ABSTRACT
The natural purification of soils contaminated with petroleum products takes a prolonged period of time (5-20 years) under the action of both biotic and abiotic agents. Microorganisms are the most important factor in soil self-purification. The process of soil selfpurification consists of several stages. In the first stage under the action of physicochemical agents some gaseous and volatile oil fractions are destroyed; later, under the action of soil biota, chiefly the decomposition of CIS-CIS n-alkanes, then the less accessible C27-C33 compounds as well as cycloparaffins (naphthenes) and polyaromatic hydrocarbons are subjected to the effects of biodegradation [1-3]. The biological properties of the soils and the content of certain oil-oxidizing microorganisms in them are directly dependent on their pollution by petroleum products. According to Zvyagintsev [4], soil pollution levels can be subdivided into four stages corresponding to the oil concentration and its effect on the soil microbial cenosis (Table 1). In order to intensify the natural processes of degradation of oil and its derivatives, some special biotechnologies for the purification of polluted territories have been developed that allow the purification to be accomplished within months or even days.
