Māris kļaviņŠ, azamat azizov, JĀnis zaļoksnis environment, pollution, development: the case of uzbekistan

 4.2.2.  Carbon cycle
Carbon is the most important element for living organisms. 
With  an  average  concentration  of  350  mg/kg,  carbon  is  not  so 
pervading on the Earth; yet, it has an exceptional role in the cycling 
of elements. In the carbon cycle (biogeochemical cycle), one carbon 
compound is converted into others, and this process occurs in the 
atmo sphere, hydrosphere, litho sphere and biosphere. In the litho-
sphere, carbon is stored in carbonate sedimentary rocks (limestone – 
CaCO
3
, dolomite – CaMg(CO
3
)
2
 and others), and it also forms fossil 
fuel sediments (coal, oil, bituminous shale). Furthermore, large 
amounts of carbon compounds (carbon dioxide and methane) 
are stored in the permafrost zone, and they also form waterbody 
sediments and the decomposition products of organic substances in 
the soil. 
In the hydrosphere, carbon compounds are present in living 
organic matter, carbonate ions and hydrogen carbonate ions in the