In recent years, silver nanoparticles (AgNPs) are increasingly used in various industries due to their antibacterial properties, which lead to an increase in pollution of the environment and soil ecosystems. However, the ecological effects of soil pollution by AgNPs were poorly studied than that with AgNPs of other metal-based NPs. The aim of this study is to assess the influence of AgNPs on the biological properties of Haplic Chernozem. Silver was introduced into the soil in the form of AgNPs with a concentration of 0.5; 1; 5; 10; 50, and 100 mg/kg in laboratory conditions. The influence of AgNPs on the biological properties of Haplic Chernozem was assessed 30 days after contamination. The degree of reduction in biological properties depends on the AgNPs concentration in the soil. This study showed that the sensitivity to contamination by AgNPs in the total number of bacteria and enzymatic activity was more than that in the abundance of bacteria of the genus Azotobacter. The integrated index of biological state (IIBS) of Haplic Chernozem was decreased by contamination with AgNPs. Silver nanoparticles in the concentration of 10 mg/kg caused a decrease in the indicator by 13% relative to the control. It also decreased IIBS by doses of 50 and 100 mg/kg by 22 and 27% relative to the control. All used biological indicators could be used for biomonitoring, biodiagnosis, bioindication, and regulation of ecological condition of soil contamination by AgNPs.

The work objective was to assess the ecological state of soils by changing the residual oil content and restoring catalase activity after remediation. The soils were selected in various ecosystems: a steppe of the Rostov Region (Haplic Chernozem), beech-hornbeam forests in the Republic of Adygea (Haplic Cambisols), and semi-desert of the Caspian province of the Republic of Kalmykia (Eutric Cambisols). Soil samples were polluted with oil at a concentration of 5% of the soil mass. After that, ameliorants (biochar, nitroammophoska, sodium humate, and Baikal EM-1) were introduced into the oil-contaminated soil. The catalase activity of Haplic Cambisols was stimulated only with the introduction of D₂ biochar by 11% relative to the control, and in Haplic Chernozem, catalase was most stimulated with the addition of nitroammophoska D_0.5 and D₁ by 65% and 57% of the control, respectively. Nitroammophoska in all doses significantly stimulated the enzymatic activity, in Eutric Cambisols by four to six times compared to the control. The range of soil stability determined by catalase activity: Eutric Cambisols > Haplic Chernozem > Haplic Cambisols. Thus, it is most effective to apply biochar in doses of D and D₂ and D_0.5 and D nitroammophoska during the remediation of oil-contaminated Haplic Chernozem. For the remediation of Haplic Cambisols, it is effective to introduce biochar in dose of D₂, and Eutric Cambisols—biochar and sodium humate in dose of D_0.5 and nitroammophoska (all doses). The results of the study allow using catalase activity as a very informative and statistically significant diagnostical indicator of the health of oil-contaminated soils after remediation.

An increase in the penetration of metal-based nanoparticles (NPs) into the environment requires an assessment of their ecotoxicity as they impair the critical activity of plants, animals, bacteria, and enzymes. Therefore, the study aimed to observe the effects of metal-based NPs, including copper (Cu), nickel (Ni), and zinc (Zn), on the Cambisols, which cover a significant part of the earth’s soil and play an important role in the biosphere. Metal-based NPs were introduced into the soil at concentrations of 100, 1000, and 10,000 mg/kg. The biological properties of the soil are being investigated as the most sensitive to external contamination. The highest ecotoxicity of the studied pollutants introduced into the soil at the same concentrations was shown by Cu (up to 34%) and Zn (up to 30%) NPs, while Ni NPs showed less (up to 22%). Microbiological (total number of bacteria, Azotobacter sp. abundance) and phytotoxic properties (radish seed germination and length of roots) of Cambisols were more sensitive (22–53%) to pollution by NPs of Cu, Zn, and Ni, while enzymatic activity (catalase and dehydrogenases) showed less sensitivity (14–32%). The present results could be useful for biomonitoring the state of contaminated soils, especially by NPs.

Petroleum hydrocarbon contamination disrupts ecological and agricultural soil functions. For their restoration, bioremediation agents of various natures are used (nonorganic or organic fertilizers, bacterial preparations, adsorbing agents) featuring different remediation mechanisms (adsorption or biostimulation of petroleum hydrocarbon decomposition). The objective of this research is the assessment of the ecological condition of petroleum hydrocarbon-contaminated Haplic Chernozem Calcic after the application of bioremediation agents of various natures. The influence of glauconite, nitroammophos, sodium humate, the bacterial preparation “Baikal EM-1”, and biochar on the intensity of petroleum hydrocarbon decomposition and the ecological condition of Haplic Chernozem Calcic was analyzed. The ecological condition of Haplic Chernozem Calcic was assessed based on the residual content of petroleum hydrocarbons in soil and the following biological parameters: changes in the number of soil bacteria, activity of catalase and dehydrogenases, soil respiration (CO₂ emission), germinating ability, lengths of roots and shoots, and integrated index of the biological state. The minimum concentrations of residual petroleum hydrocarbons in soil were observed after the use of biochar (44% from initial content) and glauconite (49%). The biological properties of soils were affected in different ways. Soil respiration was stimulated by 3-6-fold after adding nitroammophos. Indices for the intensity of the early growth and germination of radish in soil with glauconite, sodium humate, and biochar were increased by 37–125% (p < 0.01) compared with the reference value. After the application of biochar, sodium humate, and “Baikal EM-1”, the number of soil bacteria was 66–289% higher (p < 0.01) than the reference value. At the same time, the activities of catalase and dehydrogenases were inhibited by up to 35% in variants with bioremediation agents and petroleum hydrocarbons relative to the reference values. The maximum stimulation of the biological activity (as the integrated index of the biological state (IISB)) of Haplic Chernozem Calcic was observed after applying sodium humate and biochar, with 70 and 66% (p < 0.01) increases from the reference value, respectively. Considering the net cost of bioremediation agents, the maximum cost efficiency is achieved with “Baikal EM-1”, sodium humate, and biochar: 110, 527, and 847 USD·10³/ha, respectively. After using Baikal EM-1”, sodium humate, and biochar, the ecological state of Haplic Chernozem Calcic was restored.