Accumulation of Ni by species of Brassicaceae on ultramafic soils in the Southern and Middle Urals

The study investigates the influence of geochemistry of ultramafic rocks on elemental composition of soils and plants. An ability of 13 species of Brassicaceae family growing on ultramafic soils, naturally contaminated by heavy metals, to accumulate Ni in aboveground shoots was studied. Ultramafic soils in the Middle and Southern Urals contain relatively high concentrations of Ni, Mg and other metals, low concentrations of Ca, as well as high Mg/Ca ratio, which is greater than 1. The soils have shown resemblance in geochemistry with ultramafic soils of other regions in the Word. Nine species of Brassicaceae showed low concentrations of Ni in shoots and leaves and were regarded as excluders, three species (Alyssum litvinovii Knjaz., Noccaea thlaspidioides (Pall.) F. K. Mey., Alyssum tortuosum Waldst. & Kit. ex Willd.) were hemi-accumulators, which contained lower than 0,01 % Ni in aboveground shoots, and one species (Alyssum obovatum (C. A. Mey.) Turcz.) was a hyperaccumulator. A. obovatum showed an ability to accumulate high concentrations of Ni in all ultramafic massifs of the Middle and Southern Urals. In contrast, A. tortuosum showed significant interpopulation variation of Ni concentrations in aboveground biomass. The highest concentrations of Ni were found in the population in Chabarninskyi massif, where the ability to hyperaccumulate Ni was established for this species.