Biogeochemical Cycles - Part I

Carbon CycleCarbon is exchanged among the biosphere, pedosphere, geosphere,

hydrosphere and the atmosphere of the Earth through a biogeochemical cycle called Carbon Cycle.

Oxygen CycleThis biogeochemical cycle explains the movement of oxygen gas within

the atmosphere, the ecosystem, biosphere and the lithosphere.

Oxidisingatmosphere

Ocean

PlantsAnimals

N2

Ar

H2OCO2

O2

CH2

Biogeochemical Cycles

Living Organisms Non-living Di�erent Reactions on Earth

Biotic components

The movement of chemical substances among the living and non-living components of the Earth

Main biogeochemical cycles are Carbon cycle, Oxygen cycle, Hydrogen cycle, Nitrogen cycle, Phosphorus cycle, Sulphur cycle and Water cycle

All organic compounds have carbon

21% O2 in air Atom in molecules like H2O, CO2Used for Respiration, Combustion, Oxidation and Decomposition

Auto &Factory

emissionsPhotosynthesis

Plantrespiration

Rootrespiration

Organic waste

Animalrespiration

Ocean uptake

Plantrespirationrespirationrespiration

Animalrespirationrespiration

PlantAnimal

CO2Cycle

Plants remove CO2 from atmosphere.

1

All aerobic organisms usefree oxygen for respiration.

2All green plants during theprocess of photosynthesis,release oxygen back intothe atmosphere as a by-product.

1

CO2 is released inatmosphere by respirationof animals, combustion offossil fuels in industries and automobiles.

3

Lithosphere has CO2 in the form of fossil fuels2

Animals exhale carbon dioxide back into the atmosphere which is again used by the plants during photosynthesis. Thus oxygen is balancedin the atmosphere.

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Atmosphericoxygen

Oxygen

Carbondioxide

OOO

Photosynthesis

Abiotic components

Biogeochemical Cycles - Part II Nitrogen (N2) Cycle

Nitrogen Cycle is a biogeochemical process which transforms the elemental nitrogen present in the atmosphere to a more usable form for living organisms.

Nitrogen �xation Nitri�cation Assimilation Ammoni�cation Denitri�cation

Phosphorus CyclePhosphorus cycle involves both aquatic and soil reservoirs

Process of Nitrogen Cycle

Atmospheric nitrogen: 78%N2 (elemental form)

Ammonia and other soluble forms as NO3- & NO2- can be used

But animals & plants cannotutilize gaseous form of nitrogen

1 2 3

Too much nitrogen fromfertillizers returns to soil, contaminates ground water.

Plants and animals die,return to the soil,are decomposed

Forest �res release N2 from trees whichthen goes back to the atmosphere.

Denitrifying bacteria convertnitrogen to an unusable form,return it to atmosphere

Fish dies, decompose

Nitrogen from atmosphere returnsto soil and water with the help of bacteria and algae.

ATMOSPHERIC NITROGEN 78%

Decomposers( Worms, bacteria, beetles, fungi) break down waste and dead things.Bacteria �x N2 which is released into soil & water & used by plants

Animals eat plants to receive N2 to be used tomake DNA, RNA & proteins. Animals excrete wastes.

Algae converts unusableNitrogen to usable

Lightning converts nitrogento ammonia and nitrate whichreturn to soil & water by rain

Too much nitrogen fromToo much nitrogen fromToo much nitrogen fromToo much nitrogen fromToo much nitrogen fromToo much nitrogen fromToo much nitrogen fromToo much nitrogen fromToo much nitrogen fromfertillizers returns to soil, contaminates ground water.

Plants and animals die,Plants and animals die,Plants and animals die,Plants and animals die,Plants and animals die,Plants and animals die,Plants and animals die,Plants and animals die,Plants and animals die,Plants and animals die,Plants and animals die,return to the soil,

Forest �res release Nthen goes back to the atmosphere.

Denitrifying bacteria convert

Too much nitrogen from

Animals eat plants to Animals eat plants to receive Nmake DNA, RNA & proteins. Animals excrete wastes.

Lightning converts nitrogenLightning converts nitrogento ammonia and nitrate whichto ammonia and nitrate whichreturn to soil & water by rainreturn to soil & water by rain

Inorganic phosphate (HPO4)

Incorporation into sedimentary rocks (as phosphates of Ca, Mg and Fe)

Excretion &decomposition

Dissolved Phosphates

Wastedecomposition

Weathering or erosion of rocks

Urine

Rocks contain

phosphate (PO43-)

Plant Uptake

Geological Upheaval