Potentially toxic element accumulation in two Equisetum species spontaneously grown in the flotation tailings

Decades of mining activity have resulted in the accumulation of significant amounts of tailings that are deposited over the natural vegetation, forming deposits tens of meters thick. The tailings are poor in organic matter and macronutrients and contain a high concentration of potentially toxic elements (PTE). Their surface remains unvegetated for long periods of time and is susceptible to fluvial and wind erosion. Equisetum arvense and E. telmateia appear to be the first colonizers in the tailings of the Pb-Cu-Zn mine in Serbia. Each plant was sampled along with its associated substrate. Pseudototal and available metals in the substrate, as well as total As, Cd, Cu, Fe, Mn, Ni, Pb and Zn concentrations in the plant parts were determined by atomic absorption spectrophotometry. The findings show that both species have high bioaccumulation capacity and tolerance to otherwise toxic concentrations due to efficient accumulation, immobilization, and detoxification of these elements in their underground parts. It is expected that the long-term presence of metal-tolerant horsetail species would increase the organic matter content of flotation residues, thus gradually improving their physical, chemical, and biological properties. This, in turn, would promote the natural succession of other metal-tolerant plant species and soil microorganisms.