biogeochemical cycles

1. Biogeochemical cycles

2. The Water Cycle

4. The Water Cycle

5. (1) Evaporation: During part of the water
cycle, the sun heats up liquid water and
changes it to a gas by this process.
.
(2) Transpiration: The process of evaporation
from plants.

6. (3) Condensation: As water (in
the form of gas) rises higher in
the atmosphere, it starts to cool
and become a liquid again. This
process is called condensation.
When a large amount of water
vapor condenses, it results in the
formation of clouds.
(4) Precipitation: When the
water in the clouds gets too
heavy, the water falls back to
the earth. This is called
precipitation.

7. (5) Runoff: When rain falls on the land, some of
the water is absorbed into the ground forming
pockets of water called groundwater. Most
groundwater eventually returns to the ocean.
Other precipitation runs directly into streams or
rivers. Water that collects in rivers, streams, and
oceans is called runoff.

8. THE NITROGEN CYCLE

9. Sources
• Lightning
• Inorganic fertilizers
• Nitrogen Fixation
• Animal Residues
• Crop residues
• Organic fertilizers

10. Forms of Nitrogen
• Urea  CO(NH2)2
• Ammonia  NH3 (gaseous)
• Ammonium  NH4
• Nitrate  NO3
• Nitrite  NO2
• Atmospheric Dinitrogen N2
• Organic N

11. Nitrogen Cycles
• Ammonification/mineralization
• Immobilization
• Nitrogen Fixation
• Nitrification
• Denitrification

12. Sediments
Nitrification
Root
uptake
Biological
fixation
Nitrification
Ammonium NH4
+
Ammonification
Nitrite NO2
-
Dissolved in water
Denitrification
Leaching
Nitrate
NO3
-
Soil organic nitrogen
Atmospheric
fixation
Industrial
fixation
Plant protein
Animal
protein
Atmospheric Nitrogen

13. Ammonification
• Nitrogen enters the soil through the
decomposition of protein in dead organic
matter
Amino acids + 11/2O2  CO2 + H2O + NH3 + 736kJ
• This process liberates a lot of energy
which can be used by the saprotrophic
microbes

14. Nitrification
• This involves two oxidation processes
• The ammonia produced by ammonification is an
energy rich substrate for Nitrosomas bacteria
They oxidise it to nitrite:
NH3 + 11/2O2  NO2
- + H2O + 276kJ
This in turn provides a substrate for Nitrobacter
bacteria oxidise the nitrite to nitrate:
NO2
- + 1/2O2  NO3
- + 73 kJ
• This energy is the only source of energy for
these prokaryotes
• They are chemoautotrophs

15. Nitrogen Fixation
• Energy intensive process :
• N2 + 8H+ + 8e- + 16 ATP = 2NH3 + H2 +
16ADP + 16 Pi
• Performed only by selected bacteria and
actinomycetes
• Performed in nitrogen fixing crops
(ex: soybeans)

16. Atmospheric nitrogen
fixation
• Electrical storms
• Lightning provides sufficient energy to
split the nitrogen atoms of nitrogen gas,
• Forming oxides of nitrogen NOx and NO2

17. Denitrification
• Removes a limiting nutrient from the
environment
• 4NO3
-
+ C6H12O6 2N2 + 6 H20
• Inhibited by O2
• Not inhibited by ammonia
• Microbial reaction
• Nitrate is the terminal electron acceptor

18. CARBON CYCLE

19. Carbon in Atmosphere
Plants use
carbon to make
food
Animals eat
plants and
take in carbon
Plants and
animals die
Decomposers
break down dead
things, releasing
carbon to
atmosphere and
soil
Bodies not
decomposed —
after many
years, become
part of oil or coal
deposits
Fossil fuels are
burned; carbon
is returned to
atmosphere
Carbon slowly
released from
these substances
returns to
atmosphere

20. OXYGEN CYCLE