APES Nitrogen Cycle

What is nitrogen cycle

Movement of nitrogen containing molecules between sources and sinks/reservoirs

N₂

Nitrogen gas

NH₃

Ammonia

 NO₃

Nitrate

NH₄

Ammonium

NO₂

Nitrite

N₂O

Nitrous oxide

Main N reservoir, how much % of it does N make up, what form is N in?

Atmosphere, 78%, N₂

Why is nitrogen important

Limiting nutrient - all organisms need it for DNA and amino acids

What is nitrogen fixation

N₂ gas from atmosphere converted to biologically available NH₃ ammonia or NO₃ nitrate

What performs nitrogen fixation

Bacteria in the soil, or in legume root nodules convert N₂ to NH₃, lighting can too

Synthetic fixation

Humans combust fossil fuels, converting N₂ into NO₃ (synthetic fertilizers)

Assimilation

Organisms taking nitrogen, incorporating it into their body

Plant roots take in NO₃ or NH₃ from the soil, animals eat plants or other animals

Ammonification

Bacteria/decomposers convert waste, dead biomass to NH₃, back to soil

Nitrification

Ammonium NH₄ converted to nitrite NO₂ and then nitrate NO₃ by bacteria

Denitrification

Converts soil NO₃ into N₂O (nitrous oxide), returns to atmosphere

Nitrogen impact on climate

N₂O warms earth, produced by denitrification of nitrate in agricultural soils

Ammonia volatilization

Excess fertilizer use = NH₃ gas in atmosphere (acid rain, bad air)

Leaching

Synthetic fertilizer use leads to NO₃ being carried out of soil by water

Eutrophication

Excess nutrients = algae growth, blocks sunlight, kills aquatic plants (result of leaching)