Changes in some agrophysical characteristics of oil-contaminated soils following their washing with polysorbate 80 solutions

The study was aimed at comparing the effect of oil, diesel fuel, and motor oil on the capillary moisture capacity and hygroscopic moisture content of gray forest soil, as well as assessing changes in these characteristics of oil-contaminated soils following their washing with polysorbate 80. Water and a washing solution (with detergent concentrations of 1, 5, and 10 g/L) were added to the soil to be continuously mixed for 1 h at 20 °С using a shaker (60 rpm). The analyzed agrophysical characteristics of soils are shown to decrease when soils are contaminated with oil, diesel fuel, and motor oil at concentrations of 50, 150, and 300 mL/kg. The effect of motor oil on capillary moisture capacity is more pronounced than those of oil and diesel fuel at similar concentrations, while the effect on hygroscopic moisture content is, conversely, less pronounced. The washing of contaminated soils with polysorbate 80 partially restored these agrophysical characteristics; however, they remained lower than those of the original samples. The effectiveness of polysorbate 80 is also confirmed by the reduction in the phytotoxicity of contaminated soil samples following their washing with detergent solutions. At the level of oil contamination of up to 150 mL/kg, solutions containing 5 g/L of polysorbate 80 were found to be more effective, whereas at 300 mL/kg, it is recommended to increase the concentration of detergent up to 10 g/L. The recommended weight ratio of soil, washing solution, and water for soil washing is 1:1:4. Thus, the prospects for using polysorbate 80 to mitigate the negative impact of oil contamination in soil are demonstrated.