What are the stores of carbon?
- Atmospheric: CO2 in air
- Terrestrial: Biomass, soils, mantle
- Oceanic: Dissolved carbon in water, sedimentary rocks, calcium carbonate shells
What are fluxes?
Flows of carbon between stores
Define the carbon cycle.
The exchange of carbon between the atmosphere, terrestrial biosphere, oceans and sediments.
How is carbon measured?
- In petagrams
- 1 Pg = billion tonnes of carbon
In what forms can carbon be found?
- Inorganic: in rocks as bicarbonates + carbonate
- Organic: in plant material
- Gaseous: as CO2, CH4 and CO
Define carbon sequestration.
The removal + long-term storage of carbon from the atmosphere.
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
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
Define biological carbon pump.
Process by which living organisms transfer carbon from atmospheric store to the ocean floor sediment store
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
What is the fast carbon cycle?
Terrestriaal part where plants sequester CO2 via PS and release it via respiration/decomposition (100-120Gt/yr)
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
Effect of deforestation on atmospheric carbon stores in a particular area?
Increased as less carbon sequestration via PS
Role of oceans in the carbon cycle?
- Ocean acts as carbon sink
- Seesters carbon via phytoplankton through PS, lowering atmospheric carbon
- Biological carbon pump
Processes that release CO2:
Process that remove CO2 from atmosphere:
Organism that are decomposers:
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
Hydrocarbon fuel + oxygen = carbon dioxide/sulfur dioxide + water
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
Equation for PS:
Carbon dioxide + water -> oxygen + glucose + energy
Equation for respiration:
Oxygen + glucose -> carbon dioxide + water + energy
Carbon compounds found within plants + animals
Rock that traps carbon from dead plants/animals + product formed within these rocks of millions of years
Sedimentary rocks + fossil fuels
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
What natural methods can be implemented to sequester carbon?
- Peat bogs
- Wetland restoration (15% of world's soil carbon is in wetlands)