Biogeochemical Cycles - Physical

Question 1

What are some human impacts on the carbon cycle?

Answer 1

Deforestation / Afforestation
Livestock farming
Padi fields
Soil disturbance (ploughing)
Use of fossil fuels
Forest fires

Question 2

How can the carbon cycle be managed in a more sustainable way?

Answer 2

• Conservation of carbon stores (peat bogs etc).
• Use of alternative to fossil fuels (renewable).
• Carbon sequestration.

Question 3

How can CO2 be removed from the exhaust gases of fossil fuel combustion?

Answer 3

• Dissolving in a solvent.
• High pressure membrane filtration.
• Cryogenic separation.

Question 4

How is CO2 stored (during CCS)?

Answer 4

Commonly stored underground in things like depleted aquifers or oil fields.

Question 5

What is the importance of nitrogen? Limitation?

Answer 5

• All living organisms need nitrogen.
• Impossible for most organisms to extract from air.

Question 6

What can turn N2 into other forms for others to use?

Answer 6

Nitrifying bacteria.

Question 7

What are the three types of nitrogen fixation?

Answer 7

• Atmospheric fixation e.g. lightning.
• Industrial fixation e.g. Haber process.
• Biological fixation - bacteria (live in legumes/soil). Some turns it into ammonia, some taken up by host plant.

Question 8

What are some human influences on the nitrogen cycle?

Answer 8

• Flooding (denitrification).
• Combustion of fossil fuels in cars = NOx
• Using fertilisers = Haber process (artificial nitrogen fixation).
• Deforestation = erosion + runoff = leaching.
• Planting beans and peas = nitrogen fixation (root nodule bacteria).
• Drainage/ploughing = more aerobic soil = more nitrification.

Question 9

What is eutrophication?

Answer 9

1) Excessive nutrients from fertilisers carried deep into soil, carried to streams and rivers.
2) Pollutants cause aquatic plant growth of algae + others.
3) Algae blooms, prevents sunlight reaching other plants, depleting oxygen in water.
4) Dead plants broken down by decomposers, depletes oxygen further.
5) Oxygen level reaches a point where no life can exist - existing plants/animals die.

Question 10

How can the impact of fertilisers on the nitrogen cycle be reduced?

Answer 10

• Don’t put out when likely to rain.
• Ploughing/draining the land = more nitrifying bacteria.
• Planting more legumes = increases nitrogen compounds in soil.
• Crop rotation.

Question 11

How can the impact of biological waste on the nitrogen cycle be reduced?

Answer 11

• Ploughed into the soil / applied to surface. Produces a fertiliser with a better C:N ratio.

Question 12

What are soil management practices to reduce the impact on the nitrogen cycle?

Answer 12

• Low-tillage techniques to reduce soil disturbance.
• Minimal use of pesticides that harm soil biota.

Question 13

Name a decomposer bacteria.

Answer 13

Saprobionts.

Question 14

What is the biological oxygen demand (BOD)?

Answer 14

Oxygen needed by all living organisms in water - mainly bacteria.

Question 15

Why do living organisms need phosphorous?

Answer 15

To make molecules like ATP, DNA, molecules in bones etc.

Question 16

Is the phosphorous cycle a slow or fast cycle? Why?

Answer 16

Slow cycle.

Has no gas phase and has low solubility.

Question 17

In what form do plants take up phosphorous?

Answer 17

Phosphate

Question 18

How can amount of phosphorous compounds in soil be increased?

Answer 18

• Manure from cows.
• Decomposition of detritus.
• Weathering
• Urine.

Question 19

How is phosphorous transferred from the ocean to the land?

Answer 19

1) Phosphorous is in the rocks (lithification).
2) The rock is uplifted out of sea.
3) Rock is weathered.
4) Also can be mined/quarried.