Phytoremediation of potentially toxic elements using constructed wetlands in coastal areas with a mining influence

Abstract

This paper proposes the use of wetlands as a phytoremediation strategy for areas of mining and maritime influence in the southeast of Spain. Potentially toxic elements (PTEs) tolerant and salinity-resistant macrophytes (Phragmites australis, Juncus effusus and Iris pseudacorus) have been used. The experiment is carried out in an aerobic artificial wetland using representative sediments affected by mining activities in the study area. Selected species were placed in pots containing substrates made with different mixtures of topsoil and/or peat, mining residues (black or yellow sand). After six months, rhizosphere, root and aerial parts were collected. A transfer study of As, Pb, Zn and Cu is performed, determining contents in rhizosphere and plant (aerial and underground part). From these data, the TF and BCF were calculated for each plant in 15 different substrates. The work is complemented by an initial study of scanning electron microscopy (SEM–EDX) of plants. The obtained results indicate a tolerance of the metallophytes to these PTEs, which may favour the obtaining of a naturalized habitat that acts as an effective protective barrier to the ecosystem, that is easy to maintain and that avoid the risk of transfer to the trophic chain. The use of these species can be a complement to the chemical stabilization proposed for the whole area and carried out in experimental plots. Because they are perennial plants, it is necessary to continue with the experiments and obtain results in a longer period of time that allows to evaluate yield and stabilization.