Distribution of Rare Earth Elements in the Soil–Plant System in the Zone Affected by Enterprises for the Extraction and Processing of Apatite–Nepheline Ores of the Khibiny Alkaline Massif

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The geochemical features of REE distribution in the soil–plant system in the impact zone of apatite–nepheline ore mining and processing enterprises of the Kola Peninsula were studied. Samples of podzolic and wetland soils, plants (birch leaves (Betula subarctica) and sphagnum moss (Sphagnum L.)) affected by mining and processing activity at the Khibiny alkaline massif, and atmospheric aerosols (main transport medium) were investigated. Rare earth elements were analyzed in plants, soils, and aerosols by inductively coupled plasma mass spectrometry. The contents of REE in soils, birch leaves, and moss affected by mining and processing operations on the apatite–nepheline ores of the Kola Peninsula are reported. It was shown that the soils are characterized by salt extraction pH values from 3.23 to 7.31, and there is a moderate correlation between the total REE content in the soils and the pH of salt extraction (r = 0.40, p < 0.001). Data on REE content in atmospheric air in the cities of Kirovsk and Apatity were obtained for the first time. The total concentrations of REE in the birch leaves and mosses were found to exceed the reference plant value by factors of 4.4 and 185, respectively, which indicates the outstanding role of moss as a bioindicator and superaccumulator. The highest REE contents accompanied by high phosphorus, fluorine, and strontium are typical of sites located in the immediate vicinity of railway tracks. It was established that an increase in the La/Yb ratio is an indicator of soil contamination with apatite ore dust, which is a new diagnostic criterion for monitoring the environmental impact of mining and processing facilities. The calculated biological concentration factors decreased in the La–Lu sequence for both plant species. It was found that the Eu biological concentration factor of the birch leaves was significantly higher than those of neighboring REE. It was shown for the first time that selective Eu accumulation occurs in the soil–birch leaf system, which results in a factor 2–10 increase in the Eu anomaly in the birch leaves relative to the soil. In contrast, Eu fractionation does not occur in the source rock–soil–moss system.