Abstract

The effect of contamination with oil, lead, and their combinations and the influence of bioremediation with the use of microorganisms on the biological activity of leached chernozem (Luvic Chernozem) was comprehensively analyzed in a model experiment. The studied soil was sampled in Ufa district of the Republic of Bashkortostan and artificially contaminated with the listed pollutants. The soil was treated with hydrocarbon-oxidizing bacterial strains resistant to high concentrations of lead ions. All types of pollutants increased the soil phytotoxicity, while applied microorganisms reduced it, which was manifested in a rise in the seed germination index by 1.2‒19.2% as compared to untreated variants. The addition of lead into the oil-contaminated soil reduced the degree of decomposition of hydrocarbons by 4.4–11.2%. Bacterization of contaminated soils enhanced the degradation of hydrocarbons by 6.2–33.8%. The total number of microorganisms increased in soils with oil and with oil and lead. Actinomycetes were most sensitive to the presence of xenobiotics. By the end of the experiment, the enzymatic activity of the oil-contaminated soil decreased. The presence of lead caused a slight rise in the catalase and invertase activities in the first half of the experiment. The combined contamination significantly suppressed the activity of catalase and urease. Bioaugmentation exerted a favorable effect on the restoration of the soil enzymatic activity. The applied bacterial strains contributed to a decrease in phytotoxicity and to an increase in the enzymatic activity of the soil, which makes them promising agents for soil bioremediation.