Vegetation establishment in soils polluted by heavy metal(loid)s after assisted natural remediation.

Background and aims: This field-base study evaluates the long-term effectiveness of in-situ remediation measures applied to soils residually polluted by potentially toxic elements (PTEs) in an area affected by a mining spill in SW Spain. Methods: To evaluate the remediation treatments success, their influence on key soil properties and on the development of spontaneous vegetation in the treated soils was investigated. The treatments were based on human derived by-products valorization, and consisted of: biopiles, marble sludge and gypsum mining spoil addition, and their combination with an organic amendment (vermicompost). Results: Amendments application improved the soil properties and reduced PTEs availability. As a result, an enhancement in spontaneous development of vegetation cover and diversity of plant species in the treated soils was followed. Spergularia rubra and Lamarckia aurea, two primary plant species growing in the studied area and that exhibit strong association to soils with the highest levels of pollution, showed high Pb and As accumulation in shoots ande in roots. Exceptionally, accumulation of these pollutants occurred in L. aurea roots, which can explain its high presence in soils with more limited vegetation development and in which no additional plant species can thrive. Conclusions: The occurrence of S. rubra and L. aurea in the amended soils may be indicative of improved soil conditions and reduced toxicity induced by the remediation measures implemented. They may also be considered key species in the area since their presence can promote the recolonization of the degraded soils by species less tolerant to their residual pollution. [ABSTRACT FROM AUTHOR]