Potential use of three different Salix genotypes for the phytostabilisation of metal contaminated soils

In the context of the ecological restauration of contaminated soils, it is crucial to acquire knowledge about the behavior of metal(oids) in different abiotic and biotic compartments and to define the mechanisms which condition their transfers, bioaccumulation and ultimately, their toxic and ecotoxicological effects at different levels of biological integration to assess further phytomanagement options. The aim of this study was to assess the capacity of three salix genotypes (Salix viminalis, Salix purpurea north-west and Salix purpurea south-east) to develop a root system and to grow under a mono-or a polymetallic constraint. The mono-metal stress (Cd, Co, Pb, Hg, Ni) was obtained by adding at the beginning of a 55 days period of growth a mono-metal solution of 0, 16, 32, 64, 128 and 256μM to a sandy substrate. The three salix genotypes demonstrated the ability to produce a root system which was mainly affected by the highest metal concentration, whereas no significant differences in terms of biomass production was observed in the upper part of plants among the different metal concentrations. At the end of the treatment, plants samples were divided into initial cutting and roots, stems and leaves entirely formed during the treatment in order to evaluate the metal repartition. We observed a significant absorption of heavy metals in the different genotypes, while the accumulation of heavy metal was contrasted in the different organs. Additionally we studied in mescosms experiments the speciation, reactivity and transfer of metal(loid)s in a soil-water-plant continuum obtained from mining soils containing up to 15000 mg Pb.kg-1, 83000 mg As.kg-1 and 1100 mg Sb.kg-1. We demonstrate the possibility to grow Salix in such conditions when mixing the contaminated mining soils to a control garden soil at different ratios in mescosms. We concluded that these Salix genotypes can be proposed to stabilize metal contaminated soils.