Cabon Cycle EQ1

Question 1

Sequestering

Answer 1

• The natural storage of carbon by physical or biological processes such as photosynthesis

Question 2

Origins of the carbon cycle

Answer 2

• When primitive bacteria started photosynthesising 3 billion years ago, they added oxygen to the atmosphere and absorbed C02 from it. The higher oxygen levels that resulted allowed more complex organisms to develop about 2 billion years ago
• CO2 was dissolved in the early oceans and then stored in sedimentary rocks
• The balance in the carbon cycle has been altered by human activity such as deforestation, burning of fossil fuels and release of stored carbon

Question 3

Carbon cycle is a closed system:

Answer 3

It does not have any external inputs or outputs, so the total amount of carbon is constant and finite

Question 4

Carbon stores

Answer 4

Reservoirs/pools/stocks where carbon is held

Question 5

Carbon fluxes

Answer 5

The movement or transfer of carbon between stores

Question 6

Carbon processes

Answer 6

The physical mechanisms that the drive the fluxes between stores

Question 7

What are the 4 carbon stores

Answer 7

• The atmosphere: gases such as carbon dioxide and methane
• The hydrosphere: oceans and lakes, where there is dissolved carbon dioxide
• The lithosphere: carbonates in limestones and fossil fuels
• The biosphere: living and dead organisms

Question 8

The geology carbon cycle (slow cycle)

Answer 8

• This is a natural cycle that moves carbon between land, ocean and atmosphere. This movement involves a number of chemical reactions that create new stores which trap carbon for significant periods of time

1) terrestrial carbon within the mantle is release into the atmosphere during an eruption
2) it combines with rainfall to produce acid rain which dissolved carbon rich rocks
3) rivers transport weathered material to oceans where it is deposited
4) carbon in organic matter from plants and animals sinks to the bottom of ocean beds when they die building stars of coal, chalk and limestone

Question 9

The biochemical carbon cycle (fast cycle)

Answer 9

• The biological and chemical processes determine just how much of the carbon available on the Earth’s surface is stored or released at any time

There are 4 key processes in this cycle:
- photosynthesis
- respiration
- decomposition
- combustion

Question 10

Maintains an equilibrium

Answer 10

• Volcanic emissions send extra CO2 into the atmosphere, which leads to rising temperatures increased evaporation and higher levels of atmospheric moisture
• This leads to acid rain, with weathers rocks and creates biocarbonates which end up on the bottom of ocean floors
• This slowly rebalances the carbon cycle

Question 11

How do geological processes release carbon into the atmosphere

Answer 11

• Weathering: rainwater dissolves carbon rich rocks, which then causes these biocarbonates to be deposited in nearby ocean floors. Tectonic forces may bring these sedimentary rocks into contact with extreme heat, causing the release of this carbon dioxide back into the atmosphere
• Volcanic outgassing: pockets of CO2 exist in the Earth’s crust. Disturbance by volcanic eruptions or earthquakes may allow pulses or more diffuse fluxes into the atmosphere

Question 12

Ocean sequestration

Answer 12

• The ocean is one of Earth’s largest carbon stores. Small changes in oceanic carbon cycling can have significant global impacts

Question 13

Carbon cycle pumps

Answer 13

• Biological pump
• Carbonate pump
• Physical pump

These pumps flux surface ocean CO2 to the deep ocean

Question 14

Biological pump

Answer 14

• This is the organic sequestration of CO2 to oceans by phytoplankton. They float near the surface to access sunlight to photosynthesis
• Carbon is then passed up the food chain by consumer fish, which in turn release the carbon back into the water and atmosphere
• Most is recycles in surface waters

Question 15

Carbonate pump

Answer 15

• Marine organisms may use calcium carbonate to make hard outer shells and inner skeletons
• When they die and sink, many shells dissolve before reaching sea floor sediments. This carbon become part of deep ocean currents
• The shells that do not dissolve build up slowly on the sea floor

Question 16

Physical pump

Answer 16

• CO2 in the oceans is mixed much slower than in the atmosphere, meaning there are large spatial differences in CO2 concentrations
• The colder the water, the more potential for CO2 absorption. Polar oceans store more carbon that tropical oceans
• Warm tropical oceans release CO2, whereas colder high-latitude waters absorb it. More than twice as much CO2 can dissolve in polar waters than in warm equatorial waters

Question 17

Terrestrial primary producers

Answer 17

• They sequester carbon through the process of photosynthesis, just as phytoplankton does in the ocean
• Green plants are primary producers. CO2 is absorbed and converted into plant growth during photosynthesis. As plants grow, they release CO2 into atmosphere through respiration. 95% of a trees biomass is made up of CO2
• Carbon fixation turns gaseous carbon into organic compounds that grow

Question 18

Terrestrial primary consumers

Answer 18

• Organisms known as primary consumers depend on and feed on producers, and return carbon back to the atmosphere through respiration

Question 19

The role of soil in the carbon cycle

Answer 19

• Soil stores 20-30% of global carbon, sequestering about twice the quantity as the atmposhere
• Whether it sequesters or emits CO2 depends on local conditions
• Organic sources are the main cause of carbon in soil. Plant photosynthesis and subsequent decomposition as well as living organisms input carbon into soils. Living organisms represent about 5% of total soil organic matter
• Decomposition is fastest in warmer climates with high rainfall, temperatures and oxygen levels; it is very slow in cold, dry climates with a lack of oxygen

Question 20

Factors that affect the capacity of soil to store carbon

Answer 20

• Climate: warmer, wetter, oxygen rich climates yield the highest decomposition levels
• Soil type: clay rich soils have higher carbon content than sandy soils
• Management and use of soil: since 1850, 40-90 billion tonnes of carbon have been lost to cultivation and disturbance
• Tundra soils: much of the carbon in the tundra region is permanently frozen and contains ancient carbon. The majority of time roots and dead organic matter is frozen, locking any carbon in an icy store

Question 21

Natural greenhouse effect

Answer 21

• Energy is received from the sun as short-wave radiation. Dark surfaces absorb this and then radiate or back as heat which is long-wave
• Greenhouse gases absorb and reflect some of the radiated heat from the earth’s surface. Some long-wave radiation is passed back into space

Question 22

Enhanced greenhouse effect

Answer 22

• Human activities such as deforestation and release of natural carbon stores combine with oxygen to create greenhouse gases
  -This results in a thicker layer of greenhouse gases which trap more heat. Furthermore, the increased temperature causes greater evaporation and in turn more cloud covers which further traps more heat

Question 23

Regulating the composition of the atmosphere

Answer 23

Photosynthesis is a vital process in regulating the composition of the atmosphere:

• Phytoplankton in the ocean sequesters CO2 in the action of the biological pump
• Terrestrial photosynthesis enables plants to sequester and release carbon through respiration and decomposition