Search

Enzymatic activity of soils is the most important diagnostic indicator of the ecological state of soils affected by various types of anthropogenic impact. The aim of the study was to evaluate the enzymatic activity of ordinary chernozem (Haplic Chernozem) contaminated with Ag, Bi, Te, and Tl. Ten enzymes (catalase, dehydrogenase, peroxidase, polyphenol oxidase, ascorbate oxidase, ferrireductase, protease, phosphatase, invertase, and urease) were analyzed. According to the degree of inhibition of enzymes, heavy metals formed the following sequence: Tl > Ag > Bi > Te. With an increase in the concentration of heavy metals, the toxic effect on the activity of enzymes increased. The oxidoreductases showed greater sensitivity to Ag, Bi, Te, and Tl contamination than hydrolases. Among oxidoreductases, the highest sensitivity was found for ferrireductase, and the lowest one for ascorbate oxidase. According to the activity of enzymes of the hydrolase class, invertase was the most sensitive, and urease was the least sensitive. When contaminated with Ag, Bi, and Te, invertase had the highest informative value, and when contaminated with Tl, urease and polyphenol oxidase were the most informative. Among the enzymes of the oxidoreductase class, the highest information value was found for peroxidase, and the lowest one for ascorbate oxidase. Among the enzymes of the hydrolase class, invertase was the most sensitive, and phosphatase was the least sensitive. The results of the study can be used to assess the ecological state of soils contaminated with Ag, Bi, Te and Tl. [ABSTRACT FROM AUTHOR]

The ecotoxicity of Ag particles of different size has been assessed by microbiological, biochemical, and phytotoxic indicators for the upper layer (0–20 cm) of ordinary chernozem (Haplic Chernozem) in a laboratory model experiment. The effect has been studied of nano- (10 and 100 nm) and microparticles (1000 nm) of Ag at concentrations of 1, 10, and 100 mg/kg on the biological parameters of ordinary chernozem 30 days after contamination: the activity of catalase, dehydrogenases, ferrireductase, urease, peroxidase, polyphenol oxidase, invertase, phosphatase, the total number of bacteria, the abundance of bacteria of Azotobacter genus, the number of germinated seeds and the length of radish roots. It was found that the ecotoxicity of Ag particles depended on their size: in most cases, Ag particles 10 nm in size had a stronger ecotoxic effect on the biological parameters than particles 100 and 1000 nm in size. There were no significant differences in the ecotoxicity of 100 and 1000 nm Ag particles. The difference in the effects of Ag particles of different sizes increased with increasing Ag concentration in the soil: the higher the Ag concentration was in the soil (from 1 to 100 mg/kg), the more pronounced the difference was in ecotoxicity between 10 nm Ag particles and 100 and 1000 nm Ag particles. Phytotoxic indicators were more sensitive to contamination by Ag nanoparticles at all concentrations studied (1, 10 and 100 mg/kg); the total number of bacteria, invertase and phosphatase activity at 10 and 100 mg/kg; the abundance of bacteria of Azotobacter genus and the activity of dehydrogenases at 100 mg/kg. It is advisable to use these indicators in biodiagnostics of the ecotoxicity of Ag nanoparticles. [ABSTRACT FROM AUTHOR]

Thallium ecotoxicity was assessed in laboratory model experiments by changing in microbiological, biochemical, and phytotoxic properties of soils in the South of Russia: ordinary chernozem (Haplic Chernozem (Loamic)), seropesok (Eutric Arenosol), and slightly unsaturated brown forest soil (Eutric Cambisol), differing in texture, pH, and organic matter content. There was usually a direct relationship between Tl concentration and the deterioration rate of the studied soil properties. The ecotoxicity of Tl nitrate was higher as compared to Tl oxide. The ecotoxic effect of Tl was the strongest for chernozem and seropesok within 10 days and for brown forest soil within 30 days after contamination. Restoration of biological soil properties was recorded on the 90th day. The resistance to Tl contamination was the greatest for ordinary chernozem and the smallest for seropesok. The results obtained indicate a high ecotoxicity of Tl. [ABSTRACT FROM AUTHOR]

Soil tolerance towards contamination with platinum nanoparticles (PtNP) was assessed using biological parameters for soils of southern Russia differing in particle-size composition, organic matter content, and soil reaction. Model laboratory experiments were performed with samples from the upper (0–10 cm) layer of soils with contrasting genetic characteristics, i.e., ordinary chernozem (Haplic Chernozem (Loamic)), brown forest soil (Eutric Cambisol), and gray sandy soil under pine stand (Eutric Arenosol). PtNP concentrations of 0.01, 0.1, 1, 10, and 100 mg/kg were studied. Soil tolerance was estimated using sensitive and informative biological indices: the total number of bacteria, the activity of catalase and dehydrogenases, and germination degree of radish seeds, and radish root length. In most cases, low PtNP concentrations (0.01, 0.1, and 1 mg/kg) did not affect reliably the biological state of soils, whereas higher doses (10 and 100 mg/kg) worsened biological characteristics. The enzymatic activity of PtNP-contaminated soils decreased to a lesser extent than the phytotoxic and microbiological indices. Ordinary chernozem showed a higher tolerance towards PtNP contamination than brown forest soil and gray sandy soil. The results of this study can be used for predicting ecological risks of soil contamination with PtNP and for assigning the maximum permissible concentration for platinum in different soils. [ABSTRACT FROM AUTHOR]