The regularities of transformation of hydrocarbon composition in oil-contaminated soils of Sakhalin Island

The main types of soils in the northeastern part of the Sakhalin Island have been studied in conditions of oil pollution (1 year and 10 years), as well as their background counterparts. The regularities of hydrocarbons transformation in oil-contaminated soils are revealed, the possibility of launching self-purification processes based on the results of an assessment of the composition of petroleum hydrocarbons (TPH) is shown. The analysis of n-alkanes as markers of TPH biodegradation showed a change in their content and composition, depending on the degree and age of soil contamination by TPH, as well as the sorption capacity of soils. During the first year, the mechanisms of soil self-purification are triggered, leading to a change in the composition of n-alkanes: light fractions volatilized, alkanes C16–C23 undergo to biodegradation. Under conditions of 1-year oil contamination of soils, the composition of petroleum hydrocarbons undergoes significant changes, expressed in an increase in the proportion of microbial n-alkanes (ΣC20–25). An increase in the content of high molecular homologues ΣC26–C34 has been found in comparison with the initial state of oil-contaminated soils and the composition of oil. The calculations of CPI (coefficient of oddness), Ki (coefficient of biodegradation) and Kw (coefficient "degree of waxiness") demonstrateв the transformation of the composition of n-alkanes and, in general, the transformation of petroleum hydrocarbons in time. The use of the sum of odd n-alkanes C27, C29, and C31 as a diagnostic indicator is a solid base for selecting background soils in the area of hydrocarbon deposits.