The Carbon Cycle

Processes by which carbon is transferred from one store to another

Carbon is present in both organic and inorganic forms

--> organic carbon found in the biomass of living organisms

--> inorganic carbon is found in the atmosphere and the ocean

Carbon stores (pools or sinks) = ocean, fossil fuels, living organism

Carbon moves between four pools: biosphere, hydrosphere, atmosphere and sediments by fluxes

Carbon transfer (fluxes) = dissolving, combustion or photosynthesis

• Diffusion: CO2 diffuses from the atmosphere or water into autotrophs

• Photosynthesis: autotrophs convert CO2 from the atmosphere into carbohydrates and other organic compounds

• Respiration: CO2 is produced as a waster product and diffuses out into the atmosphere or water

• Decay: dead organic matter is decomposed to CO2, water, ammonia and mineral ions by micro-organisms

• Peat: forms when plant matter doesn't fully decompose due to acidic and anaerobic conditions. Slowly releases carbon when exposed to oxygen/burned

• Combustion: releasing of carbon dioxide by burning fossil fuels and organic material

• Feeding: gaining carbon compounds from other organisms

Biomass, peat, coal, oil and natural gas form big carbon sinks

--> when these carbon supplies burn as a fuel in complete combustion carbon dioxide and water is released

Oil and gas are formed over a large period of time and originate from dead marine organisms containing calcium carbonate

When buried under the sediment layer heat and compression acts on transforming these organism in oil and gas

--> stored away in pockets of rocks or sand

Coal has been formed from plant material

Peat is the first stage in coal formation

--> consists of incompletely decomposed organic matter

Decaying plant material, usually in wet areas, is prevented from decaying fully by acidic and anerobic conditions

When sediments accumulate over partially decomposed peat, coal is formed by further transformation through weight and pressure

Majority of carbon dioxide emission from combustion originates from the burning of fossil fuels by humans

If photosynthesis exceeds respiration, there is a net uptake

--> ecosystem acting as a carbon sink

If respiration exceeds respiration, there is a net release

--> ecosystem acting as a carbon source

The rate of these two processes are not necessarily equal

Constructing carbon cycle diagrams

• Should be drawn using boxes and arrows

• Storages = boxes

• Fluxes = arrows