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The nitrogen cycle is thebiogeochemical cycle thatdescribes the transformations of nitrogen and nitrogen-

containing compounds innature

http://en.wikipedia.org/wiki/Biogeochemical_cyclehttp://en.wikipedia.org/wiki/Nitrogenhttp://en.wikipedia.org/wiki/Nitrogenhttp://en.wikipedia.org/wiki/Biogeochemical_cycle

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Nitrogen is essential for many biologicalprocesses; and is crucial for any life here onEarth. It is in all amino acids , isincorporated into proteins , and is present inthe bases that make up nucleic acids , suchas DNA and RNA . In plants , much of the

nitrogen is used in chlorophyll molecules which are essential for photosynthesis andfurther growth.

http://en.wikipedia.org/wiki/Amino_acidshttp://en.wikipedia.org/wiki/Proteinshttp://en.wikipedia.org/wiki/Nucleic_acidshttp://en.wikipedia.org/wiki/DNAhttp://en.wikipedia.org/wiki/RNAhttp://en.wikipedia.org/wiki/Plantshttp://en.wikipedia.org/wiki/Chlorophyllhttp://en.wikipedia.org/wiki/Photosynthesishttp://en.wikipedia.org/wiki/Photosynthesishttp://en.wikipedia.org/wiki/Chlorophyllhttp://en.wikipedia.org/wiki/Plantshttp://en.wikipedia.org/wiki/RNAhttp://en.wikipedia.org/wiki/DNAhttp://en.wikipedia.org/wiki/Nucleic_acidshttp://en.wikipedia.org/wiki/Proteinshttp://en.wikipedia.org/wiki/Amino_acids

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Nitrogen fixation

The conversion of nitrogen (N 2) from theatmosphere into a form readily available to plants and hence toanimals and humans is an importantstep in the nitrogen cycle, thatdetermines the supply of this essential

nutrient.

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There are three main ways to convert N 2 (atmospheric nitrogen gas) into morechemically reactive formsBiological fixationIndustrial N-fixation

Atmospheric fixation (lightning)

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some symbiotic bacteria (mostoften associated withleguminous plants) and somefree-living bacteria are able to

fix nitrogen and assimilate it asorganic nitrogen.

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Under great pressure, at atemperature of 600 C, and with the

use of a catalyst, atmosphericnitrogen and hydrogen can becombined to form ammonia (NH 3). which is used to make fertilizer andexplosives.

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The enormous energy of lightningbreaks nitrogen molecules and enablestheir atoms to combine with oxygen inthe air forming nitrogen oxides. Thesedissolve in rain, forming nitrates, thatare carried to the earth. Atmospheric nitrogen fixationprobably contributes some 5 8% of the

total nitrogen fixed.

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Plants can absorb nitrate orammonium ions from the soil viatheir root hairs. If nitrate is

absorbed, it is first reduced tonitrite ions and then ammoniumions for incorporation into aminoacids, nucleic acids, andchlorophyll

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When a plant or animal dies, or ananimal excretes, the initial form of

nitrogen is organic. Bacteria, or insome cases, fungi, converts theorganic nitrogen within the

remains back into ammonia, aprocess called ammonification ormineralization .

http://en.wikipedia.org/wiki/Mineralization_(soil)http://en.wikipedia.org/wiki/Mineralization_(soil)

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The conversion of ammonia to nitrates is performedprimarily by soil-living bacteria and other nitrifyingbacteria. The primary stage of nitrification, theoxidation of ammonia (NH

3) is performed by bacteria

such as the Nitrosomonas species, which convertsammonia to nitrites (NO 2-). Other bacterial species,such as the Nitrobacter , are responsible for theoxidation of the nitrites into nitrates (NO

3

-).It isimportant for the nitrites to be converted to nitratesbecause accumulated nitrites are toxic to plant life.

http://en.wikipedia.org/wiki/Nitrosomonashttp://en.wikipedia.org/wiki/Nitrobacterhttp://en.wikipedia.org/wiki/Nitrobacterhttp://en.wikipedia.org/wiki/Nitrosomonas

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Denitrification is the reduction of nitrites back into the largely inertnitrogen gas (N

2), completing the

nitrogen cycle. This process isperformed by bacterial species such asPseudomonas

andClostridium

inanaerobic conditions

http://en.wikipedia.org/wiki/Pseudomonashttp://en.wikipedia.org/wiki/Clostridiumhttp://en.wikipedia.org/wiki/Clostridiumhttp://en.wikipedia.org/wiki/Pseudomonas

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In this biological process, nitrite and ammonium are converteddirectly into dinitrogen gas. Thisprocess makes up a major

proportion of dinitrogenconversion in the oceans.

http://en.wikipedia.org/wiki/Nitritehttp://en.wikipedia.org/wiki/Ammoniumhttp://en.wikipedia.org/wiki/Dinitrogenhttp://en.wikipedia.org/wiki/Dinitrogenhttp://en.wikipedia.org/wiki/Ammoniumhttp://en.wikipedia.org/wiki/Nitrite

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ExtractionGrowing of legumesIndustrial extraction for fertilizer

ReleaseBurning fossil fuels

Untreated sewage releaseFertilizer run off

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Destruction of ozone. (N 2O has deleterious effects inthe stratosphere , where it breaks down and acts as acatalyst in the destruction of atmospheric ozone)

Reduction of air quality (Ammonia (NH 3) is a reactantin the atmosphere, where it acts as an aerosol ,decreasing air quality and clinging on to water droplets.)

Atmospheric Pollution (NOx actively altersatmospheric chemistry , and is a precursor of tropospheric (lower atmosphere) ozone production, which contributes to smog , acid rain)

http://en.wikipedia.org/wiki/Stratospherehttp://en.wikipedia.org/wiki/Catalysthttp://en.wikipedia.org/wiki/Ammoniahttp://en.wikipedia.org/wiki/Aerosolhttp://en.wikipedia.org/wiki/Aerosolhttp://en.wikipedia.org/wiki/Waterhttp://en.wikipedia.org/wiki/Atmospheric_chemistryhttp://en.wikipedia.org/wiki/Tropospherehttp://en.wikipedia.org/wiki/Smoghttp://en.wikipedia.org/wiki/Smoghttp://en.wikipedia.org/wiki/Tropospherehttp://en.wikipedia.org/wiki/Atmospheric_chemistryhttp://en.wikipedia.org/wiki/Waterhttp://en.wikipedia.org/wiki/Aerosolhttp://en.wikipedia.org/wiki/Ammoniahttp://en.wikipedia.org/wiki/Catalysthttp://en.wikipedia.org/wiki/Stratosphere

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(Water pollution) EutrophicationOnsite sewage facilities such as septic tanks

and holding tanks release large amounts of nitrogen into the environment by discharging through a drainfield into theground

Poisoning (The health risk associated withdrinking >10 ppm nitrogen water is thedevelopment of blue baby syndrome .)

http://en.wikipedia.org/wiki/Onsite_sewage_facilitieshttp://en.wikipedia.org/wiki/Onsite_sewage_facilitieshttp://en.wikipedia.org/w/index.php?title=Drainfield&action=edit&redlink=1http://en.wikipedia.org/wiki/Blue_baby_syndromehttp://en.wikipedia.org/wiki/Blue_baby_syndromehttp://en.wikipedia.org/w/index.php?title=Drainfield&action=edit&redlink=1http://en.wikipedia.org/wiki/Onsite_sewage_facilitieshttp://en.wikipedia.org/wiki/Onsite_sewage_facilitieshttp://en.wikipedia.org/wiki/Onsite_sewage_facilities

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http://en.wikipedia.org/wiki/Image:Nitrogen_Cycle.jpghttp://en.wikipedia.org/wiki/Image:Nitrogen_Cycle.jpg

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