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

Figure 4.22. 
Natural 
processes of nitrogen 
compounds in the 
environment

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70 
ENVIRONMENT, POLLUTION, DEVELOPMENT:  THE CASE OF UZBEKISTAN
soil and waters, where they are reduced back into inert nitrogen 
gas. The amount of N
2
O  emissions  is  100 million  tons  per  year, 
and its overall amount in the atmo sphere is 2000 million tons. The 
nitrogen cycle completes in 120 years, but the concentration of N
2
O 
in the atmo sphere has been increasing by 0.3% annually within 
the last hundred of years. Hence N
2
O is considered one of the main 
greenhouse gases.
As with other key chemical elements, nitrogen cycling is graphi-
cally represented by its biogeochemical cycle (Figure 4.23).
N
2
 in the atmosphere
6
0.2
Fixation of N
2
in the atmosphere 125
Fixation of N
2
in the soil 110
Soils
Conversion of nitrogen 
compounds: denitrification 100
Fixation of N
2
 in the hydrosphere 140
Conversion of nitrogen compounds: denitrification 240
Industrial fixation of N
2
fossil fuel combustion 125
Sedimentary rocks
containing nitrogen
Runoff 20
In 1914, German chemists Fritz Haber and Carl Bosch developed 
an industrial method for the manufacture of ammonia from atmo-
spheric nitrogen, commencing the development of a large-scale 
industrial production of agricultural inorganic fertilisers. Today 
the  total  amount  of  approximately  100 million  tons  of  nitrogen 
fertiliser is produced every year, which roughly corresponds to the 
amount of nitrogen fixed by micro-organisms (100-200 million tons 
per year) (Figure 4.24). Thus, the amount of nitrogen produced by 
human activity is already comparable to the amount nitrogen fixed 
in the natural processes of the nitrogen biogeochemical cycle, and 
it is estimated that the former will exceed the latter in the near 
future.
Considering the large production amounts of nitrogen com-
pounds, they can adversely affect not only environ mental processes 
but also human and animal health.