Kurbatov Yuri Nikolaevich

This study assessed the impact of soil surface contamination with used motor oil on the migration and accumulation properties of zinc and copper, as well as estimated the activities of soil urease and catalase, two of the most important parameters characterizing soil self-healing processes under oil contamination. X-ray fluorescence, titrimetric, infrared spectrometry, and other methods were used to determine soil parameters and analyze petroleum products. Six years of monitoring under field experimental conditions revealed a significant accumulation of zinc in the surface soil layer (0–10 cm)—up to three times that of the control. This accumulation was due to the increased influence of the natural geochemical barrier—the upper organogenic soil horizon—by the added petroleum products, as well as the increased activity of ureolytic bacteria capable of precipitating this metal as insoluble carbonate minerals. Copper exhibits significant mobility under contaminated conditions, characterized by migration from the 0–10 cm layer and accumulation at a depth of 10–30 cm, exceeding the control level by up to 2.6 times, due to the high affinity of this metal for water-soluble fractions of petroleum hydrocarbons, heavy precipitation that fell during the monitoring period, and the presence of a thick clay layer at a depth of 60 cm and below, which served as a geochemical barrier preventing its further downward migration. Urease activity in the soil increased significantly, which was observed throughout the experiment. Soil catalase activity was inhibited immediately after the application of the petroleum product to the soil, and by the end of the study period, it increased to values 47,6% higher than the control level, indicating a gradual restoration of the microbiota and stimulation of soil self-purification processes.