Nitrogen Cycle

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Human Alteration of the Global Nitrogen Cycle

What is Nitrogen?
Nitrogen is the most abundant element in the Earth’s atmosphere. Nitrogen makes up 78% of the troposphere. Nitrogen cannot be absorbed directly by the plants and animals until it is converted into compounds they can use. This process is called the Nitrogen Cycle.

Heather McGraw, Mandy Williams, Suzanne Heinzel, and Cristen Whorl, Give SIUE Permission to Put Our Presentation on E-reserve at Lovejoy Library.

The Nitrogen Cycle

How does the nitrogen cycle work?
Step 1- Nitrogen Fixation- Special bacteria convert the nitrogen gas (N2 ) to ammonia (NH3) which the plants can use. Step 2- Nitrification- Nitrification is the process which converts the ammonia into nitrite ions which the plants can take in as nutrients. Step 3- Ammonification- After all of the living organisms have used the nitrogen, decomposer bacteria convert the nitrogen-rich waste compounds into simpler ones. Step 4- Denitrification- Denitrification is the final step in which other bacteria convert the simple nitrogen compounds back into nitrogen gas (N2 ), which is then released back into the atmosphere to begin the cycle again.

How does human intervention affect the nitrogen cycle?
Nitric Oxide (NO) is released into the atmosphere when any type of fuel is burned. This includes byproducts of internal combustion engines. Nitrous Oxide (N2O) is released into the atmosphere through bacteria in livestock waste and commercial fertilizers applied to the soil. Removing nitrogen from the Earth’s crust and soil when we mine nitrogen-rich mineral deposits. Discharge of municipal sewage adds nitrogen compounds to aquatic ecosystems which disrupts the ecosystem and kills fish.

Production and Use of Nitrogen Fertilizers

Nitrogen Fertilizer
#1 Contributor to new nitrogen in the global cycle First developed during WWI Use has grown exponentially Can actually increase the nitrogen so much that soil fertility actually decreases...
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