3.2.4 Biogeochemical Cycles

Question 1

Process of carbon cycle affected by humans

Answer 1

• Photosynthesis.
• Aerobic respiration.
• Anaerobic respiration.
• Combustion.
• CO2 dissolving in the sea/exsolving from the
sea.
• Biomass movements.
• Changes in carbon reservoirs.
• Increased atmospheric concentration of CO2.
• Less soil dead organic matter.
• Increased concentrations of dissolved CO2,
carbonic acid, hydrogen carbonate ions.
• Increased atmospheric concentration of
methane.
• Reduced amount of carbon in plant biomass.
• Reduced amount of carbon in fossil fuels.

Question 2

Sustainable management of c cycle

Answer 2

• Alternatives to fossil fuel use.
• Carbon sequestration.
• Carbon Capture and Storage (CCS).
• Matching afforestation to deforestation.
• Increasing soil organic matter.
• Conservation of peat bogs.

Question 3

Nitrogen cycle and human influences

Answer 3

• The Haber Process fixing nitrogen in ammonia, mainly to produce agricultural fertilisers.
• Land drainage increases nitrogen fixation and reduces denitrification.
• The growth of legume crops increases nitrogen fixation in plant proteins.
• Sewage disposal increases nitrate movements to rivers and the sea, together with phosphates, causes eutrophication.
• Combustion processes cause nitrogen and oxygen to react, producing oxides of nitrogen.
• Decomposition and ammonification affected by organic waste disposal policies.

Question 4

Consequences of nitrogen reservoirs

Answer 4

• eutrophication
• global climate change
• NOx toxicity
• photochemical smogs

Question 5

Methods of counteracting anthropogenic nitrogen movements:

Answer 5

• reduced combustion processes
• use of natural nitrogen fixation processes
instead of the Haber process
• management of biological wastes
• methods of reducing soil nitrate leaching.

Question 6

Phosphorus cycle

Answer 6

Phosphorus compounds are mobilised in more soluble forms for use in agricultural fertilisers.
Eutrophication is caused by nutrient enrichment of water bodies, combined with the effect of nitrates

Question 7

Sustainable management of p cycle

Answer 7

• the use of biological wastes as fertilisers
• breeding of crops that absorb phosphates more
efficiently
• providing suitable conditions for soil mycorrhizal
fungi increases phosphate uptake combustion processes.