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

Figure 8.11. 
Discharge 
of untreated 
wastewaters is a 
common source of river 
water pollution
Aerobic environment – 
an environment where 
the oxygen content 
is sufficient to sustain 
the life processes of 
oxygen‑consuming 
organisms. Anaerobic 
environment – oxygen‑
free environment. 

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178 
ENVIRONMENT, POLLUTION, DEVELOPMENT:  THE CASE OF UZBEKISTAN
large number of microorganisms and a multiplicity of forms can 
be observed, which depend both on the chemical composition 
of the waste water and on the quantity of organic particles 
suspended therein.
3. Regeneration zone. Here from the active disintegration zone 
the minerals – nitrate ions, phosphate ions and various micro-
elements – are borne, which are liberated in the decomposition 
process of organic substances. Since the active decomposition 
of organic substances no longer takes place here, the water is 
slowly recovering the oxygen content, and turbidity decreases. 
This creates ideal conditions for the development of algae and 
aquatic plants. As a result, the algae proliferate abundantly here.
4. Purified  zone.  In  this  zone  the  condition  of  river  ecosystem 
approaches the initial one. Nutrients have been assimilated by 
aquatic plants. As a result of photosynthesis the oxygen levels 
in the water have returned to normal. Therefore, the fish and 
invertebrates characteristic of clean water again appear in the 
river. However, it should be emphasized that in case of major 
pollution with organic substances the biological self-cleaning 
never achieves the original condition of the river ecosystem. 
Thus, the river self-cleaning process includes logical, sequential 
changes of many essential indicators. The river self-cleaning process 
described above is portrayed schematically. In a real situation, 
its pace is dependent both on the type of waste water and on the 
velocity of its current.
Pollution of natural waters with oil is particularly dangerous. 
Like other aquatic environ ment pollutants, oil is a complex mixture 
of various substances, which, depending on the oil extraction source, 
consists of linear hydrocarbons (C
6
–C
25
  paraffins),  cycloalkanes, 
aromatic hydrocarbons (mono and polycyclic) and also contains 
aromatic carboxylic acids, organo-sulfur compounds and other 
hydrocarbons.
This form of pollution is characterized by leakage of a large 
mass of oil into the marine waters and contamination of vast 
territories. Upon entry of oil and its products into the aquatic 
environ ment, it quickly spreads along the surface of the water, 
creating a surface film, for example, 15 tons of mazout leaking for 
6-7  days  can  cover  about  20 km
2
 of water surface. This condition 
involves one of the major hazards characteristic to environ mental 
pollution by oil, namely, it disrupts the air exchange between the 
atmo sphere and water, which in turn can lead to fish suffocation and 
other consequences. Waterfowl landing in the contaminated water, 
become covered in sticky oil.
Another feature of such a surface film is that many other pollutants 
are concentrated therein, primarily organochlorine compounds. For 
Oil can get into the 
aquatic environment:
 
Œ as a result of various 
accidents;
 
Œ by rainwater runoff 
leaching from 
urbanized or industrial 
areas. 
According to the ways 
of contamination listed 
above, the water protec‑
tion measures must be 
undertaken.
Marine waters can 
become contaminated: 
 
Œ as a result of tanker 
accident;
 
Œ with wash and rinse 
water of tanker ships;
 
Œ from oil rigs in the sea.