Schematic representation of the flow of Nitrogen through the environment. The importance of bacteria in the cycle is immediately recognized as being a key element in the cycle, providing different forms of nitrogen compounds assimilable by higher organisms. See Martinus Beijerinck. Martinus Willem Beijerinck ( March 16, 1851 - January 1, 1931) was a Dutch Microbiologist and Botanist

The nitrogen cycle is the biogeochemical cycle that describes the transformations of nitrogen and nitrogen-containing compounds in nature. In Ecology and Earth science, a biogeochemical cycle is a circuit or pathway by which a Chemical element or Molecule moves through both biotic Nitrogen (ˈnaɪtɹəʤɪn is a Chemical element that has the symbol N and Atomic number 7 and Atomic weight 14 It is a gaseous cycle. This page is about the physical properties of gas as a state of matter

Earth's atmosphere is about 78% nitrogen, making it the largest pool of nitrogen. Temperature and layers The temperature of the Earth's atmosphere varies with altitude the mathematical relationship between temperature and altitude varies among five Nitrogen (ˈnaɪtɹəʤɪn is a Chemical element that has the symbol N and Atomic number 7 and Atomic weight 14 Nitrogen is essential for many biological processes; and is crucial for any life here on Earth. It is in all amino acids, is incorporated into proteins, and is present in the bases that make up nucleic acids, such as DNA and RNA. In Chemistry, an amino acid is a Molecule containing both Amine and Carboxyl Functional groups In Biochemistry, this Proteins are large Organic compounds made of Amino acids arranged in a linear chain and joined together by Peptide bonds between the Carboxyl A nucleic acid is a Macromolecule composed of chains of monomeric Nucleotides In Biochemistry these Molecules carry Genetic information Deoxyribonucleic acid ( DNA) is a Nucleic acid that contains the genetic instructions used in the development and functioning of all known Ribonucleic acid ( RNA) is a Nucleic acid that consists of a long chain of Nucleotide units In plants, much of the nitrogen is used in chlorophyll molecules which are essential for photosynthesis and further growth. Plants are living Organisms belonging to the kingdom Plantae. Chlorophyll is a green Pigment found in most Plants Algae and Cyanobacteria. Photosynthesis is a Metabolic pathway that converts Light Energy into Chemical energy. ^[1]

Processing, or fixation, is necessary to convert gaseous nitrogen into forms usable by living organisms. Nitrogen fixation is the process by which Nitrogen is taken from its natural relatively inert molecular form (N2 in the atmosphere and converted into Some fixation occurs in lightning strikes, but most fixation is done by free-living or symbiotic bacteria. Lightning is an atmospheric discharge of Electricity, which typically occurs during Thunderstorms and sometimes during volcanic eruptions or This article is about the biological phenomenon for other uses see Symbiosis (disambiguation The term symbiosis (from the Greek The Bacteria ( singular: bacterium) are a large group of unicellular Microorganisms Typically a few Micrometres in length bacteria have 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 its own organic compounds. Nitrogenase ( is the Enzyme used by some organisms to fix atmospheric Nitrogen gas (N2 Enzymes are Biomolecules that catalyze ( ie increase the rates of Chemical reactions Almost all enzymes are Proteins Hydrogen (ˈhaɪdrədʒən is the Chemical element with Atomic number 1 Ammonia is a compound with the formula N[[hydrogen H3]] It is normally encountered as a Gas with a characteristic pungent Odor An organic compound is any member of a large class of Chemical compounds whose Molecules contain Carbon. Some nitrogen fixing bacteria, such as Rhizobium, live in the root nodules of legumes (such as peas or beans). Rhizobia (from the Greek words rhiza = root and bios = Life are Soil bacteria that fix Nitrogen ( Diazotrophy A legume is a Plant in the family Fabaceae (or Leguminosae or a Fruit of these specific plants Here they form a mutualistic relationship with the plant, producing ammonia in exchange for carbohydrates. Mutualism is a Biological interaction between individuals of two different Species, where both individuals derive a fitness benefit for example increased Carbohydrates (from ' Hydrates of Carbon ' or saccharides ( Greek σάκχαρον meaning " Sugar " are the most Nutrient-poor soils can be planted with legumes to enrich them with nitrogen. A few other plants can form such symbioses. This article is about the biological phenomenon for other uses see Symbiosis (disambiguation The term symbiosis (from the Greek

Other plants get nitrogen from the soil by absorption at their roots in the form of either nitrate ions or ammonium ions. In Inorganic chemistry, a nitrate is a salt of Nitric acid with an Ion composed of one Nitrogen and three Oxygen atoms An ion is an Atom or Molecule which has lost or gained one or more Valence electrons giving it a positive or negative electrical charge Ammonium is also an old name for the Siwa Oasis in western Egypt. All nitrogen obtained by animals can be traced back to the eating of plants at some stage of the food chain. Food chains, also called food networks and/or trophic networks, describe the feeding relationships between species within an Ecosystem.

Due to their very high solubility, nitrates can enter groundwater. Solubility is the characteristic Physical property referring to the ability of a given substance the Solute, to dissolve in a Solvent. 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. Methemoglobinemia is a disorder characterized by the presence of a higher than normal level of Methemoglobin (metHb in the Blood. ^[2] Where groundwater recharges stream flow, nitrate-enriched groundwater can contribute to eutrophication, a process leading to high algal, especially blue-green algal populations and the death of aquatic life due to excessive demand for oxygen. Eutrophication is an increase in chemical Nutrients -- typically compounds containing Nitrogen or Phosphorus -- in an Ecosystem, and may occur Algae ( sing. alga are a large and diverse group of simple typically Autotrophic organisms ranging from Unicellular to Multicellular forms 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. As of 2006, the application of nitrogen fertilizer is being increasingly controlled in Britain and the United States. Fertilizers ( also spelt fertiliser are chemical compounds given to Plants to promote growth they are usually applied either through the soil for uptake by plant 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.

Ammonia is highly toxic to fish life and the water discharge level of ammonia from wastewater treatment plants must often be closely monitored. To prevent loss of fish, nitrification prior to discharge is often desirable. Land application can be an attractive alternative to the mechanical aeration needed for nitrification. Aeration is the Process by which Air is circulated through mixed with or dissolved in a Liquid or substance

During anaerobic (low oxygen) conditions, denitrification by bacteria occurs. For other uses of the term "hypoxia" see Hypoxia. Hypoxia or oxygen depletion is a phenomenon that occurs in aquatic environments Denitrification is a microbially facilitated process of dissimilatory nitrate reduction that may ultimately produce molecular Nitrogen (N2 through a series of intermediate This results in nitrates being converted to nitrogen gas and returned to the atmosphere. Temperature and layers The temperature of the Earth's atmosphere varies with altitude the mathematical relationship between temperature and altitude varies among five Nitrate can also be reduced to nitrite and subsequently combine with ammonium in the anammox process, which also results in the production of dinitrogen gas. In Inorganic chemistry, a nitrate is a salt of Nitric acid with an Ion composed of one Nitrogen and three Oxygen atoms The nitrite Ion is NO2− The anion is bent being Isoelectronic with O3. Ammonium is also an old name for the Siwa Oasis in western Egypt. Anammox, an acronym for anaerobic ammonium oxidation, is a stage in the Nitrogen cycle.

Processes of the nitrogen cycle

Nitrogen fixation

Main article: Nitrogen fixation

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, that determines the supply of this essential nutrient. Nitrogen fixation is the process by which Nitrogen is taken from its natural relatively inert molecular form (N2 in the atmosphere and converted into There are four ways to convert N₂ (atmospheric nitrogen gas) into more chemically reactive forms:^[1]

1. Biological fixation: some symbiotic bacteria (most often associated with leguminous plants) and some free-living bacteria are able to fix nitrogen and assimilate it as organic nitrogen. An example of mutualistic nitrogen fixing bacteria are the Rhizobium bacteria, which live in legume root nodules. Rhizobia (from the Greek words rhiza = root and bios = Life are Soil bacteria that fix Nitrogen ( Diazotrophy A legume is a Plant in the family Fabaceae (or Leguminosae or a Fruit of these specific plants These species are diazotrophs. Diazotrophs are Bacteria that fix atmospheric Nitrogen gas into a more usable form such as Ammonia. An example of the free-living bacteria is Azotobacter. Azotobacter is a Genus of usually motile oval or spherical Bacteria that form thick-walled cysts and may produce large quantities of capsular slime
2. Industrial N-fixation : in the Haber-Bosch process, N₂ is converted together with hydrogen gas (H₂) into ammonia (NH₃) which is used to make fertilizer and explosives. The Haber process, also called the Haber–Bosch process, is the Nitrogen fixation reaction of Nitrogen and Hydrogen, over an iron substrate
3. Combustion of fossil fuels : automobile engines and thermal power plants, which release various nitrogen oxides (NO_x).
4. Other processes : Additionally, the formation of NO from N₂ and O₂ due to photons and especially lightning, are important for atmospheric chemistry, but not for terrestrial or aquatic nitrogen turnover.

Assimilation

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. ^[1] In plants which have a mutualistic relationship with rhizobia, amy stone some nitrogen is assimilated in the form of ammonium ions directly from the nodules. Animals, fungi, and other heterotrophic organisms absorb nitrogen as amino acids, nucleotides and other small organic molecules. A heterotrophs, or chemoorganotrophy ( Greek heterone = (another and trophe = nutrition is an Organism that requires In Chemistry, an amino acid is a Molecule containing both Amine and Carboxyl Functional groups In Biochemistry, this Nucleotides are Organic compounds that consist of three joined structures a nitrogenous base a Sugar, and a Phosphate group

Ammonification

When a plant or animal dies, or an animal excretes, the initial form of nitrogen is organic. Bacteria, or in some cases, fungi, converts the organic nitrogen within the remains back into ammonia, a process called ammonification or mineralization.

Nitrification

Main article: Nitrification

The conversion of ammonia to nitrates is performed primarily by soil-living bacteria and other nitrifying bacteria. Nitrification is the biological oxidation of Ammonia with oxygen into Nitrite followed by the oxidation of these nitrites into Nitrates Degradation The primary stage of nitrification, the oxidation of ammonia (NH₃) is performed by bacteria such as the Nitrosomonas species, which converts ammonia to nitrites (NO₂^-). Nitrosomonas is a Genus comprising ellipsoidal soil Bacteria. Other bacterial species, such as the Nitrobacter, are responsible for the oxidation of the nitrites into nitrates (NO₃^-). Nitrobacter is a rod-shaped Gram-negative, and a Chemoautotrophic bacterium ^[1]

Denitrification

Main article: Denitrification

Denitrification is the reduction of nitrites back into the largely inert nitrogen gas (N₂), completing the nitrogen cycle. Denitrification is a microbially facilitated process of dissimilatory nitrate reduction that may ultimately produce molecular Nitrogen (N2 through a series of intermediate This process is performed by bacterial species such as Pseudomonas and Clostridium in anaerobic conditions. Pseudomonas is a Genus of gamma Proteobacteria, belonging to the larger family of Pseudomonads Recently 16S rRNA sequence Clostridium is a Genus of Gram-positive bacteria belonging to the Firmicutes. ^[1] 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.

Anaerobic ammonium oxidation

Main article: Anammox

In this biological process, nitrite and ammonium are converted directly into dinitrogen gas. Anammox, an acronym for anaerobic ammonium oxidation, is a stage in the Nitrogen cycle. The nitrite Ion is NO2− The anion is bent being Isoelectronic with O3. Ammonium is also an old name for the Siwa Oasis in western Egypt. Nitrogen (ˈnaɪtɹəʤɪn is a Chemical element that has the symbol N and Atomic number 7 and Atomic weight 14 This process makes up a major proportion of dinitrogen conversion in the oceans.

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. The Haber process, also called the Haber–Bosch process, is the Nitrogen fixation reaction of Nitrogen and Hydrogen, over an iron substrate ^[2] 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. EARTH was a short-lived Japanese vocal trio which released 6 singles and 1 album between 2000 and 2001 Temperature and layers The temperature of the Earth's atmosphere varies with altitude the mathematical relationship between temperature and altitude varies among five

N₂O has risen in the atmosphere as a result of agricultural fertilization, biomass burning, cattle and feedlots, and other industrial sources. ^[3] N₂O has deleterious effects in the stratosphere, where it breaks down and acts as a catalyst in the destruction of atmospheric ozone. The stratosphere is the second major layer of Earth's atmosphere, just above the Troposphere, and below the Mesosphere. Catalysis is the process in which the rate of a Chemical reaction is increased by means of a Chemical substance known as a catalyst OZONE is an object oriented Operating system written in the C programming language. Ammonia (NH₃) in the atmosphere has tripled as the result of human activities. Ammonia is a compound with the formula N[[hydrogen H3]] It is normally encountered as a Gas with a characteristic pungent Odor It is a reactant in the atmosphere, where it acts as an aerosol, decreasing air quality and clinging on to water droplets, eventually resulting in acid rain. Technically an aerosol is a suspension of fine solid particles or liquid droplets in a gas Water is a common Chemical substance that is essential for the survival of all known forms of Life. Acid rain is Rain or any other form of precipitation that is unusually Acidic It has harmful effects on plants aquatic animals and infastructure Fossil fuel combustion has contributed to a 6 or 7 fold increase in NOx flux to the atmosphere. Fossil fuels or mineral fuels are fossil source Fuels that is Hydrocarbons found within the top layer of the Earth’s crust. Combustion or burning is a complex sequence of Exothermic chemical reactions between a Fuel and an Oxidant accompanied by the production of NOx actively alters atmospheric chemistry, and is a precursor of tropospheric (lower atmosphere) ozone production, which contributes to smog, acid rain, and increases nitrogen inputs to ecosystems. Atmospheric chemistry is a branch of Atmospheric science in which the Chemistry of the Earth's atmosphere and that of other planets is studied The troposphere is the lowest portion of Earth's atmosphere. It contains approximately 75% of the atmosphere's mass and almost all of its Water vapor and Smog is a kind of Air pollution; the word "smog" is a Portmanteau of Smoke and Fog. ^[1] Ecosystem processes can increase with nitrogen fertilization, but anthropogenic input can also result in nitrogen saturation, which weakens productivity and can kill plants. An ecosystem is a natural unit consisting of all plants animals and micro-organisms( Biotic factors in an area functioning together with all of the non-living physical ( For soil improvement see Fertilization (soil. Anthropogenic effects processes objects or materials are those that are derived from Human activities as opposed to those occurring in Natural environments without ^[2] Decreases in biodiversity can also result if higher nitrogen availability increases nitrogen-demanding grasses, causing a degradation of nitrogen-poor, species diverse heathlands. Biodiversity is the variation of Life forms within a given Ecosystem, Biome or for the entire Earth. ^[4]

Wastewater

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. On Site Sewage Facilities ( OSSF) are Wastewater systems designed to treat and dispose of effluent on the same property that produces the wastewater Microbial activity consumes the nitrogen and other contaminants in the wastewater. However, in certain areas the soil is unsuitable to handle some or all of the wastewater, and as a result, the wastewater with the contaminants enters the aquifers. An aquifer is an underground layer of Water -bearing Permeable rock or unconsolidated materials ( Gravel, Sand, Silt, or Clay These contaminants accumulate and eventually end up in drinking water. One of the contaminants concerned about the most is nitrogen in the form of nitrates. Nitrogen (ˈnaɪtɹəʤɪn is a Chemical element that has the symbol N and Atomic number 7 and Atomic weight 14 In Inorganic chemistry, a nitrate is a salt of Nitric acid with an Ion composed of one Nitrogen and three Oxygen atoms A nitrate concentration of 10 ppm 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 (milligrams per liter).

The health risk associated with drinking >10 ppm nitrogen water is the development of methemoglobinemia and has been found to cause blue baby syndrome. Methemoglobinemia is a disorder characterized by the presence of a higher than normal level of Methemoglobin (metHb in the Blood. Blue baby syndrome (or simply blue baby) is a Layman 's term used to describe Newborns with cyanotic conditions such as Cyanotic Several 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.

References

Bibliography

• The Nitrogen Cycle, and New Tank Syndrome http://www.aquariumdomain.com/guideTheNitrogenCycle.asp, accessed 2006-07-16.
• Raven, P. H. and G. B. Johnson. 1996. Biology. Wm. C. Brown Publishers.