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What are the stores of carbon?
- Atmospheric: CO2 in air
- Terrestrial: Biomass, soils, mantle
- Oceanic: Dissolved carbon in water, sedimentary rocks, calcium carbonate shells
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What are fluxes?
Flows of carbon between stores
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Define the carbon cycle.
The exchange of carbon between the atmosphere, terrestrial biosphere, oceans and sediments.
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How is carbon measured?
- In petagrams
- 1 Pg = billion tonnes of carbon
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In what forms can carbon be found?
- Inorganic: in rocks as bicarbonates + carbonate
- Organic: in plant material
- Gaseous: as CO2, CH4 and CO
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Define carbon sequestration.
The removal + long-term storage of carbon from the atmosphere.
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What occurs in the geological cycle?
- 1) Terrrestrial carbon in mantle is released into atmosphere when volcanoes erupt, called outgassing
- 2) Atmospheric CO2 + rainfall -> carbonic acid. Acid rain dissolves rocks, which releases bicarbonates, called chemical weathering
- 3) Rivers transport carbon + calcium to oceans
- 4) Organic carbon from plants/shells/skeletons sinks to ocean bed + builds up
- 5) Carbon rocks are subducted along plate boundaries, emerging during eruptions
- 6) Intense heating along plate boundaries metamorphoses sedimentary rocks, forming metamorphic rocks and CO2 is released
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Describe the biogeochemical cycle.
- 1) PS by phytoplankton takes in CO2 from atmosphere
- 3) Respiration by organisms releases CO2 + water into atmosphere
- 4) Decomposition of dead organisms releases CO2 into soil + sea floor
- 5) Combustion of FFs releases CO2 into atmosphere
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Define biological carbon pump.
Process by which living organisms transfer carbon from atmospheric store to the ocean floor sediment store
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Describe the steps of the biological pump.
- CO2 from atmosphere dissolves in water (oceans hold 50x more carbon than atmosphere)
- Phytoplankton (microscopic organisms) photosynthesise and sequester this carbon and some CO2 is released by respiration (they sequester 2bn tonnes of carbon from atmophere to ocean)
- When eaten by zooplankton/larger organisms, carbon is passed through food chain
- Organisms turn carbon into calcium carbonate outer shells and inner skeletons
- They die and sink to sea floor
- Sedimentation/lithification occurs and they form limestone sediments as a carbon store
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What is the fast carbon cycle?
Terrestriaal part where plants sequester CO2 via PS and release it via respiration/decomposition (100-120Gt/yr)
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What is the slow carbon cycle?
- Ocean part where carbon is in dissolved form + ocean organisms, and held in sediment on ocean floor for a long time
- Long-held stores in earth's surface are moved when volcanic eruptions occur
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Effect of deforestation on atmospheric carbon stores in a particular area?
Increased as less carbon sequestration via PS
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Role of oceans in the carbon cycle?
- Ocean acts as carbon sink
- Seesters carbon via phytoplankton through PS, lowering atmospheric carbon
- Biological carbon pump
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Processes that release CO2:
- Respiration
- Combustion
- Decomposition/decay
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Process that remove CO2 from atmosphere:
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Organism that are decomposers:
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Why can’t plants grow without decomposers?
- Decomposers cause decay of dead plants/animals
- Releases carbon and nitrogen into soil to be taken by plants
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Combustion equation:
Hydrocarbon fuel + oxygen = carbon dioxide/sulfur dioxide + water
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Methods of testing for the presence of CO2:
- Limewater - turns cloud
- Bicarbonate indicator - yellow if above atmospheric CO2 level, orange if equal, purple if below
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Equation for PS:
Carbon dioxide + water -> oxygen + glucose + energy
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Equation for respiration:
Oxygen + glucose -> carbon dioxide + water + energy
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Carbon compounds found within plants + animals
- Cellulose
- Starch
- Glycogen
- Glucose
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Rock that traps carbon from dead plants/animals + product formed within these rocks of millions of years
Sedimentary rocks + fossil fuels
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What is the thermohaline circulation?
- Ocean current that produces vertical/horizontal circulation of cold + warm water around the world’s oceans. In addition to this, the
- atmospheric circulation creates large currents in the oceans which transfers water from the
- warmer tropical areas of the world to the colder polar regions.
- Cold currents upwell nutrients and ocean mixing removes zooplankton, so phytoplankton thrive
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What natural methods can be implemented to sequester carbon?
- Peat bogs
- Afforestation
- Wetland restoration (15% of world's soil carbon is in wetlands)
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