1. Biogeochemical Cycles - 1
1. What are systems?
2. What are biogeochemical cycles?
3. Why are they important?
4. What is common about them?
5. Carbon and nitrogen cycles
6. Focus on the Water Cycle

2. What is a system?
System: a collection of matter, parts, or components which are included inside a specified, often arbitrary, boundary. Example: Ecosystem
Systems often have inputs and outputs.
For dynamic systems, by definition, one or more aspects of the system change with time.
Example of a simple dynamic system: bathtub or your ‘bank’ account.
Flux
The boundary of a dynamic system is chosen for convenient conceptual separation for the system
Pool

3. Carbon dioxide
C-pool
Sugar
Night

4. What are biogeochemical cycles?
Earth system has four parts
Atmosphere
Hydrosphere
Lithosphere
Biosphere
Biogeochemical cycles: The chemical interactions (cycles) that exist between the atmosphere, hydrosphere, lithosphere, and biosphere.
Abiotic (physio-chemical) and biotic processes drive these cycles
Focus on carbon and water cycles (but could include all necessary elements for life). N - cycle weakly touched on!

5. What is common amongst them?
Each compound (water, carbon, nitrogen) typically exists in all four parts of the Earth System
There are
‘Pools’
Fluxes in and out of pools
Chemical or biochemical transformations
Transformations
are important
can lead to positive & negative consequences

6. Transformations Examples of Transformations
Carbon cycle: Organic compounds to CO2 (processes: respiration, decomposition, or fire)
Carbon cycle: CO2 to organic compounds (process: photosynthesis)
Nitrogen cycle: N2 to NO3 (atmospheric nitrogen to plant utilizable nitrate) (process: N-fixation)
Nitrogen cycle: N2 to NH3 (plant utilizable ammonia) (process: Haber-Bosch Industrial N-fixation)
Water cycle: Liquid water to water vapor (process: evaporation and evapo-transpiration)
Water cycle: Water vapor to liquid water (process: condensation)

7. Carbon Cycle
5000

8. Carbon Cycle Data Burning of fossil fuels Land conversion Cement
760 59
Burning of fossil fuels
Land conversion
Cement
Role of Oceans
Role of terrestrial plants (trees & soils)
Lithosphere

9. Changes in Atmospheric C02 - 1
Dr. Pieter Tans, NOAA/ESRL (

10. Changes in Atmospheric C02 - 2

11. Key Aspects of the Carbon Cycle
Carbon is the skeleton of all life.
Carbon dioxide is a critical gas:
Taken up by plants in photosynthesis
Released by plants and animals in respiration
Released during decomposition (and fires)
Greenhouse gas (greenhouse effect - your car in the sun)

12. Nitrogen Cycle Forms of Nitrogen (N2)
N2 - inert gas, 78% of the atmosphere
NO, N20, NO2 - other gases of nitrogen, not directly biologically important. Part of the gases found in smog.
NO3- (nitrate) and NH4+ (ammonium) -- ionic forms of nitrogen that are biologically usable.

13. Nitrogen Cycle Forms & Sources of biologically available nitrogen (N2)
For plants
NO3- (nitrate)
NH4+ (ammonium)
Sources: N-fixation by plants (N2 to NH3 and N2 to NO3), lightening, bacteria decomposition of organic N (amino acids & proteins)
For animals
Organic forms: amino acids and proteins (from plants or other animals)

14. Nitrogen Cycle Losses of nitrogen from system
In bogs, lakes (places of low oxygen), NO3- is converted to N2 by bacteria (get their oxygen from the NO3)
Volatilization of NH4+ (urea) to ammonia gas (NH3) - warm, dry conditions.
Leaching of NO3- (nitrate)
Erosion
Fire (combustion)

15. Nitrogen Sources over time

16. Nitrogen Cycle: Key Points
Nitrogen is in the atmosphere as N2 (78%)
N2 is an inert gas and cannot be used by plants or animals
N2 can be converted to a usable form via
Lightening
N-fixing plants and cyanobacteria
Industrial process (energy intensive)
Nitrogen limits plant growth
Nitrogen is easily lost from biological systems

17. Summary 1. What are systems? 2. What are biogeochemical cycles?
3. Why are they important?
4. What is common about them?
5. Carbon and nitrogen cycles