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

particles; 
2.  as a nonaqueous liquid 
phase in the soil; 
3.  as a solution in the soil 
water and groundwa‑
ter; 
4.  adsorbed on soil 
particle surfaces;
Physical adsorption 
(sorption without the 
chemical interaction of 
substance to be sorbed 
and the sorbent) should 
be distinguished from 
chemical adsorption – 
chemisorption (the 
substance to be sorbed 
and the sorbent interact 
chemically).

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192 
ENVIRONMENT, POLLUTION, DEVELOPMENT:  THE CASE OF UZBEKISTAN
biological processes are of greater importance. In the absence of 
oxygen, oil product degradation slows down. The degradation rate 
of oil products is influenced by the presence of nutrients (nitrogen, 
phosphorus and potassium compounds). These substances contribute 
to the biochemical degradation of oil products. Biodegradation is 
important for soil and ground selfpurification. In nature, there are 
many microorganisms that use oil products as nutrients. 
Soil microorganisms (bacteria and soil fungi) convert com-
pounds harm ful to nature and humans into less toxic compounds. 
The inten sity of oil biodegradation process is determined by pollu-
tion, the environ ment and the characteristics and properties of 
the micro organisms therein. In the biodegradation processes the 
oil products serve as an energy source for microorganism activity. 
Micro organisms metabolize the pollution for the maintenance of 
their life processes and reproduction. The end product of micro-
biological bio degra dation is carbon dioxide, water and biomass. 
Generally, the natural biodegradation process occurs more efficiently 
in fertile soils with sufficient quantities of nitrogen and phosphorus. 
Bio degradation of petroleum products in oxidative conditions de-
creases in the following direction: normal alkanes → iso-alkanes → 
aromatic compounds → cyclic alkanes → high molecular weight cy-
clic compounds, asphaltenes, resins.
Environ mental  quality  can  be  significantly  affected  by  the 
substances used in agriculture – pesticides.
Currently there are about 30 000 known kinds of pesticides, which 
are divided into categories based on their application requirement.
Pesticides are classified according to their chemical composition 
and mode of action. Their main groups are organo chlorine com-
pounds (DDT, heptachlor, aldrin, dieldrin, etc.), organo phos pho rus 
compounds and pesticides, based on carbamates and chloro phenol 
acid. The most widely known representative of organo chlorine pes-
ticides is DDT. The largest quantities of pesticides are used to raise 
buckwheat and various oil plants. In some cases, the amount of use 
pesticides reaches 5000 g per hectare.
As  a  result  of  using  large  quantities  of  pesticides,  they  are 
accumu lating in the soil and can affect the quality of agricultural 
products and human health. Pesticide distribution and accumulation 
in soils is dependent on their stability, which in turn is influenced 
by their chemical structure, physical and chemical properties, and 
biological stability. Pesticide sorption and migration in the soil 
is  also  significantly  affected  by  the  soil  characteristics,  weather 
conditions, including the amount of precipitation. As a consequence 
of adsorption processes (resulting from physical, chemical and ion 
exchange), pesticides accumulate in the surface layer of soil to a 
depth of 20 cm. The possible contamination of underground waters 
Pesticides (from 
Latin pestis – disease and 
‑cide – to kill) are che‑
mical compounds that 
produce toxic effects on 
certain groups of living 
organisms, from bacteria, 
mould fungi to plants 
and warm‑blooded 
animals.
The most important 
groups of pesticides are: 
1.  insecticides – to 
exterminate insects; 
2.  herbicides – weed 
control; 
3.  fungicides – control of 
fungi; 
4.  zoocides – destruction 
of vertebrates; 
5.  repellents – to repel 
harmful insects; 
6. attractants – to attract 
pests; 
7.  defoliants – designed 
to promote fall of 
leaves; 
8. desiccants – dry the 
leaves, causes the 
seeds to mature