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

Table 7.2. 
Annual average concentration of air pollutants, µg/m
3
 
City
SO
2
NO
2
Dust
The most common indicators in European cities
20-50
40-60
60-70
European guiding value
40-60
30
40-60
Riga
10-30
45-75
100-200
Of other sulfur compounds whose presence in the air can 
adversely affect its quality, hydrogen sulfide H
2
S should be noted. 
As a result of natural processes rather large quantities of hydrogen 
sulfide  are  released  in  the  environ ment.  The  main  sources  of  its 
natural emission are volcanic gases and decomposition of living 
organisms. High hydrogen sulfide content is observed in natural gas 
(up to 15%, Leke – France, Astrakhan – Russia). In small quantities it 
escapes into the atmo sphere as a result of processes that take place 
An effective solution 
to reduce sulfur oxide 
emissions is fuel 
combustion process 
optimization, such as 
using the fluidized bed 
method. In this case, coal 
and limestone particles 
crushed to certain sizes 
with adjustable air flow 
are maintained at the 
level of fluidized bed and 
already in the process of 
burning sulfur dioxide 
is fixed, and gypsum 
is formed as the end 
product of the process.
CaCO
3
 → CaO + CO
2
 
2CaO +2 SO
2
 + O
2
 → 2 
CaSO
4
 
CaO + SO
2
 → CaSO
3
 

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ENVIRONMENT, POLLUTION, DEVELOPMENT:  THE CASE OF UZBEKISTAN
in continental shelves, marshes and elsewhere due to decomposition 
of  organic  matter.  Hydrogen  sulfide  concentration  in  the  air  on 
average equals 6 µg/m
3
.
In industry, hydrogen sulfide is incorporated into the composi-
tion of coke gases and water gas, and as an admixture it may be 
generated  in  oil  refining,  as  well  as  the  manufacturing  processes 
of  artificial  silk,  cellulose,  rubber  and  dyes.  Hydrogen  sulfide  and 
organosulfur compounds are released by purification devices.
Hydrogen sulfide is an unstable compound that readily oxidizes, 
reacts with metals. Depending on the oxidizer, the oxidation 
processes lead to sulfur or sulfur oxides. Hydrogen sulfide is easily 
soluble in water. The toxic effect of hydrogen sulfide is determined by 
its ability to block the enzyme activity by binding to the constituent 
metal ions in stable sulfides. Hydrogen sulfide sensing threshold is 
0.075 to 0.1 mg/m
3
, and contact with it numbs the sensory organs 
rather  quickly.  In  practice,  the  poisoning  of  hydrogen  sulfide  can 
take place as a result of contact with sewage systems, as well as in 
chemical laboratories and enterprises. Thus, the key issue to protect 
people from exposure is proper ventilation and, if necessary, airing 
in the rooms where hydrogen sulfide may accumulate.