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

Figure 8.12. 
Oil 
spills from ships is a 
significant pollution 
source

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8. WATER POLLUTION
 179
example, the pesticide dieldrin concentration factor in such surface 
film increases up to 10 000 times. In addition, such a surface layer can 
accumulate heavy metals, particularly mercury compounds. 
After entry of oil and its products into the environ ment, further 
transformation processes take place. First of all, the volatile oil 
fractions  (benzene,  xylene,  octane,  lower  paraffins  and  cyclo-
paraffins) evaporate.
Further transformations take place through a variety of micro-
organisms. Since the oil composition is very complex, its bio destruc-
tion takes place under the influence of several groups of organisms, 
each of which has its own specifics. Primary degradation processes 
result in a new group of compounds, which themselves may not 
be less toxic than the original oil products, and their further 
transformations are implemented by different organisms. Of the oil 
products the first to be degraded are paraffins, and subsequently 
cycloparaffins. The polyaromatic hydrocarbons are most stable. 
The total oil oxidation rate depends on the ambient temperature 
and oxygen content in the water, and this last factor can be used 
as the indicator of the intensity of contamination destruction 
processes.
It is estimated that, in order to oxidize 4 liters of crude oil, as 
much oxygen is consumed, as is contained in 1 500 000 litres of sea 
water saturated with oxygen. It is contained by a 30 cm thick layer 
of sea water in the area of 500 m
2
. As a result of the degradation 
process and the mechanical action of waves the homogeneous oil 
film is gradually being destroyed, initially through formation of the 
oil droplet emulsion in the water, from which, through evaporation 
and adhesion, greasy oil clumps are formed, which then are often 
washed ashore.
Through the natural oil degradation processes the water 
environ ment decontamination of the oil pollution is accomplished. 
In the past, water pollution with oil was eliminated either by 
adding a variety of surfactants to the water, which helped to destroy 
the  film  on  the  surface,  or  carbonized  sand,  which  contributed  to 
the sedimentation of the surface film. However, this approach had a 
disadvantage – it did not fundamentally eradicate the environ mental 
pollution, but simply transferred it to another location or time 
postponed?. In addition, the toxic effects of many surfactants were 
even greater than those of oil products.
Given the urgency of the matter, recently many techniques 
have been developed to prevent the environ ment pollution by oil 
products, among which the preference should be given to the use of 
selectively operating micro-organisms. 
Today, the question arises regarding the contamination of water 
environ ment with synthetic detergents. 
Synthetic detergents 
contain a variety of sub‑
stances that may pollute 
the aquatic environment:
 
Œ bleaches / whitening 
agents (various 
oxidizing agents) such 
as sodium perborate;
 
Œ enzymes such as lipase;
 
Œ corrosion inhibitors 
such as sodium silicate; 
 
Œ fragrances; 
 
Œ inert substances 
(fillers) such as sodium 
sulphate;
 
Œ stabilizers, such as 
magnesium silicate.
However, from an 
environmental point of 
view, the most important 
are two components of 
synthetic detergents: 
1. surfactants; 
2. water softeners.

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180 
ENVIRONMENT, POLLUTION, DEVELOPMENT:  THE CASE OF UZBEKISTAN
Surfactants are a group of water-soluble organic substances, 
which concentrate on surfaces and reduce the surface tension of 
water. The main constituting elements which determine the impact 
of a substance on the surface tension of the aqueous solution is an 
asymmetric molecular structure: surfactant molecules consist of 
two  parts  –  a  water-repellent  grouping  –  a  hydrophobic  part  and 
a  –  hydrophilic  (water  attracting)  part.  In  soaps  the  hydrophobic 
group has a relatively long linear hydrocarbon residue, and the 
hydrophilic group is the carboxyl group. 
There are the following groups of surface active agents (SAA): 
1. Anionactive  SAA.  The  molecules  of  these  surface-active 
substances are composed of hydrocarbon residue (hydrophobic