Vodyanitshii, and 2 co-authors, reported in 2021 that in recent years, an increase in the input of lanthanides (Ln), an important group of heavy metals (HMs), has been observed in the environment throughout the world (in particular soil). Anthropogenic Ln sources are mainly connected to phosphogypsum, Ln-bearing microfertilizer and micronutrients, and mine waste. Therefore, assessment of the hazards associated with the presence of Ln in the soil is an urgent issue.
Hazardousness, depends strongly upon the buffer capacity of a specified soil, and is determined by the organic matter content, the pH value and other soil properties. For a standard soil (containing 10% organic matter and 25% clay), the discrepancy of the hazardousness of HMs can be estimated based on the maximum permissible concentration (MPC) values proposed by ecologists in the Netherlands. Low levels of Ln contamination in the soil are found, making it possible to classify them in the group of moderately and weakly acting pollutants. The MPC value proposed for cerium (Ce) in the standard soil is 44 mg = kg−1. Approximate MPC values for several other lanthanides (Ln, Pr, Nd, Sm, Gd and Dy) in soils were proposed based on MPC values for freshwater sediments in the Netherlands. According to the MPC value, Ln falls into the group of moderate- and low-hazardous heavy metals.
The authors concluded that Lanthanides (REEs) fall into the moderate low-hazardous heavy metal groups. At the same time a significant increase in Ln input to the soil makes the critical assessment of associated hazardous risk an urgent issue. The hazardousness of Ln relies on both peculiarities of each
metal and the buffer capacity of the given soil. The buffer capacity, in turn, depends on the content of organic matter, pH value and other soil properties. Special attention is paid to the necessity of defining the MPC Ln contents in soils with different buffer capacities and methods of soil remediation contaminated with REEs.
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