Introduction to the carbon cycle

The element carbon is the most important out of all the elements that make up living matter. It has a simple atomic structure that can bond with other atoms of other elements to create complex molecules, which makes it the basis of all living matter. E.g., proteins, simple sugars, carbohydrates and fats, these carbon-based compounds are the building blocks of life.

Key terms:

Stores - where carbon is held, creates cycles + feedback

Fluxes - the rate of flow between stores (aka sinks, pools)

Systems - how the carbon cycle operates with inputs, outputs, stores + flows

Anthropogenic - processes + actions associated with human activity

Organic - carbon found in living organisms

Reservoir turnover - the rate at which carbon enters + leaves a store is measured by the mass of carbon in any store divided by the exchange flux

Petagrams (Pg) or Gigatonnes (Gt) - the units used to measure carbon, 1 petagram (aka 1 gigatonne) is equal to a trillion Kg, or 1 billion tonnes

Photosynthesis - how plants with chlorophyll (green plants) produce energy from carbon + water

Respiration - breathing

Decomposition - the breaking down of organic matter, resulting in the release of carbon

Combustion - burning oxygen

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The carbon cycle is a natural cycle that moves carbon between land, oceans and the atmosphere. This movement involves a number of chemical reactions that create new stores which trap carbon for significant periods of time. There tends to be a natural balance between carbon production and absorption within this cycle. However, there can be occasional disruptions and short periods before the equilibrium is restored, such as when large volcanic eruptions emit large quantities of carbon into the atmosphere or when natural climate change occurs.

The 2 main components of the carbon cycle:

The (slow) geological carbon cycle

• carbon stored in rocks and sediment

The (fast) biological (bio-geological) carbon cycle

• carbon stored within vegetation, soils, and the atmosphere

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If the sources equal the sink, the carbon cycle is balanced or in equilibrium, with no change in the size of stores. Humans have altered the stores and fluxes in various ways (anthropogenic factors).

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→ STORES: terrestrial (land), oceanic (oceans + seas), atmospheric (the air around us)

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%%Biosphere%%:

• living organisms, trees, and plants (uses photosynthesis)

• also stored in aquatic environments and animals

• stores 0.0012% of carbon

• concentrated geographically in forests (not evenly distributed)

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^^Atmosphere^^:

• stores 0.0017% of carbon
• mostly found as carbon dioxide and methane
• increasing amounts due to climate change

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%%Pedosphere%%:

• made of peat (dead organic matter)
• layers of peat conserve carbon in the ground
• stores 0.0031% of carbon

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==Fossil fuels==:

• stores 0.004% of carbon

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^^Hydrosphere^^:

• stores 0.038% of carbon

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@@Lithosphere@@:

• stores over 99.99% of carbon
• e.g., limestones

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