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

 9.1. 
 Contamination of soil with organic 
substances 
The importance of the Earth’s upper crust contamination by 
oil products must be particularly emphasized. Soil, ground and 
groundwater are contaminated with oil and petroleum products due 
Sources of pollution, 
depending on the 
pollutant dispersion, are 
divided into two types:
 
Œ point source or 
concentrated pollution;
 
Œ diffuse or dissipated 
pollution. 

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9. POLLUTION OF SOIL 
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to misuse of technology or accidents in oil extraction, processing, 
transportation and storage facilities. The most typical sources of 
pollution are oil mining and processing, oil and petroleum product 
pipelines, oil transport, railway territories and locomotive depot 
areas, fuel stations, motor transport depots, fuel storage areas and 
abandoned military sites. 
In cases of oil and petroleum product spillage, when they enter 
the soil, they become subject to a wide variety of transformation 
processes. First, there are chemical processes: oxidation, reduction, 
hydrolysis, photolysis and hydration processes. Secondly, physical 
and mechanical processes: evaporation, sorption, dissolution, 
viscosity and density change. Thirdly, biological processes: 
biodegradation, biotransformation, bioaccumulation and toxicity 
changes. First of all the volatile oil fractions (benzene, xylene, 
octane,  lower  paraffins  and  cycloparaffins)  evaporate.  Migration 
of oil products is directly dependent on their solubility in water. 
The best solubility in water is typical of aromatic hydrocarbons. 
70-90% of the total weight of the aromatic hydrocarbons pass 
into an aqueous solution, regardless of the fuel type. Heavy oil 
product residues due to their physicochemical properties are almost 
insoluble in water and therefore move very little. Migration of oil 
products in soil is affected by the soil and its composition. Sorption 
characteristics of the soil and the ground below it are determined by 
the mineral properties, their structure and amount. Sorption consists 
of adsorption and ion exchange.
The highest sorption capacity is characteristic of clay and the 
organic substances present in soil. The organic substances and clay