Sergey Alekseevich Shoba

Th e response of the microbial community of soils to diff erent levels of oil contamination in a model experiment was studied according to indicators: basal respiration (BR), basal induced respiration (SIR), carbon of microbial biomass (Cmic), potential denitrifi cation (DNF), methanogenesis, catalase activity. Th e soils are represented by light chestnut (Haplic Kastanozems Sodic) and meadow-chestnut (Gleyic Kastanozems Chromic) dry-steppe zone of the Stavropol area, diff ering in the organic matter content, salinity and the content of physical clay. Th e intensity of BR increased aft er 30 days of the crude oil input into the soils and caused the growth of Cmic due to the activation of oil-oxidizing microorganisms in anaerobic zones of soils. DNF varied in light chestnut and meadow-chestnut soils not directly, that was probably due to the level of organic matter content in soils and their salinity. Catalase activity was a sensitive indicator for the petroleum hydrocarbons in light chestnut soil, but salinity was the determining factor in its activity in meadow chestnut soil. Biotesting with the use of worms Eisenia fetida showed the inability of test organisms to survive in non-contaminated chestnut soils. A signifi cant indicator that did not depend on natural factors in chestnut soils was BR and related indicators. Catalase activity and DNF have limitations on the salinity factor.

The soils of two pairs of catena were studied under conditions of petroleum hydrocarbon (PH) contamination and lack of exposure within the Middle Taiga subzone (Tyumen region). 1st pair of catena: Gleyic Albic Podzol, Dystric Gleyic Histic Fluvisols, Dystric Gleyic Fluvisols; 2nd pair of catena:Albic Gleyic Retisols, Albic Gleyic Histic Retisols, 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). PH contamination of soils led to a violation of the barrier and transformational hydrosphere functions of soils. The pH reaction of soils significantly changed towards alkalinization (0,5 to 2,0 pH units). The accumulation of chlorides (up to 0,7 g∙kg-1) with a maximum in the 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 holes. 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 the microbial coefficient of qCO2 in organic soils of Western Siberia under oil contamination decreased with an increase in the concentration of PH. A negative correlation was found between PH concentrations and catalase activity in soils (R = –0,80 – (–0,90), p<0,05). Th e levels of PH content at which stable soil functioning occurs are justifi ed: no more than 6,8 g∙kg-1 for soils with 1-year contamination and 2,3 g∙kg-1 for soils with 3-year contamination and high concentrations of salts.