GEOG 001 Chapter Notes - Chapter 10: Nitrogen Fixation

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Geog 1
Cos
Physical Geography
The Nitrogen Cycle
Readings PPSS Ch. 10 12
Nitrogen Cycle aka the Nitrogen Cascade
Atmosphere
Aquatic
Terrestrial
Energy production (natural and anthropogenic)
Food production
Human activities
A single molecule of nitrogen can be cycled through the whole process (cascading effect)
Eg, N atom starts as smog-forming compound.. cascade begins
Can form nitric acid in lakes and forest.. toxic to organisms
Same N atom in ocean.. forms red tides and dead zones
May finally return to atmosphere as greenhouse gas.. destroying ozone
We rely on N for many things, (eg stability in food production etc)
What is the primary source of Nitrogen?
The atmosphere (it makes up ~78% of air), however, most organisms cannot use the
atmospheric form of nitrogen
The nitrogen cycle is crucial, because it is how atmospheric N is changed into useful
form
Why is it so important to life?
Base of amino acids, used to build proteins we use proteins for almost anything
Also important part of DNA and RNA
Development of intensive agriculture and industrial processes, the nitrogen cycle has been
manipulated on a massive scale
much more nitrogen on earth/in atmosphere than in the past
Human sources vs. Natural sources of Nitrogen
Natural sources
N-Fixing Bacteria ~100 Tg/yr (?) Teragram/year
Marine Ecosystems ~15 Tg/yr
Lightning 15 Tg/yr
Human sources
N-fixing crops ~30 Tg/yr
Fertilizer Industry ~80 Tg/yr
Burning fossil fuels 35 Tg/yr
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