Transformation of heavy petroleum during chemical and biological degradation in soil

Trends in the constitutional changes of the Lebyazhinskoe-field heavy oil a fter chemical oxidation and its 6-month biodegradation in soil were studied . It was shown that quantitative changes in the composition of high-molecul ar-weight biomarkers take place, together with the degradation of normal an d isoprenoid alkanes, during the transformation of an A(2) type labile oil into a solid product that is similar to a type B-1 natural asphaltite. Thes e changes represent a decrease in proportion of epimers having the biologic al configuration of 20-R methyl in the aliphatic molecular chain and the se lective degradation of the steroid ring of cholestane C-27 epimers, resulti ng in their almost complete disappearance in the petroleum degradation prod ucts. A comparatively higher stability of the high-molecular-weight C-28 an d C-29 homologues of cholestane and C-29-C-33 hopanes in bacterial degradat ion processes allows these biomarkers, in particular, the adiantane/hopane ratio, to be used for identifying the presence of petroleum hydrocarbons in soil and determining the genotype of soil-polluting petroleum.