Influence of carbon sorbents on the potential ability of soils to self-cleaning from petroleum pollution

In a laboratory experiment, the ability of the soil to self-cleaning under heavy petroleum pollution and the effect of biochars and shungites on the cleaning process were studied. Incubation of contaminated soils for 28 days at a constant humidity and temperature without addition of sorbents led to a decrease in the residual content of petroleum products by only 8%. The addition of biochar and shungite at a dose of 2.5% made it possible to reduce the content of petroleum under constant incubation conditions to 48.8% and 38%, respectively. It was shown that the incubation of oil-contaminated soils in the regime of variable humidity and temperature without the addition of sorbents makes it possible to reduce the content of petroleum by 32% over 28 days of the experiment. In the course of the study, methods were developed for determining substrate-induced respiration (SIR) in various incubation modes. Soil contamination with petroleum led to a significant decrease of SIR in the initial period of incubation from 12.8 C-CO2 µg/g h to 8.6 C-CO2 µg/g h, which returned to normal on the 14th day of the experiment. It has been shown that the introduction of biochars (to a lesser extent schungites) into oil-contaminated soils ensures the maintenance of SIR at the required level and increases the potential capacity of soils for self-purification. The paper discusses the possibilities of increasing the potential capacity of soils for self-cleaning under heavy oil pollution.