Zinc, cadmium and thallium distribution in soils and plants of an area impacted by sphalerite-bearing mine wastes

Abstract

An area affected by the long-term weathering of sphalerite-bearing mine wastes was studied in order to assess the environmental fate and behaviour of different toxic elements occurring in this mineral. Soil and plant samples were collected at different distances from the polluting sources and analysed for the content and distribution of Zn, Cd and Tl. Soils are highly polluted with Zn and Cd, reaching total concentrations up to 92,940 and 218mgkg−1, respectively. Soil contamination with Tl appears slight, with maximum total concentrations of 1.13mgkg−1. Mobile contents of Zn and Cd also reach high values, above 500 and 5mgkg−1, respectively. There is a great risk of an additional mobilization of Zn and Cd under acidic oxidizing conditions, whereas Tl mostly occurs in the residual fraction. Of the plants growing in this area, Jasione montana L. and Orchis maculata L. show a high risk of Cd incorporation in the trophic chain. These plants accumulate Cd concentrations up to 12.6 and 4.50mgkg−1 in their aerial parts.