This article provides an essay on the carbon cycle.
The carbon cycle is very complex due to the fact that carbon can exist in a wide variety of different types of compounds, occupying in plants, animals, rocks, liquid, sediments and air.
The most important carbonaceous materials are CO2, CO, carbonates, and organic carbonaceous materials. In the atmosphere 0.03 per cent CO2 gas is present. Major amount of carbon materials lie as dissolved CO2 in fresh water and saline water.
They form carbonate or bicarbonate and thereby make deposition as sediment or crustal deposits like limestone and marble stone. However a major amount of CO2 is fixed as organic carbon by the green plants through photosynthesis in both terrestrial and aquatic ecosystem.
A portion of them are deposited as fossil fuel like coal and oil. On the other hand, CO2 is liberated back to atmosphere from burning of fuel, respiration of biota, volcanoes, and decomposition of organic waste. An overall scheme of carbon cycle is given in Fig. 5.17.
In some situations, CO2 cycle is very rapid as in plants which fix CO2 within an hour by photosynthesis, and are also capable of releasing the same by respiration in same rapidly.
But non-biological processes or complex biological and abiotic processes leading to carbonate rock formation, or fossil organic fuel deposit creation requires millions of years. In modern times, human activities are making a significant impact on the global carbon cycle.
When fossil fuels are burned, geological reserves of carbon are converted into CO2 and released into the atmosphere. Today the release of CO2 or discharge of CO2 into the atmosphere is steadily increased, owing both to the burning of fossil fuels and to the destruction of forests. A simplified model of carbon flow in the environment is given in Fig. 5.18.
As a consequence of global CO2 rise over the years, green effects were noticed particularly during past couple of decades, as such rise of global warming problem takes place. An overview of global warming problem arising out of CO2 cycle disturbances is depicted in Fig. 5.19.