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

particular amount of water currently happens to be. For example, 
the spring water is underground water, but coming to the surface, it 
becomes surface water. The river water also changes its composition 
and properties when falling into the seas or oceans, but the ocean 
mist is often salty to taste, and its properties are different from the 
fog, for example, in tropical forests after the rain.
Water features and content may change not only due to pollution 
but also to cleaning. In nature, water has a self-cleaning ability and 
it is an essential condition, because of which the water can be called 
a renewable resource. 
The existing water treatment technologies allow purifying the 
water, rendering it usable for a particular sphere of its use. Depend-
ing on the type of contamination, it can be categorized into the 
chemical, physical and biological contamination.
Two types of water pollution sources can be distinguished: 
1)  point sources of pollution;
2)  diffuse pollution sources. 
Typical water pollution point sources are: 
1)  pipes through which either treated or untreated sewage water 
of the cities or factories is discharged into water reservoirs, 
rivers, lakes and seas;
2)  agricultural effluents;
3)  oil and petroleum product spill from pipelines.
Diffuse pollution sources are scattered and it is more difficult to 
identify and assess them. The main diffuse sources of pollution are:
1)  surface  runoff  from  agricultural  lands,  construction  areas, 
burned forests;
2)  surface  runoff  from  agricultural  lands,  which  are  conta mi-
nated with chemical fertilizers, natural fertilizers (biogenic 
element runoff), pesticides or saline waters;
3)  rainwater runoff from urbanized areas;
4)  drainage from abandoned or operational mines, quarries; 
5) fall of substances with precipitation (sulfur, nitrogen and 
metal compounds, organochlorine compounds);
6)  leaks from dumping-grounds and landfills into underground 
and surface waters.
Chemical pollution 
is caused by entry or 
presence of chemicals in 
the waters and, depen‑
ding on the pollutant 
characteristics, one can 
distinguish between 
the contamination with 
inorganic substances 
(biogenic elements, 
inorganic salts, toxic trace 
elements, radionuclides) 
and organic substances 
(biologically readily 
degradable substances, 
oil products, pesticides, 
surfactants and other 
substances). Physical 
pollution is caused by 
physical effects such as 
the influence of tempe‑
rature on the water, but 
biological contamination 
is created by the entry of 
living organisms atypical 
to the particular type of 
water, such as viruses, 
bacteria.

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8. WATER POLLUTION
 161
Diffuse water pollution is generally more dangerous than point 
source pollution. For example, the major part of nitrogen and almost 
half the amount of phosphorus compounds contamination in the 
Baltic Sea is caused by the diffuse pollution (Figure 8.2).
Industry
3%
Non-point
sources
71% 
Non-point
sources
44% 
Wastewaters
26%