Topic 7: Carbon Cycle

Question 1

What does it mean that the carbon cycle is in a state of dynamic equilibrium naturally?

Answer 1

• the processes cancel each other out
• there is little to no change in the amount of carbon in each reservoir in the cycle

Question 2

What do humans do to the natural equilibrium that the carbon cycle is in?

Answer 2

-they alter the dynamic equilibrium it is in because they alter many of the processes in the carbon cycle
- so some reservoirs become depleted, whereas other reservoirs of carbon are increased

Question 3

Main reservoirs of the carbon cycle

Answer 3

Lithosphere,biosphere,hydrosphere,atmosphere

Question 4

Stores of carbon in the lithosphere

Answer 4

Carbonaceous rocks e.g. limestone
Fossil fuels

Question 5

Stores of carbon in the biosphere

Answer 5

Carbohydrates,proteins, lipids
Living organisms
Dead organic matter

Question 6

Stores of carbon in the hydrosphere

Answer 6

Hydrogen carbonate ions
Dissolved carbon dioxide

Question 7

Stores of carbon in the atmosphere

Answer 7

Carbon dioxide, methane, carbon monoxide

Question 8

5 main processes of the carbon cycle

Answer 8

Respiration
Food webs
Photosynthesis
Fossilation
Combustion

Question 9

Respiration as a process in the carbon cycle

Answer 9

Releases energy captured in photosynthesis, which is used to drive metabolic processes
Aerobic respiration returns carbon to atmosphere as CO2
It breaks down organic molecules more completely than anaerobic respiration and releases more energy
Anaerobic returns carbon to the atmosphere as methane

Question 10

Food webs as a process of the carbon cycle

Answer 10

Carbs,lipids,proteins are produced by plants
Some of these are eaten by herbivores, which may then be eaten by carnivores
These feeding relationships form food webs

Question 11

Photosynthesis as a process in the carbon cycle

Answer 11

Captures light energy using chlorophyll, and converts low—energy substances like CO2 and H2O into high energy carbs, which might be converted to other substances like proteins and lipids

Question 12

Combustion as a process in the carbon cycle

Answer 12

Burning of organic matter
Releases carbon dioxide
Natural fires in forests & grasslands may be started by lightning

Question 13

What is fossilisation?

Answer 13

The incomplete combustion of dead organic matter
Often under anaerobic conditions and can produce substances that form long-term carbon stores

Question 14

Fossilisation as a process of the carbon cycle

Answer 14

Can produce long term carbon stores
E.g. organisms with exoskeletons, like coral, contain calcium carbonate
This may produce rocks like limestone, which contain most of the carbon in the lithosphere

Question 15

6 ways that humans affect the carbon cycle

Answer 15

Changes to respiration
Changes to photosynthesis
Carbonic acid concentration in the sea
Biomass movements
Combustion
Methane releases from fossil fuels

Question 16

How do humans affect the carbon cycle through combustion?

Answer 16

Increase CO2 in the atmosphere by the combustion of fossil fuels and wood

Question 17

How do humans affect the carbon cycle by increasing methane?

Answer 17

Methane may be released into the atmosphere during the extraction of fossil fuels

Question 18

How do humans alter the carbon cycle by biomass movements?

Answer 18

Humans move large amounts of carbon in biomass between areas, this can have environmental impacts because it reduces local changes
E.g. movement of marine biomass to terrestrial ecosystem by fishing
- movement of biomass into the sea when sewage is discharges

Question 19

How do humans increase the carbonic acid concentration in the sea?

Answer 19

More CO2 in the atmosphere
More CO2 is dissolved in the sea
More hydrogen ions
Higher PH

Question 20

How do humans cause changes to aerobic respiration?

Answer 20

Ploughing increases the oxygen supply to decomposers,so more aerobic decomposition and the amount of carbon in dead organic matter in the soil is reduced and the amount in the atmosphere is increased

Question 21

How do humans cause changes to anaerobic respiration?

Answer 21

Methane is produced by anerobic respiration
Anerobic environments: rice padi fields,landfill,anaerobic sediments in reservoirs, livestock intestines
Anerobic environments are destroyed by the drainage of marshlands or peat bogs

Question 22

How do humans cause changes in photosynthesis?

Answer 22

Deforestation, afforestation
Marine pollution itch toxic material reduces phytoplankton, so more CO2 in atmosphere not marine sediments
Algae that live on ice will die when it melts

Question 23

Suggest 4 ways that the carbon cycle can be sustainably managed

Answer 23

Conservation of biomass carbon stores
Use of alternatives to fossil fuels
Carbon sequestration
CCS-carbon capture and storage

Question 24

Explain the conservation of biomass carbon stores

Answer 24

Habitats e.g. peat bogs are protected from exploitation or land use change to prevent further CO2 releases

Question 25

Explain the use of alternatives to fossil fuels

Answer 25

Renewable energy sources and nuclear power to produce lower CO2 emissions than fossil fuels

Question 26

Explain carbon sequestration

Answer 26

Large scale tree planting will remove a lot of CO2 from the atmosphere then act as a reservoir when trees are fully grown
Still a store if they are kept and used to build houses

Question 27

3 elements of CCS

Answer 27

Pre-combustion technology
Post-combustion technology
Storage

Question 28

What is pre-combustion technology?

Answer 28

Changing the fuel or way that it is combusted, may be more expensive and require new technology bit makes CO2 removal more efficient

Question 29

example of pre-combustion technology

Answer 29

Whilst post-combustion technology is useful for small sources, this captures carbon before fuel is used so it isnt released
E.g. gasification turns coal into gaseous hydrogen and CO2 , when burnt the excess gas+water not CO2

Question 30

Post combustion technology

Answer 30

Carbon dioxide can be removed from the exhaust gases of fossil fuel combustion using several methods
E.g. dissolving in solvent,cryogenic separation,graphene absorption

Question 31

Storage (CCS)

Answer 31

Proposals to use underground geological structures to store CO2
Or use it in secondary oil recovery