Question

The major reservoir of carbon on earth is ……….

Answer 1

The amount of carbon present in the atmosphere is very small. Most of the carbon in the atmosphere is present in the form of carbon dioxide. The main sources of carbon are ocean, biosphere and soil.

Complete answer:
The size for any reservoir of carbon is given as its mass units. The total amount of carbon present in the whole world is 65,500 GtC (Giga-tonnes of carbon). The largest (major) reservoir of carbon on earth is the deep oceans. The amount of carbon present in the ocean is about 37,000 GtC, whereas in the atmosphere, it is about 750 GtC and in the biosphere, it is 610 GtC.
Carbon moves between these reservoirs through the carbon cycle having different components (both slow and fast). In the slow component, the carbon has the ability to move in the cycle by producing complex chemical reactions. In the fast cycle, carbon has the ability to move through different forms of life on the earth. Even the annual flux in the fast cycles is about 1000 times more than in the slow cycles.

Additional information: Many microorganisms have also been discovered that play an important role in mineralizing organic compounds present on the earth, thus increasing the overall turnover of the carbon. Microorganisms present in the oceans have the capability to metabolise many types of substances for their survival.

Note: The sizes of reservoirs and their fluxes vary a lot between different sources and this property is known as reactivity. Small reservoirs are more reactive than the larger ones because they have relatively high fluxes as compared to the total size.