Water and carbon cycles 7


Carbon stores represent a natural reservoir of carbon before it is transferred into another chemical or physical environment. It can be a source - a store in which the release of carbon occurs at a faster rtae than it is absorbed; and a sink - a store in which the absorption of carbon occurs at a faster rate than it is released.

  • Carbon sources release more carbon than they absorb.
  • Carbon sinks absorm more carbon than they release.

The size of the stores fluctuates

  • Fast carbon cycles - relatively rapid transfers of carbon compounds over years, decades and centuries, e.g. photosynthesis.
  • Slow carbon cycles - transfers of carbon compounds over extensive timescales, e.g. carbon sequestration.

Sub-cycle duration:

There are four major cycles of carbon that operate over different timescales.

  • Fast organic carbon cycle - operates from months to centuries and mainly involves the tranfers of organic carbon via living things between the atmosphere, soil and biosphere.
  • Fast non-organic carbon cycle - involves ocean-atmosphere exchange of carbon dioxide depending upon the relative conditions of both.
  • Slow organic carbon cycle - takes hundreds of millions of…


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