The nitrogen cycle is the biogeochemical cycle that describes the transformations of nitrogen and nitrogen- containing compounds in nature biogeochemical cycle nitrogen

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 plants, much of the nitrogen is used in chlorophyll molecules which are essential for photosynthesis and further growth.amino acidsproteinsnucleic acidsDNARNAplantschlorophyllphotosynthesis

Nitrogen fixation The conversion of nitrogen (N 2 ) 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.

There are three main ways to convert N 2 (atmospheric nitrogen gas) into more chemically reactive forms Biological fixation Industrial N-fixation Atmospheric fixation (lightning)

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.

Under great pressure, at a temperature of 600 C, and with the use of a catalyst, atmospheric nitrogen and hydrogen can be combined to form ammonia (NH 3 ). which is used to make fertilizer and explosives.

The enormous energy of lightning breaks nitrogen molecules and enables their atoms to combine with oxygen in the air forming nitrogen oxides. These dissolve in rain, forming nitrates, that are carried to the earth. Atmospheric nitrogen fixation probably contributes some 5– 8% of the total nitrogen fixed.

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

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. mineralization

The conversion of ammonia to nitrates is performed primarily by soil-living bacteria and other nitrifying bacteria. The primary stage of nitrification, the oxidation of ammonia (NH 3 ) is performed by bacteria such as the Nitrosomonas species, which converts ammonia to nitrites (NO 2 - ). Other bacterial species, such as the Nitrobacter, are responsible for the oxidation of the nitrites into nitrates (NO 3 - ).It is important for the nitrites to be converted to nitrates because accumulated nitrites are toxic to plant life.NitrosomonasNitrobacter

Denitrification is the reduction of nitrites back into the largely inert nitrogen gas (N 2 ), completing the nitrogen cycle. This process is performed by bacterial species such as Pseudomonas and Clostridium in anaerobic conditions PseudomonasClostridium

In this biological process, nitrite and ammonium are converted directly into dinitrogen gas. This process makes up a major proportion of dinitrogen conversion in the oceans.nitriteammoniumdinitrogen

 Extraction Growing of legumes Industrial extraction for fertilizer  Release Burning fossil fuels Untreated sewage release Fertilizer run off

Destruction of ozone. (N 2 O has deleterious effects in the stratosphere, where it breaks down and acts as a catalyst in the destruction of atmospheric ozone)stratosphere catalyst Reduction of air quality (Ammonia (NH 3 ) is a reactant in the atmosphere, where it acts as an aerosol, decreasing air quality and clinging on to water droplets.) Reduction of air quality (Ammoniaaerosolwater Atmospheric Pollution (NOx actively alters atmospheric chemistry, and is a precursor of tropospheric (lower atmosphere) ozone production, which contributes to smog, acid rain) atmospheric chemistry troposphericsmog

(Water pollution) Eutrophication (Water pollution) Onsite sewage facilities 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 grounddrainfield Poisoning (The health risk associated with drinking >10 ppm nitrogen water is the development of blue baby syndrome.)blue baby syndrome