Ability of Nerium oleander L. Apocynaceae for the stabilization of a lead polluted soil in Mediterranean riparian ecosystems

Resumen

The ability of plant species to extract and bloaccumulate metals or to tolerate them without accumulating too much in their tissues is well known. Such species are very useful for biological soil reclamation programs (phytoextraction or phytostabilisation, respectively) in polluted areas. Recently, a screening program was started to evaluate the potential of several autochthonous plant taxa from SE Spain for reclamation of metal contaminated soils in an area with a long history of human-caused metal contamination (chiefly associated with mining practice) and which lacks a test of the suitability of biological remediation tools. In this study we tested for the capacity of Oleander (Nerium oleander; Apocynaceae) for transferring lead (Pb) from soils into above- and below-ground tissues, and evaluated transfer factors between 3 and 6 weeks of exposure. Nerium was not efficient in removing Pb from the contaminated soil, and this efficiency was even lower when there was a Mixture of metals (Pb and Zn) in soils. Results indicate that metal concentrations in the plant are not directly correlated to metal concentrations in the soil, and that the duration of exposure of plants to Pb has no significant influence on lead accumulation. Consequently, the calculated transfer factors for Pb were very low. In relation to plant physiology during the experiments, most plant tissues remained apparently very healthy after the exposure to metals. Although it may not be Suitable for lead extraction, this species may be a good candidate for phytostabilisation of lead polluted soils. Because this plant species is a very common in areas bordering river watercourses, it may prove promising for riparian soil stabilization.