Ecotoxicity assessment of water-soluble platinum specie (PTCL₂) in soils with contrasting properties

Nowadays, soil contamination with platinum (Pt) is expanding at a fast rate. Platinum has a wide range of industrial applications, especially as automobile catalysts. Increased platinum emissions into the environment, primarily soil, stipulated by vehicles with platinum exhaust converters, result in the accumulation of platinum in soils at a level significantly exceeding background indicator. Moreover, some areas have already been detected as places with an excess of the background platinum level by 750 times (more than 2 mg/kg), but the toxicity of platinum has not been thoroughly investigated. Besides, standards for Pt content in soil have not yet been developed throughout the world. In a simulated experiment, the authors investigated the effects of Pt²⁺ contamination at its concentrations of 0.01, 0.1, 1, 10, and 100 mg/kg on the biological activity in three soil types contrasted in properties and resistance to heavy metal contamination, including Haplic Chernozem (slightly alkaline heavy loamy soil), Eutric Cambisol (acidic heavy loamy soil), and Eutric Arenosol (neutral sandy loam soil). Platinum was introduced into the soil in the form of its chloride (PtCl₂), which is the most mobile and toxic in the soil, with the following determination of the most sensitive and informative biological indicators of soil condition. They included phytotoxic indicators such as germination, root length, and shoot length; microbiological indicators, namely the total number of bacteria; and enzymatic activity involving the activity of catalase, dehydrogenases, invertase, urease, and phosphatase. Based on these indices, an integrated indicator of the biological soil condition was calculated to assess the magnitude of impairment in ecosystem functions of the soils. The Pt concentration, which preserved the most important ecosystem functions of the soil, ensuring its fertility, was taken as ecologically safe. These environmentally safe concentrations of Pt in the investigated soil types can be recommended for use in the field of environmental protection and agricultural and scientific activities as environmental standards for soils with different properties.