1. The Nitrogen Cycle

2. What is nitrogen?

3. Periodic Table
Nitrogen is an element

4. Where is nitrogen found in the environment?

5. The largest single source of nitrogen is in the atmosphere.
Nitrogen makes up 78% of our air!

6. What happens to atmospheric nitrogen (N2) in the nitrogen cycle?

7. Atmospheric nitrogen is converted to ammonia or nitrates.
Atmospheric Nitrogen (N2) N N
Nitrates (NO3)
Nitrogen combines with Oxygen to make Nitrates
Ammonia (NH3)
Nitrogen combines with Hydrogen to make Ammonia

8. Why does atmospheric nitrogen need to be converted?

9. It is one of nature’s great ironies…
Nitrogen is an essential component of DNA, RNA, and proteins—the building blocks of life.
Although the majority of the air we breathe is nitrogen, most living organisms are unable to use nitrogen as it exists in the atmosphere!

10. How does atmospheric nitrogen get changed into a form that can be used by most living organisms?

11. By traveling through one of the three processes in the Nitrogen Cycle!
(1) Nitrogen Fixation
(3) Denitrification
Nitrogen Cycle
(2) Nitrification

12. The first process in the nitrogen cycle is… Nitrogen Fixation!

13. What is “nitrogen fixation” and what does it mean to say nitrogen gets “fixed”?

14. “Nitrogen Fixation” is the process that causes the strong two-atom nitrogen molecules found in the atmosphere to break apart so they can combine with other atoms and be used by plants Nitrogen gets “fixed” when it is combined with oxygen or hydrogen. N N
Hydrogen
Oxygen
Hydrogen N N N N
Oxygen

15. Symbiotic Relationship Bacteria
Biological Fixation (where MOST nitrogen fixing is completed) There are two types of “Nitrogen Fixing Bacteria”
Free Living Bacteria
(“fixes” 30% of N2)
Symbiotic Relationship Bacteria
(“fixes” 70% of N2)

16. It travels through the second process of the nitrogen cycle called Nitrification!
The conversion of ammonium to nitrites and then nitrates by the bacteria
(1) Nitrogen Fixation
(2) Nitrification

17. How does nitrogen reenter the atmosphere in the nitrogen cycle?

18. Through the third process called denitrification!
(1) Nitrogen Fixation
(3) Denitrification
(2) Nitrification

19. What does denitrification do?

20. Denitrification converts nitrates (NO3) in the soil to atmospheric nitrogen (N2) replenishing the atmosphere.
Nitrogen in atmosphere (N2)
Nitrates (NO3) in Soil

21. How does the denitrification process work?
Nitrates in soil

22. Ways that nitrogen returns to the atmosphere…
Emissions from industrial combustion and gasoline engines create nitrous oxides gas (N2O).
Volcano eruptions emit nitrous oxides gas (N2O).