Major Biogeochemical Cycles: Definition, Explanation and Importance

Biogeochemical cycles:

    Biogeochemical cycles are those cycles in which bio elements recycle through different pathways. These cycles are complete through biological, geological and chemical processes. The major cycles are carbon cycle, nitrogen cycle and water cycle.

Carbon cycle:

    Carbon is major bio element. It is essential for life as it is a basic component of all organic material. It is found in the form of graphite, diamond, carbon dioxide(CO₂) and organic compound. Carbon cycle is complete in air through this process.
  • First of all plants absorb CO₂ from atmosphere for photosynthesis. Photosynthesis is a complex process in which plants use H₂O and CO₂ to produce organic compound glucose.
  • Animals and other organisms eat this food and incorporate carbon in their bodies.
  • Fungi and bacteria decompose waste products of plants and animals . CO₂ is released in atmosphere from these products.
    Carbon cycle in air
Carbon cycle is also works in water bodies mainly oceans. 
  • Firstly ocean absorb CO₂ from atmosphere.
  • It reacts with water and form many compounds mainly bicarbonate ions. 
  • These ions decompose by organisms and then CO₂ back release in atmosphere.
  • Carbon also stored in organisms, after their death by decomposition CO₂ released.   

Importance of carbon cycle:

    Carbon cycle is very important in regulating climate and temperature. Because CO₂ balance greenhouse effect. 
    

Nitrogen cycle:

    Nitrogen is also a basic component of many organic compounds such as amino acid and nucleic acid. Nitrogen make up 78% of gases in atmosphere. Nitrogen cycle involves preparation of nitrates from nitrogen gas N₂, which is circulated and recirculated through living organisms. Nitrogen cycle is accomplished by following stages.
Nitrogen cycle

1.Nitrogen fixation:

    Organisms cannot intake nitrogen directly from atmosphere. It must be converted into nitrates. Nitrogen is converted into ammonia. This conversion is called ammonification. Nitrogen can be converted through various ways.
  • Nitrogen fixing bacteria Rhizobium can fix it in soil.
  • Lightning strikes provides energy which break N₂(N-N) bonds. N combine with atmospheric oxygen to form nitrous and nitric acid. These acids are dissolve in rain water and fall to the ground. This fixation is called atmospheric fixation. 
  • Haber-Bosch process can be used in industries to fix nitrogen. In this process nitrogen is reacted with hydrogen which forms ammonia(NH₃). This ammonia is used for making fertilizers.

2.Nitrification:

     Conversion of ammonium(NH₄⁺) and ammonia(NH₃) into nitrites(NO₂⁻) and then nitrates(NO₃⁻) is called nitrification. This can be done by nitrifying bacteria which converts NH₃ into NO₂⁻.  Then bacteria convert NO₂⁻ into NO₃⁻ .

3.Assimilation:

    Plants uptake nitrates from soil. They use these nitrates to produce amino acids which are building blocks of proteins and other organic compounds. Animal and other organisms consume food from plants. 

4.Ammonification:

    When plants die organic matter are decompose into ammonia. When animal digest food they excrete NH₃ as a waste product. 

5.Denitrification:

    Conversion of nitrates and ammonia into nitrogen gas is called denitrification. This is done by denitrifying bacteria. Nitrogen gas then back release in atmosphere.

Importance:

  • Nitrogen cycle is very important for atmosphere because it regulate nitrogen level. 
  • It is very important for plants because they could not intake nitrogen gas. 
  • It regulate soil health.

Water cycle:

    Water is generally found in liquid state. Its freezing point(minimum temperature where liquid changes into solid) is 0C and boiling point(maximum temperature where liquid changes to gas) 100C. Water cycle is proceed in four steps. 
  • Firstly, water is evaporate from oceans, rivers and lakes in atmosphere(evaporation). 
  • Secondly, it cooldown and form cloud(condensation). 
  • Thirdly, it water falls in the form of rain(precipitation). 
  • Last, water flow towards oceans and lakes(run off).
    The water cycle

  

Human impact:

    Human activities have negative impact on these cycles. Deforestation, burning of fossil fuels, excessive use of fertilizers disturb these cycles as
  • Cutting of trees causes increase in the amount of CO₂.
  • Fertilizers increase amount of nitrogen in soil which flow in water bodies and causes water pollution.
  • Automobiles release nitrous oxide, which is a green house gas.  

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