Assessment of Soil Tolerance towards Contamination with Platinum Nanoparticles by Biodiagnostic Methods

-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.