Effect of Platinum Nanoparticles (PtNPs) Pollution on the Biological Properties of Haplic Cambisols Eutric of the Caucasus Forests

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).