What is Nitrogen Cycle

The nitrogen cycle is the natural flow of nitrogen in various forms. Nitrogen, which is found in proteins and nucleic acids, is necessary for life on Earth to exist. Although nitrogen gas makes up 78 percent of the atmosphere by volume, it is in an useless condition for most species.

Nitrogen cycle:

The nitrogen cycle is a biogeochemical cycle in which nitrogen is transformed into numerous chemical forms as it moves through the atmospheric, land, and sea ecosystems. Both biological and physical methods can be used to convert nitrogen. Fixation, ammonification, nitrification, and denitrification are all important processes in the nitrogen cycle. Atmospheric nitrogen makes up the majority of the Earth’s atmosphere (78 percent), making it the most abundant source of nitrogen. However, the availability of atmospheric nitrogen for biological utilisation is limited, resulting in a scarcity of usable nitrogen in many ecosystems.

Nitrogen cycle diagram:

Nitrogen formula:

Nitrogen is represented by the chemical symbol N. Nitrogen gas has the chemical formula N₂.

N≡N can be used to denote the formula. Nitrogen gas is a diatomic element made up of two atoms of the same element linked by one or more covalent bonds . In the instance of N₂, a triple covalent link connects the two nitrogen atoms.

Explanation:

The molecule of nitrogen (N₂)

Nitrogen’s electrical configuration (Z=7) is 1s² 2s² 2px¹2py¹2pz¹.

In the nitrogen molecule (N₂), there are a total of 14 electrons.

These 14 electrons can be accommodated in various chemical orbitals in order to optimise energy.

N2: KK (σ2s)2 (σ2s⋆)2 (π2Px)2 (π2py)2 (σ2px⋆)2 (π2py⋆)2

The (1s)² (1s)² component of the arrangement is abbreviated as KK, which stands for the two atoms’ K shells. We can omit KK while computing bond order because it has two bonding and two antibonding electrons.

The bond order of N₂ can be computed by using the following formula:

Nb = 8 and Na = 2 in this case.

(Nb-Na) /2 bond order

Order of Bonds = (8-2)/2

Order of Bonds = 3

Because the bond order is three, Nitrogen has three bonds and is abbreviated as N≡N.

Marine nitrogen cycle:

In the ocean, the nitrogen cycle is also an important process. While the overall cycle is similar, the participants and modes of nitrogen transport in the ocean differ. Nitrogen enters the water system by precipitation, runoff, or atmospheric N₂. Because phytoplankton cannot use nitrogen as N₂, it must undergo nitrogen fixation, which is primarily conducted by cyanobacteria. Fixed nitrogen would be depleted in the marine cycle in around 2000 years if sources were not replenished. For the beginning synthesis of organic matter, phytoplankton requires nitrogen in physiologically accessible forms. Plankton excretion causes ammonia and urea to be released into the water. The downward migration of organic matter removes nitrogen sources from the euphotic zone. 

Human influence on the nitrogen cycle:

Humans have more than doubled the annual transfer of nitrogen into biologically available forms 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 fertilisers, and pollution emitted by vehicles and industrial plants. Furthermore, people have played a substantial role in the transport of nitrogen trace gases from the Earth’s surface to the atmosphere, as well as from land to aquatic systems. Human-induced changes to the global nitrogen cycle are most pronounced in developed countries and Asia, which have the highest levels of automobile emissions and industrial agriculture.

Human manipulation of the nitrogen cycle has the following consequences:

Impacts on human health: nitrate accumulation in drinking water:

Leakage of Nr (reactive nitrogen) from human activities can lead to nitrate buildup in natural water bodies, which can have negative health consequences. One of the biggest sources of nitrate pollution in groundwater and surface water has been excessive use of nitrogen fertiliser in agriculture. Nitrate can quickly escape from the subsurface layer to the groundwater due to its high solubility and limited soil retention, resulting in nitrate pollution. Livestock feeding, animal and human contamination, and urban and industrial waste are among other non-point sources of nitrate pollution in groundwater. Because groundwater is frequently used as a primary source of domestic water, nitrate pollution can spread from groundwater to surface and drinking water during the process of producing potable water, especially in small communities.

Impacts on human health: air quality:

Human activities have also radically affected the global nitrogen cycle by producing nitrogenous gases, which are linked to global nitrogen pollution in the atmosphere. Reactive nitrogen (Nr) fluxes in the atmosphere come from a variety of places. Agricultural sources of reactive nitrogen can emit ammonia (NH₃), nitrogen oxides (NOₓ), and nitrous oxide into the atmosphere (N₂O). By emitting NOₓ, an accidental waste product, combustion operations in energy production, transportation, and manufacturing might result in the formation of new reactive nitrogen. When reactive nitrogens are released into the lower atmosphere, they can cause smog, particulate matter, and aerosols to develop, all of which are key contributors to the negative health effects of air pollution. NO₂ can be converted to nitric acid in the environment.

Impacts on natural systems:

Nitrogen deposition has been found to have a variety of deleterious consequences on both terrestrial and aquatic ecosystems. Certain plant species can be directly hazardous to nitrogen gases and aerosols, affecting the aboveground physiology and growth of plants near significant point sources of nitrogen pollution. Plant species may change when the accumulation of nitrogen compounds increases their availability in a given ecosystem, affecting species composition, plant diversity, and nitrogen cycle. Ammonia and ammonium, two reduced forms of nitrogen, can be harmful over time due to increased toxicity toward delicate plant species, particularly those that are accustomed to obtaining nitrogen from nitrate, resulting in poor root and shoot development. 

Atomic mass of nitrogen:

Nitrogen has an atomic mass of 14.01 amu (14.01 g/mol).

Conclusion:

Bacteria and fungi aid in the decomposition of organic matter at the end of the nitrogen cycle, where the nitrogenous chemicals are dissolved into the soil and utilised by plants anew .The nitrogenous molecules in the soil are then converted to nitrogen gas by microorganisms. Creatures absorb nitrogen by eating these plants or other nitrogen-containing animals. Humans absorb the proteins from these plants and animals, and the nitrogen is incorporated into our system.