes nitrogen a crucial component of food production. Sony VAIO VPCEB20 Battery

The abundance or scarcity of this "fixed" form of nitrogen, (also known as reactive nitrogen), dictates how much food can be grown on a piece of land.

The processes of the nitrogen cycle

Nitrogen is present in the environment in a wide variety of chemical forms including organic nitrogen, ammonium (NH4+), nitrite (NO2-), nitrate (NO3-), nitrous oxide(N2O), nitric oxide (NO) or inorganic nitrogen gas (N2).Sony VAIO VPCEC20 Battery

Organic nitrogen may be in the form of a living organism, humus or in the intermediate products of organic matter decomposition. The processes of the nitrogen cycle transform nitrogen from one form to another. Many of those processes are carried out by microbes, either in their effort to harvest energy or to accumulate nitrogen in a form needed for their growth. Sony VAIO VPCEE20 Battery

The diagram above shows how these processes fit together to form the nitrogen cycle.

Nitrogen fixation

Atmospheric nitrogen must be processed, or "fixed" (see page on nitrogen fixation), to be used by plants. Some fixation occurs in lightning strikes, but most fixation is done by free-living or symbiotic bacteria.Sony VAIO VPCEF20 Battery

These bacteria have the nitrogenase enzyme that combines gaseous nitrogen with hydrogen to produce ammonia, which is then further converted by the bacteria to make their own organic compounds. Most biological nitrogen fixation occurs by the activity of Mo-nitrogenase, found in a wide variety of bacteria and some Archaea. Sony VAIO VPCF112FX/B Battery

Mo-nitrogenase is a complex two component enzyme that has multiple metal-containing prosthetic groups. Some nitrogen fixing bacteria, such as Rhizobium, live in the root nodules of legumes (such as peas or beans). Here they form a mutualistic relationship with the plant, producing ammonia in exchange for carbohydrates. Sony VAIO VPCF115FG/B Battery

Nutrient-poor soils can be planted with legumes to enrich them with nitrogen. A few other plants can form suchsymbioses. Today, about 30% of the total fixed nitrogen is manufactured in ammonia chemical plants.

Conversion of N2

The conversion of nitrogen (N2) from the atmosphere into a form readily available to plants and hence to animals and humans is an important step in the nitrogen cycle, which distributes the supply of this essential nutrient. Sony VAIO VPCF116FGBI Battery

There are four ways to convert N2 (atmospheric nitrogen gas) into more chemically reactive forms:

1. Biological fixation: some symbiotic bacteria (most often associated with leguminous plants) and some free-living bacteria are able to fix nitrogen as organic nitrogen. An example of mutualistic nitrogen fixing bacteria are the Rhizobium bacteria, which live in legume root nodules. These species are diazotrophs. An example of the free-living bacteria is Azotobacter.Sony VAIO VPCF117FJ/W Battery
2. Industrial N-fixation: Under great pressure, at a temperature of 600 C, and with the use of an iron catalyst, hydrogen (usually derived from natural gas or petroleum) and atmospheric nitrogen can be combined to form ammonia (NH3) in the Haber-Bosch process which is used to make fertilizer and explosives.Sony VAIO VPCF117HG/BI Battery
3. Combustion of fossil fuels: automobile engines and thermal power plants, which release various nitrogen oxides (NOx).
4. Other processes: In addition, the formation of NO from N2 and O2 due to photons and especially lightning, can fix nitrogen.Sony VAIO VPCF118FJ/W Battery

Assimilation

Plants take nitrogen from the soil, by absorption through their roots in the form of either nitrate ions or ammonium ions. All nitrogen obtained by animals can be traced back to the eating of plants at some stage of the food chain.Sony VAIO VPCF119FC Battery

Plants can absorb nitrate or ammonium ions from the soil via their root hairs. If nitrate is absorbed, it is first reduced to nitrite ions and then ammonium ions for incorporation into amino acids, nucleic acids, and chlorophyll. In plants that have a mutualistic relationship with rhizobia, some nitrogen is assimilated in the form of ammonium ions directly from the nodules. Sony VAIO VPCF119FC/BI Battery

Animals, fungi, and other heterotrophic organisms obtain nitrogen by ingestion of amino acids, nucleotides and other small organic molecules.

Ammonification

When a plant or animal dies, or an animal expels waste, the initial form of nitrogen is organic. Bacteria, or fungi in some cases, convert the organic nitrogen within the remains back into ammonium (NH4+), a process called ammonification or mineralization.Sony VAIO VPCF119FJ/BI Battery

Enzymes Involved:

• GS: Gln Synthetase (Cytosolic & PLastid)
• GOGAT: Glu 2-oxoglutarate aminotransferase (Ferredoxin & NADH dependent)
• GDH: Glu Dehydrogenase:
  • Minor Role in ammonium assimilation.
  • Important in amino acid catabolism. Sony VAIO VPCF11AFJ Battery

Nitrification

The conversion of ammonium to nitrate is performed primarily by soil-living bacteria and other nitrifying bacteria. In the primary stage of nitrification, the oxidation of ammonium (NH4+) is performed by bacteria such as the Nitrosomonas species, which converts ammonia to nitrites (NO2-). Sony VAIO VPCF11AGJ Battery

Other bacterial species, such as the Nitrobacter, are responsible for the oxidation of the nitrites into nitrates (NO3-). It is important for the nitrites to be converted to nitrates because accumulated nitrites are toxic to plant life.

Due to their very high solubility, nitrates can enter groundwater. Sony VAIO VPCF11AHJ Battery

Elevated nitrate in groundwater is a concern for drinking water use because nitrate can interfere with blood-oxygen levels in infants and cause methemoglobinemia or blue-baby syndrome. Where groundwater recharges stream flow, nitrate-enriched groundwater can contribute to eutrophication, a process that leads to high algal, especially blue-green algal populations and the death of aquatic life due to the algae's excessive demand for oxygen. Sony VAIO VPCF11JFX/B Battery

While not directly toxic to fish life, like ammonia, nitrate can have indirect effects on fish if it contributes to this eutrophication. Nitrogen has contributed to severe eutrophication problems in some water bodies. Since 2006, the application of nitrogen fertilizer has been increasingly controlled in Britain and the United States. Sony VAIO VPCF11M1E Battery

This is occurring along the same lines as control of phosphorus fertilizer, restriction of which is normally considered essential to the recovery of eutrophied waterbodies.

Denitrification

Denitrification is the reduction of nitrates back into the largely inert nitrogen gas (N2), completing the nitrogen cycle. Sony VAIO VPCF11M1E/H Battery

This process is performed by bacterial species such as Pseudomonas and Clostridium in anaerobic conditions. They use the nitrate as an electron acceptor in the place of oxygen during respiration. These facultatively anaerobic bacteria can also live in aerobic conditions.Sony VAIO VPCF11MFX/B Battery

Anaerobic ammonium oxidation

In this biological process, nitrite and ammonium are converted directly into elemental nitrogen (N2) gas. This process makes up a major proportion of elemental nitrogen conversion in the oceans.

Marine nitrogen cycle

The nitrogen cycle is an important process in the ocean as well. While the overall cycle is similar, there are different players and modes of transfer for nitrogen in the ocean.Sony VAIO VPCF11S1E Battery

Nitrogen enters the water through precipitation, runoff, or as N2 from the atmosphere. Nitrogen cannot be utilized by phytoplankton as N2 so it must undergo nitrogen fixation which is performed predominately by cyanobacteria. Without supplies of fixed nitrogen entering the marine cycle the fixed nitrogen would be used up in about 2000 years. Sony VAIO VPCF11S1E/B Battery

Phytoplankton need nitrogen in biologically available forms for the initial synthesis of organic matter. Ammonia and urea are released into the water by excretion from plankton. Nitrogen sources are removed from the euphotic zone by the downward movement of the organic matter. Sony VAIO VPCF11Z1E Battery

This can occur from sinking of phytoplankton, vertical mixing, or sinking of waste of vertical migrators. The sinking results in ammonia being introduced at lower depths below the euphotic zone. Bacteria are able to convert ammonia to nitrite and nitrate but they are inhibited by light so this must occur below the euphotic zone.Sony VAIO VPCF11Z1E/BI Battery

Ammonification or Mineralization is performed by bacteria to convert the ammonia to ammonium. Nitrification can then occur to convert the ammonium to nitrite and nitrate. Nitrate can be returned to the euphotic zone by vertical mixing and upwelling where it can be taken up by phytoplankton to continue the cycle. N2 can be returned to the atmosphere through denitrification.Sony VAIO VPCF11ZHJ Battery

NH4+ is thought to be the preferred source of fixed nitrogen for phytoplankton because its assimilation does not involve a redox reaction and therefore requires little energy. However NO3 is more abundant so most phytoplankton have adapted to have the enzymes necessary to undertake this reduction (nitrate reductase). Sony VAIO VPCF127HGBI Battery

There are a few notable and well-known exceptions that include Prochlorococcus and some Synechococcus. These species can only take up nitrogen as NH4+.

The nutrients in the ocean are not uniformly distributed. Areas of upwelling provide supplies of nitrogen from below the euphotic zone. Sony VAIO VPCF137HG/BI Battery

Coastal zones provide nitrogen from runoff and upwelling occurs readily along the coast. However, the rate at which nitrogen can be taken up by phytoplankton is decreased in oligotrophicwaters all year-round and temperate water in the summer resulting in lower primary production. The distribution of the different forms of nitrogen varies throughout the oceans as well.Sony VAIO VPC-P111KX/B Battery

Nitrate is depleted in near-surface water except in upwelling regions. Coastal upwelling regions usually have high nitrate and chlorophyll levels as a result of the increased production. However, there are regions of high surface nitrate but low chlorophyll that are referred to as HNLC (high nitrogen, low chlorophyll) regions. Sony VAIO VPC-P111KX/D Battery

As of now the best explanation for HNLC regions relates to iron limitation in the ocean. In recent years iron has become an important player when discussing ocean dynamics and nutrient cycles. The input of iron varies by region and is delivered to the ocean by dust (from dust storms) and is leached out of rocks. Iron is under consideration as the true limiting element in the ocean.Sony VAIO VPC-P111KX/G Battery

NH4+ and NO2 show a maximum concentration at 50-80 m (lower end of the euphotic zone) with decreasing concentration below that depth. This distribution can be accounted for by the fact that NO2 and NH4+ are intermediate species. They are both rapidly produced and consumed through the water column . Sony VAIO VPC-P111KX/P Battery

The amount of NH4+ in the ocean is about 3 orders of magnitude less than nitrate. Between NH4+, NO2, and NO3, NO2 has the fastest turnover rate. It can be produced during NO3assimilation, nitrification, and denitrification; however, it is immediately consumed again.Sony VAIO VPC-P111KX/W Battery

New vs. regenerated nitrogen

Nitrogen entering the euphotic zone is referred to as new nitrogen because it is newly arrived from outside the productive layer. The new nitrogen can come from below the euphotic zone or from outside sources. If the organic matter is eaten, respired, delivered to the water as ammonia, and re-incorporated into organic matter by phytoplankton it is considered recycled/regenerated production.Sony VAIO VPC-P112KX/B Battery

New production is an important component of the marine environment. One reason is that only continual input of new nitrogen can determine the total capacity of the ocean to produce a sustainable fish harvest. Harvesting fish from regenerated nitrogen areas will lead to a decrease in nitrogen and therefore a decrease in primary production. Sony VAIO VPC-P112KX/D Battery

This will have a negative effect on the system. However, if fish are harvested from areas of new nitrogen the nitrogen will be replenished.

Human influences on the nitrogen cycle

As a result of extensive cultivation of legumes (particularly soy, alfalfa, and clover), growing use of the Haber-Bosch process in the creation of chemical fertilizers, and pollution emitted by vehicles and industrial plants, human beings have more than doubled the annual transfer of nitrogen into biologically-available forms.Sony VAIO VPC-P112KX/G Battery

In addition, humans have significantly contributed to the transfer of nitrogen trace gases from Earth to the atmosphere, and from the land to aquatic systems. Human alterations to the global nitrogen cycle are most intense in developed countries and in Asia, where vehicle emissions and industrial agriculture are highest.Sony VAIO VPC-P112KX/P Battery

Nitrous oxide (N2O) has risen in the atmosphere as a result of agricultural fertilization, biomass burning, cattle and feedlots, and industrial sources. N2O has deleterious effects in the stratosphere, where it breaks down and acts as a catalyst in the destruction of atmospheric ozone. Sony VAIO VPC-P112KX/W Battery

In the atmosphere nitrous oxide is agreenhouse gas, and is currently the third largest contributor to global warming, after carbon dioxide and methane. While not as abundant in the atmosphere as carbon dioxide, it is for an equivalent mass, nearly 300 times more potent in its ability to warm the planet.Sony VAIO VPCP113KX/B Battery

Ammonia (NH3) in the atmosphere has tripled as the result of human activities. It is a reactant in the atmosphere, where it acts as an aerosol, decreasing air quality and clinging to water droplets, eventually resulting in nitric acid (HNO3) that produces acid rain. Atmospheric ammonia and nitric acid damage respiratory systems.Sony VAIO VPC-P113KX/B Battery

All forms of high-temperature combustion have contributed to a 6 or 7 fold increase in the flux of NOx to the atmosphere. Its production is a function of combustion temperature - the higher the temperature, the more NOx is produced. Fossil fuel combustion is a primary contributor, but so are biofuels and even the burning of hydrogen.Sony VAIO VPCP113KX/D Battery

The higher combustion temperature of hydrogen produces more NOx than natural gas combustion. The very-high temperature of lightning produces small amounts of NOx, NH3, and HNO3.

Ammonia and nitrous oxides actively alter atmospheric chemistry. Sony VAIO VPC-P113KX/D Battery

They are precursors of tropospheric (lower atmosphere) ozone production, which contributes to smog, and acid rain, damages plants and increases nitrogen inputs to ecosystems. Ecosystem processes can increase with nitrogen fertilization, but anthropogenic input can also result in nitrogen saturation, which weakens productivity and can damage the health of plants, animals, fish, and humans.Sony VAIO VPCP113KX/G Battery

Decreases in biodiversity can also result if higher nitrogen availability increases nitrogen-demanding grasses, causing a degradation of nitrogen-poor, species diverse heathlands.

Wastewater treatment

Onsite sewage facilities such as septic tanks and holding tanks release large amounts of nitrogen into the environment by discharging through a drainfield into the ground.Sony VAIO VPC-P113KX/G Battery

Microbial activity consumes the nitrogen and other contaminants in the wastewater.

However, in certain areas, the soil is unsuitable and some or all of the wastewater, with the contaminants, enters the aquifers. These contaminants accumulate and eventually end up in drinking water. One of the contaminants most concerned about is nitrogen in the form of nitrates. Sony VAIO VPCP113KX/P Battery

A nitrate concentration of 10 ppm (parts per million) or 10 milligrams per liter is the current EPA limit for drinking water and typical household wastewater can produce a range of 20–85 ppm.

One health risk associated with drinking water (with >10 ppm nitrate) is the development of methemoglobinemia and has been found to cause blue baby syndrome. Sony VAIO VPC-P113KX/P Battery

Several American states have now started programs to introduce advanced wastewater treatment systems to the typical onsite sewage facilities. The result of these systems is an overall reduction of nitrogen, as well as other contaminants in the wastewater.

Environmental impacts

Additional risks posed by increased availability of inorganic nitrogen in aquatic ecosystems include water acidification; Sony VAIO VPCP113KX/W Battery

eutrophication of fresh and saltwater systems; and toxicity issues for animals, including humans. Eutrophication often leads to lower dissolved oxygen levels in the water column, including hypoxic and anoxic conditions, which can cause cause death of aquatic fauna.Sony VAIO VPC-P113KX/W Battery

Relatively sessile benthos, or bottom-dwelling creatures, are particularly vulnerable because of their lack of mobility, though large fish kills are not uncommon. Oceanic dead zones near the mouth of the Mississippi in the Gulf of Mexico are a well-known examples of algal bloom-induced hypoxia.Sony VAIO VPC-P114KX/B Battery

The New York Adirondack Lakes, Catskills, Hudson Highlands, Rensselaer Plateau and parts of Long Island display the impact of nitric acid rain deposition, resulting in the killing of fish and many other aquatic species. Sony VAIO VPC-P114KX/D Battery

Ammonia (NH3) is highly toxic to fish and the level of ammonia discharged from wastewater treatment facilities must be closely monitored. To prevent fish deaths, nitrification via aeration prior to discharge is often desirable. Land application can be an attractive alternative to the aeration.Sony VAIO VPC-P114KX/G Battery,Sony VAIO VPC-P114KX/P Battery,Sony VAIO VPC-P114KX/W Battery,Sony VAIO VPCP115JC Battery,Sony VAIO VPCP115JC/B Battery