Hydrocarbon status of soils in the asphalt deposit area (Samara Bend)

The composition and distribution features of the main components of soil hydrocarbon complex― organic (noncarbonate) carbon, hexane bitumoids, and individual polycyclic aromatic hydrocarbons (PAHs)―in the area of depleted Bakhilovo asphalt deposit (Samara oblast) have been studied. According to their proportions, three genetic types of soil hydrocarbon status are distinguished: (a) emanation–injection type prevailing within the limits of the former production field and characterized by anomalous contents of heavy resinous bitumoids (5000–7000 mg/kg on the average) throughout the soil profile and a high content of PAHs (4–9 mg/kg on the average, 29 mg/kg as the maximum, with the dominance of naphthalene homologues); (b) emanation–biogeochemical type confined to mechanogenically undisturbed soils within and beyond the deposit area, where the emanation component is manifested in soils with heavy texture and higher concentrations and very light composition of bitumoids in the lower parts of the soil profile; and (c) atmosedimentation–biogeochemical type characteristic of conventionally background soils with light texture; benzo[a]pyrene traces are detected among PAHs in the upper soil horizon, which indicates the input of this hydrocarbon with aerosols from the atmosphere; the concentrations of bitumoids and PAHs in parent rocks are lower than in the soils.