Parameters of the Native Hydrocarbon Status of Soils in Different Bioclimatic Zones

Abstract

To characterize the native component of the hydrocarbon status of soils in different bioclimatic zones, representative soils were studied in the East European Plain within the middle and southern taiga, forest-steppe, and semidesert zones. The samples were analyzed for the contents of hexane-soluble bitumens (bitumoids), normal and iso-alkanes (C₁₄–C₃₅), individual polycyclic aromatic hydrocarbons (PAHs, polyarenes), and soil hydrocarbon gases. It was found that the parameters of the native hydrocarbon status of soils are rather similar in different bioclimatic zones. For the background (uncontaminated) soils forming on interfluves, the following concentrations of native hydrocarbons were determined: up to 25 ppm (often, less than 5 ppm) of hexane bitumoid, no more than 60 ppb of the sum of 11 PAHs, and no more than 1 ppb of individual n-alkanes. Polyarenes were represented mainly by the lightest two- and three-ring compounds. The content of hydrocarbon gases retained by the soils varied widely. In 100% of cases, methane was the most common gas (from 1.8 to 3994 ppmv, 5.14 ppmv on average). Ethylene was less common (0.04–54.5 ppmv, 4.1 ppmv on average). Heavier alkane gases were less common and were present in amounts ranging from 0.02 to 4.09 ppmv (on average, 0.53 ppmv).