Functioning of Petroleum-Hydrocarbon-Contaminated Soils in the Taiga Zone of Western Siberia

Soils of two pairs of catenas were studied under conditions of petroleum-hydrocarbon (PH) contamination and lack of exposure within the Middle Taiga subzone (Tyumen oblast). The first pair of catenas were Gleyic Albic Podzol, Dystric Gleyic Histic Fluvisols, and Dystric Gleyic Fluvisols, and the second pair of catenas were Albic Gleyic Retisols, Albic Gleyic Histic Retisols, and Dystric Histic Gleysols. The effects of PH contamination on the biological characteristics of soils (respiration and catalase activity) and the possibility of their use for rationing the content of PH in soils were evaluated. The lateral migration of PH in soils prevailed over the radial one. The highest concentrations of PH were adsorbed in the upper peat layer (from 83 to 399 g kg^–1). For soils of the superaqual position, a radial monotonously decreasing distribution of PH along the profile was revealed (from 40–50 to 3–4 g kg^–1). The contamination of soils with PH caused a violation of the barrier and transformational hydrosphere functions of soils. The pH reaction of soils significantly changed towards alkaline (0.5 to 2.0 pH units). The accumulation of chlorides (to 0.7 g kg^–1) with a maximum in soils of the superaqual position was recorded; a reliable correlation was established between the pairs: the content of PH–pH, PH–Cl^–, and Cl^––pH, which indicated the income of crude oil into the soil as a result of emergency pipeline brake. PH underwent changes over time: heavy high-boiling hydrocarbons (99.9%) were present in the soils after 3 years of pollution. A significant correlation was revealed between PH and basal respiration (BR): direct for humic and reverse for organic soil horizons. It was found that the microbial coefficient qCO₂ in organic soils of Western Siberia decreased under oil contamination contrary to PH concentrations. A negative correlation was found between PH concentrations and catalase activity in soils (R is from –0.80 to –0.90, p < 0.05). The PH contents at which soil functioning is stable are substantiated: no more than 6.8 g kg^–1 for soils of the first year of contamination and 2.3 g kg^–1 for soils of contamination during 3 years and high concentrations of salts.