posted on Aug, 16 2008 @ 10:51 PM
Carbon dioxide (CO2) is a stable oxide of carbon. It will not normally break down in the atmosphere. Magnesium will burn in a pure CO2 atmosphere,
liberating carbon while it forms magnesium oxide, but that is a unique process.
Most carbon dioxide is either absorbed by ocean water (forming weak carbonic acid) or it is absorbed by plant life through photosynthesis. The carbon
dioxide that is absorbed is used to produce sugars (food for the plant, or for us when we eat it) and oxygen is then liberated by the process. By far,
the plant absorption accounts for most of the CO2 that is scrubbed from the atmosphere. CO2 is a bit heavier than air, so it tends to concentrate at
low levels, which, luckily enough, is where the plants are.
CO2 which is absorbed by the oceans forms a very weak acid, since it does not readily absorb into water. The soda that fizzes when you open it is
composed of 'carbonated' water, which is essentially CO2 dissolved under pressure in the water contained in the soda. The reason it fizzes is that
CO2 does not absorb easily in water, so when the pressure is released, the CO2 escapes rapidly, forming the fizz. So it is in the oceans, where
oceanic plant life thrives from dissolved CO2 in the water escaping from carbonic acid molecules.
CO2 is relatively inert, and as far as we can tell, has been present in the atmosphere since as far back as we can measure. The levels have varied
during the planet's history. Today, the average concentration is 387 parts per million (ppm) of air by volume. 'Toxic' CO2 levels begin for the
most sensitive people at 10,000 ppm. CO2 is not a poison, or a toxin, or pollution. It is a normal trace gas in the atmosphere, and is as vital for
plant life as oxygen is for us.
CO2 is produced by any oxidation of carbon. Since carbon is extremely abundant (lucky for us, because life itself is based on carbon compounds), it
oxidizes in many ways. Volcanoes spew huge amounts of CO2 when they erupt, and pockets of CO2 occasionally vent to the surface through tectonic
cracks. All animal life produces CO2 as a by-product through breathing. Additionally, any time anything organic is burned (oxidizes) it produces CO2
or occasionally, if the available oxygen is restricted, CO. CO, or carbon monoxide is an asphyxiant which tends to replace oxygen in the bloodstream
and bonds too tightly to the blood cells, rendering them useless for carrying vital oxygen to the cells. The amount of CO normally is so low that this
is not a problem; however, when enclosed in an area with no ventilation and combustion of organic material, it may tend to accumulate and cause
drowsiness, dizziness, unconsciousness, or finally death. Luckily again, CO does tend to break down fairly quickly, especially in atmospheric
conditions, into CO2. That may have been what was confusing you.