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.

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.

Sustainable agriculture is only possible if the agroecological services of the soil are preserved. Soil contamination with rare elements such as silver (Ag), bismuth (Bi), tellurium (Te), and thallium (Tl) is less studied, but their toxicity is no less high than in other heavy metals. Activity of soil enzymes is of great importance for the healthy functioning of soils, agroecosystem services, and their fertility. It is necessary to assess the ecological state of black soil using the most sensitive and informative indicators of the state of soils—their enzymatic activity. The objective of this research was to evaluate changes in activity of five priority soil enzymes (catalase, dehydrogenases, invertase, phosphatase, and urease) when contaminated with oxides and nitrates of Ag, Bi, Te, and Tl in a laboratory model experiment. The integral toxicity of nitrates and oxides of Ag, Bi, Te, and Tl was assessed by the integrated index of soil enzymatic activity. A comparison of the toxicity of oxides and nitrates of each element, according to the integrated index of soil enzymatic activity, allowed us to establish that Ag oxide is more toxic than Ag nitrate; Bi oxide is equivalent in its toxicity to Bi nitrate; and Tl and Te oxides are less toxic than Tl and Te nitrates. When contaminated with oxides, the most informative indicators are activity of invertase (Ag), urease (Bi, Tl), and phosphatase (Te). When contaminated with nitrates, the most informative indicators are activity of phosphatase (Ag) and invertase (Bi, Tl, and Te). Activity of phosphatase and catalase are the most sensitive to contamination by oxides and nitrates of Ag, Bi, Tl, and Te, and dehydrogenases, invertase, and urease are the least sensitive.

Soil health is the basis of ecological and food security for humanity. Among the informative indicators of soil health are microbiological indicators based on the intensity of the carbon dioxide release from the soil. The reaction of the microbial community of Haplic Chernozem Loamic, Haplic Arenosols Eutric, and Haplic Cambisols Eutric to contamination with oxides and nitrates of Ag, Bi, Tl, and Te at doses of 0.5, 1, 3, 10, and 30 derived specific permissible concentrations (SPC) was analyzed in the conditions of a vegetation experiment (the exposure period was 10 days). One derived concentration is assumed to be equal to three background concentrations of the element in the soil. The carbon content of microbial biomass in Haplic Chernozem varied between the experimental options from 6 to 218 mg/kg of soil; in Haplic Arenosols, from 3 to 349 mg/kg of soil; and in Haplic Cambisols, from 7 to 294 mg/kg of soil. Microbial biomass was a more sensitive indicator of contamination by the studied pollutants than basal soil respiration. A decrease in specific microbial respiration was found when Haplic Cambisols were contaminated with Ag, Bi, Te, and Tl oxides. Te and Tl nitrates had a significant toxic effect on each type of soil. At the maximum dose of Tl and Te nitrate, a decrease in basal soil respiration of 56–96% relative to the control and an increase in the metabolic coefficient by 4–6 times was found. The toxicity series of heavy metals averaged for all types of soils in terms of microbiological activity was established: Bi > Ag > Te > Tl (oxides) and Te > Tl > Ag > Bi (nitrates). Nitrates of the elements were more toxic than oxides. Soil toxicity due to Ag, Bi, Tl, and Te contamination was dependent on soil particle size distribution, organic matter content, and soil structure. A series of soil sensitivity to changes in microbial biomass and basal soil respiration when contaminated with the studied pollutants: Haplic Arenosols > Haplic Chernozems > Haplic Cambisols. When diagnosing and assessing the health of soils contaminated with Ag, Bi, Tl, and Te, it is advisable to use indicators of soil microbiological activity.

Thallium (Tl) was introduced into Haplic Chernozem in the amounts of 3, 30, and 300 mg/kg, and biological indicators were observed at 10, 30, and 90 days after incubation in the laboratory experiment. An increase in biological activities; i.e., the total number of bacteria, Azotobacter spp. abundance, enzymes (catalase, dehydrogenases), and phytotoxic indicators (germination rate of radish) after 30 days of Tl exposure were noted. The total number of bacteria and Azotobacter spp. abundance, enzyme activity, and phytotoxicity were more sensitive (16–76%) and informative (12–65%) indicators compared to the control, respectively. Integral biological indicators of soil state (IIBS) noted at 10, 30, and 90 days decreased at a dose of 30 and 300 mg/kg by 13–43% in relation to the control. An increase in Tl concentration and duration of exposure (up to 90 days) inhibited biological properties and caused ecotoxicological effects, respectively. We concluded that the use of individual indicators served as an indicator of the state of the soil.

Soil contamination with such rare heavy metals as silver (Ag), bismuth (Bi), tellurium (Te), and thallium (Tl) leads to disruption of its agricultural and ecological functions. Each of these rare heavy metals has a different level of soil toxicity, which affects the ecological state of the soil and its recovery degree estimated by biological indicators. The work objective is to assess the ecotoxicity of oxides and nitrates of silver, bismuth, tellurium, and thallium by biological indicators of Haplic Chernozem. Under the conditions of a laboratory simulation experiment, silver, bismuth, tellurium, and thallium were introduced into the samples of soil. The ecological state of the soil for each incubation period was assessed by the activity of soil enzymes (catalase and dehydrogenases), the intensity of seed development in polluted soil (the length of shoots and roots of winter wheat), and microbiological indicators (the total number of bacteria and Azotobacter sp. abundance). For 90 days, when contaminated with oxides of silver, bismuth, tellurium, and thallium, the most sensitive biological indicator was the length of wheat roots; when contaminated with nitrates, the total number of bacteria was the most sensitive biological indicator. The most informative biological indicator for contamination with both chemical forms of rare elements (silver, bismuth, tellurium, and thallium) was the Azotobacter sp. abundance. The most ecotoxic elements among those studied were thallium and tellurium, both in the form of oxides and nitrates. The results of the study may be useful for biomonitoring and diagnostics of the state of soils contaminated with silver, bismuth, tellurium, and thallium.