BIOREMEDIATION OF CRYOGENIC SOILS WITH FRESH AND OLD OIL POLLUTION: SPECIFIC FEATURES AND ASSESSMENT OF EFFICIENCY

Bioremediation is the most relevant and popular method of soil purification from oil pollution, especially in the northern regions. The results of field experiments to study the influence of the age of oil pollution on the efficiency of microbiological remediation of soils on the territory of the former oil pipeline (southwest of Yakutia) are presented. Purification was carried out by introducing the biological preparation based on enrichment cultures of indigenous hydrocarbon-oxidising microorganisms, previously isolated from the soils of this territory. It was found that the degree of destruction of fresh pollution a year after bioremediation was 77.4 %, and for old 7-year-old pollution it was only 34.3 % (of the level that remained 7 years after the oil spill). For the first time, a decrease in the efficiency of bioremediation processes has been considered from the standpoint of the chain free radical mechanism of microbiological oxidation. In the absence of a readily oxidised substrate, specifically alkanes from n-C12 to n-C24, as well as 12,13-methylalkanes, which naturally degraded over 7 years, the initiation of oxidation slows down, and the addition of the biological preparation no longer allows achieving high purification efficiency. In addition, the formation of intermediate reaction products (high-molecular naphthene-aromatic hydrocarbons) could inhibit the chain oxidation process due to the formation of stable intermediate radicals. The new formation of resins during bioremediation leads to hydrophobisation of soils and disruption of their water-air regime, which also could have a negative effect on the oxidative biodegradation of oil pollution. It has been shown that the method of bioremediation of oil-contaminated soils is most effective in the case of fresh oil spills.