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

Figure 5.16. 
Emission 
amounts of nitrogen 
oxides and ammonia 
and their changes in 
the European Union 
Member States

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5. GLOBAL ENVIRONMENTAL PROBLEMS
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Motor traffic is considered one of the major sources of nitrogen 
oxides which directly affect the air quality in cities (Figure 5.17).
 Nitrogen (N
2
)
Nitrogen oxide (NO)
Combustion
Nitrogen oxide (NO)
and
Acid rain
Oxygen atom (O)
Nitrogen oxide (NO)
and
Various pollutants
Hydrocarbons
Oxygen (O
2
)
Oxygen (O
2
)
Oxygen (O
2
)
Ozone (O
3
)
Nitrogen dioxide (NO
2
)
UV rays
Water vapour
(H
2
O)
Peroxyacyl nitrates
Nitric acid (HNO
3
)
Volatile
hydrocarbons
 5.3.3.  Dust and aerosols 
Atmo spheric air contains particles of every sort, size and com-
po sition. Their sizes may vary from micron to millimetric parts. The 
finer particles (size <10 µm) are called aerosols, whereas the coarser 
are called dust. Liquid micro-droplets (haze) are also counted 
as aerosols. The main sources of dust and aerosol for ma tion are 
various natural processes – soil and its constituent mi ne ral particles 
entering  the  atmo sphere  with  wind,  dust  storms  (Figure 5.18), 
volcanic  eruptions,  forest  fires,  and  evaporation  from  the  sea  and 
ocean surfaces (forming sea salt aerosols). Admittedly, to day human 
activity causes the discharge of many aerosols and dust into the 
air. The main anthropogenic sources are such processes as the 
generation of energy, the production of building materials, mining, 
agriculture, air transport and others.
Figure 5.17. 
Role of 
nitrogen oxides emitted 
with motor vehicle 
engine exhaust in the 
reactions of formation 
of smog, acid rain and 
ozone

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ENVIRONMENT, POLLUTION, DEVELOPMENT:  THE CASE OF UZBEKISTAN
Aerosols can be formed and the composition of particles in the 
air can vary as a consequence of different chemical reactions. Sulphur 
and nitrogen oxides play a considerable role in these processes. 
Since the airborne solid particles form the condensation centres for 
water vapour, all these reactions take place in the atmo sphere in the 
presence of water. Acid rain formation is a typical example.
As aerosols and dust particles have a relatively large surface, they 
can sorb atmo spheric gases, chemicals, micro-organisms and water 
vapour, and this sorption process determines the rather complex 
composition of aerosols.
Atmo spheric aerosols and dust can significantly affect the Earth’s 
climate, as evidenced by long-term climate change analysis and the 
increasing effect of dust from volcanic eruptions on the climate.
An important group of aerosols are those of organic composition. 
Their  source  can  be  both  natural  processes  (plants,  forest  fires, 
organic matter decay) and anthropogenic processes. The presence 
of metal compounds (Pb, Hg, Cu, Ni, Be), radioactive isotopes and 
organic substances in the composition of aerosols can particularly 
adversely  affect  the  human  health.  The  exposure  to  aerosols  is 
most hazardous in case of inhaling such particles that are retained 
in the lungs (coarser dust particles are captured in the nasal cavity 
and  upper  airways,  whereas  finer  particles  can  be  exhaled).  The 
aerosols containing such particles are called respirable aerosols. 
Their particle sizes are often smaller than 2.5 µm. These aerosols 
are designated PM
2.5
 (PM stands for Particulate Matter). The effects 
of these aerosols can be as follows:
1)  the substances adsorbed on the surfaces of aerosol particles may 
desorb and enter the circulatory and lymphatic systems. Such 
Figure 5.18. 
Sand storm 
in the Sahara

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5. GLOBAL ENVIRONMENTAL PROBLEMS
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an effect is typical of various combustion products. Combustion 
product aerosols contain carbon, and on the surface of these 
aerosols, usually there is quite a high concentration of different 
organic substances originated from incomplete combustion or 
in the process of thermosynthesis;
2)  ultrafine particles, such as asbestos fibres, can penetrate the 
blood or lymphatic system from the lungs; 
3) aerosol particles can remain in the lungs and calcify, 
causing  constant  irritation.  The  aerosol  effect  of  this  type  is 
characteristic of occupational diseases – asbestosis and silicosis, 
caused by inhaling the air polluted with mineral particles;
4)  micro-organisms, bacteria or fungi residing on the aerosol and 
dust particles may cause allergic reactions as well as illness.
The dust of pollen, wood, flour and other organic substances can 
be considered a special group of aerosols. Since these substances are 
organic, their composition differs significantly from the traditional 
dust composition; yet, these aerosols can cause allergies.
Since  the  effects  of  aerosols  on  humans,  animals,  plants 
and buildings can be detrimental, and aerosols and dust can 
be considered, by their mass, the largest group of atmo spheric 
pollutants, it is crucial to limit their emission in the main sectors 
responsible for this kind of pollution, namely the production and 
energy industry.