Dendroremediation perspectives to improve and restore urban and periurban heavy metals-contaminated soils

Historically, different physical and chemical remediation approaches are available to control heavy metal pollution in the soils. Nevertheless, most of these methods are expensive, time-consuming, technically challenging and can trigger irreversible alterations to soil properties and microflora. Therefore, the use of trees to preserve, improve or restore the structure and the functioning of contaminated soils represents a promising eco-friendly and sustainable strategy (dendroremediation). In this context, fast-growing and high biomass-producing tree species have previously shown interesting potentialities. In the frame of the Project "DENDROCLEAN: Trees to clean up contaminated soils" (grant number CSTO160891), the response to some major heavy metal contaminants of different poplar (Populus spp.) and willow (Salix spp.) clones cultivated in hydroponic systems was tested by investigating their tolerance, phytoextraction potential and pattern of heavy metal accumulation between green and ligneous organs. Treated clones did not show substantial phytotoxic effects; the phytoextraction efficiency and the accumulation patterns displayed high variability depending on the heavy metal. Although heavy metals can be efficiently sequestered by leaves, some clones achieved good performances in the absorption at stem level. A first screening of the best scoring clones resulted in the selection of potential candidates for dendroremediation purposes. In the next future, dendroremediation might provide an effective strategy to requalify urban and periurban areas, hence boosting their role as providers of key ecosystem services.