1.5 The Nitrogen Cycle
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21 Terms
Nitrogen cycle
Movement of nitrogen containing molecules between sources and sinks/reservoirs
Nitrogen sources
Release nitrogen into the atmosphere
Nitrogen sinks
Take the nitrogen out of the atmosphere
Nitrogen reservoirs
Hold nitrogen for relatively short periods of time
Examples of nitrogen reservoirs
Plants, soil, atmosphere
Main nitrogen reservoir
Atmosphere
What is nitrogen in the atmosphere?
Exist mostly as N2 gas and is not usable for plants and animals
What is nitrogen used for?
It is used in DNA and amino acids to make proteins
Nitrogen fixation
Process of N2 gas being converted into biologically available NH3 (ammonia) or NO3 (nitrate)
Bacterial fixation
Certain bacteria that live in soil or in symbiotic relationships with root nodules convert N2 into NH3 (ammonia)
Rhizobacteria
Live in root nodules of legumes and fix nitrogen and in return receive amino acids from the plants
Synthetic fixation
Humans combust Fossil Fuels to convert N2 gas into nitrate (NO3)
Assimilation
Plants and animals taking nitrogen in and incorporating it into their bodies
Examples of assimilation
Plant roots take in NO3 or NH3 from soil and animals assimilate nitrogen by eating plants or other animals
Amminoification
Soil bacteria, microbes, and decomposers convert waste and dead biomass back into NH3 and returning it back to soil
Nitrification
The conversion of NH4 into nitrate (NO2) and then nitrate (NO3) by soil bacteria
Denitrification
The conversion of soil nitrate (NH3) into nitrous oxide (N2O) gas which returns to the atmosophere
What is a human impact on the climate through the nitrogen cycle?
N2O gas (nitrous oxide)
Ammonia volatilization
When excess fertilizer use can lead to NH3 gas entering the atmosphere
NH3 gas in the atmosphere
Leads to acid precipitation and respiratory irritation in humans and animals and it also means less nitrogen stays in the soil
Leaching and eutrophication
Synthetic fertilizer use leads to nitrates (NO3) leaching, or being carried out of soil by water