Biogeochemical Cycles

Define a Reservoir

Temporary holding area → contain an amount of a substance

Define fluxes

Flows of a substance → describe an amount of a substance per timestep that is exchanged between reservoirs (e.g. kilograms of carbon per year)

What are the key processes in the water cycle?

Evaporation, condensation, precipitation, infiltration, runoff, and transpiration.

2. Q: What are the key processes in the carbon cycle?

A: Photosynthesis, respiration, decomposition, combustion, and carbon sequestration.

3. Q: What are the key processes in the nitrogen cycle?

A: Nitrogen fixation, nitrification, assimilation, ammonification, and denitrification.

4. Q: What are the key processes in the phosphorus cycle?

A: Weathering of rocks, absorption by plants, consumption by animals, decomposition, and sedimentation.

5. Q: What is the fast carbon cycle?

A: The movement of carbon through living organisms, atmosphere, and surface oceans within years to decades.

6. Q: What is the slow carbon cycle?

A: The movement of carbon through rocks, sediments, and deep oceans over thousands to millions of years.

7. Q: What is the main difference between the fast and slow carbon cycles?

A: The fast cycle involves biological processes and short time scales; the slow cycle involves geological processes and long time scales.

8. Q: What is silicate weathering?

A: A chemical process where silicate rocks react with carbonic acid, removing CO₂ from the atmosphere and storing it in rocks.

9. Q: What is carbonate weathering?

A: A process where carbonate rocks dissolve in carbonic acid, temporarily releasing CO₂ back into the atmosphere.

10. Q: How does silicate weathering differ from carbonate weathering in terms of carbon storage?

A: Silicate weathering removes CO₂ from the atmosphere long-term, while carbonate weathering recycles it more quickly.

11. Q: How do plants link the water and carbon cycles?

A: Plants absorb CO₂ during photosynthesis and release water vapor through transpiration.

12. Q: What is residence time in a biogeochemical cycle?

A: The average time a substance spends in a reservoir.

13. Q: How is residence time calculated?

A: Residence time = Reservoir size ÷ Flux (in appropriate time units).

14. Q: If a reservoir contains 1000 units of a substance and the flux is 100 units/year, what is the residence time?

A: 10 years.

15. Q: Why is it important to consider the correct time scale when calculating residence time?

A: To ensure the units of reservoir and flux match, providing an accurate estimate.

Describe groundwater reservoirs

residence time of water can be millennia

unsutainable groundwater extraction

What are the different forms carbon can be found in throughout the carbon cycle?

• atmosphere = methane and carbon dioxide

• photosynthetic organisms = carbohydrates

• ocean = carbonate, bicarbonate, carbon dioxide

  • deep sea is largest carbon reservoir

Why is there so much carbon in the ocean?

• fractionation into dissolved inorganic carbon

  • co2 + h20 = h2co3

  • h2co3 → H+ + HCO3

• higher temperatures make the co2 more soluble

• biological pump

  • construction of soft tissue by photosynthesis

  • construction of calcareous skeletons

What is the Haber & Bosch Method?

COnversion of N2 → NH3

ethical question - nazis