Distribution of Chromium and Nickel in Plants and Soil from Serpentine and Other Sites

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Abstract
Plants and soils from a range of serpentine sites on Unst (Shetland Islands), at Greenhill (Aberdeenshire [Scotland, United Kingdom]) and at Kraubath (Austria) were analyzed for Cr and Ni. Samples of the shoots of a range of species from various serpentine sites including the spoil heaps of chromite mining showed that concentrations of Ni and Cr were species-specific. This specificity was confirmed by the results of the analyses of plants of 8 spp. [Silene acaulis, S. maritima, Anthyllis vulneraria, Cerastium nigrescens, Thymus drucei, Armeria maritima, Plantago maritima, Agrostis Stolonifera] growing on a single site. The mean Ni concentration in shoots of S. acaulis was 5 times that for S. maritima. Positive correlations between Cr and Ni levels in the shoots of the plants were established for 5 of the 8 spp. examined and other inter-element correlations observed in some species. Roots of individuals of 3 species were analyzed and the Ni concentrations (ash weight basis) approach or even exceed the soil concentrations, whereas the Cr concentrations in the roots were well below soil values. The availability of Cr and Ni in serpentine and non-serpentine soils was studied using a range of extractants. All the chemical methods of extraction tested were unsatisfactory. The concentrations of the elements present in the plants were considered to give the best measure of availability. Addition of 51CrO42- or 51Cr3+ to soils showed that both forms were strongly bound and not readily solubilized using a variety of extractants.