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Water, Carbon and Nitrogen Cycles

The Carbon Cycle.

Natural processes can release carbon dioxide into the atmosphere
(by combustion, decay and respiration)
or remove carbon dioxide from the atmosphere
(by photosynthesis and dissolving in the sea),
or "lock up" carbon in the ground as fossil fuel or carbonate rock.

Carbon dioxide in the atmosphere dissolves in rain water,
forming carbonic acid (H₂CO_3(aq)).
H₂O_(l)     + CO_2(g)        H⁺_(aq)    +      HCO₃^-_(aq)
This makes rain water naturally acidic (pH = 5.5).
This acidic rain water will react with carbonates in rocks.

Rain water finds its way into the sea (see the water cycle).
Carbon dioxide also dissolves directly into the sea. The huge oceans
are an important gas reservoir for carbon dioxide (they store it).

Chalk and limestone release carbon dioxide when they react with acid rain.
If chalk or limestone are forced down into magma and heated,
then carbon dioxide may be released from volcanoes.

The burning of fossil fuels is increasing the amount of carbon dioxide
in the atmosphere faster than nature can remove it.
Deforestation (cutting down forests) is making this worse,
as it reduces the amount of photosynthesis.

See also global warming and greenhouse gases.

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Copyright © 2008 Dr. Colin France. All Rights Reserved.