1. Nitrogen Cycle

2. Forms of Nitrogen Ammonia: NH3+ Ammonium: NH4 Nitrite: NO2-
Nitrate: NO3-
Gas: N2
Nitrogen Oxide: NO
Dinitrogen oxide: N2O

3. Each spot on the cycle is a reservoir of nitrogen; a place where it is stored or available in some form
Atmosphere
Living organisms
Soils
Oceans

4. 78% of the atmosphere is nitrogen
Gaseous nitrogen (N2) is not usable to living things
Nitrogen fixation must take place

5. Nitrogen fixation- processing of nitrogen into forms that are usable by living things
1 of 4 methods
Lightning
Bacteria
Industrial fixation: the Haber-Bosch processes convert N2 into fertilizer
Combustion of fossil fuels
Bacteria: have an enzyme that breaks down N2 into ammonia

6. Assimilation Plants absorb nitrogen through roots
Bacteria can also take up N
Animals get nitrogen from eating plants or other animals
N is important for making amino acids and proteins
Also important part of DNA and RNA

7. Ammonification Organisms die and are broken down by decomposers
Bacteria convert the nitrates into ammonia

8. Nitrification
Ammonium absorbed by soil and then changed by bacteria to nitrite and nitrate
Nitrate can then either be used by plants or go through denitrification

9. Denitrification Turn nitrates back into nitrogen gas
Completes the nitrogen cycle, putting N back into the atmosphere

10. Anaerobic Ammonium Oxidation
Nitrite and Ammonium converted straight to N2
Occurs mostly in oceans

11. Humans affect the Nitrogen Cycle
N-rich fertilizers put N into water; can be toxic to babies
Fertilizers, cattle and feedlots, and industrial sources also release dinitrogen oxide (N2O) into the air; contributes to global warming

12. Humans and the N-cycle
Burning fossil fuels and forests releases Nitrogen oxide; contributes to smog and acid rain
Wastewater treatment plants release ammonia, toxic to fish