W + C: The Carbon Cycle

Question 1

What is a carbon sink?

Answer 1

store that absorbs more than it releases

Question 2

What is a carbon source?

Answer 2

releases more carbon than it absorbs.

Question 3

Why is the carbon cycle important?

Answer 3

• Carbon is a basic chemical element needed by all animals and plants to survive. Recycling of carbon is essential for life on earth: food for animals and plants, energy sources for industrial development, etc. concerns over increasing levels in the atmosphere
• the Carbon Cycle is the route carbon follows on Earth. Transformed from organic carbon to inorganic carbon and back again. The primary source of carbon is the Earths interior. its stores are all 5 of the subsystems and transfers.

Question 4

Where is carbon in the Lithosphere?

Answer 4

Over 99.9% of the carbon on Earth is stored in sedimentary rocks, e.g. limestone (marine sediments and sedimentary rock have 100,000 amount in billions of metric tonnes- a long term store, also fossil fuel deposits at 4,000 BMT hydrocarbons are important long term stores of carbon)

Question 5

Where is carbon in the atmosphere?

Answer 5

Carbon is stored as CO2 and methane in the atmosphere (750 billion metric tonnes - has been increased due to power stations, vechiles and deforestation)

Question 6

Where is carbon in the biosphere?

Answer 6

Carbon is stored in the tissues of living organisms - it’s trasnferred to the soil when they die and decay (1500 billion metric tonnes of carbon in the soils containing rotting organic matter and 560 billion MT of carbon stored in terrestrial plants, which store carbon and transfer into soil)

Question 7

Where is carbon in the hydrosphere?

Answer 7

Oceans are the second largest store -CO2 is dissolved in rivers, lakes and oceans (38,000 billion MT carbon absorbed from the air)

Question 8

Where is carbon in the cryosphere?

Answer 8

The smallest carbon store, most of the carbon is in the soil in areas of permafrost where decomposing organisms have frozen in the ground

Question 9

What are the global stores on Earth?

Answer 9

• carbon held in stores, changes over timescales of minutes to millions of years, we call these changes fluxes.
• Carbon stores can be identified at all geographical scales and have a geographical component - they are not evenly distributed.

Question 10

What is the global pattern of vegetation carbon store?

Answer 10

• Some regions of the world (e.g. Sahara desert) have virtually no plant storage
• Scientists have noticed carbon uptake is increasing in Northern Hemisphere, but less carbon being absorbed in the tropics and Southern Hemisphere.
• Oceans are larger in the Southern Hemisphere
• Different amounts of carbon are stored worldwide and one of the stores that is currently changing is trees.

Question 11

What is the movement of carbon?

Answer 11

• Each store can be a carbon source (release more) or a carbon sink (absorb more)
• Size of store fluctuates over time and space
• Fast Carbon cycles (change rapidly) and slow carbon cycles (timescale of millions of years) - these timescales will have an impact on feedback loops.

Question 12

What are the fast and slow movements of carbon?

Answer 12

— Fast organic; minutes to centuries, organic carbon through living things between atmosphere, soil and biosphere
— Fast non-organic; ocean-atmosphere exchange
— Slow Organic; remains of marine creatures and terrestrial forests, as fossil deposits of oil, coal and gas
— Slow Non-organic; carbon from atmosphere to hydrosphere and then to sedimentary stores in the lithosphere, recycled by volcanic activity.

Question 13

What is the process of photosynthesis? (Fast carbon)

Answer 13

plants use light energy from sun to produce carbohydrates in the form of glucose
- plants absorb light energy using chlorophyll in leaves
- absorbed energy converts CO2 from air and water (from soil) to glucose. oxygen is also released
- Some glucose is used in respiration, rest is converted back to starch, which is insoluble but can be converted back into glucose for respiration.
- CO2 + water + light energy = glucose + oxygen

Question 14

what is the process of respiration? (Fast carbon)

Answer 14

Chemical process that happens in all cells and common for plants and animals
- Plants break down glucose (carbohydrates) for energy to carry out respiration
- energy can be used for growth and repair, movement and control of body temp in mammals
- CO2 then returned to the atmosphere by exhaled air. Methane (which contains carbon) is also released.

Question 15

What is the process of decomposition? (Fast carbon)

Answer 15

when organisms die, they are consumed by decomposers such as bacteria, fungi and earthworms
- During decomposition, carbon from bodies is returned to the atmosphere as CO2.
- Some organic material passes into the soil where it may be stored for hundreds of years.

Question 16

What is the process of burial and compaction? (Slow carbon)

Answer 16

• organic matter is buried by sediments and becomes compacted. Over millions of years, these organic sediments containing carbon may form hydrocarbons e.g. oil and coal.
• Corals and shelled organisms, take CO2 from the water and convert it into calcium carbonate to build their shells. When die, the shells lay on the sea bed. Some carbonate dissolves, releasing CO2. The rest compacts forming limestone, storing carbon for millions of years.

Question 17

What is the process of weathering? (Slow carbon)

Answer 17

• involves the breakdown or decay of rocks in their original place or close to the surface
• When CO2 is absorbed by rainwater, it forms an acidic carbonic acid
• after a series of chemical reactions, rocks will slowly dissolve with the carbon being held in the solution
• This is transported via the water cycle to the oceans and the carbon cycle can then be used to build the shells of marine organisms.

Question 18

What is the process of carbon sequestration? (Slow and fast carbon)

Answer 18

the transfer of carbon from the atmosphere to the plants, soils, rock formations and oceans.
• It is both a natural and human process
• Carbon Capture and Storage (CCS) is recent term to describe carbon sequestration by humans.

Question 19

What is geological sequestration?

Answer 19

A human process
- CO2 is captured at its source (e.g. power plants) and then injected in liquid form to store underground, e.g. depleted oil and gas reserves. This techniques is still in experimental stage.

Question 20

What is terrestrial or biological sequestration?

Answer 20

plants capture CO2 from the atmosphere and then store it as carbon in the stems and roots of the plants as well as in the soil.

Question 21

What is an example of sequestration?

Answer 21

Planned grazing will reverse desertification. Increase animals grazing on land, then move them. This enriches soil without killing plant life. Enough carbon out of the atmosphere to take atmospheric carbon back to pre-industrial levels - also increases biodiversity.

Question 22

What is a sere?

Answer 22

• a sere is a succession that relates to a specific environment. Each stage of the succession is called a seral stage.
• A lithosere is a vegetation succession that occurs on bare rock. Other seres include:
  —> Hydrosere (water - freshwater pond)
  —> Halosere (salt - coastal salt marsh)
  —> Psammosere (coastal sand - sand dunes)

Question 23

What is the terrestrial carbon cycle (the lithosere) —> the vegetation succession?

Answer 23

1. Rock exposed, e.g. due to glacial retreat - weathering releases carbon which is then often dissolved in water, or due to tectonic uplift, raised beach or volcanic eruption
2. Vulnerable to weathering (rain has absorbed CO2)
3. Rock is slowly broken down - carbon is in the remaining water.
4. This, through transfers within the water cycle, goes to the other stores (atmosphere, hydrosphere and biosphere)
5. Vegetation grows on the exposed rock - Litchens and mosses are the first to colonise
6. They take their nutrients directly from the rock
7. carbon exchange takes place (respiration and photosynthesis)
8. Organic matter and leaf litter is added to the broken rock fragments
9. Beginning of soil formation and as it develops it can support further vegetation
10. Soil can absorb and store carbon
11. Plant species becomes more diverse
12. Different habitats are established

Question 24

What’s the continental scale (geological) for carbon cycle at different scales?

Answer 24

1. From the atmosphere, CO2 is removed by dissolving in water, forming carbonic acid (CO2+H2O—>H2CO3 (carbonic acid))
2. Reaches the surface as rain, and reacts with the minerals
3. Slowly dissolves them through chemical weathering. The component ions are then left in the water (carbon)
4. Carried in surface waters (rivers/streams) and then to the ocean
5. Settle out as minerals, in the form of calcium carbonate (CaCO2)
6. Coral extracts CaCO2 from the seawater
   7 . Dead coral sinks to the bottom of the ocean and becomes buried
7. Becomes compacted as layers of limestone
   9 . Tectonic uplift then exposes this buried limestone. E.g. Himalayas —> highest peaks are formed from material that was once as the bottom of the oceans
8. Tectonic forces causes plate movement to push the sea floor under continental margains through subduction
   11 .These deposits are then subject to convection currents
9. And rise back to the surface through volcanic eruptions
   THEN REPEATS - A REPEATED CYCLE.