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 use of silver in various spheres of life and production leads to an increase in environmental pollution, including soil. At the same time, the environmental consequences of silver pollution of soils have been studied to a much lesser extent than those of other heavy metals. The aim of this study is to estimate silver ecotoxicity using the soil state biological indicators. We studied soils that are significantly different in resistance to heavy metal pollution: ordinary chernozem (Haplic Chernozems, Loamic), sierosands (Haplic Arenosols, Eutric), and brown forest acidic soil (Haplic Cambisols, Eutric). Contamination was simulated in the laboratory. Silver was introduced into the soil in the form of nitrate in doses of 1, 10, and 100 mg/kg. Changes in biological parameters were assessed 10, 30, and 90 days after contamination. Silver pollution of soils in most cases leads to deterioration of their biological properties: the total number of bacteria, the abundance of bacteria of the genus Azotobacter, the activity of enzymes (catalase and dehydrogenases), and the phytotoxicity indicators decrease. The degree of reduction in biological properties depends on the silver concentration in the soil and the period from the contamination moment. In most cases, there is a direct relationship between the silver concentration and the degree of deterioration of the studied soil properties. The silver toxic effect was most pronounced on the 30th day after contamination. In terms of their resistance to silver pollution, the studied soils are in the following order: ordinary chernozem > sierosands ≥ brown forest soil. The light granulometric composition of sierosands and the acidic reaction of the environment of brown forest soils, as well as the low content of organic matter, contribute to high mobility and, consequently, high ecotoxicity of silver in these soils. The regional maximum permissible concentration (rMPC) of silver in ordinary chernozem (Haplic Chernozems, Loamic) is 4.4 mg/kg, in sierosands (Haplic Arenosols, Eutric) 0.9 mg/kg, and in brown forest soils (Haplic Cambisols, Eutric) 0.8 mg/kg.
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, 1,000, 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.
The effect of silver pollution on the phytotoxicity of soils of varying degrees of resistance: chernozems, sierosands and brown forest soils was investigated. A direct relationship was observed between the concentration of the element in the soil and the length of the radish roots. At a silver concentration of 10 mg/kg, the highest toxicity was established on sulphurous sand and brown forest soil. A dose of 100 mg/kg had the greatest inhibitory effect on the length of the roots of radishes grown on ordinary chernozem, sierosands, and brown forest soil at 17, 24, and 29 % of the control, respectively. According to the degree of resistance to silver pollution, according to the radish root length indicator, the studied soils form the following series: ordinary chernozem (90) ≥ sierosands (88) > brown forest soil (81). The toxic effect of silver depends on the concentration of the element in the soil, the particle size distribution, the reaction of the soil environment and the content of organic matter in the soil. The greatest resistance of common chernozem to silver contamination is due to the particle size distribution, high humus content (3.7 %) and neutral alkaline-acid conditions (pH = 7.8). The light particle size distribution of the sierosands does not provide a sufficient absorption capacity for fixing silver in the soil. Brown forest soil is most sensitive to silver, as it has an acidic soil reaction (pH = 5.8), in which this element is mobile and has a toxic effect on the radish root system.
Aim. To assess the resistance of soils in the south of Russia to silver pollution using biological indicators.Methods. The contamination of soils in southern Russia (ordinary chernozem, grey sandy and brown forest soils) was simulated with silver under laboratory conditions. Soils were contaminated with water‐soluble silver nitrate in order to reveal the maximum ecotoxicity of silver. Soil stability was assessed according to the most sensitive and informative biological parameters in dynamics of 10, 30 and 90 days after pollution. Results. Silver contamination inhibits the activity of oxidoreductases (catalase and dehydrogenases), reduces the total number of bacteria and the growth and development of radish. For all soils, a direct relationship was noted between silver concentration and the degree of deterioration of soil properties. The toxic effect of silver was most pronounced on the 30th day after contamination. According to their resistance to silver pollution, the soils investigated form the following sequence: ordinary chernozem> grey sandy soil ≥ brown forest soil. Conclusion. The light granulometric composition of grey sandy soils and the acidic reaction of the environment of brown forest soils, as well as the low organic matter content, contribute to the high mobility and high ecotoxicity of silver in these soils. Regional maximum permissible concentrations (MPCs) of silver content in ordinary chernozems, grey sandy and brown forest soils have been determined as ‐ 4.4, 0.9 and 0.8 mg/kg, respectively.
The study assessed the ecotoxicity of various chemical compounds of silver (nitrate, oxide, sulfide, nanoparticles) by indicators of phytotoxicity of ordinary chernozem. The effect of nitrate, oxide, sulfide and silver nanoparticles in concentrations of 0.5; 1; 5; 10; 50 and 100 mg/kg of ordinary chernozem on the germination and length of radish roots 30 days after contamination was evaluated. In most cases, a negative effect of silver chemical compounds on phytotoxic indicators of ordinary chernozem was noted. The degree of ecotoxicity of silver is affected by its concentration in the soil. Silver nitrate, which is highly soluble in water and provides greater mobility of silver in the soil in the form of Ag2+, has a somewhat greater ecotoxicity. Practically insoluble in water forms showed slightly less negative impact. According to the germination of radish, a number of toxicity of chemical compounds (% of control) has been compiled: nitrate (84) > sulfide (87) > oxide (88) > nanoparticles (91); according to the length of the radish roots, a number of toxicity of chemical compounds of silver (% of the control) has been compiled: nitrate (90) > oxide (95) ≥ nanoparticles (95) ≥ sulfide (95). Keywords: SOIL, NITRATE, OXIDE, SULFIDE, NANOPARTICLES, GERMINATION, ROOT LENGTH, CONTAMINATION
Pollution by platinum (Pt) is an emerging threat to forest soil health. The widespread use of Pt nanoparticles (NPs) in gas neutralizers for automobile exhaust has sharply increased the amount of PtNP pollution in the environment, including forest ecosystems. Recently, territories with Pt concentrations greater than 0.3 mg/kg in soil have been discovered. This concentration is 750 times greater than the background content in the earth’s crust. Cambisols, the most prevalent forest soil type in boreal forests that determines the functioning of the entire forest ecosystem, occupy a significant share of the Earth’s soil cover, which is about 1.5 billion hectares worldwide, or 12% of the entire continental land area. This shows the importance of studying the effect of pollution on this type of soil. In this study, laboratory simulations of PtNP contamination of the Haplic Cambisols Eutric at concentrations of 0.01, 0.1, 1, 10, and 100 mg/kg were carried out. The effect of PtNPs on soil properties was assessed using the most sensitive and informative biological indicators. The total number of bacteria was studied by the methods of luminescent microscopy, catalase activity (gasometrically), dehydrogenases activity (spectrophotometrically), germination, and length of roots by the method of seedlings. It was found that at the concentrations of 0.01, 0.1, and 1 mg/kg of PtNPs, there was either no effect or a slight, statistically insignificant decrease in the biological state of Haplic Cambisols Eutric. Concentrations of 10 and 100 mg/kg of PtNPs had a toxic effect on all the studied parameters. No statistically significant stimulating effect (hormesis) of PtNPs on the biological properties of Haplic Cambisols Eutric was observed, which indicates the high toxicity of PtNPs and the importance of studying the consequences of soil and ecosystem contamination with PtNPs. However, when the content of Pt in the soil was 1 mg/kg, there was a tendency to stimulate germination, the length of radish roots, and the total number of bacteria. The toxicity of PtNPs measured by biochemical indicators (activity of catalase and dehydrogenases) starts at a concentration of 100 mg/kg for phytotoxic effects (germination and root length of radish) and 10 mg/kg for microbiological effects (total number of bacteria).
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.
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