Trace element accumulation in plant species differently affected by abandoned tailings in the Riotinto mining district

Coarse, acidic and metal polluted substrata generated by extensive metal mining in the Riotinto area (Huelva province, SW Spain) are model habitats for biogeochemical studies and for designing plant-assisted remediation technologies. Major and trace element concentrations were determined in different plant parts from the few spontaneous species growing in areas differently impacted by abandoned mine waste: Erica andevalensis, Erica australis, Nerium oleander, Halimium ocymoides and Cistus ladanifer, in order to evaluate their potential for soil reclamation. E. andevalensis, which is an endemic species to the Iberian Pyrite Belt, forms monospecific patches in the most polluted sites and showed an asymptomatic scarcity of essential macroelements (Ca, Mg and P) in leaves. The two heathers accumulate very high concentrations of As, Cu, Fe, Pb, S and Zn in the root bark, but in their aerial parts only As and Pb (among potentially phytotoxic elements) are accumulated at higher levels than those reported for Erica species growing in unpolluted areas. Stems and leaves from N. oleander, H. ocymoides and C. ladanifer had remarkably higher Cd and Zn concentrations than those measured in E. andevalensis and E. australis. Although comparisons among plant species showed different element accumulation patterns, in general, all species have a common adaptative strategy: the selective uptake of essential elements and the exclusion of potentially phytotoxic elements. However, as the shrub E. andevalensis tolerates the most extreme edaphic conditions and its breeding and growing are compatible with local climatic conditions, it seems the most suitable species for the phytostabilization of abandoned waste in the Riotinto mining district.