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

Table 7.3. 
Nitrogen (I) oxide sources in the environment
Emission sources
Tg N
2
O-N/per year
Natural sources
Oceans
1.4-2.6
Tropical soils
2.7-5.7
Temperate climate sources
0.05-2.0
Anthropogenic sources
Use of fertilizer
0.03-3.0
Biomass incineration
0.2-1.0
Combustion of fuels
0.3-0.9
Production
0.5-0.9
From the point of view of environ mental pollution, special 
attention should be given to nitrogen (II) oxide NO and nitrogen (IV) 
oxide NO
2
.
The reaction time depends on the temperature, respectively, the 
amount of energy input. 
At 2000 °C temperature NO, N
2
 and O
2
 molecule cross-reaction 
is at equilibrium. The intensity of NO formation is also affected by 
how quickly the formed molecule is removed from the reaction zone. 
Thus, the nitrogen oxides are formed in all processes that occur at 
high temperatures: burning, spark discharge, plasma processes, and 
explosions.
Nitrogen oxides are formed by working car engines (Figure 7.17). 
Fuel-air mixture in the cylinder of the car engine is compressed 
(compression), an electric spark ignites it, and the combustion 
(explosion) leads to a high temperature (>1000 °C), where as a by-
process a reaction occurs between the air forming gases – nitrogen 
and oxygen to form NO. After fuel combustion in the cylinder, the 
produced gas mixture is pushed out of the cylinder and it cools down 
relatively quickly, retaining the formed NO quantity.
Pr
essur
e
c
b
d
a
a’
Volume
ab
da’
aa’
bc and cd
Nitrogen oxide (II) NO is a 
colourless gas, odourless, 
non‑flammable. However, 
in the air it easily oxidizes 
to NO
2
 and therefore 
the sum of both oxides 
NO
x
 is usually looked 
at. Nitrogen (II), as well 
as nitrogen (IV) oxide is 
highly toxic. Nitrogen (II) 
oxide is mainly formed 
due to a variety of high 
temperature processes, 
as a reaction of oxygen 
with nitrogen.
N
2
 + O
2
 → 2NO 
N
2
 + 2O
2
 → 2NO
2