Availability of elements in tundra soils on acidic and ultramafic rocks in the Polar Urals

The chemical properties of soils and their particle-size distribution in ecotopes of the Polar Urals mountain tundra were considered in relation with the lithological and geochemical features of the parent rocks. In the soils of ecotopes on the ultramafic massif, the contents of the total Ni (2830 mg/kg) and the total Cr (2327 mg/kg) were found to exceed their clarke values, which suggested the accumulation of these elements by plants and their migration with water. In the soils of the ultramafic massif, the average content of mobile Ni was 46.8 mg/kg, which exceeded the Ni MPC by 11.7 times. The average concentration of mobile Cr in the soils of the massif made up 0.35 MPC. In the soils of geochemical acidic rocks, the contents of mobile Ni and Cr were lower than their MPC levels. A higher content of particles with an average diameter ≥5 μm was found in the soils of the ultramafic massif.