The effectiveness of different bioremediation methods (biostimulation, bioaugmentation, the sorption-biological method) for the restoration of soil contaminated with petroleum products in the Russian Subarctic has been studied. The object of the study includes soil contaminated for 20 years with petroleum products. By laboratory experiment, we established five types of microfungi that most intensively decompose petroleum hydrocarbons: Penicillium canescens st. 1, Penicillium simplicissimum st. 1, Penicillum commune, Penicillium ochrochloron, and Penicillium restrictum. One day after the start of the experiment, 6 to 18% of the hydrocarbons decomposed: at 3 days, this was 16 to 49%; at 7 days, 40 to 73%; and at 10 days, 71 to 87%. Penicillium commune exhibited the greatest degrading activity throughout the experiment. For soils of light granulometric composition with a low content of organic matter, a more effective method of bioremediation is sorption-biological treatment using peat or granulated activated carbon: the content of hydrocarbons decreased by an average of 65%, which is 2.5 times more effective than without treatment. The sorbent not only binds hydrocarbons and their toxic metabolites but is also a carrier for hydrocarbon-oxidizing microorganisms and prevents nutrient leaching from the soil. High efficiency was noted due to the biostimulation of the native hydrocarbon-oxidizing microfungi and bacteria by mineral fertilizers and liming. An increase in the number of microfungi, bacteria and dehydrogenase activity indicate the presence of a certain microbial potential of the soil and the ability of the hydrocarbons to produce biochemical oxidation. The use of the considered methods of bioremediation will improve the ecological state of the contaminated area and further the gradual restoration of biodiversity.

Elevated plant and microbial toxicity throughout the season was found in field experiments on bioremediation of diesel fuel (DF)-contaminated soil (4.5%). This was an indication of the presence of mobile toxic DF components and their metabolites. Introduction of granulated activated charcoal (GAC) was shown to decrease the bio- and phytotoxicity of petroleum-contaminated soil, resulting in a sharp increase in the abundance of petroleum degraders (both aboriginal and inoculated ones), as well as to create conditions for improved growth at the stage of post-treatment by phytoremediation. In spite of short-time deceleration of DF degradation, more complete decrease of hydrocarbon concentrations occurred in the presence of GAC, while simultaneous introduction of the sorbent and a biopreparation (and association of mesophilic petroleum-degrading strains) provided the best results. In these variants the concentration of petroleum hydrocarbons decreased to 0.19–0.21 and 0.13–0.14%, respectively, which was 1.5 and 2 times lower than the values for unsupplemented control. Thus, GAC introduction during bioremediation of DF-contaminated soils increases the efficiency of remediation and localizes the pollutants in the treated layer, which decreases the risk of their penetration into groundwater during in situ soil treatment.

The majority of Russia’s oil and gas-producing regions are situated in the northern part of Western Siberia, where sandy podzolic soils are prevalent. Due to the low buffering capacity of these soils and the severe Arctic climate, the conventional method of bioremediation for removing oil contamination is not effective. This study, for the first time, explores the potential of adsorptive bioremediation for purifying oil-polluted gley-podzolic soil. This approach involves introducing natural sorbents of various classes before soil treatment through bioremediation. The optimal conditions for soil treatment can be determined using the express phytotests based on white clover ( Trifolium repens ) seed germination. The results indicate that under the best conditions, which involve adding 2 % mixed sorbent based on granulated activated carbon (GAC) and diatomite (4:1) or Spilsorb, it is possible to minimize soil phytotoxicity after 2-3 warm seasons and reduce the content of total petroleum hydrocarbons to the permissible residual oil content (≤5 g/kg) established in the territory of the Khanty-Mansiysk Autonomous Okrug for recultivated agricultural soils. Moreover, other sorbents, such as peat, GAC, vermiculite, zeolite, and diatomite, can be used to reduce phytotoxicity to <33 %, allowing for additional soil decontamination through phytoremediation.

Due to the large volume of coal mining in the Russian Federation and other countries, there is a serious issue of the formation of waste heaps from coal dumps, which pose a significant threat to the environment of adjacent territories. One of such areas is the Donetsk coal basin, whose area is more than 60 thousand km2. Phytoreclamation is the most common and cost-effective method recommended for the restoration of degraded coal dump soil, which reduces the removal of toxic substances with dust emissions and water runoff. However, plant growth on these soils is hindered by their phytotoxicity and unfavorable physical and physicochemical properties. The aim of this research was to develop a biogeochemical technology for the reclamation of coal dumps in Donbas based on phytoreclamation with various additives. Our experiments involved soil samples taken from the upper layer of the Ayutinskaya mine waste heap in the Donetsk coal basin, as well as zonal ordinary chernozem samples. The experiments were conducted in microfield conditions in bottomless vessels with an area of 0.1 m2 dug into the ground. The additives used were wood biochar and other sorbents, including mineral (diatomite and vermiculite) and organic (acidic and neutralized peat) ones, as well as ordinary chernozem and quarry sand - clean and with biohumus additives. The soil was seeded with a drought-resistant lawn mixture. All additives had a positive effect on the growth of green mass of drought-resistant lawn, measured during 3 cuttings ib the vegetation season of 2024. However, the best results were obtained with the addition of neutralized peat and chernozem at doses of 25 %, as well as quarry sand at doses of 25 and 50 % with the addition of biohumus; at the same time, the additional addition of 5 % biochar to all these samples gave no desired result.