The Choice of Indicators for Ecological Rationing of Petroleum Products in Chestnut Soils

The response of the microbial community of soils to different levels of oil contamination was studied in a model experiment by the parameters: basal respiration (BR), substrate induced respiration (SIR), carbon of microbial biomass (Cmic), potential denitrification (DNF), methanogenesis, and catalase activity. We analyzed light-chestnut (Haplic Kastanozems Sodic) and meadow-chestnut (Gleyic Kastanozems Chromic) soils of the dry-steppe zone of Stavropol region, differing in the organic matter amount, salinity, and the content of physical clay. The intensity of BR increased within a 30-day-period after the crude-oil input to the soils and caused the growth of Cmic due to activation of oil-oxidizing microorganisms in anaerobic zones of soils. The variations in DNF in light-chestnut and meadow-chestnut soils were in different directions, which was probably related to the organic-matter content and salinity of the soils. The catalase activity was a sensitive indicator of petroleum hydrocarbons in light-chestnut soil, but salinity was the determining factor for 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. The BR and SIR related to it were significant indicators, which did not depend on natural factors in chestnut soils. Catalase activity and DNF are limited by the salinity factor.