The Level of the Efficiency of Bioremediation by Oil-Contaminated Brown Semi-Desert Soil of the Republic of Kalmykia (Model Experiment)

Abstract

The brown semi-desert soils of the Republic of Kalmykia are subject to high levels of oil pollution. To assess the ecological state of soils, it is necessary to analyze not only the residual oil content, but also the biological indicators of soils. The purpose of this work was to evaluate the effectiveness of bioremediation of the oil-contaminated brown semi-desert soil of the Republic using physicochemical and biological indicators. Biochar, nitroammophos, sodium humate, and Baikal EM-1 were added to oil-contaminated soil (5% of the soil mass). To assess the effectiveness of remediation of brown semi-desert soil after 30 days, the residual oil content, the activity of catalase and dehydrogenases, the number of bacteria, the length of the roots, and the germination of radish were studied. It has been established that the introduction of biochar and Baikal EM-1 reduces the residual oil content in brown semi-desert soil. Biochar and nitroammophos affect the contents of easily soluble salts, and Baikal EM-1, the redox potential. Sodium humate stimulates catalase activity (r = –0.48), shoot length (r = –0.54), roots (r = –0.54), and radish germination (r = –0.64). Nitroammophos stimulates the number of bacteria (r = –0.56), the activity of catalase (r = –0.63), and dehydrogenases (r = –0.84), but inhibits the length of radish shoots and roots (Raphanus sativus L.). The application of Baikal EM-1 stimulates the number of soil bacteria (r = –0.83), the activity of dehydrogenases (r = –0.89) and inhibits the length of roots, shoots and germination. It is advisable to use the results of the study in biomonitoring and diagnosing the state of oil-contaminated brown semi-desert soils of the Republic of Kalmykia.