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

Figure 7.13. 
Sulfur 
dioxide oxidation 
reaction sequence in the 
atmosphere 
Sulfur trioxide – 
SO
3
 readily reacts with 
atmospheric water vapor 
to form sulfuric acid 
solution. 
SO
3
 + H
2
O → H
2
SO
4

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7. AIR POLLUTION
 129
temperatures forms other environ mental pollutants, but as a result 
of the fuel-forming organic compound transformation carbon 
dioxide is formed.
Sulfur dioxide is a colourless gas with a sharp odour. Sulfur 
dioxide at high concentrations causes severe respiratory irritation. 
Since sulfur dioxide is easily soluble in water, during the inhalation 
it sorbs in the mucous membrane of the nose and trachea, whereas 
if the sulfur dioxide is in the form of an aerosol, it enters the lungs. 
This is precisely one of the factors that determines the harmful 
London-type smog exposure, because this type of smog is formed in 
humid air and is characterized by high dust content.
When sulphur dioxide reaches the concentration of 500 mg/m
3
 
(daily average), the condition of asthma and pulmonary patients 
worsens. The cases of hospitalization are observed to increase, when 
sulfur dioxide concentrations reach 750 mg/m
3
. During the London 
smog in 1952 the annual concentration of sulfur dioxide in the air 
reached 4000 mg/m
3
.
Sulfur  dioxide  negatively  affects  plant  development.  High 
concentrations of sulfur dioxide exposure can cause leaf necrosis 
(withering),  but  chronic  exposure  results  in  typical  chlorosis  –  a 
leaf  discoloration  or  yellowing.  Sulfur  dioxide  effect  intensifies 
with increasing air humidity. Sulfur dioxide causes the inhibition 
of photosynthesis and plant respiration process, and cell membrane 
damage. The degree of plant damage depends on the nutrient and