Concept of the carbon cycle

The Carbon Cycle

1.-Carbon enters the atmosphere as carbon dioxide from respiration (breathing) and combustion (burning).

2-Carbon dioxide is absorbed by producers (life forms that make their own food e.g. plants) to make carbohydrates in photosynthesis. These producers then put off oxygen.

3. - Animals feed on the plants. Thus passing the carbon compounds along the food chain. Most of the carbon these animals consume however is exhaled as carbon dioxide. This is through the process of respiration. The animals and plants then eventually die.

4.-The dead organisms (dead animals and plants) are eaten by decomposers in the ground. The carbon that was in their bodies is then returned to the atmosphere as carbon dioxide. In some circumstances the process of decomposition is prevented. The decomposed plants and animals may then be available as fossil fuel in the future for combustion.

Symbolic representation of the main chemical reactions carried out in this cycle.

CO2 + H2O + energy «(carbohydrate) CH2O + O2»

CO2 + CO3 2 - (carbonate) + H2O «»

2HCO3 (bicarbonate)

CO2 + H2O «H2CO3 (carbonic acid)

(Ca, Mg)SiO3 (silicate rock) + 2CO2 + 3H2O ® (Ca, Mg) 2 + 2HCO3 - (bicarbonate) + if (OH) 4

How has increased the concentration of CO2 in the atmosphere and what has caused.

Naturally, the atmosphere is composed in a 78.1% of nitrogen, a 20.9% oxygen, and the remaining 1% by other gases, including argon, helium, and some greenhouse gases, as the carbon dioxide (0.035%), methane (0.00015%), nitrous oxide (0.0000016%) and water vapor (0.7%).

Derived from human activity, a lot of gases have been emitted into the atmosphere, which has slightly changed the composition of the same. As an example we can mention the concentration of various greenhouse gases has increased.

In the last three hundred years the amount of carbon dioxide increased from 280 to 368 milligrams per cubic meter (mg/m3 or parts per million); of methane, from 0.7 to 1.75 mg/m3; and that of nitrous oxide, from 0.27 to 0.316 mg/m3. This means that, by volume, carbon dioxide is now 0.046% of the atmosphere rather than 0.035%; methane is now the 0.00037% rather than the 0.00015%, and nitrous oxide is the 0.00000187% instead of the 0.0000016%.

Although these concentrations are very small compared to oxygen or nitrogen, the change in them is actually affected the planet.

Effects of such an increase.

The persistent effect of contamination of the air breathed in a silent process of years, ultimately leads to the development of

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