Change in the Capillary Moisture Capacity and Phytotoxicity of Oil-Contaminated Soils under the Influence of the Oil-Destructive Biological Product “DOP-UNI” in a Short-Term Experiment

Contamination of gray forest soils with oil and diesel fuel in concentrations of 50, 150, and 300 mL/kg led to a decrease in the soil capillary moisture capacity. With the introduction of 50 mL of oil per kilogram of soil, this indicator decreased from 62 (corresponding to the best capillary moisture capacity) to 22.6%; for 150 mL/kg, down to 19.1%; and for 300 mL/kg, down to 12.6%. The effect of diesel fuel on the capillary moisture capacity of the soil was similar. At 50, 150, and 300 mL of diesel fuel per kilogram of soil, the capillary moisture capacity decreased from 62% down to 28.3, 20.0, and 13.8%, respectively. After applying the microbial oil-destroying preparation “DOP-UNI” and subsequent exposure for three weeks, it was possible to restore this agrophysical characteristic in part. Even for such a short exposure time, the capillary moisture capacity of the soil contaminated with oil (50–300 mL/kg) increased by 1.3–1.8 times after treatment with the biopreparation compared to the untreated oil-contaminated sample. However, the soil capillary moisture capacity still remained lower than in uncontaminated (control) soil samples. A similar trend was noted in the experiment with diesel fuel. In addition, the treatment of oil-contaminated soil with the biopreparation “DOP-UNI” for three weeks led to a decrease (by about 20%) in phytotoxicity at an oil contamination level of up to 150 g/kg. The data obtained allow us to suggest prospects for using the biopreparation “DOP-UNI” for remediation of soils contaminated with oil products and for restoration of their agrophysical properties. At the same time, lowering the temperature down to 10°C in the experiment did not have a significant effect on the efficiency of the biopreparation, at least during the 3-week experiments. This indicates that it is possible to use “DOP-UNI” at low temperatures, which is typical for the main oil fields in the Russian Federation.